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
use crate::io::{Interest, Ready};
use crate::runtime::io::{ReadyEvent, Registration};
use crate::runtime::scheduler;
use mio::unix::SourceFd;
use std::error::Error;
use std::fmt;
use std::io;
use std::os::unix::io::{AsRawFd, RawFd};
use std::task::{ready, Context, Poll};
/// Associates an IO object backed by a Unix file descriptor with the tokio
/// reactor, allowing for readiness to be polled. The file descriptor must be of
/// a type that can be used with the OS polling facilities (ie, `poll`, `epoll`,
/// `kqueue`, etc), such as a network socket or pipe, and the file descriptor
/// must have the nonblocking mode set to true.
///
/// Creating an [`AsyncFd`] registers the file descriptor with the current tokio
/// Reactor, allowing you to directly await the file descriptor being readable
/// or writable. Once registered, the file descriptor remains registered until
/// the [`AsyncFd`] is dropped.
///
/// The [`AsyncFd`] takes ownership of an arbitrary object to represent the IO
/// object. It is intended that this object will handle closing the file
/// descriptor when it is dropped, avoiding resource leaks and ensuring that the
/// [`AsyncFd`] can clean up the registration before closing the file descriptor.
/// The [`AsyncFd::into_inner`] function can be used to extract the inner object
/// to retake control from the tokio IO reactor.
///
/// The inner object is required to implement [`AsRawFd`]. This file descriptor
/// must not change while [`AsyncFd`] owns the inner object, i.e. the
/// [`AsRawFd::as_raw_fd`] method on the inner type must always return the same
/// file descriptor when called multiple times. Failure to uphold this results
/// in unspecified behavior in the IO driver, which may include breaking
/// notifications for other sockets/etc.
///
/// Polling for readiness is done by calling the async functions [`readable`]
/// and [`writable`]. These functions complete when the associated readiness
/// condition is observed. Any number of tasks can query the same `AsyncFd` in
/// parallel, on the same or different conditions.
///
/// On some platforms, the readiness detecting mechanism relies on
/// edge-triggered notifications. This means that the OS will only notify Tokio
/// when the file descriptor transitions from not-ready to ready. For this to
/// work you should first try to read or write and only poll for readiness
/// if that fails with an error of [`std::io::ErrorKind::WouldBlock`].
///
/// Tokio internally tracks when it has received a ready notification, and when
/// readiness checking functions like [`readable`] and [`writable`] are called,
/// if the readiness flag is set, these async functions will complete
/// immediately. This however does mean that it is critical to ensure that this
/// ready flag is cleared when (and only when) the file descriptor ceases to be
/// ready. The [`AsyncFdReadyGuard`] returned from readiness checking functions
/// serves this function; after calling a readiness-checking async function,
/// you must use this [`AsyncFdReadyGuard`] to signal to tokio whether the file
/// descriptor is no longer in a ready state.
///
/// ## Use with to a poll-based API
///
/// In some cases it may be desirable to use `AsyncFd` from APIs similar to
/// [`TcpStream::poll_read_ready`]. The [`AsyncFd::poll_read_ready`] and
/// [`AsyncFd::poll_write_ready`] functions are provided for this purpose.
/// Because these functions don't create a future to hold their state, they have
/// the limitation that only one task can wait on each direction (read or write)
/// at a time.
///
/// # Examples
///
/// This example shows how to turn [`std::net::TcpStream`] asynchronous using
/// `AsyncFd`. It implements the read/write operations both as an `async fn`
/// and using the IO traits [`AsyncRead`] and [`AsyncWrite`].
///
/// ```no_run
/// use std::io::{self, Read, Write};
/// use std::net::TcpStream;
/// use std::pin::Pin;
/// use std::task::{ready, Context, Poll};
/// use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
/// use tokio::io::unix::AsyncFd;
///
/// pub struct AsyncTcpStream {
/// inner: AsyncFd<TcpStream>,
/// }
///
/// impl AsyncTcpStream {
/// pub fn new(tcp: TcpStream) -> io::Result<Self> {
/// tcp.set_nonblocking(true)?;
/// Ok(Self {
/// inner: AsyncFd::new(tcp)?,
/// })
/// }
///
/// pub async fn read(&self, out: &mut [u8]) -> io::Result<usize> {
/// loop {
/// let mut guard = self.inner.readable().await?;
///
/// match guard.try_io(|inner| inner.get_ref().read(out)) {
/// Ok(result) => return result,
/// Err(_would_block) => continue,
/// }
/// }
/// }
///
/// pub async fn write(&self, buf: &[u8]) -> io::Result<usize> {
/// loop {
/// let mut guard = self.inner.writable().await?;
///
/// match guard.try_io(|inner| inner.get_ref().write(buf)) {
/// Ok(result) => return result,
/// Err(_would_block) => continue,
/// }
/// }
/// }
/// }
///
/// impl AsyncRead for AsyncTcpStream {
/// fn poll_read(
/// self: Pin<&mut Self>,
/// cx: &mut Context<'_>,
/// buf: &mut ReadBuf<'_>
/// ) -> Poll<io::Result<()>> {
/// loop {
/// let mut guard = ready!(self.inner.poll_read_ready(cx))?;
///
/// let unfilled = buf.initialize_unfilled();
/// match guard.try_io(|inner| inner.get_ref().read(unfilled)) {
/// Ok(Ok(len)) => {
/// buf.advance(len);
/// return Poll::Ready(Ok(()));
/// },
/// Ok(Err(err)) => return Poll::Ready(Err(err)),
/// Err(_would_block) => continue,
/// }
/// }
/// }
/// }
///
/// impl AsyncWrite for AsyncTcpStream {
/// fn poll_write(
/// self: Pin<&mut Self>,
/// cx: &mut Context<'_>,
/// buf: &[u8]
/// ) -> Poll<io::Result<usize>> {
/// loop {
/// let mut guard = ready!(self.inner.poll_write_ready(cx))?;
///
/// match guard.try_io(|inner| inner.get_ref().write(buf)) {
/// Ok(result) => return Poll::Ready(result),
/// Err(_would_block) => continue,
/// }
/// }
/// }
///
/// fn poll_flush(
/// self: Pin<&mut Self>,
/// cx: &mut Context<'_>,
/// ) -> Poll<io::Result<()>> {
/// // tcp flush is a no-op
/// Poll::Ready(Ok(()))
/// }
///
/// fn poll_shutdown(
/// self: Pin<&mut Self>,
/// cx: &mut Context<'_>,
/// ) -> Poll<io::Result<()>> {
/// self.inner.get_ref().shutdown(std::net::Shutdown::Write)?;
/// Poll::Ready(Ok(()))
/// }
/// }
/// ```
///
/// [`readable`]: method@Self::readable
/// [`writable`]: method@Self::writable
/// [`AsyncFdReadyGuard`]: struct@self::AsyncFdReadyGuard
/// [`TcpStream::poll_read_ready`]: struct@crate::net::TcpStream
/// [`AsyncRead`]: trait@crate::io::AsyncRead
/// [`AsyncWrite`]: trait@crate::io::AsyncWrite
pub struct AsyncFd<T: AsRawFd> {
registration: Registration,
// The inner value is always present. the Option is required for `drop` and `into_inner`.
// In all other methods `unwrap` is valid, and will never panic.
inner: Option<T>,
}
/// Represents an IO-ready event detected on a particular file descriptor that
/// has not yet been acknowledged. This is a `must_use` structure to help ensure
/// that you do not forget to explicitly clear (or not clear) the event.
///
/// This type exposes an immutable reference to the underlying IO object.
#[must_use = "You must explicitly choose whether to clear the readiness state by calling a method on ReadyGuard"]
pub struct AsyncFdReadyGuard<'a, T: AsRawFd> {
async_fd: &'a AsyncFd<T>,
event: Option<ReadyEvent>,
}
/// Represents an IO-ready event detected on a particular file descriptor that
/// has not yet been acknowledged. This is a `must_use` structure to help ensure
/// that you do not forget to explicitly clear (or not clear) the event.
///
/// This type exposes a mutable reference to the underlying IO object.
#[must_use = "You must explicitly choose whether to clear the readiness state by calling a method on ReadyGuard"]
pub struct AsyncFdReadyMutGuard<'a, T: AsRawFd> {
async_fd: &'a mut AsyncFd<T>,
event: Option<ReadyEvent>,
}
impl<T: AsRawFd> AsyncFd<T> {
/// Creates an [`AsyncFd`] backed by (and taking ownership of) an object
/// implementing [`AsRawFd`]. The backing file descriptor is cached at the
/// time of creation.
///
/// Only configures the [`Interest::READABLE`] and [`Interest::WRITABLE`] interests. For more
/// control, use [`AsyncFd::with_interest`].
///
/// This method must be called in the context of a tokio runtime.
///
/// # Panics
///
/// This function panics if there is no current reactor set, or if the `rt`
/// feature flag is not enabled.
#[inline]
#[track_caller]
pub fn new(inner: T) -> io::Result<Self>
where
T: AsRawFd,
{
Self::with_interest(inner, Interest::READABLE | Interest::WRITABLE)
}
/// Creates an [`AsyncFd`] backed by (and taking ownership of) an object
/// implementing [`AsRawFd`], with a specific [`Interest`]. The backing
/// file descriptor is cached at the time of creation.
///
/// # Panics
///
/// This function panics if there is no current reactor set, or if the `rt`
/// feature flag is not enabled.
#[inline]
#[track_caller]
pub fn with_interest(inner: T, interest: Interest) -> io::Result<Self>
where
T: AsRawFd,
{
Self::new_with_handle_and_interest(inner, scheduler::Handle::current(), interest)
}
#[track_caller]
pub(crate) fn new_with_handle_and_interest(
inner: T,
handle: scheduler::Handle,
interest: Interest,
) -> io::Result<Self> {
Self::try_new_with_handle_and_interest(inner, handle, interest).map_err(Into::into)
}
/// Creates an [`AsyncFd`] backed by (and taking ownership of) an object
/// implementing [`AsRawFd`]. The backing file descriptor is cached at the
/// time of creation.
///
/// Only configures the [`Interest::READABLE`] and [`Interest::WRITABLE`] interests. For more
/// control, use [`AsyncFd::try_with_interest`].
///
/// This method must be called in the context of a tokio runtime.
///
/// In the case of failure, it returns [`AsyncFdTryNewError`] that contains the original object
/// passed to this function.
///
/// # Panics
///
/// This function panics if there is no current reactor set, or if the `rt`
/// feature flag is not enabled.
#[inline]
#[track_caller]
pub fn try_new(inner: T) -> Result<Self, AsyncFdTryNewError<T>>
where
T: AsRawFd,
{
Self::try_with_interest(inner, Interest::READABLE | Interest::WRITABLE)
}
/// Creates an [`AsyncFd`] backed by (and taking ownership of) an object
/// implementing [`AsRawFd`], with a specific [`Interest`]. The backing
/// file descriptor is cached at the time of creation.
///
/// In the case of failure, it returns [`AsyncFdTryNewError`] that contains the original object
/// passed to this function.
///
/// # Panics
///
/// This function panics if there is no current reactor set, or if the `rt`
/// feature flag is not enabled.
#[inline]
#[track_caller]
pub fn try_with_interest(inner: T, interest: Interest) -> Result<Self, AsyncFdTryNewError<T>>
where
T: AsRawFd,
{
Self::try_new_with_handle_and_interest(inner, scheduler::Handle::current(), interest)
}
#[track_caller]
pub(crate) fn try_new_with_handle_and_interest(
inner: T,
handle: scheduler::Handle,
interest: Interest,
) -> Result<Self, AsyncFdTryNewError<T>> {
let fd = inner.as_raw_fd();
match Registration::new_with_interest_and_handle(&mut SourceFd(&fd), interest, handle) {
Ok(registration) => Ok(AsyncFd {
registration,
inner: Some(inner),
}),
Err(cause) => Err(AsyncFdTryNewError { inner, cause }),
}
}
/// Returns a shared reference to the backing object of this [`AsyncFd`].
#[inline]
pub fn get_ref(&self) -> &T {
self.inner.as_ref().unwrap()
}
/// Returns a mutable reference to the backing object of this [`AsyncFd`].
#[inline]
pub fn get_mut(&mut self) -> &mut T {
self.inner.as_mut().unwrap()
}
fn take_inner(&mut self) -> Option<T> {
let inner = self.inner.take()?;
let fd = inner.as_raw_fd();
let _ = self.registration.deregister(&mut SourceFd(&fd));
Some(inner)
}
/// Deregisters this file descriptor and returns ownership of the backing
/// object.
pub fn into_inner(mut self) -> T {
self.take_inner().unwrap()
}
/// Polls for read readiness.
///
/// If the file descriptor is not currently ready for reading, this method
/// will store a clone of the [`Waker`] from the provided [`Context`]. When the
/// file descriptor becomes ready for reading, [`Waker::wake`] will be called.
///
/// Note that on multiple calls to [`poll_read_ready`] or
/// [`poll_read_ready_mut`], only the `Waker` from the `Context` passed to the
/// most recent call is scheduled to receive a wakeup. (However,
/// [`poll_write_ready`] retains a second, independent waker).
///
/// This method is intended for cases where creating and pinning a future
/// via [`readable`] is not feasible. Where possible, using [`readable`] is
/// preferred, as this supports polling from multiple tasks at once.
///
/// This method takes `&self`, so it is possible to call this method
/// concurrently with other methods on this struct. This method only
/// provides shared access to the inner IO resource when handling the
/// [`AsyncFdReadyGuard`].
///
/// [`poll_read_ready`]: method@Self::poll_read_ready
/// [`poll_read_ready_mut`]: method@Self::poll_read_ready_mut
/// [`poll_write_ready`]: method@Self::poll_write_ready
/// [`readable`]: method@Self::readable
/// [`Context`]: struct@std::task::Context
/// [`Waker`]: struct@std::task::Waker
/// [`Waker::wake`]: method@std::task::Waker::wake
pub fn poll_read_ready<'a>(
&'a self,
cx: &mut Context<'_>,
) -> Poll<io::Result<AsyncFdReadyGuard<'a, T>>> {
let event = ready!(self.registration.poll_read_ready(cx))?;
Poll::Ready(Ok(AsyncFdReadyGuard {
async_fd: self,
event: Some(event),
}))
}
/// Polls for read readiness.
///
/// If the file descriptor is not currently ready for reading, this method
/// will store a clone of the [`Waker`] from the provided [`Context`]. When the
/// file descriptor becomes ready for reading, [`Waker::wake`] will be called.
///
/// Note that on multiple calls to [`poll_read_ready`] or
/// [`poll_read_ready_mut`], only the `Waker` from the `Context` passed to the
/// most recent call is scheduled to receive a wakeup. (However,
/// [`poll_write_ready`] retains a second, independent waker).
///
/// This method is intended for cases where creating and pinning a future
/// via [`readable`] is not feasible. Where possible, using [`readable`] is
/// preferred, as this supports polling from multiple tasks at once.
///
/// This method takes `&mut self`, so it is possible to access the inner IO
/// resource mutably when handling the [`AsyncFdReadyMutGuard`].
///
/// [`poll_read_ready`]: method@Self::poll_read_ready
/// [`poll_read_ready_mut`]: method@Self::poll_read_ready_mut
/// [`poll_write_ready`]: method@Self::poll_write_ready
/// [`readable`]: method@Self::readable
/// [`Context`]: struct@std::task::Context
/// [`Waker`]: struct@std::task::Waker
/// [`Waker::wake`]: method@std::task::Waker::wake
pub fn poll_read_ready_mut<'a>(
&'a mut self,
cx: &mut Context<'_>,
) -> Poll<io::Result<AsyncFdReadyMutGuard<'a, T>>> {
let event = ready!(self.registration.poll_read_ready(cx))?;
Poll::Ready(Ok(AsyncFdReadyMutGuard {
async_fd: self,
event: Some(event),
}))
}
/// Polls for write readiness.
///
/// If the file descriptor is not currently ready for writing, this method
/// will store a clone of the [`Waker`] from the provided [`Context`]. When the
/// file descriptor becomes ready for writing, [`Waker::wake`] will be called.
///
/// Note that on multiple calls to [`poll_write_ready`] or
/// [`poll_write_ready_mut`], only the `Waker` from the `Context` passed to the
/// most recent call is scheduled to receive a wakeup. (However,
/// [`poll_read_ready`] retains a second, independent waker).
///
/// This method is intended for cases where creating and pinning a future
/// via [`writable`] is not feasible. Where possible, using [`writable`] is
/// preferred, as this supports polling from multiple tasks at once.
///
/// This method takes `&self`, so it is possible to call this method
/// concurrently with other methods on this struct. This method only
/// provides shared access to the inner IO resource when handling the
/// [`AsyncFdReadyGuard`].
///
/// [`poll_read_ready`]: method@Self::poll_read_ready
/// [`poll_write_ready`]: method@Self::poll_write_ready
/// [`poll_write_ready_mut`]: method@Self::poll_write_ready_mut
/// [`writable`]: method@Self::readable
/// [`Context`]: struct@std::task::Context
/// [`Waker`]: struct@std::task::Waker
/// [`Waker::wake`]: method@std::task::Waker::wake
pub fn poll_write_ready<'a>(
&'a self,
cx: &mut Context<'_>,
) -> Poll<io::Result<AsyncFdReadyGuard<'a, T>>> {
let event = ready!(self.registration.poll_write_ready(cx))?;
Poll::Ready(Ok(AsyncFdReadyGuard {
async_fd: self,
event: Some(event),
}))
}
/// Polls for write readiness.
///
/// If the file descriptor is not currently ready for writing, this method
/// will store a clone of the [`Waker`] from the provided [`Context`]. When the
/// file descriptor becomes ready for writing, [`Waker::wake`] will be called.
///
/// Note that on multiple calls to [`poll_write_ready`] or
/// [`poll_write_ready_mut`], only the `Waker` from the `Context` passed to the
/// most recent call is scheduled to receive a wakeup. (However,
/// [`poll_read_ready`] retains a second, independent waker).
///
/// This method is intended for cases where creating and pinning a future
/// via [`writable`] is not feasible. Where possible, using [`writable`] is
/// preferred, as this supports polling from multiple tasks at once.
///
/// This method takes `&mut self`, so it is possible to access the inner IO
/// resource mutably when handling the [`AsyncFdReadyMutGuard`].
///
/// [`poll_read_ready`]: method@Self::poll_read_ready
/// [`poll_write_ready`]: method@Self::poll_write_ready
/// [`poll_write_ready_mut`]: method@Self::poll_write_ready_mut
/// [`writable`]: method@Self::readable
/// [`Context`]: struct@std::task::Context
/// [`Waker`]: struct@std::task::Waker
/// [`Waker::wake`]: method@std::task::Waker::wake
pub fn poll_write_ready_mut<'a>(
&'a mut self,
cx: &mut Context<'_>,
) -> Poll<io::Result<AsyncFdReadyMutGuard<'a, T>>> {
let event = ready!(self.registration.poll_write_ready(cx))?;
Poll::Ready(Ok(AsyncFdReadyMutGuard {
async_fd: self,
event: Some(event),
}))
}
/// Waits for any of the requested ready states, returning a
/// [`AsyncFdReadyGuard`] that must be dropped to resume
/// polling for the requested ready states.
///
/// The function may complete without the file descriptor being ready. This is a
/// false-positive and attempting an operation will return with
/// `io::ErrorKind::WouldBlock`. The function can also return with an empty
/// [`Ready`] set, so you should always check the returned value and possibly
/// wait again if the requested states are not set.
///
/// When an IO operation does return `io::ErrorKind::WouldBlock`, the readiness must be cleared.
/// When a combined interest is used, it is important to clear only the readiness
/// that is actually observed to block. For instance when the combined
/// interest `Interest::READABLE | Interest::WRITABLE` is used, and a read blocks, only
/// read readiness should be cleared using the [`AsyncFdReadyGuard::clear_ready_matching`] method:
/// `guard.clear_ready_matching(Ready::READABLE)`.
/// Also clearing the write readiness in this case would be incorrect. The [`AsyncFdReadyGuard::clear_ready`]
/// method clears all readiness flags.
///
/// This method takes `&self`, so it is possible to call this method
/// concurrently with other methods on this struct. This method only
/// provides shared access to the inner IO resource when handling the
/// [`AsyncFdReadyGuard`].
///
/// # Examples
///
/// Concurrently read and write to a [`std::net::TcpStream`] on the same task without
/// splitting.
///
/// ```no_run
/// use std::error::Error;
/// use std::io;
/// use std::io::{Read, Write};
/// use std::net::TcpStream;
/// use tokio::io::unix::AsyncFd;
/// use tokio::io::{Interest, Ready};
///
/// #[tokio::main]
/// async fn main() -> Result<(), Box<dyn Error>> {
/// let stream = TcpStream::connect("127.0.0.1:8080")?;
/// stream.set_nonblocking(true)?;
/// let stream = AsyncFd::new(stream)?;
///
/// loop {
/// let mut guard = stream
/// .ready(Interest::READABLE | Interest::WRITABLE)
/// .await?;
///
/// if guard.ready().is_readable() {
/// let mut data = vec![0; 1024];
/// // Try to read data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match stream.get_ref().read(&mut data) {
/// Ok(n) => {
/// println!("read {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a read has blocked, but a write might still succeed.
/// // clear only the read readiness.
/// guard.clear_ready_matching(Ready::READABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
///
/// if guard.ready().is_writable() {
/// // Try to write data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match stream.get_ref().write(b"hello world") {
/// Ok(n) => {
/// println!("write {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a write has blocked, but a read might still succeed.
/// // clear only the write readiness.
/// guard.clear_ready_matching(Ready::WRITABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
/// }
/// }
/// ```
pub async fn ready(&self, interest: Interest) -> io::Result<AsyncFdReadyGuard<'_, T>> {
let event = self.registration.readiness(interest).await?;
Ok(AsyncFdReadyGuard {
async_fd: self,
event: Some(event),
})
}
/// Waits for any of the requested ready states, returning a
/// [`AsyncFdReadyMutGuard`] that must be dropped to resume
/// polling for the requested ready states.
///
/// The function may complete without the file descriptor being ready. This is a
/// false-positive and attempting an operation will return with
/// `io::ErrorKind::WouldBlock`. The function can also return with an empty
/// [`Ready`] set, so you should always check the returned value and possibly
/// wait again if the requested states are not set.
///
/// When an IO operation does return `io::ErrorKind::WouldBlock`, the readiness must be cleared.
/// When a combined interest is used, it is important to clear only the readiness
/// that is actually observed to block. For instance when the combined
/// interest `Interest::READABLE | Interest::WRITABLE` is used, and a read blocks, only
/// read readiness should be cleared using the [`AsyncFdReadyMutGuard::clear_ready_matching`] method:
/// `guard.clear_ready_matching(Ready::READABLE)`.
/// Also clearing the write readiness in this case would be incorrect.
/// The [`AsyncFdReadyMutGuard::clear_ready`] method clears all readiness flags.
///
/// This method takes `&mut self`, so it is possible to access the inner IO
/// resource mutably when handling the [`AsyncFdReadyMutGuard`].
///
/// # Examples
///
/// Concurrently read and write to a [`std::net::TcpStream`] on the same task without
/// splitting.
///
/// ```no_run
/// use std::error::Error;
/// use std::io;
/// use std::io::{Read, Write};
/// use std::net::TcpStream;
/// use tokio::io::unix::AsyncFd;
/// use tokio::io::{Interest, Ready};
///
/// #[tokio::main]
/// async fn main() -> Result<(), Box<dyn Error>> {
/// let stream = TcpStream::connect("127.0.0.1:8080")?;
/// stream.set_nonblocking(true)?;
/// let mut stream = AsyncFd::new(stream)?;
///
/// loop {
/// let mut guard = stream
/// .ready_mut(Interest::READABLE | Interest::WRITABLE)
/// .await?;
///
/// if guard.ready().is_readable() {
/// let mut data = vec![0; 1024];
/// // Try to read data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match guard.get_inner_mut().read(&mut data) {
/// Ok(n) => {
/// println!("read {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a read has blocked, but a write might still succeed.
/// // clear only the read readiness.
/// guard.clear_ready_matching(Ready::READABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
///
/// if guard.ready().is_writable() {
/// // Try to write data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match guard.get_inner_mut().write(b"hello world") {
/// Ok(n) => {
/// println!("write {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a write has blocked, but a read might still succeed.
/// // clear only the write readiness.
/// guard.clear_ready_matching(Ready::WRITABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
/// }
/// }
/// ```
pub async fn ready_mut(
&mut self,
interest: Interest,
) -> io::Result<AsyncFdReadyMutGuard<'_, T>> {
let event = self.registration.readiness(interest).await?;
Ok(AsyncFdReadyMutGuard {
async_fd: self,
event: Some(event),
})
}
/// Waits for the file descriptor to become readable, returning a
/// [`AsyncFdReadyGuard`] that must be dropped to resume read-readiness
/// polling.
///
/// This method takes `&self`, so it is possible to call this method
/// concurrently with other methods on this struct. This method only
/// provides shared access to the inner IO resource when handling the
/// [`AsyncFdReadyGuard`].
#[allow(clippy::needless_lifetimes)] // The lifetime improves rustdoc rendering.
pub async fn readable<'a>(&'a self) -> io::Result<AsyncFdReadyGuard<'a, T>> {
self.ready(Interest::READABLE).await
}
/// Waits for the file descriptor to become readable, returning a
/// [`AsyncFdReadyMutGuard`] that must be dropped to resume read-readiness
/// polling.
///
/// This method takes `&mut self`, so it is possible to access the inner IO
/// resource mutably when handling the [`AsyncFdReadyMutGuard`].
#[allow(clippy::needless_lifetimes)] // The lifetime improves rustdoc rendering.
pub async fn readable_mut<'a>(&'a mut self) -> io::Result<AsyncFdReadyMutGuard<'a, T>> {
self.ready_mut(Interest::READABLE).await
}
/// Waits for the file descriptor to become writable, returning a
/// [`AsyncFdReadyGuard`] that must be dropped to resume write-readiness
/// polling.
///
/// This method takes `&self`, so it is possible to call this method
/// concurrently with other methods on this struct. This method only
/// provides shared access to the inner IO resource when handling the
/// [`AsyncFdReadyGuard`].
#[allow(clippy::needless_lifetimes)] // The lifetime improves rustdoc rendering.
pub async fn writable<'a>(&'a self) -> io::Result<AsyncFdReadyGuard<'a, T>> {
self.ready(Interest::WRITABLE).await
}
/// Waits for the file descriptor to become writable, returning a
/// [`AsyncFdReadyMutGuard`] that must be dropped to resume write-readiness
/// polling.
///
/// This method takes `&mut self`, so it is possible to access the inner IO
/// resource mutably when handling the [`AsyncFdReadyMutGuard`].
#[allow(clippy::needless_lifetimes)] // The lifetime improves rustdoc rendering.
pub async fn writable_mut<'a>(&'a mut self) -> io::Result<AsyncFdReadyMutGuard<'a, T>> {
self.ready_mut(Interest::WRITABLE).await
}
/// Reads or writes from the file descriptor using a user-provided IO operation.
///
/// The `async_io` method is a convenience utility that waits for the file
/// descriptor to become ready, and then executes the provided IO operation.
/// Since file descriptors may be marked ready spuriously, the closure will
/// be called repeatedly until it returns something other than a
/// [`WouldBlock`] error. This is done using the following loop:
///
/// ```no_run
/// # use std::io::{self, Result};
/// # struct Dox<T> { inner: T }
/// # impl<T> Dox<T> {
/// # async fn writable(&self) -> Result<&Self> {
/// # Ok(self)
/// # }
/// # fn try_io<R>(&self, _: impl FnMut(&T) -> Result<R>) -> Result<Result<R>> {
/// # panic!()
/// # }
/// async fn async_io<R>(&self, mut f: impl FnMut(&T) -> io::Result<R>) -> io::Result<R> {
/// loop {
/// // or `readable` if called with the read interest.
/// let guard = self.writable().await?;
///
/// match guard.try_io(&mut f) {
/// Ok(result) => return result,
/// Err(_would_block) => continue,
/// }
/// }
/// }
/// # }
/// ```
///
/// The closure should only return a [`WouldBlock`] error if it has performed
/// an IO operation on the file descriptor that failed due to the file descriptor not being
/// ready. Returning a [`WouldBlock`] error in any other situation will
/// incorrectly clear the readiness flag, which can cause the file descriptor to
/// behave incorrectly.
///
/// The closure should not perform the IO operation using any of the methods
/// defined on the Tokio [`AsyncFd`] type, as this will mess with the
/// readiness flag and can cause the file descriptor to behave incorrectly.
///
/// This method is not intended to be used with combined interests.
/// The closure should perform only one type of IO operation, so it should not
/// require more than one ready state. This method may panic or sleep forever
/// if it is called with a combined interest.
///
/// # Examples
///
/// This example sends some bytes on the inner [`std::net::UdpSocket`]. The `async_io`
/// method waits for readiness, and retries if the send operation does block. This example
/// is equivalent to the one given for [`try_io`].
///
/// ```no_run
/// use tokio::io::{Interest, unix::AsyncFd};
///
/// use std::io;
/// use std::net::UdpSocket;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let socket = UdpSocket::bind("0.0.0.0:8080")?;
/// socket.set_nonblocking(true)?;
/// let async_fd = AsyncFd::new(socket)?;
///
/// let written = async_fd
/// .async_io(Interest::WRITABLE, |inner| inner.send(&[1, 2]))
/// .await?;
///
/// println!("wrote {written} bytes");
///
/// Ok(())
/// }
/// ```
///
/// [`try_io`]: AsyncFdReadyGuard::try_io
/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock
pub async fn async_io<R>(
&self,
interest: Interest,
mut f: impl FnMut(&T) -> io::Result<R>,
) -> io::Result<R> {
self.registration
.async_io(interest, || f(self.get_ref()))
.await
}
/// Reads or writes from the file descriptor using a user-provided IO operation.
///
/// The behavior is the same as [`async_io`], except that the closure can mutate the inner
/// value of the [`AsyncFd`].
///
/// [`async_io`]: AsyncFd::async_io
pub async fn async_io_mut<R>(
&mut self,
interest: Interest,
mut f: impl FnMut(&mut T) -> io::Result<R>,
) -> io::Result<R> {
self.registration
.async_io(interest, || f(self.inner.as_mut().unwrap()))
.await
}
}
impl<T: AsRawFd> AsRawFd for AsyncFd<T> {
fn as_raw_fd(&self) -> RawFd {
self.inner.as_ref().unwrap().as_raw_fd()
}
}
impl<T: AsRawFd> std::os::unix::io::AsFd for AsyncFd<T> {
fn as_fd(&self) -> std::os::unix::io::BorrowedFd<'_> {
unsafe { std::os::unix::io::BorrowedFd::borrow_raw(self.as_raw_fd()) }
}
}
impl<T: std::fmt::Debug + AsRawFd> std::fmt::Debug for AsyncFd<T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("AsyncFd")
.field("inner", &self.inner)
.finish()
}
}
impl<T: AsRawFd> Drop for AsyncFd<T> {
fn drop(&mut self) {
let _ = self.take_inner();
}
}
impl<'a, Inner: AsRawFd> AsyncFdReadyGuard<'a, Inner> {
/// Indicates to tokio that the file descriptor is no longer ready. All
/// internal readiness flags will be cleared, and tokio will wait for the
/// next edge-triggered readiness notification from the OS.
///
/// This function is commonly used with guards returned by [`AsyncFd::readable`] and
/// [`AsyncFd::writable`].
///
/// It is critical that this function not be called unless your code
/// _actually observes_ that the file descriptor is _not_ ready. Do not call
/// it simply because, for example, a read succeeded; it should be called
/// when a read is observed to block.
///
/// This method only clears readiness events that happened before the creation of this guard.
/// In other words, if the IO resource becomes ready between the creation of the guard and
/// this call to `clear_ready`, then the readiness is not actually cleared.
pub fn clear_ready(&mut self) {
if let Some(event) = self.event.take() {
self.async_fd.registration.clear_readiness(event);
}
}
/// Indicates to tokio that the file descriptor no longer has a specific readiness.
/// The internal readiness flag will be cleared, and tokio will wait for the
/// next edge-triggered readiness notification from the OS.
///
/// This function is useful in combination with the [`AsyncFd::ready`] method when a
/// combined interest like `Interest::READABLE | Interest::WRITABLE` is used.
///
/// It is critical that this function not be called unless your code
/// _actually observes_ that the file descriptor is _not_ ready for the provided `Ready`.
/// Do not call it simply because, for example, a read succeeded; it should be called
/// when a read is observed to block. Only clear the specific readiness that is observed to
/// block. For example when a read blocks when using a combined interest,
/// only clear `Ready::READABLE`.
///
/// This method only clears readiness events that happened before the creation of this guard.
/// In other words, if the IO resource becomes ready between the creation of the guard and
/// this call to `clear_ready`, then the readiness is not actually cleared.
///
/// # Examples
///
/// Concurrently read and write to a [`std::net::TcpStream`] on the same task without
/// splitting.
///
/// ```no_run
/// use std::error::Error;
/// use std::io;
/// use std::io::{Read, Write};
/// use std::net::TcpStream;
/// use tokio::io::unix::AsyncFd;
/// use tokio::io::{Interest, Ready};
///
/// #[tokio::main]
/// async fn main() -> Result<(), Box<dyn Error>> {
/// let stream = TcpStream::connect("127.0.0.1:8080")?;
/// stream.set_nonblocking(true)?;
/// let stream = AsyncFd::new(stream)?;
///
/// loop {
/// let mut guard = stream
/// .ready(Interest::READABLE | Interest::WRITABLE)
/// .await?;
///
/// if guard.ready().is_readable() {
/// let mut data = vec![0; 1024];
/// // Try to read data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match stream.get_ref().read(&mut data) {
/// Ok(n) => {
/// println!("read {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a read has blocked, but a write might still succeed.
/// // clear only the read readiness.
/// guard.clear_ready_matching(Ready::READABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
///
/// if guard.ready().is_writable() {
/// // Try to write data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match stream.get_ref().write(b"hello world") {
/// Ok(n) => {
/// println!("write {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a write has blocked, but a read might still succeed.
/// // clear only the write readiness.
/// guard.clear_ready_matching(Ready::WRITABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
/// }
/// }
/// ```
pub fn clear_ready_matching(&mut self, ready: Ready) {
if let Some(mut event) = self.event.take() {
self.async_fd
.registration
.clear_readiness(event.with_ready(ready));
// the event is no longer ready for the readiness that was just cleared
event.ready = event.ready - ready;
if !event.ready.is_empty() {
self.event = Some(event);
}
}
}
/// This method should be invoked when you intentionally want to keep the
/// ready flag asserted.
///
/// While this function is itself a no-op, it satisfies the `#[must_use]`
/// constraint on the [`AsyncFdReadyGuard`] type.
pub fn retain_ready(&mut self) {
// no-op
}
/// Get the [`Ready`] value associated with this guard.
///
/// This method will return the empty readiness state if
/// [`AsyncFdReadyGuard::clear_ready`] has been called on
/// the guard.
///
/// [`Ready`]: crate::io::Ready
pub fn ready(&self) -> Ready {
match &self.event {
Some(event) => event.ready,
None => Ready::EMPTY,
}
}
/// Performs the provided IO operation.
///
/// If `f` returns a [`WouldBlock`] error, the readiness state associated
/// with this file descriptor is cleared, and the method returns
/// `Err(TryIoError::WouldBlock)`. You will typically need to poll the
/// `AsyncFd` again when this happens.
///
/// This method helps ensure that the readiness state of the underlying file
/// descriptor remains in sync with the tokio-side readiness state, by
/// clearing the tokio-side state only when a [`WouldBlock`] condition
/// occurs. It is the responsibility of the caller to ensure that `f`
/// returns [`WouldBlock`] only if the file descriptor that originated this
/// `AsyncFdReadyGuard` no longer expresses the readiness state that was queried to
/// create this `AsyncFdReadyGuard`.
///
/// # Examples
///
/// This example sends some bytes to the inner [`std::net::UdpSocket`]. Waiting
/// for write-readiness and retrying when the send operation does block are explicit.
/// This example can be written more succinctly using [`AsyncFd::async_io`].
///
/// ```no_run
/// use tokio::io::unix::AsyncFd;
///
/// use std::io;
/// use std::net::UdpSocket;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let socket = UdpSocket::bind("0.0.0.0:8080")?;
/// socket.set_nonblocking(true)?;
/// let async_fd = AsyncFd::new(socket)?;
///
/// let written = loop {
/// let mut guard = async_fd.writable().await?;
/// match guard.try_io(|inner| inner.get_ref().send(&[1, 2])) {
/// Ok(result) => {
/// break result?;
/// }
/// Err(_would_block) => {
/// // try_io already cleared the file descriptor's readiness state
/// continue;
/// }
/// }
/// };
///
/// println!("wrote {written} bytes");
///
/// Ok(())
/// }
/// ```
///
/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock
// Alias for old name in 0.x
#[cfg_attr(docsrs, doc(alias = "with_io"))]
pub fn try_io<R>(
&mut self,
f: impl FnOnce(&'a AsyncFd<Inner>) -> io::Result<R>,
) -> Result<io::Result<R>, TryIoError> {
let result = f(self.async_fd);
match result {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {
self.clear_ready();
Err(TryIoError(()))
}
result => Ok(result),
}
}
/// Returns a shared reference to the inner [`AsyncFd`].
pub fn get_ref(&self) -> &'a AsyncFd<Inner> {
self.async_fd
}
/// Returns a shared reference to the backing object of the inner [`AsyncFd`].
pub fn get_inner(&self) -> &'a Inner {
self.get_ref().get_ref()
}
}
impl<'a, Inner: AsRawFd> AsyncFdReadyMutGuard<'a, Inner> {
/// Indicates to tokio that the file descriptor is no longer ready. All
/// internal readiness flags will be cleared, and tokio will wait for the
/// next edge-triggered readiness notification from the OS.
///
/// This function is commonly used with guards returned by [`AsyncFd::readable_mut`] and
/// [`AsyncFd::writable_mut`].
///
/// It is critical that this function not be called unless your code
/// _actually observes_ that the file descriptor is _not_ ready. Do not call
/// it simply because, for example, a read succeeded; it should be called
/// when a read is observed to block.
///
/// This method only clears readiness events that happened before the creation of this guard.
/// In other words, if the IO resource becomes ready between the creation of the guard and
/// this call to `clear_ready`, then the readiness is not actually cleared.
pub fn clear_ready(&mut self) {
if let Some(event) = self.event.take() {
self.async_fd.registration.clear_readiness(event);
}
}
/// Indicates to tokio that the file descriptor no longer has a specific readiness.
/// The internal readiness flag will be cleared, and tokio will wait for the
/// next edge-triggered readiness notification from the OS.
///
/// This function is useful in combination with the [`AsyncFd::ready_mut`] method when a
/// combined interest like `Interest::READABLE | Interest::WRITABLE` is used.
///
/// It is critical that this function not be called unless your code
/// _actually observes_ that the file descriptor is _not_ ready for the provided `Ready`.
/// Do not call it simply because, for example, a read succeeded; it should be called
/// when a read is observed to block. Only clear the specific readiness that is observed to
/// block. For example when a read blocks when using a combined interest,
/// only clear `Ready::READABLE`.
///
/// This method only clears readiness events that happened before the creation of this guard.
/// In other words, if the IO resource becomes ready between the creation of the guard and
/// this call to `clear_ready`, then the readiness is not actually cleared.
///
/// # Examples
///
/// Concurrently read and write to a [`std::net::TcpStream`] on the same task without
/// splitting.
///
/// ```no_run
/// use std::error::Error;
/// use std::io;
/// use std::io::{Read, Write};
/// use std::net::TcpStream;
/// use tokio::io::unix::AsyncFd;
/// use tokio::io::{Interest, Ready};
///
/// #[tokio::main]
/// async fn main() -> Result<(), Box<dyn Error>> {
/// let stream = TcpStream::connect("127.0.0.1:8080")?;
/// stream.set_nonblocking(true)?;
/// let mut stream = AsyncFd::new(stream)?;
///
/// loop {
/// let mut guard = stream
/// .ready_mut(Interest::READABLE | Interest::WRITABLE)
/// .await?;
///
/// if guard.ready().is_readable() {
/// let mut data = vec![0; 1024];
/// // Try to read data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match guard.get_inner_mut().read(&mut data) {
/// Ok(n) => {
/// println!("read {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a read has blocked, but a write might still succeed.
/// // clear only the read readiness.
/// guard.clear_ready_matching(Ready::READABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
///
/// if guard.ready().is_writable() {
/// // Try to write data, this may still fail with `WouldBlock`
/// // if the readiness event is a false positive.
/// match guard.get_inner_mut().write(b"hello world") {
/// Ok(n) => {
/// println!("write {} bytes", n);
/// }
/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
/// // a write has blocked, but a read might still succeed.
/// // clear only the write readiness.
/// guard.clear_ready_matching(Ready::WRITABLE);
/// continue;
/// }
/// Err(e) => {
/// return Err(e.into());
/// }
/// }
/// }
/// }
/// }
/// ```
pub fn clear_ready_matching(&mut self, ready: Ready) {
if let Some(mut event) = self.event.take() {
self.async_fd
.registration
.clear_readiness(event.with_ready(ready));
// the event is no longer ready for the readiness that was just cleared
event.ready = event.ready - ready;
if !event.ready.is_empty() {
self.event = Some(event);
}
}
}
/// This method should be invoked when you intentionally want to keep the
/// ready flag asserted.
///
/// While this function is itself a no-op, it satisfies the `#[must_use]`
/// constraint on the [`AsyncFdReadyGuard`] type.
pub fn retain_ready(&mut self) {
// no-op
}
/// Get the [`Ready`] value associated with this guard.
///
/// This method will return the empty readiness state if
/// [`AsyncFdReadyGuard::clear_ready`] has been called on
/// the guard.
///
/// [`Ready`]: super::Ready
pub fn ready(&self) -> Ready {
match &self.event {
Some(event) => event.ready,
None => Ready::EMPTY,
}
}
/// Performs the provided IO operation.
///
/// If `f` returns a [`WouldBlock`] error, the readiness state associated
/// with this file descriptor is cleared, and the method returns
/// `Err(TryIoError::WouldBlock)`. You will typically need to poll the
/// `AsyncFd` again when this happens.
///
/// This method helps ensure that the readiness state of the underlying file
/// descriptor remains in sync with the tokio-side readiness state, by
/// clearing the tokio-side state only when a [`WouldBlock`] condition
/// occurs. It is the responsibility of the caller to ensure that `f`
/// returns [`WouldBlock`] only if the file descriptor that originated this
/// `AsyncFdReadyGuard` no longer expresses the readiness state that was queried to
/// create this `AsyncFdReadyGuard`.
///
/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock
pub fn try_io<R>(
&mut self,
f: impl FnOnce(&mut AsyncFd<Inner>) -> io::Result<R>,
) -> Result<io::Result<R>, TryIoError> {
let result = f(self.async_fd);
match result {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {
self.clear_ready();
Err(TryIoError(()))
}
result => Ok(result),
}
}
/// Returns a shared reference to the inner [`AsyncFd`].
pub fn get_ref(&self) -> &AsyncFd<Inner> {
self.async_fd
}
/// Returns a mutable reference to the inner [`AsyncFd`].
pub fn get_mut(&mut self) -> &mut AsyncFd<Inner> {
self.async_fd
}
/// Returns a shared reference to the backing object of the inner [`AsyncFd`].
pub fn get_inner(&self) -> &Inner {
self.get_ref().get_ref()
}
/// Returns a mutable reference to the backing object of the inner [`AsyncFd`].
pub fn get_inner_mut(&mut self) -> &mut Inner {
self.get_mut().get_mut()
}
}
impl<'a, T: std::fmt::Debug + AsRawFd> std::fmt::Debug for AsyncFdReadyGuard<'a, T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("ReadyGuard")
.field("async_fd", &self.async_fd)
.finish()
}
}
impl<'a, T: std::fmt::Debug + AsRawFd> std::fmt::Debug for AsyncFdReadyMutGuard<'a, T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("MutReadyGuard")
.field("async_fd", &self.async_fd)
.finish()
}
}
/// The error type returned by [`try_io`].
///
/// This error indicates that the IO resource returned a [`WouldBlock`] error.
///
/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock
/// [`try_io`]: method@AsyncFdReadyGuard::try_io
#[derive(Debug)]
pub struct TryIoError(());
/// Error returned by [`try_new`] or [`try_with_interest`].
///
/// [`try_new`]: AsyncFd::try_new
/// [`try_with_interest`]: AsyncFd::try_with_interest
pub struct AsyncFdTryNewError<T> {
inner: T,
cause: io::Error,
}
impl<T> AsyncFdTryNewError<T> {
/// Returns the original object passed to [`try_new`] or [`try_with_interest`]
/// alongside the error that caused these functions to fail.
///
/// [`try_new`]: AsyncFd::try_new
/// [`try_with_interest`]: AsyncFd::try_with_interest
pub fn into_parts(self) -> (T, io::Error) {
(self.inner, self.cause)
}
}
impl<T> fmt::Display for AsyncFdTryNewError<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(&self.cause, f)
}
}
impl<T> fmt::Debug for AsyncFdTryNewError<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&self.cause, f)
}
}
impl<T> Error for AsyncFdTryNewError<T> {
fn source(&self) -> Option<&(dyn Error + 'static)> {
Some(&self.cause)
}
}
impl<T> From<AsyncFdTryNewError<T>> for io::Error {
fn from(value: AsyncFdTryNewError<T>) -> Self {
value.cause
}
}