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
/*!
Provides routines for interpolating capture group references.
That is, if a replacement string contains references like `$foo` or `${foo1}`,
then they are replaced with the corresponding capture values for the groups
named `foo` and `foo1`, respectively. Similarly, syntax like `$1` and `${1}`
is supported as well, with `1` corresponding to a capture group index and not
a name.
This module provides the free functions [`string`] and [`bytes`], which
interpolate Rust Unicode strings and byte strings, respectively.
# Format
These routines support two different kinds of capture references: unbraced and
braced.
For the unbraced format, the format supported is `$ref` where `name` can be
any character in the class `[0-9A-Za-z_]`. `ref` is always the longest
possible parse. So for example, `$1a` corresponds to the capture group named
`1a` and not the capture group at index `1`. If `ref` matches `^[0-9]+$`, then
it is treated as a capture group index itself and not a name.
For the braced format, the format supported is `${ref}` where `ref` can be any
sequence of bytes except for `}`. If no closing brace occurs, then it is not
considered a capture reference. As with the unbraced format, if `ref` matches
`^[0-9]+$`, then it is treated as a capture group index and not a name.
The braced format is useful for exerting precise control over the name of the
capture reference. For example, `${1}a` corresponds to the capture group
reference `1` followed by the letter `a`, where as `$1a` (as mentioned above)
corresponds to the capture group reference `1a`. The braced format is also
useful for expressing capture group names that use characters not supported by
the unbraced format. For example, `${foo[bar].baz}` refers to the capture group
named `foo[bar].baz`.
If a capture group reference is found and it does not refer to a valid capture
group, then it will be replaced with the empty string.
To write a literal `$`, use `$$`.
To be clear, and as exhibited via the type signatures in the routines in this
module, it is impossible for a replacement string to be invalid. A replacement
string may not have the intended semantics, but the interpolation procedure
itself can never fail.
*/
use alloc::string::String;
/// Accepts a replacement string and interpolates capture references with their
/// corresponding values.
///
/// `append` should be a function that appends the string value of a capture
/// group at a particular index to the string given. If the capture group
/// index is invalid, then nothing should be appended.
///
/// `name_to_index` should be a function that maps a capture group name to a
/// capture group index. If the given name doesn't exist, then `None` should
/// be returned.
///
/// Finally, `dst` is where the final interpolated contents should be written.
/// If `replacement` contains no capture group references, then `dst` will be
/// equivalent to `replacement`.
///
/// See the [module documentation](self) for details about the format
/// supported.
pub fn string(
mut replacement: &str,
mut append: impl FnMut(usize, &mut String),
mut name_to_index: impl FnMut(&str) -> Option<usize>,
dst: &mut String,
) {
while !replacement.is_empty() {
match replacement.find('$') {
None => break,
Some(i) => {
dst.push_str(&replacement[..i]);
replacement = &replacement[i..];
}
}
// Handle escaping of '$'.
if replacement.as_bytes().get(1).map_or(false, |&b| b == b'$') {
dst.push_str("$");
replacement = &replacement[2..];
continue;
}
debug_assert!(!replacement.is_empty());
let cap_ref = match find_cap_ref(replacement.as_bytes()) {
Some(cap_ref) => cap_ref,
None => {
dst.push_str("$");
replacement = &replacement[1..];
continue;
}
};
replacement = &replacement[cap_ref.end..];
match cap_ref.cap {
Ref::Number(i) => append(i, dst),
Ref::Named(name) => {
if let Some(i) = name_to_index(name) {
append(i, dst);
}
}
}
}
dst.push_str(replacement);
}
/*
This should be uncommented and used if we ever provide public APIs for
searching `&[u8]`.
/// Accepts a replacement byte string and interpolates capture references with
/// their corresponding values.
///
/// `append` should be a function that appends the byte string value of a
/// capture group at a particular index to the byte string given. If the
/// capture group index is invalid, then nothing should be appended.
///
/// `name_to_index` should be a function that maps a capture group name to a
/// capture group index. If the given name doesn't exist, then `None` should
/// be returned.
///
/// Finally, `dst` is where the final interpolated contents should be written.
/// If `replacement` contains no capture group references, then `dst` will be
/// equivalent to `replacement`.
///
/// See the [module documentation](self) for details about the format
/// supported.
pub fn bytes(
mut replacement: &[u8],
mut append: impl FnMut(usize, &mut Vec<u8>),
mut name_to_index: impl FnMut(&str) -> Option<usize>,
dst: &mut Vec<u8>,
) {
while !replacement.is_empty() {
match replacement.iter().position(|&b| b == b'$') {
None => break,
Some(i) => {
dst.extend_from_slice(&replacement[..i]);
replacement = &replacement[i..];
}
}
// Handle escaping of '$'.
if replacement.get(1).map_or(false, |&b| b == b'$') {
dst.push(b'$');
replacement = &replacement[2..];
continue;
}
debug_assert!(!replacement.is_empty());
let cap_ref = match find_cap_ref(replacement) {
Some(cap_ref) => cap_ref,
None => {
dst.push(b'$');
replacement = &replacement[1..];
continue;
}
};
replacement = &replacement[cap_ref.end..];
match cap_ref.cap {
Ref::Number(i) => append(i, dst),
Ref::Named(name) => {
if let Some(i) = name_to_index(name) {
append(i, dst);
}
}
}
}
dst.extend_from_slice(replacement);
}
*/
/// `CaptureRef` represents a reference to a capture group inside some text.
/// The reference is either a capture group name or a number.
///
/// It is also tagged with the position in the text following the
/// capture reference.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct CaptureRef<'a> {
cap: Ref<'a>,
end: usize,
}
/// A reference to a capture group in some text.
///
/// e.g., `$2`, `$foo`, `${foo}`.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum Ref<'a> {
Named(&'a str),
Number(usize),
}
impl<'a> From<&'a str> for Ref<'a> {
fn from(x: &'a str) -> Ref<'a> {
Ref::Named(x)
}
}
impl From<usize> for Ref<'static> {
fn from(x: usize) -> Ref<'static> {
Ref::Number(x)
}
}
/// Parses a possible reference to a capture group name in the given text,
/// starting at the beginning of `replacement`.
///
/// If no such valid reference could be found, None is returned.
///
/// Note that this returns a "possible" reference because this routine doesn't
/// know whether the reference is to a valid group or not. If it winds up not
/// being a valid reference, then it should be replaced with the empty string.
fn find_cap_ref(replacement: &[u8]) -> Option<CaptureRef<'_>> {
let mut i = 0;
let rep: &[u8] = replacement;
if rep.len() <= 1 || rep[0] != b'$' {
return None;
}
i += 1;
if rep[i] == b'{' {
return find_cap_ref_braced(rep, i + 1);
}
let mut cap_end = i;
while rep.get(cap_end).copied().map_or(false, is_valid_cap_letter) {
cap_end += 1;
}
if cap_end == i {
return None;
}
// We just verified that the range 0..cap_end is valid ASCII, so it must
// therefore be valid UTF-8. If we really cared, we could avoid this UTF-8
// check via an unchecked conversion or by parsing the number straight from
// &[u8].
let cap = core::str::from_utf8(&rep[i..cap_end])
.expect("valid UTF-8 capture name");
Some(CaptureRef {
cap: match cap.parse::<usize>() {
Ok(i) => Ref::Number(i),
Err(_) => Ref::Named(cap),
},
end: cap_end,
})
}
/// Looks for a braced reference, e.g., `${foo1}`. This assumes that an opening
/// brace has been found at `i-1` in `rep`. This then looks for a closing
/// brace and returns the capture reference within the brace.
fn find_cap_ref_braced(rep: &[u8], mut i: usize) -> Option<CaptureRef<'_>> {
assert_eq!(b'{', rep[i.checked_sub(1).unwrap()]);
let start = i;
while rep.get(i).map_or(false, |&b| b != b'}') {
i += 1;
}
if !rep.get(i).map_or(false, |&b| b == b'}') {
return None;
}
// When looking at braced names, we don't put any restrictions on the name,
// so it's possible it could be invalid UTF-8. But a capture group name
// can never be invalid UTF-8, so if we have invalid UTF-8, then we can
// safely return None.
let cap = match core::str::from_utf8(&rep[start..i]) {
Err(_) => return None,
Ok(cap) => cap,
};
Some(CaptureRef {
cap: match cap.parse::<usize>() {
Ok(i) => Ref::Number(i),
Err(_) => Ref::Named(cap),
},
end: i + 1,
})
}
/// Returns true if and only if the given byte is allowed in a capture name
/// written in non-brace form.
fn is_valid_cap_letter(b: u8) -> bool {
match b {
b'0'..=b'9' | b'a'..=b'z' | b'A'..=b'Z' | b'_' => true,
_ => false,
}
}
#[cfg(test)]
mod tests {
use alloc::{string::String, vec, vec::Vec};
use super::{find_cap_ref, CaptureRef};
macro_rules! find {
($name:ident, $text:expr) => {
#[test]
fn $name() {
assert_eq!(None, find_cap_ref($text.as_bytes()));
}
};
($name:ident, $text:expr, $capref:expr) => {
#[test]
fn $name() {
assert_eq!(Some($capref), find_cap_ref($text.as_bytes()));
}
};
}
macro_rules! c {
($name_or_number:expr, $pos:expr) => {
CaptureRef { cap: $name_or_number.into(), end: $pos }
};
}
find!(find_cap_ref1, "$foo", c!("foo", 4));
find!(find_cap_ref2, "${foo}", c!("foo", 6));
find!(find_cap_ref3, "$0", c!(0, 2));
find!(find_cap_ref4, "$5", c!(5, 2));
find!(find_cap_ref5, "$10", c!(10, 3));
// See https://github.com/rust-lang/regex/pull/585
// for more on characters following numbers
find!(find_cap_ref6, "$42a", c!("42a", 4));
find!(find_cap_ref7, "${42}a", c!(42, 5));
find!(find_cap_ref8, "${42");
find!(find_cap_ref9, "${42 ");
find!(find_cap_ref10, " $0 ");
find!(find_cap_ref11, "$");
find!(find_cap_ref12, " ");
find!(find_cap_ref13, "");
find!(find_cap_ref14, "$1-$2", c!(1, 2));
find!(find_cap_ref15, "$1_$2", c!("1_", 3));
find!(find_cap_ref16, "$x-$y", c!("x", 2));
find!(find_cap_ref17, "$x_$y", c!("x_", 3));
find!(find_cap_ref18, "${#}", c!("#", 4));
find!(find_cap_ref19, "${Z[}", c!("Z[", 5));
find!(find_cap_ref20, "${¾}", c!("¾", 5));
find!(find_cap_ref21, "${¾a}", c!("¾a", 6));
find!(find_cap_ref22, "${a¾}", c!("a¾", 6));
find!(find_cap_ref23, "${☃}", c!("☃", 6));
find!(find_cap_ref24, "${a☃}", c!("a☃", 7));
find!(find_cap_ref25, "${☃a}", c!("☃a", 7));
find!(find_cap_ref26, "${名字}", c!("名字", 9));
fn interpolate_string(
mut name_to_index: Vec<(&'static str, usize)>,
caps: Vec<&'static str>,
replacement: &str,
) -> String {
name_to_index.sort_by_key(|x| x.0);
let mut dst = String::new();
super::string(
replacement,
|i, dst| {
if let Some(&s) = caps.get(i) {
dst.push_str(s);
}
},
|name| -> Option<usize> {
name_to_index
.binary_search_by_key(&name, |x| x.0)
.ok()
.map(|i| name_to_index[i].1)
},
&mut dst,
);
dst
}
/*
fn interpolate_bytes(
mut name_to_index: Vec<(&'static str, usize)>,
caps: Vec<&'static str>,
replacement: &str,
) -> String {
name_to_index.sort_by_key(|x| x.0);
let mut dst = vec![];
super::bytes(
replacement.as_bytes(),
|i, dst| {
if let Some(&s) = caps.get(i) {
dst.extend_from_slice(s.as_bytes());
}
},
|name| -> Option<usize> {
name_to_index
.binary_search_by_key(&name, |x| x.0)
.ok()
.map(|i| name_to_index[i].1)
},
&mut dst,
);
String::from_utf8(dst).unwrap()
}
*/
macro_rules! interp {
($name:ident, $map:expr, $caps:expr, $hay:expr, $expected:expr $(,)*) => {
#[test]
fn $name() {
assert_eq!(
$expected,
interpolate_string($map, $caps, $hay),
"interpolate::string failed",
);
/*
assert_eq!(
$expected,
interpolate_bytes($map, $caps, $hay),
"interpolate::bytes failed",
);
*/
}
};
}
interp!(
interp1,
vec![("foo", 2)],
vec!["", "", "xxx"],
"test $foo test",
"test xxx test",
);
interp!(
interp2,
vec![("foo", 2)],
vec!["", "", "xxx"],
"test$footest",
"test",
);
interp!(
interp3,
vec![("foo", 2)],
vec!["", "", "xxx"],
"test${foo}test",
"testxxxtest",
);
interp!(
interp4,
vec![("foo", 2)],
vec!["", "", "xxx"],
"test$2test",
"test",
);
interp!(
interp5,
vec![("foo", 2)],
vec!["", "", "xxx"],
"test${2}test",
"testxxxtest",
);
interp!(
interp6,
vec![("foo", 2)],
vec!["", "", "xxx"],
"test $$foo test",
"test $foo test",
);
interp!(
interp7,
vec![("foo", 2)],
vec!["", "", "xxx"],
"test $foo",
"test xxx",
);
interp!(
interp8,
vec![("foo", 2)],
vec!["", "", "xxx"],
"$foo test",
"xxx test",
);
interp!(
interp9,
vec![("bar", 1), ("foo", 2)],
vec!["", "yyy", "xxx"],
"test $bar$foo",
"test yyyxxx",
);
interp!(
interp10,
vec![("bar", 1), ("foo", 2)],
vec!["", "yyy", "xxx"],
"test $ test",
"test $ test",
);
interp!(
interp11,
vec![("bar", 1), ("foo", 2)],
vec!["", "yyy", "xxx"],
"test ${} test",
"test test",
);
interp!(
interp12,
vec![("bar", 1), ("foo", 2)],
vec!["", "yyy", "xxx"],
"test ${ } test",
"test test",
);
interp!(
interp13,
vec![("bar", 1), ("foo", 2)],
vec!["", "yyy", "xxx"],
"test ${a b} test",
"test test",
);
interp!(
interp14,
vec![("bar", 1), ("foo", 2)],
vec!["", "yyy", "xxx"],
"test ${a} test",
"test test",
);
// This is a funny case where a braced reference is never closed, but
// within the unclosed braced reference, there is an unbraced reference.
// In this case, the braced reference is just treated literally and the
// unbraced reference is found.
interp!(
interp15,
vec![("bar", 1), ("foo", 2)],
vec!["", "yyy", "xxx"],
"test ${wat $bar ok",
"test ${wat yyy ok",
);
}