1 | //! Utilities for the `str` primitive type. |
---|---|
2 | //! |
3 | //! *[See also the `str` primitive type](str).* |
4 | |
5 | #![stable(feature = "rust1", since = "1.0.0")] |
6 | // Many of the usings in this module are only used in the test configuration. |
7 | // It's cleaner to just turn off the unused_imports warning than to fix them. |
8 | #![allow(unused_imports)] |
9 | |
10 | use core::borrow::{Borrow, BorrowMut}; |
11 | use core::iter::FusedIterator; |
12 | use core::mem::MaybeUninit; |
13 | #[stable(feature = "encode_utf16", since = "1.8.0")] |
14 | pub use core::str::EncodeUtf16; |
15 | #[stable(feature = "split_ascii_whitespace", since = "1.34.0")] |
16 | pub use core::str::SplitAsciiWhitespace; |
17 | #[stable(feature = "split_inclusive", since = "1.51.0")] |
18 | pub use core::str::SplitInclusive; |
19 | #[stable(feature = "rust1", since = "1.0.0")] |
20 | pub use core::str::SplitWhitespace; |
21 | #[stable(feature = "rust1", since = "1.0.0")] |
22 | pub use core::str::pattern; |
23 | use core::str::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher, Utf8Pattern}; |
24 | #[stable(feature = "rust1", since = "1.0.0")] |
25 | pub use core::str::{Bytes, CharIndices, Chars, from_utf8, from_utf8_mut}; |
26 | #[stable(feature = "str_escape", since = "1.34.0")] |
27 | pub use core::str::{EscapeDebug, EscapeDefault, EscapeUnicode}; |
28 | #[stable(feature = "rust1", since = "1.0.0")] |
29 | pub use core::str::{FromStr, Utf8Error}; |
30 | #[allow(deprecated)] |
31 | #[stable(feature = "rust1", since = "1.0.0")] |
32 | pub use core::str::{Lines, LinesAny}; |
33 | #[stable(feature = "rust1", since = "1.0.0")] |
34 | pub use core::str::{MatchIndices, RMatchIndices}; |
35 | #[stable(feature = "rust1", since = "1.0.0")] |
36 | pub use core::str::{Matches, RMatches}; |
37 | #[stable(feature = "rust1", since = "1.0.0")] |
38 | pub use core::str::{ParseBoolError, from_utf8_unchecked, from_utf8_unchecked_mut}; |
39 | #[stable(feature = "rust1", since = "1.0.0")] |
40 | pub use core::str::{RSplit, Split}; |
41 | #[stable(feature = "rust1", since = "1.0.0")] |
42 | pub use core::str::{RSplitN, SplitN}; |
43 | #[stable(feature = "rust1", since = "1.0.0")] |
44 | pub use core::str::{RSplitTerminator, SplitTerminator}; |
45 | #[stable(feature = "utf8_chunks", since = "1.79.0")] |
46 | pub use core::str::{Utf8Chunk, Utf8Chunks}; |
47 | #[unstable(feature = "str_from_raw_parts", issue = "119206")] |
48 | pub use core::str::{from_raw_parts, from_raw_parts_mut}; |
49 | use core::unicode::conversions; |
50 | use core::{mem, ptr}; |
51 | |
52 | use crate::borrow::ToOwned; |
53 | use crate::boxed::Box; |
54 | use crate::slice::{Concat, Join, SliceIndex}; |
55 | use crate::string::String; |
56 | use crate::vec::Vec; |
57 | |
58 | /// Note: `str` in `Concat<str>` is not meaningful here. |
59 | /// This type parameter of the trait only exists to enable another impl. |
60 | #[cfg(not(no_global_oom_handling))] |
61 | #[unstable(feature = "slice_concat_ext", issue = "27747")] |
62 | impl<S: Borrow<str>> Concat<str> for [S] { |
63 | type Output = String; |
64 | |
65 | fn concat(slice: &Self) -> String { |
66 | Join::join(slice, sep:"") |
67 | } |
68 | } |
69 | |
70 | #[cfg(not(no_global_oom_handling))] |
71 | #[unstable(feature = "slice_concat_ext", issue = "27747")] |
72 | impl<S: Borrow<str>> Join<&str> for [S] { |
73 | type Output = String; |
74 | |
75 | fn join(slice: &Self, sep: &str) -> String { |
76 | unsafe { String::from_utf8_unchecked(bytes:join_generic_copy(slice, sep.as_bytes())) } |
77 | } |
78 | } |
79 | |
80 | #[cfg(not(no_global_oom_handling))] |
81 | macro_rules! specialize_for_lengths { |
82 | ($separator:expr, $target:expr, $iter:expr; $($num:expr),*) => {{ |
83 | let mut target = $target; |
84 | let iter = $iter; |
85 | let sep_bytes = $separator; |
86 | match $separator.len() { |
87 | $( |
88 | // loops with hardcoded sizes run much faster |
89 | // specialize the cases with small separator lengths |
90 | $num => { |
91 | for s in iter { |
92 | copy_slice_and_advance!(target, sep_bytes); |
93 | let content_bytes = s.borrow().as_ref(); |
94 | copy_slice_and_advance!(target, content_bytes); |
95 | } |
96 | }, |
97 | )* |
98 | _ => { |
99 | // arbitrary non-zero size fallback |
100 | for s in iter { |
101 | copy_slice_and_advance!(target, sep_bytes); |
102 | let content_bytes = s.borrow().as_ref(); |
103 | copy_slice_and_advance!(target, content_bytes); |
104 | } |
105 | } |
106 | } |
107 | target |
108 | }} |
109 | } |
110 | |
111 | #[cfg(not(no_global_oom_handling))] |
112 | macro_rules! copy_slice_and_advance { |
113 | ($target:expr, $bytes:expr) => { |
114 | let len = $bytes.len(); |
115 | let (head, tail) = { $target }.split_at_mut(len); |
116 | head.copy_from_slice($bytes); |
117 | $target = tail; |
118 | }; |
119 | } |
120 | |
121 | // Optimized join implementation that works for both Vec<T> (T: Copy) and String's inner vec |
122 | // Currently (2018-05-13) there is a bug with type inference and specialization (see issue #36262) |
123 | // For this reason SliceConcat<T> is not specialized for T: Copy and SliceConcat<str> is the |
124 | // only user of this function. It is left in place for the time when that is fixed. |
125 | // |
126 | // the bounds for String-join are S: Borrow<str> and for Vec-join Borrow<[T]> |
127 | // [T] and str both impl AsRef<[T]> for some T |
128 | // => s.borrow().as_ref() and we always have slices |
129 | #[cfg(not(no_global_oom_handling))] |
130 | fn join_generic_copy<B, T, S>(slice: &[S], sep: &[T]) -> Vec<T> |
131 | where |
132 | T: Copy, |
133 | B: AsRef<[T]> + ?Sized, |
134 | S: Borrow<B>, |
135 | { |
136 | let sep_len = sep.len(); |
137 | let mut iter = slice.iter(); |
138 | |
139 | // the first slice is the only one without a separator preceding it |
140 | let first = match iter.next() { |
141 | Some(first) => first, |
142 | None => return vec![], |
143 | }; |
144 | |
145 | // compute the exact total length of the joined Vec |
146 | // if the `len` calculation overflows, we'll panic |
147 | // we would have run out of memory anyway and the rest of the function requires |
148 | // the entire Vec pre-allocated for safety |
149 | let reserved_len = sep_len |
150 | .checked_mul(iter.len()) |
151 | .and_then(|n| { |
152 | slice.iter().map(|s| s.borrow().as_ref().len()).try_fold(n, usize::checked_add) |
153 | }) |
154 | .expect("attempt to join into collection with len > usize::MAX"); |
155 | |
156 | // prepare an uninitialized buffer |
157 | let mut result = Vec::with_capacity(reserved_len); |
158 | debug_assert!(result.capacity() >= reserved_len); |
159 | |
160 | result.extend_from_slice(first.borrow().as_ref()); |
161 | |
162 | unsafe { |
163 | let pos = result.len(); |
164 | let target = result.spare_capacity_mut().get_unchecked_mut(..reserved_len - pos); |
165 | |
166 | // Convert the separator and slices to slices of MaybeUninit |
167 | // to simplify implementation in specialize_for_lengths |
168 | let sep_uninit = core::slice::from_raw_parts(sep.as_ptr().cast(), sep.len()); |
169 | let iter_uninit = iter.map(|it| { |
170 | let it = it.borrow().as_ref(); |
171 | core::slice::from_raw_parts(it.as_ptr().cast(), it.len()) |
172 | }); |
173 | |
174 | // copy separator and slices over without bounds checks |
175 | // generate loops with hardcoded offsets for small separators |
176 | // massive improvements possible (~ x2) |
177 | let remain = specialize_for_lengths!(sep_uninit, target, iter_uninit; 0, 1, 2, 3, 4); |
178 | |
179 | // A weird borrow implementation may return different |
180 | // slices for the length calculation and the actual copy. |
181 | // Make sure we don't expose uninitialized bytes to the caller. |
182 | let result_len = reserved_len - remain.len(); |
183 | result.set_len(result_len); |
184 | } |
185 | result |
186 | } |
187 | |
188 | #[stable(feature = "rust1", since = "1.0.0")] |
189 | impl Borrow<str> for String { |
190 | #[inline] |
191 | fn borrow(&self) -> &str { |
192 | &self[..] |
193 | } |
194 | } |
195 | |
196 | #[stable(feature = "string_borrow_mut", since = "1.36.0")] |
197 | impl BorrowMut<str> for String { |
198 | #[inline] |
199 | fn borrow_mut(&mut self) -> &mut str { |
200 | &mut self[..] |
201 | } |
202 | } |
203 | |
204 | #[cfg(not(no_global_oom_handling))] |
205 | #[stable(feature = "rust1", since = "1.0.0")] |
206 | impl ToOwned for str { |
207 | type Owned = String; |
208 | |
209 | #[inline] |
210 | fn to_owned(&self) -> String { |
211 | unsafe { String::from_utf8_unchecked(self.as_bytes().to_owned()) } |
212 | } |
213 | |
214 | #[inline] |
215 | fn clone_into(&self, target: &mut String) { |
216 | target.clear(); |
217 | target.push_str(self); |
218 | } |
219 | } |
220 | |
221 | /// Methods for string slices. |
222 | impl str { |
223 | /// Converts a `Box<str>` into a `Box<[u8]>` without copying or allocating. |
224 | /// |
225 | /// # Examples |
226 | /// |
227 | /// ``` |
228 | /// let s = "this is a string"; |
229 | /// let boxed_str = s.to_owned().into_boxed_str(); |
230 | /// let boxed_bytes = boxed_str.into_boxed_bytes(); |
231 | /// assert_eq!(*boxed_bytes, *s.as_bytes()); |
232 | /// ``` |
233 | #[rustc_allow_incoherent_impl] |
234 | #[stable(feature = "str_box_extras", since = "1.20.0")] |
235 | #[must_use= "`self` will be dropped if the result is not used"] |
236 | #[inline] |
237 | pub fn into_boxed_bytes(self: Box<Self>) -> Box<[u8]> { |
238 | self.into() |
239 | } |
240 | |
241 | /// Replaces all matches of a pattern with another string. |
242 | /// |
243 | /// `replace` creates a new [`String`], and copies the data from this string slice into it. |
244 | /// While doing so, it attempts to find matches of a pattern. If it finds any, it |
245 | /// replaces them with the replacement string slice. |
246 | /// |
247 | /// # Examples |
248 | /// |
249 | /// ``` |
250 | /// let s = "this is old"; |
251 | /// |
252 | /// assert_eq!("this is new", s.replace( "old", "new")); |
253 | /// assert_eq!("than an old", s.replace( "is", "an")); |
254 | /// ``` |
255 | /// |
256 | /// When the pattern doesn't match, it returns this string slice as [`String`]: |
257 | /// |
258 | /// ``` |
259 | /// let s = "this is old"; |
260 | /// assert_eq!(s, s.replace("cookie monster", "little lamb")); |
261 | /// ``` |
262 | #[cfg(not(no_global_oom_handling))] |
263 | #[rustc_allow_incoherent_impl] |
264 | #[must_use= "this returns the replaced string as a new allocation, \ |
265 | without modifying the original"] |
266 | #[stable(feature = "rust1", since = "1.0.0")] |
267 | #[inline] |
268 | pub fn replace<P: Pattern>(&self, from: P, to: &str) -> String { |
269 | // Fast path for replacing a single ASCII character with another. |
270 | if let Some(from_byte) = match from.as_utf8_pattern() { |
271 | Some(Utf8Pattern::StringPattern([from_byte])) => Some(*from_byte), |
272 | Some(Utf8Pattern::CharPattern(c)) => c.as_ascii().map(|ascii_char| ascii_char.to_u8()), |
273 | _ => None, |
274 | } { |
275 | if let [to_byte] = to.as_bytes() { |
276 | return unsafe { replace_ascii(self.as_bytes(), from_byte, *to_byte) }; |
277 | } |
278 | } |
279 | // Set result capacity to self.len() when from.len() <= to.len() |
280 | let default_capacity = match from.as_utf8_pattern() { |
281 | Some(Utf8Pattern::StringPattern(s)) if s.len() <= to.len() => self.len(), |
282 | Some(Utf8Pattern::CharPattern(c)) if c.len_utf8() <= to.len() => self.len(), |
283 | _ => 0, |
284 | }; |
285 | let mut result = String::with_capacity(default_capacity); |
286 | let mut last_end = 0; |
287 | for (start, part) in self.match_indices(from) { |
288 | result.push_str(unsafe { self.get_unchecked(last_end..start) }); |
289 | result.push_str(to); |
290 | last_end = start + part.len(); |
291 | } |
292 | result.push_str(unsafe { self.get_unchecked(last_end..self.len()) }); |
293 | result |
294 | } |
295 | |
296 | /// Replaces first N matches of a pattern with another string. |
297 | /// |
298 | /// `replacen` creates a new [`String`], and copies the data from this string slice into it. |
299 | /// While doing so, it attempts to find matches of a pattern. If it finds any, it |
300 | /// replaces them with the replacement string slice at most `count` times. |
301 | /// |
302 | /// # Examples |
303 | /// |
304 | /// ``` |
305 | /// let s = "foo foo 123 foo"; |
306 | /// assert_eq!("new new 123 foo", s.replacen( "foo", "new", 2)); |
307 | /// assert_eq!("faa fao 123 foo", s.replacen( 'o', "a", 3)); |
308 | /// assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1)); |
309 | /// ``` |
310 | /// |
311 | /// When the pattern doesn't match, it returns this string slice as [`String`]: |
312 | /// |
313 | /// ``` |
314 | /// let s = "this is old"; |
315 | /// assert_eq!(s, s.replacen("cookie monster", "little lamb", 10)); |
316 | /// ``` |
317 | #[cfg(not(no_global_oom_handling))] |
318 | #[rustc_allow_incoherent_impl] |
319 | #[doc(alias = "replace_first")] |
320 | #[must_use= "this returns the replaced string as a new allocation, \ |
321 | without modifying the original"] |
322 | #[stable(feature = "str_replacen", since = "1.16.0")] |
323 | pub fn replacen<P: Pattern>(&self, pat: P, to: &str, count: usize) -> String { |
324 | // Hope to reduce the times of re-allocation |
325 | let mut result = String::with_capacity(32); |
326 | let mut last_end = 0; |
327 | for (start, part) in self.match_indices(pat).take(count) { |
328 | result.push_str(unsafe { self.get_unchecked(last_end..start) }); |
329 | result.push_str(to); |
330 | last_end = start + part.len(); |
331 | } |
332 | result.push_str(unsafe { self.get_unchecked(last_end..self.len()) }); |
333 | result |
334 | } |
335 | |
336 | /// Returns the lowercase equivalent of this string slice, as a new [`String`]. |
337 | /// |
338 | /// 'Lowercase' is defined according to the terms of the Unicode Derived Core Property |
339 | /// `Lowercase`. |
340 | /// |
341 | /// Since some characters can expand into multiple characters when changing |
342 | /// the case, this function returns a [`String`] instead of modifying the |
343 | /// parameter in-place. |
344 | /// |
345 | /// # Examples |
346 | /// |
347 | /// Basic usage: |
348 | /// |
349 | /// ``` |
350 | /// let s = "HELLO"; |
351 | /// |
352 | /// assert_eq!("hello", s.to_lowercase()); |
353 | /// ``` |
354 | /// |
355 | /// A tricky example, with sigma: |
356 | /// |
357 | /// ``` |
358 | /// let sigma = "Σ"; |
359 | /// |
360 | /// assert_eq!("σ", sigma.to_lowercase()); |
361 | /// |
362 | /// // but at the end of a word, it's ς, not σ: |
363 | /// let odysseus = "ὈΔΥΣΣΕΎΣ"; |
364 | /// |
365 | /// assert_eq!("ὀδυσσεύς", odysseus.to_lowercase()); |
366 | /// ``` |
367 | /// |
368 | /// Languages without case are not changed: |
369 | /// |
370 | /// ``` |
371 | /// let new_year = "农历新年"; |
372 | /// |
373 | /// assert_eq!(new_year, new_year.to_lowercase()); |
374 | /// ``` |
375 | #[cfg(not(no_global_oom_handling))] |
376 | #[rustc_allow_incoherent_impl] |
377 | #[must_use= "this returns the lowercase string as a new String, \ |
378 | without modifying the original"] |
379 | #[stable(feature = "unicode_case_mapping", since = "1.2.0")] |
380 | pub fn to_lowercase(&self) -> String { |
381 | let (mut s, rest) = convert_while_ascii(self, u8::to_ascii_lowercase); |
382 | |
383 | let prefix_len = s.len(); |
384 | |
385 | for (i, c) in rest.char_indices() { |
386 | if c == 'Σ'{ |
387 | // Σ maps to σ, except at the end of a word where it maps to ς. |
388 | // This is the only conditional (contextual) but language-independent mapping |
389 | // in `SpecialCasing.txt`, |
390 | // so hard-code it rather than have a generic "condition" mechanism. |
391 | // See https://github.com/rust-lang/rust/issues/26035 |
392 | let sigma_lowercase = map_uppercase_sigma(self, prefix_len + i); |
393 | s.push(sigma_lowercase); |
394 | } else { |
395 | match conversions::to_lower(c) { |
396 | [a, '\0 ', _] => s.push(a), |
397 | [a, b, '\0 '] => { |
398 | s.push(a); |
399 | s.push(b); |
400 | } |
401 | [a, b, c] => { |
402 | s.push(a); |
403 | s.push(b); |
404 | s.push(c); |
405 | } |
406 | } |
407 | } |
408 | } |
409 | return s; |
410 | |
411 | fn map_uppercase_sigma(from: &str, i: usize) -> char { |
412 | // See https://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992 |
413 | // for the definition of `Final_Sigma`. |
414 | debug_assert!('Σ'.len_utf8() == 2); |
415 | let is_word_final = case_ignorable_then_cased(from[..i].chars().rev()) |
416 | && !case_ignorable_then_cased(from[i + 2..].chars()); |
417 | if is_word_final { 'ς'} else { 'σ'} |
418 | } |
419 | |
420 | fn case_ignorable_then_cased<I: Iterator<Item = char>>(iter: I) -> bool { |
421 | use core::unicode::{Case_Ignorable, Cased}; |
422 | match iter.skip_while(|&c| Case_Ignorable(c)).next() { |
423 | Some(c) => Cased(c), |
424 | None => false, |
425 | } |
426 | } |
427 | } |
428 | |
429 | /// Returns the uppercase equivalent of this string slice, as a new [`String`]. |
430 | /// |
431 | /// 'Uppercase' is defined according to the terms of the Unicode Derived Core Property |
432 | /// `Uppercase`. |
433 | /// |
434 | /// Since some characters can expand into multiple characters when changing |
435 | /// the case, this function returns a [`String`] instead of modifying the |
436 | /// parameter in-place. |
437 | /// |
438 | /// # Examples |
439 | /// |
440 | /// Basic usage: |
441 | /// |
442 | /// ``` |
443 | /// let s = "hello"; |
444 | /// |
445 | /// assert_eq!("HELLO", s.to_uppercase()); |
446 | /// ``` |
447 | /// |
448 | /// Scripts without case are not changed: |
449 | /// |
450 | /// ``` |
451 | /// let new_year = "农历新年"; |
452 | /// |
453 | /// assert_eq!(new_year, new_year.to_uppercase()); |
454 | /// ``` |
455 | /// |
456 | /// One character can become multiple: |
457 | /// ``` |
458 | /// let s = "tschüß"; |
459 | /// |
460 | /// assert_eq!("TSCHÜSS", s.to_uppercase()); |
461 | /// ``` |
462 | #[cfg(not(no_global_oom_handling))] |
463 | #[rustc_allow_incoherent_impl] |
464 | #[must_use= "this returns the uppercase string as a new String, \ |
465 | without modifying the original"] |
466 | #[stable(feature = "unicode_case_mapping", since = "1.2.0")] |
467 | pub fn to_uppercase(&self) -> String { |
468 | let (mut s, rest) = convert_while_ascii(self, u8::to_ascii_uppercase); |
469 | |
470 | for c in rest.chars() { |
471 | match conversions::to_upper(c) { |
472 | [a, '\0 ', _] => s.push(a), |
473 | [a, b, '\0 '] => { |
474 | s.push(a); |
475 | s.push(b); |
476 | } |
477 | [a, b, c] => { |
478 | s.push(a); |
479 | s.push(b); |
480 | s.push(c); |
481 | } |
482 | } |
483 | } |
484 | s |
485 | } |
486 | |
487 | /// Converts a [`Box<str>`] into a [`String`] without copying or allocating. |
488 | /// |
489 | /// # Examples |
490 | /// |
491 | /// ``` |
492 | /// let string = String::from("birthday gift"); |
493 | /// let boxed_str = string.clone().into_boxed_str(); |
494 | /// |
495 | /// assert_eq!(boxed_str.into_string(), string); |
496 | /// ``` |
497 | #[stable(feature = "box_str", since = "1.4.0")] |
498 | #[rustc_allow_incoherent_impl] |
499 | #[must_use= "`self` will be dropped if the result is not used"] |
500 | #[inline] |
501 | pub fn into_string(self: Box<Self>) -> String { |
502 | let slice = Box::<[u8]>::from(self); |
503 | unsafe { String::from_utf8_unchecked(slice.into_vec()) } |
504 | } |
505 | |
506 | /// Creates a new [`String`] by repeating a string `n` times. |
507 | /// |
508 | /// # Panics |
509 | /// |
510 | /// This function will panic if the capacity would overflow. |
511 | /// |
512 | /// # Examples |
513 | /// |
514 | /// Basic usage: |
515 | /// |
516 | /// ``` |
517 | /// assert_eq!("abc".repeat(4), String::from( "abcabcabcabc")); |
518 | /// ``` |
519 | /// |
520 | /// A panic upon overflow: |
521 | /// |
522 | /// ```should_panic |
523 | /// // this will panic at runtime |
524 | /// let huge = "0123456789abcdef".repeat(usize::MAX); |
525 | /// ``` |
526 | #[cfg(not(no_global_oom_handling))] |
527 | #[rustc_allow_incoherent_impl] |
528 | #[must_use] |
529 | #[stable(feature = "repeat_str", since = "1.16.0")] |
530 | #[inline] |
531 | pub fn repeat(&self, n: usize) -> String { |
532 | unsafe { String::from_utf8_unchecked(self.as_bytes().repeat(n)) } |
533 | } |
534 | |
535 | /// Returns a copy of this string where each character is mapped to its |
536 | /// ASCII upper case equivalent. |
537 | /// |
538 | /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', |
539 | /// but non-ASCII letters are unchanged. |
540 | /// |
541 | /// To uppercase the value in-place, use [`make_ascii_uppercase`]. |
542 | /// |
543 | /// To uppercase ASCII characters in addition to non-ASCII characters, use |
544 | /// [`to_uppercase`]. |
545 | /// |
546 | /// # Examples |
547 | /// |
548 | /// ``` |
549 | /// let s = "Grüße, Jürgen ❤"; |
550 | /// |
551 | /// assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase()); |
552 | /// ``` |
553 | /// |
554 | /// [`make_ascii_uppercase`]: str::make_ascii_uppercase |
555 | /// [`to_uppercase`]: #method.to_uppercase |
556 | #[cfg(not(no_global_oom_handling))] |
557 | #[rustc_allow_incoherent_impl] |
558 | #[must_use= "to uppercase the value in-place, use `make_ascii_uppercase()`"] |
559 | #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
560 | #[inline] |
561 | pub fn to_ascii_uppercase(&self) -> String { |
562 | let mut s = self.to_owned(); |
563 | s.make_ascii_uppercase(); |
564 | s |
565 | } |
566 | |
567 | /// Returns a copy of this string where each character is mapped to its |
568 | /// ASCII lower case equivalent. |
569 | /// |
570 | /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', |
571 | /// but non-ASCII letters are unchanged. |
572 | /// |
573 | /// To lowercase the value in-place, use [`make_ascii_lowercase`]. |
574 | /// |
575 | /// To lowercase ASCII characters in addition to non-ASCII characters, use |
576 | /// [`to_lowercase`]. |
577 | /// |
578 | /// # Examples |
579 | /// |
580 | /// ``` |
581 | /// let s = "Grüße, Jürgen ❤"; |
582 | /// |
583 | /// assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase()); |
584 | /// ``` |
585 | /// |
586 | /// [`make_ascii_lowercase`]: str::make_ascii_lowercase |
587 | /// [`to_lowercase`]: #method.to_lowercase |
588 | #[cfg(not(no_global_oom_handling))] |
589 | #[rustc_allow_incoherent_impl] |
590 | #[must_use= "to lowercase the value in-place, use `make_ascii_lowercase()`"] |
591 | #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
592 | #[inline] |
593 | pub fn to_ascii_lowercase(&self) -> String { |
594 | let mut s = self.to_owned(); |
595 | s.make_ascii_lowercase(); |
596 | s |
597 | } |
598 | } |
599 | |
600 | /// Converts a boxed slice of bytes to a boxed string slice without checking |
601 | /// that the string contains valid UTF-8. |
602 | /// |
603 | /// # Safety |
604 | /// |
605 | /// * The provided bytes must contain a valid UTF-8 sequence. |
606 | /// |
607 | /// # Examples |
608 | /// |
609 | /// ``` |
610 | /// let smile_utf8 = Box::new([226, 152, 186]); |
611 | /// let smile = unsafe { std::str::from_boxed_utf8_unchecked(smile_utf8) }; |
612 | /// |
613 | /// assert_eq!("☺", &*smile); |
614 | /// ``` |
615 | #[stable(feature = "str_box_extras", since = "1.20.0")] |
616 | #[must_use] |
617 | #[inline] |
618 | pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> { |
619 | unsafe { Box::from_raw(Box::into_raw(v) as *mut str) } |
620 | } |
621 | |
622 | /// Converts leading ascii bytes in `s` by calling the `convert` function. |
623 | /// |
624 | /// For better average performance, this happens in chunks of `2*size_of::<usize>()`. |
625 | /// |
626 | /// Returns a tuple of the converted prefix and the remainder starting from |
627 | /// the first non-ascii character. |
628 | /// |
629 | /// This function is only public so that it can be verified in a codegen test, |
630 | /// see `issue-123712-str-to-lower-autovectorization.rs`. |
631 | #[unstable(feature = "str_internals", issue = "none")] |
632 | #[doc(hidden)] |
633 | #[inline] |
634 | #[cfg(not(no_global_oom_handling))] |
635 | pub fn convert_while_ascii(s: &str, convert: fn(&u8) -> u8) -> (String, &str) { |
636 | // Process the input in chunks of 16 bytes to enable auto-vectorization. |
637 | // Previously the chunk size depended on the size of `usize`, |
638 | // but on 32-bit platforms with sse or neon is also the better choice. |
639 | // The only downside on other platforms would be a bit more loop-unrolling. |
640 | const N: usize = 16; |
641 | |
642 | let mut slice = s.as_bytes(); |
643 | let mut out = Vec::with_capacity(slice.len()); |
644 | let mut out_slice = out.spare_capacity_mut(); |
645 | |
646 | let mut ascii_prefix_len = 0_usize; |
647 | let mut is_ascii = [false; N]; |
648 | |
649 | while slice.len() >= N { |
650 | // SAFETY: checked in loop condition |
651 | let chunk = unsafe { slice.get_unchecked(..N) }; |
652 | // SAFETY: out_slice has at least same length as input slice and gets sliced with the same offsets |
653 | let out_chunk = unsafe { out_slice.get_unchecked_mut(..N) }; |
654 | |
655 | for j in 0..N { |
656 | is_ascii[j] = chunk[j] <= 127; |
657 | } |
658 | |
659 | // Auto-vectorization for this check is a bit fragile, sum and comparing against the chunk |
660 | // size gives the best result, specifically a pmovmsk instruction on x86. |
661 | // See https://github.com/llvm/llvm-project/issues/96395 for why llvm currently does not |
662 | // currently recognize other similar idioms. |
663 | if is_ascii.iter().map(|x| *x as u8).sum::<u8>() as usize != N { |
664 | break; |
665 | } |
666 | |
667 | for j in 0..N { |
668 | out_chunk[j] = MaybeUninit::new(convert(&chunk[j])); |
669 | } |
670 | |
671 | ascii_prefix_len += N; |
672 | slice = unsafe { slice.get_unchecked(N..) }; |
673 | out_slice = unsafe { out_slice.get_unchecked_mut(N..) }; |
674 | } |
675 | |
676 | // handle the remainder as individual bytes |
677 | while slice.len() > 0 { |
678 | let byte = slice[0]; |
679 | if byte > 127 { |
680 | break; |
681 | } |
682 | // SAFETY: out_slice has at least same length as input slice |
683 | unsafe { |
684 | *out_slice.get_unchecked_mut(0) = MaybeUninit::new(convert(&byte)); |
685 | } |
686 | ascii_prefix_len += 1; |
687 | slice = unsafe { slice.get_unchecked(1..) }; |
688 | out_slice = unsafe { out_slice.get_unchecked_mut(1..) }; |
689 | } |
690 | |
691 | unsafe { |
692 | // SAFETY: ascii_prefix_len bytes have been initialized above |
693 | out.set_len(ascii_prefix_len); |
694 | |
695 | // SAFETY: We have written only valid ascii to the output vec |
696 | let ascii_string = String::from_utf8_unchecked(out); |
697 | |
698 | // SAFETY: we know this is a valid char boundary |
699 | // since we only skipped over leading ascii bytes |
700 | let rest = core::str::from_utf8_unchecked(slice); |
701 | |
702 | (ascii_string, rest) |
703 | } |
704 | } |
705 | #[inline] |
706 | #[cfg(not(no_global_oom_handling))] |
707 | #[allow(dead_code)] |
708 | /// Faster implementation of string replacement for ASCII to ASCII cases. |
709 | /// Should produce fast vectorized code. |
710 | unsafe fn replace_ascii(utf8_bytes: &[u8], from: u8, to: u8) -> String { |
711 | let result: Vec<u8> = utf8_bytes.iter().map(|b: &u8| if *b == from { to } else { *b }).collect(); |
712 | // SAFETY: We replaced ascii with ascii on valid utf8 strings. |
713 | unsafe { String::from_utf8_unchecked(bytes:result) } |
714 | } |
715 |
Definitions
- Output
- concat
- Output
- join
- specialize_for_lengths
- copy_slice_and_advance
- join_generic_copy
- borrow
- borrow_mut
- Owned
- to_owned
- clone_into
- into_boxed_bytes
- replace
- replacen
- to_lowercase
- map_uppercase_sigma
- case_ignorable_then_cased
- to_uppercase
- into_string
- repeat
- to_ascii_uppercase
- to_ascii_lowercase
- from_boxed_utf8_unchecked
- convert_while_ascii
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