1//! String manipulation.
2//!
3//! For more details, see the [`std::str`] module.
4//!
5//! [`std::str`]: ../../std/str/index.html
6
7#![stable(feature = "rust1", since = "1.0.0")]
8
9mod converts;
10mod count;
11mod error;
12mod iter;
13mod traits;
14mod validations;
15
16use self::pattern::Pattern;
17use self::pattern::{DoubleEndedSearcher, ReverseSearcher, Searcher};
18
19use crate::ascii;
20use crate::char::{self, EscapeDebugExtArgs};
21use crate::mem;
22use crate::slice::{self, SliceIndex};
23
24pub mod pattern;
25
26mod lossy;
27#[unstable(feature = "utf8_chunks", issue = "99543")]
28pub use lossy::{Utf8Chunk, Utf8Chunks};
29
30#[stable(feature = "rust1", since = "1.0.0")]
31pub use converts::{from_utf8, from_utf8_unchecked};
32
33#[stable(feature = "str_mut_extras", since = "1.20.0")]
34pub use converts::{from_utf8_mut, from_utf8_unchecked_mut};
35
36#[unstable(feature = "str_from_raw_parts", issue = "119206")]
37pub use converts::{from_raw_parts, from_raw_parts_mut};
38
39#[stable(feature = "rust1", since = "1.0.0")]
40pub use error::{ParseBoolError, Utf8Error};
41
42#[stable(feature = "rust1", since = "1.0.0")]
43pub use traits::FromStr;
44
45#[stable(feature = "rust1", since = "1.0.0")]
46pub use iter::{Bytes, CharIndices, Chars, Lines, SplitWhitespace};
47
48#[stable(feature = "rust1", since = "1.0.0")]
49#[allow(deprecated)]
50pub use iter::LinesAny;
51
52#[stable(feature = "rust1", since = "1.0.0")]
53pub use iter::{RSplit, RSplitTerminator, Split, SplitTerminator};
54
55#[stable(feature = "rust1", since = "1.0.0")]
56pub use iter::{RSplitN, SplitN};
57
58#[stable(feature = "str_matches", since = "1.2.0")]
59pub use iter::{Matches, RMatches};
60
61#[stable(feature = "str_match_indices", since = "1.5.0")]
62pub use iter::{MatchIndices, RMatchIndices};
63
64#[stable(feature = "encode_utf16", since = "1.8.0")]
65pub use iter::EncodeUtf16;
66
67#[stable(feature = "str_escape", since = "1.34.0")]
68pub use iter::{EscapeDebug, EscapeDefault, EscapeUnicode};
69
70#[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
71pub use iter::SplitAsciiWhitespace;
72
73#[stable(feature = "split_inclusive", since = "1.51.0")]
74pub use iter::SplitInclusive;
75
76#[unstable(feature = "str_internals", issue = "none")]
77pub use validations::{next_code_point, utf8_char_width};
78
79use iter::MatchIndicesInternal;
80use iter::SplitInternal;
81use iter::{MatchesInternal, SplitNInternal};
82
83#[inline(never)]
84#[cold]
85#[track_caller]
86#[rustc_allow_const_fn_unstable(const_eval_select)]
87#[cfg(not(feature = "panic_immediate_abort"))]
88const fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
89 crate::intrinsics::const_eval_select((s, begin, end), _called_in_const:slice_error_fail_ct, _called_at_rt:slice_error_fail_rt)
90}
91
92#[cfg(feature = "panic_immediate_abort")]
93const fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
94 slice_error_fail_ct(s, begin, end)
95}
96
97#[track_caller]
98const fn slice_error_fail_ct(_: &str, _: usize, _: usize) -> ! {
99 panic!("failed to slice string");
100}
101
102#[track_caller]
103fn slice_error_fail_rt(s: &str, begin: usize, end: usize) -> ! {
104 const MAX_DISPLAY_LENGTH: usize = 256;
105 let trunc_len = s.floor_char_boundary(MAX_DISPLAY_LENGTH);
106 let s_trunc = &s[..trunc_len];
107 let ellipsis = if trunc_len < s.len() { "[...]" } else { "" };
108
109 // 1. out of bounds
110 if begin > s.len() || end > s.len() {
111 let oob_index = if begin > s.len() { begin } else { end };
112 panic!("byte index {oob_index} is out of bounds of `{s_trunc}`{ellipsis}");
113 }
114
115 // 2. begin <= end
116 assert!(
117 begin <= end,
118 "begin <= end ({} <= {}) when slicing `{}`{}",
119 begin,
120 end,
121 s_trunc,
122 ellipsis
123 );
124
125 // 3. character boundary
126 let index = if !s.is_char_boundary(begin) { begin } else { end };
127 // find the character
128 let char_start = s.floor_char_boundary(index);
129 // `char_start` must be less than len and a char boundary
130 let ch = s[char_start..].chars().next().unwrap();
131 let char_range = char_start..char_start + ch.len_utf8();
132 panic!(
133 "byte index {} is not a char boundary; it is inside {:?} (bytes {:?}) of `{}`{}",
134 index, ch, char_range, s_trunc, ellipsis
135 );
136}
137
138#[cfg(not(test))]
139impl str {
140 /// Returns the length of `self`.
141 ///
142 /// This length is in bytes, not [`char`]s or graphemes. In other words,
143 /// it might not be what a human considers the length of the string.
144 ///
145 /// [`char`]: prim@char
146 ///
147 /// # Examples
148 ///
149 /// ```
150 /// let len = "foo".len();
151 /// assert_eq!(3, len);
152 ///
153 /// assert_eq!("ƒoo".len(), 4); // fancy f!
154 /// assert_eq!("ƒoo".chars().count(), 3);
155 /// ```
156 #[stable(feature = "rust1", since = "1.0.0")]
157 #[rustc_const_stable(feature = "const_str_len", since = "1.39.0")]
158 #[must_use]
159 #[inline]
160 pub const fn len(&self) -> usize {
161 self.as_bytes().len()
162 }
163
164 /// Returns `true` if `self` has a length of zero bytes.
165 ///
166 /// # Examples
167 ///
168 /// ```
169 /// let s = "";
170 /// assert!(s.is_empty());
171 ///
172 /// let s = "not empty";
173 /// assert!(!s.is_empty());
174 /// ```
175 #[stable(feature = "rust1", since = "1.0.0")]
176 #[rustc_const_stable(feature = "const_str_is_empty", since = "1.39.0")]
177 #[must_use]
178 #[inline]
179 pub const fn is_empty(&self) -> bool {
180 self.len() == 0
181 }
182
183 /// Checks that `index`-th byte is the first byte in a UTF-8 code point
184 /// sequence or the end of the string.
185 ///
186 /// The start and end of the string (when `index == self.len()`) are
187 /// considered to be boundaries.
188 ///
189 /// Returns `false` if `index` is greater than `self.len()`.
190 ///
191 /// # Examples
192 ///
193 /// ```
194 /// let s = "Löwe 老虎 Léopard";
195 /// assert!(s.is_char_boundary(0));
196 /// // start of `老`
197 /// assert!(s.is_char_boundary(6));
198 /// assert!(s.is_char_boundary(s.len()));
199 ///
200 /// // second byte of `ö`
201 /// assert!(!s.is_char_boundary(2));
202 ///
203 /// // third byte of `老`
204 /// assert!(!s.is_char_boundary(8));
205 /// ```
206 #[must_use]
207 #[stable(feature = "is_char_boundary", since = "1.9.0")]
208 #[inline]
209 pub fn is_char_boundary(&self, index: usize) -> bool {
210 // 0 is always ok.
211 // Test for 0 explicitly so that it can optimize out the check
212 // easily and skip reading string data for that case.
213 // Note that optimizing `self.get(..index)` relies on this.
214 if index == 0 {
215 return true;
216 }
217
218 match self.as_bytes().get(index) {
219 // For `None` we have two options:
220 //
221 // - index == self.len()
222 // Empty strings are valid, so return true
223 // - index > self.len()
224 // In this case return false
225 //
226 // The check is placed exactly here, because it improves generated
227 // code on higher opt-levels. See PR #84751 for more details.
228 None => index == self.len(),
229
230 Some(&b) => b.is_utf8_char_boundary(),
231 }
232 }
233
234 /// Finds the closest `x` not exceeding `index` where `is_char_boundary(x)` is `true`.
235 ///
236 /// This method can help you truncate a string so that it's still valid UTF-8, but doesn't
237 /// exceed a given number of bytes. Note that this is done purely at the character level
238 /// and can still visually split graphemes, even though the underlying characters aren't
239 /// split. For example, the emoji 🧑‍🔬 (scientist) could be split so that the string only
240 /// includes 🧑 (person) instead.
241 ///
242 /// # Examples
243 ///
244 /// ```
245 /// #![feature(round_char_boundary)]
246 /// let s = "❤️🧡💛💚💙💜";
247 /// assert_eq!(s.len(), 26);
248 /// assert!(!s.is_char_boundary(13));
249 ///
250 /// let closest = s.floor_char_boundary(13);
251 /// assert_eq!(closest, 10);
252 /// assert_eq!(&s[..closest], "❤️🧡");
253 /// ```
254 #[unstable(feature = "round_char_boundary", issue = "93743")]
255 #[inline]
256 pub fn floor_char_boundary(&self, index: usize) -> usize {
257 if index >= self.len() {
258 self.len()
259 } else {
260 let lower_bound = index.saturating_sub(3);
261 let new_index = self.as_bytes()[lower_bound..=index]
262 .iter()
263 .rposition(|b| b.is_utf8_char_boundary());
264
265 // SAFETY: we know that the character boundary will be within four bytes
266 unsafe { lower_bound + new_index.unwrap_unchecked() }
267 }
268 }
269
270 /// Finds the closest `x` not below `index` where `is_char_boundary(x)` is `true`.
271 ///
272 /// If `index` is greater than the length of the string, this returns the length of the string.
273 ///
274 /// This method is the natural complement to [`floor_char_boundary`]. See that method
275 /// for more details.
276 ///
277 /// [`floor_char_boundary`]: str::floor_char_boundary
278 ///
279 ///
280 /// # Examples
281 ///
282 /// ```
283 /// #![feature(round_char_boundary)]
284 /// let s = "❤️🧡💛💚💙💜";
285 /// assert_eq!(s.len(), 26);
286 /// assert!(!s.is_char_boundary(13));
287 ///
288 /// let closest = s.ceil_char_boundary(13);
289 /// assert_eq!(closest, 14);
290 /// assert_eq!(&s[..closest], "❤️🧡💛");
291 /// ```
292 #[unstable(feature = "round_char_boundary", issue = "93743")]
293 #[inline]
294 pub fn ceil_char_boundary(&self, index: usize) -> usize {
295 if index > self.len() {
296 self.len()
297 } else {
298 let upper_bound = Ord::min(index + 4, self.len());
299 self.as_bytes()[index..upper_bound]
300 .iter()
301 .position(|b| b.is_utf8_char_boundary())
302 .map_or(upper_bound, |pos| pos + index)
303 }
304 }
305
306 /// Converts a string slice to a byte slice. To convert the byte slice back
307 /// into a string slice, use the [`from_utf8`] function.
308 ///
309 /// # Examples
310 ///
311 /// ```
312 /// let bytes = "bors".as_bytes();
313 /// assert_eq!(b"bors", bytes);
314 /// ```
315 #[stable(feature = "rust1", since = "1.0.0")]
316 #[rustc_const_stable(feature = "str_as_bytes", since = "1.39.0")]
317 #[must_use]
318 #[inline(always)]
319 #[allow(unused_attributes)]
320 pub const fn as_bytes(&self) -> &[u8] {
321 // SAFETY: const sound because we transmute two types with the same layout
322 unsafe { mem::transmute(self) }
323 }
324
325 /// Converts a mutable string slice to a mutable byte slice.
326 ///
327 /// # Safety
328 ///
329 /// The caller must ensure that the content of the slice is valid UTF-8
330 /// before the borrow ends and the underlying `str` is used.
331 ///
332 /// Use of a `str` whose contents are not valid UTF-8 is undefined behavior.
333 ///
334 /// # Examples
335 ///
336 /// Basic usage:
337 ///
338 /// ```
339 /// let mut s = String::from("Hello");
340 /// let bytes = unsafe { s.as_bytes_mut() };
341 ///
342 /// assert_eq!(b"Hello", bytes);
343 /// ```
344 ///
345 /// Mutability:
346 ///
347 /// ```
348 /// let mut s = String::from("🗻∈🌏");
349 ///
350 /// unsafe {
351 /// let bytes = s.as_bytes_mut();
352 ///
353 /// bytes[0] = 0xF0;
354 /// bytes[1] = 0x9F;
355 /// bytes[2] = 0x8D;
356 /// bytes[3] = 0x94;
357 /// }
358 ///
359 /// assert_eq!("🍔∈🌏", s);
360 /// ```
361 #[stable(feature = "str_mut_extras", since = "1.20.0")]
362 #[must_use]
363 #[inline(always)]
364 pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8] {
365 // SAFETY: the cast from `&str` to `&[u8]` is safe since `str`
366 // has the same layout as `&[u8]` (only std can make this guarantee).
367 // The pointer dereference is safe since it comes from a mutable reference which
368 // is guaranteed to be valid for writes.
369 unsafe { &mut *(self as *mut str as *mut [u8]) }
370 }
371
372 /// Converts a string slice to a raw pointer.
373 ///
374 /// As string slices are a slice of bytes, the raw pointer points to a
375 /// [`u8`]. This pointer will be pointing to the first byte of the string
376 /// slice.
377 ///
378 /// The caller must ensure that the returned pointer is never written to.
379 /// If you need to mutate the contents of the string slice, use [`as_mut_ptr`].
380 ///
381 /// [`as_mut_ptr`]: str::as_mut_ptr
382 ///
383 /// # Examples
384 ///
385 /// ```
386 /// let s = "Hello";
387 /// let ptr = s.as_ptr();
388 /// ```
389 #[stable(feature = "rust1", since = "1.0.0")]
390 #[rustc_const_stable(feature = "rustc_str_as_ptr", since = "1.32.0")]
391 #[rustc_never_returns_null_ptr]
392 #[must_use]
393 #[inline(always)]
394 pub const fn as_ptr(&self) -> *const u8 {
395 self as *const str as *const u8
396 }
397
398 /// Converts a mutable string slice to a raw pointer.
399 ///
400 /// As string slices are a slice of bytes, the raw pointer points to a
401 /// [`u8`]. This pointer will be pointing to the first byte of the string
402 /// slice.
403 ///
404 /// It is your responsibility to make sure that the string slice only gets
405 /// modified in a way that it remains valid UTF-8.
406 #[stable(feature = "str_as_mut_ptr", since = "1.36.0")]
407 #[rustc_never_returns_null_ptr]
408 #[must_use]
409 #[inline(always)]
410 pub fn as_mut_ptr(&mut self) -> *mut u8 {
411 self as *mut str as *mut u8
412 }
413
414 /// Returns a subslice of `str`.
415 ///
416 /// This is the non-panicking alternative to indexing the `str`. Returns
417 /// [`None`] whenever equivalent indexing operation would panic.
418 ///
419 /// # Examples
420 ///
421 /// ```
422 /// let v = String::from("🗻∈🌏");
423 ///
424 /// assert_eq!(Some("🗻"), v.get(0..4));
425 ///
426 /// // indices not on UTF-8 sequence boundaries
427 /// assert!(v.get(1..).is_none());
428 /// assert!(v.get(..8).is_none());
429 ///
430 /// // out of bounds
431 /// assert!(v.get(..42).is_none());
432 /// ```
433 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
434 #[inline]
435 pub fn get<I: SliceIndex<str>>(&self, i: I) -> Option<&I::Output> {
436 i.get(self)
437 }
438
439 /// Returns a mutable subslice of `str`.
440 ///
441 /// This is the non-panicking alternative to indexing the `str`. Returns
442 /// [`None`] whenever equivalent indexing operation would panic.
443 ///
444 /// # Examples
445 ///
446 /// ```
447 /// let mut v = String::from("hello");
448 /// // correct length
449 /// assert!(v.get_mut(0..5).is_some());
450 /// // out of bounds
451 /// assert!(v.get_mut(..42).is_none());
452 /// assert_eq!(Some("he"), v.get_mut(0..2).map(|v| &*v));
453 ///
454 /// assert_eq!("hello", v);
455 /// {
456 /// let s = v.get_mut(0..2);
457 /// let s = s.map(|s| {
458 /// s.make_ascii_uppercase();
459 /// &*s
460 /// });
461 /// assert_eq!(Some("HE"), s);
462 /// }
463 /// assert_eq!("HEllo", v);
464 /// ```
465 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
466 #[inline]
467 pub fn get_mut<I: SliceIndex<str>>(&mut self, i: I) -> Option<&mut I::Output> {
468 i.get_mut(self)
469 }
470
471 /// Returns an unchecked subslice of `str`.
472 ///
473 /// This is the unchecked alternative to indexing the `str`.
474 ///
475 /// # Safety
476 ///
477 /// Callers of this function are responsible that these preconditions are
478 /// satisfied:
479 ///
480 /// * The starting index must not exceed the ending index;
481 /// * Indexes must be within bounds of the original slice;
482 /// * Indexes must lie on UTF-8 sequence boundaries.
483 ///
484 /// Failing that, the returned string slice may reference invalid memory or
485 /// violate the invariants communicated by the `str` type.
486 ///
487 /// # Examples
488 ///
489 /// ```
490 /// let v = "🗻∈🌏";
491 /// unsafe {
492 /// assert_eq!("🗻", v.get_unchecked(0..4));
493 /// assert_eq!("∈", v.get_unchecked(4..7));
494 /// assert_eq!("🌏", v.get_unchecked(7..11));
495 /// }
496 /// ```
497 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
498 #[inline]
499 pub unsafe fn get_unchecked<I: SliceIndex<str>>(&self, i: I) -> &I::Output {
500 // SAFETY: the caller must uphold the safety contract for `get_unchecked`;
501 // the slice is dereferenceable because `self` is a safe reference.
502 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
503 unsafe { &*i.get_unchecked(self) }
504 }
505
506 /// Returns a mutable, unchecked subslice of `str`.
507 ///
508 /// This is the unchecked alternative to indexing the `str`.
509 ///
510 /// # Safety
511 ///
512 /// Callers of this function are responsible that these preconditions are
513 /// satisfied:
514 ///
515 /// * The starting index must not exceed the ending index;
516 /// * Indexes must be within bounds of the original slice;
517 /// * Indexes must lie on UTF-8 sequence boundaries.
518 ///
519 /// Failing that, the returned string slice may reference invalid memory or
520 /// violate the invariants communicated by the `str` type.
521 ///
522 /// # Examples
523 ///
524 /// ```
525 /// let mut v = String::from("🗻∈🌏");
526 /// unsafe {
527 /// assert_eq!("🗻", v.get_unchecked_mut(0..4));
528 /// assert_eq!("∈", v.get_unchecked_mut(4..7));
529 /// assert_eq!("🌏", v.get_unchecked_mut(7..11));
530 /// }
531 /// ```
532 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
533 #[inline]
534 pub unsafe fn get_unchecked_mut<I: SliceIndex<str>>(&mut self, i: I) -> &mut I::Output {
535 // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`;
536 // the slice is dereferenceable because `self` is a safe reference.
537 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
538 unsafe { &mut *i.get_unchecked_mut(self) }
539 }
540
541 /// Creates a string slice from another string slice, bypassing safety
542 /// checks.
543 ///
544 /// This is generally not recommended, use with caution! For a safe
545 /// alternative see [`str`] and [`Index`].
546 ///
547 /// [`Index`]: crate::ops::Index
548 ///
549 /// This new slice goes from `begin` to `end`, including `begin` but
550 /// excluding `end`.
551 ///
552 /// To get a mutable string slice instead, see the
553 /// [`slice_mut_unchecked`] method.
554 ///
555 /// [`slice_mut_unchecked`]: str::slice_mut_unchecked
556 ///
557 /// # Safety
558 ///
559 /// Callers of this function are responsible that three preconditions are
560 /// satisfied:
561 ///
562 /// * `begin` must not exceed `end`.
563 /// * `begin` and `end` must be byte positions within the string slice.
564 /// * `begin` and `end` must lie on UTF-8 sequence boundaries.
565 ///
566 /// # Examples
567 ///
568 /// ```
569 /// let s = "Löwe 老虎 Léopard";
570 ///
571 /// unsafe {
572 /// assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
573 /// }
574 ///
575 /// let s = "Hello, world!";
576 ///
577 /// unsafe {
578 /// assert_eq!("world", s.slice_unchecked(7, 12));
579 /// }
580 /// ```
581 #[stable(feature = "rust1", since = "1.0.0")]
582 #[deprecated(since = "1.29.0", note = "use `get_unchecked(begin..end)` instead")]
583 #[must_use]
584 #[inline]
585 pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str {
586 // SAFETY: the caller must uphold the safety contract for `get_unchecked`;
587 // the slice is dereferenceable because `self` is a safe reference.
588 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
589 unsafe { &*(begin..end).get_unchecked(self) }
590 }
591
592 /// Creates a string slice from another string slice, bypassing safety
593 /// checks.
594 /// This is generally not recommended, use with caution! For a safe
595 /// alternative see [`str`] and [`IndexMut`].
596 ///
597 /// [`IndexMut`]: crate::ops::IndexMut
598 ///
599 /// This new slice goes from `begin` to `end`, including `begin` but
600 /// excluding `end`.
601 ///
602 /// To get an immutable string slice instead, see the
603 /// [`slice_unchecked`] method.
604 ///
605 /// [`slice_unchecked`]: str::slice_unchecked
606 ///
607 /// # Safety
608 ///
609 /// Callers of this function are responsible that three preconditions are
610 /// satisfied:
611 ///
612 /// * `begin` must not exceed `end`.
613 /// * `begin` and `end` must be byte positions within the string slice.
614 /// * `begin` and `end` must lie on UTF-8 sequence boundaries.
615 #[stable(feature = "str_slice_mut", since = "1.5.0")]
616 #[deprecated(since = "1.29.0", note = "use `get_unchecked_mut(begin..end)` instead")]
617 #[inline]
618 pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str {
619 // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`;
620 // the slice is dereferenceable because `self` is a safe reference.
621 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
622 unsafe { &mut *(begin..end).get_unchecked_mut(self) }
623 }
624
625 /// Divide one string slice into two at an index.
626 ///
627 /// The argument, `mid`, should be a byte offset from the start of the
628 /// string. It must also be on the boundary of a UTF-8 code point.
629 ///
630 /// The two slices returned go from the start of the string slice to `mid`,
631 /// and from `mid` to the end of the string slice.
632 ///
633 /// To get mutable string slices instead, see the [`split_at_mut`]
634 /// method.
635 ///
636 /// [`split_at_mut`]: str::split_at_mut
637 ///
638 /// # Panics
639 ///
640 /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is past
641 /// the end of the last code point of the string slice. For a non-panicking
642 /// alternative see [`split_at_checked`](str::split_at_checked).
643 ///
644 /// # Examples
645 ///
646 /// ```
647 /// let s = "Per Martin-Löf";
648 ///
649 /// let (first, last) = s.split_at(3);
650 ///
651 /// assert_eq!("Per", first);
652 /// assert_eq!(" Martin-Löf", last);
653 /// ```
654 #[inline]
655 #[must_use]
656 #[stable(feature = "str_split_at", since = "1.4.0")]
657 pub fn split_at(&self, mid: usize) -> (&str, &str) {
658 match self.split_at_checked(mid) {
659 None => slice_error_fail(self, 0, mid),
660 Some(pair) => pair,
661 }
662 }
663
664 /// Divide one mutable string slice into two at an index.
665 ///
666 /// The argument, `mid`, should be a byte offset from the start of the
667 /// string. It must also be on the boundary of a UTF-8 code point.
668 ///
669 /// The two slices returned go from the start of the string slice to `mid`,
670 /// and from `mid` to the end of the string slice.
671 ///
672 /// To get immutable string slices instead, see the [`split_at`] method.
673 ///
674 /// [`split_at`]: str::split_at
675 ///
676 /// # Panics
677 ///
678 /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is past
679 /// the end of the last code point of the string slice. For a non-panicking
680 /// alternative see [`split_at_mut_checked`](str::split_at_mut_checked).
681 ///
682 /// # Examples
683 ///
684 /// ```
685 /// let mut s = "Per Martin-Löf".to_string();
686 /// {
687 /// let (first, last) = s.split_at_mut(3);
688 /// first.make_ascii_uppercase();
689 /// assert_eq!("PER", first);
690 /// assert_eq!(" Martin-Löf", last);
691 /// }
692 /// assert_eq!("PER Martin-Löf", s);
693 /// ```
694 #[inline]
695 #[must_use]
696 #[stable(feature = "str_split_at", since = "1.4.0")]
697 pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str) {
698 // is_char_boundary checks that the index is in [0, .len()]
699 if self.is_char_boundary(mid) {
700 // SAFETY: just checked that `mid` is on a char boundary.
701 unsafe { self.split_at_mut_unchecked(mid) }
702 } else {
703 slice_error_fail(self, 0, mid)
704 }
705 }
706
707 /// Divide one string slice into two at an index.
708 ///
709 /// The argument, `mid`, should be a valid byte offset from the start of the
710 /// string. It must also be on the boundary of a UTF-8 code point. The
711 /// method returns `None` if that’s not the case.
712 ///
713 /// The two slices returned go from the start of the string slice to `mid`,
714 /// and from `mid` to the end of the string slice.
715 ///
716 /// To get mutable string slices instead, see the [`split_at_mut_checked`]
717 /// method.
718 ///
719 /// [`split_at_mut_checked`]: str::split_at_mut_checked
720 ///
721 /// # Examples
722 ///
723 /// ```
724 /// #![feature(split_at_checked)]
725 ///
726 /// let s = "Per Martin-Löf";
727 ///
728 /// let (first, last) = s.split_at_checked(3).unwrap();
729 /// assert_eq!("Per", first);
730 /// assert_eq!(" Martin-Löf", last);
731 ///
732 /// assert_eq!(None, s.split_at_checked(13)); // Inside “ö”
733 /// assert_eq!(None, s.split_at_checked(16)); // Beyond the string length
734 /// ```
735 #[inline]
736 #[must_use]
737 #[unstable(feature = "split_at_checked", reason = "new API", issue = "119128")]
738 pub fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)> {
739 // is_char_boundary checks that the index is in [0, .len()]
740 if self.is_char_boundary(mid) {
741 // SAFETY: just checked that `mid` is on a char boundary.
742 Some(unsafe { (self.get_unchecked(0..mid), self.get_unchecked(mid..self.len())) })
743 } else {
744 None
745 }
746 }
747
748 /// Divide one mutable string slice into two at an index.
749 ///
750 /// The argument, `mid`, should be a valid byte offset from the start of the
751 /// string. It must also be on the boundary of a UTF-8 code point. The
752 /// method returns `None` if that’s not the case.
753 ///
754 /// The two slices returned go from the start of the string slice to `mid`,
755 /// and from `mid` to the end of the string slice.
756 ///
757 /// To get immutable string slices instead, see the [`split_at_checked`] method.
758 ///
759 /// [`split_at_checked`]: str::split_at_checked
760 ///
761 /// # Examples
762 ///
763 /// ```
764 /// #![feature(split_at_checked)]
765 ///
766 /// let mut s = "Per Martin-Löf".to_string();
767 /// if let Some((first, last)) = s.split_at_mut_checked(3) {
768 /// first.make_ascii_uppercase();
769 /// assert_eq!("PER", first);
770 /// assert_eq!(" Martin-Löf", last);
771 /// }
772 /// assert_eq!("PER Martin-Löf", s);
773 ///
774 /// assert_eq!(None, s.split_at_mut_checked(13)); // Inside “ö”
775 /// assert_eq!(None, s.split_at_mut_checked(16)); // Beyond the string length
776 /// ```
777 #[inline]
778 #[must_use]
779 #[unstable(feature = "split_at_checked", reason = "new API", issue = "119128")]
780 pub fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str)> {
781 // is_char_boundary checks that the index is in [0, .len()]
782 if self.is_char_boundary(mid) {
783 // SAFETY: just checked that `mid` is on a char boundary.
784 Some(unsafe { self.split_at_mut_unchecked(mid) })
785 } else {
786 None
787 }
788 }
789
790 /// Divide one string slice into two at an index.
791 ///
792 /// # Safety
793 ///
794 /// The caller must ensure that `mid` is a valid byte offset from the start
795 /// of the string and falls on the boundary of a UTF-8 code point.
796 unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut str, &mut str) {
797 let len = self.len();
798 let ptr = self.as_mut_ptr();
799 // SAFETY: caller guarantees `mid` is on a char boundary.
800 unsafe {
801 (
802 from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, mid)),
803 from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr.add(mid), len - mid)),
804 )
805 }
806 }
807
808 /// Returns an iterator over the [`char`]s of a string slice.
809 ///
810 /// As a string slice consists of valid UTF-8, we can iterate through a
811 /// string slice by [`char`]. This method returns such an iterator.
812 ///
813 /// It's important to remember that [`char`] represents a Unicode Scalar
814 /// Value, and might not match your idea of what a 'character' is. Iteration
815 /// over grapheme clusters may be what you actually want. This functionality
816 /// is not provided by Rust's standard library, check crates.io instead.
817 ///
818 /// # Examples
819 ///
820 /// Basic usage:
821 ///
822 /// ```
823 /// let word = "goodbye";
824 ///
825 /// let count = word.chars().count();
826 /// assert_eq!(7, count);
827 ///
828 /// let mut chars = word.chars();
829 ///
830 /// assert_eq!(Some('g'), chars.next());
831 /// assert_eq!(Some('o'), chars.next());
832 /// assert_eq!(Some('o'), chars.next());
833 /// assert_eq!(Some('d'), chars.next());
834 /// assert_eq!(Some('b'), chars.next());
835 /// assert_eq!(Some('y'), chars.next());
836 /// assert_eq!(Some('e'), chars.next());
837 ///
838 /// assert_eq!(None, chars.next());
839 /// ```
840 ///
841 /// Remember, [`char`]s might not match your intuition about characters:
842 ///
843 /// [`char`]: prim@char
844 ///
845 /// ```
846 /// let y = "y̆";
847 ///
848 /// let mut chars = y.chars();
849 ///
850 /// assert_eq!(Some('y'), chars.next()); // not 'y̆'
851 /// assert_eq!(Some('\u{0306}'), chars.next());
852 ///
853 /// assert_eq!(None, chars.next());
854 /// ```
855 #[stable(feature = "rust1", since = "1.0.0")]
856 #[inline]
857 pub fn chars(&self) -> Chars<'_> {
858 Chars { iter: self.as_bytes().iter() }
859 }
860
861 /// Returns an iterator over the [`char`]s of a string slice, and their
862 /// positions.
863 ///
864 /// As a string slice consists of valid UTF-8, we can iterate through a
865 /// string slice by [`char`]. This method returns an iterator of both
866 /// these [`char`]s, as well as their byte positions.
867 ///
868 /// The iterator yields tuples. The position is first, the [`char`] is
869 /// second.
870 ///
871 /// # Examples
872 ///
873 /// Basic usage:
874 ///
875 /// ```
876 /// let word = "goodbye";
877 ///
878 /// let count = word.char_indices().count();
879 /// assert_eq!(7, count);
880 ///
881 /// let mut char_indices = word.char_indices();
882 ///
883 /// assert_eq!(Some((0, 'g')), char_indices.next());
884 /// assert_eq!(Some((1, 'o')), char_indices.next());
885 /// assert_eq!(Some((2, 'o')), char_indices.next());
886 /// assert_eq!(Some((3, 'd')), char_indices.next());
887 /// assert_eq!(Some((4, 'b')), char_indices.next());
888 /// assert_eq!(Some((5, 'y')), char_indices.next());
889 /// assert_eq!(Some((6, 'e')), char_indices.next());
890 ///
891 /// assert_eq!(None, char_indices.next());
892 /// ```
893 ///
894 /// Remember, [`char`]s might not match your intuition about characters:
895 ///
896 /// [`char`]: prim@char
897 ///
898 /// ```
899 /// let yes = "y̆es";
900 ///
901 /// let mut char_indices = yes.char_indices();
902 ///
903 /// assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
904 /// assert_eq!(Some((1, '\u{0306}')), char_indices.next());
905 ///
906 /// // note the 3 here - the previous character took up two bytes
907 /// assert_eq!(Some((3, 'e')), char_indices.next());
908 /// assert_eq!(Some((4, 's')), char_indices.next());
909 ///
910 /// assert_eq!(None, char_indices.next());
911 /// ```
912 #[stable(feature = "rust1", since = "1.0.0")]
913 #[inline]
914 pub fn char_indices(&self) -> CharIndices<'_> {
915 CharIndices { front_offset: 0, iter: self.chars() }
916 }
917
918 /// An iterator over the bytes of a string slice.
919 ///
920 /// As a string slice consists of a sequence of bytes, we can iterate
921 /// through a string slice by byte. This method returns such an iterator.
922 ///
923 /// # Examples
924 ///
925 /// ```
926 /// let mut bytes = "bors".bytes();
927 ///
928 /// assert_eq!(Some(b'b'), bytes.next());
929 /// assert_eq!(Some(b'o'), bytes.next());
930 /// assert_eq!(Some(b'r'), bytes.next());
931 /// assert_eq!(Some(b's'), bytes.next());
932 ///
933 /// assert_eq!(None, bytes.next());
934 /// ```
935 #[stable(feature = "rust1", since = "1.0.0")]
936 #[inline]
937 pub fn bytes(&self) -> Bytes<'_> {
938 Bytes(self.as_bytes().iter().copied())
939 }
940
941 /// Splits a string slice by whitespace.
942 ///
943 /// The iterator returned will return string slices that are sub-slices of
944 /// the original string slice, separated by any amount of whitespace.
945 ///
946 /// 'Whitespace' is defined according to the terms of the Unicode Derived
947 /// Core Property `White_Space`. If you only want to split on ASCII whitespace
948 /// instead, use [`split_ascii_whitespace`].
949 ///
950 /// [`split_ascii_whitespace`]: str::split_ascii_whitespace
951 ///
952 /// # Examples
953 ///
954 /// Basic usage:
955 ///
956 /// ```
957 /// let mut iter = "A few words".split_whitespace();
958 ///
959 /// assert_eq!(Some("A"), iter.next());
960 /// assert_eq!(Some("few"), iter.next());
961 /// assert_eq!(Some("words"), iter.next());
962 ///
963 /// assert_eq!(None, iter.next());
964 /// ```
965 ///
966 /// All kinds of whitespace are considered:
967 ///
968 /// ```
969 /// let mut iter = " Mary had\ta\u{2009}little \n\t lamb".split_whitespace();
970 /// assert_eq!(Some("Mary"), iter.next());
971 /// assert_eq!(Some("had"), iter.next());
972 /// assert_eq!(Some("a"), iter.next());
973 /// assert_eq!(Some("little"), iter.next());
974 /// assert_eq!(Some("lamb"), iter.next());
975 ///
976 /// assert_eq!(None, iter.next());
977 /// ```
978 ///
979 /// If the string is empty or all whitespace, the iterator yields no string slices:
980 /// ```
981 /// assert_eq!("".split_whitespace().next(), None);
982 /// assert_eq!(" ".split_whitespace().next(), None);
983 /// ```
984 #[must_use = "this returns the split string as an iterator, \
985 without modifying the original"]
986 #[stable(feature = "split_whitespace", since = "1.1.0")]
987 #[cfg_attr(not(test), rustc_diagnostic_item = "str_split_whitespace")]
988 #[inline]
989 pub fn split_whitespace(&self) -> SplitWhitespace<'_> {
990 SplitWhitespace { inner: self.split(IsWhitespace).filter(IsNotEmpty) }
991 }
992
993 /// Splits a string slice by ASCII whitespace.
994 ///
995 /// The iterator returned will return string slices that are sub-slices of
996 /// the original string slice, separated by any amount of ASCII whitespace.
997 ///
998 /// To split by Unicode `Whitespace` instead, use [`split_whitespace`].
999 ///
1000 /// [`split_whitespace`]: str::split_whitespace
1001 ///
1002 /// # Examples
1003 ///
1004 /// Basic usage:
1005 ///
1006 /// ```
1007 /// let mut iter = "A few words".split_ascii_whitespace();
1008 ///
1009 /// assert_eq!(Some("A"), iter.next());
1010 /// assert_eq!(Some("few"), iter.next());
1011 /// assert_eq!(Some("words"), iter.next());
1012 ///
1013 /// assert_eq!(None, iter.next());
1014 /// ```
1015 ///
1016 /// All kinds of ASCII whitespace are considered:
1017 ///
1018 /// ```
1019 /// let mut iter = " Mary had\ta little \n\t lamb".split_ascii_whitespace();
1020 /// assert_eq!(Some("Mary"), iter.next());
1021 /// assert_eq!(Some("had"), iter.next());
1022 /// assert_eq!(Some("a"), iter.next());
1023 /// assert_eq!(Some("little"), iter.next());
1024 /// assert_eq!(Some("lamb"), iter.next());
1025 ///
1026 /// assert_eq!(None, iter.next());
1027 /// ```
1028 ///
1029 /// If the string is empty or all ASCII whitespace, the iterator yields no string slices:
1030 /// ```
1031 /// assert_eq!("".split_ascii_whitespace().next(), None);
1032 /// assert_eq!(" ".split_ascii_whitespace().next(), None);
1033 /// ```
1034 #[must_use = "this returns the split string as an iterator, \
1035 without modifying the original"]
1036 #[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
1037 #[inline]
1038 pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace<'_> {
1039 let inner =
1040 self.as_bytes().split(IsAsciiWhitespace).filter(BytesIsNotEmpty).map(UnsafeBytesToStr);
1041 SplitAsciiWhitespace { inner }
1042 }
1043
1044 /// An iterator over the lines of a string, as string slices.
1045 ///
1046 /// Lines are split at line endings that are either newlines (`\n`) or
1047 /// sequences of a carriage return followed by a line feed (`\r\n`).
1048 ///
1049 /// Line terminators are not included in the lines returned by the iterator.
1050 ///
1051 /// Note that any carriage return (`\r`) not immediately followed by a
1052 /// line feed (`\n`) does not split a line. These carriage returns are
1053 /// thereby included in the produced lines.
1054 ///
1055 /// The final line ending is optional. A string that ends with a final line
1056 /// ending will return the same lines as an otherwise identical string
1057 /// without a final line ending.
1058 ///
1059 /// # Examples
1060 ///
1061 /// Basic usage:
1062 ///
1063 /// ```
1064 /// let text = "foo\r\nbar\n\nbaz\r";
1065 /// let mut lines = text.lines();
1066 ///
1067 /// assert_eq!(Some("foo"), lines.next());
1068 /// assert_eq!(Some("bar"), lines.next());
1069 /// assert_eq!(Some(""), lines.next());
1070 /// // Trailing carriage return is included in the last line
1071 /// assert_eq!(Some("baz\r"), lines.next());
1072 ///
1073 /// assert_eq!(None, lines.next());
1074 /// ```
1075 ///
1076 /// The final line does not require any ending:
1077 ///
1078 /// ```
1079 /// let text = "foo\nbar\n\r\nbaz";
1080 /// let mut lines = text.lines();
1081 ///
1082 /// assert_eq!(Some("foo"), lines.next());
1083 /// assert_eq!(Some("bar"), lines.next());
1084 /// assert_eq!(Some(""), lines.next());
1085 /// assert_eq!(Some("baz"), lines.next());
1086 ///
1087 /// assert_eq!(None, lines.next());
1088 /// ```
1089 #[stable(feature = "rust1", since = "1.0.0")]
1090 #[inline]
1091 pub fn lines(&self) -> Lines<'_> {
1092 Lines(self.split_inclusive('\n').map(LinesMap))
1093 }
1094
1095 /// An iterator over the lines of a string.
1096 #[stable(feature = "rust1", since = "1.0.0")]
1097 #[deprecated(since = "1.4.0", note = "use lines() instead now", suggestion = "lines")]
1098 #[inline]
1099 #[allow(deprecated)]
1100 pub fn lines_any(&self) -> LinesAny<'_> {
1101 LinesAny(self.lines())
1102 }
1103
1104 /// Returns an iterator of `u16` over the string encoded as UTF-16.
1105 ///
1106 /// # Examples
1107 ///
1108 /// ```
1109 /// let text = "Zażółć gęślą jaźń";
1110 ///
1111 /// let utf8_len = text.len();
1112 /// let utf16_len = text.encode_utf16().count();
1113 ///
1114 /// assert!(utf16_len <= utf8_len);
1115 /// ```
1116 #[must_use = "this returns the encoded string as an iterator, \
1117 without modifying the original"]
1118 #[stable(feature = "encode_utf16", since = "1.8.0")]
1119 pub fn encode_utf16(&self) -> EncodeUtf16<'_> {
1120 EncodeUtf16 { chars: self.chars(), extra: 0 }
1121 }
1122
1123 /// Returns `true` if the given pattern matches a sub-slice of
1124 /// this string slice.
1125 ///
1126 /// Returns `false` if it does not.
1127 ///
1128 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1129 /// function or closure that determines if a character matches.
1130 ///
1131 /// [`char`]: prim@char
1132 /// [pattern]: self::pattern
1133 ///
1134 /// # Examples
1135 ///
1136 /// ```
1137 /// let bananas = "bananas";
1138 ///
1139 /// assert!(bananas.contains("nana"));
1140 /// assert!(!bananas.contains("apples"));
1141 /// ```
1142 #[stable(feature = "rust1", since = "1.0.0")]
1143 #[inline]
1144 pub fn contains<'a, P: Pattern<'a>>(&'a self, pat: P) -> bool {
1145 pat.is_contained_in(self)
1146 }
1147
1148 /// Returns `true` if the given pattern matches a prefix of this
1149 /// string slice.
1150 ///
1151 /// Returns `false` if it does not.
1152 ///
1153 /// The [pattern] can be a `&str`, in which case this function will return true if
1154 /// the `&str` is a prefix of this string slice.
1155 ///
1156 /// The [pattern] can also be a [`char`], a slice of [`char`]s, or a
1157 /// function or closure that determines if a character matches.
1158 /// These will only be checked against the first character of this string slice.
1159 /// Look at the second example below regarding behavior for slices of [`char`]s.
1160 ///
1161 /// [`char`]: prim@char
1162 /// [pattern]: self::pattern
1163 ///
1164 /// # Examples
1165 ///
1166 /// ```
1167 /// let bananas = "bananas";
1168 ///
1169 /// assert!(bananas.starts_with("bana"));
1170 /// assert!(!bananas.starts_with("nana"));
1171 /// ```
1172 ///
1173 /// ```
1174 /// let bananas = "bananas";
1175 ///
1176 /// // Note that both of these assert successfully.
1177 /// assert!(bananas.starts_with(&['b', 'a', 'n', 'a']));
1178 /// assert!(bananas.starts_with(&['a', 'b', 'c', 'd']));
1179 /// ```
1180 #[stable(feature = "rust1", since = "1.0.0")]
1181 pub fn starts_with<'a, P: Pattern<'a>>(&'a self, pat: P) -> bool {
1182 pat.is_prefix_of(self)
1183 }
1184
1185 /// Returns `true` if the given pattern matches a suffix of this
1186 /// string slice.
1187 ///
1188 /// Returns `false` if it does not.
1189 ///
1190 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1191 /// function or closure that determines if a character matches.
1192 ///
1193 /// [`char`]: prim@char
1194 /// [pattern]: self::pattern
1195 ///
1196 /// # Examples
1197 ///
1198 /// ```
1199 /// let bananas = "bananas";
1200 ///
1201 /// assert!(bananas.ends_with("anas"));
1202 /// assert!(!bananas.ends_with("nana"));
1203 /// ```
1204 #[stable(feature = "rust1", since = "1.0.0")]
1205 pub fn ends_with<'a, P>(&'a self, pat: P) -> bool
1206 where
1207 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1208 {
1209 pat.is_suffix_of(self)
1210 }
1211
1212 /// Returns the byte index of the first character of this string slice that
1213 /// matches the pattern.
1214 ///
1215 /// Returns [`None`] if the pattern doesn't match.
1216 ///
1217 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1218 /// function or closure that determines if a character matches.
1219 ///
1220 /// [`char`]: prim@char
1221 /// [pattern]: self::pattern
1222 ///
1223 /// # Examples
1224 ///
1225 /// Simple patterns:
1226 ///
1227 /// ```
1228 /// let s = "Löwe 老虎 Léopard Gepardi";
1229 ///
1230 /// assert_eq!(s.find('L'), Some(0));
1231 /// assert_eq!(s.find('é'), Some(14));
1232 /// assert_eq!(s.find("pard"), Some(17));
1233 /// ```
1234 ///
1235 /// More complex patterns using point-free style and closures:
1236 ///
1237 /// ```
1238 /// let s = "Löwe 老虎 Léopard";
1239 ///
1240 /// assert_eq!(s.find(char::is_whitespace), Some(5));
1241 /// assert_eq!(s.find(char::is_lowercase), Some(1));
1242 /// assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
1243 /// assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));
1244 /// ```
1245 ///
1246 /// Not finding the pattern:
1247 ///
1248 /// ```
1249 /// let s = "Löwe 老虎 Léopard";
1250 /// let x: &[_] = &['1', '2'];
1251 ///
1252 /// assert_eq!(s.find(x), None);
1253 /// ```
1254 #[stable(feature = "rust1", since = "1.0.0")]
1255 #[inline]
1256 pub fn find<'a, P: Pattern<'a>>(&'a self, pat: P) -> Option<usize> {
1257 pat.into_searcher(self).next_match().map(|(i, _)| i)
1258 }
1259
1260 /// Returns the byte index for the first character of the last match of the pattern in
1261 /// this string slice.
1262 ///
1263 /// Returns [`None`] if the pattern doesn't match.
1264 ///
1265 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1266 /// function or closure that determines if a character matches.
1267 ///
1268 /// [`char`]: prim@char
1269 /// [pattern]: self::pattern
1270 ///
1271 /// # Examples
1272 ///
1273 /// Simple patterns:
1274 ///
1275 /// ```
1276 /// let s = "Löwe 老虎 Léopard Gepardi";
1277 ///
1278 /// assert_eq!(s.rfind('L'), Some(13));
1279 /// assert_eq!(s.rfind('é'), Some(14));
1280 /// assert_eq!(s.rfind("pard"), Some(24));
1281 /// ```
1282 ///
1283 /// More complex patterns with closures:
1284 ///
1285 /// ```
1286 /// let s = "Löwe 老虎 Léopard";
1287 ///
1288 /// assert_eq!(s.rfind(char::is_whitespace), Some(12));
1289 /// assert_eq!(s.rfind(char::is_lowercase), Some(20));
1290 /// ```
1291 ///
1292 /// Not finding the pattern:
1293 ///
1294 /// ```
1295 /// let s = "Löwe 老虎 Léopard";
1296 /// let x: &[_] = &['1', '2'];
1297 ///
1298 /// assert_eq!(s.rfind(x), None);
1299 /// ```
1300 #[stable(feature = "rust1", since = "1.0.0")]
1301 #[inline]
1302 pub fn rfind<'a, P>(&'a self, pat: P) -> Option<usize>
1303 where
1304 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1305 {
1306 pat.into_searcher(self).next_match_back().map(|(i, _)| i)
1307 }
1308
1309 /// An iterator over substrings of this string slice, separated by
1310 /// characters matched by a pattern.
1311 ///
1312 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1313 /// function or closure that determines if a character matches.
1314 ///
1315 /// [`char`]: prim@char
1316 /// [pattern]: self::pattern
1317 ///
1318 /// # Iterator behavior
1319 ///
1320 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1321 /// allows a reverse search and forward/reverse search yields the same
1322 /// elements. This is true for, e.g., [`char`], but not for `&str`.
1323 ///
1324 /// If the pattern allows a reverse search but its results might differ
1325 /// from a forward search, the [`rsplit`] method can be used.
1326 ///
1327 /// [`rsplit`]: str::rsplit
1328 ///
1329 /// # Examples
1330 ///
1331 /// Simple patterns:
1332 ///
1333 /// ```
1334 /// let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
1335 /// assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);
1336 ///
1337 /// let v: Vec<&str> = "".split('X').collect();
1338 /// assert_eq!(v, [""]);
1339 ///
1340 /// let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
1341 /// assert_eq!(v, ["lion", "", "tiger", "leopard"]);
1342 ///
1343 /// let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
1344 /// assert_eq!(v, ["lion", "tiger", "leopard"]);
1345 ///
1346 /// let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
1347 /// assert_eq!(v, ["abc", "def", "ghi"]);
1348 ///
1349 /// let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
1350 /// assert_eq!(v, ["lion", "tiger", "leopard"]);
1351 /// ```
1352 ///
1353 /// If the pattern is a slice of chars, split on each occurrence of any of the characters:
1354 ///
1355 /// ```
1356 /// let v: Vec<&str> = "2020-11-03 23:59".split(&['-', ' ', ':', '@'][..]).collect();
1357 /// assert_eq!(v, ["2020", "11", "03", "23", "59"]);
1358 /// ```
1359 ///
1360 /// A more complex pattern, using a closure:
1361 ///
1362 /// ```
1363 /// let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
1364 /// assert_eq!(v, ["abc", "def", "ghi"]);
1365 /// ```
1366 ///
1367 /// If a string contains multiple contiguous separators, you will end up
1368 /// with empty strings in the output:
1369 ///
1370 /// ```
1371 /// let x = "||||a||b|c".to_string();
1372 /// let d: Vec<_> = x.split('|').collect();
1373 ///
1374 /// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
1375 /// ```
1376 ///
1377 /// Contiguous separators are separated by the empty string.
1378 ///
1379 /// ```
1380 /// let x = "(///)".to_string();
1381 /// let d: Vec<_> = x.split('/').collect();
1382 ///
1383 /// assert_eq!(d, &["(", "", "", ")"]);
1384 /// ```
1385 ///
1386 /// Separators at the start or end of a string are neighbored
1387 /// by empty strings.
1388 ///
1389 /// ```
1390 /// let d: Vec<_> = "010".split("0").collect();
1391 /// assert_eq!(d, &["", "1", ""]);
1392 /// ```
1393 ///
1394 /// When the empty string is used as a separator, it separates
1395 /// every character in the string, along with the beginning
1396 /// and end of the string.
1397 ///
1398 /// ```
1399 /// let f: Vec<_> = "rust".split("").collect();
1400 /// assert_eq!(f, &["", "r", "u", "s", "t", ""]);
1401 /// ```
1402 ///
1403 /// Contiguous separators can lead to possibly surprising behavior
1404 /// when whitespace is used as the separator. This code is correct:
1405 ///
1406 /// ```
1407 /// let x = " a b c".to_string();
1408 /// let d: Vec<_> = x.split(' ').collect();
1409 ///
1410 /// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
1411 /// ```
1412 ///
1413 /// It does _not_ give you:
1414 ///
1415 /// ```,ignore
1416 /// assert_eq!(d, &["a", "b", "c"]);
1417 /// ```
1418 ///
1419 /// Use [`split_whitespace`] for this behavior.
1420 ///
1421 /// [`split_whitespace`]: str::split_whitespace
1422 #[stable(feature = "rust1", since = "1.0.0")]
1423 #[inline]
1424 pub fn split<'a, P: Pattern<'a>>(&'a self, pat: P) -> Split<'a, P> {
1425 Split(SplitInternal {
1426 start: 0,
1427 end: self.len(),
1428 matcher: pat.into_searcher(self),
1429 allow_trailing_empty: true,
1430 finished: false,
1431 })
1432 }
1433
1434 /// An iterator over substrings of this string slice, separated by
1435 /// characters matched by a pattern. Differs from the iterator produced by
1436 /// `split` in that `split_inclusive` leaves the matched part as the
1437 /// terminator of the substring.
1438 ///
1439 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1440 /// function or closure that determines if a character matches.
1441 ///
1442 /// [`char`]: prim@char
1443 /// [pattern]: self::pattern
1444 ///
1445 /// # Examples
1446 ///
1447 /// ```
1448 /// let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb."
1449 /// .split_inclusive('\n').collect();
1450 /// assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb."]);
1451 /// ```
1452 ///
1453 /// If the last element of the string is matched,
1454 /// that element will be considered the terminator of the preceding substring.
1455 /// That substring will be the last item returned by the iterator.
1456 ///
1457 /// ```
1458 /// let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb.\n"
1459 /// .split_inclusive('\n').collect();
1460 /// assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb.\n"]);
1461 /// ```
1462 #[stable(feature = "split_inclusive", since = "1.51.0")]
1463 #[inline]
1464 pub fn split_inclusive<'a, P: Pattern<'a>>(&'a self, pat: P) -> SplitInclusive<'a, P> {
1465 SplitInclusive(SplitInternal {
1466 start: 0,
1467 end: self.len(),
1468 matcher: pat.into_searcher(self),
1469 allow_trailing_empty: false,
1470 finished: false,
1471 })
1472 }
1473
1474 /// An iterator over substrings of the given string slice, separated by
1475 /// characters matched by a pattern and yielded in reverse order.
1476 ///
1477 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1478 /// function or closure that determines if a character matches.
1479 ///
1480 /// [`char`]: prim@char
1481 /// [pattern]: self::pattern
1482 ///
1483 /// # Iterator behavior
1484 ///
1485 /// The returned iterator requires that the pattern supports a reverse
1486 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1487 /// search yields the same elements.
1488 ///
1489 /// For iterating from the front, the [`split`] method can be used.
1490 ///
1491 /// [`split`]: str::split
1492 ///
1493 /// # Examples
1494 ///
1495 /// Simple patterns:
1496 ///
1497 /// ```
1498 /// let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
1499 /// assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);
1500 ///
1501 /// let v: Vec<&str> = "".rsplit('X').collect();
1502 /// assert_eq!(v, [""]);
1503 ///
1504 /// let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
1505 /// assert_eq!(v, ["leopard", "tiger", "", "lion"]);
1506 ///
1507 /// let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
1508 /// assert_eq!(v, ["leopard", "tiger", "lion"]);
1509 /// ```
1510 ///
1511 /// A more complex pattern, using a closure:
1512 ///
1513 /// ```
1514 /// let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
1515 /// assert_eq!(v, ["ghi", "def", "abc"]);
1516 /// ```
1517 #[stable(feature = "rust1", since = "1.0.0")]
1518 #[inline]
1519 pub fn rsplit<'a, P>(&'a self, pat: P) -> RSplit<'a, P>
1520 where
1521 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1522 {
1523 RSplit(self.split(pat).0)
1524 }
1525
1526 /// An iterator over substrings of the given string slice, separated by
1527 /// characters matched by a pattern.
1528 ///
1529 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1530 /// function or closure that determines if a character matches.
1531 ///
1532 /// [`char`]: prim@char
1533 /// [pattern]: self::pattern
1534 ///
1535 /// Equivalent to [`split`], except that the trailing substring
1536 /// is skipped if empty.
1537 ///
1538 /// [`split`]: str::split
1539 ///
1540 /// This method can be used for string data that is _terminated_,
1541 /// rather than _separated_ by a pattern.
1542 ///
1543 /// # Iterator behavior
1544 ///
1545 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1546 /// allows a reverse search and forward/reverse search yields the same
1547 /// elements. This is true for, e.g., [`char`], but not for `&str`.
1548 ///
1549 /// If the pattern allows a reverse search but its results might differ
1550 /// from a forward search, the [`rsplit_terminator`] method can be used.
1551 ///
1552 /// [`rsplit_terminator`]: str::rsplit_terminator
1553 ///
1554 /// # Examples
1555 ///
1556 /// ```
1557 /// let v: Vec<&str> = "A.B.".split_terminator('.').collect();
1558 /// assert_eq!(v, ["A", "B"]);
1559 ///
1560 /// let v: Vec<&str> = "A..B..".split_terminator(".").collect();
1561 /// assert_eq!(v, ["A", "", "B", ""]);
1562 ///
1563 /// let v: Vec<&str> = "A.B:C.D".split_terminator(&['.', ':'][..]).collect();
1564 /// assert_eq!(v, ["A", "B", "C", "D"]);
1565 /// ```
1566 #[stable(feature = "rust1", since = "1.0.0")]
1567 #[inline]
1568 pub fn split_terminator<'a, P: Pattern<'a>>(&'a self, pat: P) -> SplitTerminator<'a, P> {
1569 SplitTerminator(SplitInternal { allow_trailing_empty: false, ..self.split(pat).0 })
1570 }
1571
1572 /// An iterator over substrings of `self`, separated by characters
1573 /// matched by a pattern and yielded in reverse order.
1574 ///
1575 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1576 /// function or closure that determines if a character matches.
1577 ///
1578 /// [`char`]: prim@char
1579 /// [pattern]: self::pattern
1580 ///
1581 /// Equivalent to [`split`], except that the trailing substring is
1582 /// skipped if empty.
1583 ///
1584 /// [`split`]: str::split
1585 ///
1586 /// This method can be used for string data that is _terminated_,
1587 /// rather than _separated_ by a pattern.
1588 ///
1589 /// # Iterator behavior
1590 ///
1591 /// The returned iterator requires that the pattern supports a
1592 /// reverse search, and it will be double ended if a forward/reverse
1593 /// search yields the same elements.
1594 ///
1595 /// For iterating from the front, the [`split_terminator`] method can be
1596 /// used.
1597 ///
1598 /// [`split_terminator`]: str::split_terminator
1599 ///
1600 /// # Examples
1601 ///
1602 /// ```
1603 /// let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
1604 /// assert_eq!(v, ["B", "A"]);
1605 ///
1606 /// let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
1607 /// assert_eq!(v, ["", "B", "", "A"]);
1608 ///
1609 /// let v: Vec<&str> = "A.B:C.D".rsplit_terminator(&['.', ':'][..]).collect();
1610 /// assert_eq!(v, ["D", "C", "B", "A"]);
1611 /// ```
1612 #[stable(feature = "rust1", since = "1.0.0")]
1613 #[inline]
1614 pub fn rsplit_terminator<'a, P>(&'a self, pat: P) -> RSplitTerminator<'a, P>
1615 where
1616 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1617 {
1618 RSplitTerminator(self.split_terminator(pat).0)
1619 }
1620
1621 /// An iterator over substrings of the given string slice, separated by a
1622 /// pattern, restricted to returning at most `n` items.
1623 ///
1624 /// If `n` substrings are returned, the last substring (the `n`th substring)
1625 /// will contain the remainder of the string.
1626 ///
1627 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1628 /// function or closure that determines if a character matches.
1629 ///
1630 /// [`char`]: prim@char
1631 /// [pattern]: self::pattern
1632 ///
1633 /// # Iterator behavior
1634 ///
1635 /// The returned iterator will not be double ended, because it is
1636 /// not efficient to support.
1637 ///
1638 /// If the pattern allows a reverse search, the [`rsplitn`] method can be
1639 /// used.
1640 ///
1641 /// [`rsplitn`]: str::rsplitn
1642 ///
1643 /// # Examples
1644 ///
1645 /// Simple patterns:
1646 ///
1647 /// ```
1648 /// let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
1649 /// assert_eq!(v, ["Mary", "had", "a little lambda"]);
1650 ///
1651 /// let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
1652 /// assert_eq!(v, ["lion", "", "tigerXleopard"]);
1653 ///
1654 /// let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
1655 /// assert_eq!(v, ["abcXdef"]);
1656 ///
1657 /// let v: Vec<&str> = "".splitn(1, 'X').collect();
1658 /// assert_eq!(v, [""]);
1659 /// ```
1660 ///
1661 /// A more complex pattern, using a closure:
1662 ///
1663 /// ```
1664 /// let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
1665 /// assert_eq!(v, ["abc", "defXghi"]);
1666 /// ```
1667 #[stable(feature = "rust1", since = "1.0.0")]
1668 #[inline]
1669 pub fn splitn<'a, P: Pattern<'a>>(&'a self, n: usize, pat: P) -> SplitN<'a, P> {
1670 SplitN(SplitNInternal { iter: self.split(pat).0, count: n })
1671 }
1672
1673 /// An iterator over substrings of this string slice, separated by a
1674 /// pattern, starting from the end of the string, restricted to returning
1675 /// at most `n` items.
1676 ///
1677 /// If `n` substrings are returned, the last substring (the `n`th substring)
1678 /// will contain the remainder of the string.
1679 ///
1680 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1681 /// function or closure that determines if a character matches.
1682 ///
1683 /// [`char`]: prim@char
1684 /// [pattern]: self::pattern
1685 ///
1686 /// # Iterator behavior
1687 ///
1688 /// The returned iterator will not be double ended, because it is not
1689 /// efficient to support.
1690 ///
1691 /// For splitting from the front, the [`splitn`] method can be used.
1692 ///
1693 /// [`splitn`]: str::splitn
1694 ///
1695 /// # Examples
1696 ///
1697 /// Simple patterns:
1698 ///
1699 /// ```
1700 /// let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
1701 /// assert_eq!(v, ["lamb", "little", "Mary had a"]);
1702 ///
1703 /// let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
1704 /// assert_eq!(v, ["leopard", "tiger", "lionX"]);
1705 ///
1706 /// let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
1707 /// assert_eq!(v, ["leopard", "lion::tiger"]);
1708 /// ```
1709 ///
1710 /// A more complex pattern, using a closure:
1711 ///
1712 /// ```
1713 /// let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
1714 /// assert_eq!(v, ["ghi", "abc1def"]);
1715 /// ```
1716 #[stable(feature = "rust1", since = "1.0.0")]
1717 #[inline]
1718 pub fn rsplitn<'a, P>(&'a self, n: usize, pat: P) -> RSplitN<'a, P>
1719 where
1720 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1721 {
1722 RSplitN(self.splitn(n, pat).0)
1723 }
1724
1725 /// Splits the string on the first occurrence of the specified delimiter and
1726 /// returns prefix before delimiter and suffix after delimiter.
1727 ///
1728 /// # Examples
1729 ///
1730 /// ```
1731 /// assert_eq!("cfg".split_once('='), None);
1732 /// assert_eq!("cfg=".split_once('='), Some(("cfg", "")));
1733 /// assert_eq!("cfg=foo".split_once('='), Some(("cfg", "foo")));
1734 /// assert_eq!("cfg=foo=bar".split_once('='), Some(("cfg", "foo=bar")));
1735 /// ```
1736 #[stable(feature = "str_split_once", since = "1.52.0")]
1737 #[inline]
1738 pub fn split_once<'a, P: Pattern<'a>>(&'a self, delimiter: P) -> Option<(&'a str, &'a str)> {
1739 let (start, end) = delimiter.into_searcher(self).next_match()?;
1740 // SAFETY: `Searcher` is known to return valid indices.
1741 unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
1742 }
1743
1744 /// Splits the string on the last occurrence of the specified delimiter and
1745 /// returns prefix before delimiter and suffix after delimiter.
1746 ///
1747 /// # Examples
1748 ///
1749 /// ```
1750 /// assert_eq!("cfg".rsplit_once('='), None);
1751 /// assert_eq!("cfg=foo".rsplit_once('='), Some(("cfg", "foo")));
1752 /// assert_eq!("cfg=foo=bar".rsplit_once('='), Some(("cfg=foo", "bar")));
1753 /// ```
1754 #[stable(feature = "str_split_once", since = "1.52.0")]
1755 #[inline]
1756 pub fn rsplit_once<'a, P>(&'a self, delimiter: P) -> Option<(&'a str, &'a str)>
1757 where
1758 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1759 {
1760 let (start, end) = delimiter.into_searcher(self).next_match_back()?;
1761 // SAFETY: `Searcher` is known to return valid indices.
1762 unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
1763 }
1764
1765 /// An iterator over the disjoint matches of a pattern within the given string
1766 /// slice.
1767 ///
1768 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1769 /// function or closure that determines if a character matches.
1770 ///
1771 /// [`char`]: prim@char
1772 /// [pattern]: self::pattern
1773 ///
1774 /// # Iterator behavior
1775 ///
1776 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1777 /// allows a reverse search and forward/reverse search yields the same
1778 /// elements. This is true for, e.g., [`char`], but not for `&str`.
1779 ///
1780 /// If the pattern allows a reverse search but its results might differ
1781 /// from a forward search, the [`rmatches`] method can be used.
1782 ///
1783 /// [`rmatches`]: str::rmatches
1784 ///
1785 /// # Examples
1786 ///
1787 /// ```
1788 /// let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
1789 /// assert_eq!(v, ["abc", "abc", "abc"]);
1790 ///
1791 /// let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
1792 /// assert_eq!(v, ["1", "2", "3"]);
1793 /// ```
1794 #[stable(feature = "str_matches", since = "1.2.0")]
1795 #[inline]
1796 pub fn matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> Matches<'a, P> {
1797 Matches(MatchesInternal(pat.into_searcher(self)))
1798 }
1799
1800 /// An iterator over the disjoint matches of a pattern within this string slice,
1801 /// yielded in reverse order.
1802 ///
1803 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1804 /// function or closure that determines if a character matches.
1805 ///
1806 /// [`char`]: prim@char
1807 /// [pattern]: self::pattern
1808 ///
1809 /// # Iterator behavior
1810 ///
1811 /// The returned iterator requires that the pattern supports a reverse
1812 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1813 /// search yields the same elements.
1814 ///
1815 /// For iterating from the front, the [`matches`] method can be used.
1816 ///
1817 /// [`matches`]: str::matches
1818 ///
1819 /// # Examples
1820 ///
1821 /// ```
1822 /// let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
1823 /// assert_eq!(v, ["abc", "abc", "abc"]);
1824 ///
1825 /// let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
1826 /// assert_eq!(v, ["3", "2", "1"]);
1827 /// ```
1828 #[stable(feature = "str_matches", since = "1.2.0")]
1829 #[inline]
1830 pub fn rmatches<'a, P>(&'a self, pat: P) -> RMatches<'a, P>
1831 where
1832 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1833 {
1834 RMatches(self.matches(pat).0)
1835 }
1836
1837 /// An iterator over the disjoint matches of a pattern within this string
1838 /// slice as well as the index that the match starts at.
1839 ///
1840 /// For matches of `pat` within `self` that overlap, only the indices
1841 /// corresponding to the first match are returned.
1842 ///
1843 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1844 /// function or closure that determines if a character matches.
1845 ///
1846 /// [`char`]: prim@char
1847 /// [pattern]: self::pattern
1848 ///
1849 /// # Iterator behavior
1850 ///
1851 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1852 /// allows a reverse search and forward/reverse search yields the same
1853 /// elements. This is true for, e.g., [`char`], but not for `&str`.
1854 ///
1855 /// If the pattern allows a reverse search but its results might differ
1856 /// from a forward search, the [`rmatch_indices`] method can be used.
1857 ///
1858 /// [`rmatch_indices`]: str::rmatch_indices
1859 ///
1860 /// # Examples
1861 ///
1862 /// ```
1863 /// let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
1864 /// assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);
1865 ///
1866 /// let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
1867 /// assert_eq!(v, [(1, "abc"), (4, "abc")]);
1868 ///
1869 /// let v: Vec<_> = "ababa".match_indices("aba").collect();
1870 /// assert_eq!(v, [(0, "aba")]); // only the first `aba`
1871 /// ```
1872 #[stable(feature = "str_match_indices", since = "1.5.0")]
1873 #[inline]
1874 pub fn match_indices<'a, P: Pattern<'a>>(&'a self, pat: P) -> MatchIndices<'a, P> {
1875 MatchIndices(MatchIndicesInternal(pat.into_searcher(self)))
1876 }
1877
1878 /// An iterator over the disjoint matches of a pattern within `self`,
1879 /// yielded in reverse order along with the index of the match.
1880 ///
1881 /// For matches of `pat` within `self` that overlap, only the indices
1882 /// corresponding to the last match are returned.
1883 ///
1884 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1885 /// function or closure that determines if a character matches.
1886 ///
1887 /// [`char`]: prim@char
1888 /// [pattern]: self::pattern
1889 ///
1890 /// # Iterator behavior
1891 ///
1892 /// The returned iterator requires that the pattern supports a reverse
1893 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1894 /// search yields the same elements.
1895 ///
1896 /// For iterating from the front, the [`match_indices`] method can be used.
1897 ///
1898 /// [`match_indices`]: str::match_indices
1899 ///
1900 /// # Examples
1901 ///
1902 /// ```
1903 /// let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
1904 /// assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);
1905 ///
1906 /// let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
1907 /// assert_eq!(v, [(4, "abc"), (1, "abc")]);
1908 ///
1909 /// let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
1910 /// assert_eq!(v, [(2, "aba")]); // only the last `aba`
1911 /// ```
1912 #[stable(feature = "str_match_indices", since = "1.5.0")]
1913 #[inline]
1914 pub fn rmatch_indices<'a, P>(&'a self, pat: P) -> RMatchIndices<'a, P>
1915 where
1916 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
1917 {
1918 RMatchIndices(self.match_indices(pat).0)
1919 }
1920
1921 /// Returns a string slice with leading and trailing whitespace removed.
1922 ///
1923 /// 'Whitespace' is defined according to the terms of the Unicode Derived
1924 /// Core Property `White_Space`, which includes newlines.
1925 ///
1926 /// # Examples
1927 ///
1928 /// ```
1929 /// let s = "\n Hello\tworld\t\n";
1930 ///
1931 /// assert_eq!("Hello\tworld", s.trim());
1932 /// ```
1933 #[inline]
1934 #[must_use = "this returns the trimmed string as a slice, \
1935 without modifying the original"]
1936 #[stable(feature = "rust1", since = "1.0.0")]
1937 #[cfg_attr(not(test), rustc_diagnostic_item = "str_trim")]
1938 pub fn trim(&self) -> &str {
1939 self.trim_matches(|c: char| c.is_whitespace())
1940 }
1941
1942 /// Returns a string slice with leading whitespace removed.
1943 ///
1944 /// 'Whitespace' is defined according to the terms of the Unicode Derived
1945 /// Core Property `White_Space`, which includes newlines.
1946 ///
1947 /// # Text directionality
1948 ///
1949 /// A string is a sequence of bytes. `start` in this context means the first
1950 /// position of that byte string; for a left-to-right language like English or
1951 /// Russian, this will be left side, and for right-to-left languages like
1952 /// Arabic or Hebrew, this will be the right side.
1953 ///
1954 /// # Examples
1955 ///
1956 /// Basic usage:
1957 ///
1958 /// ```
1959 /// let s = "\n Hello\tworld\t\n";
1960 /// assert_eq!("Hello\tworld\t\n", s.trim_start());
1961 /// ```
1962 ///
1963 /// Directionality:
1964 ///
1965 /// ```
1966 /// let s = " English ";
1967 /// assert!(Some('E') == s.trim_start().chars().next());
1968 ///
1969 /// let s = " עברית ";
1970 /// assert!(Some('ע') == s.trim_start().chars().next());
1971 /// ```
1972 #[inline]
1973 #[must_use = "this returns the trimmed string as a new slice, \
1974 without modifying the original"]
1975 #[stable(feature = "trim_direction", since = "1.30.0")]
1976 #[cfg_attr(not(test), rustc_diagnostic_item = "str_trim_start")]
1977 pub fn trim_start(&self) -> &str {
1978 self.trim_start_matches(|c: char| c.is_whitespace())
1979 }
1980
1981 /// Returns a string slice with trailing whitespace removed.
1982 ///
1983 /// 'Whitespace' is defined according to the terms of the Unicode Derived
1984 /// Core Property `White_Space`, which includes newlines.
1985 ///
1986 /// # Text directionality
1987 ///
1988 /// A string is a sequence of bytes. `end` in this context means the last
1989 /// position of that byte string; for a left-to-right language like English or
1990 /// Russian, this will be right side, and for right-to-left languages like
1991 /// Arabic or Hebrew, this will be the left side.
1992 ///
1993 /// # Examples
1994 ///
1995 /// Basic usage:
1996 ///
1997 /// ```
1998 /// let s = "\n Hello\tworld\t\n";
1999 /// assert_eq!("\n Hello\tworld", s.trim_end());
2000 /// ```
2001 ///
2002 /// Directionality:
2003 ///
2004 /// ```
2005 /// let s = " English ";
2006 /// assert!(Some('h') == s.trim_end().chars().rev().next());
2007 ///
2008 /// let s = " עברית ";
2009 /// assert!(Some('ת') == s.trim_end().chars().rev().next());
2010 /// ```
2011 #[inline]
2012 #[must_use = "this returns the trimmed string as a new slice, \
2013 without modifying the original"]
2014 #[stable(feature = "trim_direction", since = "1.30.0")]
2015 #[cfg_attr(not(test), rustc_diagnostic_item = "str_trim_end")]
2016 pub fn trim_end(&self) -> &str {
2017 self.trim_end_matches(|c: char| c.is_whitespace())
2018 }
2019
2020 /// Returns a string slice with leading whitespace removed.
2021 ///
2022 /// 'Whitespace' is defined according to the terms of the Unicode Derived
2023 /// Core Property `White_Space`.
2024 ///
2025 /// # Text directionality
2026 ///
2027 /// A string is a sequence of bytes. 'Left' in this context means the first
2028 /// position of that byte string; for a language like Arabic or Hebrew
2029 /// which are 'right to left' rather than 'left to right', this will be
2030 /// the _right_ side, not the left.
2031 ///
2032 /// # Examples
2033 ///
2034 /// Basic usage:
2035 ///
2036 /// ```
2037 /// let s = " Hello\tworld\t";
2038 ///
2039 /// assert_eq!("Hello\tworld\t", s.trim_left());
2040 /// ```
2041 ///
2042 /// Directionality:
2043 ///
2044 /// ```
2045 /// let s = " English";
2046 /// assert!(Some('E') == s.trim_left().chars().next());
2047 ///
2048 /// let s = " עברית";
2049 /// assert!(Some('ע') == s.trim_left().chars().next());
2050 /// ```
2051 #[must_use = "this returns the trimmed string as a new slice, \
2052 without modifying the original"]
2053 #[inline]
2054 #[stable(feature = "rust1", since = "1.0.0")]
2055 #[deprecated(since = "1.33.0", note = "superseded by `trim_start`", suggestion = "trim_start")]
2056 pub fn trim_left(&self) -> &str {
2057 self.trim_start()
2058 }
2059
2060 /// Returns a string slice with trailing whitespace removed.
2061 ///
2062 /// 'Whitespace' is defined according to the terms of the Unicode Derived
2063 /// Core Property `White_Space`.
2064 ///
2065 /// # Text directionality
2066 ///
2067 /// A string is a sequence of bytes. 'Right' in this context means the last
2068 /// position of that byte string; for a language like Arabic or Hebrew
2069 /// which are 'right to left' rather than 'left to right', this will be
2070 /// the _left_ side, not the right.
2071 ///
2072 /// # Examples
2073 ///
2074 /// Basic usage:
2075 ///
2076 /// ```
2077 /// let s = " Hello\tworld\t";
2078 ///
2079 /// assert_eq!(" Hello\tworld", s.trim_right());
2080 /// ```
2081 ///
2082 /// Directionality:
2083 ///
2084 /// ```
2085 /// let s = "English ";
2086 /// assert!(Some('h') == s.trim_right().chars().rev().next());
2087 ///
2088 /// let s = "עברית ";
2089 /// assert!(Some('ת') == s.trim_right().chars().rev().next());
2090 /// ```
2091 #[must_use = "this returns the trimmed string as a new slice, \
2092 without modifying the original"]
2093 #[inline]
2094 #[stable(feature = "rust1", since = "1.0.0")]
2095 #[deprecated(since = "1.33.0", note = "superseded by `trim_end`", suggestion = "trim_end")]
2096 pub fn trim_right(&self) -> &str {
2097 self.trim_end()
2098 }
2099
2100 /// Returns a string slice with all prefixes and suffixes that match a
2101 /// pattern repeatedly removed.
2102 ///
2103 /// The [pattern] can be a [`char`], a slice of [`char`]s, or a function
2104 /// or closure that determines if a character matches.
2105 ///
2106 /// [`char`]: prim@char
2107 /// [pattern]: self::pattern
2108 ///
2109 /// # Examples
2110 ///
2111 /// Simple patterns:
2112 ///
2113 /// ```
2114 /// assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
2115 /// assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");
2116 ///
2117 /// let x: &[_] = &['1', '2'];
2118 /// assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");
2119 /// ```
2120 ///
2121 /// A more complex pattern, using a closure:
2122 ///
2123 /// ```
2124 /// assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");
2125 /// ```
2126 #[must_use = "this returns the trimmed string as a new slice, \
2127 without modifying the original"]
2128 #[stable(feature = "rust1", since = "1.0.0")]
2129 pub fn trim_matches<'a, P>(&'a self, pat: P) -> &'a str
2130 where
2131 P: Pattern<'a, Searcher: DoubleEndedSearcher<'a>>,
2132 {
2133 let mut i = 0;
2134 let mut j = 0;
2135 let mut matcher = pat.into_searcher(self);
2136 if let Some((a, b)) = matcher.next_reject() {
2137 i = a;
2138 j = b; // Remember earliest known match, correct it below if
2139 // last match is different
2140 }
2141 if let Some((_, b)) = matcher.next_reject_back() {
2142 j = b;
2143 }
2144 // SAFETY: `Searcher` is known to return valid indices.
2145 unsafe { self.get_unchecked(i..j) }
2146 }
2147
2148 /// Returns a string slice with all prefixes that match a pattern
2149 /// repeatedly removed.
2150 ///
2151 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2152 /// function or closure that determines if a character matches.
2153 ///
2154 /// [`char`]: prim@char
2155 /// [pattern]: self::pattern
2156 ///
2157 /// # Text directionality
2158 ///
2159 /// A string is a sequence of bytes. `start` in this context means the first
2160 /// position of that byte string; for a left-to-right language like English or
2161 /// Russian, this will be left side, and for right-to-left languages like
2162 /// Arabic or Hebrew, this will be the right side.
2163 ///
2164 /// # Examples
2165 ///
2166 /// ```
2167 /// assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
2168 /// assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");
2169 ///
2170 /// let x: &[_] = &['1', '2'];
2171 /// assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");
2172 /// ```
2173 #[must_use = "this returns the trimmed string as a new slice, \
2174 without modifying the original"]
2175 #[stable(feature = "trim_direction", since = "1.30.0")]
2176 pub fn trim_start_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str {
2177 let mut i = self.len();
2178 let mut matcher = pat.into_searcher(self);
2179 if let Some((a, _)) = matcher.next_reject() {
2180 i = a;
2181 }
2182 // SAFETY: `Searcher` is known to return valid indices.
2183 unsafe { self.get_unchecked(i..self.len()) }
2184 }
2185
2186 /// Returns a string slice with the prefix removed.
2187 ///
2188 /// If the string starts with the pattern `prefix`, returns the substring after the prefix,
2189 /// wrapped in `Some`. Unlike `trim_start_matches`, this method removes the prefix exactly once.
2190 ///
2191 /// If the string does not start with `prefix`, returns `None`.
2192 ///
2193 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2194 /// function or closure that determines if a character matches.
2195 ///
2196 /// [`char`]: prim@char
2197 /// [pattern]: self::pattern
2198 ///
2199 /// # Examples
2200 ///
2201 /// ```
2202 /// assert_eq!("foo:bar".strip_prefix("foo:"), Some("bar"));
2203 /// assert_eq!("foo:bar".strip_prefix("bar"), None);
2204 /// assert_eq!("foofoo".strip_prefix("foo"), Some("foo"));
2205 /// ```
2206 #[must_use = "this returns the remaining substring as a new slice, \
2207 without modifying the original"]
2208 #[stable(feature = "str_strip", since = "1.45.0")]
2209 pub fn strip_prefix<'a, P: Pattern<'a>>(&'a self, prefix: P) -> Option<&'a str> {
2210 prefix.strip_prefix_of(self)
2211 }
2212
2213 /// Returns a string slice with the suffix removed.
2214 ///
2215 /// If the string ends with the pattern `suffix`, returns the substring before the suffix,
2216 /// wrapped in `Some`. Unlike `trim_end_matches`, this method removes the suffix exactly once.
2217 ///
2218 /// If the string does not end with `suffix`, returns `None`.
2219 ///
2220 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2221 /// function or closure that determines if a character matches.
2222 ///
2223 /// [`char`]: prim@char
2224 /// [pattern]: self::pattern
2225 ///
2226 /// # Examples
2227 ///
2228 /// ```
2229 /// assert_eq!("bar:foo".strip_suffix(":foo"), Some("bar"));
2230 /// assert_eq!("bar:foo".strip_suffix("bar"), None);
2231 /// assert_eq!("foofoo".strip_suffix("foo"), Some("foo"));
2232 /// ```
2233 #[must_use = "this returns the remaining substring as a new slice, \
2234 without modifying the original"]
2235 #[stable(feature = "str_strip", since = "1.45.0")]
2236 pub fn strip_suffix<'a, P>(&'a self, suffix: P) -> Option<&'a str>
2237 where
2238 P: Pattern<'a>,
2239 <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,
2240 {
2241 suffix.strip_suffix_of(self)
2242 }
2243
2244 /// Returns a string slice with all suffixes that match a pattern
2245 /// repeatedly removed.
2246 ///
2247 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2248 /// function or closure that determines if a character matches.
2249 ///
2250 /// [`char`]: prim@char
2251 /// [pattern]: self::pattern
2252 ///
2253 /// # Text directionality
2254 ///
2255 /// A string is a sequence of bytes. `end` in this context means the last
2256 /// position of that byte string; for a left-to-right language like English or
2257 /// Russian, this will be right side, and for right-to-left languages like
2258 /// Arabic or Hebrew, this will be the left side.
2259 ///
2260 /// # Examples
2261 ///
2262 /// Simple patterns:
2263 ///
2264 /// ```
2265 /// assert_eq!("11foo1bar11".trim_end_matches('1'), "11foo1bar");
2266 /// assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");
2267 ///
2268 /// let x: &[_] = &['1', '2'];
2269 /// assert_eq!("12foo1bar12".trim_end_matches(x), "12foo1bar");
2270 /// ```
2271 ///
2272 /// A more complex pattern, using a closure:
2273 ///
2274 /// ```
2275 /// assert_eq!("1fooX".trim_end_matches(|c| c == '1' || c == 'X'), "1foo");
2276 /// ```
2277 #[must_use = "this returns the trimmed string as a new slice, \
2278 without modifying the original"]
2279 #[stable(feature = "trim_direction", since = "1.30.0")]
2280 pub fn trim_end_matches<'a, P>(&'a self, pat: P) -> &'a str
2281 where
2282 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
2283 {
2284 let mut j = 0;
2285 let mut matcher = pat.into_searcher(self);
2286 if let Some((_, b)) = matcher.next_reject_back() {
2287 j = b;
2288 }
2289 // SAFETY: `Searcher` is known to return valid indices.
2290 unsafe { self.get_unchecked(0..j) }
2291 }
2292
2293 /// Returns a string slice with all prefixes that match a pattern
2294 /// repeatedly removed.
2295 ///
2296 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2297 /// function or closure that determines if a character matches.
2298 ///
2299 /// [`char`]: prim@char
2300 /// [pattern]: self::pattern
2301 ///
2302 /// # Text directionality
2303 ///
2304 /// A string is a sequence of bytes. 'Left' in this context means the first
2305 /// position of that byte string; for a language like Arabic or Hebrew
2306 /// which are 'right to left' rather than 'left to right', this will be
2307 /// the _right_ side, not the left.
2308 ///
2309 /// # Examples
2310 ///
2311 /// ```
2312 /// assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
2313 /// assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");
2314 ///
2315 /// let x: &[_] = &['1', '2'];
2316 /// assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");
2317 /// ```
2318 #[stable(feature = "rust1", since = "1.0.0")]
2319 #[deprecated(
2320 since = "1.33.0",
2321 note = "superseded by `trim_start_matches`",
2322 suggestion = "trim_start_matches"
2323 )]
2324 pub fn trim_left_matches<'a, P: Pattern<'a>>(&'a self, pat: P) -> &'a str {
2325 self.trim_start_matches(pat)
2326 }
2327
2328 /// Returns a string slice with all suffixes that match a pattern
2329 /// repeatedly removed.
2330 ///
2331 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2332 /// function or closure that determines if a character matches.
2333 ///
2334 /// [`char`]: prim@char
2335 /// [pattern]: self::pattern
2336 ///
2337 /// # Text directionality
2338 ///
2339 /// A string is a sequence of bytes. 'Right' in this context means the last
2340 /// position of that byte string; for a language like Arabic or Hebrew
2341 /// which are 'right to left' rather than 'left to right', this will be
2342 /// the _left_ side, not the right.
2343 ///
2344 /// # Examples
2345 ///
2346 /// Simple patterns:
2347 ///
2348 /// ```
2349 /// assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
2350 /// assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");
2351 ///
2352 /// let x: &[_] = &['1', '2'];
2353 /// assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");
2354 /// ```
2355 ///
2356 /// A more complex pattern, using a closure:
2357 ///
2358 /// ```
2359 /// assert_eq!("1fooX".trim_right_matches(|c| c == '1' || c == 'X'), "1foo");
2360 /// ```
2361 #[stable(feature = "rust1", since = "1.0.0")]
2362 #[deprecated(
2363 since = "1.33.0",
2364 note = "superseded by `trim_end_matches`",
2365 suggestion = "trim_end_matches"
2366 )]
2367 pub fn trim_right_matches<'a, P>(&'a self, pat: P) -> &'a str
2368 where
2369 P: Pattern<'a, Searcher: ReverseSearcher<'a>>,
2370 {
2371 self.trim_end_matches(pat)
2372 }
2373
2374 /// Parses this string slice into another type.
2375 ///
2376 /// Because `parse` is so general, it can cause problems with type
2377 /// inference. As such, `parse` is one of the few times you'll see
2378 /// the syntax affectionately known as the 'turbofish': `::<>`. This
2379 /// helps the inference algorithm understand specifically which type
2380 /// you're trying to parse into.
2381 ///
2382 /// `parse` can parse into any type that implements the [`FromStr`] trait.
2383
2384 ///
2385 /// # Errors
2386 ///
2387 /// Will return [`Err`] if it's not possible to parse this string slice into
2388 /// the desired type.
2389 ///
2390 /// [`Err`]: FromStr::Err
2391 ///
2392 /// # Examples
2393 ///
2394 /// Basic usage
2395 ///
2396 /// ```
2397 /// let four: u32 = "4".parse().unwrap();
2398 ///
2399 /// assert_eq!(4, four);
2400 /// ```
2401 ///
2402 /// Using the 'turbofish' instead of annotating `four`:
2403 ///
2404 /// ```
2405 /// let four = "4".parse::<u32>();
2406 ///
2407 /// assert_eq!(Ok(4), four);
2408 /// ```
2409 ///
2410 /// Failing to parse:
2411 ///
2412 /// ```
2413 /// let nope = "j".parse::<u32>();
2414 ///
2415 /// assert!(nope.is_err());
2416 /// ```
2417 #[inline]
2418 #[stable(feature = "rust1", since = "1.0.0")]
2419 pub fn parse<F: FromStr>(&self) -> Result<F, F::Err> {
2420 FromStr::from_str(self)
2421 }
2422
2423 /// Checks if all characters in this string are within the ASCII range.
2424 ///
2425 /// # Examples
2426 ///
2427 /// ```
2428 /// let ascii = "hello!\n";
2429 /// let non_ascii = "Grüße, Jürgen ❤";
2430 ///
2431 /// assert!(ascii.is_ascii());
2432 /// assert!(!non_ascii.is_ascii());
2433 /// ```
2434 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2435 #[rustc_const_stable(feature = "const_slice_is_ascii", since = "1.74.0")]
2436 #[must_use]
2437 #[inline]
2438 pub const fn is_ascii(&self) -> bool {
2439 // We can treat each byte as character here: all multibyte characters
2440 // start with a byte that is not in the ASCII range, so we will stop
2441 // there already.
2442 self.as_bytes().is_ascii()
2443 }
2444
2445 /// If this string slice [`is_ascii`](Self::is_ascii), returns it as a slice
2446 /// of [ASCII characters](`ascii::Char`), otherwise returns `None`.
2447 #[unstable(feature = "ascii_char", issue = "110998")]
2448 #[must_use]
2449 #[inline]
2450 pub const fn as_ascii(&self) -> Option<&[ascii::Char]> {
2451 // Like in `is_ascii`, we can work on the bytes directly.
2452 self.as_bytes().as_ascii()
2453 }
2454
2455 /// Checks that two strings are an ASCII case-insensitive match.
2456 ///
2457 /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
2458 /// but without allocating and copying temporaries.
2459 ///
2460 /// # Examples
2461 ///
2462 /// ```
2463 /// assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
2464 /// assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
2465 /// assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));
2466 /// ```
2467 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2468 #[must_use]
2469 #[inline]
2470 pub fn eq_ignore_ascii_case(&self, other: &str) -> bool {
2471 self.as_bytes().eq_ignore_ascii_case(other.as_bytes())
2472 }
2473
2474 /// Converts this string to its ASCII upper case equivalent in-place.
2475 ///
2476 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
2477 /// but non-ASCII letters are unchanged.
2478 ///
2479 /// To return a new uppercased value without modifying the existing one, use
2480 /// [`to_ascii_uppercase()`].
2481 ///
2482 /// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
2483 ///
2484 /// # Examples
2485 ///
2486 /// ```
2487 /// let mut s = String::from("Grüße, Jürgen ❤");
2488 ///
2489 /// s.make_ascii_uppercase();
2490 ///
2491 /// assert_eq!("GRüßE, JüRGEN ❤", s);
2492 /// ```
2493 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2494 #[inline]
2495 pub fn make_ascii_uppercase(&mut self) {
2496 // SAFETY: changing ASCII letters only does not invalidate UTF-8.
2497 let me = unsafe { self.as_bytes_mut() };
2498 me.make_ascii_uppercase()
2499 }
2500
2501 /// Converts this string to its ASCII lower case equivalent in-place.
2502 ///
2503 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
2504 /// but non-ASCII letters are unchanged.
2505 ///
2506 /// To return a new lowercased value without modifying the existing one, use
2507 /// [`to_ascii_lowercase()`].
2508 ///
2509 /// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
2510 ///
2511 /// # Examples
2512 ///
2513 /// ```
2514 /// let mut s = String::from("GRÜßE, JÜRGEN ❤");
2515 ///
2516 /// s.make_ascii_lowercase();
2517 ///
2518 /// assert_eq!("grÜße, jÜrgen ❤", s);
2519 /// ```
2520 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2521 #[inline]
2522 pub fn make_ascii_lowercase(&mut self) {
2523 // SAFETY: changing ASCII letters only does not invalidate UTF-8.
2524 let me = unsafe { self.as_bytes_mut() };
2525 me.make_ascii_lowercase()
2526 }
2527
2528 /// Returns a string slice with leading ASCII whitespace removed.
2529 ///
2530 /// 'Whitespace' refers to the definition used by
2531 /// [`u8::is_ascii_whitespace`].
2532 ///
2533 /// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
2534 ///
2535 /// # Examples
2536 ///
2537 /// ```
2538 /// #![feature(byte_slice_trim_ascii)]
2539 ///
2540 /// assert_eq!(" \t \u{3000}hello world\n".trim_ascii_start(), "\u{3000}hello world\n");
2541 /// assert_eq!(" ".trim_ascii_start(), "");
2542 /// assert_eq!("".trim_ascii_start(), "");
2543 /// ```
2544 #[unstable(feature = "byte_slice_trim_ascii", issue = "94035")]
2545 #[must_use = "this returns the trimmed string as a new slice, \
2546 without modifying the original"]
2547 #[inline]
2548 pub const fn trim_ascii_start(&self) -> &str {
2549 // SAFETY: Removing ASCII characters from a `&str` does not invalidate
2550 // UTF-8.
2551 unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii_start()) }
2552 }
2553
2554 /// Returns a string slice with trailing ASCII whitespace removed.
2555 ///
2556 /// 'Whitespace' refers to the definition used by
2557 /// [`u8::is_ascii_whitespace`].
2558 ///
2559 /// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
2560 ///
2561 /// # Examples
2562 ///
2563 /// ```
2564 /// #![feature(byte_slice_trim_ascii)]
2565 ///
2566 /// assert_eq!("\r hello world\u{3000}\n ".trim_ascii_end(), "\r hello world\u{3000}");
2567 /// assert_eq!(" ".trim_ascii_end(), "");
2568 /// assert_eq!("".trim_ascii_end(), "");
2569 /// ```
2570 #[unstable(feature = "byte_slice_trim_ascii", issue = "94035")]
2571 #[must_use = "this returns the trimmed string as a new slice, \
2572 without modifying the original"]
2573 #[inline]
2574 pub const fn trim_ascii_end(&self) -> &str {
2575 // SAFETY: Removing ASCII characters from a `&str` does not invalidate
2576 // UTF-8.
2577 unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii_end()) }
2578 }
2579
2580 /// Returns a string slice with leading and trailing ASCII whitespace
2581 /// removed.
2582 ///
2583 /// 'Whitespace' refers to the definition used by
2584 /// [`u8::is_ascii_whitespace`].
2585 ///
2586 /// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
2587 ///
2588 /// # Examples
2589 ///
2590 /// ```
2591 /// #![feature(byte_slice_trim_ascii)]
2592 ///
2593 /// assert_eq!("\r hello world\n ".trim_ascii(), "hello world");
2594 /// assert_eq!(" ".trim_ascii(), "");
2595 /// assert_eq!("".trim_ascii(), "");
2596 /// ```
2597 #[unstable(feature = "byte_slice_trim_ascii", issue = "94035")]
2598 #[must_use = "this returns the trimmed string as a new slice, \
2599 without modifying the original"]
2600 #[inline]
2601 pub const fn trim_ascii(&self) -> &str {
2602 // SAFETY: Removing ASCII characters from a `&str` does not invalidate
2603 // UTF-8.
2604 unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii()) }
2605 }
2606
2607 /// Return an iterator that escapes each char in `self` with [`char::escape_debug`].
2608 ///
2609 /// Note: only extended grapheme codepoints that begin the string will be
2610 /// escaped.
2611 ///
2612 /// # Examples
2613 ///
2614 /// As an iterator:
2615 ///
2616 /// ```
2617 /// for c in "❤\n!".escape_debug() {
2618 /// print!("{c}");
2619 /// }
2620 /// println!();
2621 /// ```
2622 ///
2623 /// Using `println!` directly:
2624 ///
2625 /// ```
2626 /// println!("{}", "❤\n!".escape_debug());
2627 /// ```
2628 ///
2629 ///
2630 /// Both are equivalent to:
2631 ///
2632 /// ```
2633 /// println!("❤\\n!");
2634 /// ```
2635 ///
2636 /// Using `to_string`:
2637 ///
2638 /// ```
2639 /// assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");
2640 /// ```
2641 #[must_use = "this returns the escaped string as an iterator, \
2642 without modifying the original"]
2643 #[stable(feature = "str_escape", since = "1.34.0")]
2644 pub fn escape_debug(&self) -> EscapeDebug<'_> {
2645 let mut chars = self.chars();
2646 EscapeDebug {
2647 inner: chars
2648 .next()
2649 .map(|first| first.escape_debug_ext(EscapeDebugExtArgs::ESCAPE_ALL))
2650 .into_iter()
2651 .flatten()
2652 .chain(chars.flat_map(CharEscapeDebugContinue)),
2653 }
2654 }
2655
2656 /// Return an iterator that escapes each char in `self` with [`char::escape_default`].
2657 ///
2658 /// # Examples
2659 ///
2660 /// As an iterator:
2661 ///
2662 /// ```
2663 /// for c in "❤\n!".escape_default() {
2664 /// print!("{c}");
2665 /// }
2666 /// println!();
2667 /// ```
2668 ///
2669 /// Using `println!` directly:
2670 ///
2671 /// ```
2672 /// println!("{}", "❤\n!".escape_default());
2673 /// ```
2674 ///
2675 ///
2676 /// Both are equivalent to:
2677 ///
2678 /// ```
2679 /// println!("\\u{{2764}}\\n!");
2680 /// ```
2681 ///
2682 /// Using `to_string`:
2683 ///
2684 /// ```
2685 /// assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");
2686 /// ```
2687 #[must_use = "this returns the escaped string as an iterator, \
2688 without modifying the original"]
2689 #[stable(feature = "str_escape", since = "1.34.0")]
2690 pub fn escape_default(&self) -> EscapeDefault<'_> {
2691 EscapeDefault { inner: self.chars().flat_map(CharEscapeDefault) }
2692 }
2693
2694 /// Return an iterator that escapes each char in `self` with [`char::escape_unicode`].
2695 ///
2696 /// # Examples
2697 ///
2698 /// As an iterator:
2699 ///
2700 /// ```
2701 /// for c in "❤\n!".escape_unicode() {
2702 /// print!("{c}");
2703 /// }
2704 /// println!();
2705 /// ```
2706 ///
2707 /// Using `println!` directly:
2708 ///
2709 /// ```
2710 /// println!("{}", "❤\n!".escape_unicode());
2711 /// ```
2712 ///
2713 ///
2714 /// Both are equivalent to:
2715 ///
2716 /// ```
2717 /// println!("\\u{{2764}}\\u{{a}}\\u{{21}}");
2718 /// ```
2719 ///
2720 /// Using `to_string`:
2721 ///
2722 /// ```
2723 /// assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");
2724 /// ```
2725 #[must_use = "this returns the escaped string as an iterator, \
2726 without modifying the original"]
2727 #[stable(feature = "str_escape", since = "1.34.0")]
2728 pub fn escape_unicode(&self) -> EscapeUnicode<'_> {
2729 EscapeUnicode { inner: self.chars().flat_map(CharEscapeUnicode) }
2730 }
2731}
2732
2733#[stable(feature = "rust1", since = "1.0.0")]
2734impl AsRef<[u8]> for str {
2735 #[inline]
2736 fn as_ref(&self) -> &[u8] {
2737 self.as_bytes()
2738 }
2739}
2740
2741#[stable(feature = "rust1", since = "1.0.0")]
2742impl Default for &str {
2743 /// Creates an empty str
2744 #[inline]
2745 fn default() -> Self {
2746 ""
2747 }
2748}
2749
2750#[stable(feature = "default_mut_str", since = "1.28.0")]
2751impl Default for &mut str {
2752 /// Creates an empty mutable str
2753 #[inline]
2754 fn default() -> Self {
2755 // SAFETY: The empty string is valid UTF-8.
2756 unsafe { from_utf8_unchecked_mut(&mut []) }
2757 }
2758}
2759
2760impl_fn_for_zst! {
2761 /// A nameable, cloneable fn type
2762 #[derive(Clone)]
2763 struct LinesMap impl<'a> Fn = |line: &'a str| -> &'a str {
2764 let Some(line) = line.strip_suffix('\n') else { return line };
2765 let Some(line) = line.strip_suffix('\r') else { return line };
2766 line
2767 };
2768
2769 #[derive(Clone)]
2770 struct CharEscapeDebugContinue impl Fn = |c: char| -> char::EscapeDebug {
2771 c.escape_debug_ext(EscapeDebugExtArgs {
2772 escape_grapheme_extended: false,
2773 escape_single_quote: true,
2774 escape_double_quote: true
2775 })
2776 };
2777
2778 #[derive(Clone)]
2779 struct CharEscapeUnicode impl Fn = |c: char| -> char::EscapeUnicode {
2780 c.escape_unicode()
2781 };
2782 #[derive(Clone)]
2783 struct CharEscapeDefault impl Fn = |c: char| -> char::EscapeDefault {
2784 c.escape_default()
2785 };
2786
2787 #[derive(Clone)]
2788 struct IsWhitespace impl Fn = |c: char| -> bool {
2789 c.is_whitespace()
2790 };
2791
2792 #[derive(Clone)]
2793 struct IsAsciiWhitespace impl Fn = |byte: &u8| -> bool {
2794 byte.is_ascii_whitespace()
2795 };
2796
2797 #[derive(Clone)]
2798 struct IsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b str| -> bool {
2799 !s.is_empty()
2800 };
2801
2802 #[derive(Clone)]
2803 struct BytesIsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b [u8]| -> bool {
2804 !s.is_empty()
2805 };
2806
2807 #[derive(Clone)]
2808 struct UnsafeBytesToStr impl<'a> Fn = |bytes: &'a [u8]| -> &'a str {
2809 // SAFETY: not safe
2810 unsafe { from_utf8_unchecked(bytes) }
2811 };
2812}
2813
2814// This is required to make `impl From<&str> for Box<dyn Error>` and `impl<E> From<E> for Box<dyn Error>` not overlap.
2815#[stable(feature = "rust1", since = "1.0.0")]
2816impl !crate::error::Error for &str {}
2817