1//! Trait implementations for `str`.
2
3use super::ParseBoolError;
4use crate::cmp::Ordering;
5use crate::intrinsics::unchecked_sub;
6use crate::slice::SliceIndex;
7use crate::ub_checks::assert_unsafe_precondition;
8use crate::{ops, ptr, range};
9
10/// Implements ordering of strings.
11///
12/// Strings are ordered [lexicographically](Ord#lexicographical-comparison) by their byte values. This orders Unicode code
13/// points based on their positions in the code charts. This is not necessarily the same as
14/// "alphabetical" order, which varies by language and locale. Sorting strings according to
15/// culturally-accepted standards requires locale-specific data that is outside the scope of
16/// the `str` type.
17#[stable(feature = "rust1", since = "1.0.0")]
18impl Ord for str {
19 #[inline]
20 fn cmp(&self, other: &str) -> Ordering {
21 self.as_bytes().cmp(other.as_bytes())
22 }
23}
24
25#[stable(feature = "rust1", since = "1.0.0")]
26impl PartialEq for str {
27 #[inline]
28 fn eq(&self, other: &str) -> bool {
29 self.as_bytes() == other.as_bytes()
30 }
31}
32
33#[stable(feature = "rust1", since = "1.0.0")]
34impl Eq for str {}
35
36/// Implements comparison operations on strings.
37///
38/// Strings are compared [lexicographically](Ord#lexicographical-comparison) by their byte values. This compares Unicode code
39/// points based on their positions in the code charts. This is not necessarily the same as
40/// "alphabetical" order, which varies by language and locale. Comparing strings according to
41/// culturally-accepted standards requires locale-specific data that is outside the scope of
42/// the `str` type.
43#[stable(feature = "rust1", since = "1.0.0")]
44impl PartialOrd for str {
45 #[inline]
46 fn partial_cmp(&self, other: &str) -> Option<Ordering> {
47 Some(self.cmp(other))
48 }
49}
50
51#[stable(feature = "rust1", since = "1.0.0")]
52impl<I> ops::Index<I> for str
53where
54 I: SliceIndex<str>,
55{
56 type Output = I::Output;
57
58 #[inline]
59 fn index(&self, index: I) -> &I::Output {
60 index.index(self)
61 }
62}
63
64#[stable(feature = "rust1", since = "1.0.0")]
65impl<I> ops::IndexMut<I> for str
66where
67 I: SliceIndex<str>,
68{
69 #[inline]
70 fn index_mut(&mut self, index: I) -> &mut I::Output {
71 index.index_mut(self)
72 }
73}
74
75#[inline(never)]
76#[cold]
77#[track_caller]
78const fn str_index_overflow_fail() -> ! {
79 panic!("attempted to index str up to maximum usize");
80}
81
82/// Implements substring slicing with syntax `&self[..]` or `&mut self[..]`.
83///
84/// Returns a slice of the whole string, i.e., returns `&self` or `&mut
85/// self`. Equivalent to `&self[0 .. len]` or `&mut self[0 .. len]`. Unlike
86/// other indexing operations, this can never panic.
87///
88/// This operation is *O*(1).
89///
90/// Prior to 1.20.0, these indexing operations were still supported by
91/// direct implementation of `Index` and `IndexMut`.
92///
93/// Equivalent to `&self[0 .. len]` or `&mut self[0 .. len]`.
94#[stable(feature = "str_checked_slicing", since = "1.20.0")]
95unsafe impl SliceIndex<str> for ops::RangeFull {
96 type Output = str;
97 #[inline]
98 fn get(self, slice: &str) -> Option<&Self::Output> {
99 Some(slice)
100 }
101 #[inline]
102 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
103 Some(slice)
104 }
105 #[inline]
106 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
107 slice
108 }
109 #[inline]
110 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
111 slice
112 }
113 #[inline]
114 fn index(self, slice: &str) -> &Self::Output {
115 slice
116 }
117 #[inline]
118 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
119 slice
120 }
121}
122
123/// Implements substring slicing with syntax `&self[begin .. end]` or `&mut
124/// self[begin .. end]`.
125///
126/// Returns a slice of the given string from the byte range
127/// [`begin`, `end`).
128///
129/// This operation is *O*(1).
130///
131/// Prior to 1.20.0, these indexing operations were still supported by
132/// direct implementation of `Index` and `IndexMut`.
133///
134/// # Panics
135///
136/// Panics if `begin` or `end` does not point to the starting byte offset of
137/// a character (as defined by `is_char_boundary`), if `begin > end`, or if
138/// `end > len`.
139///
140/// # Examples
141///
142/// ```
143/// let s = "Löwe 老虎 Léopard";
144/// assert_eq!(&s[0 .. 1], "L");
145///
146/// assert_eq!(&s[1 .. 9], "öwe 老");
147///
148/// // these will panic:
149/// // byte 2 lies within `ö`:
150/// // &s[2 ..3];
151///
152/// // byte 8 lies within `老`
153/// // &s[1 .. 8];
154///
155/// // byte 100 is outside the string
156/// // &s[3 .. 100];
157/// ```
158#[stable(feature = "str_checked_slicing", since = "1.20.0")]
159unsafe impl SliceIndex<str> for ops::Range<usize> {
160 type Output = str;
161 #[inline]
162 fn get(self, slice: &str) -> Option<&Self::Output> {
163 if self.start <= self.end
164 && slice.is_char_boundary(self.start)
165 && slice.is_char_boundary(self.end)
166 {
167 // SAFETY: just checked that `start` and `end` are on a char boundary,
168 // and we are passing in a safe reference, so the return value will also be one.
169 // We also checked char boundaries, so this is valid UTF-8.
170 Some(unsafe { &*self.get_unchecked(slice) })
171 } else {
172 None
173 }
174 }
175 #[inline]
176 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
177 if self.start <= self.end
178 && slice.is_char_boundary(self.start)
179 && slice.is_char_boundary(self.end)
180 {
181 // SAFETY: just checked that `start` and `end` are on a char boundary.
182 // We know the pointer is unique because we got it from `slice`.
183 Some(unsafe { &mut *self.get_unchecked_mut(slice) })
184 } else {
185 None
186 }
187 }
188 #[inline]
189 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
190 let slice = slice as *const [u8];
191
192 assert_unsafe_precondition!(
193 // We'd like to check that the bounds are on char boundaries,
194 // but there's not really a way to do so without reading
195 // behind the pointer, which has aliasing implications.
196 // It's also not possible to move this check up to
197 // `str::get_unchecked` without adding a special function
198 // to `SliceIndex` just for this.
199 check_library_ub,
200 "str::get_unchecked requires that the range is within the string slice",
201 (
202 start: usize = self.start,
203 end: usize = self.end,
204 len: usize = slice.len()
205 ) => end >= start && end <= len,
206 );
207
208 // SAFETY: the caller guarantees that `self` is in bounds of `slice`
209 // which satisfies all the conditions for `add`.
210 unsafe {
211 let new_len = unchecked_sub(self.end, self.start);
212 ptr::slice_from_raw_parts(slice.as_ptr().add(self.start), new_len) as *const str
213 }
214 }
215 #[inline]
216 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
217 let slice = slice as *mut [u8];
218
219 assert_unsafe_precondition!(
220 check_library_ub,
221 "str::get_unchecked_mut requires that the range is within the string slice",
222 (
223 start: usize = self.start,
224 end: usize = self.end,
225 len: usize = slice.len()
226 ) => end >= start && end <= len,
227 );
228
229 // SAFETY: see comments for `get_unchecked`.
230 unsafe {
231 let new_len = unchecked_sub(self.end, self.start);
232 ptr::slice_from_raw_parts_mut(slice.as_mut_ptr().add(self.start), new_len) as *mut str
233 }
234 }
235 #[inline]
236 fn index(self, slice: &str) -> &Self::Output {
237 let (start, end) = (self.start, self.end);
238 match self.get(slice) {
239 Some(s) => s,
240 None => super::slice_error_fail(slice, start, end),
241 }
242 }
243 #[inline]
244 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
245 // is_char_boundary checks that the index is in [0, .len()]
246 // cannot reuse `get` as above, because of NLL trouble
247 if self.start <= self.end
248 && slice.is_char_boundary(self.start)
249 && slice.is_char_boundary(self.end)
250 {
251 // SAFETY: just checked that `start` and `end` are on a char boundary,
252 // and we are passing in a safe reference, so the return value will also be one.
253 unsafe { &mut *self.get_unchecked_mut(slice) }
254 } else {
255 super::slice_error_fail(slice, self.start, self.end)
256 }
257 }
258}
259
260#[unstable(feature = "new_range_api", issue = "125687")]
261unsafe impl SliceIndex<str> for range::Range<usize> {
262 type Output = str;
263 #[inline]
264 fn get(self, slice: &str) -> Option<&Self::Output> {
265 if self.start <= self.end
266 && slice.is_char_boundary(self.start)
267 && slice.is_char_boundary(self.end)
268 {
269 // SAFETY: just checked that `start` and `end` are on a char boundary,
270 // and we are passing in a safe reference, so the return value will also be one.
271 // We also checked char boundaries, so this is valid UTF-8.
272 Some(unsafe { &*self.get_unchecked(slice) })
273 } else {
274 None
275 }
276 }
277 #[inline]
278 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
279 if self.start <= self.end
280 && slice.is_char_boundary(self.start)
281 && slice.is_char_boundary(self.end)
282 {
283 // SAFETY: just checked that `start` and `end` are on a char boundary.
284 // We know the pointer is unique because we got it from `slice`.
285 Some(unsafe { &mut *self.get_unchecked_mut(slice) })
286 } else {
287 None
288 }
289 }
290 #[inline]
291 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
292 let slice = slice as *const [u8];
293
294 assert_unsafe_precondition!(
295 // We'd like to check that the bounds are on char boundaries,
296 // but there's not really a way to do so without reading
297 // behind the pointer, which has aliasing implications.
298 // It's also not possible to move this check up to
299 // `str::get_unchecked` without adding a special function
300 // to `SliceIndex` just for this.
301 check_library_ub,
302 "str::get_unchecked requires that the range is within the string slice",
303 (
304 start: usize = self.start,
305 end: usize = self.end,
306 len: usize = slice.len()
307 ) => end >= start && end <= len,
308 );
309
310 // SAFETY: the caller guarantees that `self` is in bounds of `slice`
311 // which satisfies all the conditions for `add`.
312 unsafe {
313 let new_len = unchecked_sub(self.end, self.start);
314 ptr::slice_from_raw_parts(slice.as_ptr().add(self.start), new_len) as *const str
315 }
316 }
317 #[inline]
318 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
319 let slice = slice as *mut [u8];
320
321 assert_unsafe_precondition!(
322 check_library_ub,
323 "str::get_unchecked_mut requires that the range is within the string slice",
324 (
325 start: usize = self.start,
326 end: usize = self.end,
327 len: usize = slice.len()
328 ) => end >= start && end <= len,
329 );
330
331 // SAFETY: see comments for `get_unchecked`.
332 unsafe {
333 let new_len = unchecked_sub(self.end, self.start);
334 ptr::slice_from_raw_parts_mut(slice.as_mut_ptr().add(self.start), new_len) as *mut str
335 }
336 }
337 #[inline]
338 fn index(self, slice: &str) -> &Self::Output {
339 let (start, end) = (self.start, self.end);
340 match self.get(slice) {
341 Some(s) => s,
342 None => super::slice_error_fail(slice, start, end),
343 }
344 }
345 #[inline]
346 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
347 // is_char_boundary checks that the index is in [0, .len()]
348 // cannot reuse `get` as above, because of NLL trouble
349 if self.start <= self.end
350 && slice.is_char_boundary(self.start)
351 && slice.is_char_boundary(self.end)
352 {
353 // SAFETY: just checked that `start` and `end` are on a char boundary,
354 // and we are passing in a safe reference, so the return value will also be one.
355 unsafe { &mut *self.get_unchecked_mut(slice) }
356 } else {
357 super::slice_error_fail(slice, self.start, self.end)
358 }
359 }
360}
361
362/// Implements substring slicing for arbitrary bounds.
363///
364/// Returns a slice of the given string bounded by the byte indices
365/// provided by each bound.
366///
367/// This operation is *O*(1).
368///
369/// # Panics
370///
371/// Panics if `begin` or `end` (if it exists and once adjusted for
372/// inclusion/exclusion) does not point to the starting byte offset of
373/// a character (as defined by `is_char_boundary`), if `begin > end`, or if
374/// `end > len`.
375#[stable(feature = "slice_index_str_with_ops_bound_pair", since = "1.73.0")]
376unsafe impl SliceIndex<str> for (ops::Bound<usize>, ops::Bound<usize>) {
377 type Output = str;
378
379 #[inline]
380 fn get(self, slice: &str) -> Option<&str> {
381 crate::slice::index::into_range(slice.len(), self)?.get(slice)
382 }
383
384 #[inline]
385 fn get_mut(self, slice: &mut str) -> Option<&mut str> {
386 crate::slice::index::into_range(slice.len(), self)?.get_mut(slice)
387 }
388
389 #[inline]
390 unsafe fn get_unchecked(self, slice: *const str) -> *const str {
391 let len = (slice as *const [u8]).len();
392 // SAFETY: the caller has to uphold the safety contract for `get_unchecked`.
393 unsafe { crate::slice::index::into_range_unchecked(len, self).get_unchecked(slice) }
394 }
395
396 #[inline]
397 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut str {
398 let len = (slice as *mut [u8]).len();
399 // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`.
400 unsafe { crate::slice::index::into_range_unchecked(len, self).get_unchecked_mut(slice) }
401 }
402
403 #[inline]
404 fn index(self, slice: &str) -> &str {
405 crate::slice::index::into_slice_range(slice.len(), self).index(slice)
406 }
407
408 #[inline]
409 fn index_mut(self, slice: &mut str) -> &mut str {
410 crate::slice::index::into_slice_range(slice.len(), self).index_mut(slice)
411 }
412}
413
414/// Implements substring slicing with syntax `&self[.. end]` or `&mut
415/// self[.. end]`.
416///
417/// Returns a slice of the given string from the byte range \[0, `end`).
418/// Equivalent to `&self[0 .. end]` or `&mut self[0 .. end]`.
419///
420/// This operation is *O*(1).
421///
422/// Prior to 1.20.0, these indexing operations were still supported by
423/// direct implementation of `Index` and `IndexMut`.
424///
425/// # Panics
426///
427/// Panics if `end` does not point to the starting byte offset of a
428/// character (as defined by `is_char_boundary`), or if `end > len`.
429#[stable(feature = "str_checked_slicing", since = "1.20.0")]
430unsafe impl SliceIndex<str> for ops::RangeTo<usize> {
431 type Output = str;
432 #[inline]
433 fn get(self, slice: &str) -> Option<&Self::Output> {
434 if slice.is_char_boundary(self.end) {
435 // SAFETY: just checked that `end` is on a char boundary,
436 // and we are passing in a safe reference, so the return value will also be one.
437 Some(unsafe { &*self.get_unchecked(slice) })
438 } else {
439 None
440 }
441 }
442 #[inline]
443 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
444 if slice.is_char_boundary(self.end) {
445 // SAFETY: just checked that `end` is on a char boundary,
446 // and we are passing in a safe reference, so the return value will also be one.
447 Some(unsafe { &mut *self.get_unchecked_mut(slice) })
448 } else {
449 None
450 }
451 }
452 #[inline]
453 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
454 // SAFETY: the caller has to uphold the safety contract for `get_unchecked`.
455 unsafe { (0..self.end).get_unchecked(slice) }
456 }
457 #[inline]
458 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
459 // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`.
460 unsafe { (0..self.end).get_unchecked_mut(slice) }
461 }
462 #[inline]
463 fn index(self, slice: &str) -> &Self::Output {
464 let end = self.end;
465 match self.get(slice) {
466 Some(s) => s,
467 None => super::slice_error_fail(slice, 0, end),
468 }
469 }
470 #[inline]
471 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
472 if slice.is_char_boundary(self.end) {
473 // SAFETY: just checked that `end` is on a char boundary,
474 // and we are passing in a safe reference, so the return value will also be one.
475 unsafe { &mut *self.get_unchecked_mut(slice) }
476 } else {
477 super::slice_error_fail(slice, 0, self.end)
478 }
479 }
480}
481
482/// Implements substring slicing with syntax `&self[begin ..]` or `&mut
483/// self[begin ..]`.
484///
485/// Returns a slice of the given string from the byte range \[`begin`, `len`).
486/// Equivalent to `&self[begin .. len]` or `&mut self[begin .. len]`.
487///
488/// This operation is *O*(1).
489///
490/// Prior to 1.20.0, these indexing operations were still supported by
491/// direct implementation of `Index` and `IndexMut`.
492///
493/// # Panics
494///
495/// Panics if `begin` does not point to the starting byte offset of
496/// a character (as defined by `is_char_boundary`), or if `begin > len`.
497#[stable(feature = "str_checked_slicing", since = "1.20.0")]
498unsafe impl SliceIndex<str> for ops::RangeFrom<usize> {
499 type Output = str;
500 #[inline]
501 fn get(self, slice: &str) -> Option<&Self::Output> {
502 if slice.is_char_boundary(self.start) {
503 // SAFETY: just checked that `start` is on a char boundary,
504 // and we are passing in a safe reference, so the return value will also be one.
505 Some(unsafe { &*self.get_unchecked(slice) })
506 } else {
507 None
508 }
509 }
510 #[inline]
511 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
512 if slice.is_char_boundary(self.start) {
513 // SAFETY: just checked that `start` is on a char boundary,
514 // and we are passing in a safe reference, so the return value will also be one.
515 Some(unsafe { &mut *self.get_unchecked_mut(slice) })
516 } else {
517 None
518 }
519 }
520 #[inline]
521 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
522 let len = (slice as *const [u8]).len();
523 // SAFETY: the caller has to uphold the safety contract for `get_unchecked`.
524 unsafe { (self.start..len).get_unchecked(slice) }
525 }
526 #[inline]
527 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
528 let len = (slice as *mut [u8]).len();
529 // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`.
530 unsafe { (self.start..len).get_unchecked_mut(slice) }
531 }
532 #[inline]
533 fn index(self, slice: &str) -> &Self::Output {
534 let (start, end) = (self.start, slice.len());
535 match self.get(slice) {
536 Some(s) => s,
537 None => super::slice_error_fail(slice, start, end),
538 }
539 }
540 #[inline]
541 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
542 if slice.is_char_boundary(self.start) {
543 // SAFETY: just checked that `start` is on a char boundary,
544 // and we are passing in a safe reference, so the return value will also be one.
545 unsafe { &mut *self.get_unchecked_mut(slice) }
546 } else {
547 super::slice_error_fail(slice, self.start, slice.len())
548 }
549 }
550}
551
552#[unstable(feature = "new_range_api", issue = "125687")]
553unsafe impl SliceIndex<str> for range::RangeFrom<usize> {
554 type Output = str;
555 #[inline]
556 fn get(self, slice: &str) -> Option<&Self::Output> {
557 if slice.is_char_boundary(self.start) {
558 // SAFETY: just checked that `start` is on a char boundary,
559 // and we are passing in a safe reference, so the return value will also be one.
560 Some(unsafe { &*self.get_unchecked(slice) })
561 } else {
562 None
563 }
564 }
565 #[inline]
566 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
567 if slice.is_char_boundary(self.start) {
568 // SAFETY: just checked that `start` is on a char boundary,
569 // and we are passing in a safe reference, so the return value will also be one.
570 Some(unsafe { &mut *self.get_unchecked_mut(slice) })
571 } else {
572 None
573 }
574 }
575 #[inline]
576 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
577 let len = (slice as *const [u8]).len();
578 // SAFETY: the caller has to uphold the safety contract for `get_unchecked`.
579 unsafe { (self.start..len).get_unchecked(slice) }
580 }
581 #[inline]
582 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
583 let len = (slice as *mut [u8]).len();
584 // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`.
585 unsafe { (self.start..len).get_unchecked_mut(slice) }
586 }
587 #[inline]
588 fn index(self, slice: &str) -> &Self::Output {
589 let (start, end) = (self.start, slice.len());
590 match self.get(slice) {
591 Some(s) => s,
592 None => super::slice_error_fail(slice, start, end),
593 }
594 }
595 #[inline]
596 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
597 if slice.is_char_boundary(self.start) {
598 // SAFETY: just checked that `start` is on a char boundary,
599 // and we are passing in a safe reference, so the return value will also be one.
600 unsafe { &mut *self.get_unchecked_mut(slice) }
601 } else {
602 super::slice_error_fail(slice, self.start, slice.len())
603 }
604 }
605}
606
607/// Implements substring slicing with syntax `&self[begin ..= end]` or `&mut
608/// self[begin ..= end]`.
609///
610/// Returns a slice of the given string from the byte range
611/// [`begin`, `end`]. Equivalent to `&self [begin .. end + 1]` or `&mut
612/// self[begin .. end + 1]`, except if `end` has the maximum value for
613/// `usize`.
614///
615/// This operation is *O*(1).
616///
617/// # Panics
618///
619/// Panics if `begin` does not point to the starting byte offset of
620/// a character (as defined by `is_char_boundary`), if `end` does not point
621/// to the ending byte offset of a character (`end + 1` is either a starting
622/// byte offset or equal to `len`), if `begin > end`, or if `end >= len`.
623#[stable(feature = "inclusive_range", since = "1.26.0")]
624unsafe impl SliceIndex<str> for ops::RangeInclusive<usize> {
625 type Output = str;
626 #[inline]
627 fn get(self, slice: &str) -> Option<&Self::Output> {
628 if *self.end() == usize::MAX { None } else { self.into_slice_range().get(slice) }
629 }
630 #[inline]
631 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
632 if *self.end() == usize::MAX { None } else { self.into_slice_range().get_mut(slice) }
633 }
634 #[inline]
635 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
636 // SAFETY: the caller must uphold the safety contract for `get_unchecked`.
637 unsafe { self.into_slice_range().get_unchecked(slice) }
638 }
639 #[inline]
640 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
641 // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`.
642 unsafe { self.into_slice_range().get_unchecked_mut(slice) }
643 }
644 #[inline]
645 fn index(self, slice: &str) -> &Self::Output {
646 if *self.end() == usize::MAX {
647 str_index_overflow_fail();
648 }
649 self.into_slice_range().index(slice)
650 }
651 #[inline]
652 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
653 if *self.end() == usize::MAX {
654 str_index_overflow_fail();
655 }
656 self.into_slice_range().index_mut(slice)
657 }
658}
659
660#[unstable(feature = "new_range_api", issue = "125687")]
661unsafe impl SliceIndex<str> for range::RangeInclusive<usize> {
662 type Output = str;
663 #[inline]
664 fn get(self, slice: &str) -> Option<&Self::Output> {
665 if self.end == usize::MAX { None } else { self.into_slice_range().get(slice) }
666 }
667 #[inline]
668 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
669 if self.end == usize::MAX { None } else { self.into_slice_range().get_mut(slice) }
670 }
671 #[inline]
672 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
673 // SAFETY: the caller must uphold the safety contract for `get_unchecked`.
674 unsafe { self.into_slice_range().get_unchecked(slice) }
675 }
676 #[inline]
677 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
678 // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`.
679 unsafe { self.into_slice_range().get_unchecked_mut(slice) }
680 }
681 #[inline]
682 fn index(self, slice: &str) -> &Self::Output {
683 if self.end == usize::MAX {
684 str_index_overflow_fail();
685 }
686 self.into_slice_range().index(slice)
687 }
688 #[inline]
689 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
690 if self.end == usize::MAX {
691 str_index_overflow_fail();
692 }
693 self.into_slice_range().index_mut(slice)
694 }
695}
696
697/// Implements substring slicing with syntax `&self[..= end]` or `&mut
698/// self[..= end]`.
699///
700/// Returns a slice of the given string from the byte range \[0, `end`\].
701/// Equivalent to `&self [0 .. end + 1]`, except if `end` has the maximum
702/// value for `usize`.
703///
704/// This operation is *O*(1).
705///
706/// # Panics
707///
708/// Panics if `end` does not point to the ending byte offset of a character
709/// (`end + 1` is either a starting byte offset as defined by
710/// `is_char_boundary`, or equal to `len`), or if `end >= len`.
711#[stable(feature = "inclusive_range", since = "1.26.0")]
712unsafe impl SliceIndex<str> for ops::RangeToInclusive<usize> {
713 type Output = str;
714 #[inline]
715 fn get(self, slice: &str) -> Option<&Self::Output> {
716 (0..=self.end).get(slice)
717 }
718 #[inline]
719 fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
720 (0..=self.end).get_mut(slice)
721 }
722 #[inline]
723 unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output {
724 // SAFETY: the caller must uphold the safety contract for `get_unchecked`.
725 unsafe { (0..=self.end).get_unchecked(slice) }
726 }
727 #[inline]
728 unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output {
729 // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`.
730 unsafe { (0..=self.end).get_unchecked_mut(slice) }
731 }
732 #[inline]
733 fn index(self, slice: &str) -> &Self::Output {
734 (0..=self.end).index(slice)
735 }
736 #[inline]
737 fn index_mut(self, slice: &mut str) -> &mut Self::Output {
738 (0..=self.end).index_mut(slice)
739 }
740}
741
742/// Parse a value from a string
743///
744/// `FromStr`'s [`from_str`] method is often used implicitly, through
745/// [`str`]'s [`parse`] method. See [`parse`]'s documentation for examples.
746///
747/// [`from_str`]: FromStr::from_str
748/// [`parse`]: str::parse
749///
750/// `FromStr` does not have a lifetime parameter, and so you can only parse types
751/// that do not contain a lifetime parameter themselves. In other words, you can
752/// parse an `i32` with `FromStr`, but not a `&i32`. You can parse a struct that
753/// contains an `i32`, but not one that contains an `&i32`.
754///
755/// # Examples
756///
757/// Basic implementation of `FromStr` on an example `Point` type:
758///
759/// ```
760/// use std::str::FromStr;
761///
762/// #[derive(Debug, PartialEq)]
763/// struct Point {
764/// x: i32,
765/// y: i32
766/// }
767///
768/// #[derive(Debug, PartialEq, Eq)]
769/// struct ParsePointError;
770///
771/// impl FromStr for Point {
772/// type Err = ParsePointError;
773///
774/// fn from_str(s: &str) -> Result<Self, Self::Err> {
775/// let (x, y) = s
776/// .strip_prefix('(')
777/// .and_then(|s| s.strip_suffix(')'))
778/// .and_then(|s| s.split_once(','))
779/// .ok_or(ParsePointError)?;
780///
781/// let x_fromstr = x.parse::<i32>().map_err(|_| ParsePointError)?;
782/// let y_fromstr = y.parse::<i32>().map_err(|_| ParsePointError)?;
783///
784/// Ok(Point { x: x_fromstr, y: y_fromstr })
785/// }
786/// }
787///
788/// let expected = Ok(Point { x: 1, y: 2 });
789/// // Explicit call
790/// assert_eq!(Point::from_str("(1,2)"), expected);
791/// // Implicit calls, through parse
792/// assert_eq!("(1,2)".parse(), expected);
793/// assert_eq!("(1,2)".parse::<Point>(), expected);
794/// // Invalid input string
795/// assert!(Point::from_str("(1 2)").is_err());
796/// ```
797#[stable(feature = "rust1", since = "1.0.0")]
798pub trait FromStr: Sized {
799 /// The associated error which can be returned from parsing.
800 #[stable(feature = "rust1", since = "1.0.0")]
801 type Err;
802
803 /// Parses a string `s` to return a value of this type.
804 ///
805 /// If parsing succeeds, return the value inside [`Ok`], otherwise
806 /// when the string is ill-formatted return an error specific to the
807 /// inside [`Err`]. The error type is specific to the implementation of the trait.
808 ///
809 /// # Examples
810 ///
811 /// Basic usage with [`i32`], a type that implements `FromStr`:
812 ///
813 /// ```
814 /// use std::str::FromStr;
815 ///
816 /// let s = "5";
817 /// let x = i32::from_str(s).unwrap();
818 ///
819 /// assert_eq!(5, x);
820 /// ```
821 #[stable(feature = "rust1", since = "1.0.0")]
822 #[rustc_diagnostic_item = "from_str_method"]
823 fn from_str(s: &str) -> Result<Self, Self::Err>;
824}
825
826#[stable(feature = "rust1", since = "1.0.0")]
827impl FromStr for bool {
828 type Err = ParseBoolError;
829
830 /// Parse a `bool` from a string.
831 ///
832 /// The only accepted values are `"true"` and `"false"`. Any other input
833 /// will return an error.
834 ///
835 /// # Examples
836 ///
837 /// ```
838 /// use std::str::FromStr;
839 ///
840 /// assert_eq!(FromStr::from_str("true"), Ok(true));
841 /// assert_eq!(FromStr::from_str("false"), Ok(false));
842 /// assert!(<bool as FromStr>::from_str("not even a boolean").is_err());
843 /// ```
844 ///
845 /// Note, in many cases, the `.parse()` method on `str` is more proper.
846 ///
847 /// ```
848 /// assert_eq!("true".parse(), Ok(true));
849 /// assert_eq!("false".parse(), Ok(false));
850 /// assert!("not even a boolean".parse::<bool>().is_err());
851 /// ```
852 #[inline]
853 fn from_str(s: &str) -> Result<bool, ParseBoolError> {
854 match s {
855 "true" => Ok(true),
856 "false" => Ok(false),
857 _ => Err(ParseBoolError),
858 }
859 }
860}
861