1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790 4791 4792 4793 4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628 5629 5630 5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644 5645 5646 5647 5648 5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682 5683 5684 5685 5686 5687 5688 5689 5690 5691 5692 5693 5694 5695 5696 5697 5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721 5722 5723 5724 5725 5726 5727 5728 5729 5730 5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792 5793 5794 5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912 5913 5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009 6010 6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038 6039 6040 6041 6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090 6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108 6109 6110 6111 6112 6113 6114 6115 6116 6117 6118 6119 6120 6121 6122 6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 6145 6146 6147 6148 6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160 6161 6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173 6174 6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187 6188 6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200 6201 6202 6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228 6229 6230 6231 6232 6233 6234 6235 6236 6237 6238 6239 6240 6241 6242 6243 6244 6245 6246 6247 6248 6249 6250 6251 6252 6253 6254 6255 6256 6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382 6383 6384 6385 6386 6387 6388 6389 6390 6391 6392 6393 6394 6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419 6420 6421 6422 6423 6424 6425 6426 6427 6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570 6571 6572 6573 6574 6575 6576 6577 6578 6579 6580 6581 6582 6583 6584 6585 6586 6587 6588 6589 6590 6591 6592 6593 6594 6595 6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620 6621 6622 6623 6624 6625 6626 6627 6628 6629 6630 6631 6632 6633 6634 6635 6636 6637 6638 6639 6640 6641 6642 6643 6644 6645 6646 6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657 6658 6659 6660 6661 6662 6663 6664 6665 6666 6667 6668 6669 6670 6671 6672 6673 6674 6675 6676 6677 6678 6679 6680 6681 6682 6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743 6744 6745 6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764 6765 6766 6767 6768 6769 6770 6771 6772 6773 6774 6775 6776 6777 6778 6779 6780 6781 6782 6783 6784 6785 6786 6787 6788 6789 6790 6791 6792 6793 6794 6795 6796 6797 6798 6799 6800 6801 6802 6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832 6833 6834 6835 6836 6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849 6850 6851 6852 6853 6854 6855 6856 6857 6858 6859 6860 6861 6862 6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879 6880 6881 6882 6883 6884 6885 6886 6887 6888 6889 6890 6891 6892 6893 6894 6895 6896 6897 6898 6899 6900 6901 6902 6903 6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926 6927 6928 6929 6930 6931 6932 6933 6934 6935 6936 6937 6938 6939 6940 6941 6942 6943 6944 6945 6946 6947 6948 6949 6950 6951 6952 6953 6954 6955 6956 6957 6958 6959 6960 6961 6962 6963 6964 6965 6966 6967 6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986 6987 6988 6989 6990 6991 6992 6993 6994 6995 6996 6997 6998 6999 7000 7001 7002 7003 7004 7005 7006 7007 7008 7009 7010 7011 7012 7013 7014 7015 7016 7017 7018 7019 7020 7021 7022 7023 7024 7025 7026 7027 7028 7029 7030 7031 7032 7033 7034 7035 7036 7037 7038 7039 7040 7041 7042 7043 7044 7045 7046 7047 7048 7049 7050 7051 7052 7053 7054 7055 7056 7057 7058 7059 7060 7061 7062 7063 7064 7065 7066 7067 7068 7069 7070 7071 7072 7073 7074 7075 7076 7077 7078 7079 7080 7081 7082 7083 7084 7085 7086 7087 7088 7089 7090 7091 7092 7093 7094 7095 7096 7097 7098 7099 7100 7101 7102 7103 7104 7105 7106 7107 7108 7109 7110 7111 7112 7113 7114 7115 7116 7117 7118 7119 7120 7121 7122 7123 7124 7125 7126 7127 7128 7129 7130 7131 7132 7133 7134 7135 7136 7137 7138 7139 7140 7141 7142 7143 7144 7145 7146 7147 7148 7149 7150 7151 7152 7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164 7165 7166 7167 7168 7169 7170 7171 7172 7173 7174 7175 7176 7177 7178 7179 7180 7181 7182 7183 7184 7185 7186 7187 7188 7189 7190 7191 7192 7193 7194 7195 7196 7197 7198 7199 7200 7201 7202 7203 7204 7205 7206 7207 7208 7209 7210 7211 7212 7213 7214 7215 7216 7217 7218 7219 7220 7221 7222 7223 7224 7225 7226 7227 7228 7229 7230 7231 7232 7233 7234 7235 7236 7237 7238 7239 7240 7241 7242 7243 7244 7245 7246 7247 7248 7249 7250 7251 7252 7253 7254 7255 7256 7257 7258 7259 7260 7261 7262 7263 7264 7265 7266 7267 7268 7269 7270 7271 7272 7273 7274 7275 7276 7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287 7288 7289 7290 7291 7292 7293 7294 7295 7296 7297 7298 7299 7300 7301 7302 7303 7304 7305 7306 7307 7308 7309 7310 7311 7312 7313 7314 7315 7316 7317 7318 7319 7320 7321 7322 7323 7324 7325 7326 7327 7328 7329 7330 7331 7332 7333 7334 7335 7336 7337 7338 7339 7340 7341 7342 7343 7344 7345 7346 7347 7348 7349 7350 7351 7352 7353 7354 7355 7356 7357 7358 7359 7360 7361 7362 7363 7364 7365 7366 7367 7368 7369 7370 7371 7372 7373 7374 7375 7376 7377 7378 7379 7380 7381 7382 7383 7384 7385 7386 7387 7388 7389 7390 7391 7392 7393 7394 7395 7396 7397 7398 7399 7400 7401 7402 7403 7404 7405 7406 7407 7408 7409 7410 7411 7412 7413 7414 7415 7416 7417 7418 7419 7420 7421 7422 7423 7424 7425 7426 7427 7428 7429 7430 7431 7432 7433 7434 7435 7436 7437 7438 7439 7440 7441 7442 7443 7444 7445 7446 7447 7448 7449 7450 7451 7452 7453 7454 7455 7456 7457 7458 7459 7460 7461 7462 7463 7464 7465 7466 7467 7468 7469 7470 7471 7472 7473 7474 7475 7476 7477 7478 7479 7480 7481 7482 7483 7484 7485 7486 7487 7488 7489 7490 7491 7492 7493 7494 7495 7496 7497 7498 7499 7500 7501 7502 7503 7504 7505 7506 7507 7508 7509 7510 7511 7512 7513 7514 7515 7516 7517 7518 7519 7520 7521 7522 7523 7524 7525 7526 7527 7528 7529 7530 7531 7532 7533 7534 7535 7536 7537 7538 7539 7540 7541 7542 7543 7544 7545 7546 7547 7548 7549 7550 7551 7552 7553 7554 7555 7556 7557 7558 7559 7560 7561 7562 7563 7564 7565 7566 7567 7568 7569 7570 7571 7572 7573 7574 7575 7576 7577 7578 7579 7580 7581 7582 7583 7584 7585 7586 7587 7588 7589 7590 7591 7592 7593 7594 7595 7596 7597 7598 7599 7600 7601 7602 7603 7604 7605 7606 7607 7608 7609 7610 7611 7612 7613 7614 7615 7616 7617 7618 7619 7620 7621 7622 7623 7624 7625 7626 7627 7628 7629 7630 7631 7632 7633 7634 7635 7636 7637 7638 7639 7640 7641 7642 7643 7644 7645 7646 7647 7648 7649 7650 7651 7652 7653 7654 7655 7656 7657 7658 7659 7660 7661 7662 7663 7664 7665 7666 7667 7668 7669 7670 7671 7672 7673 7674 7675 7676 7677 7678 7679 7680 7681 7682 7683 7684 7685 7686 7687 7688 7689 7690 7691 7692 7693 7694 7695 7696 7697 7698 7699 7700 7701 7702 7703 7704 7705 7706 7707 7708 7709 7710 7711 7712 7713 7714 7715 7716 7717 7718 7719 7720 7721 7722 7723 7724 7725 7726 7727 7728 7729 7730 7731 7732 7733 7734 7735 7736 7737 7738 7739 7740 7741 7742 7743 7744 7745 7746 7747 7748 7749 7750 7751 7752 7753 7754 7755 7756 7757 7758 7759 7760 7761 7762 7763 7764 7765 7766 7767 7768 7769 7770 7771 7772 7773 7774 7775 7776 7777 7778 7779 7780 7781 7782 7783 7784 7785 7786 7787 7788 7789 7790 7791 7792 7793 7794 7795 7796 7797 7798 7799 7800 7801 7802 7803 7804 7805 7806 7807 7808 7809 7810 7811 7812 7813 7814 7815 7816 7817 7818 7819 7820 7821 7822 7823 7824 7825 7826 7827 7828 7829 7830 7831 7832 7833 7834 7835 7836 7837 7838 7839 7840 7841 7842 7843 7844 7845 7846 7847 7848 7849 7850 7851 7852 7853 7854 7855 7856 7857 7858 7859 7860 7861 7862 7863 7864 7865 7866 7867 7868 7869 7870 7871 7872 7873 7874 7875 7876 7877 7878 7879 7880 7881 7882 7883 7884 7885 7886 7887 7888 7889 7890 7891 7892 7893 7894 7895 7896 7897 7898 7899 7900 7901 7902 7903 7904 7905 7906 7907 7908 7909 7910 7911 7912 7913 7914 7915 7916 7917 7918 7919 7920 7921 7922 7923 7924 7925 7926 7927 7928 7929 7930 7931 7932 7933 7934 7935 7936 7937 7938 7939 7940 7941 7942 7943 7944 7945 7946 7947 7948 7949 7950 7951 7952 7953 7954 7955 7956 7957 7958 7959 7960 7961 7962 7963 7964 7965 7966 7967 7968 7969 7970 7971 7972 7973 7974 7975 7976 7977 7978 7979 7980 7981 7982 7983 7984 7985 7986 7987 7988 7989 7990 7991 7992 7993 7994 7995 7996 7997 7998 7999 8000 8001 8002 8003 8004 8005 8006 8007 8008 8009 8010 8011 8012 8013 8014 8015 8016 8017 8018 8019 8020 8021 8022 8023 8024 8025 8026 8027 8028 8029 8030 8031 8032 8033 8034 8035 8036 8037 8038 8039 8040 8041 8042 8043 8044 8045 8046 8047 8048 8049 8050 8051 8052 8053 8054 8055 8056 8057 8058 8059 8060 8061 8062 8063 8064 8065 8066 8067 8068 8069 8070 8071 8072 8073 8074 8075 8076 8077 8078 8079 8080 8081 8082 8083 8084 8085 8086 8087 8088 8089 8090 8091 8092 8093 8094 8095 8096 8097 8098 8099 8100 8101 8102 8103 8104 8105 8106 8107 8108 8109 8110 8111 8112 8113 8114 8115 8116 8117 8118 8119 8120 8121 8122 8123 8124 8125 8126 8127 8128 8129 8130 8131 8132 8133 8134 8135 8136 8137 8138 8139 8140 8141 8142 8143 8144 8145 8146 8147 8148 8149 8150 8151 8152 8153 8154 8155 8156 8157 8158 8159 8160 8161 8162 8163 8164 8165 8166 8167 8168 8169 8170 8171 8172 8173 8174 8175 8176 8177 8178 8179 8180 8181 8182 8183 8184 8185 8186 8187 8188 8189 8190 8191 8192 8193 8194 8195 8196 8197 8198 8199 8200 8201 8202 8203 8204 8205 8206 8207 8208 8209 8210 8211 8212 8213 8214 8215 8216 8217 8218 8219 8220 8221 8222 8223 8224 8225 8226 8227 8228 8229 8230 8231 8232 8233 8234 8235 8236 8237 8238 8239 8240 8241 8242 8243 8244 8245 8246 8247 8248 8249 8250 8251 8252 8253 8254 8255 8256 8257 8258 8259 8260 8261 8262 8263 8264 8265 8266 8267 8268 8269 8270 8271 8272 8273 8274 8275 8276 8277 8278 8279 8280 8281 8282 8283 8284
// Copyright 2018 The Fuchsia Authors
//
// Licensed under the 2-Clause BSD License <LICENSE-BSD or
// https://opensource.org/license/bsd-2-clause>, Apache License, Version 2.0
// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
// This file may not be copied, modified, or distributed except according to
// those terms.
// After updating the following doc comment, make sure to run the following
// command to update `README.md` based on its contents:
//
// ./generate-readme.sh > README.md
//! *<span style="font-size: 100%; color:grey;">Want to help improve zerocopy?
//! Fill out our [user survey][user-survey]!</span>*
//!
//! ***<span style="font-size: 140%">Fast, safe, <span
//! style="color:red;">compile error</span>. Pick two.</span>***
//!
//! Zerocopy makes zero-cost memory manipulation effortless. We write `unsafe`
//! so you don't have to.
//!
//! # Overview
//!
//! Zerocopy provides four core marker traits, each of which can be derived
//! (e.g., `#[derive(FromZeroes)]`):
//! - [`FromZeroes`] indicates that a sequence of zero bytes represents a valid
//! instance of a type
//! - [`FromBytes`] indicates that a type may safely be converted from an
//! arbitrary byte sequence
//! - [`AsBytes`] indicates that a type may safely be converted *to* a byte
//! sequence
//! - [`Unaligned`] indicates that a type's alignment requirement is 1
//!
//! Types which implement a subset of these traits can then be converted to/from
//! byte sequences with little to no runtime overhead.
//!
//! Zerocopy also provides byte-order aware integer types that support these
//! conversions; see the [`byteorder`] module. These types are especially useful
//! for network parsing.
//!
//! [user-survey]: https://docs.google.com/forms/d/e/1FAIpQLSdzBNTN9tzwsmtyZxRFNL02K36IWCdHWW2ZBckyQS2xiO3i8Q/viewform?usp=published_options
//!
//! # Cargo Features
//!
//! - **`alloc`**
//! By default, `zerocopy` is `no_std`. When the `alloc` feature is enabled,
//! the `alloc` crate is added as a dependency, and some allocation-related
//! functionality is added.
//!
//! - **`byteorder`** (enabled by default)
//! Adds the [`byteorder`] module and a dependency on the `byteorder` crate.
//! The `byteorder` module provides byte order-aware equivalents of the
//! multi-byte primitive numerical types. Unlike their primitive equivalents,
//! the types in this module have no alignment requirement and support byte
//! order conversions. This can be useful in handling file formats, network
//! packet layouts, etc which don't provide alignment guarantees and which may
//! use a byte order different from that of the execution platform.
//!
//! - **`derive`**
//! Provides derives for the core marker traits via the `zerocopy-derive`
//! crate. These derives are re-exported from `zerocopy`, so it is not
//! necessary to depend on `zerocopy-derive` directly.
//!
//! However, you may experience better compile times if you instead directly
//! depend on both `zerocopy` and `zerocopy-derive` in your `Cargo.toml`,
//! since doing so will allow Rust to compile these crates in parallel. To do
//! so, do *not* enable the `derive` feature, and list both dependencies in
//! your `Cargo.toml` with the same leading non-zero version number; e.g:
//!
//! ```toml
//! [dependencies]
//! zerocopy = "0.X"
//! zerocopy-derive = "0.X"
//! ```
//!
//! - **`simd`**
//! When the `simd` feature is enabled, `FromZeroes`, `FromBytes`, and
//! `AsBytes` impls are emitted for all stable SIMD types which exist on the
//! target platform. Note that the layout of SIMD types is not yet stabilized,
//! so these impls may be removed in the future if layout changes make them
//! invalid. For more information, see the Unsafe Code Guidelines Reference
//! page on the [layout of packed SIMD vectors][simd-layout].
//!
//! - **`simd-nightly`**
//! Enables the `simd` feature and adds support for SIMD types which are only
//! available on nightly. Since these types are unstable, support for any type
//! may be removed at any point in the future.
//!
//! [simd-layout]: https://rust-lang.github.io/unsafe-code-guidelines/layout/packed-simd-vectors.html
//!
//! # Security Ethos
//!
//! Zerocopy is expressly designed for use in security-critical contexts. We
//! strive to ensure that that zerocopy code is sound under Rust's current
//! memory model, and *any future memory model*. We ensure this by:
//! - **...not 'guessing' about Rust's semantics.**
//! We annotate `unsafe` code with a precise rationale for its soundness that
//! cites a relevant section of Rust's official documentation. When Rust's
//! documented semantics are unclear, we work with the Rust Operational
//! Semantics Team to clarify Rust's documentation.
//! - **...rigorously testing our implementation.**
//! We run tests using [Miri], ensuring that zerocopy is sound across a wide
//! array of supported target platforms of varying endianness and pointer
//! width, and across both current and experimental memory models of Rust.
//! - **...formally proving the correctness of our implementation.**
//! We apply formal verification tools like [Kani][kani] to prove zerocopy's
//! correctness.
//!
//! For more information, see our full [soundness policy].
//!
//! [Miri]: https://github.com/rust-lang/miri
//! [Kani]: https://github.com/model-checking/kani
//! [soundness policy]: https://github.com/google/zerocopy/blob/main/POLICIES.md#soundness
//!
//! # Relationship to Project Safe Transmute
//!
//! [Project Safe Transmute] is an official initiative of the Rust Project to
//! develop language-level support for safer transmutation. The Project consults
//! with crates like zerocopy to identify aspects of safer transmutation that
//! would benefit from compiler support, and has developed an [experimental,
//! compiler-supported analysis][mcp-transmutability] which determines whether,
//! for a given type, any value of that type may be soundly transmuted into
//! another type. Once this functionality is sufficiently mature, zerocopy
//! intends to replace its internal transmutability analysis (implemented by our
//! custom derives) with the compiler-supported one. This change will likely be
//! an implementation detail that is invisible to zerocopy's users.
//!
//! Project Safe Transmute will not replace the need for most of zerocopy's
//! higher-level abstractions. The experimental compiler analysis is a tool for
//! checking the soundness of `unsafe` code, not a tool to avoid writing
//! `unsafe` code altogether. For the foreseeable future, crates like zerocopy
//! will still be required in order to provide higher-level abstractions on top
//! of the building block provided by Project Safe Transmute.
//!
//! [Project Safe Transmute]: https://rust-lang.github.io/rfcs/2835-project-safe-transmute.html
//! [mcp-transmutability]: https://github.com/rust-lang/compiler-team/issues/411
//!
//! # MSRV
//!
//! See our [MSRV policy].
//!
//! [MSRV policy]: https://github.com/google/zerocopy/blob/main/POLICIES.md#msrv
//!
//! # Changelog
//!
//! Zerocopy uses [GitHub Releases].
//!
//! [GitHub Releases]: https://github.com/google/zerocopy/releases
// Sometimes we want to use lints which were added after our MSRV.
// `unknown_lints` is `warn` by default and we deny warnings in CI, so without
// this attribute, any unknown lint would cause a CI failure when testing with
// our MSRV.
//
// TODO(#1201): Remove `unexpected_cfgs`
#![allow(unknown_lints, non_local_definitions, unexpected_cfgs)]
#![deny(renamed_and_removed_lints)]
#![deny(
anonymous_parameters,
deprecated_in_future,
late_bound_lifetime_arguments,
missing_copy_implementations,
missing_debug_implementations,
missing_docs,
path_statements,
patterns_in_fns_without_body,
rust_2018_idioms,
trivial_numeric_casts,
unreachable_pub,
unsafe_op_in_unsafe_fn,
unused_extern_crates,
// We intentionally choose not to deny `unused_qualifications`. When items
// are added to the prelude (e.g., `core::mem::size_of`), this has the
// consequence of making some uses trigger this lint on the latest toolchain
// (e.g., `mem::size_of`), but fixing it (e.g. by replacing with `size_of`)
// does not work on older toolchains.
//
// We tested a more complicated fix in #1413, but ultimately decided that,
// since this lint is just a minor style lint, the complexity isn't worth it
// - it's fine to occasionally have unused qualifications slip through,
// especially since these do not affect our user-facing API in any way.
variant_size_differences
)]
#![cfg_attr(
__INTERNAL_USE_ONLY_NIGHLTY_FEATURES_IN_TESTS,
deny(fuzzy_provenance_casts, lossy_provenance_casts)
)]
#![deny(
clippy::all,
clippy::alloc_instead_of_core,
clippy::arithmetic_side_effects,
clippy::as_underscore,
clippy::assertions_on_result_states,
clippy::as_conversions,
clippy::correctness,
clippy::dbg_macro,
clippy::decimal_literal_representation,
clippy::get_unwrap,
clippy::indexing_slicing,
clippy::missing_inline_in_public_items,
clippy::missing_safety_doc,
clippy::obfuscated_if_else,
clippy::perf,
clippy::print_stdout,
clippy::std_instead_of_core,
clippy::style,
clippy::suspicious,
clippy::todo,
clippy::undocumented_unsafe_blocks,
clippy::unimplemented,
clippy::unnested_or_patterns,
clippy::unwrap_used,
clippy::use_debug
)]
#![deny(
rustdoc::bare_urls,
rustdoc::broken_intra_doc_links,
rustdoc::invalid_codeblock_attributes,
rustdoc::invalid_html_tags,
rustdoc::invalid_rust_codeblocks,
rustdoc::missing_crate_level_docs,
rustdoc::private_intra_doc_links
)]
// In test code, it makes sense to weight more heavily towards concise, readable
// code over correct or debuggable code.
#![cfg_attr(any(test, kani), allow(
// In tests, you get line numbers and have access to source code, so panic
// messages are less important. You also often unwrap a lot, which would
// make expect'ing instead very verbose.
clippy::unwrap_used,
// In tests, there's no harm to "panic risks" - the worst that can happen is
// that your test will fail, and you'll fix it. By contrast, panic risks in
// production code introduce the possibly of code panicking unexpectedly "in
// the field".
clippy::arithmetic_side_effects,
clippy::indexing_slicing,
))]
#![cfg_attr(not(test), no_std)]
#![cfg_attr(
all(feature = "simd-nightly", any(target_arch = "x86", target_arch = "x86_64")),
feature(stdarch_x86_avx512)
)]
#![cfg_attr(
all(feature = "simd-nightly", target_arch = "arm"),
feature(stdarch_arm_dsp, stdarch_arm_neon_intrinsics)
)]
#![cfg_attr(
all(feature = "simd-nightly", any(target_arch = "powerpc", target_arch = "powerpc64")),
feature(stdarch_powerpc)
)]
#![cfg_attr(doc_cfg, feature(doc_cfg))]
#![cfg_attr(
__INTERNAL_USE_ONLY_NIGHLTY_FEATURES_IN_TESTS,
feature(layout_for_ptr, strict_provenance)
)]
// This is a hack to allow zerocopy-derive derives to work in this crate. They
// assume that zerocopy is linked as an extern crate, so they access items from
// it as `zerocopy::Xxx`. This makes that still work.
#[cfg(any(feature = "derive", test))]
extern crate self as zerocopy;
#[macro_use]
mod macros;
#[cfg(feature = "byteorder")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "byteorder")))]
pub mod byteorder;
#[doc(hidden)]
pub mod macro_util;
mod post_monomorphization_compile_fail_tests;
mod util;
// TODO(#252): If we make this pub, come up with a better name.
mod wrappers;
#[cfg(feature = "byteorder")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "byteorder")))]
pub use crate::byteorder::*;
pub use crate::wrappers::*;
#[cfg(any(feature = "derive", test))]
#[cfg_attr(doc_cfg, doc(cfg(feature = "derive")))]
pub use zerocopy_derive::Unaligned;
// `pub use` separately here so that we can mark it `#[doc(hidden)]`.
//
// TODO(#29): Remove this or add a doc comment.
#[cfg(any(feature = "derive", test))]
#[cfg_attr(doc_cfg, doc(cfg(feature = "derive")))]
#[doc(hidden)]
pub use zerocopy_derive::KnownLayout;
use core::{
cell::{self, RefMut},
cmp::Ordering,
fmt::{self, Debug, Display, Formatter},
hash::Hasher,
marker::PhantomData,
mem::{self, ManuallyDrop, MaybeUninit},
num::{
NonZeroI128, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI8, NonZeroIsize, NonZeroU128,
NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize, Wrapping,
},
ops::{Deref, DerefMut},
ptr::{self, NonNull},
slice,
};
#[cfg(feature = "alloc")]
extern crate alloc;
#[cfg(feature = "alloc")]
use alloc::{boxed::Box, vec::Vec};
#[cfg(any(feature = "alloc", kani))]
use core::alloc::Layout;
// Used by `TryFromBytes::is_bit_valid`.
#[doc(hidden)]
pub use crate::util::ptr::Ptr;
// For each polyfill, as soon as the corresponding feature is stable, the
// polyfill import will be unused because method/function resolution will prefer
// the inherent method/function over a trait method/function. Thus, we suppress
// the `unused_imports` warning.
//
// See the documentation on `util::polyfills` for more information.
#[allow(unused_imports)]
use crate::util::polyfills::NonNullExt as _;
#[rustversion::nightly]
#[cfg(all(test, not(__INTERNAL_USE_ONLY_NIGHLTY_FEATURES_IN_TESTS)))]
const _: () = {
#[deprecated = "some tests may be skipped due to missing RUSTFLAGS=\"--cfg __INTERNAL_USE_ONLY_NIGHLTY_FEATURES_IN_TESTS\""]
const _WARNING: () = ();
#[warn(deprecated)]
_WARNING
};
/// The target pointer width, counted in bits.
const POINTER_WIDTH_BITS: usize = mem::size_of::<usize>() * 8;
/// The layout of a type which might be dynamically-sized.
///
/// `DstLayout` describes the layout of sized types, slice types, and "slice
/// DSTs" - ie, those that are known by the type system to have a trailing slice
/// (as distinguished from `dyn Trait` types - such types *might* have a
/// trailing slice type, but the type system isn't aware of it).
///
/// # Safety
///
/// Unlike [`core::alloc::Layout`], `DstLayout` is only used to describe full
/// Rust types - ie, those that satisfy the layout requirements outlined by
/// [the reference]. Callers may assume that an instance of `DstLayout`
/// satisfies any conditions imposed on Rust types by the reference.
///
/// If `layout: DstLayout` describes a type, `T`, then it is guaranteed that:
/// - `layout.align` is equal to `T`'s alignment
/// - If `layout.size_info` is `SizeInfo::Sized { size }`, then `T: Sized` and
/// `size_of::<T>() == size`
/// - If `layout.size_info` is `SizeInfo::SliceDst(slice_layout)`, then
/// - `T` is a slice DST
/// - The `size` of an instance of `T` with `elems` trailing slice elements is
/// equal to `slice_layout.offset + slice_layout.elem_size * elems` rounded up
/// to the nearest multiple of `layout.align`. Any bytes in the range
/// `[slice_layout.offset + slice_layout.elem_size * elems, size)` are padding
/// and must not be assumed to be initialized.
///
/// [the reference]: https://doc.rust-lang.org/reference/type-layout.html
#[doc(hidden)]
#[allow(missing_debug_implementations, missing_copy_implementations)]
#[cfg_attr(any(kani, test), derive(Copy, Clone, Debug, PartialEq, Eq))]
pub struct DstLayout {
align: NonZeroUsize,
size_info: SizeInfo,
}
#[cfg_attr(any(kani, test), derive(Copy, Clone, Debug, PartialEq, Eq))]
enum SizeInfo<E = usize> {
Sized { _size: usize },
SliceDst(TrailingSliceLayout<E>),
}
#[cfg_attr(any(kani, test), derive(Copy, Clone, Debug, PartialEq, Eq))]
struct TrailingSliceLayout<E = usize> {
// The offset of the first byte of the trailing slice field. Note that this
// is NOT the same as the minimum size of the type. For example, consider
// the following type:
//
// struct Foo {
// a: u16,
// b: u8,
// c: [u8],
// }
//
// In `Foo`, `c` is at byte offset 3. When `c.len() == 0`, `c` is followed
// by a padding byte.
_offset: usize,
// The size of the element type of the trailing slice field.
_elem_size: E,
}
impl SizeInfo {
/// Attempts to create a `SizeInfo` from `Self` in which `elem_size` is a
/// `NonZeroUsize`. If `elem_size` is 0, returns `None`.
#[allow(unused)]
const fn try_to_nonzero_elem_size(&self) -> Option<SizeInfo<NonZeroUsize>> {
Some(match *self {
SizeInfo::Sized { _size } => SizeInfo::Sized { _size },
SizeInfo::SliceDst(TrailingSliceLayout { _offset, _elem_size }) => {
if let Some(_elem_size) = NonZeroUsize::new(_elem_size) {
SizeInfo::SliceDst(TrailingSliceLayout { _offset, _elem_size })
} else {
return None;
}
}
})
}
}
#[doc(hidden)]
#[derive(Copy, Clone)]
#[cfg_attr(test, derive(Debug))]
#[allow(missing_debug_implementations)]
pub enum _CastType {
_Prefix,
_Suffix,
}
impl DstLayout {
/// The minimum possible alignment of a type.
const MIN_ALIGN: NonZeroUsize = match NonZeroUsize::new(1) {
Some(min_align) => min_align,
None => unreachable!(),
};
/// The maximum theoretic possible alignment of a type.
///
/// For compatibility with future Rust versions, this is defined as the
/// maximum power-of-two that fits into a `usize`. See also
/// [`DstLayout::CURRENT_MAX_ALIGN`].
const THEORETICAL_MAX_ALIGN: NonZeroUsize =
match NonZeroUsize::new(1 << (POINTER_WIDTH_BITS - 1)) {
Some(max_align) => max_align,
None => unreachable!(),
};
/// The current, documented max alignment of a type \[1\].
///
/// \[1\] Per <https://doc.rust-lang.org/reference/type-layout.html#the-alignment-modifiers>:
///
/// The alignment value must be a power of two from 1 up to
/// 2<sup>29</sup>.
#[cfg(not(kani))]
const CURRENT_MAX_ALIGN: NonZeroUsize = match NonZeroUsize::new(1 << 28) {
Some(max_align) => max_align,
None => unreachable!(),
};
/// Constructs a `DstLayout` for a zero-sized type with `repr_align`
/// alignment (or 1). If `repr_align` is provided, then it must be a power
/// of two.
///
/// # Panics
///
/// This function panics if the supplied `repr_align` is not a power of two.
///
/// # Safety
///
/// Unsafe code may assume that the contract of this function is satisfied.
#[doc(hidden)]
#[inline]
pub const fn new_zst(repr_align: Option<NonZeroUsize>) -> DstLayout {
let align = match repr_align {
Some(align) => align,
None => Self::MIN_ALIGN,
};
assert!(align.is_power_of_two());
DstLayout { align, size_info: SizeInfo::Sized { _size: 0 } }
}
/// Constructs a `DstLayout` which describes `T`.
///
/// # Safety
///
/// Unsafe code may assume that `DstLayout` is the correct layout for `T`.
#[doc(hidden)]
#[inline]
pub const fn for_type<T>() -> DstLayout {
// SAFETY: `align` is correct by construction. `T: Sized`, and so it is
// sound to initialize `size_info` to `SizeInfo::Sized { size }`; the
// `size` field is also correct by construction.
DstLayout {
align: match NonZeroUsize::new(mem::align_of::<T>()) {
Some(align) => align,
None => unreachable!(),
},
size_info: SizeInfo::Sized { _size: mem::size_of::<T>() },
}
}
/// Constructs a `DstLayout` which describes `[T]`.
///
/// # Safety
///
/// Unsafe code may assume that `DstLayout` is the correct layout for `[T]`.
const fn for_slice<T>() -> DstLayout {
// SAFETY: The alignment of a slice is equal to the alignment of its
// element type, and so `align` is initialized correctly.
//
// Since this is just a slice type, there is no offset between the
// beginning of the type and the beginning of the slice, so it is
// correct to set `offset: 0`. The `elem_size` is correct by
// construction. Since `[T]` is a (degenerate case of a) slice DST, it
// is correct to initialize `size_info` to `SizeInfo::SliceDst`.
DstLayout {
align: match NonZeroUsize::new(mem::align_of::<T>()) {
Some(align) => align,
None => unreachable!(),
},
size_info: SizeInfo::SliceDst(TrailingSliceLayout {
_offset: 0,
_elem_size: mem::size_of::<T>(),
}),
}
}
/// Like `Layout::extend`, this creates a layout that describes a record
/// whose layout consists of `self` followed by `next` that includes the
/// necessary inter-field padding, but not any trailing padding.
///
/// In order to match the layout of a `#[repr(C)]` struct, this method
/// should be invoked for each field in declaration order. To add trailing
/// padding, call `DstLayout::pad_to_align` after extending the layout for
/// all fields. If `self` corresponds to a type marked with
/// `repr(packed(N))`, then `repr_packed` should be set to `Some(N)`,
/// otherwise `None`.
///
/// This method cannot be used to match the layout of a record with the
/// default representation, as that representation is mostly unspecified.
///
/// # Safety
///
/// If a (potentially hypothetical) valid `repr(C)` Rust type begins with
/// fields whose layout are `self`, and those fields are immediately
/// followed by a field whose layout is `field`, then unsafe code may rely
/// on `self.extend(field, repr_packed)` producing a layout that correctly
/// encompasses those two components.
///
/// We make no guarantees to the behavior of this method if these fragments
/// cannot appear in a valid Rust type (e.g., the concatenation of the
/// layouts would lead to a size larger than `isize::MAX`).
#[doc(hidden)]
#[inline]
pub const fn extend(self, field: DstLayout, repr_packed: Option<NonZeroUsize>) -> Self {
use util::{core_layout::padding_needed_for, max, min};
// If `repr_packed` is `None`, there are no alignment constraints, and
// the value can be defaulted to `THEORETICAL_MAX_ALIGN`.
let max_align = match repr_packed {
Some(max_align) => max_align,
None => Self::THEORETICAL_MAX_ALIGN,
};
assert!(max_align.is_power_of_two());
// We use Kani to prove that this method is robust to future increases
// in Rust's maximum allowed alignment. However, if such a change ever
// actually occurs, we'd like to be notified via assertion failures.
#[cfg(not(kani))]
{
debug_assert!(self.align.get() <= DstLayout::CURRENT_MAX_ALIGN.get());
debug_assert!(field.align.get() <= DstLayout::CURRENT_MAX_ALIGN.get());
if let Some(repr_packed) = repr_packed {
debug_assert!(repr_packed.get() <= DstLayout::CURRENT_MAX_ALIGN.get());
}
}
// The field's alignment is clamped by `repr_packed` (i.e., the
// `repr(packed(N))` attribute, if any) [1].
//
// [1] Per https://doc.rust-lang.org/reference/type-layout.html#the-alignment-modifiers:
//
// The alignments of each field, for the purpose of positioning
// fields, is the smaller of the specified alignment and the alignment
// of the field's type.
let field_align = min(field.align, max_align);
// The struct's alignment is the maximum of its previous alignment and
// `field_align`.
let align = max(self.align, field_align);
let size_info = match self.size_info {
// If the layout is already a DST, we panic; DSTs cannot be extended
// with additional fields.
SizeInfo::SliceDst(..) => panic!("Cannot extend a DST with additional fields."),
SizeInfo::Sized { _size: preceding_size } => {
// Compute the minimum amount of inter-field padding needed to
// satisfy the field's alignment, and offset of the trailing
// field. [1]
//
// [1] Per https://doc.rust-lang.org/reference/type-layout.html#the-alignment-modifiers:
//
// Inter-field padding is guaranteed to be the minimum
// required in order to satisfy each field's (possibly
// altered) alignment.
let padding = padding_needed_for(preceding_size, field_align);
// This will not panic (and is proven to not panic, with Kani)
// if the layout components can correspond to a leading layout
// fragment of a valid Rust type, but may panic otherwise (e.g.,
// combining or aligning the components would create a size
// exceeding `isize::MAX`).
let offset = match preceding_size.checked_add(padding) {
Some(offset) => offset,
None => panic!("Adding padding to `self`'s size overflows `usize`."),
};
match field.size_info {
SizeInfo::Sized { _size: field_size } => {
// If the trailing field is sized, the resulting layout
// will be sized. Its size will be the sum of the
// preceeding layout, the size of the new field, and the
// size of inter-field padding between the two.
//
// This will not panic (and is proven with Kani to not
// panic) if the layout components can correspond to a
// leading layout fragment of a valid Rust type, but may
// panic otherwise (e.g., combining or aligning the
// components would create a size exceeding
// `usize::MAX`).
let size = match offset.checked_add(field_size) {
Some(size) => size,
None => panic!("`field` cannot be appended without the total size overflowing `usize`"),
};
SizeInfo::Sized { _size: size }
}
SizeInfo::SliceDst(TrailingSliceLayout {
_offset: trailing_offset,
_elem_size,
}) => {
// If the trailing field is dynamically sized, so too
// will the resulting layout. The offset of the trailing
// slice component is the sum of the offset of the
// trailing field and the trailing slice offset within
// that field.
//
// This will not panic (and is proven with Kani to not
// panic) if the layout components can correspond to a
// leading layout fragment of a valid Rust type, but may
// panic otherwise (e.g., combining or aligning the
// components would create a size exceeding
// `usize::MAX`).
let offset = match offset.checked_add(trailing_offset) {
Some(offset) => offset,
None => panic!("`field` cannot be appended without the total size overflowing `usize`"),
};
SizeInfo::SliceDst(TrailingSliceLayout { _offset: offset, _elem_size })
}
}
}
};
DstLayout { align, size_info }
}
/// Like `Layout::pad_to_align`, this routine rounds the size of this layout
/// up to the nearest multiple of this type's alignment or `repr_packed`
/// (whichever is less). This method leaves DST layouts unchanged, since the
/// trailing padding of DSTs is computed at runtime.
///
/// In order to match the layout of a `#[repr(C)]` struct, this method
/// should be invoked after the invocations of [`DstLayout::extend`]. If
/// `self` corresponds to a type marked with `repr(packed(N))`, then
/// `repr_packed` should be set to `Some(N)`, otherwise `None`.
///
/// This method cannot be used to match the layout of a record with the
/// default representation, as that representation is mostly unspecified.
///
/// # Safety
///
/// If a (potentially hypothetical) valid `repr(C)` type begins with fields
/// whose layout are `self` followed only by zero or more bytes of trailing
/// padding (not included in `self`), then unsafe code may rely on
/// `self.pad_to_align(repr_packed)` producing a layout that correctly
/// encapsulates the layout of that type.
///
/// We make no guarantees to the behavior of this method if `self` cannot
/// appear in a valid Rust type (e.g., because the addition of trailing
/// padding would lead to a size larger than `isize::MAX`).
#[doc(hidden)]
#[inline]
pub const fn pad_to_align(self) -> Self {
use util::core_layout::padding_needed_for;
let size_info = match self.size_info {
// For sized layouts, we add the minimum amount of trailing padding
// needed to satisfy alignment.
SizeInfo::Sized { _size: unpadded_size } => {
let padding = padding_needed_for(unpadded_size, self.align);
let size = match unpadded_size.checked_add(padding) {
Some(size) => size,
None => panic!("Adding padding caused size to overflow `usize`."),
};
SizeInfo::Sized { _size: size }
}
// For DST layouts, trailing padding depends on the length of the
// trailing DST and is computed at runtime. This does not alter the
// offset or element size of the layout, so we leave `size_info`
// unchanged.
size_info @ SizeInfo::SliceDst(_) => size_info,
};
DstLayout { align: self.align, size_info }
}
/// Validates that a cast is sound from a layout perspective.
///
/// Validates that the size and alignment requirements of a type with the
/// layout described in `self` would not be violated by performing a
/// `cast_type` cast from a pointer with address `addr` which refers to a
/// memory region of size `bytes_len`.
///
/// If the cast is valid, `validate_cast_and_convert_metadata` returns
/// `(elems, split_at)`. If `self` describes a dynamically-sized type, then
/// `elems` is the maximum number of trailing slice elements for which a
/// cast would be valid (for sized types, `elem` is meaningless and should
/// be ignored). `split_at` is the index at which to split the memory region
/// in order for the prefix (suffix) to contain the result of the cast, and
/// in order for the remaining suffix (prefix) to contain the leftover
/// bytes.
///
/// There are three conditions under which a cast can fail:
/// - The smallest possible value for the type is larger than the provided
/// memory region
/// - A prefix cast is requested, and `addr` does not satisfy `self`'s
/// alignment requirement
/// - A suffix cast is requested, and `addr + bytes_len` does not satisfy
/// `self`'s alignment requirement (as a consequence, since all instances
/// of the type are a multiple of its alignment, no size for the type will
/// result in a starting address which is properly aligned)
///
/// # Safety
///
/// The caller may assume that this implementation is correct, and may rely
/// on that assumption for the soundness of their code. In particular, the
/// caller may assume that, if `validate_cast_and_convert_metadata` returns
/// `Some((elems, split_at))`, then:
/// - A pointer to the type (for dynamically sized types, this includes
/// `elems` as its pointer metadata) describes an object of size `size <=
/// bytes_len`
/// - If this is a prefix cast:
/// - `addr` satisfies `self`'s alignment
/// - `size == split_at`
/// - If this is a suffix cast:
/// - `split_at == bytes_len - size`
/// - `addr + split_at` satisfies `self`'s alignment
///
/// Note that this method does *not* ensure that a pointer constructed from
/// its return values will be a valid pointer. In particular, this method
/// does not reason about `isize` overflow, which is a requirement of many
/// Rust pointer APIs, and may at some point be determined to be a validity
/// invariant of pointer types themselves. This should never be a problem so
/// long as the arguments to this method are derived from a known-valid
/// pointer (e.g., one derived from a safe Rust reference), but it is
/// nonetheless the caller's responsibility to justify that pointer
/// arithmetic will not overflow based on a safety argument *other than* the
/// mere fact that this method returned successfully.
///
/// # Panics
///
/// `validate_cast_and_convert_metadata` will panic if `self` describes a
/// DST whose trailing slice element is zero-sized.
///
/// If `addr + bytes_len` overflows `usize`,
/// `validate_cast_and_convert_metadata` may panic, or it may return
/// incorrect results. No guarantees are made about when
/// `validate_cast_and_convert_metadata` will panic. The caller should not
/// rely on `validate_cast_and_convert_metadata` panicking in any particular
/// condition, even if `debug_assertions` are enabled.
#[allow(unused)]
const fn validate_cast_and_convert_metadata(
&self,
addr: usize,
bytes_len: usize,
cast_type: _CastType,
) -> Option<(usize, usize)> {
// `debug_assert!`, but with `#[allow(clippy::arithmetic_side_effects)]`.
macro_rules! __debug_assert {
($e:expr $(, $msg:expr)?) => {
debug_assert!({
#[allow(clippy::arithmetic_side_effects)]
let e = $e;
e
} $(, $msg)?);
};
}
// Note that, in practice, `self` is always a compile-time constant. We
// do this check earlier than needed to ensure that we always panic as a
// result of bugs in the program (such as calling this function on an
// invalid type) instead of allowing this panic to be hidden if the cast
// would have failed anyway for runtime reasons (such as a too-small
// memory region).
//
// TODO(#67): Once our MSRV is 1.65, use let-else:
// https://blog.rust-lang.org/2022/11/03/Rust-1.65.0.html#let-else-statements
let size_info = match self.size_info.try_to_nonzero_elem_size() {
Some(size_info) => size_info,
None => panic!("attempted to cast to slice type with zero-sized element"),
};
// Precondition
__debug_assert!(addr.checked_add(bytes_len).is_some(), "`addr` + `bytes_len` > usize::MAX");
// Alignment checks go in their own block to avoid introducing variables
// into the top-level scope.
{
// We check alignment for `addr` (for prefix casts) or `addr +
// bytes_len` (for suffix casts). For a prefix cast, the correctness
// of this check is trivial - `addr` is the address the object will
// live at.
//
// For a suffix cast, we know that all valid sizes for the type are
// a multiple of the alignment (and by safety precondition, we know
// `DstLayout` may only describe valid Rust types). Thus, a
// validly-sized instance which lives at a validly-aligned address
// must also end at a validly-aligned address. Thus, if the end
// address for a suffix cast (`addr + bytes_len`) is not aligned,
// then no valid start address will be aligned either.
let offset = match cast_type {
_CastType::_Prefix => 0,
_CastType::_Suffix => bytes_len,
};
// Addition is guaranteed not to overflow because `offset <=
// bytes_len`, and `addr + bytes_len <= usize::MAX` is a
// precondition of this method. Modulus is guaranteed not to divide
// by 0 because `align` is non-zero.
#[allow(clippy::arithmetic_side_effects)]
if (addr + offset) % self.align.get() != 0 {
return None;
}
}
let (elems, self_bytes) = match size_info {
SizeInfo::Sized { _size: size } => {
if size > bytes_len {
return None;
}
(0, size)
}
SizeInfo::SliceDst(TrailingSliceLayout { _offset: offset, _elem_size: elem_size }) => {
// Calculate the maximum number of bytes that could be consumed
// - any number of bytes larger than this will either not be a
// multiple of the alignment, or will be larger than
// `bytes_len`.
let max_total_bytes =
util::round_down_to_next_multiple_of_alignment(bytes_len, self.align);
// Calculate the maximum number of bytes that could be consumed
// by the trailing slice.
//
// TODO(#67): Once our MSRV is 1.65, use let-else:
// https://blog.rust-lang.org/2022/11/03/Rust-1.65.0.html#let-else-statements
let max_slice_and_padding_bytes = match max_total_bytes.checked_sub(offset) {
Some(max) => max,
// `bytes_len` too small even for 0 trailing slice elements.
None => return None,
};
// Calculate the number of elements that fit in
// `max_slice_and_padding_bytes`; any remaining bytes will be
// considered padding.
//
// Guaranteed not to divide by zero: `elem_size` is non-zero.
#[allow(clippy::arithmetic_side_effects)]
let elems = max_slice_and_padding_bytes / elem_size.get();
// Guaranteed not to overflow on multiplication: `usize::MAX >=
// max_slice_and_padding_bytes >= (max_slice_and_padding_bytes /
// elem_size) * elem_size`.
//
// Guaranteed not to overflow on addition:
// - max_slice_and_padding_bytes == max_total_bytes - offset
// - elems * elem_size <= max_slice_and_padding_bytes == max_total_bytes - offset
// - elems * elem_size + offset <= max_total_bytes <= usize::MAX
#[allow(clippy::arithmetic_side_effects)]
let without_padding = offset + elems * elem_size.get();
// `self_bytes` is equal to the offset bytes plus the bytes
// consumed by the trailing slice plus any padding bytes
// required to satisfy the alignment. Note that we have computed
// the maximum number of trailing slice elements that could fit
// in `self_bytes`, so any padding is guaranteed to be less than
// the size of an extra element.
//
// Guaranteed not to overflow:
// - By previous comment: without_padding == elems * elem_size +
// offset <= max_total_bytes
// - By construction, `max_total_bytes` is a multiple of
// `self.align`.
// - At most, adding padding needed to round `without_padding`
// up to the next multiple of the alignment will bring
// `self_bytes` up to `max_total_bytes`.
#[allow(clippy::arithmetic_side_effects)]
let self_bytes = without_padding
+ util::core_layout::padding_needed_for(without_padding, self.align);
(elems, self_bytes)
}
};
__debug_assert!(self_bytes <= bytes_len);
let split_at = match cast_type {
_CastType::_Prefix => self_bytes,
// Guaranteed not to underflow:
// - In the `Sized` branch, only returns `size` if `size <=
// bytes_len`.
// - In the `SliceDst` branch, calculates `self_bytes <=
// max_toatl_bytes`, which is upper-bounded by `bytes_len`.
#[allow(clippy::arithmetic_side_effects)]
_CastType::_Suffix => bytes_len - self_bytes,
};
Some((elems, split_at))
}
}
/// A trait which carries information about a type's layout that is used by the
/// internals of this crate.
///
/// This trait is not meant for consumption by code outside of this crate. While
/// the normal semver stability guarantees apply with respect to which types
/// implement this trait and which trait implementations are implied by this
/// trait, no semver stability guarantees are made regarding its internals; they
/// may change at any time, and code which makes use of them may break.
///
/// # Safety
///
/// This trait does not convey any safety guarantees to code outside this crate.
#[doc(hidden)] // TODO: Remove this once KnownLayout is used by other APIs
pub unsafe trait KnownLayout {
// The `Self: Sized` bound makes it so that `KnownLayout` can still be
// object safe. It's not currently object safe thanks to `const LAYOUT`, and
// it likely won't be in the future, but there's no reason not to be
// forwards-compatible with object safety.
#[doc(hidden)]
fn only_derive_is_allowed_to_implement_this_trait()
where
Self: Sized;
#[doc(hidden)]
const LAYOUT: DstLayout;
/// SAFETY: The returned pointer has the same address and provenance as
/// `bytes`. If `Self` is a DST, the returned pointer's referent has `elems`
/// elements in its trailing slice. If `Self` is sized, `elems` is ignored.
#[doc(hidden)]
fn raw_from_ptr_len(bytes: NonNull<u8>, elems: usize) -> NonNull<Self>;
}
// SAFETY: Delegates safety to `DstLayout::for_slice`.
unsafe impl<T: KnownLayout> KnownLayout for [T] {
#[allow(clippy::missing_inline_in_public_items)]
fn only_derive_is_allowed_to_implement_this_trait()
where
Self: Sized,
{
}
const LAYOUT: DstLayout = DstLayout::for_slice::<T>();
// SAFETY: `.cast` preserves address and provenance. The returned pointer
// refers to an object with `elems` elements by construction.
#[inline(always)]
fn raw_from_ptr_len(data: NonNull<u8>, elems: usize) -> NonNull<Self> {
// TODO(#67): Remove this allow. See NonNullExt for more details.
#[allow(unstable_name_collisions)]
NonNull::slice_from_raw_parts(data.cast::<T>(), elems)
}
}
#[rustfmt::skip]
impl_known_layout!(
(),
u8, i8, u16, i16, u32, i32, u64, i64, u128, i128, usize, isize, f32, f64,
bool, char,
NonZeroU8, NonZeroI8, NonZeroU16, NonZeroI16, NonZeroU32, NonZeroI32,
NonZeroU64, NonZeroI64, NonZeroU128, NonZeroI128, NonZeroUsize, NonZeroIsize
);
#[rustfmt::skip]
impl_known_layout!(
T => Option<T>,
T: ?Sized => PhantomData<T>,
T => Wrapping<T>,
T => MaybeUninit<T>,
T: ?Sized => *const T,
T: ?Sized => *mut T,
);
impl_known_layout!(const N: usize, T => [T; N]);
safety_comment! {
/// SAFETY:
/// `str` and `ManuallyDrop<[T]>` [1] have the same representations as
/// `[u8]` and `[T]` repsectively. `str` has different bit validity than
/// `[u8]`, but that doesn't affect the soundness of this impl.
///
/// [1] Per https://doc.rust-lang.org/nightly/core/mem/struct.ManuallyDrop.html:
///
/// `ManuallyDrop<T>` is guaranteed to have the same layout and bit
/// validity as `T`
///
/// TODO(#429):
/// - Add quotes from docs.
/// - Once [1] (added in
/// https://github.com/rust-lang/rust/pull/115522) is available on stable,
/// quote the stable docs instead of the nightly docs.
unsafe_impl_known_layout!(#[repr([u8])] str);
unsafe_impl_known_layout!(T: ?Sized + KnownLayout => #[repr(T)] ManuallyDrop<T>);
}
/// Analyzes whether a type is [`FromZeroes`].
///
/// This derive analyzes, at compile time, whether the annotated type satisfies
/// the [safety conditions] of `FromZeroes` and implements `FromZeroes` if it is
/// sound to do so. This derive can be applied to structs, enums, and unions;
/// e.g.:
///
/// ```
/// # use zerocopy_derive::FromZeroes;
/// #[derive(FromZeroes)]
/// struct MyStruct {
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes)]
/// #[repr(u8)]
/// enum MyEnum {
/// # Variant0,
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes)]
/// union MyUnion {
/// # variant: u8,
/// # /*
/// ...
/// # */
/// }
/// ```
///
/// [safety conditions]: trait@FromZeroes#safety
///
/// # Analysis
///
/// *This section describes, roughly, the analysis performed by this derive to
/// determine whether it is sound to implement `FromZeroes` for a given type.
/// Unless you are modifying the implementation of this derive, or attempting to
/// manually implement `FromZeroes` for a type yourself, you don't need to read
/// this section.*
///
/// If a type has the following properties, then this derive can implement
/// `FromZeroes` for that type:
///
/// - If the type is a struct, all of its fields must be `FromZeroes`.
/// - If the type is an enum, it must be C-like (meaning that all variants have
/// no fields) and it must have a variant with a discriminant of `0`. See [the
/// reference] for a description of how discriminant values are chosen.
/// - The type must not contain any [`UnsafeCell`]s (this is required in order
/// for it to be sound to construct a `&[u8]` and a `&T` to the same region of
/// memory). The type may contain references or pointers to `UnsafeCell`s so
/// long as those values can themselves be initialized from zeroes
/// (`FromZeroes` is not currently implemented for, e.g.,
/// `Option<&UnsafeCell<_>>`, but it could be one day).
///
/// This analysis is subject to change. Unsafe code may *only* rely on the
/// documented [safety conditions] of `FromZeroes`, and must *not* rely on the
/// implementation details of this derive.
///
/// [the reference]: https://doc.rust-lang.org/reference/items/enumerations.html#custom-discriminant-values-for-fieldless-enumerations
/// [`UnsafeCell`]: core::cell::UnsafeCell
///
/// ## Why isn't an explicit representation required for structs?
///
/// Neither this derive, nor the [safety conditions] of `FromZeroes`, requires
/// that structs are marked with `#[repr(C)]`.
///
/// Per the [Rust reference](reference),
///
/// > The representation of a type can change the padding between fields, but
/// > does not change the layout of the fields themselves.
///
/// [reference]: https://doc.rust-lang.org/reference/type-layout.html#representations
///
/// Since the layout of structs only consists of padding bytes and field bytes,
/// a struct is soundly `FromZeroes` if:
/// 1. its padding is soundly `FromZeroes`, and
/// 2. its fields are soundly `FromZeroes`.
///
/// The answer to the first question is always yes: padding bytes do not have
/// any validity constraints. A [discussion] of this question in the Unsafe Code
/// Guidelines Working Group concluded that it would be virtually unimaginable
/// for future versions of rustc to add validity constraints to padding bytes.
///
/// [discussion]: https://github.com/rust-lang/unsafe-code-guidelines/issues/174
///
/// Whether a struct is soundly `FromZeroes` therefore solely depends on whether
/// its fields are `FromZeroes`.
// TODO(#146): Document why we don't require an enum to have an explicit `repr`
// attribute.
#[cfg(any(feature = "derive", test))]
#[cfg_attr(doc_cfg, doc(cfg(feature = "derive")))]
pub use zerocopy_derive::FromZeroes;
/// Types whose validity can be checked at runtime, allowing them to be
/// conditionally converted from byte slices.
///
/// WARNING: Do not implement this trait yourself! Instead, use
/// `#[derive(TryFromBytes)]`.
///
/// `TryFromBytes` types can safely be deserialized from an untrusted sequence
/// of bytes by performing a runtime check that the byte sequence contains a
/// valid instance of `Self`.
///
/// `TryFromBytes` is ignorant of byte order. For byte order-aware types, see
/// the [`byteorder`] module.
///
/// # What is a "valid instance"?
///
/// In Rust, each type has *bit validity*, which refers to the set of bit
/// patterns which may appear in an instance of that type. It is impossible for
/// safe Rust code to produce values which violate bit validity (ie, values
/// outside of the "valid" set of bit patterns). If `unsafe` code produces an
/// invalid value, this is considered [undefined behavior].
///
/// Rust's bit validity rules are currently being decided, which means that some
/// types have three classes of bit patterns: those which are definitely valid,
/// and whose validity is documented in the language; those which may or may not
/// be considered valid at some point in the future; and those which are
/// definitely invalid.
///
/// Zerocopy takes a conservative approach, and only considers a bit pattern to
/// be valid if its validity is a documenteed guarantee provided by the
/// language.
///
/// For most use cases, Rust's current guarantees align with programmers'
/// intuitions about what ought to be valid. As a result, zerocopy's
/// conservatism should not affect most users. One notable exception is unions,
/// whose bit validity is very up in the air; zerocopy does not permit
/// implementing `TryFromBytes` for any union type.
///
/// If you are negatively affected by lack of support for a particular type,
/// we encourage you to let us know by [filing an issue][github-repo].
///
/// # Safety
///
/// On its own, `T: TryFromBytes` does not make any guarantees about the layout
/// or representation of `T`. It merely provides the ability to perform a
/// validity check at runtime via methods like [`try_from_ref`].
///
/// Currently, it is not possible to stably implement `TryFromBytes` other than
/// by using `#[derive(TryFromBytes)]`. While there are `#[doc(hidden)]` items
/// on this trait that provide well-defined safety invariants, no stability
/// guarantees are made with respect to these items. In particular, future
/// releases of zerocopy may make backwards-breaking changes to these items,
/// including changes that only affect soundness, which may cause code which
/// uses those items to silently become unsound.
///
/// [undefined behavior]: https://raphlinus.github.io/programming/rust/2018/08/17/undefined-behavior.html
/// [github-repo]: https://github.com/google/zerocopy
/// [`try_from_ref`]: TryFromBytes::try_from_ref
// TODO(#5): Update `try_from_ref` doc link once it exists
#[doc(hidden)]
pub unsafe trait TryFromBytes {
/// Does a given memory range contain a valid instance of `Self`?
///
/// # Safety
///
/// ## Preconditions
///
/// The memory referenced by `candidate` may only be accessed via reads for
/// the duration of this method call. This prohibits writes through mutable
/// references and through [`UnsafeCell`]s. There may exist immutable
/// references to the same memory which contain `UnsafeCell`s so long as:
/// - Those `UnsafeCell`s exist at the same byte ranges as `UnsafeCell`s in
/// `Self`. This is a bidirectional property: `Self` may not contain
/// `UnsafeCell`s where other references to the same memory do not, and
/// vice-versa.
/// - Those `UnsafeCell`s are never used to perform mutation for the
/// duration of this method call.
///
/// The memory referenced by `candidate` may not be referenced by any
/// mutable references even if these references are not used to perform
/// mutation.
///
/// `candidate` is not required to refer to a valid `Self`. However, it must
/// satisfy the requirement that uninitialized bytes may only be present
/// where it is possible for them to be present in `Self`. This is a dynamic
/// property: if, at a particular byte offset, a valid enum discriminant is
/// set, the subsequent bytes may only have uninitialized bytes as
/// specificed by the corresponding enum.
///
/// Formally, given `len = size_of_val_raw(candidate)`, at every byte
/// offset, `b`, in the range `[0, len)`:
/// - If, in all instances `s: Self` of length `len`, the byte at offset `b`
/// in `s` is initialized, then the byte at offset `b` within `*candidate`
/// must be initialized.
/// - Let `c` be the contents of the byte range `[0, b)` in `*candidate`.
/// Let `S` be the subset of valid instances of `Self` of length `len`
/// which contain `c` in the offset range `[0, b)`. If, for all instances
/// of `s: Self` in `S`, the byte at offset `b` in `s` is initialized,
/// then the byte at offset `b` in `*candidate` must be initialized.
///
/// Pragmatically, this means that if `*candidate` is guaranteed to
/// contain an enum type at a particular offset, and the enum discriminant
/// stored in `*candidate` corresponds to a valid variant of that enum
/// type, then it is guaranteed that the appropriate bytes of `*candidate`
/// are initialized as defined by that variant's bit validity (although
/// note that the variant may contain another enum type, in which case the
/// same rules apply depending on the state of its discriminant, and so on
/// recursively).
///
/// ## Postconditions
///
/// Unsafe code may assume that, if `is_bit_valid(candidate)` returns true,
/// `*candidate` contains a valid `Self`.
///
/// # Panics
///
/// `is_bit_valid` may panic. Callers are responsible for ensuring that any
/// `unsafe` code remains sound even in the face of `is_bit_valid`
/// panicking. (We support user-defined validation routines; so long as
/// these routines are not required to be `unsafe`, there is no way to
/// ensure that these do not generate panics.)
///
/// [`UnsafeCell`]: core::cell::UnsafeCell
#[doc(hidden)]
unsafe fn is_bit_valid(candidate: Ptr<'_, Self>) -> bool;
/// Attempts to interpret a byte slice as a `Self`.
///
/// `try_from_ref` validates that `bytes` contains a valid `Self`, and that
/// it satisfies `Self`'s alignment requirement. If it does, then `bytes` is
/// reinterpreted as a `Self`.
///
/// Note that Rust's bit validity rules are still being decided. As such,
/// there exist types whose bit validity is ambiguous. See the
/// `TryFromBytes` docs for a discussion of how these cases are handled.
// TODO(#251): In a future in which we distinguish between `FromBytes` and
// `RefFromBytes`, this requires `where Self: RefFromBytes` to disallow
// interior mutability.
#[inline]
#[doc(hidden)] // TODO(#5): Finalize name before remove this attribute.
fn try_from_ref(bytes: &[u8]) -> Option<&Self>
where
Self: KnownLayout,
{
let maybe_self = Ptr::from(bytes).try_cast_into_no_leftover::<Self>()?;
// SAFETY:
// - Since `bytes` is an immutable reference, we know that no mutable
// references exist to this memory region.
// - Since `[u8]` contains no `UnsafeCell`s, we know there are no
// `&UnsafeCell` references to this memory region.
// - Since we don't permit implementing `TryFromBytes` for types which
// contain `UnsafeCell`s, there are no `UnsafeCell`s in `Self`, and so
// the requirement that all references contain `UnsafeCell`s at the
// same offsets is trivially satisfied.
// - All bytes of `bytes` are initialized.
//
// This call may panic. If that happens, it doesn't cause any soundness
// issues, as we have not generated any invalid state which we need to
// fix before returning.
if unsafe { !Self::is_bit_valid(maybe_self) } {
return None;
}
// SAFETY:
// - Preconditions for `as_ref`:
// - `is_bit_valid` guarantees that `*maybe_self` contains a valid
// `Self`. Since `&[u8]` does not permit interior mutation, this
// cannot be invalidated after this method returns.
// - Since the argument and return types are immutable references,
// Rust will prevent the caller from producing any mutable
// references to the same memory region.
// - Since `Self` is not allowed to contain any `UnsafeCell`s and the
// same is true of `[u8]`, interior mutation is not possible. Thus,
// no mutation is possible. For the same reason, there is no
// mismatch between the two types in terms of which byte ranges are
// referenced as `UnsafeCell`s.
// - Since interior mutation isn't possible within `Self`, there's no
// way for the returned reference to be used to modify the byte range,
// and thus there's no way for the returned reference to be used to
// write an invalid `[u8]` which would be observable via the original
// `&[u8]`.
Some(unsafe { maybe_self.as_ref() })
}
}
/// Types for which a sequence of bytes all set to zero represents a valid
/// instance of the type.
///
/// Any memory region of the appropriate length which is guaranteed to contain
/// only zero bytes can be viewed as any `FromZeroes` type with no runtime
/// overhead. This is useful whenever memory is known to be in a zeroed state,
/// such memory returned from some allocation routines.
///
/// # Implementation
///
/// **Do not implement this trait yourself!** Instead, use
/// [`#[derive(FromZeroes)]`][derive] (requires the `derive` Cargo feature);
/// e.g.:
///
/// ```
/// # use zerocopy_derive::FromZeroes;
/// #[derive(FromZeroes)]
/// struct MyStruct {
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes)]
/// #[repr(u8)]
/// enum MyEnum {
/// # Variant0,
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes)]
/// union MyUnion {
/// # variant: u8,
/// # /*
/// ...
/// # */
/// }
/// ```
///
/// This derive performs a sophisticated, compile-time safety analysis to
/// determine whether a type is `FromZeroes`.
///
/// # Safety
///
/// *This section describes what is required in order for `T: FromZeroes`, and
/// what unsafe code may assume of such types. If you don't plan on implementing
/// `FromZeroes` manually, and you don't plan on writing unsafe code that
/// operates on `FromZeroes` types, then you don't need to read this section.*
///
/// If `T: FromZeroes`, then unsafe code may assume that:
/// - It is sound to treat any initialized sequence of zero bytes of length
/// `size_of::<T>()` as a `T`.
/// - Given `b: &[u8]` where `b.len() == size_of::<T>()`, `b` is aligned to
/// `align_of::<T>()`, and `b` contains only zero bytes, it is sound to
/// construct a `t: &T` at the same address as `b`, and it is sound for both
/// `b` and `t` to be live at the same time.
///
/// If a type is marked as `FromZeroes` which violates this contract, it may
/// cause undefined behavior.
///
/// `#[derive(FromZeroes)]` only permits [types which satisfy these
/// requirements][derive-analysis].
///
#[cfg_attr(
feature = "derive",
doc = "[derive]: zerocopy_derive::FromZeroes",
doc = "[derive-analysis]: zerocopy_derive::FromZeroes#analysis"
)]
#[cfg_attr(
not(feature = "derive"),
doc = concat!("[derive]: https://docs.rs/zerocopy/", env!("CARGO_PKG_VERSION"), "/zerocopy/derive.FromZeroes.html"),
doc = concat!("[derive-analysis]: https://docs.rs/zerocopy/", env!("CARGO_PKG_VERSION"), "/zerocopy/derive.FromZeroes.html#analysis"),
)]
pub unsafe trait FromZeroes {
// The `Self: Sized` bound makes it so that `FromZeroes` is still object
// safe.
#[doc(hidden)]
fn only_derive_is_allowed_to_implement_this_trait()
where
Self: Sized;
/// Overwrites `self` with zeroes.
///
/// Sets every byte in `self` to 0. While this is similar to doing `*self =
/// Self::new_zeroed()`, it differs in that `zero` does not semantically
/// drop the current value and replace it with a new one - it simply
/// modifies the bytes of the existing value.
///
/// # Examples
///
/// ```
/// # use zerocopy::FromZeroes;
/// # use zerocopy_derive::*;
/// #
/// #[derive(FromZeroes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// let mut header = PacketHeader {
/// src_port: 100u16.to_be_bytes(),
/// dst_port: 200u16.to_be_bytes(),
/// length: 300u16.to_be_bytes(),
/// checksum: 400u16.to_be_bytes(),
/// };
///
/// header.zero();
///
/// assert_eq!(header.src_port, [0, 0]);
/// assert_eq!(header.dst_port, [0, 0]);
/// assert_eq!(header.length, [0, 0]);
/// assert_eq!(header.checksum, [0, 0]);
/// ```
#[inline(always)]
fn zero(&mut self) {
let slf: *mut Self = self;
let len = mem::size_of_val(self);
// SAFETY:
// - `self` is guaranteed by the type system to be valid for writes of
// size `size_of_val(self)`.
// - `u8`'s alignment is 1, and thus `self` is guaranteed to be aligned
// as required by `u8`.
// - Since `Self: FromZeroes`, the all-zeroes instance is a valid
// instance of `Self.`
//
// TODO(#429): Add references to docs and quotes.
unsafe { ptr::write_bytes(slf.cast::<u8>(), 0, len) };
}
/// Creates an instance of `Self` from zeroed bytes.
///
/// # Examples
///
/// ```
/// # use zerocopy::FromZeroes;
/// # use zerocopy_derive::*;
/// #
/// #[derive(FromZeroes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// let header: PacketHeader = FromZeroes::new_zeroed();
///
/// assert_eq!(header.src_port, [0, 0]);
/// assert_eq!(header.dst_port, [0, 0]);
/// assert_eq!(header.length, [0, 0]);
/// assert_eq!(header.checksum, [0, 0]);
/// ```
#[inline(always)]
fn new_zeroed() -> Self
where
Self: Sized,
{
// SAFETY: `FromZeroes` says that the all-zeroes bit pattern is legal.
unsafe { mem::zeroed() }
}
/// Creates a `Box<Self>` from zeroed bytes.
///
/// This function is useful for allocating large values on the heap and
/// zero-initializing them, without ever creating a temporary instance of
/// `Self` on the stack. For example, `<[u8; 1048576]>::new_box_zeroed()`
/// will allocate `[u8; 1048576]` directly on the heap; it does not require
/// storing `[u8; 1048576]` in a temporary variable on the stack.
///
/// On systems that use a heap implementation that supports allocating from
/// pre-zeroed memory, using `new_box_zeroed` (or related functions) may
/// have performance benefits.
///
/// Note that `Box<Self>` can be converted to `Arc<Self>` and other
/// container types without reallocation.
///
/// # Panics
///
/// Panics if allocation of `size_of::<Self>()` bytes fails.
#[cfg(feature = "alloc")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
#[inline]
fn new_box_zeroed() -> Box<Self>
where
Self: Sized,
{
// If `T` is a ZST, then return a proper boxed instance of it. There is
// no allocation, but `Box` does require a correct dangling pointer.
let layout = Layout::new::<Self>();
if layout.size() == 0 {
return Box::new(Self::new_zeroed());
}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
let ptr = unsafe { alloc::alloc::alloc_zeroed(layout).cast::<Self>() };
if ptr.is_null() {
alloc::alloc::handle_alloc_error(layout);
}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe {
Box::from_raw(ptr)
}
}
/// Creates a `Box<[Self]>` (a boxed slice) from zeroed bytes.
///
/// This function is useful for allocating large values of `[Self]` on the
/// heap and zero-initializing them, without ever creating a temporary
/// instance of `[Self; _]` on the stack. For example,
/// `u8::new_box_slice_zeroed(1048576)` will allocate the slice directly on
/// the heap; it does not require storing the slice on the stack.
///
/// On systems that use a heap implementation that supports allocating from
/// pre-zeroed memory, using `new_box_slice_zeroed` may have performance
/// benefits.
///
/// If `Self` is a zero-sized type, then this function will return a
/// `Box<[Self]>` that has the correct `len`. Such a box cannot contain any
/// actual information, but its `len()` property will report the correct
/// value.
///
/// # Panics
///
/// * Panics if `size_of::<Self>() * len` overflows.
/// * Panics if allocation of `size_of::<Self>() * len` bytes fails.
#[cfg(feature = "alloc")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
#[inline]
fn new_box_slice_zeroed(len: usize) -> Box<[Self]>
where
Self: Sized,
{
let size = mem::size_of::<Self>()
.checked_mul(len)
.expect("mem::size_of::<Self>() * len overflows `usize`");
let align = mem::align_of::<Self>();
// On stable Rust versions <= 1.64.0, `Layout::from_size_align` has a
// bug in which sufficiently-large allocations (those which, when
// rounded up to the alignment, overflow `isize`) are not rejected,
// which can cause undefined behavior. See #64 for details.
//
// TODO(#67): Once our MSRV is > 1.64.0, remove this assertion.
#[allow(clippy::as_conversions)]
let max_alloc = (isize::MAX as usize).saturating_sub(align);
assert!(size <= max_alloc);
// TODO(https://github.com/rust-lang/rust/issues/55724): Use
// `Layout::repeat` once it's stabilized.
let layout =
Layout::from_size_align(size, align).expect("total allocation size overflows `isize`");
let ptr = if layout.size() != 0 {
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
let ptr = unsafe { alloc::alloc::alloc_zeroed(layout).cast::<Self>() };
if ptr.is_null() {
alloc::alloc::handle_alloc_error(layout);
}
ptr
} else {
// `Box<[T]>` does not allocate when `T` is zero-sized or when `len`
// is zero, but it does require a non-null dangling pointer for its
// allocation.
NonNull::<Self>::dangling().as_ptr()
};
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe {
Box::from_raw(slice::from_raw_parts_mut(ptr, len))
}
}
/// Creates a `Vec<Self>` from zeroed bytes.
///
/// This function is useful for allocating large values of `Vec`s and
/// zero-initializing them, without ever creating a temporary instance of
/// `[Self; _]` (or many temporary instances of `Self`) on the stack. For
/// example, `u8::new_vec_zeroed(1048576)` will allocate directly on the
/// heap; it does not require storing intermediate values on the stack.
///
/// On systems that use a heap implementation that supports allocating from
/// pre-zeroed memory, using `new_vec_zeroed` may have performance benefits.
///
/// If `Self` is a zero-sized type, then this function will return a
/// `Vec<Self>` that has the correct `len`. Such a `Vec` cannot contain any
/// actual information, but its `len()` property will report the correct
/// value.
///
/// # Panics
///
/// * Panics if `size_of::<Self>() * len` overflows.
/// * Panics if allocation of `size_of::<Self>() * len` bytes fails.
#[cfg(feature = "alloc")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "new_vec_zeroed")))]
#[inline(always)]
fn new_vec_zeroed(len: usize) -> Vec<Self>
where
Self: Sized,
{
Self::new_box_slice_zeroed(len).into()
}
}
/// Analyzes whether a type is [`FromBytes`].
///
/// This derive analyzes, at compile time, whether the annotated type satisfies
/// the [safety conditions] of `FromBytes` and implements `FromBytes` if it is
/// sound to do so. This derive can be applied to structs, enums, and unions;
/// e.g.:
///
/// ```
/// # use zerocopy_derive::{FromBytes, FromZeroes};
/// #[derive(FromZeroes, FromBytes)]
/// struct MyStruct {
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(u8)]
/// enum MyEnum {
/// # V00, V01, V02, V03, V04, V05, V06, V07, V08, V09, V0A, V0B, V0C, V0D, V0E,
/// # V0F, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V1A, V1B, V1C, V1D,
/// # V1E, V1F, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V2A, V2B, V2C,
/// # V2D, V2E, V2F, V30, V31, V32, V33, V34, V35, V36, V37, V38, V39, V3A, V3B,
/// # V3C, V3D, V3E, V3F, V40, V41, V42, V43, V44, V45, V46, V47, V48, V49, V4A,
/// # V4B, V4C, V4D, V4E, V4F, V50, V51, V52, V53, V54, V55, V56, V57, V58, V59,
/// # V5A, V5B, V5C, V5D, V5E, V5F, V60, V61, V62, V63, V64, V65, V66, V67, V68,
/// # V69, V6A, V6B, V6C, V6D, V6E, V6F, V70, V71, V72, V73, V74, V75, V76, V77,
/// # V78, V79, V7A, V7B, V7C, V7D, V7E, V7F, V80, V81, V82, V83, V84, V85, V86,
/// # V87, V88, V89, V8A, V8B, V8C, V8D, V8E, V8F, V90, V91, V92, V93, V94, V95,
/// # V96, V97, V98, V99, V9A, V9B, V9C, V9D, V9E, V9F, VA0, VA1, VA2, VA3, VA4,
/// # VA5, VA6, VA7, VA8, VA9, VAA, VAB, VAC, VAD, VAE, VAF, VB0, VB1, VB2, VB3,
/// # VB4, VB5, VB6, VB7, VB8, VB9, VBA, VBB, VBC, VBD, VBE, VBF, VC0, VC1, VC2,
/// # VC3, VC4, VC5, VC6, VC7, VC8, VC9, VCA, VCB, VCC, VCD, VCE, VCF, VD0, VD1,
/// # VD2, VD3, VD4, VD5, VD6, VD7, VD8, VD9, VDA, VDB, VDC, VDD, VDE, VDF, VE0,
/// # VE1, VE2, VE3, VE4, VE5, VE6, VE7, VE8, VE9, VEA, VEB, VEC, VED, VEE, VEF,
/// # VF0, VF1, VF2, VF3, VF4, VF5, VF6, VF7, VF8, VF9, VFA, VFB, VFC, VFD, VFE,
/// # VFF,
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes, FromBytes)]
/// union MyUnion {
/// # variant: u8,
/// # /*
/// ...
/// # */
/// }
/// ```
///
/// [safety conditions]: trait@FromBytes#safety
///
/// # Analysis
///
/// *This section describes, roughly, the analysis performed by this derive to
/// determine whether it is sound to implement `FromBytes` for a given type.
/// Unless you are modifying the implementation of this derive, or attempting to
/// manually implement `FromBytes` for a type yourself, you don't need to read
/// this section.*
///
/// If a type has the following properties, then this derive can implement
/// `FromBytes` for that type:
///
/// - If the type is a struct, all of its fields must be `FromBytes`.
/// - If the type is an enum:
/// - It must be a C-like enum (meaning that all variants have no fields).
/// - It must have a defined representation (`repr`s `C`, `u8`, `u16`, `u32`,
/// `u64`, `usize`, `i8`, `i16`, `i32`, `i64`, or `isize`).
/// - The maximum number of discriminants must be used (so that every possible
/// bit pattern is a valid one). Be very careful when using the `C`,
/// `usize`, or `isize` representations, as their size is
/// platform-dependent.
/// - The type must not contain any [`UnsafeCell`]s (this is required in order
/// for it to be sound to construct a `&[u8]` and a `&T` to the same region of
/// memory). The type may contain references or pointers to `UnsafeCell`s so
/// long as those values can themselves be initialized from zeroes
/// (`FromBytes` is not currently implemented for, e.g., `Option<*const
/// UnsafeCell<_>>`, but it could be one day).
///
/// [`UnsafeCell`]: core::cell::UnsafeCell
///
/// This analysis is subject to change. Unsafe code may *only* rely on the
/// documented [safety conditions] of `FromBytes`, and must *not* rely on the
/// implementation details of this derive.
///
/// ## Why isn't an explicit representation required for structs?
///
/// Neither this derive, nor the [safety conditions] of `FromBytes`, requires
/// that structs are marked with `#[repr(C)]`.
///
/// Per the [Rust reference](reference),
///
/// > The representation of a type can change the padding between fields, but
/// > does not change the layout of the fields themselves.
///
/// [reference]: https://doc.rust-lang.org/reference/type-layout.html#representations
///
/// Since the layout of structs only consists of padding bytes and field bytes,
/// a struct is soundly `FromBytes` if:
/// 1. its padding is soundly `FromBytes`, and
/// 2. its fields are soundly `FromBytes`.
///
/// The answer to the first question is always yes: padding bytes do not have
/// any validity constraints. A [discussion] of this question in the Unsafe Code
/// Guidelines Working Group concluded that it would be virtually unimaginable
/// for future versions of rustc to add validity constraints to padding bytes.
///
/// [discussion]: https://github.com/rust-lang/unsafe-code-guidelines/issues/174
///
/// Whether a struct is soundly `FromBytes` therefore solely depends on whether
/// its fields are `FromBytes`.
// TODO(#146): Document why we don't require an enum to have an explicit `repr`
// attribute.
#[cfg(any(feature = "derive", test))]
#[cfg_attr(doc_cfg, doc(cfg(feature = "derive")))]
pub use zerocopy_derive::FromBytes;
/// Types for which any bit pattern is valid.
///
/// Any memory region of the appropriate length which contains initialized bytes
/// can be viewed as any `FromBytes` type with no runtime overhead. This is
/// useful for efficiently parsing bytes as structured data.
///
/// # Implementation
///
/// **Do not implement this trait yourself!** Instead, use
/// [`#[derive(FromBytes)]`][derive] (requires the `derive` Cargo feature);
/// e.g.:
///
/// ```
/// # use zerocopy_derive::{FromBytes, FromZeroes};
/// #[derive(FromZeroes, FromBytes)]
/// struct MyStruct {
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(u8)]
/// enum MyEnum {
/// # V00, V01, V02, V03, V04, V05, V06, V07, V08, V09, V0A, V0B, V0C, V0D, V0E,
/// # V0F, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V1A, V1B, V1C, V1D,
/// # V1E, V1F, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V2A, V2B, V2C,
/// # V2D, V2E, V2F, V30, V31, V32, V33, V34, V35, V36, V37, V38, V39, V3A, V3B,
/// # V3C, V3D, V3E, V3F, V40, V41, V42, V43, V44, V45, V46, V47, V48, V49, V4A,
/// # V4B, V4C, V4D, V4E, V4F, V50, V51, V52, V53, V54, V55, V56, V57, V58, V59,
/// # V5A, V5B, V5C, V5D, V5E, V5F, V60, V61, V62, V63, V64, V65, V66, V67, V68,
/// # V69, V6A, V6B, V6C, V6D, V6E, V6F, V70, V71, V72, V73, V74, V75, V76, V77,
/// # V78, V79, V7A, V7B, V7C, V7D, V7E, V7F, V80, V81, V82, V83, V84, V85, V86,
/// # V87, V88, V89, V8A, V8B, V8C, V8D, V8E, V8F, V90, V91, V92, V93, V94, V95,
/// # V96, V97, V98, V99, V9A, V9B, V9C, V9D, V9E, V9F, VA0, VA1, VA2, VA3, VA4,
/// # VA5, VA6, VA7, VA8, VA9, VAA, VAB, VAC, VAD, VAE, VAF, VB0, VB1, VB2, VB3,
/// # VB4, VB5, VB6, VB7, VB8, VB9, VBA, VBB, VBC, VBD, VBE, VBF, VC0, VC1, VC2,
/// # VC3, VC4, VC5, VC6, VC7, VC8, VC9, VCA, VCB, VCC, VCD, VCE, VCF, VD0, VD1,
/// # VD2, VD3, VD4, VD5, VD6, VD7, VD8, VD9, VDA, VDB, VDC, VDD, VDE, VDF, VE0,
/// # VE1, VE2, VE3, VE4, VE5, VE6, VE7, VE8, VE9, VEA, VEB, VEC, VED, VEE, VEF,
/// # VF0, VF1, VF2, VF3, VF4, VF5, VF6, VF7, VF8, VF9, VFA, VFB, VFC, VFD, VFE,
/// # VFF,
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(FromZeroes, FromBytes)]
/// union MyUnion {
/// # variant: u8,
/// # /*
/// ...
/// # */
/// }
/// ```
///
/// This derive performs a sophisticated, compile-time safety analysis to
/// determine whether a type is `FromBytes`.
///
/// # Safety
///
/// *This section describes what is required in order for `T: FromBytes`, and
/// what unsafe code may assume of such types. If you don't plan on implementing
/// `FromBytes` manually, and you don't plan on writing unsafe code that
/// operates on `FromBytes` types, then you don't need to read this section.*
///
/// If `T: FromBytes`, then unsafe code may assume that:
/// - It is sound to treat any initialized sequence of bytes of length
/// `size_of::<T>()` as a `T`.
/// - Given `b: &[u8]` where `b.len() == size_of::<T>()`, `b` is aligned to
/// `align_of::<T>()` it is sound to construct a `t: &T` at the same address
/// as `b`, and it is sound for both `b` and `t` to be live at the same time.
///
/// If a type is marked as `FromBytes` which violates this contract, it may
/// cause undefined behavior.
///
/// `#[derive(FromBytes)]` only permits [types which satisfy these
/// requirements][derive-analysis].
///
#[cfg_attr(
feature = "derive",
doc = "[derive]: zerocopy_derive::FromBytes",
doc = "[derive-analysis]: zerocopy_derive::FromBytes#analysis"
)]
#[cfg_attr(
not(feature = "derive"),
doc = concat!("[derive]: https://docs.rs/zerocopy/", env!("CARGO_PKG_VERSION"), "/zerocopy/derive.FromBytes.html"),
doc = concat!("[derive-analysis]: https://docs.rs/zerocopy/", env!("CARGO_PKG_VERSION"), "/zerocopy/derive.FromBytes.html#analysis"),
)]
pub unsafe trait FromBytes: FromZeroes {
// The `Self: Sized` bound makes it so that `FromBytes` is still object
// safe.
#[doc(hidden)]
fn only_derive_is_allowed_to_implement_this_trait()
where
Self: Sized;
/// Interprets the given `bytes` as a `&Self` without copying.
///
/// If `bytes.len() != size_of::<Self>()` or `bytes` is not aligned to
/// `align_of::<Self>()`, this returns `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// // These bytes encode a `PacketHeader`.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7].as_slice();
///
/// let header = PacketHeader::ref_from(bytes).unwrap();
///
/// assert_eq!(header.src_port, [0, 1]);
/// assert_eq!(header.dst_port, [2, 3]);
/// assert_eq!(header.length, [4, 5]);
/// assert_eq!(header.checksum, [6, 7]);
/// ```
#[inline]
fn ref_from(bytes: &[u8]) -> Option<&Self>
where
Self: Sized,
{
Ref::<&[u8], Self>::new(bytes).map(Ref::into_ref)
}
/// Interprets the prefix of the given `bytes` as a `&Self` without copying.
///
/// `ref_from_prefix` returns a reference to the first `size_of::<Self>()`
/// bytes of `bytes`. If `bytes.len() < size_of::<Self>()` or `bytes` is not
/// aligned to `align_of::<Self>()`, this returns `None`.
///
/// To also access the prefix bytes, use [`Ref::new_from_prefix`]. Then, use
/// [`Ref::into_ref`] to get a `&Self` with the same lifetime.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// // These are more bytes than are needed to encode a `PacketHeader`.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].as_slice();
///
/// let header = PacketHeader::ref_from_prefix(bytes).unwrap();
///
/// assert_eq!(header.src_port, [0, 1]);
/// assert_eq!(header.dst_port, [2, 3]);
/// assert_eq!(header.length, [4, 5]);
/// assert_eq!(header.checksum, [6, 7]);
/// ```
#[inline]
fn ref_from_prefix(bytes: &[u8]) -> Option<&Self>
where
Self: Sized,
{
Ref::<&[u8], Self>::new_from_prefix(bytes).map(|(r, _)| r.into_ref())
}
/// Interprets the suffix of the given `bytes` as a `&Self` without copying.
///
/// `ref_from_suffix` returns a reference to the last `size_of::<Self>()`
/// bytes of `bytes`. If `bytes.len() < size_of::<Self>()` or the suffix of
/// `bytes` is not aligned to `align_of::<Self>()`, this returns `None`.
///
/// To also access the suffix bytes, use [`Ref::new_from_suffix`]. Then, use
/// [`Ref::into_ref`] to get a `&Self` with the same lifetime.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketTrailer {
/// frame_check_sequence: [u8; 4],
/// }
///
/// // These are more bytes than are needed to encode a `PacketTrailer`.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].as_slice();
///
/// let trailer = PacketTrailer::ref_from_suffix(bytes).unwrap();
///
/// assert_eq!(trailer.frame_check_sequence, [6, 7, 8, 9]);
/// ```
#[inline]
fn ref_from_suffix(bytes: &[u8]) -> Option<&Self>
where
Self: Sized,
{
Ref::<&[u8], Self>::new_from_suffix(bytes).map(|(_, r)| r.into_ref())
}
/// Interprets the given `bytes` as a `&mut Self` without copying.
///
/// If `bytes.len() != size_of::<Self>()` or `bytes` is not aligned to
/// `align_of::<Self>()`, this returns `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(AsBytes, FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// // These bytes encode a `PacketHeader`.
/// let bytes = &mut [0, 1, 2, 3, 4, 5, 6, 7][..];
///
/// let header = PacketHeader::mut_from(bytes).unwrap();
///
/// assert_eq!(header.src_port, [0, 1]);
/// assert_eq!(header.dst_port, [2, 3]);
/// assert_eq!(header.length, [4, 5]);
/// assert_eq!(header.checksum, [6, 7]);
///
/// header.checksum = [0, 0];
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 0, 0]);
/// ```
#[inline]
fn mut_from(bytes: &mut [u8]) -> Option<&mut Self>
where
Self: Sized + AsBytes,
{
Ref::<&mut [u8], Self>::new(bytes).map(Ref::into_mut)
}
/// Interprets the prefix of the given `bytes` as a `&mut Self` without
/// copying.
///
/// `mut_from_prefix` returns a reference to the first `size_of::<Self>()`
/// bytes of `bytes`. If `bytes.len() < size_of::<Self>()` or `bytes` is not
/// aligned to `align_of::<Self>()`, this returns `None`.
///
/// To also access the prefix bytes, use [`Ref::new_from_prefix`]. Then, use
/// [`Ref::into_mut`] to get a `&mut Self` with the same lifetime.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(AsBytes, FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// // These are more bytes than are needed to encode a `PacketHeader`.
/// let bytes = &mut [0, 1, 2, 3, 4, 5, 6, 7, 8, 9][..];
///
/// let header = PacketHeader::mut_from_prefix(bytes).unwrap();
///
/// assert_eq!(header.src_port, [0, 1]);
/// assert_eq!(header.dst_port, [2, 3]);
/// assert_eq!(header.length, [4, 5]);
/// assert_eq!(header.checksum, [6, 7]);
///
/// header.checksum = [0, 0];
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 0, 0, 8, 9]);
/// ```
#[inline]
fn mut_from_prefix(bytes: &mut [u8]) -> Option<&mut Self>
where
Self: Sized + AsBytes,
{
Ref::<&mut [u8], Self>::new_from_prefix(bytes).map(|(r, _)| r.into_mut())
}
/// Interprets the suffix of the given `bytes` as a `&mut Self` without copying.
///
/// `mut_from_suffix` returns a reference to the last `size_of::<Self>()`
/// bytes of `bytes`. If `bytes.len() < size_of::<Self>()` or the suffix of
/// `bytes` is not aligned to `align_of::<Self>()`, this returns `None`.
///
/// To also access the suffix bytes, use [`Ref::new_from_suffix`]. Then,
/// use [`Ref::into_mut`] to get a `&mut Self` with the same lifetime.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(AsBytes, FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketTrailer {
/// frame_check_sequence: [u8; 4],
/// }
///
/// // These are more bytes than are needed to encode a `PacketTrailer`.
/// let bytes = &mut [0, 1, 2, 3, 4, 5, 6, 7, 8, 9][..];
///
/// let trailer = PacketTrailer::mut_from_suffix(bytes).unwrap();
///
/// assert_eq!(trailer.frame_check_sequence, [6, 7, 8, 9]);
///
/// trailer.frame_check_sequence = [0, 0, 0, 0];
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 0, 0, 0, 0]);
/// ```
#[inline]
fn mut_from_suffix(bytes: &mut [u8]) -> Option<&mut Self>
where
Self: Sized + AsBytes,
{
Ref::<&mut [u8], Self>::new_from_suffix(bytes).map(|(_, r)| r.into_mut())
}
/// Interprets the given `bytes` as a `&[Self]` without copying.
///
/// If `bytes.len() % size_of::<Self>() != 0` or `bytes` is not aligned to
/// `align_of::<Self>()`, this returns `None`.
///
/// If you need to convert a specific number of slice elements, see
/// [`slice_from_prefix`](FromBytes::slice_from_prefix) or
/// [`slice_from_suffix`](FromBytes::slice_from_suffix).
///
/// # Panics
///
/// If `Self` is a zero-sized type.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// # #[derive(Debug, PartialEq, Eq)]
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct Pixel {
/// r: u8,
/// g: u8,
/// b: u8,
/// a: u8,
/// }
///
/// // These bytes encode two `Pixel`s.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7].as_slice();
///
/// let pixels = Pixel::slice_from(bytes).unwrap();
///
/// assert_eq!(pixels, &[
/// Pixel { r: 0, g: 1, b: 2, a: 3 },
/// Pixel { r: 4, g: 5, b: 6, a: 7 },
/// ]);
/// ```
#[inline]
fn slice_from(bytes: &[u8]) -> Option<&[Self]>
where
Self: Sized,
{
Ref::<_, [Self]>::new_slice(bytes).map(|r| r.into_slice())
}
/// Interprets the prefix of the given `bytes` as a `&[Self]` with length
/// equal to `count` without copying.
///
/// This method verifies that `bytes.len() >= size_of::<T>() * count`
/// and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// first `size_of::<T>() * count` bytes from `bytes` to construct a
/// `&[Self]`, and returns the remaining bytes to the caller. It also
/// ensures that `sizeof::<T>() * count` does not overflow a `usize`.
/// If any of the length, alignment, or overflow checks fail, it returns
/// `None`.
///
/// # Panics
///
/// If `T` is a zero-sized type.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// # #[derive(Debug, PartialEq, Eq)]
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct Pixel {
/// r: u8,
/// g: u8,
/// b: u8,
/// a: u8,
/// }
///
/// // These are more bytes than are needed to encode two `Pixel`s.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].as_slice();
///
/// let (pixels, rest) = Pixel::slice_from_prefix(bytes, 2).unwrap();
///
/// assert_eq!(pixels, &[
/// Pixel { r: 0, g: 1, b: 2, a: 3 },
/// Pixel { r: 4, g: 5, b: 6, a: 7 },
/// ]);
///
/// assert_eq!(rest, &[8, 9]);
/// ```
#[inline]
fn slice_from_prefix(bytes: &[u8], count: usize) -> Option<(&[Self], &[u8])>
where
Self: Sized,
{
Ref::<_, [Self]>::new_slice_from_prefix(bytes, count).map(|(r, b)| (r.into_slice(), b))
}
/// Interprets the suffix of the given `bytes` as a `&[Self]` with length
/// equal to `count` without copying.
///
/// This method verifies that `bytes.len() >= size_of::<T>() * count`
/// and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// last `size_of::<T>() * count` bytes from `bytes` to construct a
/// `&[Self]`, and returns the preceding bytes to the caller. It also
/// ensures that `sizeof::<T>() * count` does not overflow a `usize`.
/// If any of the length, alignment, or overflow checks fail, it returns
/// `None`.
///
/// # Panics
///
/// If `T` is a zero-sized type.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// # #[derive(Debug, PartialEq, Eq)]
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct Pixel {
/// r: u8,
/// g: u8,
/// b: u8,
/// a: u8,
/// }
///
/// // These are more bytes than are needed to encode two `Pixel`s.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].as_slice();
///
/// let (rest, pixels) = Pixel::slice_from_suffix(bytes, 2).unwrap();
///
/// assert_eq!(rest, &[0, 1]);
///
/// assert_eq!(pixels, &[
/// Pixel { r: 2, g: 3, b: 4, a: 5 },
/// Pixel { r: 6, g: 7, b: 8, a: 9 },
/// ]);
/// ```
#[inline]
fn slice_from_suffix(bytes: &[u8], count: usize) -> Option<(&[u8], &[Self])>
where
Self: Sized,
{
Ref::<_, [Self]>::new_slice_from_suffix(bytes, count).map(|(b, r)| (b, r.into_slice()))
}
/// Interprets the given `bytes` as a `&mut [Self]` without copying.
///
/// If `bytes.len() % size_of::<T>() != 0` or `bytes` is not aligned to
/// `align_of::<T>()`, this returns `None`.
///
/// If you need to convert a specific number of slice elements, see
/// [`mut_slice_from_prefix`](FromBytes::mut_slice_from_prefix) or
/// [`mut_slice_from_suffix`](FromBytes::mut_slice_from_suffix).
///
/// # Panics
///
/// If `T` is a zero-sized type.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// # #[derive(Debug, PartialEq, Eq)]
/// #[derive(AsBytes, FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct Pixel {
/// r: u8,
/// g: u8,
/// b: u8,
/// a: u8,
/// }
///
/// // These bytes encode two `Pixel`s.
/// let bytes = &mut [0, 1, 2, 3, 4, 5, 6, 7][..];
///
/// let pixels = Pixel::mut_slice_from(bytes).unwrap();
///
/// assert_eq!(pixels, &[
/// Pixel { r: 0, g: 1, b: 2, a: 3 },
/// Pixel { r: 4, g: 5, b: 6, a: 7 },
/// ]);
///
/// pixels[1] = Pixel { r: 0, g: 0, b: 0, a: 0 };
///
/// assert_eq!(bytes, [0, 1, 2, 3, 0, 0, 0, 0]);
/// ```
#[inline]
fn mut_slice_from(bytes: &mut [u8]) -> Option<&mut [Self]>
where
Self: Sized + AsBytes,
{
Ref::<_, [Self]>::new_slice(bytes).map(|r| r.into_mut_slice())
}
/// Interprets the prefix of the given `bytes` as a `&mut [Self]` with length
/// equal to `count` without copying.
///
/// This method verifies that `bytes.len() >= size_of::<T>() * count`
/// and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// first `size_of::<T>() * count` bytes from `bytes` to construct a
/// `&[Self]`, and returns the remaining bytes to the caller. It also
/// ensures that `sizeof::<T>() * count` does not overflow a `usize`.
/// If any of the length, alignment, or overflow checks fail, it returns
/// `None`.
///
/// # Panics
///
/// If `T` is a zero-sized type.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// # #[derive(Debug, PartialEq, Eq)]
/// #[derive(AsBytes, FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct Pixel {
/// r: u8,
/// g: u8,
/// b: u8,
/// a: u8,
/// }
///
/// // These are more bytes than are needed to encode two `Pixel`s.
/// let bytes = &mut [0, 1, 2, 3, 4, 5, 6, 7, 8, 9][..];
///
/// let (pixels, rest) = Pixel::mut_slice_from_prefix(bytes, 2).unwrap();
///
/// assert_eq!(pixels, &[
/// Pixel { r: 0, g: 1, b: 2, a: 3 },
/// Pixel { r: 4, g: 5, b: 6, a: 7 },
/// ]);
///
/// assert_eq!(rest, &[8, 9]);
///
/// pixels[1] = Pixel { r: 0, g: 0, b: 0, a: 0 };
///
/// assert_eq!(bytes, [0, 1, 2, 3, 0, 0, 0, 0, 8, 9]);
/// ```
#[inline]
fn mut_slice_from_prefix(bytes: &mut [u8], count: usize) -> Option<(&mut [Self], &mut [u8])>
where
Self: Sized + AsBytes,
{
Ref::<_, [Self]>::new_slice_from_prefix(bytes, count).map(|(r, b)| (r.into_mut_slice(), b))
}
/// Interprets the suffix of the given `bytes` as a `&mut [Self]` with length
/// equal to `count` without copying.
///
/// This method verifies that `bytes.len() >= size_of::<T>() * count`
/// and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// last `size_of::<T>() * count` bytes from `bytes` to construct a
/// `&[Self]`, and returns the preceding bytes to the caller. It also
/// ensures that `sizeof::<T>() * count` does not overflow a `usize`.
/// If any of the length, alignment, or overflow checks fail, it returns
/// `None`.
///
/// # Panics
///
/// If `T` is a zero-sized type.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// # #[derive(Debug, PartialEq, Eq)]
/// #[derive(AsBytes, FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct Pixel {
/// r: u8,
/// g: u8,
/// b: u8,
/// a: u8,
/// }
///
/// // These are more bytes than are needed to encode two `Pixel`s.
/// let bytes = &mut [0, 1, 2, 3, 4, 5, 6, 7, 8, 9][..];
///
/// let (rest, pixels) = Pixel::mut_slice_from_suffix(bytes, 2).unwrap();
///
/// assert_eq!(rest, &[0, 1]);
///
/// assert_eq!(pixels, &[
/// Pixel { r: 2, g: 3, b: 4, a: 5 },
/// Pixel { r: 6, g: 7, b: 8, a: 9 },
/// ]);
///
/// pixels[1] = Pixel { r: 0, g: 0, b: 0, a: 0 };
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 0, 0, 0, 0]);
/// ```
#[inline]
fn mut_slice_from_suffix(bytes: &mut [u8], count: usize) -> Option<(&mut [u8], &mut [Self])>
where
Self: Sized + AsBytes,
{
Ref::<_, [Self]>::new_slice_from_suffix(bytes, count).map(|(b, r)| (b, r.into_mut_slice()))
}
/// Reads a copy of `Self` from `bytes`.
///
/// If `bytes.len() != size_of::<Self>()`, `read_from` returns `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// // These bytes encode a `PacketHeader`.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7].as_slice();
///
/// let header = PacketHeader::read_from(bytes).unwrap();
///
/// assert_eq!(header.src_port, [0, 1]);
/// assert_eq!(header.dst_port, [2, 3]);
/// assert_eq!(header.length, [4, 5]);
/// assert_eq!(header.checksum, [6, 7]);
/// ```
#[inline]
fn read_from(bytes: &[u8]) -> Option<Self>
where
Self: Sized,
{
Ref::<_, Unalign<Self>>::new_unaligned(bytes).map(|r| r.read().into_inner())
}
/// Reads a copy of `Self` from the prefix of `bytes`.
///
/// `read_from_prefix` reads a `Self` from the first `size_of::<Self>()`
/// bytes of `bytes`. If `bytes.len() < size_of::<Self>()`, it returns
/// `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// // These are more bytes than are needed to encode a `PacketHeader`.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].as_slice();
///
/// let header = PacketHeader::read_from_prefix(bytes).unwrap();
///
/// assert_eq!(header.src_port, [0, 1]);
/// assert_eq!(header.dst_port, [2, 3]);
/// assert_eq!(header.length, [4, 5]);
/// assert_eq!(header.checksum, [6, 7]);
/// ```
#[inline]
fn read_from_prefix(bytes: &[u8]) -> Option<Self>
where
Self: Sized,
{
Ref::<_, Unalign<Self>>::new_unaligned_from_prefix(bytes)
.map(|(r, _)| r.read().into_inner())
}
/// Reads a copy of `Self` from the suffix of `bytes`.
///
/// `read_from_suffix` reads a `Self` from the last `size_of::<Self>()`
/// bytes of `bytes`. If `bytes.len() < size_of::<Self>()`, it returns
/// `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::FromBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketTrailer {
/// frame_check_sequence: [u8; 4],
/// }
///
/// // These are more bytes than are needed to encode a `PacketTrailer`.
/// let bytes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].as_slice();
///
/// let trailer = PacketTrailer::read_from_suffix(bytes).unwrap();
///
/// assert_eq!(trailer.frame_check_sequence, [6, 7, 8, 9]);
/// ```
#[inline]
fn read_from_suffix(bytes: &[u8]) -> Option<Self>
where
Self: Sized,
{
Ref::<_, Unalign<Self>>::new_unaligned_from_suffix(bytes)
.map(|(_, r)| r.read().into_inner())
}
}
/// Analyzes whether a type is [`AsBytes`].
///
/// This derive analyzes, at compile time, whether the annotated type satisfies
/// the [safety conditions] of `AsBytes` and implements `AsBytes` if it is
/// sound to do so. This derive can be applied to structs, enums, and unions;
/// e.g.:
///
/// ```
/// # use zerocopy_derive::{AsBytes};
/// #[derive(AsBytes)]
/// #[repr(C)]
/// struct MyStruct {
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(AsBytes)]
/// #[repr(u8)]
/// enum MyEnum {
/// # Variant,
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(AsBytes)]
/// #[repr(C)]
/// union MyUnion {
/// # variant: u8,
/// # /*
/// ...
/// # */
/// }
/// ```
///
/// [safety conditions]: trait@AsBytes#safety
///
/// # Error Messages
///
/// Due to the way that the custom derive for `AsBytes` is implemented, you may
/// get an error like this:
///
/// ```text
/// error[E0277]: the trait bound `HasPadding<Foo, true>: ShouldBe<false>` is not satisfied
/// --> lib.rs:23:10
/// |
/// 1 | #[derive(AsBytes)]
/// | ^^^^^^^ the trait `ShouldBe<false>` is not implemented for `HasPadding<Foo, true>`
/// |
/// = help: the trait `ShouldBe<VALUE>` is implemented for `HasPadding<T, VALUE>`
/// ```
///
/// This error indicates that the type being annotated has padding bytes, which
/// is illegal for `AsBytes` types. Consider reducing the alignment of some
/// fields by using types in the [`byteorder`] module, adding explicit struct
/// fields where those padding bytes would be, or using `#[repr(packed)]`. See
/// the Rust Reference's page on [type layout] for more information
/// about type layout and padding.
///
/// [type layout]: https://doc.rust-lang.org/reference/type-layout.html
///
/// # Analysis
///
/// *This section describes, roughly, the analysis performed by this derive to
/// determine whether it is sound to implement `AsBytes` for a given type.
/// Unless you are modifying the implementation of this derive, or attempting to
/// manually implement `AsBytes` for a type yourself, you don't need to read
/// this section.*
///
/// If a type has the following properties, then this derive can implement
/// `AsBytes` for that type:
///
/// - If the type is a struct:
/// - It must have a defined representation (`repr(C)`, `repr(transparent)`,
/// or `repr(packed)`).
/// - All of its fields must be `AsBytes`.
/// - Its layout must have no padding. This is always true for
/// `repr(transparent)` and `repr(packed)`. For `repr(C)`, see the layout
/// algorithm described in the [Rust Reference].
/// - If the type is an enum:
/// - It must be a C-like enum (meaning that all variants have no fields).
/// - It must have a defined representation (`repr`s `C`, `u8`, `u16`, `u32`,
/// `u64`, `usize`, `i8`, `i16`, `i32`, `i64`, or `isize`).
/// - The type must not contain any [`UnsafeCell`]s (this is required in order
/// for it to be sound to construct a `&[u8]` and a `&T` to the same region of
/// memory). The type may contain references or pointers to `UnsafeCell`s so
/// long as those values can themselves be initialized from zeroes (`AsBytes`
/// is not currently implemented for, e.g., `Option<&UnsafeCell<_>>`, but it
/// could be one day).
///
/// [`UnsafeCell`]: core::cell::UnsafeCell
///
/// This analysis is subject to change. Unsafe code may *only* rely on the
/// documented [safety conditions] of `FromBytes`, and must *not* rely on the
/// implementation details of this derive.
///
/// [Rust Reference]: https://doc.rust-lang.org/reference/type-layout.html
#[cfg(any(feature = "derive", test))]
#[cfg_attr(doc_cfg, doc(cfg(feature = "derive")))]
pub use zerocopy_derive::AsBytes;
/// Types that can be viewed as an immutable slice of initialized bytes.
///
/// Any `AsBytes` type can be viewed as a slice of initialized bytes of the same
/// size. This is useful for efficiently serializing structured data as raw
/// bytes.
///
/// # Implementation
///
/// **Do not implement this trait yourself!** Instead, use
/// [`#[derive(AsBytes)]`][derive] (requires the `derive` Cargo feature); e.g.:
///
/// ```
/// # use zerocopy_derive::AsBytes;
/// #[derive(AsBytes)]
/// #[repr(C)]
/// struct MyStruct {
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(AsBytes)]
/// #[repr(u8)]
/// enum MyEnum {
/// # Variant0,
/// # /*
/// ...
/// # */
/// }
///
/// #[derive(AsBytes)]
/// #[repr(C)]
/// union MyUnion {
/// # variant: u8,
/// # /*
/// ...
/// # */
/// }
/// ```
///
/// This derive performs a sophisticated, compile-time safety analysis to
/// determine whether a type is `AsBytes`. See the [derive
/// documentation][derive] for guidance on how to interpret error messages
/// produced by the derive's analysis.
///
/// # Safety
///
/// *This section describes what is required in order for `T: AsBytes`, and
/// what unsafe code may assume of such types. If you don't plan on implementing
/// `AsBytes` manually, and you don't plan on writing unsafe code that
/// operates on `AsBytes` types, then you don't need to read this section.*
///
/// If `T: AsBytes`, then unsafe code may assume that:
/// - It is sound to treat any `t: T` as an immutable `[u8]` of length
/// `size_of_val(t)`.
/// - Given `t: &T`, it is sound to construct a `b: &[u8]` where `b.len() ==
/// size_of_val(t)` at the same address as `t`, and it is sound for both `b`
/// and `t` to be live at the same time.
///
/// If a type is marked as `AsBytes` which violates this contract, it may cause
/// undefined behavior.
///
/// `#[derive(AsBytes)]` only permits [types which satisfy these
/// requirements][derive-analysis].
///
#[cfg_attr(
feature = "derive",
doc = "[derive]: zerocopy_derive::AsBytes",
doc = "[derive-analysis]: zerocopy_derive::AsBytes#analysis"
)]
#[cfg_attr(
not(feature = "derive"),
doc = concat!("[derive]: https://docs.rs/zerocopy/", env!("CARGO_PKG_VERSION"), "/zerocopy/derive.AsBytes.html"),
doc = concat!("[derive-analysis]: https://docs.rs/zerocopy/", env!("CARGO_PKG_VERSION"), "/zerocopy/derive.AsBytes.html#analysis"),
)]
pub unsafe trait AsBytes {
// The `Self: Sized` bound makes it so that this function doesn't prevent
// `AsBytes` from being object safe. Note that other `AsBytes` methods
// prevent object safety, but those provide a benefit in exchange for object
// safety. If at some point we remove those methods, change their type
// signatures, or move them out of this trait so that `AsBytes` is object
// safe again, it's important that this function not prevent object safety.
#[doc(hidden)]
fn only_derive_is_allowed_to_implement_this_trait()
where
Self: Sized;
/// Gets the bytes of this value.
///
/// `as_bytes` provides access to the bytes of this value as an immutable
/// byte slice.
///
/// # Examples
///
/// ```
/// use zerocopy::AsBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(AsBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// let header = PacketHeader {
/// src_port: [0, 1],
/// dst_port: [2, 3],
/// length: [4, 5],
/// checksum: [6, 7],
/// };
///
/// let bytes = header.as_bytes();
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 6, 7]);
/// ```
#[inline(always)]
fn as_bytes(&self) -> &[u8] {
// Note that this method does not have a `Self: Sized` bound;
// `size_of_val` works for unsized values too.
let len = mem::size_of_val(self);
let slf: *const Self = self;
// SAFETY:
// - `slf.cast::<u8>()` is valid for reads for `len *
// mem::size_of::<u8>()` many bytes because...
// - `slf` is the same pointer as `self`, and `self` is a reference
// which points to an object whose size is `len`. Thus...
// - The entire region of `len` bytes starting at `slf` is contained
// within a single allocation.
// - `slf` is non-null.
// - `slf` is trivially aligned to `align_of::<u8>() == 1`.
// - `Self: AsBytes` ensures that all of the bytes of `slf` are
// initialized.
// - Since `slf` is derived from `self`, and `self` is an immutable
// reference, the only other references to this memory region that
// could exist are other immutable references, and those don't allow
// mutation. `AsBytes` prohibits types which contain `UnsafeCell`s,
// which are the only types for which this rule wouldn't be sufficient.
// - The total size of the resulting slice is no larger than
// `isize::MAX` because no allocation produced by safe code can be
// larger than `isize::MAX`.
//
// TODO(#429): Add references to docs and quotes.
unsafe { slice::from_raw_parts(slf.cast::<u8>(), len) }
}
/// Gets the bytes of this value mutably.
///
/// `as_bytes_mut` provides access to the bytes of this value as a mutable
/// byte slice.
///
/// # Examples
///
/// ```
/// use zerocopy::AsBytes;
/// # use zerocopy_derive::*;
///
/// # #[derive(Eq, PartialEq, Debug)]
/// #[derive(AsBytes, FromZeroes, FromBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// let mut header = PacketHeader {
/// src_port: [0, 1],
/// dst_port: [2, 3],
/// length: [4, 5],
/// checksum: [6, 7],
/// };
///
/// let bytes = header.as_bytes_mut();
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 6, 7]);
///
/// bytes.reverse();
///
/// assert_eq!(header, PacketHeader {
/// src_port: [7, 6],
/// dst_port: [5, 4],
/// length: [3, 2],
/// checksum: [1, 0],
/// });
/// ```
#[inline(always)]
fn as_bytes_mut(&mut self) -> &mut [u8]
where
Self: FromBytes,
{
// Note that this method does not have a `Self: Sized` bound;
// `size_of_val` works for unsized values too.
let len = mem::size_of_val(self);
let slf: *mut Self = self;
// SAFETY:
// - `slf.cast::<u8>()` is valid for reads and writes for `len *
// mem::size_of::<u8>()` many bytes because...
// - `slf` is the same pointer as `self`, and `self` is a reference
// which points to an object whose size is `len`. Thus...
// - The entire region of `len` bytes starting at `slf` is contained
// within a single allocation.
// - `slf` is non-null.
// - `slf` is trivially aligned to `align_of::<u8>() == 1`.
// - `Self: AsBytes` ensures that all of the bytes of `slf` are
// initialized.
// - `Self: FromBytes` ensures that no write to this memory region
// could result in it containing an invalid `Self`.
// - Since `slf` is derived from `self`, and `self` is a mutable
// reference, no other references to this memory region can exist.
// - The total size of the resulting slice is no larger than
// `isize::MAX` because no allocation produced by safe code can be
// larger than `isize::MAX`.
//
// TODO(#429): Add references to docs and quotes.
unsafe { slice::from_raw_parts_mut(slf.cast::<u8>(), len) }
}
/// Writes a copy of `self` to `bytes`.
///
/// If `bytes.len() != size_of_val(self)`, `write_to` returns `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::AsBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(AsBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// let header = PacketHeader {
/// src_port: [0, 1],
/// dst_port: [2, 3],
/// length: [4, 5],
/// checksum: [6, 7],
/// };
///
/// let mut bytes = [0, 0, 0, 0, 0, 0, 0, 0];
///
/// header.write_to(&mut bytes[..]);
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 6, 7]);
/// ```
///
/// If too many or too few target bytes are provided, `write_to` returns
/// `None` and leaves the target bytes unmodified:
///
/// ```
/// # use zerocopy::AsBytes;
/// # let header = u128::MAX;
/// let mut excessive_bytes = &mut [0u8; 128][..];
///
/// let write_result = header.write_to(excessive_bytes);
///
/// assert!(write_result.is_none());
/// assert_eq!(excessive_bytes, [0u8; 128]);
/// ```
#[inline]
fn write_to(&self, bytes: &mut [u8]) -> Option<()> {
if bytes.len() != mem::size_of_val(self) {
return None;
}
bytes.copy_from_slice(self.as_bytes());
Some(())
}
/// Writes a copy of `self` to the prefix of `bytes`.
///
/// `write_to_prefix` writes `self` to the first `size_of_val(self)` bytes
/// of `bytes`. If `bytes.len() < size_of_val(self)`, it returns `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::AsBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(AsBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// let header = PacketHeader {
/// src_port: [0, 1],
/// dst_port: [2, 3],
/// length: [4, 5],
/// checksum: [6, 7],
/// };
///
/// let mut bytes = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
///
/// header.write_to_prefix(&mut bytes[..]);
///
/// assert_eq!(bytes, [0, 1, 2, 3, 4, 5, 6, 7, 0, 0]);
/// ```
///
/// If insufficient target bytes are provided, `write_to_prefix` returns
/// `None` and leaves the target bytes unmodified:
///
/// ```
/// # use zerocopy::AsBytes;
/// # let header = u128::MAX;
/// let mut insufficent_bytes = &mut [0, 0][..];
///
/// let write_result = header.write_to_suffix(insufficent_bytes);
///
/// assert!(write_result.is_none());
/// assert_eq!(insufficent_bytes, [0, 0]);
/// ```
#[inline]
fn write_to_prefix(&self, bytes: &mut [u8]) -> Option<()> {
let size = mem::size_of_val(self);
bytes.get_mut(..size)?.copy_from_slice(self.as_bytes());
Some(())
}
/// Writes a copy of `self` to the suffix of `bytes`.
///
/// `write_to_suffix` writes `self` to the last `size_of_val(self)` bytes of
/// `bytes`. If `bytes.len() < size_of_val(self)`, it returns `None`.
///
/// # Examples
///
/// ```
/// use zerocopy::AsBytes;
/// # use zerocopy_derive::*;
///
/// #[derive(AsBytes)]
/// #[repr(C)]
/// struct PacketHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// let header = PacketHeader {
/// src_port: [0, 1],
/// dst_port: [2, 3],
/// length: [4, 5],
/// checksum: [6, 7],
/// };
///
/// let mut bytes = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
///
/// header.write_to_suffix(&mut bytes[..]);
///
/// assert_eq!(bytes, [0, 0, 0, 1, 2, 3, 4, 5, 6, 7]);
///
/// let mut insufficent_bytes = &mut [0, 0][..];
///
/// let write_result = header.write_to_suffix(insufficent_bytes);
///
/// assert!(write_result.is_none());
/// assert_eq!(insufficent_bytes, [0, 0]);
/// ```
///
/// If insufficient target bytes are provided, `write_to_suffix` returns
/// `None` and leaves the target bytes unmodified:
///
/// ```
/// # use zerocopy::AsBytes;
/// # let header = u128::MAX;
/// let mut insufficent_bytes = &mut [0, 0][..];
///
/// let write_result = header.write_to_suffix(insufficent_bytes);
///
/// assert!(write_result.is_none());
/// assert_eq!(insufficent_bytes, [0, 0]);
/// ```
#[inline]
fn write_to_suffix(&self, bytes: &mut [u8]) -> Option<()> {
let start = bytes.len().checked_sub(mem::size_of_val(self))?;
bytes
.get_mut(start..)
.expect("`start` should be in-bounds of `bytes`")
.copy_from_slice(self.as_bytes());
Some(())
}
}
/// Types with no alignment requirement.
///
/// WARNING: Do not implement this trait yourself! Instead, use
/// `#[derive(Unaligned)]` (requires the `derive` Cargo feature).
///
/// If `T: Unaligned`, then `align_of::<T>() == 1`.
///
/// # Safety
///
/// *This section describes what is required in order for `T: Unaligned`, and
/// what unsafe code may assume of such types. `#[derive(Unaligned)]` only
/// permits types which satisfy these requirements. If you don't plan on
/// implementing `Unaligned` manually, and you don't plan on writing unsafe code
/// that operates on `Unaligned` types, then you don't need to read this
/// section.*
///
/// If `T: Unaligned`, then unsafe code may assume that it is sound to produce a
/// reference to `T` at any memory location regardless of alignment. If a type
/// is marked as `Unaligned` which violates this contract, it may cause
/// undefined behavior.
pub unsafe trait Unaligned {
// The `Self: Sized` bound makes it so that `Unaligned` is still object
// safe.
#[doc(hidden)]
fn only_derive_is_allowed_to_implement_this_trait()
where
Self: Sized;
}
safety_comment! {
/// SAFETY:
/// Per the reference [1], "the unit tuple (`()`) ... is guaranteed as a
/// zero-sized type to have a size of 0 and an alignment of 1."
/// - `TryFromBytes` (with no validator), `FromZeroes`, `FromBytes`: There
/// is only one possible sequence of 0 bytes, and `()` is inhabited.
/// - `AsBytes`: Since `()` has size 0, it contains no padding bytes.
/// - `Unaligned`: `()` has alignment 1.
///
/// [1] https://doc.rust-lang.org/reference/type-layout.html#tuple-layout
unsafe_impl!((): TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_unaligned!(());
}
safety_comment! {
/// SAFETY:
/// - `TryFromBytes` (with no validator), `FromZeroes`, `FromBytes`: all bit
/// patterns are valid for numeric types [1]
/// - `AsBytes`: numeric types have no padding bytes [1]
/// - `Unaligned` (`u8` and `i8` only): The reference [2] specifies the size
/// of `u8` and `i8` as 1 byte. We also know that:
/// - Alignment is >= 1 [3]
/// - Size is an integer multiple of alignment [4]
/// - The only value >= 1 for which 1 is an integer multiple is 1
/// Therefore, the only possible alignment for `u8` and `i8` is 1.
///
/// [1] Per https://doc.rust-lang.org/beta/reference/types/numeric.html#bit-validity:
///
/// For every numeric type, `T`, the bit validity of `T` is equivalent to
/// the bit validity of `[u8; size_of::<T>()]`. An uninitialized byte is
/// not a valid `u8`.
///
/// TODO(https://github.com/rust-lang/reference/pull/1392): Once this text
/// is available on the Stable docs, cite those instead.
///
/// [2] https://doc.rust-lang.org/reference/type-layout.html#primitive-data-layout
///
/// [3] Per https://doc.rust-lang.org/reference/type-layout.html#size-and-alignment:
///
/// Alignment is measured in bytes, and must be at least 1.
///
/// [4] Per https://doc.rust-lang.org/reference/type-layout.html#size-and-alignment:
///
/// The size of a value is always a multiple of its alignment.
///
/// TODO(#278): Once we've updated the trait docs to refer to `u8`s rather
/// than bits or bytes, update this comment, especially the reference to
/// [1].
unsafe_impl!(u8: TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
unsafe_impl!(i8: TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_unaligned!(u8, i8);
unsafe_impl!(u16: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(i16: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(u32: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(i32: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(u64: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(i64: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(u128: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(i128: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(usize: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(isize: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(f32: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(f64: TryFromBytes, FromZeroes, FromBytes, AsBytes);
}
safety_comment! {
/// SAFETY:
/// - `FromZeroes`: Valid since "[t]he value false has the bit pattern
/// 0x00" [1].
/// - `AsBytes`: Since "the boolean type has a size and alignment of 1 each"
/// and "The value false has the bit pattern 0x00 and the value true has
/// the bit pattern 0x01" [1]. Thus, the only byte of the bool is always
/// initialized.
/// - `Unaligned`: Per the reference [1], "[a]n object with the boolean type
/// has a size and alignment of 1 each."
///
/// [1] https://doc.rust-lang.org/reference/types/boolean.html
unsafe_impl!(bool: FromZeroes, AsBytes, Unaligned);
assert_unaligned!(bool);
/// SAFETY:
/// - The safety requirements for `unsafe_impl!` with an `is_bit_valid`
/// closure:
/// - Given `t: *mut bool` and `let r = *mut u8`, `r` refers to an object
/// of the same size as that referred to by `t`. This is true because
/// `bool` and `u8` have the same size (1 byte) [1].
/// - Since the closure takes a `&u8` argument, given a `Ptr<'a, bool>`
/// which satisfies the preconditions of
/// `TryFromBytes::<bool>::is_bit_valid`, it must be guaranteed that the
/// memory referenced by that `Ptr` always contains a valid `u8`. Since
/// `bool`'s single byte is always initialized, `is_bit_valid`'s
/// precondition requires that the same is true of its argument. Since
/// `u8`'s only bit validity invariant is that its single byte must be
/// initialized, this memory is guaranteed to contain a valid `u8`.
/// - The alignment of `bool` is equal to the alignment of `u8`. [1] [2]
/// - The impl must only return `true` for its argument if the original
/// `Ptr<bool>` refers to a valid `bool`. We only return true if the
/// `u8` value is 0 or 1, and both of these are valid values for `bool`.
/// [3]
///
/// [1] Per https://doc.rust-lang.org/reference/type-layout.html#primitive-data-layout:
///
/// The size of most primitives is given in this table.
///
/// | Type | `size_of::<Type>() ` |
/// |-----------|----------------------|
/// | `bool` | 1 |
/// | `u8`/`i8` | 1 |
///
/// [2] Per https://doc.rust-lang.org/reference/type-layout.html#size-and-alignment:
///
/// The size of a value is always a multiple of its alignment.
///
/// [3] Per https://doc.rust-lang.org/reference/types/boolean.html:
///
/// The value false has the bit pattern 0x00 and the value true has the
/// bit pattern 0x01.
unsafe_impl!(bool: TryFromBytes; |byte: &u8| *byte < 2);
}
safety_comment! {
/// SAFETY:
/// - `FromZeroes`: Per reference [1], "[a] value of type char is a Unicode
/// scalar value (i.e. a code point that is not a surrogate), represented
/// as a 32-bit unsigned word in the 0x0000 to 0xD7FF or 0xE000 to
/// 0x10FFFF range" which contains 0x0000.
/// - `AsBytes`: `char` is per reference [1] "represented as a 32-bit
/// unsigned word" (`u32`) which is `AsBytes`. Note that unlike `u32`, not
/// all bit patterns are valid for `char`.
///
/// [1] https://doc.rust-lang.org/reference/types/textual.html
unsafe_impl!(char: FromZeroes, AsBytes);
/// SAFETY:
/// - The safety requirements for `unsafe_impl!` with an `is_bit_valid`
/// closure:
/// - Given `t: *mut char` and `let r = *mut u32`, `r` refers to an object
/// of the same size as that referred to by `t`. This is true because
/// `char` and `u32` have the same size [1].
/// - Since the closure takes a `&u32` argument, given a `Ptr<'a, char>`
/// which satisfies the preconditions of
/// `TryFromBytes::<char>::is_bit_valid`, it must be guaranteed that the
/// memory referenced by that `Ptr` always contains a valid `u32`. Since
/// `char`'s bytes are always initialized [2], `is_bit_valid`'s
/// precondition requires that the same is true of its argument. Since
/// `u32`'s only bit validity invariant is that its bytes must be
/// initialized, this memory is guaranteed to contain a valid `u32`.
/// - The alignment of `char` is equal to the alignment of `u32`. [1]
/// - The impl must only return `true` for its argument if the original
/// `Ptr<char>` refers to a valid `char`. `char::from_u32` guarantees
/// that it returns `None` if its input is not a valid `char`. [3]
///
/// [1] Per https://doc.rust-lang.org/nightly/reference/types/textual.html#layout-and-bit-validity:
///
/// `char` is guaranteed to have the same size and alignment as `u32` on
/// all platforms.
///
/// [2] Per https://doc.rust-lang.org/core/primitive.char.html#method.from_u32:
///
/// Every byte of a `char` is guaranteed to be initialized.
///
/// [3] Per https://doc.rust-lang.org/core/primitive.char.html#method.from_u32:
///
/// `from_u32()` will return `None` if the input is not a valid value for
/// a `char`.
unsafe_impl!(char: TryFromBytes; |candidate: &u32| char::from_u32(*candidate).is_some());
}
safety_comment! {
/// SAFETY:
/// - `FromZeroes`, `AsBytes`, `Unaligned`: Per the reference [1], `str`
/// has the same layout as `[u8]`, and `[u8]` is `FromZeroes`, `AsBytes`,
/// and `Unaligned`.
///
/// Note that we don't `assert_unaligned!(str)` because `assert_unaligned!`
/// uses `align_of`, which only works for `Sized` types.
///
/// TODO(#429): Add quotes from documentation.
///
/// [1] https://doc.rust-lang.org/reference/type-layout.html#str-layout
unsafe_impl!(str: FromZeroes, AsBytes, Unaligned);
/// SAFETY:
/// - The safety requirements for `unsafe_impl!` with an `is_bit_valid`
/// closure:
/// - Given `t: *mut str` and `let r = *mut [u8]`, `r` refers to an object
/// of the same size as that referred to by `t`. This is true because
/// `str` and `[u8]` have the same representation. [1]
/// - Since the closure takes a `&[u8]` argument, given a `Ptr<'a, str>`
/// which satisfies the preconditions of
/// `TryFromBytes::<str>::is_bit_valid`, it must be guaranteed that the
/// memory referenced by that `Ptr` always contains a valid `[u8]`.
/// Since `str`'s bytes are always initialized [1], `is_bit_valid`'s
/// precondition requires that the same is true of its argument. Since
/// `[u8]`'s only bit validity invariant is that its bytes must be
/// initialized, this memory is guaranteed to contain a valid `[u8]`.
/// - The alignment of `str` is equal to the alignment of `[u8]`. [1]
/// - The impl must only return `true` for its argument if the original
/// `Ptr<str>` refers to a valid `str`. `str::from_utf8` guarantees that
/// it returns `Err` if its input is not a valid `str`. [2]
///
/// [1] Per https://doc.rust-lang.org/reference/types/textual.html:
///
/// A value of type `str` is represented the same was as `[u8]`.
///
/// [2] Per https://doc.rust-lang.org/core/str/fn.from_utf8.html#errors:
///
/// Returns `Err` if the slice is not UTF-8.
unsafe_impl!(str: TryFromBytes; |candidate: &[u8]| core::str::from_utf8(candidate).is_ok());
}
safety_comment! {
// `NonZeroXxx` is `AsBytes`, but not `FromZeroes` or `FromBytes`.
//
/// SAFETY:
/// - `AsBytes`: `NonZeroXxx` has the same layout as its associated
/// primitive. Since it is the same size, this guarantees it has no
/// padding - integers have no padding, and there's no room for padding
/// if it can represent all of the same values except 0.
/// - `Unaligned`: `NonZeroU8` and `NonZeroI8` document that
/// `Option<NonZeroU8>` and `Option<NonZeroI8>` both have size 1. [1] [2]
/// This is worded in a way that makes it unclear whether it's meant as a
/// guarantee, but given the purpose of those types, it's virtually
/// unthinkable that that would ever change. `Option` cannot be smaller
/// than its contained type, which implies that, and `NonZeroX8` are of
/// size 1 or 0. `NonZeroX8` can represent multiple states, so they cannot
/// be 0 bytes, which means that they must be 1 byte. The only valid
/// alignment for a 1-byte type is 1.
///
/// TODO(#429): Add quotes from documentation.
///
/// [1] https://doc.rust-lang.org/stable/std/num/struct.NonZeroU8.html
/// [2] https://doc.rust-lang.org/stable/std/num/struct.NonZeroI8.html
/// TODO(https://github.com/rust-lang/rust/pull/104082): Cite documentation
/// that layout is the same as primitive layout.
unsafe_impl!(NonZeroU8: AsBytes, Unaligned);
unsafe_impl!(NonZeroI8: AsBytes, Unaligned);
assert_unaligned!(NonZeroU8, NonZeroI8);
unsafe_impl!(NonZeroU16: AsBytes);
unsafe_impl!(NonZeroI16: AsBytes);
unsafe_impl!(NonZeroU32: AsBytes);
unsafe_impl!(NonZeroI32: AsBytes);
unsafe_impl!(NonZeroU64: AsBytes);
unsafe_impl!(NonZeroI64: AsBytes);
unsafe_impl!(NonZeroU128: AsBytes);
unsafe_impl!(NonZeroI128: AsBytes);
unsafe_impl!(NonZeroUsize: AsBytes);
unsafe_impl!(NonZeroIsize: AsBytes);
/// SAFETY:
/// - The safety requirements for `unsafe_impl!` with an `is_bit_valid`
/// closure:
/// - Given `t: *mut NonZeroXxx` and `let r = *mut xxx`, `r` refers to an
/// object of the same size as that referred to by `t`. This is true
/// because `NonZeroXxx` and `xxx` have the same size. [1]
/// - Since the closure takes a `&xxx` argument, given a `Ptr<'a,
/// NonZeroXxx>` which satisfies the preconditions of
/// `TryFromBytes::<NonZeroXxx>::is_bit_valid`, it must be guaranteed
/// that the memory referenced by that `Ptr` always contains a valid
/// `xxx`. Since `NonZeroXxx`'s bytes are always initialized [1],
/// `is_bit_valid`'s precondition requires that the same is true of its
/// argument. Since `xxx`'s only bit validity invariant is that its
/// bytes must be initialized, this memory is guaranteed to contain a
/// valid `xxx`.
/// - The alignment of `NonZeroXxx` is equal to the alignment of `xxx`.
/// [1]
/// - The impl must only return `true` for its argument if the original
/// `Ptr<NonZeroXxx>` refers to a valid `NonZeroXxx`. The only `xxx`
/// which is not also a valid `NonZeroXxx` is 0. [1]
///
/// [1] Per https://doc.rust-lang.org/core/num/struct.NonZeroU16.html:
///
/// `NonZeroU16` is guaranteed to have the same layout and bit validity as
/// `u16` with the exception that `0` is not a valid instance.
unsafe_impl!(NonZeroU8: TryFromBytes; |n: &u8| *n != 0);
unsafe_impl!(NonZeroI8: TryFromBytes; |n: &i8| *n != 0);
unsafe_impl!(NonZeroU16: TryFromBytes; |n: &u16| *n != 0);
unsafe_impl!(NonZeroI16: TryFromBytes; |n: &i16| *n != 0);
unsafe_impl!(NonZeroU32: TryFromBytes; |n: &u32| *n != 0);
unsafe_impl!(NonZeroI32: TryFromBytes; |n: &i32| *n != 0);
unsafe_impl!(NonZeroU64: TryFromBytes; |n: &u64| *n != 0);
unsafe_impl!(NonZeroI64: TryFromBytes; |n: &i64| *n != 0);
unsafe_impl!(NonZeroU128: TryFromBytes; |n: &u128| *n != 0);
unsafe_impl!(NonZeroI128: TryFromBytes; |n: &i128| *n != 0);
unsafe_impl!(NonZeroUsize: TryFromBytes; |n: &usize| *n != 0);
unsafe_impl!(NonZeroIsize: TryFromBytes; |n: &isize| *n != 0);
}
safety_comment! {
/// SAFETY:
/// - `TryFromBytes` (with no validator), `FromZeroes`, `FromBytes`,
/// `AsBytes`: The Rust compiler reuses `0` value to represent `None`, so
/// `size_of::<Option<NonZeroXxx>>() == size_of::<xxx>()`; see
/// `NonZeroXxx` documentation.
/// - `Unaligned`: `NonZeroU8` and `NonZeroI8` document that
/// `Option<NonZeroU8>` and `Option<NonZeroI8>` both have size 1. [1] [2]
/// This is worded in a way that makes it unclear whether it's meant as a
/// guarantee, but given the purpose of those types, it's virtually
/// unthinkable that that would ever change. The only valid alignment for
/// a 1-byte type is 1.
///
/// TODO(#429): Add quotes from documentation.
///
/// [1] https://doc.rust-lang.org/stable/std/num/struct.NonZeroU8.html
/// [2] https://doc.rust-lang.org/stable/std/num/struct.NonZeroI8.html
///
/// TODO(https://github.com/rust-lang/rust/pull/104082): Cite documentation
/// for layout guarantees.
unsafe_impl!(Option<NonZeroU8>: TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
unsafe_impl!(Option<NonZeroI8>: TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_unaligned!(Option<NonZeroU8>, Option<NonZeroI8>);
unsafe_impl!(Option<NonZeroU16>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroI16>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroU32>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroI32>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroU64>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroI64>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroU128>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroI128>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroUsize>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
unsafe_impl!(Option<NonZeroIsize>: TryFromBytes, FromZeroes, FromBytes, AsBytes);
}
safety_comment! {
/// SAFETY:
/// The following types can be transmuted from `[0u8; size_of::<T>()]`. [1]
/// None of them contain `UnsafeCell`s, and so they all soundly implement
/// `FromZeroes`.
///
/// [1] Per
/// https://doc.rust-lang.org/nightly/core/option/index.html#representation:
///
/// Rust guarantees to optimize the following types `T` such that
/// [`Option<T>`] has the same size and alignment as `T`. In some of these
/// cases, Rust further guarantees that `transmute::<_, Option<T>>([0u8;
/// size_of::<T>()])` is sound and produces `Option::<T>::None`. These
/// cases are identified by the second column:
///
/// | `T` | `transmute::<_, Option<T>>([0u8; size_of::<T>()])` sound? |
/// |-----------------------|-----------------------------------------------------------|
/// | [`Box<U>`] | when `U: Sized` |
/// | `&U` | when `U: Sized` |
/// | `&mut U` | when `U: Sized` |
/// | [`ptr::NonNull<U>`] | when `U: Sized` |
/// | `fn`, `extern "C" fn` | always |
///
/// TODO(#429), TODO(https://github.com/rust-lang/rust/pull/115333): Cite
/// the Stable docs once they're available.
#[cfg(feature = "alloc")]
unsafe_impl!(
#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
T => FromZeroes for Option<Box<T>>
);
unsafe_impl!(T => FromZeroes for Option<&'_ T>);
unsafe_impl!(T => FromZeroes for Option<&'_ mut T>);
unsafe_impl!(T => FromZeroes for Option<NonNull<T>>);
unsafe_impl_for_power_set!(A, B, C, D, E, F, G, H, I, J, K, L -> M => FromZeroes for opt_fn!(...));
unsafe_impl_for_power_set!(A, B, C, D, E, F, G, H, I, J, K, L -> M => FromZeroes for opt_extern_c_fn!(...));
}
safety_comment! {
/// SAFETY:
/// Per reference [1]:
/// "For all T, the following are guaranteed:
/// size_of::<PhantomData<T>>() == 0
/// align_of::<PhantomData<T>>() == 1".
/// This gives:
/// - `TryFromBytes` (with no validator), `FromZeroes`, `FromBytes`: There
/// is only one possible sequence of 0 bytes, and `PhantomData` is
/// inhabited.
/// - `AsBytes`: Since `PhantomData` has size 0, it contains no padding
/// bytes.
/// - `Unaligned`: Per the preceding reference, `PhantomData` has alignment
/// 1.
///
/// [1] https://doc.rust-lang.org/std/marker/struct.PhantomData.html#layout-1
unsafe_impl!(T: ?Sized => TryFromBytes for PhantomData<T>);
unsafe_impl!(T: ?Sized => FromZeroes for PhantomData<T>);
unsafe_impl!(T: ?Sized => FromBytes for PhantomData<T>);
unsafe_impl!(T: ?Sized => AsBytes for PhantomData<T>);
unsafe_impl!(T: ?Sized => Unaligned for PhantomData<T>);
assert_unaligned!(PhantomData<()>, PhantomData<u8>, PhantomData<u64>);
}
safety_comment! {
/// SAFETY:
/// `Wrapping<T>` is guaranteed by its docs [1] to have the same layout and
/// bit validity as `T`. Also, `Wrapping<T>` is `#[repr(transparent)]`, and
/// has a single field, which is `pub`. Per the reference [2], this means
/// that the `#[repr(transparent)]` attribute is "considered part of the
/// public ABI".
///
/// - `TryFromBytes`: The safety requirements for `unsafe_impl!` with an
/// `is_bit_valid` closure:
/// - Given `t: *mut Wrapping<T>` and `let r = *mut T`, `r` refers to an
/// object of the same size as that referred to by `t`. This is true
/// because `Wrapping<T>` and `T` have the same layout
/// - The alignment of `Wrapping<T>` is equal to the alignment of `T`.
/// - The impl must only return `true` for its argument if the original
/// `Ptr<Wrapping<T>>` refers to a valid `Wrapping<T>`. Since
/// `Wrapping<T>` has the same bit validity as `T`, and since our impl
/// just calls `T::is_bit_valid`, our impl returns `true` exactly when
/// its argument contains a valid `Wrapping<T>`.
/// - `FromBytes`: Since `Wrapping<T>` has the same bit validity as `T`, if
/// `T: FromBytes`, then all initialized byte sequences are valid
/// instances of `Wrapping<T>`. Similarly, if `T: FromBytes`, then
/// `Wrapping<T>` doesn't contain any `UnsafeCell`s. Thus, `impl FromBytes
/// for Wrapping<T> where T: FromBytes` is a sound impl.
/// - `AsBytes`: Since `Wrapping<T>` has the same bit validity as `T`, if
/// `T: AsBytes`, then all valid instances of `Wrapping<T>` have all of
/// their bytes initialized. Similarly, if `T: AsBytes`, then
/// `Wrapping<T>` doesn't contain any `UnsafeCell`s. Thus, `impl AsBytes
/// for Wrapping<T> where T: AsBytes` is a valid impl.
/// - `Unaligned`: Since `Wrapping<T>` has the same layout as `T`,
/// `Wrapping<T>` has alignment 1 exactly when `T` does.
///
/// [1] Per https://doc.rust-lang.org/core/num/struct.NonZeroU16.html:
///
/// `NonZeroU16` is guaranteed to have the same layout and bit validity as
/// `u16` with the exception that `0` is not a valid instance.
///
/// TODO(#429): Add quotes from documentation.
///
/// [1] TODO(https://doc.rust-lang.org/nightly/core/num/struct.Wrapping.html#layout-1):
/// Reference this documentation once it's available on stable.
///
/// [2] https://doc.rust-lang.org/nomicon/other-reprs.html#reprtransparent
unsafe_impl!(T: TryFromBytes => TryFromBytes for Wrapping<T>; |candidate: Ptr<T>| {
// SAFETY:
// - Since `T` and `Wrapping<T>` have the same layout and bit validity
// and contain the same fields, `T` contains `UnsafeCell`s exactly
// where `Wrapping<T>` does. Thus, all memory and `UnsafeCell`
// preconditions of `T::is_bit_valid` hold exactly when the same
// preconditions for `Wrapping<T>::is_bit_valid` hold.
// - By the same token, since `candidate` is guaranteed to have its
// bytes initialized where there are always initialized bytes in
// `Wrapping<T>`, the same is true for `T`.
unsafe { T::is_bit_valid(candidate) }
});
unsafe_impl!(T: FromZeroes => FromZeroes for Wrapping<T>);
unsafe_impl!(T: FromBytes => FromBytes for Wrapping<T>);
unsafe_impl!(T: AsBytes => AsBytes for Wrapping<T>);
unsafe_impl!(T: Unaligned => Unaligned for Wrapping<T>);
assert_unaligned!(Wrapping<()>, Wrapping<u8>);
}
safety_comment! {
// `MaybeUninit<T>` is `FromZeroes` and `FromBytes`, but never `AsBytes`
// since it may contain uninitialized bytes.
//
/// SAFETY:
/// - `TryFromBytes` (with no validator), `FromZeroes`, `FromBytes`:
/// `MaybeUninit<T>` has no restrictions on its contents. Unfortunately,
/// in addition to bit validity, `TryFromBytes`, `FromZeroes` and
/// `FromBytes` also require that implementers contain no `UnsafeCell`s.
/// Thus, we require `T: Trait` in order to ensure that `T` - and thus
/// `MaybeUninit<T>` - contains to `UnsafeCell`s. Thus, requiring that `T`
/// implement each of these traits is sufficient.
/// - `Unaligned`: "MaybeUninit<T> is guaranteed to have the same size,
/// alignment, and ABI as T" [1]
///
/// [1] https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#layout-1
///
/// TODO(https://github.com/google/zerocopy/issues/251): If we split
/// `FromBytes` and `RefFromBytes`, or if we introduce a separate
/// `NoCell`/`Freeze` trait, we can relax the trait bounds for `FromZeroes`
/// and `FromBytes`.
unsafe_impl!(T: TryFromBytes => TryFromBytes for MaybeUninit<T>);
unsafe_impl!(T: FromZeroes => FromZeroes for MaybeUninit<T>);
unsafe_impl!(T: FromBytes => FromBytes for MaybeUninit<T>);
unsafe_impl!(T: Unaligned => Unaligned for MaybeUninit<T>);
assert_unaligned!(MaybeUninit<()>, MaybeUninit<u8>);
}
safety_comment! {
/// SAFETY:
/// `ManuallyDrop` has the same layout and bit validity as `T` [1], and
/// accessing the inner value is safe (meaning that it's unsound to leave
/// the inner value uninitialized while exposing the `ManuallyDrop` to safe
/// code).
/// - `FromZeroes`, `FromBytes`: Since it has the same layout as `T`, any
/// valid `T` is a valid `ManuallyDrop<T>`. If `T: FromZeroes`, a sequence
/// of zero bytes is a valid `T`, and thus a valid `ManuallyDrop<T>`. If
/// `T: FromBytes`, any sequence of bytes is a valid `T`, and thus a valid
/// `ManuallyDrop<T>`.
/// - `AsBytes`: Since it has the same layout as `T`, and since it's unsound
/// to let safe code access a `ManuallyDrop` whose inner value is
/// uninitialized, safe code can only ever access a `ManuallyDrop` whose
/// contents are a valid `T`. Since `T: AsBytes`, this means that safe
/// code can only ever access a `ManuallyDrop` with all initialized bytes.
/// - `Unaligned`: `ManuallyDrop` has the same layout (and thus alignment)
/// as `T`, and `T: Unaligned` guarantees that that alignment is 1.
///
/// `ManuallyDrop<T>` is guaranteed to have the same layout and bit
/// validity as `T`
///
/// [1] Per https://doc.rust-lang.org/nightly/core/mem/struct.ManuallyDrop.html:
///
/// TODO(#429):
/// - Add quotes from docs.
/// - Once [1] (added in
/// https://github.com/rust-lang/rust/pull/115522) is available on stable,
/// quote the stable docs instead of the nightly docs.
unsafe_impl!(T: ?Sized + FromZeroes => FromZeroes for ManuallyDrop<T>);
unsafe_impl!(T: ?Sized + FromBytes => FromBytes for ManuallyDrop<T>);
unsafe_impl!(T: ?Sized + AsBytes => AsBytes for ManuallyDrop<T>);
unsafe_impl!(T: ?Sized + Unaligned => Unaligned for ManuallyDrop<T>);
assert_unaligned!(ManuallyDrop<()>, ManuallyDrop<u8>);
}
safety_comment! {
/// SAFETY:
/// Per the reference [1]:
///
/// An array of `[T; N]` has a size of `size_of::<T>() * N` and the same
/// alignment of `T`. Arrays are laid out so that the zero-based `nth`
/// element of the array is offset from the start of the array by `n *
/// size_of::<T>()` bytes.
///
/// ...
///
/// Slices have the same layout as the section of the array they slice.
///
/// In other words, the layout of a `[T]` or `[T; N]` is a sequence of `T`s
/// laid out back-to-back with no bytes in between. Therefore, `[T]` or `[T;
/// N]` are `TryFromBytes`, `FromZeroes`, `FromBytes`, and `AsBytes` if `T`
/// is (respectively). Furthermore, since an array/slice has "the same
/// alignment of `T`", `[T]` and `[T; N]` are `Unaligned` if `T` is.
///
/// Note that we don't `assert_unaligned!` for slice types because
/// `assert_unaligned!` uses `align_of`, which only works for `Sized` types.
///
/// [1] https://doc.rust-lang.org/reference/type-layout.html#array-layout
unsafe_impl!(const N: usize, T: FromZeroes => FromZeroes for [T; N]);
unsafe_impl!(const N: usize, T: FromBytes => FromBytes for [T; N]);
unsafe_impl!(const N: usize, T: AsBytes => AsBytes for [T; N]);
unsafe_impl!(const N: usize, T: Unaligned => Unaligned for [T; N]);
assert_unaligned!([(); 0], [(); 1], [u8; 0], [u8; 1]);
unsafe_impl!(T: TryFromBytes => TryFromBytes for [T]; |c: Ptr<[T]>| {
// SAFETY: Assuming the preconditions of `is_bit_valid` are satisfied,
// so too will the postcondition: that, if `is_bit_valid(candidate)`
// returns true, `*candidate` contains a valid `Self`. Per the reference
// [1]:
//
// An array of `[T; N]` has a size of `size_of::<T>() * N` and the
// same alignment of `T`. Arrays are laid out so that the zero-based
// `nth` element of the array is offset from the start of the array by
// `n * size_of::<T>()` bytes.
//
// ...
//
// Slices have the same layout as the section of the array they slice.
//
// In other words, the layout of a `[T] is a sequence of `T`s laid out
// back-to-back with no bytes in between. If all elements in `candidate`
// are `is_bit_valid`, so too is `candidate`.
//
// Note that any of the below calls may panic, but it would still be
// sound even if it did. `is_bit_valid` does not promise that it will
// not panic (in fact, it explicitly warns that it's a possibility), and
// we have not violated any safety invariants that we must fix before
// returning.
c.iter().all(|elem|
// SAFETY: We uphold the safety contract of `is_bit_valid(elem)`, by
// precondition on the surrounding call to `is_bit_valid`. The
// memory referenced by `elem` is contained entirely within `c`, and
// satisfies the preconditions satisfied by `c`. By axiom, we assume
// that `Iterator:all` does not invalidate these preconditions
// (e.g., by writing to `elem`.) Since `elem` is derived from `c`,
// it is only possible for uninitialized bytes to occur in `elem` at
// the same bytes they occur within `c`.
unsafe { <T as TryFromBytes>::is_bit_valid(elem) }
)
});
unsafe_impl!(T: FromZeroes => FromZeroes for [T]);
unsafe_impl!(T: FromBytes => FromBytes for [T]);
unsafe_impl!(T: AsBytes => AsBytes for [T]);
unsafe_impl!(T: Unaligned => Unaligned for [T]);
}
safety_comment! {
/// SAFETY:
/// - `FromZeroes`: For thin pointers (note that `T: Sized`), the zero
/// pointer is considered "null". [1] No operations which require
/// provenance are legal on null pointers, so this is not a footgun.
///
/// NOTE(#170): Implementing `FromBytes` and `AsBytes` for raw pointers
/// would be sound, but carries provenance footguns. We want to support
/// `FromBytes` and `AsBytes` for raw pointers eventually, but we are
/// holding off until we can figure out how to address those footguns.
///
/// [1] TODO(https://github.com/rust-lang/rust/pull/116988): Cite the
/// documentation once this PR lands.
unsafe_impl!(T => FromZeroes for *const T);
unsafe_impl!(T => FromZeroes for *mut T);
}
// SIMD support
//
// Per the Unsafe Code Guidelines Reference [1]:
//
// Packed SIMD vector types are `repr(simd)` homogeneous tuple-structs
// containing `N` elements of type `T` where `N` is a power-of-two and the
// size and alignment requirements of `T` are equal:
//
// ```rust
// #[repr(simd)]
// struct Vector<T, N>(T_0, ..., T_(N - 1));
// ```
//
// ...
//
// The size of `Vector` is `N * size_of::<T>()` and its alignment is an
// implementation-defined function of `T` and `N` greater than or equal to
// `align_of::<T>()`.
//
// ...
//
// Vector elements are laid out in source field order, enabling random access
// to vector elements by reinterpreting the vector as an array:
//
// ```rust
// union U {
// vec: Vector<T, N>,
// arr: [T; N]
// }
//
// assert_eq!(size_of::<Vector<T, N>>(), size_of::<[T; N]>());
// assert!(align_of::<Vector<T, N>>() >= align_of::<[T; N]>());
//
// unsafe {
// let u = U { vec: Vector<T, N>(t_0, ..., t_(N - 1)) };
//
// assert_eq!(u.vec.0, u.arr[0]);
// // ...
// assert_eq!(u.vec.(N - 1), u.arr[N - 1]);
// }
// ```
//
// Given this background, we can observe that:
// - The size and bit pattern requirements of a SIMD type are equivalent to the
// equivalent array type. Thus, for any SIMD type whose primitive `T` is
// `TryFromBytes`, `FromZeroes`, `FromBytes`, or `AsBytes`, that SIMD type is
// also `TryFromBytes`, `FromZeroes`, `FromBytes`, or `AsBytes` respectively.
// - Since no upper bound is placed on the alignment, no SIMD type can be
// guaranteed to be `Unaligned`.
//
// Also per [1]:
//
// This chapter represents the consensus from issue #38. The statements in
// here are not (yet) "guaranteed" not to change until an RFC ratifies them.
//
// See issue #38 [2]. While this behavior is not technically guaranteed, the
// likelihood that the behavior will change such that SIMD types are no longer
// `TryFromBytes`, `FromZeroes`, `FromBytes`, or `AsBytes` is next to zero, as
// that would defeat the entire purpose of SIMD types. Nonetheless, we put this
// behavior behind the `simd` Cargo feature, which requires consumers to opt
// into this stability hazard.
//
// [1] https://rust-lang.github.io/unsafe-code-guidelines/layout/packed-simd-vectors.html
// [2] https://github.com/rust-lang/unsafe-code-guidelines/issues/38
#[cfg(feature = "simd")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "simd")))]
mod simd {
/// Defines a module which implements `TryFromBytes`, `FromZeroes`,
/// `FromBytes`, and `AsBytes` for a set of types from a module in
/// `core::arch`.
///
/// `$arch` is both the name of the defined module and the name of the
/// module in `core::arch`, and `$typ` is the list of items from that module
/// to implement `FromZeroes`, `FromBytes`, and `AsBytes` for.
#[allow(unused_macros)] // `allow(unused_macros)` is needed because some
// target/feature combinations don't emit any impls
// and thus don't use this macro.
macro_rules! simd_arch_mod {
(#[cfg $cfg:tt] $arch:ident, $mod:ident, $($typ:ident),*) => {
#[cfg $cfg]
#[cfg_attr(doc_cfg, doc(cfg $cfg))]
mod $mod {
use core::arch::$arch::{$($typ),*};
use crate::*;
impl_known_layout!($($typ),*);
safety_comment! {
/// SAFETY:
/// See comment on module definition for justification.
$( unsafe_impl!($typ: TryFromBytes, FromZeroes, FromBytes, AsBytes); )*
}
}
};
}
#[rustfmt::skip]
const _: () = {
simd_arch_mod!(
#[cfg(target_arch = "x86")]
x86, x86, __m128, __m128d, __m128i, __m256, __m256d, __m256i
);
simd_arch_mod!(
#[cfg(all(feature = "simd-nightly", target_arch = "x86"))]
x86, x86_nightly, __m512bh, __m512, __m512d, __m512i
);
simd_arch_mod!(
#[cfg(target_arch = "x86_64")]
x86_64, x86_64, __m128, __m128d, __m128i, __m256, __m256d, __m256i
);
simd_arch_mod!(
#[cfg(all(feature = "simd-nightly", target_arch = "x86_64"))]
x86_64, x86_64_nightly, __m512bh, __m512, __m512d, __m512i
);
simd_arch_mod!(
#[cfg(target_arch = "wasm32")]
wasm32, wasm32, v128
);
simd_arch_mod!(
#[cfg(all(feature = "simd-nightly", target_arch = "powerpc"))]
powerpc, powerpc, vector_bool_long, vector_double, vector_signed_long, vector_unsigned_long
);
simd_arch_mod!(
#[cfg(all(feature = "simd-nightly", target_arch = "powerpc64"))]
powerpc64, powerpc64, vector_bool_long, vector_double, vector_signed_long, vector_unsigned_long
);
simd_arch_mod!(
#[cfg(target_arch = "aarch64")]
aarch64, aarch64, float32x2_t, float32x4_t, float64x1_t, float64x2_t, int8x8_t, int8x8x2_t,
int8x8x3_t, int8x8x4_t, int8x16_t, int8x16x2_t, int8x16x3_t, int8x16x4_t, int16x4_t,
int16x8_t, int32x2_t, int32x4_t, int64x1_t, int64x2_t, poly8x8_t, poly8x8x2_t, poly8x8x3_t,
poly8x8x4_t, poly8x16_t, poly8x16x2_t, poly8x16x3_t, poly8x16x4_t, poly16x4_t, poly16x8_t,
poly64x1_t, poly64x2_t, uint8x8_t, uint8x8x2_t, uint8x8x3_t, uint8x8x4_t, uint8x16_t,
uint8x16x2_t, uint8x16x3_t, uint8x16x4_t, uint16x4_t, uint16x8_t, uint32x2_t, uint32x4_t,
uint64x1_t, uint64x2_t
);
simd_arch_mod!(
#[cfg(all(feature = "simd-nightly", target_arch = "arm"))]
arm, arm, int8x4_t, uint8x4_t
);
};
}
/// Safely transmutes a value of one type to a value of another type of the same
/// size.
///
/// The expression `$e` must have a concrete type, `T`, which implements
/// `AsBytes`. The `transmute!` expression must also have a concrete type, `U`
/// (`U` is inferred from the calling context), and `U` must implement
/// `FromBytes`.
///
/// Note that the `T` produced by the expression `$e` will *not* be dropped.
/// Semantically, its bits will be copied into a new value of type `U`, the
/// original `T` will be forgotten, and the value of type `U` will be returned.
///
/// # Examples
///
/// ```
/// # use zerocopy::transmute;
/// let one_dimensional: [u8; 8] = [0, 1, 2, 3, 4, 5, 6, 7];
///
/// let two_dimensional: [[u8; 4]; 2] = transmute!(one_dimensional);
///
/// assert_eq!(two_dimensional, [[0, 1, 2, 3], [4, 5, 6, 7]]);
/// ```
#[macro_export]
macro_rules! transmute {
($e:expr) => {{
// NOTE: This must be a macro (rather than a function with trait bounds)
// because there's no way, in a generic context, to enforce that two
// types have the same size. `core::mem::transmute` uses compiler magic
// to enforce this so long as the types are concrete.
let e = $e;
if false {
// This branch, though never taken, ensures that the type of `e` is
// `AsBytes` and that the type of this macro invocation expression
// is `FromBytes`.
struct AssertIsAsBytes<T: $crate::AsBytes>(T);
let _ = AssertIsAsBytes(e);
struct AssertIsFromBytes<U: $crate::FromBytes>(U);
#[allow(unused, unreachable_code)]
let u = AssertIsFromBytes(loop {});
u.0
} else {
// SAFETY: `core::mem::transmute` ensures that the type of `e` and
// the type of this macro invocation expression have the same size.
// We know this transmute is safe thanks to the `AsBytes` and
// `FromBytes` bounds enforced by the `false` branch.
//
// We use this reexport of `core::mem::transmute` because we know it
// will always be available for crates which are using the 2015
// edition of Rust. By contrast, if we were to use
// `std::mem::transmute`, this macro would not work for such crates
// in `no_std` contexts, and if we were to use
// `core::mem::transmute`, this macro would not work in `std`
// contexts in which `core` was not manually imported. This is not a
// problem for 2018 edition crates.
unsafe {
// Clippy: It's okay to transmute a type to itself.
#[allow(clippy::useless_transmute, clippy::missing_transmute_annotations)]
$crate::macro_util::core_reexport::mem::transmute(e)
}
}
}}
}
/// Safely transmutes a mutable or immutable reference of one type to an
/// immutable reference of another type of the same size.
///
/// The expression `$e` must have a concrete type, `&T` or `&mut T`, where `T:
/// Sized + AsBytes`. The `transmute_ref!` expression must also have a concrete
/// type, `&U` (`U` is inferred from the calling context), where `U: Sized +
/// FromBytes`. It must be the case that `align_of::<T>() >= align_of::<U>()`.
///
/// The lifetime of the input type, `&T` or `&mut T`, must be the same as or
/// outlive the lifetime of the output type, `&U`.
///
/// # Examples
///
/// ```
/// # use zerocopy::transmute_ref;
/// let one_dimensional: [u8; 8] = [0, 1, 2, 3, 4, 5, 6, 7];
///
/// let two_dimensional: &[[u8; 4]; 2] = transmute_ref!(&one_dimensional);
///
/// assert_eq!(two_dimensional, &[[0, 1, 2, 3], [4, 5, 6, 7]]);
/// ```
///
/// # Alignment increase error message
///
/// Because of limitations on macros, the error message generated when
/// `transmute_ref!` is used to transmute from a type of lower alignment to a
/// type of higher alignment is somewhat confusing. For example, the following
/// code:
///
/// ```compile_fail
/// const INCREASE_ALIGNMENT: &u16 = zerocopy::transmute_ref!(&[0u8; 2]);
/// ```
///
/// ...generates the following error:
///
/// ```text
/// error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
/// --> src/lib.rs:1524:34
/// |
/// 5 | const INCREASE_ALIGNMENT: &u16 = zerocopy::transmute_ref!(&[0u8; 2]);
/// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/// |
/// = note: source type: `AlignOf<[u8; 2]>` (8 bits)
/// = note: target type: `MaxAlignsOf<[u8; 2], u16>` (16 bits)
/// = note: this error originates in the macro `$crate::assert_align_gt_eq` which comes from the expansion of the macro `transmute_ref` (in Nightly builds, run with -Z macro-backtrace for more info)
/// ```
///
/// This is saying that `max(align_of::<T>(), align_of::<U>()) !=
/// align_of::<T>()`, which is equivalent to `align_of::<T>() <
/// align_of::<U>()`.
#[macro_export]
macro_rules! transmute_ref {
($e:expr) => {{
// NOTE: This must be a macro (rather than a function with trait bounds)
// because there's no way, in a generic context, to enforce that two
// types have the same size or alignment.
// Ensure that the source type is a reference or a mutable reference
// (note that mutable references are implicitly reborrowed here).
let e: &_ = $e;
#[allow(unused, clippy::diverging_sub_expression)]
if false {
// This branch, though never taken, ensures that the type of `e` is
// `&T` where `T: 't + Sized + AsBytes`, that the type of this macro
// expression is `&U` where `U: 'u + Sized + FromBytes`, and that
// `'t` outlives `'u`.
struct AssertIsAsBytes<'a, T: ::core::marker::Sized + $crate::AsBytes>(&'a T);
let _ = AssertIsAsBytes(e);
struct AssertIsFromBytes<'a, U: ::core::marker::Sized + $crate::FromBytes>(&'a U);
#[allow(unused, unreachable_code)]
let u = AssertIsFromBytes(loop {});
u.0
} else if false {
// This branch, though never taken, ensures that `size_of::<T>() ==
// size_of::<U>()` and that that `align_of::<T>() >=
// align_of::<U>()`.
// `t` is inferred to have type `T` because it's assigned to `e` (of
// type `&T`) as `&t`.
let mut t = unreachable!();
e = &t;
// `u` is inferred to have type `U` because it's used as `&u` as the
// value returned from this branch.
let u;
$crate::assert_size_eq!(t, u);
$crate::assert_align_gt_eq!(t, u);
&u
} else {
// SAFETY: For source type `Src` and destination type `Dst`:
// - We know that `Src: AsBytes` and `Dst: FromBytes` thanks to the
// uses of `AssertIsAsBytes` and `AssertIsFromBytes` above.
// - We know that `size_of::<Src>() == size_of::<Dst>()` thanks to
// the use of `assert_size_eq!` above.
// - We know that `align_of::<Src>() >= align_of::<Dst>()` thanks to
// the use of `assert_align_gt_eq!` above.
unsafe { $crate::macro_util::transmute_ref(e) }
}
}}
}
/// Safely transmutes a mutable reference of one type to an mutable reference of
/// another type of the same size.
///
/// The expression `$e` must have a concrete type, `&mut T`, where `T: Sized +
/// AsBytes`. The `transmute_mut!` expression must also have a concrete type,
/// `&mut U` (`U` is inferred from the calling context), where `U: Sized +
/// FromBytes`. It must be the case that `align_of::<T>() >= align_of::<U>()`.
///
/// The lifetime of the input type, `&mut T`, must be the same as or outlive the
/// lifetime of the output type, `&mut U`.
///
/// # Examples
///
/// ```
/// # use zerocopy::transmute_mut;
/// let mut one_dimensional: [u8; 8] = [0, 1, 2, 3, 4, 5, 6, 7];
///
/// let two_dimensional: &mut [[u8; 4]; 2] = transmute_mut!(&mut one_dimensional);
///
/// assert_eq!(two_dimensional, &[[0, 1, 2, 3], [4, 5, 6, 7]]);
///
/// two_dimensional.reverse();
///
/// assert_eq!(one_dimensional, [4, 5, 6, 7, 0, 1, 2, 3]);
/// ```
///
/// # Alignment increase error message
///
/// Because of limitations on macros, the error message generated when
/// `transmute_mut!` is used to transmute from a type of lower alignment to a
/// type of higher alignment is somewhat confusing. For example, the following
/// code:
///
/// ```compile_fail
/// const INCREASE_ALIGNMENT: &mut u16 = zerocopy::transmute_mut!(&mut [0u8; 2]);
/// ```
///
/// ...generates the following error:
///
/// ```text
/// error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
/// --> src/lib.rs:1524:34
/// |
/// 5 | const INCREASE_ALIGNMENT: &mut u16 = zerocopy::transmute_mut!(&mut [0u8; 2]);
/// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/// |
/// = note: source type: `AlignOf<[u8; 2]>` (8 bits)
/// = note: target type: `MaxAlignsOf<[u8; 2], u16>` (16 bits)
/// = note: this error originates in the macro `$crate::assert_align_gt_eq` which comes from the expansion of the macro `transmute_mut` (in Nightly builds, run with -Z macro-backtrace for more info)
/// ```
///
/// This is saying that `max(align_of::<T>(), align_of::<U>()) !=
/// align_of::<T>()`, which is equivalent to `align_of::<T>() <
/// align_of::<U>()`.
#[macro_export]
macro_rules! transmute_mut {
($e:expr) => {{
// NOTE: This must be a macro (rather than a function with trait bounds)
// because there's no way, in a generic context, to enforce that two
// types have the same size or alignment.
// Ensure that the source type is a mutable reference.
let e: &mut _ = $e;
#[allow(unused, clippy::diverging_sub_expression)]
if false {
// This branch, though never taken, ensures that the type of `e` is
// `&mut T` where `T: 't + Sized + FromBytes + AsBytes`, that the
// type of this macro expression is `&mut U` where `U: 'u + Sized +
// FromBytes + AsBytes`.
// We use immutable references here rather than mutable so that, if
// this macro is used in a const context (in which, as of this
// writing, mutable references are banned), the error message
// appears to originate in the user's code rather than in the
// internals of this macro.
struct AssertSrcIsFromBytes<'a, T: ::core::marker::Sized + $crate::FromBytes>(&'a T);
struct AssertSrcIsAsBytes<'a, T: ::core::marker::Sized + $crate::AsBytes>(&'a T);
struct AssertDstIsFromBytes<'a, T: ::core::marker::Sized + $crate::FromBytes>(&'a T);
struct AssertDstIsAsBytes<'a, T: ::core::marker::Sized + $crate::AsBytes>(&'a T);
if true {
let _ = AssertSrcIsFromBytes(&*e);
} else {
let _ = AssertSrcIsAsBytes(&*e);
}
if true {
#[allow(unused, unreachable_code)]
let u = AssertDstIsFromBytes(loop {});
&mut *u.0
} else {
#[allow(unused, unreachable_code)]
let u = AssertDstIsAsBytes(loop {});
&mut *u.0
}
} else if false {
// This branch, though never taken, ensures that `size_of::<T>() ==
// size_of::<U>()` and that that `align_of::<T>() >=
// align_of::<U>()`.
// `t` is inferred to have type `T` because it's assigned to `e` (of
// type `&mut T`) as `&mut t`.
let mut t = unreachable!();
e = &mut t;
// `u` is inferred to have type `U` because it's used as `&mut u` as
// the value returned from this branch.
let u;
$crate::assert_size_eq!(t, u);
$crate::assert_align_gt_eq!(t, u);
&mut u
} else {
// SAFETY: For source type `Src` and destination type `Dst`:
// - We know that `Src: FromBytes + AsBytes` and `Dst: FromBytes +
// AsBytes` thanks to the uses of `AssertSrcIsFromBytes`,
// `AssertSrcIsAsBytes`, `AssertDstIsFromBytes`, and
// `AssertDstIsAsBytes` above.
// - We know that `size_of::<Src>() == size_of::<Dst>()` thanks to
// the use of `assert_size_eq!` above.
// - We know that `align_of::<Src>() >= align_of::<Dst>()` thanks to
// the use of `assert_align_gt_eq!` above.
unsafe { $crate::macro_util::transmute_mut(e) }
}
}}
}
/// Includes a file and safely transmutes it to a value of an arbitrary type.
///
/// The file will be included as a byte array, `[u8; N]`, which will be
/// transmuted to another type, `T`. `T` is inferred from the calling context,
/// and must implement [`FromBytes`].
///
/// The file is located relative to the current file (similarly to how modules
/// are found). The provided path is interpreted in a platform-specific way at
/// compile time. So, for instance, an invocation with a Windows path containing
/// backslashes `\` would not compile correctly on Unix.
///
/// `include_value!` is ignorant of byte order. For byte order-aware types, see
/// the [`byteorder`] module.
///
/// # Examples
///
/// Assume there are two files in the same directory with the following
/// contents:
///
/// File `data` (no trailing newline):
///
/// ```text
/// abcd
/// ```
///
/// File `main.rs`:
///
/// ```rust
/// use zerocopy::include_value;
/// # macro_rules! include_value {
/// # ($file:expr) => { zerocopy::include_value!(concat!("../testdata/include_value/", $file)) };
/// # }
///
/// fn main() {
/// let as_u32: u32 = include_value!("data");
/// assert_eq!(as_u32, u32::from_ne_bytes([b'a', b'b', b'c', b'd']));
/// let as_i32: i32 = include_value!("data");
/// assert_eq!(as_i32, i32::from_ne_bytes([b'a', b'b', b'c', b'd']));
/// }
/// ```
#[doc(alias("include_bytes", "include_data", "include_type"))]
#[macro_export]
macro_rules! include_value {
($file:expr $(,)?) => {
$crate::transmute!(*::core::include_bytes!($file))
};
}
/// A typed reference derived from a byte slice.
///
/// A `Ref<B, T>` is a reference to a `T` which is stored in a byte slice, `B`.
/// Unlike a native reference (`&T` or `&mut T`), `Ref<B, T>` has the same
/// mutability as the byte slice it was constructed from (`B`).
///
/// # Examples
///
/// `Ref` can be used to treat a sequence of bytes as a structured type, and to
/// read and write the fields of that type as if the byte slice reference were
/// simply a reference to that type.
///
/// ```rust
/// # #[cfg(feature = "derive")] { // This example uses derives, and won't compile without them
/// use zerocopy::{AsBytes, ByteSlice, ByteSliceMut, FromBytes, FromZeroes, Ref, Unaligned};
///
/// #[derive(FromZeroes, FromBytes, AsBytes, Unaligned)]
/// #[repr(C)]
/// struct UdpHeader {
/// src_port: [u8; 2],
/// dst_port: [u8; 2],
/// length: [u8; 2],
/// checksum: [u8; 2],
/// }
///
/// struct UdpPacket<B> {
/// header: Ref<B, UdpHeader>,
/// body: B,
/// }
///
/// impl<B: ByteSlice> UdpPacket<B> {
/// pub fn parse(bytes: B) -> Option<UdpPacket<B>> {
/// let (header, body) = Ref::new_unaligned_from_prefix(bytes)?;
/// Some(UdpPacket { header, body })
/// }
///
/// pub fn get_src_port(&self) -> [u8; 2] {
/// self.header.src_port
/// }
/// }
///
/// impl<B: ByteSliceMut> UdpPacket<B> {
/// pub fn set_src_port(&mut self, src_port: [u8; 2]) {
/// self.header.src_port = src_port;
/// }
/// }
/// # }
/// ```
pub struct Ref<B, T: ?Sized>(B, PhantomData<T>);
/// Deprecated: prefer [`Ref`] instead.
#[deprecated(since = "0.7.0", note = "LayoutVerified has been renamed to Ref")]
#[doc(hidden)]
pub type LayoutVerified<B, T> = Ref<B, T>;
impl<B, T> Ref<B, T>
where
B: ByteSlice,
{
/// Constructs a new `Ref`.
///
/// `new` verifies that `bytes.len() == size_of::<T>()` and that `bytes` is
/// aligned to `align_of::<T>()`, and constructs a new `Ref`. If either of
/// these checks fail, it returns `None`.
#[inline]
pub fn new(bytes: B) -> Option<Ref<B, T>> {
if bytes.len() != mem::size_of::<T>() || !util::aligned_to::<_, T>(bytes.deref()) {
return None;
}
Some(Ref(bytes, PhantomData))
}
/// Constructs a new `Ref` from the prefix of a byte slice.
///
/// `new_from_prefix` verifies that `bytes.len() >= size_of::<T>()` and that
/// `bytes` is aligned to `align_of::<T>()`. It consumes the first
/// `size_of::<T>()` bytes from `bytes` to construct a `Ref`, and returns
/// the remaining bytes to the caller. If either the length or alignment
/// checks fail, it returns `None`.
#[inline]
pub fn new_from_prefix(bytes: B) -> Option<(Ref<B, T>, B)> {
if bytes.len() < mem::size_of::<T>() || !util::aligned_to::<_, T>(bytes.deref()) {
return None;
}
let (bytes, suffix) = bytes.split_at(mem::size_of::<T>());
Some((Ref(bytes, PhantomData), suffix))
}
/// Constructs a new `Ref` from the suffix of a byte slice.
///
/// `new_from_suffix` verifies that `bytes.len() >= size_of::<T>()` and that
/// the last `size_of::<T>()` bytes of `bytes` are aligned to
/// `align_of::<T>()`. It consumes the last `size_of::<T>()` bytes from
/// `bytes` to construct a `Ref`, and returns the preceding bytes to the
/// caller. If either the length or alignment checks fail, it returns
/// `None`.
#[inline]
pub fn new_from_suffix(bytes: B) -> Option<(B, Ref<B, T>)> {
let bytes_len = bytes.len();
let split_at = bytes_len.checked_sub(mem::size_of::<T>())?;
let (prefix, bytes) = bytes.split_at(split_at);
if !util::aligned_to::<_, T>(bytes.deref()) {
return None;
}
Some((prefix, Ref(bytes, PhantomData)))
}
}
impl<B, T> Ref<B, [T]>
where
B: ByteSlice,
{
/// Constructs a new `Ref` of a slice type.
///
/// `new_slice` verifies that `bytes.len()` is a multiple of
/// `size_of::<T>()` and that `bytes` is aligned to `align_of::<T>()`, and
/// constructs a new `Ref`. If either of these checks fail, it returns
/// `None`.
///
/// # Panics
///
/// `new_slice` panics if `T` is a zero-sized type.
#[inline]
pub fn new_slice(bytes: B) -> Option<Ref<B, [T]>> {
let remainder = bytes
.len()
.checked_rem(mem::size_of::<T>())
.expect("Ref::new_slice called on a zero-sized type");
if remainder != 0 || !util::aligned_to::<_, T>(bytes.deref()) {
return None;
}
Some(Ref(bytes, PhantomData))
}
/// Constructs a new `Ref` of a slice type from the prefix of a byte slice.
///
/// `new_slice_from_prefix` verifies that `bytes.len() >= size_of::<T>() *
/// count` and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// first `size_of::<T>() * count` bytes from `bytes` to construct a `Ref`,
/// and returns the remaining bytes to the caller. It also ensures that
/// `sizeof::<T>() * count` does not overflow a `usize`. If any of the
/// length, alignment, or overflow checks fail, it returns `None`.
///
/// # Panics
///
/// `new_slice_from_prefix` panics if `T` is a zero-sized type.
#[inline]
pub fn new_slice_from_prefix(bytes: B, count: usize) -> Option<(Ref<B, [T]>, B)> {
let expected_len = match mem::size_of::<T>().checked_mul(count) {
Some(len) => len,
None => return None,
};
if bytes.len() < expected_len {
return None;
}
let (prefix, bytes) = bytes.split_at(expected_len);
Self::new_slice(prefix).map(move |l| (l, bytes))
}
/// Constructs a new `Ref` of a slice type from the suffix of a byte slice.
///
/// `new_slice_from_suffix` verifies that `bytes.len() >= size_of::<T>() *
/// count` and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// last `size_of::<T>() * count` bytes from `bytes` to construct a `Ref`,
/// and returns the preceding bytes to the caller. It also ensures that
/// `sizeof::<T>() * count` does not overflow a `usize`. If any of the
/// length, alignment, or overflow checks fail, it returns `None`.
///
/// # Panics
///
/// `new_slice_from_suffix` panics if `T` is a zero-sized type.
#[inline]
pub fn new_slice_from_suffix(bytes: B, count: usize) -> Option<(B, Ref<B, [T]>)> {
let expected_len = match mem::size_of::<T>().checked_mul(count) {
Some(len) => len,
None => return None,
};
let split_at = bytes.len().checked_sub(expected_len)?;
let (bytes, suffix) = bytes.split_at(split_at);
Self::new_slice(suffix).map(move |l| (bytes, l))
}
}
fn map_zeroed<B: ByteSliceMut, T: ?Sized>(opt: Option<Ref<B, T>>) -> Option<Ref<B, T>> {
match opt {
Some(mut r) => {
r.0.fill(0);
Some(r)
}
None => None,
}
}
fn map_prefix_tuple_zeroed<B: ByteSliceMut, T: ?Sized>(
opt: Option<(Ref<B, T>, B)>,
) -> Option<(Ref<B, T>, B)> {
match opt {
Some((mut r, rest)) => {
r.0.fill(0);
Some((r, rest))
}
None => None,
}
}
fn map_suffix_tuple_zeroed<B: ByteSliceMut, T: ?Sized>(
opt: Option<(B, Ref<B, T>)>,
) -> Option<(B, Ref<B, T>)> {
map_prefix_tuple_zeroed(opt.map(|(a, b)| (b, a))).map(|(a, b)| (b, a))
}
impl<B, T> Ref<B, T>
where
B: ByteSliceMut,
{
/// Constructs a new `Ref` after zeroing the bytes.
///
/// `new_zeroed` verifies that `bytes.len() == size_of::<T>()` and that
/// `bytes` is aligned to `align_of::<T>()`, and constructs a new `Ref`. If
/// either of these checks fail, it returns `None`.
///
/// If the checks succeed, then `bytes` will be initialized to zero. This
/// can be useful when re-using buffers to ensure that sensitive data
/// previously stored in the buffer is not leaked.
#[inline(always)]
pub fn new_zeroed(bytes: B) -> Option<Ref<B, T>> {
map_zeroed(Self::new(bytes))
}
/// Constructs a new `Ref` from the prefix of a byte slice, zeroing the
/// prefix.
///
/// `new_from_prefix_zeroed` verifies that `bytes.len() >= size_of::<T>()`
/// and that `bytes` is aligned to `align_of::<T>()`. It consumes the first
/// `size_of::<T>()` bytes from `bytes` to construct a `Ref`, and returns
/// the remaining bytes to the caller. If either the length or alignment
/// checks fail, it returns `None`.
///
/// If the checks succeed, then the prefix which is consumed will be
/// initialized to zero. This can be useful when re-using buffers to ensure
/// that sensitive data previously stored in the buffer is not leaked.
#[inline(always)]
pub fn new_from_prefix_zeroed(bytes: B) -> Option<(Ref<B, T>, B)> {
map_prefix_tuple_zeroed(Self::new_from_prefix(bytes))
}
/// Constructs a new `Ref` from the suffix of a byte slice, zeroing the
/// suffix.
///
/// `new_from_suffix_zeroed` verifies that `bytes.len() >= size_of::<T>()`
/// and that the last `size_of::<T>()` bytes of `bytes` are aligned to
/// `align_of::<T>()`. It consumes the last `size_of::<T>()` bytes from
/// `bytes` to construct a `Ref`, and returns the preceding bytes to the
/// caller. If either the length or alignment checks fail, it returns
/// `None`.
///
/// If the checks succeed, then the suffix which is consumed will be
/// initialized to zero. This can be useful when re-using buffers to ensure
/// that sensitive data previously stored in the buffer is not leaked.
#[inline(always)]
pub fn new_from_suffix_zeroed(bytes: B) -> Option<(B, Ref<B, T>)> {
map_suffix_tuple_zeroed(Self::new_from_suffix(bytes))
}
}
impl<B, T> Ref<B, [T]>
where
B: ByteSliceMut,
{
/// Constructs a new `Ref` of a slice type after zeroing the bytes.
///
/// `new_slice_zeroed` verifies that `bytes.len()` is a multiple of
/// `size_of::<T>()` and that `bytes` is aligned to `align_of::<T>()`, and
/// constructs a new `Ref`. If either of these checks fail, it returns
/// `None`.
///
/// If the checks succeed, then `bytes` will be initialized to zero. This
/// can be useful when re-using buffers to ensure that sensitive data
/// previously stored in the buffer is not leaked.
///
/// # Panics
///
/// `new_slice` panics if `T` is a zero-sized type.
#[inline(always)]
pub fn new_slice_zeroed(bytes: B) -> Option<Ref<B, [T]>> {
map_zeroed(Self::new_slice(bytes))
}
/// Constructs a new `Ref` of a slice type from the prefix of a byte slice,
/// after zeroing the bytes.
///
/// `new_slice_from_prefix` verifies that `bytes.len() >= size_of::<T>() *
/// count` and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// first `size_of::<T>() * count` bytes from `bytes` to construct a `Ref`,
/// and returns the remaining bytes to the caller. It also ensures that
/// `sizeof::<T>() * count` does not overflow a `usize`. If any of the
/// length, alignment, or overflow checks fail, it returns `None`.
///
/// If the checks succeed, then the suffix which is consumed will be
/// initialized to zero. This can be useful when re-using buffers to ensure
/// that sensitive data previously stored in the buffer is not leaked.
///
/// # Panics
///
/// `new_slice_from_prefix_zeroed` panics if `T` is a zero-sized type.
#[inline(always)]
pub fn new_slice_from_prefix_zeroed(bytes: B, count: usize) -> Option<(Ref<B, [T]>, B)> {
map_prefix_tuple_zeroed(Self::new_slice_from_prefix(bytes, count))
}
/// Constructs a new `Ref` of a slice type from the prefix of a byte slice,
/// after zeroing the bytes.
///
/// `new_slice_from_suffix` verifies that `bytes.len() >= size_of::<T>() *
/// count` and that `bytes` is aligned to `align_of::<T>()`. It consumes the
/// last `size_of::<T>() * count` bytes from `bytes` to construct a `Ref`,
/// and returns the preceding bytes to the caller. It also ensures that
/// `sizeof::<T>() * count` does not overflow a `usize`. If any of the
/// length, alignment, or overflow checks fail, it returns `None`.
///
/// If the checks succeed, then the consumed suffix will be initialized to
/// zero. This can be useful when re-using buffers to ensure that sensitive
/// data previously stored in the buffer is not leaked.
///
/// # Panics
///
/// `new_slice_from_suffix_zeroed` panics if `T` is a zero-sized type.
#[inline(always)]
pub fn new_slice_from_suffix_zeroed(bytes: B, count: usize) -> Option<(B, Ref<B, [T]>)> {
map_suffix_tuple_zeroed(Self::new_slice_from_suffix(bytes, count))
}
}
impl<B, T> Ref<B, T>
where
B: ByteSlice,
T: Unaligned,
{
/// Constructs a new `Ref` for a type with no alignment requirement.
///
/// `new_unaligned` verifies that `bytes.len() == size_of::<T>()` and
/// constructs a new `Ref`. If the check fails, it returns `None`.
#[inline(always)]
pub fn new_unaligned(bytes: B) -> Option<Ref<B, T>> {
Ref::new(bytes)
}
/// Constructs a new `Ref` from the prefix of a byte slice for a type with
/// no alignment requirement.
///
/// `new_unaligned_from_prefix` verifies that `bytes.len() >=
/// size_of::<T>()`. It consumes the first `size_of::<T>()` bytes from
/// `bytes` to construct a `Ref`, and returns the remaining bytes to the
/// caller. If the length check fails, it returns `None`.
#[inline(always)]
pub fn new_unaligned_from_prefix(bytes: B) -> Option<(Ref<B, T>, B)> {
Ref::new_from_prefix(bytes)
}
/// Constructs a new `Ref` from the suffix of a byte slice for a type with
/// no alignment requirement.
///
/// `new_unaligned_from_suffix` verifies that `bytes.len() >=
/// size_of::<T>()`. It consumes the last `size_of::<T>()` bytes from
/// `bytes` to construct a `Ref`, and returns the preceding bytes to the
/// caller. If the length check fails, it returns `None`.
#[inline(always)]
pub fn new_unaligned_from_suffix(bytes: B) -> Option<(B, Ref<B, T>)> {
Ref::new_from_suffix(bytes)
}
}
impl<B, T> Ref<B, [T]>
where
B: ByteSlice,
T: Unaligned,
{
/// Constructs a new `Ref` of a slice type with no alignment requirement.
///
/// `new_slice_unaligned` verifies that `bytes.len()` is a multiple of
/// `size_of::<T>()` and constructs a new `Ref`. If the check fails, it
/// returns `None`.
///
/// # Panics
///
/// `new_slice` panics if `T` is a zero-sized type.
#[inline(always)]
pub fn new_slice_unaligned(bytes: B) -> Option<Ref<B, [T]>> {
Ref::new_slice(bytes)
}
/// Constructs a new `Ref` of a slice type with no alignment requirement
/// from the prefix of a byte slice.
///
/// `new_slice_from_prefix` verifies that `bytes.len() >= size_of::<T>() *
/// count`. It consumes the first `size_of::<T>() * count` bytes from
/// `bytes` to construct a `Ref`, and returns the remaining bytes to the
/// caller. It also ensures that `sizeof::<T>() * count` does not overflow a
/// `usize`. If either the length, or overflow checks fail, it returns
/// `None`.
///
/// # Panics
///
/// `new_slice_unaligned_from_prefix` panics if `T` is a zero-sized type.
#[inline(always)]
pub fn new_slice_unaligned_from_prefix(bytes: B, count: usize) -> Option<(Ref<B, [T]>, B)> {
Ref::new_slice_from_prefix(bytes, count)
}
/// Constructs a new `Ref` of a slice type with no alignment requirement
/// from the suffix of a byte slice.
///
/// `new_slice_from_suffix` verifies that `bytes.len() >= size_of::<T>() *
/// count`. It consumes the last `size_of::<T>() * count` bytes from `bytes`
/// to construct a `Ref`, and returns the remaining bytes to the caller. It
/// also ensures that `sizeof::<T>() * count` does not overflow a `usize`.
/// If either the length, or overflow checks fail, it returns `None`.
///
/// # Panics
///
/// `new_slice_unaligned_from_suffix` panics if `T` is a zero-sized type.
#[inline(always)]
pub fn new_slice_unaligned_from_suffix(bytes: B, count: usize) -> Option<(B, Ref<B, [T]>)> {
Ref::new_slice_from_suffix(bytes, count)
}
}
impl<B, T> Ref<B, T>
where
B: ByteSliceMut,
T: Unaligned,
{
/// Constructs a new `Ref` for a type with no alignment requirement, zeroing
/// the bytes.
///
/// `new_unaligned_zeroed` verifies that `bytes.len() == size_of::<T>()` and
/// constructs a new `Ref`. If the check fails, it returns `None`.
///
/// If the check succeeds, then `bytes` will be initialized to zero. This
/// can be useful when re-using buffers to ensure that sensitive data
/// previously stored in the buffer is not leaked.
#[inline(always)]
pub fn new_unaligned_zeroed(bytes: B) -> Option<Ref<B, T>> {
map_zeroed(Self::new_unaligned(bytes))
}
/// Constructs a new `Ref` from the prefix of a byte slice for a type with
/// no alignment requirement, zeroing the prefix.
///
/// `new_unaligned_from_prefix_zeroed` verifies that `bytes.len() >=
/// size_of::<T>()`. It consumes the first `size_of::<T>()` bytes from
/// `bytes` to construct a `Ref`, and returns the remaining bytes to the
/// caller. If the length check fails, it returns `None`.
///
/// If the check succeeds, then the prefix which is consumed will be
/// initialized to zero. This can be useful when re-using buffers to ensure
/// that sensitive data previously stored in the buffer is not leaked.
#[inline(always)]
pub fn new_unaligned_from_prefix_zeroed(bytes: B) -> Option<(Ref<B, T>, B)> {
map_prefix_tuple_zeroed(Self::new_unaligned_from_prefix(bytes))
}
/// Constructs a new `Ref` from the suffix of a byte slice for a type with
/// no alignment requirement, zeroing the suffix.
///
/// `new_unaligned_from_suffix_zeroed` verifies that `bytes.len() >=
/// size_of::<T>()`. It consumes the last `size_of::<T>()` bytes from
/// `bytes` to construct a `Ref`, and returns the preceding bytes to the
/// caller. If the length check fails, it returns `None`.
///
/// If the check succeeds, then the suffix which is consumed will be
/// initialized to zero. This can be useful when re-using buffers to ensure
/// that sensitive data previously stored in the buffer is not leaked.
#[inline(always)]
pub fn new_unaligned_from_suffix_zeroed(bytes: B) -> Option<(B, Ref<B, T>)> {
map_suffix_tuple_zeroed(Self::new_unaligned_from_suffix(bytes))
}
}
impl<B, T> Ref<B, [T]>
where
B: ByteSliceMut,
T: Unaligned,
{
/// Constructs a new `Ref` for a slice type with no alignment requirement,
/// zeroing the bytes.
///
/// `new_slice_unaligned_zeroed` verifies that `bytes.len()` is a multiple
/// of `size_of::<T>()` and constructs a new `Ref`. If the check fails, it
/// returns `None`.
///
/// If the check succeeds, then `bytes` will be initialized to zero. This
/// can be useful when re-using buffers to ensure that sensitive data
/// previously stored in the buffer is not leaked.
///
/// # Panics
///
/// `new_slice` panics if `T` is a zero-sized type.
#[inline(always)]
pub fn new_slice_unaligned_zeroed(bytes: B) -> Option<Ref<B, [T]>> {
map_zeroed(Self::new_slice_unaligned(bytes))
}
/// Constructs a new `Ref` of a slice type with no alignment requirement
/// from the prefix of a byte slice, after zeroing the bytes.
///
/// `new_slice_from_prefix` verifies that `bytes.len() >= size_of::<T>() *
/// count`. It consumes the first `size_of::<T>() * count` bytes from
/// `bytes` to construct a `Ref`, and returns the remaining bytes to the
/// caller. It also ensures that `sizeof::<T>() * count` does not overflow a
/// `usize`. If either the length, or overflow checks fail, it returns
/// `None`.
///
/// If the checks succeed, then the prefix will be initialized to zero. This
/// can be useful when re-using buffers to ensure that sensitive data
/// previously stored in the buffer is not leaked.
///
/// # Panics
///
/// `new_slice_unaligned_from_prefix_zeroed` panics if `T` is a zero-sized
/// type.
#[inline(always)]
pub fn new_slice_unaligned_from_prefix_zeroed(
bytes: B,
count: usize,
) -> Option<(Ref<B, [T]>, B)> {
map_prefix_tuple_zeroed(Self::new_slice_unaligned_from_prefix(bytes, count))
}
/// Constructs a new `Ref` of a slice type with no alignment requirement
/// from the suffix of a byte slice, after zeroing the bytes.
///
/// `new_slice_from_suffix` verifies that `bytes.len() >= size_of::<T>() *
/// count`. It consumes the last `size_of::<T>() * count` bytes from `bytes`
/// to construct a `Ref`, and returns the remaining bytes to the caller. It
/// also ensures that `sizeof::<T>() * count` does not overflow a `usize`.
/// If either the length, or overflow checks fail, it returns `None`.
///
/// If the checks succeed, then the suffix will be initialized to zero. This
/// can be useful when re-using buffers to ensure that sensitive data
/// previously stored in the buffer is not leaked.
///
/// # Panics
///
/// `new_slice_unaligned_from_suffix_zeroed` panics if `T` is a zero-sized
/// type.
#[inline(always)]
pub fn new_slice_unaligned_from_suffix_zeroed(
bytes: B,
count: usize,
) -> Option<(B, Ref<B, [T]>)> {
map_suffix_tuple_zeroed(Self::new_slice_unaligned_from_suffix(bytes, count))
}
}
impl<'a, B, T> Ref<B, T>
where
B: 'a + ByteSlice,
T: FromBytes,
{
/// Converts this `Ref` into a reference.
///
/// `into_ref` consumes the `Ref`, and returns a reference to `T`.
#[inline(always)]
pub fn into_ref(self) -> &'a T {
assert!(B::INTO_REF_INTO_MUT_ARE_SOUND);
// SAFETY: According to the safety preconditions on
// `ByteSlice::INTO_REF_INTO_MUT_ARE_SOUND`, the preceding assert
// ensures that, given `B: 'a`, it is sound to drop `self` and still
// access the underlying memory using reads for `'a`.
unsafe { self.deref_helper() }
}
}
impl<'a, B, T> Ref<B, T>
where
B: 'a + ByteSliceMut,
T: FromBytes + AsBytes,
{
/// Converts this `Ref` into a mutable reference.
///
/// `into_mut` consumes the `Ref`, and returns a mutable reference to `T`.
#[inline(always)]
pub fn into_mut(mut self) -> &'a mut T {
assert!(B::INTO_REF_INTO_MUT_ARE_SOUND);
// SAFETY: According to the safety preconditions on
// `ByteSlice::INTO_REF_INTO_MUT_ARE_SOUND`, the preceding assert
// ensures that, given `B: 'a + ByteSliceMut`, it is sound to drop
// `self` and still access the underlying memory using both reads and
// writes for `'a`.
unsafe { self.deref_mut_helper() }
}
}
impl<'a, B, T> Ref<B, [T]>
where
B: 'a + ByteSlice,
T: FromBytes,
{
/// Converts this `Ref` into a slice reference.
///
/// `into_slice` consumes the `Ref`, and returns a reference to `[T]`.
#[inline(always)]
pub fn into_slice(self) -> &'a [T] {
assert!(B::INTO_REF_INTO_MUT_ARE_SOUND);
// SAFETY: According to the safety preconditions on
// `ByteSlice::INTO_REF_INTO_MUT_ARE_SOUND`, the preceding assert
// ensures that, given `B: 'a`, it is sound to drop `self` and still
// access the underlying memory using reads for `'a`.
unsafe { self.deref_slice_helper() }
}
}
impl<'a, B, T> Ref<B, [T]>
where
B: 'a + ByteSliceMut,
T: FromBytes + AsBytes,
{
/// Converts this `Ref` into a mutable slice reference.
///
/// `into_mut_slice` consumes the `Ref`, and returns a mutable reference to
/// `[T]`.
#[inline(always)]
pub fn into_mut_slice(mut self) -> &'a mut [T] {
assert!(B::INTO_REF_INTO_MUT_ARE_SOUND);
// SAFETY: According to the safety preconditions on
// `ByteSlice::INTO_REF_INTO_MUT_ARE_SOUND`, the preceding assert
// ensures that, given `B: 'a + ByteSliceMut`, it is sound to drop
// `self` and still access the underlying memory using both reads and
// writes for `'a`.
unsafe { self.deref_mut_slice_helper() }
}
}
impl<B, T> Ref<B, T>
where
B: ByteSlice,
T: FromBytes,
{
/// Creates an immutable reference to `T` with a specific lifetime.
///
/// # Safety
///
/// The type bounds on this method guarantee that it is safe to create an
/// immutable reference to `T` from `self`. However, since the lifetime `'a`
/// is not required to be shorter than the lifetime of the reference to
/// `self`, the caller must guarantee that the lifetime `'a` is valid for
/// this reference. In particular, the referent must exist for all of `'a`,
/// and no mutable references to the same memory may be constructed during
/// `'a`.
unsafe fn deref_helper<'a>(&self) -> &'a T {
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe {
&*self.0.as_ptr().cast::<T>()
}
}
}
impl<B, T> Ref<B, T>
where
B: ByteSliceMut,
T: FromBytes + AsBytes,
{
/// Creates a mutable reference to `T` with a specific lifetime.
///
/// # Safety
///
/// The type bounds on this method guarantee that it is safe to create a
/// mutable reference to `T` from `self`. However, since the lifetime `'a`
/// is not required to be shorter than the lifetime of the reference to
/// `self`, the caller must guarantee that the lifetime `'a` is valid for
/// this reference. In particular, the referent must exist for all of `'a`,
/// and no other references - mutable or immutable - to the same memory may
/// be constructed during `'a`.
unsafe fn deref_mut_helper<'a>(&mut self) -> &'a mut T {
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe {
&mut *self.0.as_mut_ptr().cast::<T>()
}
}
}
impl<B, T> Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes,
{
/// Creates an immutable reference to `[T]` with a specific lifetime.
///
/// # Safety
///
/// `deref_slice_helper` has the same safety requirements as `deref_helper`.
unsafe fn deref_slice_helper<'a>(&self) -> &'a [T] {
let len = self.0.len();
let elem_size = mem::size_of::<T>();
debug_assert_ne!(elem_size, 0);
// `Ref<_, [T]>` maintains the invariant that `size_of::<T>() > 0`.
// Thus, neither the mod nor division operations here can panic.
#[allow(clippy::arithmetic_side_effects)]
let elems = {
debug_assert_eq!(len % elem_size, 0);
len / elem_size
};
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe {
slice::from_raw_parts(self.0.as_ptr().cast::<T>(), elems)
}
}
}
impl<B, T> Ref<B, [T]>
where
B: ByteSliceMut,
T: FromBytes + AsBytes,
{
/// Creates a mutable reference to `[T]` with a specific lifetime.
///
/// # Safety
///
/// `deref_mut_slice_helper` has the same safety requirements as
/// `deref_mut_helper`.
unsafe fn deref_mut_slice_helper<'a>(&mut self) -> &'a mut [T] {
let len = self.0.len();
let elem_size = mem::size_of::<T>();
debug_assert_ne!(elem_size, 0);
// `Ref<_, [T]>` maintains the invariant that `size_of::<T>() > 0`.
// Thus, neither the mod nor division operations here can panic.
#[allow(clippy::arithmetic_side_effects)]
let elems = {
debug_assert_eq!(len % elem_size, 0);
len / elem_size
};
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe {
slice::from_raw_parts_mut(self.0.as_mut_ptr().cast::<T>(), elems)
}
}
}
impl<B, T> Ref<B, T>
where
B: ByteSlice,
T: ?Sized,
{
/// Gets the underlying bytes.
#[inline]
pub fn bytes(&self) -> &[u8] {
&self.0
}
}
impl<B, T> Ref<B, T>
where
B: ByteSliceMut,
T: ?Sized,
{
/// Gets the underlying bytes mutably.
#[inline]
pub fn bytes_mut(&mut self) -> &mut [u8] {
&mut self.0
}
}
impl<B, T> Ref<B, T>
where
B: ByteSlice,
T: FromBytes,
{
/// Reads a copy of `T`.
#[inline]
pub fn read(&self) -> T {
// SAFETY: Because of the invariants on `Ref`, we know that `self.0` is
// at least `size_of::<T>()` bytes long, and that it is at least as
// aligned as `align_of::<T>()`. Because `T: FromBytes`, it is sound to
// interpret these bytes as a `T`.
unsafe { ptr::read(self.0.as_ptr().cast::<T>()) }
}
}
impl<B, T> Ref<B, T>
where
B: ByteSliceMut,
T: AsBytes,
{
/// Writes the bytes of `t` and then forgets `t`.
#[inline]
pub fn write(&mut self, t: T) {
// SAFETY: Because of the invariants on `Ref`, we know that `self.0` is
// at least `size_of::<T>()` bytes long, and that it is at least as
// aligned as `align_of::<T>()`. Writing `t` to the buffer will allow
// all of the bytes of `t` to be accessed as a `[u8]`, but because `T:
// AsBytes`, we know this is sound.
unsafe { ptr::write(self.0.as_mut_ptr().cast::<T>(), t) }
}
}
impl<B, T> Deref for Ref<B, T>
where
B: ByteSlice,
T: FromBytes,
{
type Target = T;
#[inline]
fn deref(&self) -> &T {
// SAFETY: This is sound because the lifetime of `self` is the same as
// the lifetime of the return value, meaning that a) the returned
// reference cannot outlive `self` and, b) no mutable methods on `self`
// can be called during the lifetime of the returned reference. See the
// documentation on `deref_helper` for what invariants we are required
// to uphold.
unsafe { self.deref_helper() }
}
}
impl<B, T> DerefMut for Ref<B, T>
where
B: ByteSliceMut,
T: FromBytes + AsBytes,
{
#[inline]
fn deref_mut(&mut self) -> &mut T {
// SAFETY: This is sound because the lifetime of `self` is the same as
// the lifetime of the return value, meaning that a) the returned
// reference cannot outlive `self` and, b) no other methods on `self`
// can be called during the lifetime of the returned reference. See the
// documentation on `deref_mut_helper` for what invariants we are
// required to uphold.
unsafe { self.deref_mut_helper() }
}
}
impl<B, T> Deref for Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes,
{
type Target = [T];
#[inline]
fn deref(&self) -> &[T] {
// SAFETY: This is sound because the lifetime of `self` is the same as
// the lifetime of the return value, meaning that a) the returned
// reference cannot outlive `self` and, b) no mutable methods on `self`
// can be called during the lifetime of the returned reference. See the
// documentation on `deref_slice_helper` for what invariants we are
// required to uphold.
unsafe { self.deref_slice_helper() }
}
}
impl<B, T> DerefMut for Ref<B, [T]>
where
B: ByteSliceMut,
T: FromBytes + AsBytes,
{
#[inline]
fn deref_mut(&mut self) -> &mut [T] {
// SAFETY: This is sound because the lifetime of `self` is the same as
// the lifetime of the return value, meaning that a) the returned
// reference cannot outlive `self` and, b) no other methods on `self`
// can be called during the lifetime of the returned reference. See the
// documentation on `deref_mut_slice_helper` for what invariants we are
// required to uphold.
unsafe { self.deref_mut_slice_helper() }
}
}
impl<T, B> Display for Ref<B, T>
where
B: ByteSlice,
T: FromBytes + Display,
{
#[inline]
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
let inner: &T = self;
inner.fmt(fmt)
}
}
impl<T, B> Display for Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes,
[T]: Display,
{
#[inline]
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
let inner: &[T] = self;
inner.fmt(fmt)
}
}
impl<T, B> Debug for Ref<B, T>
where
B: ByteSlice,
T: FromBytes + Debug,
{
#[inline]
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
let inner: &T = self;
fmt.debug_tuple("Ref").field(&inner).finish()
}
}
impl<T, B> Debug for Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes + Debug,
{
#[inline]
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
let inner: &[T] = self;
fmt.debug_tuple("Ref").field(&inner).finish()
}
}
impl<T, B> Eq for Ref<B, T>
where
B: ByteSlice,
T: FromBytes + Eq,
{
}
impl<T, B> Eq for Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes + Eq,
{
}
impl<T, B> PartialEq for Ref<B, T>
where
B: ByteSlice,
T: FromBytes + PartialEq,
{
#[inline]
fn eq(&self, other: &Self) -> bool {
self.deref().eq(other.deref())
}
}
impl<T, B> PartialEq for Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes + PartialEq,
{
#[inline]
fn eq(&self, other: &Self) -> bool {
self.deref().eq(other.deref())
}
}
impl<T, B> Ord for Ref<B, T>
where
B: ByteSlice,
T: FromBytes + Ord,
{
#[inline]
fn cmp(&self, other: &Self) -> Ordering {
let inner: &T = self;
let other_inner: &T = other;
inner.cmp(other_inner)
}
}
impl<T, B> Ord for Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes + Ord,
{
#[inline]
fn cmp(&self, other: &Self) -> Ordering {
let inner: &[T] = self;
let other_inner: &[T] = other;
inner.cmp(other_inner)
}
}
impl<T, B> PartialOrd for Ref<B, T>
where
B: ByteSlice,
T: FromBytes + PartialOrd,
{
#[inline]
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
let inner: &T = self;
let other_inner: &T = other;
inner.partial_cmp(other_inner)
}
}
impl<T, B> PartialOrd for Ref<B, [T]>
where
B: ByteSlice,
T: FromBytes + PartialOrd,
{
#[inline]
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
let inner: &[T] = self;
let other_inner: &[T] = other;
inner.partial_cmp(other_inner)
}
}
mod sealed {
pub trait ByteSliceSealed {}
}
// ByteSlice and ByteSliceMut abstract over [u8] references (&[u8], &mut [u8],
// Ref<[u8]>, RefMut<[u8]>, etc). We rely on various behaviors of these
// references such as that a given reference will never changes its length
// between calls to deref() or deref_mut(), and that split_at() works as
// expected. If ByteSlice or ByteSliceMut were not sealed, consumers could
// implement them in a way that violated these behaviors, and would break our
// unsafe code. Thus, we seal them and implement it only for known-good
// reference types. For the same reason, they're unsafe traits.
#[allow(clippy::missing_safety_doc)] // TODO(fxbug.dev/99068)
/// A mutable or immutable reference to a byte slice.
///
/// `ByteSlice` abstracts over the mutability of a byte slice reference, and is
/// implemented for various special reference types such as `Ref<[u8]>` and
/// `RefMut<[u8]>`.
///
/// Note that, while it would be technically possible, `ByteSlice` is not
/// implemented for [`Vec<u8>`], as the only way to implement the [`split_at`]
/// method would involve reallocation, and `split_at` must be a very cheap
/// operation in order for the utilities in this crate to perform as designed.
///
/// [`split_at`]: crate::ByteSlice::split_at
// It may seem overkill to go to this length to ensure that this doc link never
// breaks. We do this because it simplifies CI - it means that generating docs
// always succeeds, so we don't need special logic to only generate docs under
// certain features.
#[cfg_attr(feature = "alloc", doc = "[`Vec<u8>`]: alloc::vec::Vec")]
#[cfg_attr(
not(feature = "alloc"),
doc = "[`Vec<u8>`]: https://doc.rust-lang.org/std/vec/struct.Vec.html"
)]
pub unsafe trait ByteSlice: Deref<Target = [u8]> + Sized + sealed::ByteSliceSealed {
/// Are the [`Ref::into_ref`] and [`Ref::into_mut`] methods sound when used
/// with `Self`? If not, evaluating this constant must panic at compile
/// time.
///
/// This exists to work around #716 on versions of zerocopy prior to 0.8.
///
/// # Safety
///
/// This may only be set to true if the following holds: Given the
/// following:
/// - `Self: 'a`
/// - `bytes: Self`
/// - `let ptr = bytes.as_ptr()`
///
/// ...then:
/// - Using `ptr` to read the memory previously addressed by `bytes` is
/// sound for `'a` even after `bytes` has been dropped.
/// - If `Self: ByteSliceMut`, using `ptr` to write the memory previously
/// addressed by `bytes` is sound for `'a` even after `bytes` has been
/// dropped.
#[doc(hidden)]
const INTO_REF_INTO_MUT_ARE_SOUND: bool;
/// Gets a raw pointer to the first byte in the slice.
#[inline]
fn as_ptr(&self) -> *const u8 {
<[u8]>::as_ptr(self)
}
/// Splits the slice at the midpoint.
///
/// `x.split_at(mid)` returns `x[..mid]` and `x[mid..]`.
///
/// # Panics
///
/// `x.split_at(mid)` panics if `mid > x.len()`.
fn split_at(self, mid: usize) -> (Self, Self);
}
#[allow(clippy::missing_safety_doc)] // TODO(fxbug.dev/99068)
/// A mutable reference to a byte slice.
///
/// `ByteSliceMut` abstracts over various ways of storing a mutable reference to
/// a byte slice, and is implemented for various special reference types such as
/// `RefMut<[u8]>`.
pub unsafe trait ByteSliceMut: ByteSlice + DerefMut {
/// Gets a mutable raw pointer to the first byte in the slice.
#[inline]
fn as_mut_ptr(&mut self) -> *mut u8 {
<[u8]>::as_mut_ptr(self)
}
}
impl<'a> sealed::ByteSliceSealed for &'a [u8] {}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe impl<'a> ByteSlice for &'a [u8] {
// SAFETY: If `&'b [u8]: 'a`, then the underlying memory is treated as
// borrowed immutably for `'a` even if the slice itself is dropped.
const INTO_REF_INTO_MUT_ARE_SOUND: bool = true;
#[inline]
fn split_at(self, mid: usize) -> (Self, Self) {
<[u8]>::split_at(self, mid)
}
}
impl<'a> sealed::ByteSliceSealed for &'a mut [u8] {}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe impl<'a> ByteSlice for &'a mut [u8] {
// SAFETY: If `&'b mut [u8]: 'a`, then the underlying memory is treated as
// borrowed mutably for `'a` even if the slice itself is dropped.
const INTO_REF_INTO_MUT_ARE_SOUND: bool = true;
#[inline]
fn split_at(self, mid: usize) -> (Self, Self) {
<[u8]>::split_at_mut(self, mid)
}
}
impl<'a> sealed::ByteSliceSealed for cell::Ref<'a, [u8]> {}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe impl<'a> ByteSlice for cell::Ref<'a, [u8]> {
const INTO_REF_INTO_MUT_ARE_SOUND: bool = if !cfg!(doc) {
panic!("Ref::into_ref and Ref::into_mut are unsound when used with core::cell::Ref; see https://github.com/google/zerocopy/issues/716")
} else {
// When compiling documentation, allow the evaluation of this constant
// to succeed. This doesn't represent a soundness hole - it just delays
// any error to runtime. The reason we need this is that, otherwise,
// `rustdoc` will fail when trying to document this item.
false
};
#[inline]
fn split_at(self, mid: usize) -> (Self, Self) {
cell::Ref::map_split(self, |slice| <[u8]>::split_at(slice, mid))
}
}
impl<'a> sealed::ByteSliceSealed for RefMut<'a, [u8]> {}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe impl<'a> ByteSlice for RefMut<'a, [u8]> {
const INTO_REF_INTO_MUT_ARE_SOUND: bool = if !cfg!(doc) {
panic!("Ref::into_ref and Ref::into_mut are unsound when used with core::cell::RefMut; see https://github.com/google/zerocopy/issues/716")
} else {
// When compiling documentation, allow the evaluation of this constant
// to succeed. This doesn't represent a soundness hole - it just delays
// any error to runtime. The reason we need this is that, otherwise,
// `rustdoc` will fail when trying to document this item.
false
};
#[inline]
fn split_at(self, mid: usize) -> (Self, Self) {
RefMut::map_split(self, |slice| <[u8]>::split_at_mut(slice, mid))
}
}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe impl<'a> ByteSliceMut for &'a mut [u8] {}
// TODO(#429): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe impl<'a> ByteSliceMut for RefMut<'a, [u8]> {}
#[cfg(feature = "alloc")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
mod alloc_support {
use alloc::vec::Vec;
use super::*;
/// Extends a `Vec<T>` by pushing `additional` new items onto the end of the
/// vector. The new items are initialized with zeroes.
///
/// # Panics
///
/// Panics if `Vec::reserve(additional)` fails to reserve enough memory.
#[inline(always)]
pub fn extend_vec_zeroed<T: FromZeroes>(v: &mut Vec<T>, additional: usize) {
insert_vec_zeroed(v, v.len(), additional);
}
/// Inserts `additional` new items into `Vec<T>` at `position`.
/// The new items are initialized with zeroes.
///
/// # Panics
///
/// * Panics if `position > v.len()`.
/// * Panics if `Vec::reserve(additional)` fails to reserve enough memory.
#[inline]
pub fn insert_vec_zeroed<T: FromZeroes>(v: &mut Vec<T>, position: usize, additional: usize) {
assert!(position <= v.len());
v.reserve(additional);
// SAFETY: The `reserve` call guarantees that these cannot overflow:
// * `ptr.add(position)`
// * `position + additional`
// * `v.len() + additional`
//
// `v.len() - position` cannot overflow because we asserted that
// `position <= v.len()`.
unsafe {
// This is a potentially overlapping copy.
let ptr = v.as_mut_ptr();
#[allow(clippy::arithmetic_side_effects)]
ptr.add(position).copy_to(ptr.add(position + additional), v.len() - position);
ptr.add(position).write_bytes(0, additional);
#[allow(clippy::arithmetic_side_effects)]
v.set_len(v.len() + additional);
}
}
#[cfg(test)]
mod tests {
use core::convert::TryFrom as _;
use super::*;
#[test]
fn test_extend_vec_zeroed() {
// Test extending when there is an existing allocation.
let mut v = vec![100u64, 200, 300];
extend_vec_zeroed(&mut v, 3);
assert_eq!(v.len(), 6);
assert_eq!(&*v, &[100, 200, 300, 0, 0, 0]);
drop(v);
// Test extending when there is no existing allocation.
let mut v: Vec<u64> = Vec::new();
extend_vec_zeroed(&mut v, 3);
assert_eq!(v.len(), 3);
assert_eq!(&*v, &[0, 0, 0]);
drop(v);
}
#[test]
fn test_extend_vec_zeroed_zst() {
// Test extending when there is an existing (fake) allocation.
let mut v = vec![(), (), ()];
extend_vec_zeroed(&mut v, 3);
assert_eq!(v.len(), 6);
assert_eq!(&*v, &[(), (), (), (), (), ()]);
drop(v);
// Test extending when there is no existing (fake) allocation.
let mut v: Vec<()> = Vec::new();
extend_vec_zeroed(&mut v, 3);
assert_eq!(&*v, &[(), (), ()]);
drop(v);
}
#[test]
fn test_insert_vec_zeroed() {
// Insert at start (no existing allocation).
let mut v: Vec<u64> = Vec::new();
insert_vec_zeroed(&mut v, 0, 2);
assert_eq!(v.len(), 2);
assert_eq!(&*v, &[0, 0]);
drop(v);
// Insert at start.
let mut v = vec![100u64, 200, 300];
insert_vec_zeroed(&mut v, 0, 2);
assert_eq!(v.len(), 5);
assert_eq!(&*v, &[0, 0, 100, 200, 300]);
drop(v);
// Insert at middle.
let mut v = vec![100u64, 200, 300];
insert_vec_zeroed(&mut v, 1, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[100, 0, 200, 300]);
drop(v);
// Insert at end.
let mut v = vec![100u64, 200, 300];
insert_vec_zeroed(&mut v, 3, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[100, 200, 300, 0]);
drop(v);
}
#[test]
fn test_insert_vec_zeroed_zst() {
// Insert at start (no existing fake allocation).
let mut v: Vec<()> = Vec::new();
insert_vec_zeroed(&mut v, 0, 2);
assert_eq!(v.len(), 2);
assert_eq!(&*v, &[(), ()]);
drop(v);
// Insert at start.
let mut v = vec![(), (), ()];
insert_vec_zeroed(&mut v, 0, 2);
assert_eq!(v.len(), 5);
assert_eq!(&*v, &[(), (), (), (), ()]);
drop(v);
// Insert at middle.
let mut v = vec![(), (), ()];
insert_vec_zeroed(&mut v, 1, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[(), (), (), ()]);
drop(v);
// Insert at end.
let mut v = vec![(), (), ()];
insert_vec_zeroed(&mut v, 3, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[(), (), (), ()]);
drop(v);
}
#[test]
fn test_new_box_zeroed() {
assert_eq!(*u64::new_box_zeroed(), 0);
}
#[test]
fn test_new_box_zeroed_array() {
drop(<[u32; 0x1000]>::new_box_zeroed());
}
#[test]
fn test_new_box_zeroed_zst() {
// This test exists in order to exercise unsafe code, especially
// when running under Miri.
#[allow(clippy::unit_cmp)]
{
assert_eq!(*<()>::new_box_zeroed(), ());
}
}
#[test]
fn test_new_box_slice_zeroed() {
let mut s: Box<[u64]> = u64::new_box_slice_zeroed(3);
assert_eq!(s.len(), 3);
assert_eq!(&*s, &[0, 0, 0]);
s[1] = 3;
assert_eq!(&*s, &[0, 3, 0]);
}
#[test]
fn test_new_box_slice_zeroed_empty() {
let s: Box<[u64]> = u64::new_box_slice_zeroed(0);
assert_eq!(s.len(), 0);
}
#[test]
fn test_new_box_slice_zeroed_zst() {
let mut s: Box<[()]> = <()>::new_box_slice_zeroed(3);
assert_eq!(s.len(), 3);
assert!(s.get(10).is_none());
// This test exists in order to exercise unsafe code, especially
// when running under Miri.
#[allow(clippy::unit_cmp)]
{
assert_eq!(s[1], ());
}
s[2] = ();
}
#[test]
fn test_new_box_slice_zeroed_zst_empty() {
let s: Box<[()]> = <()>::new_box_slice_zeroed(0);
assert_eq!(s.len(), 0);
}
#[test]
#[should_panic(expected = "mem::size_of::<Self>() * len overflows `usize`")]
fn test_new_box_slice_zeroed_panics_mul_overflow() {
let _ = u16::new_box_slice_zeroed(usize::MAX);
}
#[test]
#[should_panic(expected = "assertion failed: size <= max_alloc")]
fn test_new_box_slice_zeroed_panics_isize_overflow() {
let max = usize::try_from(isize::MAX).unwrap();
let _ = u16::new_box_slice_zeroed((max / mem::size_of::<u16>()) + 1);
}
}
}
#[cfg(feature = "alloc")]
#[doc(inline)]
pub use alloc_support::*;
#[cfg(test)]
mod tests {
#![allow(clippy::unreadable_literal)]
use core::{cell::UnsafeCell, convert::TryInto as _, ops::Deref};
use static_assertions::assert_impl_all;
use super::*;
use crate::util::testutil::*;
// An unsized type.
//
// This is used to test the custom derives of our traits. The `[u8]` type
// gets a hand-rolled impl, so it doesn't exercise our custom derives.
#[derive(Debug, Eq, PartialEq, FromZeroes, FromBytes, AsBytes, Unaligned)]
#[repr(transparent)]
struct Unsized([u8]);
impl Unsized {
fn from_mut_slice(slc: &mut [u8]) -> &mut Unsized {
// SAFETY: This *probably* sound - since the layouts of `[u8]` and
// `Unsized` are the same, so are the layouts of `&mut [u8]` and
// `&mut Unsized`. [1] Even if it turns out that this isn't actually
// guaranteed by the language spec, we can just change this since
// it's in test code.
//
// [1] https://github.com/rust-lang/unsafe-code-guidelines/issues/375
unsafe { mem::transmute(slc) }
}
}
/// Tests of when a sized `DstLayout` is extended with a sized field.
#[allow(clippy::decimal_literal_representation)]
#[test]
fn test_dst_layout_extend_sized_with_sized() {
// This macro constructs a layout corresponding to a `u8` and extends it
// with a zero-sized trailing field of given alignment `n`. The macro
// tests that the resulting layout has both size and alignment `min(n,
// P)` for all valid values of `repr(packed(P))`.
macro_rules! test_align_is_size {
($n:expr) => {
let base = DstLayout::for_type::<u8>();
let trailing_field = DstLayout::for_type::<elain::Align<$n>>();
let packs =
core::iter::once(None).chain((0..29).map(|p| NonZeroUsize::new(2usize.pow(p))));
for pack in packs {
let composite = base.extend(trailing_field, pack);
let max_align = pack.unwrap_or(DstLayout::CURRENT_MAX_ALIGN);
let align = $n.min(max_align.get());
assert_eq!(
composite,
DstLayout {
align: NonZeroUsize::new(align).unwrap(),
size_info: SizeInfo::Sized { _size: align }
}
)
}
};
}
test_align_is_size!(1);
test_align_is_size!(2);
test_align_is_size!(4);
test_align_is_size!(8);
test_align_is_size!(16);
test_align_is_size!(32);
test_align_is_size!(64);
test_align_is_size!(128);
test_align_is_size!(256);
test_align_is_size!(512);
test_align_is_size!(1024);
test_align_is_size!(2048);
test_align_is_size!(4096);
test_align_is_size!(8192);
test_align_is_size!(16384);
test_align_is_size!(32768);
test_align_is_size!(65536);
test_align_is_size!(131072);
test_align_is_size!(262144);
test_align_is_size!(524288);
test_align_is_size!(1048576);
test_align_is_size!(2097152);
test_align_is_size!(4194304);
test_align_is_size!(8388608);
test_align_is_size!(16777216);
test_align_is_size!(33554432);
test_align_is_size!(67108864);
test_align_is_size!(33554432);
test_align_is_size!(134217728);
test_align_is_size!(268435456);
}
/// Tests of when a sized `DstLayout` is extended with a DST field.
#[test]
fn test_dst_layout_extend_sized_with_dst() {
// Test that for all combinations of real-world alignments and
// `repr_packed` values, that the extension of a sized `DstLayout`` with
// a DST field correctly computes the trailing offset in the composite
// layout.
let aligns = (0..29).map(|p| NonZeroUsize::new(2usize.pow(p)).unwrap());
let packs = core::iter::once(None).chain(aligns.clone().map(Some));
for align in aligns {
for pack in packs.clone() {
let base = DstLayout::for_type::<u8>();
let elem_size = 42;
let trailing_field_offset = 11;
let trailing_field = DstLayout {
align,
size_info: SizeInfo::SliceDst(TrailingSliceLayout {
_elem_size: elem_size,
_offset: 11,
}),
};
let composite = base.extend(trailing_field, pack);
let max_align = pack.unwrap_or(DstLayout::CURRENT_MAX_ALIGN).get();
let align = align.get().min(max_align);
assert_eq!(
composite,
DstLayout {
align: NonZeroUsize::new(align).unwrap(),
size_info: SizeInfo::SliceDst(TrailingSliceLayout {
_elem_size: elem_size,
_offset: align + trailing_field_offset,
}),
}
)
}
}
}
/// Tests that calling `pad_to_align` on a sized `DstLayout` adds the
/// expected amount of trailing padding.
#[test]
fn test_dst_layout_pad_to_align_with_sized() {
// For all valid alignments `align`, construct a one-byte layout aligned
// to `align`, call `pad_to_align`, and assert that the size of the
// resulting layout is equal to `align`.
for align in (0..29).map(|p| NonZeroUsize::new(2usize.pow(p)).unwrap()) {
let layout = DstLayout { align, size_info: SizeInfo::Sized { _size: 1 } };
assert_eq!(
layout.pad_to_align(),
DstLayout { align, size_info: SizeInfo::Sized { _size: align.get() } }
);
}
// Test explicitly-provided combinations of unpadded and padded
// counterparts.
macro_rules! test {
(unpadded { size: $unpadded_size:expr, align: $unpadded_align:expr }
=> padded { size: $padded_size:expr, align: $padded_align:expr }) => {
let unpadded = DstLayout {
align: NonZeroUsize::new($unpadded_align).unwrap(),
size_info: SizeInfo::Sized { _size: $unpadded_size },
};
let padded = unpadded.pad_to_align();
assert_eq!(
padded,
DstLayout {
align: NonZeroUsize::new($padded_align).unwrap(),
size_info: SizeInfo::Sized { _size: $padded_size },
}
);
};
}
test!(unpadded { size: 0, align: 4 } => padded { size: 0, align: 4 });
test!(unpadded { size: 1, align: 4 } => padded { size: 4, align: 4 });
test!(unpadded { size: 2, align: 4 } => padded { size: 4, align: 4 });
test!(unpadded { size: 3, align: 4 } => padded { size: 4, align: 4 });
test!(unpadded { size: 4, align: 4 } => padded { size: 4, align: 4 });
test!(unpadded { size: 5, align: 4 } => padded { size: 8, align: 4 });
test!(unpadded { size: 6, align: 4 } => padded { size: 8, align: 4 });
test!(unpadded { size: 7, align: 4 } => padded { size: 8, align: 4 });
test!(unpadded { size: 8, align: 4 } => padded { size: 8, align: 4 });
let current_max_align = DstLayout::CURRENT_MAX_ALIGN.get();
test!(unpadded { size: 1, align: current_max_align }
=> padded { size: current_max_align, align: current_max_align });
test!(unpadded { size: current_max_align + 1, align: current_max_align }
=> padded { size: current_max_align * 2, align: current_max_align });
}
/// Tests that calling `pad_to_align` on a DST `DstLayout` is a no-op.
#[test]
fn test_dst_layout_pad_to_align_with_dst() {
for align in (0..29).map(|p| NonZeroUsize::new(2usize.pow(p)).unwrap()) {
for offset in 0..10 {
for elem_size in 0..10 {
let layout = DstLayout {
align,
size_info: SizeInfo::SliceDst(TrailingSliceLayout {
_offset: offset,
_elem_size: elem_size,
}),
};
assert_eq!(layout.pad_to_align(), layout);
}
}
}
}
// This test takes a long time when running under Miri, so we skip it in
// that case. This is acceptable because this is a logic test that doesn't
// attempt to expose UB.
#[test]
#[cfg_attr(miri, ignore)]
fn testvalidate_cast_and_convert_metadata() {
impl From<usize> for SizeInfo {
fn from(_size: usize) -> SizeInfo {
SizeInfo::Sized { _size }
}
}
impl From<(usize, usize)> for SizeInfo {
fn from((_offset, _elem_size): (usize, usize)) -> SizeInfo {
SizeInfo::SliceDst(TrailingSliceLayout { _offset, _elem_size })
}
}
fn layout<S: Into<SizeInfo>>(s: S, align: usize) -> DstLayout {
DstLayout { size_info: s.into(), align: NonZeroUsize::new(align).unwrap() }
}
/// This macro accepts arguments in the form of:
///
/// layout(_, _, _).validate(_, _, _), Ok(Some((_, _)))
/// | | | | | | | |
/// base_size ----+ | | | | | | |
/// align -----------+ | | | | | |
/// trailing_size ------+ | | | | |
/// addr ---------------------------+ | | | |
/// bytes_len -------------------------+ | | |
/// cast_type ----------------------------+ | |
/// elems ---------------------------------------------+ |
/// split_at ---------------------------------------------+
///
/// `.validate` is shorthand for `.validate_cast_and_convert_metadata`
/// for brevity.
///
/// Each argument can either be an iterator or a wildcard. Each
/// wildcarded variable is implicitly replaced by an iterator over a
/// representative sample of values for that variable. Each `test!`
/// invocation iterates over every combination of values provided by
/// each variable's iterator (ie, the cartesian product) and validates
/// that the results are expected.
///
/// The final argument uses the same syntax, but it has a different
/// meaning:
/// - If it is `Ok(pat)`, then the pattern `pat` is supplied to
/// `assert_matches!` to validate the computed result for each
/// combination of input values.
/// - If it is `Err(msg)`, then `test!` validates that the call to
/// `validate_cast_and_convert_metadata` panics with the given panic
/// message.
///
/// Note that the meta-variables that match these variables have the
/// `tt` type, and some valid expressions are not valid `tt`s (such as
/// `a..b`). In this case, wrap the expression in parentheses, and it
/// will become valid `tt`.
macro_rules! test {
($(:$sizes:expr =>)?
layout($size:tt, $align:tt)
.validate($addr:tt, $bytes_len:tt, $cast_type:tt), $expect:pat $(,)?
) => {
itertools::iproduct!(
test!(@generate_size $size),
test!(@generate_align $align),
test!(@generate_usize $addr),
test!(@generate_usize $bytes_len),
test!(@generate_cast_type $cast_type)
).for_each(|(size_info, align, addr, bytes_len, cast_type)| {
// Temporarily disable the panic hook installed by the test
// harness. If we don't do this, all panic messages will be
// kept in an internal log. On its own, this isn't a
// problem, but if a non-caught panic ever happens (ie, in
// code later in this test not in this macro), all of the
// previously-buffered messages will be dumped, hiding the
// real culprit.
let previous_hook = std::panic::take_hook();
// I don't understand why, but this seems to be required in
// addition to the previous line.
std::panic::set_hook(Box::new(|_| {}));
let actual = std::panic::catch_unwind(|| {
layout(size_info, align).validate_cast_and_convert_metadata(addr, bytes_len, cast_type)
}).map_err(|d| {
*d.downcast::<&'static str>().expect("expected string panic message").as_ref()
});
std::panic::set_hook(previous_hook);
assert_matches::assert_matches!(
actual, $expect,
"layout({size_info:?}, {align}).validate_cast_and_convert_metadata({addr}, {bytes_len}, {cast_type:?})",
);
});
};
(@generate_usize _) => { 0..8 };
// Generate sizes for both Sized and !Sized types.
(@generate_size _) => {
test!(@generate_size (_)).chain(test!(@generate_size (_, _)))
};
// Generate sizes for both Sized and !Sized types by chaining
// specified iterators for each.
(@generate_size ($sized_sizes:tt | $unsized_sizes:tt)) => {
test!(@generate_size ($sized_sizes)).chain(test!(@generate_size $unsized_sizes))
};
// Generate sizes for Sized types.
(@generate_size (_)) => { test!(@generate_size (0..8)) };
(@generate_size ($sizes:expr)) => { $sizes.into_iter().map(Into::<SizeInfo>::into) };
// Generate sizes for !Sized types.
(@generate_size ($min_sizes:tt, $elem_sizes:tt)) => {
itertools::iproduct!(
test!(@generate_min_size $min_sizes),
test!(@generate_elem_size $elem_sizes)
).map(Into::<SizeInfo>::into)
};
(@generate_fixed_size _) => { (0..8).into_iter().map(Into::<SizeInfo>::into) };
(@generate_min_size _) => { 0..8 };
(@generate_elem_size _) => { 1..8 };
(@generate_align _) => { [1, 2, 4, 8, 16] };
(@generate_opt_usize _) => { [None].into_iter().chain((0..8).map(Some).into_iter()) };
(@generate_cast_type _) => { [_CastType::_Prefix, _CastType::_Suffix] };
(@generate_cast_type $variant:ident) => { [_CastType::$variant] };
// Some expressions need to be wrapped in parentheses in order to be
// valid `tt`s (required by the top match pattern). See the comment
// below for more details. This arm removes these parentheses to
// avoid generating an `unused_parens` warning.
(@$_:ident ($vals:expr)) => { $vals };
(@$_:ident $vals:expr) => { $vals };
}
const EVENS: [usize; 8] = [0, 2, 4, 6, 8, 10, 12, 14];
const ODDS: [usize; 8] = [1, 3, 5, 7, 9, 11, 13, 15];
// base_size is too big for the memory region.
test!(layout(((1..8) | ((1..8), (1..8))), _).validate(_, [0], _), Ok(None));
test!(layout(((2..8) | ((2..8), (2..8))), _).validate(_, [1], _), Ok(None));
// addr is unaligned for prefix cast
test!(layout(_, [2]).validate(ODDS, _, _Prefix), Ok(None));
test!(layout(_, [2]).validate(ODDS, _, _Prefix), Ok(None));
// addr is aligned, but end of buffer is unaligned for suffix cast
test!(layout(_, [2]).validate(EVENS, ODDS, _Suffix), Ok(None));
test!(layout(_, [2]).validate(EVENS, ODDS, _Suffix), Ok(None));
// Unfortunately, these constants cannot easily be used in the
// implementation of `validate_cast_and_convert_metadata`, since
// `panic!` consumes a string literal, not an expression.
//
// It's important that these messages be in a separate module. If they
// were at the function's top level, we'd pass them to `test!` as, e.g.,
// `Err(TRAILING)`, which would run into a subtle Rust footgun - the
// `TRAILING` identifier would be treated as a pattern to match rather
// than a value to check for equality.
mod msgs {
pub(super) const TRAILING: &str =
"attempted to cast to slice type with zero-sized element";
pub(super) const OVERFLOW: &str = "`addr` + `bytes_len` > usize::MAX";
}
// casts with ZST trailing element types are unsupported
test!(layout((_, [0]), _).validate(_, _, _), Err(msgs::TRAILING),);
// addr + bytes_len must not overflow usize
test!(layout(_, _).validate([usize::MAX], (1..100), _), Err(msgs::OVERFLOW));
test!(layout(_, _).validate((1..100), [usize::MAX], _), Err(msgs::OVERFLOW));
test!(
layout(_, _).validate(
[usize::MAX / 2 + 1, usize::MAX],
[usize::MAX / 2 + 1, usize::MAX],
_
),
Err(msgs::OVERFLOW)
);
// Validates that `validate_cast_and_convert_metadata` satisfies its own
// documented safety postconditions, and also a few other properties
// that aren't documented but we want to guarantee anyway.
fn validate_behavior(
(layout, addr, bytes_len, cast_type): (DstLayout, usize, usize, _CastType),
) {
if let Some((elems, split_at)) =
layout.validate_cast_and_convert_metadata(addr, bytes_len, cast_type)
{
let (size_info, align) = (layout.size_info, layout.align);
let debug_str = format!(
"layout({size_info:?}, {align}).validate_cast_and_convert_metadata({addr}, {bytes_len}, {cast_type:?}) => ({elems}, {split_at})",
);
// If this is a sized type (no trailing slice), then `elems` is
// meaningless, but in practice we set it to 0. Callers are not
// allowed to rely on this, but a lot of math is nicer if
// they're able to, and some callers might accidentally do that.
let sized = matches!(layout.size_info, SizeInfo::Sized { .. });
assert!(!(sized && elems != 0), "{}", debug_str);
let resulting_size = match layout.size_info {
SizeInfo::Sized { _size } => _size,
SizeInfo::SliceDst(TrailingSliceLayout {
_offset: offset,
_elem_size: elem_size,
}) => {
let padded_size = |elems| {
let without_padding = offset + elems * elem_size;
without_padding
+ util::core_layout::padding_needed_for(without_padding, align)
};
let resulting_size = padded_size(elems);
// Test that `validate_cast_and_convert_metadata`
// computed the largest possible value that fits in the
// given range.
assert!(padded_size(elems + 1) > bytes_len, "{}", debug_str);
resulting_size
}
};
// Test safety postconditions guaranteed by
// `validate_cast_and_convert_metadata`.
assert!(resulting_size <= bytes_len, "{}", debug_str);
match cast_type {
_CastType::_Prefix => {
assert_eq!(addr % align, 0, "{}", debug_str);
assert_eq!(resulting_size, split_at, "{}", debug_str);
}
_CastType::_Suffix => {
assert_eq!(split_at, bytes_len - resulting_size, "{}", debug_str);
assert_eq!((addr + split_at) % align, 0, "{}", debug_str);
}
}
} else {
let min_size = match layout.size_info {
SizeInfo::Sized { _size } => _size,
SizeInfo::SliceDst(TrailingSliceLayout { _offset, .. }) => {
_offset + util::core_layout::padding_needed_for(_offset, layout.align)
}
};
// If a cast is invalid, it is either because...
// 1. there are insufficent bytes at the given region for type:
let insufficient_bytes = bytes_len < min_size;
// 2. performing the cast would misalign type:
let base = match cast_type {
_CastType::_Prefix => 0,
_CastType::_Suffix => bytes_len,
};
let misaligned = (base + addr) % layout.align != 0;
assert!(insufficient_bytes || misaligned);
}
}
let sizes = 0..8;
let elem_sizes = 1..8;
let size_infos = sizes
.clone()
.map(Into::<SizeInfo>::into)
.chain(itertools::iproduct!(sizes, elem_sizes).map(Into::<SizeInfo>::into));
let layouts = itertools::iproduct!(size_infos, [1, 2, 4, 8, 16, 32])
.filter(|(size_info, align)| !matches!(size_info, SizeInfo::Sized { _size } if _size % align != 0))
.map(|(size_info, align)| layout(size_info, align));
itertools::iproduct!(layouts, 0..8, 0..8, [_CastType::_Prefix, _CastType::_Suffix])
.for_each(validate_behavior);
}
#[test]
#[cfg(__INTERNAL_USE_ONLY_NIGHLTY_FEATURES_IN_TESTS)]
fn test_validate_rust_layout() {
use core::ptr::NonNull;
// This test synthesizes pointers with various metadata and uses Rust's
// built-in APIs to confirm that Rust makes decisions about type layout
// which are consistent with what we believe is guaranteed by the
// language. If this test fails, it doesn't just mean our code is wrong
// - it means we're misunderstanding the language's guarantees.
#[derive(Debug)]
struct MacroArgs {
offset: usize,
align: NonZeroUsize,
elem_size: Option<usize>,
}
/// # Safety
///
/// `test` promises to only call `addr_of_slice_field` on a `NonNull<T>`
/// which points to a valid `T`.
///
/// `with_elems` must produce a pointer which points to a valid `T`.
fn test<T: ?Sized, W: Fn(usize) -> NonNull<T>>(
args: MacroArgs,
with_elems: W,
addr_of_slice_field: Option<fn(NonNull<T>) -> NonNull<u8>>,
) {
let dst = args.elem_size.is_some();
let layout = {
let size_info = match args.elem_size {
Some(elem_size) => SizeInfo::SliceDst(TrailingSliceLayout {
_offset: args.offset,
_elem_size: elem_size,
}),
None => SizeInfo::Sized {
// Rust only supports types whose sizes are a multiple
// of their alignment. If the macro created a type like
// this:
//
// #[repr(C, align(2))]
// struct Foo([u8; 1]);
//
// ...then Rust will automatically round the type's size
// up to 2.
_size: args.offset
+ util::core_layout::padding_needed_for(args.offset, args.align),
},
};
DstLayout { size_info, align: args.align }
};
for elems in 0..128 {
let ptr = with_elems(elems);
if let Some(addr_of_slice_field) = addr_of_slice_field {
let slc_field_ptr = addr_of_slice_field(ptr).as_ptr();
// SAFETY: Both `slc_field_ptr` and `ptr` are pointers to
// the same valid Rust object.
let offset: usize =
unsafe { slc_field_ptr.byte_offset_from(ptr.as_ptr()).try_into().unwrap() };
assert_eq!(offset, args.offset);
}
// SAFETY: `ptr` points to a valid `T`.
let (size, align) = unsafe {
(mem::size_of_val_raw(ptr.as_ptr()), mem::align_of_val_raw(ptr.as_ptr()))
};
// Avoid expensive allocation when running under Miri.
let assert_msg = if !cfg!(miri) {
format!("\n{args:?}\nsize:{size}, align:{align}")
} else {
String::new()
};
let without_padding =
args.offset + args.elem_size.map(|elem_size| elems * elem_size).unwrap_or(0);
assert!(size >= without_padding, "{}", assert_msg);
assert_eq!(align, args.align.get(), "{}", assert_msg);
// This encodes the most important part of the test: our
// understanding of how Rust determines the layout of repr(C)
// types. Sized repr(C) types are trivial, but DST types have
// some subtlety. Note that:
// - For sized types, `without_padding` is just the size of the
// type that we constructed for `Foo`. Since we may have
// requested a larger alignment, `Foo` may actually be larger
// than this, hence `padding_needed_for`.
// - For unsized types, `without_padding` is dynamically
// computed from the offset, the element size, and element
// count. We expect that the size of the object should be
// `offset + elem_size * elems` rounded up to the next
// alignment.
let expected_size = without_padding
+ util::core_layout::padding_needed_for(without_padding, args.align);
assert_eq!(expected_size, size, "{}", assert_msg);
// For zero-sized element types,
// `validate_cast_and_convert_metadata` just panics, so we skip
// testing those types.
if args.elem_size.map(|elem_size| elem_size > 0).unwrap_or(true) {
let addr = ptr.addr().get();
let (got_elems, got_split_at) = layout
.validate_cast_and_convert_metadata(addr, size, _CastType::_Prefix)
.unwrap();
// Avoid expensive allocation when running under Miri.
let assert_msg = if !cfg!(miri) {
format!(
"{}\nvalidate_cast_and_convert_metadata({addr}, {size})",
assert_msg
)
} else {
String::new()
};
assert_eq!(got_split_at, size, "{}", assert_msg);
if dst {
assert!(got_elems >= elems, "{}", assert_msg);
if got_elems != elems {
// If `validate_cast_and_convert_metadata`
// returned more elements than `elems`, that
// means that `elems` is not the maximum number
// of elements that can fit in `size` - in other
// words, there is enough padding at the end of
// the value to fit at least one more element.
// If we use this metadata to synthesize a
// pointer, despite having a different element
// count, we still expect it to have the same
// size.
let got_ptr = with_elems(got_elems);
// SAFETY: `got_ptr` is a pointer to a valid `T`.
let size_of_got_ptr = unsafe { mem::size_of_val_raw(got_ptr.as_ptr()) };
assert_eq!(size_of_got_ptr, size, "{}", assert_msg);
}
} else {
// For sized casts, the returned element value is
// technically meaningless, and we don't guarantee any
// particular value. In practice, it's always zero.
assert_eq!(got_elems, 0, "{}", assert_msg)
}
}
}
}
macro_rules! validate_against_rust {
($offset:literal, $align:literal $(, $elem_size:literal)?) => {{
#[repr(C, align($align))]
struct Foo([u8; $offset]$(, [[u8; $elem_size]])?);
let args = MacroArgs {
offset: $offset,
align: $align.try_into().unwrap(),
elem_size: {
#[allow(unused)]
let ret = None::<usize>;
$(let ret = Some($elem_size);)?
ret
}
};
#[repr(C, align($align))]
struct FooAlign;
// Create an aligned buffer to use in order to synthesize
// pointers to `Foo`. We don't ever load values from these
// pointers - we just do arithmetic on them - so having a "real"
// block of memory as opposed to a validly-aligned-but-dangling
// pointer is only necessary to make Miri happy since we run it
// with "strict provenance" checking enabled.
let aligned_buf = Align::<_, FooAlign>::new([0u8; 1024]);
let with_elems = |elems| {
let slc = NonNull::slice_from_raw_parts(NonNull::from(&aligned_buf.t), elems);
#[allow(clippy::as_conversions)]
NonNull::new(slc.as_ptr() as *mut Foo).unwrap()
};
let addr_of_slice_field = {
#[allow(unused)]
let f = None::<fn(NonNull<Foo>) -> NonNull<u8>>;
$(
// SAFETY: `test` promises to only call `f` with a `ptr`
// to a valid `Foo`.
let f: Option<fn(NonNull<Foo>) -> NonNull<u8>> = Some(|ptr: NonNull<Foo>| unsafe {
NonNull::new(ptr::addr_of_mut!((*ptr.as_ptr()).1)).unwrap().cast::<u8>()
});
let _ = $elem_size;
)?
f
};
test::<Foo, _>(args, with_elems, addr_of_slice_field);
}};
}
// Every permutation of:
// - offset in [0, 4]
// - align in [1, 16]
// - elem_size in [0, 4] (plus no elem_size)
validate_against_rust!(0, 1);
validate_against_rust!(0, 1, 0);
validate_against_rust!(0, 1, 1);
validate_against_rust!(0, 1, 2);
validate_against_rust!(0, 1, 3);
validate_against_rust!(0, 1, 4);
validate_against_rust!(0, 2);
validate_against_rust!(0, 2, 0);
validate_against_rust!(0, 2, 1);
validate_against_rust!(0, 2, 2);
validate_against_rust!(0, 2, 3);
validate_against_rust!(0, 2, 4);
validate_against_rust!(0, 4);
validate_against_rust!(0, 4, 0);
validate_against_rust!(0, 4, 1);
validate_against_rust!(0, 4, 2);
validate_against_rust!(0, 4, 3);
validate_against_rust!(0, 4, 4);
validate_against_rust!(0, 8);
validate_against_rust!(0, 8, 0);
validate_against_rust!(0, 8, 1);
validate_against_rust!(0, 8, 2);
validate_against_rust!(0, 8, 3);
validate_against_rust!(0, 8, 4);
validate_against_rust!(0, 16);
validate_against_rust!(0, 16, 0);
validate_against_rust!(0, 16, 1);
validate_against_rust!(0, 16, 2);
validate_against_rust!(0, 16, 3);
validate_against_rust!(0, 16, 4);
validate_against_rust!(1, 1);
validate_against_rust!(1, 1, 0);
validate_against_rust!(1, 1, 1);
validate_against_rust!(1, 1, 2);
validate_against_rust!(1, 1, 3);
validate_against_rust!(1, 1, 4);
validate_against_rust!(1, 2);
validate_against_rust!(1, 2, 0);
validate_against_rust!(1, 2, 1);
validate_against_rust!(1, 2, 2);
validate_against_rust!(1, 2, 3);
validate_against_rust!(1, 2, 4);
validate_against_rust!(1, 4);
validate_against_rust!(1, 4, 0);
validate_against_rust!(1, 4, 1);
validate_against_rust!(1, 4, 2);
validate_against_rust!(1, 4, 3);
validate_against_rust!(1, 4, 4);
validate_against_rust!(1, 8);
validate_against_rust!(1, 8, 0);
validate_against_rust!(1, 8, 1);
validate_against_rust!(1, 8, 2);
validate_against_rust!(1, 8, 3);
validate_against_rust!(1, 8, 4);
validate_against_rust!(1, 16);
validate_against_rust!(1, 16, 0);
validate_against_rust!(1, 16, 1);
validate_against_rust!(1, 16, 2);
validate_against_rust!(1, 16, 3);
validate_against_rust!(1, 16, 4);
validate_against_rust!(2, 1);
validate_against_rust!(2, 1, 0);
validate_against_rust!(2, 1, 1);
validate_against_rust!(2, 1, 2);
validate_against_rust!(2, 1, 3);
validate_against_rust!(2, 1, 4);
validate_against_rust!(2, 2);
validate_against_rust!(2, 2, 0);
validate_against_rust!(2, 2, 1);
validate_against_rust!(2, 2, 2);
validate_against_rust!(2, 2, 3);
validate_against_rust!(2, 2, 4);
validate_against_rust!(2, 4);
validate_against_rust!(2, 4, 0);
validate_against_rust!(2, 4, 1);
validate_against_rust!(2, 4, 2);
validate_against_rust!(2, 4, 3);
validate_against_rust!(2, 4, 4);
validate_against_rust!(2, 8);
validate_against_rust!(2, 8, 0);
validate_against_rust!(2, 8, 1);
validate_against_rust!(2, 8, 2);
validate_against_rust!(2, 8, 3);
validate_against_rust!(2, 8, 4);
validate_against_rust!(2, 16);
validate_against_rust!(2, 16, 0);
validate_against_rust!(2, 16, 1);
validate_against_rust!(2, 16, 2);
validate_against_rust!(2, 16, 3);
validate_against_rust!(2, 16, 4);
validate_against_rust!(3, 1);
validate_against_rust!(3, 1, 0);
validate_against_rust!(3, 1, 1);
validate_against_rust!(3, 1, 2);
validate_against_rust!(3, 1, 3);
validate_against_rust!(3, 1, 4);
validate_against_rust!(3, 2);
validate_against_rust!(3, 2, 0);
validate_against_rust!(3, 2, 1);
validate_against_rust!(3, 2, 2);
validate_against_rust!(3, 2, 3);
validate_against_rust!(3, 2, 4);
validate_against_rust!(3, 4);
validate_against_rust!(3, 4, 0);
validate_against_rust!(3, 4, 1);
validate_against_rust!(3, 4, 2);
validate_against_rust!(3, 4, 3);
validate_against_rust!(3, 4, 4);
validate_against_rust!(3, 8);
validate_against_rust!(3, 8, 0);
validate_against_rust!(3, 8, 1);
validate_against_rust!(3, 8, 2);
validate_against_rust!(3, 8, 3);
validate_against_rust!(3, 8, 4);
validate_against_rust!(3, 16);
validate_against_rust!(3, 16, 0);
validate_against_rust!(3, 16, 1);
validate_against_rust!(3, 16, 2);
validate_against_rust!(3, 16, 3);
validate_against_rust!(3, 16, 4);
validate_against_rust!(4, 1);
validate_against_rust!(4, 1, 0);
validate_against_rust!(4, 1, 1);
validate_against_rust!(4, 1, 2);
validate_against_rust!(4, 1, 3);
validate_against_rust!(4, 1, 4);
validate_against_rust!(4, 2);
validate_against_rust!(4, 2, 0);
validate_against_rust!(4, 2, 1);
validate_against_rust!(4, 2, 2);
validate_against_rust!(4, 2, 3);
validate_against_rust!(4, 2, 4);
validate_against_rust!(4, 4);
validate_against_rust!(4, 4, 0);
validate_against_rust!(4, 4, 1);
validate_against_rust!(4, 4, 2);
validate_against_rust!(4, 4, 3);
validate_against_rust!(4, 4, 4);
validate_against_rust!(4, 8);
validate_against_rust!(4, 8, 0);
validate_against_rust!(4, 8, 1);
validate_against_rust!(4, 8, 2);
validate_against_rust!(4, 8, 3);
validate_against_rust!(4, 8, 4);
validate_against_rust!(4, 16);
validate_against_rust!(4, 16, 0);
validate_against_rust!(4, 16, 1);
validate_against_rust!(4, 16, 2);
validate_against_rust!(4, 16, 3);
validate_against_rust!(4, 16, 4);
}
#[test]
fn test_known_layout() {
// Test that `$ty` and `ManuallyDrop<$ty>` have the expected layout.
// Test that `PhantomData<$ty>` has the same layout as `()` regardless
// of `$ty`.
macro_rules! test {
($ty:ty, $expect:expr) => {
let expect = $expect;
assert_eq!(<$ty as KnownLayout>::LAYOUT, expect);
assert_eq!(<ManuallyDrop<$ty> as KnownLayout>::LAYOUT, expect);
assert_eq!(<PhantomData<$ty> as KnownLayout>::LAYOUT, <() as KnownLayout>::LAYOUT);
};
}
let layout = |offset, align, _trailing_slice_elem_size| DstLayout {
align: NonZeroUsize::new(align).unwrap(),
size_info: match _trailing_slice_elem_size {
None => SizeInfo::Sized { _size: offset },
Some(elem_size) => SizeInfo::SliceDst(TrailingSliceLayout {
_offset: offset,
_elem_size: elem_size,
}),
},
};
test!((), layout(0, 1, None));
test!(u8, layout(1, 1, None));
// Use `align_of` because `u64` alignment may be smaller than 8 on some
// platforms.
test!(u64, layout(8, mem::align_of::<u64>(), None));
test!(AU64, layout(8, 8, None));
test!(Option<&'static ()>, usize::LAYOUT);
test!([()], layout(0, 1, Some(0)));
test!([u8], layout(0, 1, Some(1)));
test!(str, layout(0, 1, Some(1)));
}
#[cfg(feature = "derive")]
#[test]
fn test_known_layout_derive() {
// In this and other files (`late_compile_pass.rs`,
// `mid_compile_pass.rs`, and `struct.rs`), we test success and failure
// modes of `derive(KnownLayout)` for the following combination of
// properties:
//
// +------------+--------------------------------------+-----------+
// | | trailing field properties | |
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// |------------+----------+----------------+----------+-----------|
// | N | N | N | N | KL00 |
// | N | N | N | Y | KL01 |
// | N | N | Y | N | KL02 |
// | N | N | Y | Y | KL03 |
// | N | Y | N | N | KL04 |
// | N | Y | N | Y | KL05 |
// | N | Y | Y | N | KL06 |
// | N | Y | Y | Y | KL07 |
// | Y | N | N | N | KL08 |
// | Y | N | N | Y | KL09 |
// | Y | N | Y | N | KL10 |
// | Y | N | Y | Y | KL11 |
// | Y | Y | N | N | KL12 |
// | Y | Y | N | Y | KL13 |
// | Y | Y | Y | N | KL14 |
// | Y | Y | Y | Y | KL15 |
// +------------+----------+----------------+----------+-----------+
struct NotKnownLayout<T = ()> {
_t: T,
}
#[derive(KnownLayout)]
#[repr(C)]
struct AlignSize<const ALIGN: usize, const SIZE: usize>
where
elain::Align<ALIGN>: elain::Alignment,
{
_align: elain::Align<ALIGN>,
_size: [u8; SIZE],
}
type AU16 = AlignSize<2, 2>;
type AU32 = AlignSize<4, 4>;
fn _assert_kl<T: ?Sized + KnownLayout>(_: &T) {}
let sized_layout = |align, size| DstLayout {
align: NonZeroUsize::new(align).unwrap(),
size_info: SizeInfo::Sized { _size: size },
};
let unsized_layout = |align, elem_size, offset| DstLayout {
align: NonZeroUsize::new(align).unwrap(),
size_info: SizeInfo::SliceDst(TrailingSliceLayout {
_offset: offset,
_elem_size: elem_size,
}),
};
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | N | N | N | Y | KL01 |
#[derive(KnownLayout)]
#[allow(dead_code)] // fields are never read
struct KL01(NotKnownLayout<AU32>, NotKnownLayout<AU16>);
let expected = DstLayout::for_type::<KL01>();
assert_eq!(<KL01 as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL01 as KnownLayout>::LAYOUT, sized_layout(4, 8));
// ...with `align(N)`:
#[derive(KnownLayout)]
#[repr(align(64))]
#[allow(dead_code)] // fields are never read
struct KL01Align(NotKnownLayout<AU32>, NotKnownLayout<AU16>);
let expected = DstLayout::for_type::<KL01Align>();
assert_eq!(<KL01Align as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL01Align as KnownLayout>::LAYOUT, sized_layout(64, 64));
// ...with `packed`:
#[derive(KnownLayout)]
#[repr(packed)]
#[allow(dead_code)] // fields are never read
struct KL01Packed(NotKnownLayout<AU32>, NotKnownLayout<AU16>);
let expected = DstLayout::for_type::<KL01Packed>();
assert_eq!(<KL01Packed as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL01Packed as KnownLayout>::LAYOUT, sized_layout(1, 6));
// ...with `packed(N)`:
#[derive(KnownLayout)]
#[repr(packed(2))]
#[allow(dead_code)] // fields are never read
struct KL01PackedN(NotKnownLayout<AU32>, NotKnownLayout<AU16>);
assert_impl_all!(KL01PackedN: KnownLayout);
let expected = DstLayout::for_type::<KL01PackedN>();
assert_eq!(<KL01PackedN as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL01PackedN as KnownLayout>::LAYOUT, sized_layout(2, 6));
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | N | N | Y | Y | KL03 |
#[derive(KnownLayout)]
#[allow(dead_code)] // fields are never read
struct KL03(NotKnownLayout, u8);
let expected = DstLayout::for_type::<KL03>();
assert_eq!(<KL03 as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL03 as KnownLayout>::LAYOUT, sized_layout(1, 1));
// ... with `align(N)`
#[derive(KnownLayout)]
#[repr(align(64))]
#[allow(dead_code)] // fields are never read
struct KL03Align(NotKnownLayout<AU32>, u8);
let expected = DstLayout::for_type::<KL03Align>();
assert_eq!(<KL03Align as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL03Align as KnownLayout>::LAYOUT, sized_layout(64, 64));
// ... with `packed`:
#[derive(KnownLayout)]
#[repr(packed)]
#[allow(dead_code)] // fields are never read
struct KL03Packed(NotKnownLayout<AU32>, u8);
let expected = DstLayout::for_type::<KL03Packed>();
assert_eq!(<KL03Packed as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL03Packed as KnownLayout>::LAYOUT, sized_layout(1, 5));
// ... with `packed(N)`
#[derive(KnownLayout)]
#[repr(packed(2))]
#[allow(dead_code)] // fields are never read
struct KL03PackedN(NotKnownLayout<AU32>, u8);
assert_impl_all!(KL03PackedN: KnownLayout);
let expected = DstLayout::for_type::<KL03PackedN>();
assert_eq!(<KL03PackedN as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL03PackedN as KnownLayout>::LAYOUT, sized_layout(2, 6));
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | N | Y | N | Y | KL05 |
#[derive(KnownLayout)]
#[allow(dead_code)] // fields are never read
struct KL05<T>(u8, T);
fn _test_kl05<T>(t: T) -> impl KnownLayout {
KL05(0u8, t)
}
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | N | Y | Y | Y | KL07 |
#[derive(KnownLayout)]
#[allow(dead_code)] // fields are never read
struct KL07<T: KnownLayout>(u8, T);
fn _test_kl07<T: KnownLayout>(t: T) -> impl KnownLayout {
let _ = KL07(0u8, t);
}
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | Y | N | Y | N | KL10 |
#[derive(KnownLayout)]
#[repr(C)]
struct KL10(NotKnownLayout<AU32>, [u8]);
let expected = DstLayout::new_zst(None)
.extend(DstLayout::for_type::<NotKnownLayout<AU32>>(), None)
.extend(<[u8] as KnownLayout>::LAYOUT, None)
.pad_to_align();
assert_eq!(<KL10 as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL10 as KnownLayout>::LAYOUT, unsized_layout(4, 1, 4));
// ...with `align(N)`:
#[derive(KnownLayout)]
#[repr(C, align(64))]
struct KL10Align(NotKnownLayout<AU32>, [u8]);
let repr_align = NonZeroUsize::new(64);
let expected = DstLayout::new_zst(repr_align)
.extend(DstLayout::for_type::<NotKnownLayout<AU32>>(), None)
.extend(<[u8] as KnownLayout>::LAYOUT, None)
.pad_to_align();
assert_eq!(<KL10Align as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL10Align as KnownLayout>::LAYOUT, unsized_layout(64, 1, 4));
// ...with `packed`:
#[derive(KnownLayout)]
#[repr(C, packed)]
struct KL10Packed(NotKnownLayout<AU32>, [u8]);
let repr_packed = NonZeroUsize::new(1);
let expected = DstLayout::new_zst(None)
.extend(DstLayout::for_type::<NotKnownLayout<AU32>>(), repr_packed)
.extend(<[u8] as KnownLayout>::LAYOUT, repr_packed)
.pad_to_align();
assert_eq!(<KL10Packed as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL10Packed as KnownLayout>::LAYOUT, unsized_layout(1, 1, 4));
// ...with `packed(N)`:
#[derive(KnownLayout)]
#[repr(C, packed(2))]
struct KL10PackedN(NotKnownLayout<AU32>, [u8]);
let repr_packed = NonZeroUsize::new(2);
let expected = DstLayout::new_zst(None)
.extend(DstLayout::for_type::<NotKnownLayout<AU32>>(), repr_packed)
.extend(<[u8] as KnownLayout>::LAYOUT, repr_packed)
.pad_to_align();
assert_eq!(<KL10PackedN as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL10PackedN as KnownLayout>::LAYOUT, unsized_layout(2, 1, 4));
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | Y | N | Y | Y | KL11 |
#[derive(KnownLayout)]
#[repr(C)]
struct KL11(NotKnownLayout<AU64>, u8);
let expected = DstLayout::new_zst(None)
.extend(DstLayout::for_type::<NotKnownLayout<AU64>>(), None)
.extend(<u8 as KnownLayout>::LAYOUT, None)
.pad_to_align();
assert_eq!(<KL11 as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL11 as KnownLayout>::LAYOUT, sized_layout(8, 16));
// ...with `align(N)`:
#[derive(KnownLayout)]
#[repr(C, align(64))]
struct KL11Align(NotKnownLayout<AU64>, u8);
let repr_align = NonZeroUsize::new(64);
let expected = DstLayout::new_zst(repr_align)
.extend(DstLayout::for_type::<NotKnownLayout<AU64>>(), None)
.extend(<u8 as KnownLayout>::LAYOUT, None)
.pad_to_align();
assert_eq!(<KL11Align as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL11Align as KnownLayout>::LAYOUT, sized_layout(64, 64));
// ...with `packed`:
#[derive(KnownLayout)]
#[repr(C, packed)]
struct KL11Packed(NotKnownLayout<AU64>, u8);
let repr_packed = NonZeroUsize::new(1);
let expected = DstLayout::new_zst(None)
.extend(DstLayout::for_type::<NotKnownLayout<AU64>>(), repr_packed)
.extend(<u8 as KnownLayout>::LAYOUT, repr_packed)
.pad_to_align();
assert_eq!(<KL11Packed as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL11Packed as KnownLayout>::LAYOUT, sized_layout(1, 9));
// ...with `packed(N)`:
#[derive(KnownLayout)]
#[repr(C, packed(2))]
struct KL11PackedN(NotKnownLayout<AU64>, u8);
let repr_packed = NonZeroUsize::new(2);
let expected = DstLayout::new_zst(None)
.extend(DstLayout::for_type::<NotKnownLayout<AU64>>(), repr_packed)
.extend(<u8 as KnownLayout>::LAYOUT, repr_packed)
.pad_to_align();
assert_eq!(<KL11PackedN as KnownLayout>::LAYOUT, expected);
assert_eq!(<KL11PackedN as KnownLayout>::LAYOUT, sized_layout(2, 10));
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | Y | Y | Y | N | KL14 |
#[derive(KnownLayout)]
#[repr(C)]
struct KL14<T: ?Sized + KnownLayout>(u8, T);
fn _test_kl14<T: ?Sized + KnownLayout>(kl: &KL14<T>) {
_assert_kl(kl)
}
// | `repr(C)`? | generic? | `KnownLayout`? | `Sized`? | Type Name |
// | Y | Y | Y | Y | KL15 |
#[derive(KnownLayout)]
#[repr(C)]
struct KL15<T: KnownLayout>(u8, T);
fn _test_kl15<T: KnownLayout>(t: T) -> impl KnownLayout {
let _ = KL15(0u8, t);
}
// Test a variety of combinations of field types:
// - ()
// - u8
// - AU16
// - [()]
// - [u8]
// - [AU16]
#[allow(clippy::upper_case_acronyms)]
#[derive(KnownLayout)]
#[repr(C)]
struct KLTU<T, U: ?Sized>(T, U);
assert_eq!(<KLTU<(), ()> as KnownLayout>::LAYOUT, sized_layout(1, 0));
assert_eq!(<KLTU<(), u8> as KnownLayout>::LAYOUT, sized_layout(1, 1));
assert_eq!(<KLTU<(), AU16> as KnownLayout>::LAYOUT, sized_layout(2, 2));
assert_eq!(<KLTU<(), [()]> as KnownLayout>::LAYOUT, unsized_layout(1, 0, 0));
assert_eq!(<KLTU<(), [u8]> as KnownLayout>::LAYOUT, unsized_layout(1, 1, 0));
assert_eq!(<KLTU<(), [AU16]> as KnownLayout>::LAYOUT, unsized_layout(2, 2, 0));
assert_eq!(<KLTU<u8, ()> as KnownLayout>::LAYOUT, sized_layout(1, 1));
assert_eq!(<KLTU<u8, u8> as KnownLayout>::LAYOUT, sized_layout(1, 2));
assert_eq!(<KLTU<u8, AU16> as KnownLayout>::LAYOUT, sized_layout(2, 4));
assert_eq!(<KLTU<u8, [()]> as KnownLayout>::LAYOUT, unsized_layout(1, 0, 1));
assert_eq!(<KLTU<u8, [u8]> as KnownLayout>::LAYOUT, unsized_layout(1, 1, 1));
assert_eq!(<KLTU<u8, [AU16]> as KnownLayout>::LAYOUT, unsized_layout(2, 2, 2));
assert_eq!(<KLTU<AU16, ()> as KnownLayout>::LAYOUT, sized_layout(2, 2));
assert_eq!(<KLTU<AU16, u8> as KnownLayout>::LAYOUT, sized_layout(2, 4));
assert_eq!(<KLTU<AU16, AU16> as KnownLayout>::LAYOUT, sized_layout(2, 4));
assert_eq!(<KLTU<AU16, [()]> as KnownLayout>::LAYOUT, unsized_layout(2, 0, 2));
assert_eq!(<KLTU<AU16, [u8]> as KnownLayout>::LAYOUT, unsized_layout(2, 1, 2));
assert_eq!(<KLTU<AU16, [AU16]> as KnownLayout>::LAYOUT, unsized_layout(2, 2, 2));
// Test a variety of field counts.
#[derive(KnownLayout)]
#[repr(C)]
struct KLF0;
assert_eq!(<KLF0 as KnownLayout>::LAYOUT, sized_layout(1, 0));
#[derive(KnownLayout)]
#[repr(C)]
struct KLF1([u8]);
assert_eq!(<KLF1 as KnownLayout>::LAYOUT, unsized_layout(1, 1, 0));
#[derive(KnownLayout)]
#[repr(C)]
struct KLF2(NotKnownLayout<u8>, [u8]);
assert_eq!(<KLF2 as KnownLayout>::LAYOUT, unsized_layout(1, 1, 1));
#[derive(KnownLayout)]
#[repr(C)]
struct KLF3(NotKnownLayout<u8>, NotKnownLayout<AU16>, [u8]);
assert_eq!(<KLF3 as KnownLayout>::LAYOUT, unsized_layout(2, 1, 4));
#[derive(KnownLayout)]
#[repr(C)]
struct KLF4(NotKnownLayout<u8>, NotKnownLayout<AU16>, NotKnownLayout<AU32>, [u8]);
assert_eq!(<KLF4 as KnownLayout>::LAYOUT, unsized_layout(4, 1, 8));
}
#[test]
fn test_object_safety() {
fn _takes_from_zeroes(_: &dyn FromZeroes) {}
fn _takes_from_bytes(_: &dyn FromBytes) {}
fn _takes_unaligned(_: &dyn Unaligned) {}
}
#[test]
fn test_from_zeroes_only() {
// Test types that implement `FromZeroes` but not `FromBytes`.
assert!(!bool::new_zeroed());
assert_eq!(char::new_zeroed(), '\0');
#[cfg(feature = "alloc")]
{
assert_eq!(bool::new_box_zeroed(), Box::new(false));
assert_eq!(char::new_box_zeroed(), Box::new('\0'));
assert_eq!(bool::new_box_slice_zeroed(3).as_ref(), [false, false, false]);
assert_eq!(char::new_box_slice_zeroed(3).as_ref(), ['\0', '\0', '\0']);
assert_eq!(bool::new_vec_zeroed(3).as_ref(), [false, false, false]);
assert_eq!(char::new_vec_zeroed(3).as_ref(), ['\0', '\0', '\0']);
}
let mut string = "hello".to_string();
let s: &mut str = string.as_mut();
assert_eq!(s, "hello");
s.zero();
assert_eq!(s, "\0\0\0\0\0");
}
#[test]
fn test_read_write() {
const VAL: u64 = 0x12345678;
#[cfg(target_endian = "big")]
const VAL_BYTES: [u8; 8] = VAL.to_be_bytes();
#[cfg(target_endian = "little")]
const VAL_BYTES: [u8; 8] = VAL.to_le_bytes();
// Test `FromBytes::{read_from, read_from_prefix, read_from_suffix}`.
assert_eq!(u64::read_from(&VAL_BYTES[..]), Some(VAL));
// The first 8 bytes are from `VAL_BYTES` and the second 8 bytes are all
// zeroes.
let bytes_with_prefix: [u8; 16] = transmute!([VAL_BYTES, [0; 8]]);
assert_eq!(u64::read_from_prefix(&bytes_with_prefix[..]), Some(VAL));
assert_eq!(u64::read_from_suffix(&bytes_with_prefix[..]), Some(0));
// The first 8 bytes are all zeroes and the second 8 bytes are from
// `VAL_BYTES`
let bytes_with_suffix: [u8; 16] = transmute!([[0; 8], VAL_BYTES]);
assert_eq!(u64::read_from_prefix(&bytes_with_suffix[..]), Some(0));
assert_eq!(u64::read_from_suffix(&bytes_with_suffix[..]), Some(VAL));
// Test `AsBytes::{write_to, write_to_prefix, write_to_suffix}`.
let mut bytes = [0u8; 8];
assert_eq!(VAL.write_to(&mut bytes[..]), Some(()));
assert_eq!(bytes, VAL_BYTES);
let mut bytes = [0u8; 16];
assert_eq!(VAL.write_to_prefix(&mut bytes[..]), Some(()));
let want: [u8; 16] = transmute!([VAL_BYTES, [0; 8]]);
assert_eq!(bytes, want);
let mut bytes = [0u8; 16];
assert_eq!(VAL.write_to_suffix(&mut bytes[..]), Some(()));
let want: [u8; 16] = transmute!([[0; 8], VAL_BYTES]);
assert_eq!(bytes, want);
}
#[test]
fn test_transmute() {
// Test that memory is transmuted as expected.
let array_of_u8s = [0u8, 1, 2, 3, 4, 5, 6, 7];
let array_of_arrays = [[0, 1], [2, 3], [4, 5], [6, 7]];
let x: [[u8; 2]; 4] = transmute!(array_of_u8s);
assert_eq!(x, array_of_arrays);
let x: [u8; 8] = transmute!(array_of_arrays);
assert_eq!(x, array_of_u8s);
// Test that the source expression's value is forgotten rather than
// dropped.
#[derive(AsBytes)]
#[repr(transparent)]
struct PanicOnDrop(());
impl Drop for PanicOnDrop {
fn drop(&mut self) {
panic!("PanicOnDrop::drop");
}
}
#[allow(clippy::let_unit_value)]
let _: () = transmute!(PanicOnDrop(()));
// Test that `transmute!` is legal in a const context.
const ARRAY_OF_U8S: [u8; 8] = [0u8, 1, 2, 3, 4, 5, 6, 7];
const ARRAY_OF_ARRAYS: [[u8; 2]; 4] = [[0, 1], [2, 3], [4, 5], [6, 7]];
const X: [[u8; 2]; 4] = transmute!(ARRAY_OF_U8S);
assert_eq!(X, ARRAY_OF_ARRAYS);
}
#[test]
fn test_transmute_ref() {
// Test that memory is transmuted as expected.
let array_of_u8s = [0u8, 1, 2, 3, 4, 5, 6, 7];
let array_of_arrays = [[0, 1], [2, 3], [4, 5], [6, 7]];
let x: &[[u8; 2]; 4] = transmute_ref!(&array_of_u8s);
assert_eq!(*x, array_of_arrays);
let x: &[u8; 8] = transmute_ref!(&array_of_arrays);
assert_eq!(*x, array_of_u8s);
// Test that `transmute_ref!` is legal in a const context.
const ARRAY_OF_U8S: [u8; 8] = [0u8, 1, 2, 3, 4, 5, 6, 7];
const ARRAY_OF_ARRAYS: [[u8; 2]; 4] = [[0, 1], [2, 3], [4, 5], [6, 7]];
#[allow(clippy::redundant_static_lifetimes)]
const X: &'static [[u8; 2]; 4] = transmute_ref!(&ARRAY_OF_U8S);
assert_eq!(*X, ARRAY_OF_ARRAYS);
// Test that it's legal to transmute a reference while shrinking the
// lifetime (note that `X` has the lifetime `'static`).
let x: &[u8; 8] = transmute_ref!(X);
assert_eq!(*x, ARRAY_OF_U8S);
// Test that `transmute_ref!` supports decreasing alignment.
let u = AU64(0);
let array = [0, 0, 0, 0, 0, 0, 0, 0];
let x: &[u8; 8] = transmute_ref!(&u);
assert_eq!(*x, array);
// Test that a mutable reference can be turned into an immutable one.
let mut x = 0u8;
#[allow(clippy::useless_transmute)]
let y: &u8 = transmute_ref!(&mut x);
assert_eq!(*y, 0);
}
#[test]
fn test_transmute_mut() {
// Test that memory is transmuted as expected.
let mut array_of_u8s = [0u8, 1, 2, 3, 4, 5, 6, 7];
let mut array_of_arrays = [[0, 1], [2, 3], [4, 5], [6, 7]];
let x: &mut [[u8; 2]; 4] = transmute_mut!(&mut array_of_u8s);
assert_eq!(*x, array_of_arrays);
let x: &mut [u8; 8] = transmute_mut!(&mut array_of_arrays);
assert_eq!(*x, array_of_u8s);
{
// Test that it's legal to transmute a reference while shrinking the
// lifetime.
let x: &mut [u8; 8] = transmute_mut!(&mut array_of_arrays);
assert_eq!(*x, array_of_u8s);
}
// Test that `transmute_mut!` supports decreasing alignment.
let mut u = AU64(0);
let array = [0, 0, 0, 0, 0, 0, 0, 0];
let x: &[u8; 8] = transmute_mut!(&mut u);
assert_eq!(*x, array);
// Test that a mutable reference can be turned into an immutable one.
let mut x = 0u8;
#[allow(clippy::useless_transmute)]
let y: &u8 = transmute_mut!(&mut x);
assert_eq!(*y, 0);
}
#[test]
fn test_macros_evaluate_args_once() {
let mut ctr = 0;
let _: usize = transmute!({
ctr += 1;
0usize
});
assert_eq!(ctr, 1);
let mut ctr = 0;
let _: &usize = transmute_ref!({
ctr += 1;
&0usize
});
assert_eq!(ctr, 1);
}
#[test]
fn test_include_value() {
const AS_U32: u32 = include_value!("../testdata/include_value/data");
assert_eq!(AS_U32, u32::from_ne_bytes([b'a', b'b', b'c', b'd']));
const AS_I32: i32 = include_value!("../testdata/include_value/data");
assert_eq!(AS_I32, i32::from_ne_bytes([b'a', b'b', b'c', b'd']));
}
#[test]
fn test_address() {
// Test that the `Deref` and `DerefMut` implementations return a
// reference which points to the right region of memory.
let buf = [0];
let r = Ref::<_, u8>::new(&buf[..]).unwrap();
let buf_ptr = buf.as_ptr();
let deref_ptr: *const u8 = r.deref();
assert_eq!(buf_ptr, deref_ptr);
let buf = [0];
let r = Ref::<_, [u8]>::new_slice(&buf[..]).unwrap();
let buf_ptr = buf.as_ptr();
let deref_ptr = r.deref().as_ptr();
assert_eq!(buf_ptr, deref_ptr);
}
// Verify that values written to a `Ref` are properly shared between the
// typed and untyped representations, that reads via `deref` and `read`
// behave the same, and that writes via `deref_mut` and `write` behave the
// same.
fn test_new_helper(mut r: Ref<&mut [u8], AU64>) {
// assert that the value starts at 0
assert_eq!(*r, AU64(0));
assert_eq!(r.read(), AU64(0));
// Assert that values written to the typed value are reflected in the
// byte slice.
const VAL1: AU64 = AU64(0xFF00FF00FF00FF00);
*r = VAL1;
assert_eq!(r.bytes(), &VAL1.to_bytes());
*r = AU64(0);
r.write(VAL1);
assert_eq!(r.bytes(), &VAL1.to_bytes());
// Assert that values written to the byte slice are reflected in the
// typed value.
const VAL2: AU64 = AU64(!VAL1.0); // different from `VAL1`
r.bytes_mut().copy_from_slice(&VAL2.to_bytes()[..]);
assert_eq!(*r, VAL2);
assert_eq!(r.read(), VAL2);
}
// Verify that values written to a `Ref` are properly shared between the
// typed and untyped representations; pass a value with `typed_len` `AU64`s
// backed by an array of `typed_len * 8` bytes.
fn test_new_helper_slice(mut r: Ref<&mut [u8], [AU64]>, typed_len: usize) {
// Assert that the value starts out zeroed.
assert_eq!(&*r, vec![AU64(0); typed_len].as_slice());
// Check the backing storage is the exact same slice.
let untyped_len = typed_len * 8;
assert_eq!(r.bytes().len(), untyped_len);
assert_eq!(r.bytes().as_ptr(), r.as_ptr().cast::<u8>());
// Assert that values written to the typed value are reflected in the
// byte slice.
const VAL1: AU64 = AU64(0xFF00FF00FF00FF00);
for typed in &mut *r {
*typed = VAL1;
}
assert_eq!(r.bytes(), VAL1.0.to_ne_bytes().repeat(typed_len).as_slice());
// Assert that values written to the byte slice are reflected in the
// typed value.
const VAL2: AU64 = AU64(!VAL1.0); // different from VAL1
r.bytes_mut().copy_from_slice(&VAL2.0.to_ne_bytes().repeat(typed_len));
assert!(r.iter().copied().all(|x| x == VAL2));
}
// Verify that values written to a `Ref` are properly shared between the
// typed and untyped representations, that reads via `deref` and `read`
// behave the same, and that writes via `deref_mut` and `write` behave the
// same.
fn test_new_helper_unaligned(mut r: Ref<&mut [u8], [u8; 8]>) {
// assert that the value starts at 0
assert_eq!(*r, [0; 8]);
assert_eq!(r.read(), [0; 8]);
// Assert that values written to the typed value are reflected in the
// byte slice.
const VAL1: [u8; 8] = [0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00];
*r = VAL1;
assert_eq!(r.bytes(), &VAL1);
*r = [0; 8];
r.write(VAL1);
assert_eq!(r.bytes(), &VAL1);
// Assert that values written to the byte slice are reflected in the
// typed value.
const VAL2: [u8; 8] = [0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF]; // different from VAL1
r.bytes_mut().copy_from_slice(&VAL2[..]);
assert_eq!(*r, VAL2);
assert_eq!(r.read(), VAL2);
}
// Verify that values written to a `Ref` are properly shared between the
// typed and untyped representations; pass a value with `len` `u8`s backed
// by an array of `len` bytes.
fn test_new_helper_slice_unaligned(mut r: Ref<&mut [u8], [u8]>, len: usize) {
// Assert that the value starts out zeroed.
assert_eq!(&*r, vec![0u8; len].as_slice());
// Check the backing storage is the exact same slice.
assert_eq!(r.bytes().len(), len);
assert_eq!(r.bytes().as_ptr(), r.as_ptr());
// Assert that values written to the typed value are reflected in the
// byte slice.
let mut expected_bytes = [0xFF, 0x00].iter().copied().cycle().take(len).collect::<Vec<_>>();
r.copy_from_slice(&expected_bytes);
assert_eq!(r.bytes(), expected_bytes.as_slice());
// Assert that values written to the byte slice are reflected in the
// typed value.
for byte in &mut expected_bytes {
*byte = !*byte; // different from `expected_len`
}
r.bytes_mut().copy_from_slice(&expected_bytes);
assert_eq!(&*r, expected_bytes.as_slice());
}
#[test]
fn test_new_aligned_sized() {
// Test that a properly-aligned, properly-sized buffer works for new,
// new_from_prefix, and new_from_suffix, and that new_from_prefix and
// new_from_suffix return empty slices. Test that a properly-aligned
// buffer whose length is a multiple of the element size works for
// new_slice. Test that xxx_zeroed behaves the same, and zeroes the
// memory.
// A buffer with an alignment of 8.
let mut buf = Align::<[u8; 8], AU64>::default();
// `buf.t` should be aligned to 8, so this should always succeed.
test_new_helper(Ref::<_, AU64>::new(&mut buf.t[..]).unwrap());
let ascending: [u8; 8] = (0..8).collect::<Vec<_>>().try_into().unwrap();
buf.t = ascending;
test_new_helper(Ref::<_, AU64>::new_zeroed(&mut buf.t[..]).unwrap());
{
// In a block so that `r` and `suffix` don't live too long.
buf.set_default();
let (r, suffix) = Ref::<_, AU64>::new_from_prefix(&mut buf.t[..]).unwrap();
assert!(suffix.is_empty());
test_new_helper(r);
}
{
buf.t = ascending;
let (r, suffix) = Ref::<_, AU64>::new_from_prefix_zeroed(&mut buf.t[..]).unwrap();
assert!(suffix.is_empty());
test_new_helper(r);
}
{
buf.set_default();
let (prefix, r) = Ref::<_, AU64>::new_from_suffix(&mut buf.t[..]).unwrap();
assert!(prefix.is_empty());
test_new_helper(r);
}
{
buf.t = ascending;
let (prefix, r) = Ref::<_, AU64>::new_from_suffix_zeroed(&mut buf.t[..]).unwrap();
assert!(prefix.is_empty());
test_new_helper(r);
}
// A buffer with alignment 8 and length 24. We choose this length very
// intentionally: if we instead used length 16, then the prefix and
// suffix lengths would be identical. In the past, we used length 16,
// which resulted in this test failing to discover the bug uncovered in
// #506.
let mut buf = Align::<[u8; 24], AU64>::default();
// `buf.t` should be aligned to 8 and have a length which is a multiple
// of `size_of::<AU64>()`, so this should always succeed.
test_new_helper_slice(Ref::<_, [AU64]>::new_slice(&mut buf.t[..]).unwrap(), 3);
let ascending: [u8; 24] = (0..24).collect::<Vec<_>>().try_into().unwrap();
// 16 ascending bytes followed by 8 zeros.
let mut ascending_prefix = ascending;
ascending_prefix[16..].copy_from_slice(&[0, 0, 0, 0, 0, 0, 0, 0]);
// 8 zeros followed by 16 ascending bytes.
let mut ascending_suffix = ascending;
ascending_suffix[..8].copy_from_slice(&[0, 0, 0, 0, 0, 0, 0, 0]);
test_new_helper_slice(Ref::<_, [AU64]>::new_slice_zeroed(&mut buf.t[..]).unwrap(), 3);
{
buf.t = ascending_suffix;
let (r, suffix) = Ref::<_, [AU64]>::new_slice_from_prefix(&mut buf.t[..], 1).unwrap();
assert_eq!(suffix, &ascending[8..]);
test_new_helper_slice(r, 1);
}
{
buf.t = ascending_suffix;
let (r, suffix) =
Ref::<_, [AU64]>::new_slice_from_prefix_zeroed(&mut buf.t[..], 1).unwrap();
assert_eq!(suffix, &ascending[8..]);
test_new_helper_slice(r, 1);
}
{
buf.t = ascending_prefix;
let (prefix, r) = Ref::<_, [AU64]>::new_slice_from_suffix(&mut buf.t[..], 1).unwrap();
assert_eq!(prefix, &ascending[..16]);
test_new_helper_slice(r, 1);
}
{
buf.t = ascending_prefix;
let (prefix, r) =
Ref::<_, [AU64]>::new_slice_from_suffix_zeroed(&mut buf.t[..], 1).unwrap();
assert_eq!(prefix, &ascending[..16]);
test_new_helper_slice(r, 1);
}
}
#[test]
fn test_new_unaligned_sized() {
// Test that an unaligned, properly-sized buffer works for
// `new_unaligned`, `new_unaligned_from_prefix`, and
// `new_unaligned_from_suffix`, and that `new_unaligned_from_prefix`
// `new_unaligned_from_suffix` return empty slices. Test that an
// unaligned buffer whose length is a multiple of the element size works
// for `new_slice`. Test that `xxx_zeroed` behaves the same, and zeroes
// the memory.
let mut buf = [0u8; 8];
test_new_helper_unaligned(Ref::<_, [u8; 8]>::new_unaligned(&mut buf[..]).unwrap());
buf = [0xFFu8; 8];
test_new_helper_unaligned(Ref::<_, [u8; 8]>::new_unaligned_zeroed(&mut buf[..]).unwrap());
{
// In a block so that `r` and `suffix` don't live too long.
buf = [0u8; 8];
let (r, suffix) = Ref::<_, [u8; 8]>::new_unaligned_from_prefix(&mut buf[..]).unwrap();
assert!(suffix.is_empty());
test_new_helper_unaligned(r);
}
{
buf = [0xFFu8; 8];
let (r, suffix) =
Ref::<_, [u8; 8]>::new_unaligned_from_prefix_zeroed(&mut buf[..]).unwrap();
assert!(suffix.is_empty());
test_new_helper_unaligned(r);
}
{
buf = [0u8; 8];
let (prefix, r) = Ref::<_, [u8; 8]>::new_unaligned_from_suffix(&mut buf[..]).unwrap();
assert!(prefix.is_empty());
test_new_helper_unaligned(r);
}
{
buf = [0xFFu8; 8];
let (prefix, r) =
Ref::<_, [u8; 8]>::new_unaligned_from_suffix_zeroed(&mut buf[..]).unwrap();
assert!(prefix.is_empty());
test_new_helper_unaligned(r);
}
let mut buf = [0u8; 16];
// `buf.t` should be aligned to 8 and have a length which is a multiple
// of `size_of::AU64>()`, so this should always succeed.
test_new_helper_slice_unaligned(
Ref::<_, [u8]>::new_slice_unaligned(&mut buf[..]).unwrap(),
16,
);
buf = [0xFFu8; 16];
test_new_helper_slice_unaligned(
Ref::<_, [u8]>::new_slice_unaligned_zeroed(&mut buf[..]).unwrap(),
16,
);
{
buf = [0u8; 16];
let (r, suffix) =
Ref::<_, [u8]>::new_slice_unaligned_from_prefix(&mut buf[..], 8).unwrap();
assert_eq!(suffix, [0; 8]);
test_new_helper_slice_unaligned(r, 8);
}
{
buf = [0xFFu8; 16];
let (r, suffix) =
Ref::<_, [u8]>::new_slice_unaligned_from_prefix_zeroed(&mut buf[..], 8).unwrap();
assert_eq!(suffix, [0xFF; 8]);
test_new_helper_slice_unaligned(r, 8);
}
{
buf = [0u8; 16];
let (prefix, r) =
Ref::<_, [u8]>::new_slice_unaligned_from_suffix(&mut buf[..], 8).unwrap();
assert_eq!(prefix, [0; 8]);
test_new_helper_slice_unaligned(r, 8);
}
{
buf = [0xFFu8; 16];
let (prefix, r) =
Ref::<_, [u8]>::new_slice_unaligned_from_suffix_zeroed(&mut buf[..], 8).unwrap();
assert_eq!(prefix, [0xFF; 8]);
test_new_helper_slice_unaligned(r, 8);
}
}
#[test]
fn test_new_oversized() {
// Test that a properly-aligned, overly-sized buffer works for
// `new_from_prefix` and `new_from_suffix`, and that they return the
// remainder and prefix of the slice respectively. Test that
// `xxx_zeroed` behaves the same, and zeroes the memory.
let mut buf = Align::<[u8; 16], AU64>::default();
{
// In a block so that `r` and `suffix` don't live too long. `buf.t`
// should be aligned to 8, so this should always succeed.
let (r, suffix) = Ref::<_, AU64>::new_from_prefix(&mut buf.t[..]).unwrap();
assert_eq!(suffix.len(), 8);
test_new_helper(r);
}
{
buf.t = [0xFFu8; 16];
// `buf.t` should be aligned to 8, so this should always succeed.
let (r, suffix) = Ref::<_, AU64>::new_from_prefix_zeroed(&mut buf.t[..]).unwrap();
// Assert that the suffix wasn't zeroed.
assert_eq!(suffix, &[0xFFu8; 8]);
test_new_helper(r);
}
{
buf.set_default();
// `buf.t` should be aligned to 8, so this should always succeed.
let (prefix, r) = Ref::<_, AU64>::new_from_suffix(&mut buf.t[..]).unwrap();
assert_eq!(prefix.len(), 8);
test_new_helper(r);
}
{
buf.t = [0xFFu8; 16];
// `buf.t` should be aligned to 8, so this should always succeed.
let (prefix, r) = Ref::<_, AU64>::new_from_suffix_zeroed(&mut buf.t[..]).unwrap();
// Assert that the prefix wasn't zeroed.
assert_eq!(prefix, &[0xFFu8; 8]);
test_new_helper(r);
}
}
#[test]
fn test_new_unaligned_oversized() {
// Test than an unaligned, overly-sized buffer works for
// `new_unaligned_from_prefix` and `new_unaligned_from_suffix`, and that
// they return the remainder and prefix of the slice respectively. Test
// that `xxx_zeroed` behaves the same, and zeroes the memory.
let mut buf = [0u8; 16];
{
// In a block so that `r` and `suffix` don't live too long.
let (r, suffix) = Ref::<_, [u8; 8]>::new_unaligned_from_prefix(&mut buf[..]).unwrap();
assert_eq!(suffix.len(), 8);
test_new_helper_unaligned(r);
}
{
buf = [0xFFu8; 16];
let (r, suffix) =
Ref::<_, [u8; 8]>::new_unaligned_from_prefix_zeroed(&mut buf[..]).unwrap();
// Assert that the suffix wasn't zeroed.
assert_eq!(suffix, &[0xFF; 8]);
test_new_helper_unaligned(r);
}
{
buf = [0u8; 16];
let (prefix, r) = Ref::<_, [u8; 8]>::new_unaligned_from_suffix(&mut buf[..]).unwrap();
assert_eq!(prefix.len(), 8);
test_new_helper_unaligned(r);
}
{
buf = [0xFFu8; 16];
let (prefix, r) =
Ref::<_, [u8; 8]>::new_unaligned_from_suffix_zeroed(&mut buf[..]).unwrap();
// Assert that the prefix wasn't zeroed.
assert_eq!(prefix, &[0xFF; 8]);
test_new_helper_unaligned(r);
}
}
#[test]
fn test_ref_from_mut_from() {
// Test `FromBytes::{ref_from, mut_from}{,_prefix,_suffix}` success cases
// Exhaustive coverage for these methods is covered by the `Ref` tests above,
// which these helper methods defer to.
let mut buf =
Align::<[u8; 16], AU64>::new([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);
assert_eq!(
AU64::ref_from(&buf.t[8..]).unwrap().0.to_ne_bytes(),
[8, 9, 10, 11, 12, 13, 14, 15]
);
let suffix = AU64::mut_from(&mut buf.t[8..]).unwrap();
suffix.0 = 0x0101010101010101;
// The `[u8:9]` is a non-half size of the full buffer, which would catch
// `from_prefix` having the same implementation as `from_suffix` (issues #506, #511).
assert_eq!(<[u8; 9]>::ref_from_suffix(&buf.t[..]).unwrap(), &[7u8, 1, 1, 1, 1, 1, 1, 1, 1]);
let suffix = AU64::mut_from_suffix(&mut buf.t[1..]).unwrap();
suffix.0 = 0x0202020202020202;
<[u8; 10]>::mut_from_suffix(&mut buf.t[..]).unwrap()[0] = 42;
assert_eq!(<[u8; 9]>::ref_from_prefix(&buf.t[..]).unwrap(), &[0, 1, 2, 3, 4, 5, 42, 7, 2]);
<[u8; 2]>::mut_from_prefix(&mut buf.t[..]).unwrap()[1] = 30;
assert_eq!(buf.t, [0, 30, 2, 3, 4, 5, 42, 7, 2, 2, 2, 2, 2, 2, 2, 2]);
}
#[test]
fn test_ref_from_mut_from_error() {
// Test `FromBytes::{ref_from, mut_from}{,_prefix,_suffix}` error cases.
// Fail because the buffer is too large.
let mut buf = Align::<[u8; 16], AU64>::default();
// `buf.t` should be aligned to 8, so only the length check should fail.
assert!(AU64::ref_from(&buf.t[..]).is_none());
assert!(AU64::mut_from(&mut buf.t[..]).is_none());
assert!(<[u8; 8]>::ref_from(&buf.t[..]).is_none());
assert!(<[u8; 8]>::mut_from(&mut buf.t[..]).is_none());
// Fail because the buffer is too small.
let mut buf = Align::<[u8; 4], AU64>::default();
assert!(AU64::ref_from(&buf.t[..]).is_none());
assert!(AU64::mut_from(&mut buf.t[..]).is_none());
assert!(<[u8; 8]>::ref_from(&buf.t[..]).is_none());
assert!(<[u8; 8]>::mut_from(&mut buf.t[..]).is_none());
assert!(AU64::ref_from_prefix(&buf.t[..]).is_none());
assert!(AU64::mut_from_prefix(&mut buf.t[..]).is_none());
assert!(AU64::ref_from_suffix(&buf.t[..]).is_none());
assert!(AU64::mut_from_suffix(&mut buf.t[..]).is_none());
assert!(<[u8; 8]>::ref_from_prefix(&buf.t[..]).is_none());
assert!(<[u8; 8]>::mut_from_prefix(&mut buf.t[..]).is_none());
assert!(<[u8; 8]>::ref_from_suffix(&buf.t[..]).is_none());
assert!(<[u8; 8]>::mut_from_suffix(&mut buf.t[..]).is_none());
// Fail because the alignment is insufficient.
let mut buf = Align::<[u8; 13], AU64>::default();
assert!(AU64::ref_from(&buf.t[1..]).is_none());
assert!(AU64::mut_from(&mut buf.t[1..]).is_none());
assert!(AU64::ref_from(&buf.t[1..]).is_none());
assert!(AU64::mut_from(&mut buf.t[1..]).is_none());
assert!(AU64::ref_from_prefix(&buf.t[1..]).is_none());
assert!(AU64::mut_from_prefix(&mut buf.t[1..]).is_none());
assert!(AU64::ref_from_suffix(&buf.t[..]).is_none());
assert!(AU64::mut_from_suffix(&mut buf.t[..]).is_none());
}
#[test]
#[allow(clippy::cognitive_complexity)]
fn test_new_error() {
// Fail because the buffer is too large.
// A buffer with an alignment of 8.
let mut buf = Align::<[u8; 16], AU64>::default();
// `buf.t` should be aligned to 8, so only the length check should fail.
assert!(Ref::<_, AU64>::new(&buf.t[..]).is_none());
assert!(Ref::<_, AU64>::new_zeroed(&mut buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned(&buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned_zeroed(&mut buf.t[..]).is_none());
// Fail because the buffer is too small.
// A buffer with an alignment of 8.
let mut buf = Align::<[u8; 4], AU64>::default();
// `buf.t` should be aligned to 8, so only the length check should fail.
assert!(Ref::<_, AU64>::new(&buf.t[..]).is_none());
assert!(Ref::<_, AU64>::new_zeroed(&mut buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned(&buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned_zeroed(&mut buf.t[..]).is_none());
assert!(Ref::<_, AU64>::new_from_prefix(&buf.t[..]).is_none());
assert!(Ref::<_, AU64>::new_from_prefix_zeroed(&mut buf.t[..]).is_none());
assert!(Ref::<_, AU64>::new_from_suffix(&buf.t[..]).is_none());
assert!(Ref::<_, AU64>::new_from_suffix_zeroed(&mut buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned_from_prefix(&buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned_from_prefix_zeroed(&mut buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned_from_suffix(&buf.t[..]).is_none());
assert!(Ref::<_, [u8; 8]>::new_unaligned_from_suffix_zeroed(&mut buf.t[..]).is_none());
// Fail because the length is not a multiple of the element size.
let mut buf = Align::<[u8; 12], AU64>::default();
// `buf.t` has length 12, but element size is 8.
assert!(Ref::<_, [AU64]>::new_slice(&buf.t[..]).is_none());
assert!(Ref::<_, [AU64]>::new_slice_zeroed(&mut buf.t[..]).is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned(&buf.t[..]).is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_zeroed(&mut buf.t[..]).is_none());
// Fail because the buffer is too short.
let mut buf = Align::<[u8; 12], AU64>::default();
// `buf.t` has length 12, but the element size is 8 (and we're expecting
// two of them).
assert!(Ref::<_, [AU64]>::new_slice_from_prefix(&buf.t[..], 2).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_prefix_zeroed(&mut buf.t[..], 2).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_suffix(&buf.t[..], 2).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_suffix_zeroed(&mut buf.t[..], 2).is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_prefix(&buf.t[..], 2).is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_prefix_zeroed(&mut buf.t[..], 2)
.is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_suffix(&buf.t[..], 2).is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_suffix_zeroed(&mut buf.t[..], 2)
.is_none());
// Fail because the alignment is insufficient.
// A buffer with an alignment of 8. An odd buffer size is chosen so that
// the last byte of the buffer has odd alignment.
let mut buf = Align::<[u8; 13], AU64>::default();
// Slicing from 1, we get a buffer with size 12 (so the length check
// should succeed) but an alignment of only 1, which is insufficient.
assert!(Ref::<_, AU64>::new(&buf.t[1..]).is_none());
assert!(Ref::<_, AU64>::new_zeroed(&mut buf.t[1..]).is_none());
assert!(Ref::<_, AU64>::new_from_prefix(&buf.t[1..]).is_none());
assert!(Ref::<_, AU64>::new_from_prefix_zeroed(&mut buf.t[1..]).is_none());
assert!(Ref::<_, [AU64]>::new_slice(&buf.t[1..]).is_none());
assert!(Ref::<_, [AU64]>::new_slice_zeroed(&mut buf.t[1..]).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_prefix(&buf.t[1..], 1).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_prefix_zeroed(&mut buf.t[1..], 1).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_suffix(&buf.t[1..], 1).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_suffix_zeroed(&mut buf.t[1..], 1).is_none());
// Slicing is unnecessary here because `new_from_suffix[_zeroed]` use
// the suffix of the slice, which has odd alignment.
assert!(Ref::<_, AU64>::new_from_suffix(&buf.t[..]).is_none());
assert!(Ref::<_, AU64>::new_from_suffix_zeroed(&mut buf.t[..]).is_none());
// Fail due to arithmetic overflow.
let mut buf = Align::<[u8; 16], AU64>::default();
let unreasonable_len = usize::MAX / mem::size_of::<AU64>() + 1;
assert!(Ref::<_, [AU64]>::new_slice_from_prefix(&buf.t[..], unreasonable_len).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_prefix_zeroed(&mut buf.t[..], unreasonable_len)
.is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_suffix(&buf.t[..], unreasonable_len).is_none());
assert!(Ref::<_, [AU64]>::new_slice_from_suffix_zeroed(&mut buf.t[..], unreasonable_len)
.is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_prefix(&buf.t[..], unreasonable_len)
.is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_prefix_zeroed(
&mut buf.t[..],
unreasonable_len
)
.is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_suffix(&buf.t[..], unreasonable_len)
.is_none());
assert!(Ref::<_, [[u8; 8]]>::new_slice_unaligned_from_suffix_zeroed(
&mut buf.t[..],
unreasonable_len
)
.is_none());
}
// Tests for ensuring that, if a ZST is passed into a slice-like function,
// we always panic. Since these tests need to be separate per-function, and
// they tend to take up a lot of space, we generate them using a macro in a
// submodule instead. The submodule ensures that we can just re-use the name
// of the function under test for the name of the test itself.
mod test_zst_panics {
macro_rules! zst_test {
($name:ident($($tt:tt)*), $constructor_in_panic_msg:tt) => {
#[test]
#[should_panic = concat!("Ref::", $constructor_in_panic_msg, " called on a zero-sized type")]
fn $name() {
let mut buffer = [0u8];
let r = $crate::Ref::<_, [()]>::$name(&mut buffer[..], $($tt)*);
unreachable!("should have panicked, got {:?}", r);
}
}
}
zst_test!(new_slice(), "new_slice");
zst_test!(new_slice_zeroed(), "new_slice");
zst_test!(new_slice_from_prefix(1), "new_slice");
zst_test!(new_slice_from_prefix_zeroed(1), "new_slice");
zst_test!(new_slice_from_suffix(1), "new_slice");
zst_test!(new_slice_from_suffix_zeroed(1), "new_slice");
zst_test!(new_slice_unaligned(), "new_slice_unaligned");
zst_test!(new_slice_unaligned_zeroed(), "new_slice_unaligned");
zst_test!(new_slice_unaligned_from_prefix(1), "new_slice_unaligned");
zst_test!(new_slice_unaligned_from_prefix_zeroed(1), "new_slice_unaligned");
zst_test!(new_slice_unaligned_from_suffix(1), "new_slice_unaligned");
zst_test!(new_slice_unaligned_from_suffix_zeroed(1), "new_slice_unaligned");
}
#[test]
fn test_as_bytes_methods() {
/// Run a series of tests by calling `AsBytes` methods on `t`.
///
/// `bytes` is the expected byte sequence returned from `t.as_bytes()`
/// before `t` has been modified. `post_mutation` is the expected
/// sequence returned from `t.as_bytes()` after `t.as_bytes_mut()[0]`
/// has had its bits flipped (by applying `^= 0xFF`).
///
/// `N` is the size of `t` in bytes.
fn test<T: FromBytes + AsBytes + Debug + Eq + ?Sized, const N: usize>(
t: &mut T,
bytes: &[u8],
post_mutation: &T,
) {
// Test that we can access the underlying bytes, and that we get the
// right bytes and the right number of bytes.
assert_eq!(t.as_bytes(), bytes);
// Test that changes to the underlying byte slices are reflected in
// the original object.
t.as_bytes_mut()[0] ^= 0xFF;
assert_eq!(t, post_mutation);
t.as_bytes_mut()[0] ^= 0xFF;
// `write_to` rejects slices that are too small or too large.
assert_eq!(t.write_to(&mut vec![0; N - 1][..]), None);
assert_eq!(t.write_to(&mut vec![0; N + 1][..]), None);
// `write_to` works as expected.
let mut bytes = [0; N];
assert_eq!(t.write_to(&mut bytes[..]), Some(()));
assert_eq!(bytes, t.as_bytes());
// `write_to_prefix` rejects slices that are too small.
assert_eq!(t.write_to_prefix(&mut vec![0; N - 1][..]), None);
// `write_to_prefix` works with exact-sized slices.
let mut bytes = [0; N];
assert_eq!(t.write_to_prefix(&mut bytes[..]), Some(()));
assert_eq!(bytes, t.as_bytes());
// `write_to_prefix` works with too-large slices, and any bytes past
// the prefix aren't modified.
let mut too_many_bytes = vec![0; N + 1];
too_many_bytes[N] = 123;
assert_eq!(t.write_to_prefix(&mut too_many_bytes[..]), Some(()));
assert_eq!(&too_many_bytes[..N], t.as_bytes());
assert_eq!(too_many_bytes[N], 123);
// `write_to_suffix` rejects slices that are too small.
assert_eq!(t.write_to_suffix(&mut vec![0; N - 1][..]), None);
// `write_to_suffix` works with exact-sized slices.
let mut bytes = [0; N];
assert_eq!(t.write_to_suffix(&mut bytes[..]), Some(()));
assert_eq!(bytes, t.as_bytes());
// `write_to_suffix` works with too-large slices, and any bytes
// before the suffix aren't modified.
let mut too_many_bytes = vec![0; N + 1];
too_many_bytes[0] = 123;
assert_eq!(t.write_to_suffix(&mut too_many_bytes[..]), Some(()));
assert_eq!(&too_many_bytes[1..], t.as_bytes());
assert_eq!(too_many_bytes[0], 123);
}
#[derive(Debug, Eq, PartialEq, FromZeroes, FromBytes, AsBytes)]
#[repr(C)]
struct Foo {
a: u32,
b: Wrapping<u32>,
c: Option<NonZeroU32>,
}
let expected_bytes: Vec<u8> = if cfg!(target_endian = "little") {
vec![1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0]
} else {
vec![0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0]
};
let post_mutation_expected_a =
if cfg!(target_endian = "little") { 0x00_00_00_FE } else { 0xFF_00_00_01 };
test::<_, 12>(
&mut Foo { a: 1, b: Wrapping(2), c: None },
expected_bytes.as_bytes(),
&Foo { a: post_mutation_expected_a, b: Wrapping(2), c: None },
);
test::<_, 3>(
Unsized::from_mut_slice(&mut [1, 2, 3]),
&[1, 2, 3],
Unsized::from_mut_slice(&mut [0xFE, 2, 3]),
);
}
#[test]
fn test_array() {
#[derive(FromZeroes, FromBytes, AsBytes)]
#[repr(C)]
struct Foo {
a: [u16; 33],
}
let foo = Foo { a: [0xFFFF; 33] };
let expected = [0xFFu8; 66];
assert_eq!(foo.as_bytes(), &expected[..]);
}
#[test]
fn test_display_debug() {
let buf = Align::<[u8; 8], u64>::default();
let r = Ref::<_, u64>::new(&buf.t[..]).unwrap();
assert_eq!(format!("{}", r), "0");
assert_eq!(format!("{:?}", r), "Ref(0)");
let buf = Align::<[u8; 8], u64>::default();
let r = Ref::<_, [u64]>::new_slice(&buf.t[..]).unwrap();
assert_eq!(format!("{:?}", r), "Ref([0])");
}
#[test]
fn test_eq() {
let buf1 = 0_u64;
let r1 = Ref::<_, u64>::new(buf1.as_bytes()).unwrap();
let buf2 = 0_u64;
let r2 = Ref::<_, u64>::new(buf2.as_bytes()).unwrap();
assert_eq!(r1, r2);
}
#[test]
fn test_ne() {
let buf1 = 0_u64;
let r1 = Ref::<_, u64>::new(buf1.as_bytes()).unwrap();
let buf2 = 1_u64;
let r2 = Ref::<_, u64>::new(buf2.as_bytes()).unwrap();
assert_ne!(r1, r2);
}
#[test]
fn test_ord() {
let buf1 = 0_u64;
let r1 = Ref::<_, u64>::new(buf1.as_bytes()).unwrap();
let buf2 = 1_u64;
let r2 = Ref::<_, u64>::new(buf2.as_bytes()).unwrap();
assert!(r1 < r2);
}
#[test]
fn test_new_zeroed() {
assert!(!bool::new_zeroed());
assert_eq!(u64::new_zeroed(), 0);
// This test exists in order to exercise unsafe code, especially when
// running under Miri.
#[allow(clippy::unit_cmp)]
{
assert_eq!(<()>::new_zeroed(), ());
}
}
#[test]
fn test_transparent_packed_generic_struct() {
#[derive(AsBytes, FromZeroes, FromBytes, Unaligned)]
#[repr(transparent)]
#[allow(dead_code)] // for the unused fields
struct Foo<T> {
_t: T,
_phantom: PhantomData<()>,
}
assert_impl_all!(Foo<u32>: FromZeroes, FromBytes, AsBytes);
assert_impl_all!(Foo<u8>: Unaligned);
#[derive(AsBytes, FromZeroes, FromBytes, Unaligned)]
#[repr(packed)]
#[allow(dead_code)] // for the unused fields
struct Bar<T, U> {
_t: T,
_u: U,
}
assert_impl_all!(Bar<u8, AU64>: FromZeroes, FromBytes, AsBytes, Unaligned);
}
#[test]
fn test_impls() {
use core::borrow::Borrow;
// A type that can supply test cases for testing
// `TryFromBytes::is_bit_valid`. All types passed to `assert_impls!`
// must implement this trait; that macro uses it to generate runtime
// tests for `TryFromBytes` impls.
//
// All `T: FromBytes` types are provided with a blanket impl. Other
// types must implement `TryFromBytesTestable` directly (ie using
// `impl_try_from_bytes_testable!`).
trait TryFromBytesTestable {
fn with_passing_test_cases<F: Fn(&Self)>(f: F);
fn with_failing_test_cases<F: Fn(&[u8])>(f: F);
}
impl<T: FromBytes> TryFromBytesTestable for T {
fn with_passing_test_cases<F: Fn(&Self)>(f: F) {
// Test with a zeroed value.
f(&Self::new_zeroed());
let ffs = {
let mut t = Self::new_zeroed();
let ptr: *mut T = &mut t;
// SAFETY: `T: FromBytes`
unsafe { ptr::write_bytes(ptr.cast::<u8>(), 0xFF, mem::size_of::<T>()) };
t
};
// Test with a value initialized with 0xFF.
f(&ffs);
}
fn with_failing_test_cases<F: Fn(&[u8])>(_f: F) {}
}
// Implements `TryFromBytesTestable`.
macro_rules! impl_try_from_bytes_testable {
// Base case for recursion (when the list of types has run out).
(=> @success $($success_case:expr),* $(, @failure $($failure_case:expr),*)?) => {};
// Implements for type(s) with no type parameters.
($ty:ty $(,$tys:ty)* => @success $($success_case:expr),* $(, @failure $($failure_case:expr),*)?) => {
impl TryFromBytesTestable for $ty {
impl_try_from_bytes_testable!(
@methods @success $($success_case),*
$(, @failure $($failure_case),*)?
);
}
impl_try_from_bytes_testable!($($tys),* => @success $($success_case),* $(, @failure $($failure_case),*)?);
};
// Implements for multiple types with no type parameters.
($($($ty:ty),* => @success $($success_case:expr), * $(, @failure $($failure_case:expr),*)?;)*) => {
$(
impl_try_from_bytes_testable!($($ty),* => @success $($success_case),* $(, @failure $($failure_case),*)*);
)*
};
// Implements only the methods; caller must invoke this from inside
// an impl block.
(@methods @success $($success_case:expr),* $(, @failure $($failure_case:expr),*)?) => {
fn with_passing_test_cases<F: Fn(&Self)>(_f: F) {
$(
_f($success_case.borrow());
)*
}
fn with_failing_test_cases<F: Fn(&[u8])>(_f: F) {
$($(
let case = $failure_case.as_bytes();
_f(case.as_bytes());
)*)?
}
};
}
// Note that these impls are only for types which are not `FromBytes`.
// `FromBytes` types are covered by a preceding blanket impl.
impl_try_from_bytes_testable!(
bool => @success true, false,
@failure 2u8, 3u8, 0xFFu8;
char => @success '\u{0}', '\u{D7FF}', '\u{E000}', '\u{10FFFF}',
@failure 0xD800u32, 0xDFFFu32, 0x110000u32;
str => @success "", "hello", "โค๏ธ๐งก๐๐๐๐",
@failure [0, 159, 146, 150];
[u8] => @success [], [0, 1, 2];
NonZeroU8, NonZeroI8, NonZeroU16, NonZeroI16, NonZeroU32,
NonZeroI32, NonZeroU64, NonZeroI64, NonZeroU128, NonZeroI128,
NonZeroUsize, NonZeroIsize
=> @success Self::new(1).unwrap(),
// Doing this instead of `0` ensures that we always satisfy
// the size and alignment requirements of `Self` (whereas
// `0` may be any integer type with a different size or
// alignment than some `NonZeroXxx` types).
@failure Option::<Self>::None;
[bool]
=> @success [true, false], [false, true],
@failure [2u8], [3u8], [0xFFu8], [0u8, 1u8, 2u8];
);
// Asserts that `$ty` implements any `$trait` and doesn't implement any
// `!$trait`. Note that all `$trait`s must come before any `!$trait`s.
//
// For `T: TryFromBytes`, uses `TryFromBytesTestable` to test success
// and failure cases for `TryFromBytes::is_bit_valid`.
macro_rules! assert_impls {
($ty:ty: TryFromBytes) => {
<$ty as TryFromBytesTestable>::with_passing_test_cases(|val| {
let c = Ptr::from(val);
// SAFETY:
// - Since `val` is a normal reference, `c` is guranteed to
// be aligned, to point to a single allocation, and to
// have a size which doesn't overflow `isize`.
// - Since `val` is a valid `$ty`, `c`'s referent satisfies
// the bit validity constraints of `is_bit_valid`, which
// are a superset of the bit validity constraints of
// `$ty`.
let res = unsafe { <$ty as TryFromBytes>::is_bit_valid(c) };
assert!(res, "{}::is_bit_valid({:?}): got false, expected true", stringify!($ty), val);
// TODO(#5): In addition to testing `is_bit_valid`, test the
// methods built on top of it. This would both allow us to
// test their implementations and actually convert the bytes
// to `$ty`, giving Miri a chance to catch if this is
// unsound (ie, if our `is_bit_valid` impl is buggy).
//
// The following code was tried, but it doesn't work because
// a) some types are not `AsBytes` and, b) some types are
// not `Sized`.
//
// let r = <$ty as TryFromBytes>::try_from_ref(val.as_bytes()).unwrap();
// assert_eq!(r, &val);
// let r = <$ty as TryFromBytes>::try_from_mut(val.as_bytes_mut()).unwrap();
// assert_eq!(r, &mut val);
// let v = <$ty as TryFromBytes>::try_read_from(val.as_bytes()).unwrap();
// assert_eq!(v, val);
});
#[allow(clippy::as_conversions)]
<$ty as TryFromBytesTestable>::with_failing_test_cases(|c| {
let res = <$ty as TryFromBytes>::try_from_ref(c);
assert!(res.is_none(), "{}::is_bit_valid({:?}): got true, expected false", stringify!($ty), c);
});
#[allow(dead_code)]
const _: () = { static_assertions::assert_impl_all!($ty: TryFromBytes); };
};
($ty:ty: $trait:ident) => {
#[allow(dead_code)]
const _: () = { static_assertions::assert_impl_all!($ty: $trait); };
};
($ty:ty: !$trait:ident) => {
#[allow(dead_code)]
const _: () = { static_assertions::assert_not_impl_any!($ty: $trait); };
};
($ty:ty: $($trait:ident),* $(,)? $(!$negative_trait:ident),*) => {
$(
assert_impls!($ty: $trait);
)*
$(
assert_impls!($ty: !$negative_trait);
)*
};
}
// NOTE: The negative impl assertions here are not necessarily
// prescriptive. They merely serve as change detectors to make sure
// we're aware of what trait impls are getting added with a given
// change. Of course, some impls would be invalid (e.g., `bool:
// FromBytes`), and so this change detection is very important.
assert_impls!((): KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(u8: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(i8: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(u16: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(i16: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(u32: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(i32: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(u64: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(i64: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(u128: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(i128: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(usize: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(isize: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(f32: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(f64: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(bool: KnownLayout, TryFromBytes, FromZeroes, AsBytes, Unaligned, !FromBytes);
assert_impls!(char: KnownLayout, TryFromBytes, FromZeroes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(str: KnownLayout, TryFromBytes, FromZeroes, AsBytes, Unaligned, !FromBytes);
assert_impls!(NonZeroU8: KnownLayout, TryFromBytes, AsBytes, Unaligned, !FromZeroes, !FromBytes);
assert_impls!(NonZeroI8: KnownLayout, TryFromBytes, AsBytes, Unaligned, !FromZeroes, !FromBytes);
assert_impls!(NonZeroU16: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroI16: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroU32: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroI32: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroU64: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroI64: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroU128: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroI128: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroUsize: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(NonZeroIsize: KnownLayout, TryFromBytes, AsBytes, !FromBytes, !Unaligned);
assert_impls!(Option<NonZeroU8>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(Option<NonZeroI8>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(Option<NonZeroU16>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroI16>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroU32>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroI32>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroU64>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroI64>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroU128>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroI128>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroUsize>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
assert_impls!(Option<NonZeroIsize>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned);
// Implements none of the ZC traits.
struct NotZerocopy;
#[rustfmt::skip]
type FnManyArgs = fn(
NotZerocopy, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8,
) -> (NotZerocopy, NotZerocopy);
// Allowed, because we're not actually using this type for FFI.
#[allow(improper_ctypes_definitions)]
#[rustfmt::skip]
type ECFnManyArgs = extern "C" fn(
NotZerocopy, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8, u8,
) -> (NotZerocopy, NotZerocopy);
#[cfg(feature = "alloc")]
assert_impls!(Option<Box<UnsafeCell<NotZerocopy>>>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<Box<[UnsafeCell<NotZerocopy>]>>: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<&'static UnsafeCell<NotZerocopy>>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<&'static [UnsafeCell<NotZerocopy>]>: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<&'static mut UnsafeCell<NotZerocopy>>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<&'static mut [UnsafeCell<NotZerocopy>]>: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<NonNull<UnsafeCell<NotZerocopy>>>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<NonNull<[UnsafeCell<NotZerocopy>]>>: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<fn()>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<FnManyArgs>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<extern "C" fn()>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Option<ECFnManyArgs>: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(PhantomData<NotZerocopy>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(PhantomData<[u8]>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(ManuallyDrop<u8>: KnownLayout, FromZeroes, FromBytes, AsBytes, Unaligned, !TryFromBytes);
assert_impls!(ManuallyDrop<[u8]>: KnownLayout, FromZeroes, FromBytes, AsBytes, Unaligned, !TryFromBytes);
assert_impls!(ManuallyDrop<NotZerocopy>: !TryFromBytes, !KnownLayout, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(ManuallyDrop<[NotZerocopy]>: !TryFromBytes, !KnownLayout, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(MaybeUninit<u8>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, Unaligned, !AsBytes);
assert_impls!(MaybeUninit<NotZerocopy>: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Wrapping<u8>: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!(Wrapping<NotZerocopy>: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(Unalign<u8>: KnownLayout, FromZeroes, FromBytes, AsBytes, Unaligned, !TryFromBytes);
assert_impls!(Unalign<NotZerocopy>: Unaligned, !KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes);
assert_impls!([u8]: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, Unaligned);
assert_impls!([bool]: KnownLayout, TryFromBytes, FromZeroes, AsBytes, Unaligned, !FromBytes);
assert_impls!([NotZerocopy]: !KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!([u8; 0]: KnownLayout, FromZeroes, FromBytes, AsBytes, Unaligned, !TryFromBytes);
assert_impls!([NotZerocopy; 0]: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!([u8; 1]: KnownLayout, FromZeroes, FromBytes, AsBytes, Unaligned, !TryFromBytes);
assert_impls!([NotZerocopy; 1]: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(*const NotZerocopy: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(*mut NotZerocopy: KnownLayout, FromZeroes, !TryFromBytes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(*const [NotZerocopy]: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(*mut [NotZerocopy]: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(*const dyn Debug: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
assert_impls!(*mut dyn Debug: KnownLayout, !TryFromBytes, !FromZeroes, !FromBytes, !AsBytes, !Unaligned);
#[cfg(feature = "simd")]
{
#[allow(unused_macros)]
macro_rules! test_simd_arch_mod {
($arch:ident, $($typ:ident),*) => {
{
use core::arch::$arch::{$($typ),*};
use crate::*;
$( assert_impls!($typ: KnownLayout, TryFromBytes, FromZeroes, FromBytes, AsBytes, !Unaligned); )*
}
};
}
#[cfg(target_arch = "x86")]
test_simd_arch_mod!(x86, __m128, __m128d, __m128i, __m256, __m256d, __m256i);
#[cfg(all(feature = "simd-nightly", target_arch = "x86"))]
test_simd_arch_mod!(x86, __m512bh, __m512, __m512d, __m512i);
#[cfg(target_arch = "x86_64")]
test_simd_arch_mod!(x86_64, __m128, __m128d, __m128i, __m256, __m256d, __m256i);
#[cfg(all(feature = "simd-nightly", target_arch = "x86_64"))]
test_simd_arch_mod!(x86_64, __m512bh, __m512, __m512d, __m512i);
#[cfg(target_arch = "wasm32")]
test_simd_arch_mod!(wasm32, v128);
#[cfg(all(feature = "simd-nightly", target_arch = "powerpc"))]
test_simd_arch_mod!(
powerpc,
vector_bool_long,
vector_double,
vector_signed_long,
vector_unsigned_long
);
#[cfg(all(feature = "simd-nightly", target_arch = "powerpc64"))]
test_simd_arch_mod!(
powerpc64,
vector_bool_long,
vector_double,
vector_signed_long,
vector_unsigned_long
);
#[cfg(target_arch = "aarch64")]
#[rustfmt::skip]
test_simd_arch_mod!(
aarch64, float32x2_t, float32x4_t, float64x1_t, float64x2_t, int8x8_t, int8x8x2_t,
int8x8x3_t, int8x8x4_t, int8x16_t, int8x16x2_t, int8x16x3_t, int8x16x4_t, int16x4_t,
int16x8_t, int32x2_t, int32x4_t, int64x1_t, int64x2_t, poly8x8_t, poly8x8x2_t, poly8x8x3_t,
poly8x8x4_t, poly8x16_t, poly8x16x2_t, poly8x16x3_t, poly8x16x4_t, poly16x4_t, poly16x8_t,
poly64x1_t, poly64x2_t, uint8x8_t, uint8x8x2_t, uint8x8x3_t, uint8x8x4_t, uint8x16_t,
uint8x16x2_t, uint8x16x3_t, uint8x16x4_t, uint16x4_t, uint16x8_t, uint32x2_t, uint32x4_t,
uint64x1_t, uint64x2_t
);
#[cfg(all(feature = "simd-nightly", target_arch = "arm"))]
#[rustfmt::skip]
test_simd_arch_mod!(arm, int8x4_t, uint8x4_t);
}
}
}
#[cfg(kani)]
mod proofs {
use super::*;
impl kani::Arbitrary for DstLayout {
fn any() -> Self {
let align: NonZeroUsize = kani::any();
let size_info: SizeInfo = kani::any();
kani::assume(align.is_power_of_two());
kani::assume(align < DstLayout::THEORETICAL_MAX_ALIGN);
// For testing purposes, we most care about instantiations of
// `DstLayout` that can correspond to actual Rust types. We use
// `Layout` to verify that our `DstLayout` satisfies the validity
// conditions of Rust layouts.
kani::assume(
match size_info {
SizeInfo::Sized { _size } => Layout::from_size_align(_size, align.get()),
SizeInfo::SliceDst(TrailingSliceLayout { _offset, _elem_size }) => {
// `SliceDst`` cannot encode an exact size, but we know
// it is at least `_offset` bytes.
Layout::from_size_align(_offset, align.get())
}
}
.is_ok(),
);
Self { align: align, size_info: size_info }
}
}
impl kani::Arbitrary for SizeInfo {
fn any() -> Self {
let is_sized: bool = kani::any();
match is_sized {
true => {
let size: usize = kani::any();
kani::assume(size <= isize::MAX as _);
SizeInfo::Sized { _size: size }
}
false => SizeInfo::SliceDst(kani::any()),
}
}
}
impl kani::Arbitrary for TrailingSliceLayout {
fn any() -> Self {
let elem_size: usize = kani::any();
let offset: usize = kani::any();
kani::assume(elem_size < isize::MAX as _);
kani::assume(offset < isize::MAX as _);
TrailingSliceLayout { _elem_size: elem_size, _offset: offset }
}
}
#[kani::proof]
fn prove_dst_layout_extend() {
use crate::util::{core_layout::padding_needed_for, max, min};
let base: DstLayout = kani::any();
let field: DstLayout = kani::any();
let packed: Option<NonZeroUsize> = kani::any();
if let Some(max_align) = packed {
kani::assume(max_align.is_power_of_two());
kani::assume(base.align <= max_align);
}
// The base can only be extended if it's sized.
kani::assume(matches!(base.size_info, SizeInfo::Sized { .. }));
let base_size = if let SizeInfo::Sized { _size: size } = base.size_info {
size
} else {
unreachable!();
};
// Under the above conditions, `DstLayout::extend` will not panic.
let composite = base.extend(field, packed);
// The field's alignment is clamped by `max_align` (i.e., the
// `packed` attribute, if any) [1].
//
// [1] Per https://doc.rust-lang.org/reference/type-layout.html#the-alignment-modifiers:
//
// The alignments of each field, for the purpose of positioning
// fields, is the smaller of the specified alignment and the
// alignment of the field's type.
let field_align = min(field.align, packed.unwrap_or(DstLayout::THEORETICAL_MAX_ALIGN));
// The struct's alignment is the maximum of its previous alignment and
// `field_align`.
assert_eq!(composite.align, max(base.align, field_align));
// Compute the minimum amount of inter-field padding needed to
// satisfy the field's alignment, and offset of the trailing field.
// [1]
//
// [1] Per https://doc.rust-lang.org/reference/type-layout.html#the-alignment-modifiers:
//
// Inter-field padding is guaranteed to be the minimum required in
// order to satisfy each field's (possibly altered) alignment.
let padding = padding_needed_for(base_size, field_align);
let offset = base_size + padding;
// For testing purposes, we'll also construct `alloc::Layout`
// stand-ins for `DstLayout`, and show that `extend` behaves
// comparably on both types.
let base_analog = Layout::from_size_align(base_size, base.align.get()).unwrap();
match field.size_info {
SizeInfo::Sized { _size: field_size } => {
if let SizeInfo::Sized { _size: composite_size } = composite.size_info {
// If the trailing field is sized, the resulting layout
// will be sized. Its size will be the sum of the
// preceeding layout, the size of the new field, and the
// size of inter-field padding between the two.
assert_eq!(composite_size, offset + field_size);
let field_analog =
Layout::from_size_align(field_size, field_align.get()).unwrap();
if let Ok((actual_composite, actual_offset)) = base_analog.extend(field_analog)
{
assert_eq!(actual_offset, offset);
assert_eq!(actual_composite.size(), composite_size);
assert_eq!(actual_composite.align(), composite.align.get());
} else {
// An error here reflects that composite of `base`
// and `field` cannot correspond to a real Rust type
// fragment, because such a fragment would violate
// the basic invariants of a valid Rust layout. At
// the time of writing, `DstLayout` is a little more
// permissive than `Layout`, so we don't assert
// anything in this branch (e.g., unreachability).
}
} else {
panic!("The composite of two sized layouts must be sized.")
}
}
SizeInfo::SliceDst(TrailingSliceLayout {
_offset: field_offset,
_elem_size: field_elem_size,
}) => {
if let SizeInfo::SliceDst(TrailingSliceLayout {
_offset: composite_offset,
_elem_size: composite_elem_size,
}) = composite.size_info
{
// The offset of the trailing slice component is the sum
// of the offset of the trailing field and the trailing
// slice offset within that field.
assert_eq!(composite_offset, offset + field_offset);
// The elem size is unchanged.
assert_eq!(composite_elem_size, field_elem_size);
let field_analog =
Layout::from_size_align(field_offset, field_align.get()).unwrap();
if let Ok((actual_composite, actual_offset)) = base_analog.extend(field_analog)
{
assert_eq!(actual_offset, offset);
assert_eq!(actual_composite.size(), composite_offset);
assert_eq!(actual_composite.align(), composite.align.get());
} else {
// An error here reflects that composite of `base`
// and `field` cannot correspond to a real Rust type
// fragment, because such a fragment would violate
// the basic invariants of a valid Rust layout. At
// the time of writing, `DstLayout` is a little more
// permissive than `Layout`, so we don't assert
// anything in this branch (e.g., unreachability).
}
} else {
panic!("The extension of a layout with a DST must result in a DST.")
}
}
}
}
#[kani::proof]
#[kani::should_panic]
fn prove_dst_layout_extend_dst_panics() {
let base: DstLayout = kani::any();
let field: DstLayout = kani::any();
let packed: Option<NonZeroUsize> = kani::any();
if let Some(max_align) = packed {
kani::assume(max_align.is_power_of_two());
kani::assume(base.align <= max_align);
}
kani::assume(matches!(base.size_info, SizeInfo::SliceDst(..)));
let _ = base.extend(field, packed);
}
#[kani::proof]
fn prove_dst_layout_pad_to_align() {
use crate::util::core_layout::padding_needed_for;
let layout: DstLayout = kani::any();
let padded: DstLayout = layout.pad_to_align();
// Calling `pad_to_align` does not alter the `DstLayout`'s alignment.
assert_eq!(padded.align, layout.align);
if let SizeInfo::Sized { _size: unpadded_size } = layout.size_info {
if let SizeInfo::Sized { _size: padded_size } = padded.size_info {
// If the layout is sized, it will remain sized after padding is
// added. Its sum will be its unpadded size and the size of the
// trailing padding needed to satisfy its alignment
// requirements.
let padding = padding_needed_for(unpadded_size, layout.align);
assert_eq!(padded_size, unpadded_size + padding);
// Prove that calling `DstLayout::pad_to_align` behaves
// identically to `Layout::pad_to_align`.
let layout_analog =
Layout::from_size_align(unpadded_size, layout.align.get()).unwrap();
let padded_analog = layout_analog.pad_to_align();
assert_eq!(padded_analog.align(), layout.align.get());
assert_eq!(padded_analog.size(), padded_size);
} else {
panic!("The padding of a sized layout must result in a sized layout.")
}
} else {
// If the layout is a DST, padding cannot be statically added.
assert_eq!(padded.size_info, layout.size_info);
}
}
}