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29967ef6 | 1 | //! A UTF-8–encoded, growable string. |
92a42be0 | 2 | //! |
29967ef6 XL |
3 | //! This module contains the [`String`] type, the [`ToString`] trait for |
4 | //! converting to strings, and several error types that may result from | |
5 | //! working with [`String`]s. | |
92a42be0 | 6 | //! |
9cc50fc6 SL |
7 | //! # Examples |
8 | //! | |
c30ab7b3 | 9 | //! There are multiple ways to create a new [`String`] from a string literal: |
9cc50fc6 | 10 | //! |
c30ab7b3 | 11 | //! ``` |
9cc50fc6 SL |
12 | //! let s = "Hello".to_string(); |
13 | //! | |
14 | //! let s = String::from("world"); | |
15 | //! let s: String = "also this".into(); | |
16 | //! ``` | |
17 | //! | |
c30ab7b3 | 18 | //! You can create a new [`String`] from an existing one by concatenating with |
9cc50fc6 SL |
19 | //! `+`: |
20 | //! | |
c30ab7b3 | 21 | //! ``` |
9cc50fc6 SL |
22 | //! let s = "Hello".to_string(); |
23 | //! | |
24 | //! let message = s + " world!"; | |
25 | //! ``` | |
26 | //! | |
3b2f2976 | 27 | //! If you have a vector of valid UTF-8 bytes, you can make a [`String`] out of |
9cc50fc6 SL |
28 | //! it. You can do the reverse too. |
29 | //! | |
c30ab7b3 | 30 | //! ``` |
9cc50fc6 SL |
31 | //! let sparkle_heart = vec![240, 159, 146, 150]; |
32 | //! | |
33 | //! // We know these bytes are valid, so we'll use `unwrap()`. | |
34 | //! let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); | |
35 | //! | |
36 | //! assert_eq!("💖", sparkle_heart); | |
37 | //! | |
38 | //! let bytes = sparkle_heart.into_bytes(); | |
39 | //! | |
40 | //! assert_eq!(bytes, [240, 159, 146, 150]); | |
41 | //! ``` | |
1a4d82fc | 42 | |
85aaf69f | 43 | #![stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 44 | |
17df50a5 | 45 | #[cfg(not(no_global_oom_handling))] |
83c7162d | 46 | use core::char::{decode_utf16, REPLACEMENT_CHARACTER}; |
1a4d82fc JJ |
47 | use core::fmt; |
48 | use core::hash; | |
17df50a5 XL |
49 | #[cfg(not(no_global_oom_handling))] |
50 | use core::iter::FromIterator; | |
51 | use core::iter::{from_fn, FusedIterator}; | |
52 | #[cfg(not(no_global_oom_handling))] | |
53 | use core::ops::Add; | |
54 | #[cfg(not(no_global_oom_handling))] | |
55 | use core::ops::AddAssign; | |
56 | #[cfg(not(no_global_oom_handling))] | |
9fa01778 | 57 | use core::ops::Bound::{Excluded, Included, Unbounded}; |
17df50a5 | 58 | use core::ops::{self, Index, IndexMut, Range, RangeBounds}; |
1a4d82fc | 59 | use core::ptr; |
6a06907d | 60 | use core::slice; |
17df50a5 XL |
61 | #[cfg(not(no_global_oom_handling))] |
62 | use core::str::lossy; | |
63 | use core::str::pattern::Pattern; | |
1a4d82fc | 64 | |
17df50a5 | 65 | #[cfg(not(no_global_oom_handling))] |
9fa01778 | 66 | use crate::borrow::{Cow, ToOwned}; |
9fa01778 | 67 | use crate::boxed::Box; |
dfeec247 | 68 | use crate::collections::TryReserveError; |
17df50a5 XL |
69 | use crate::str::{self, Chars, Utf8Error}; |
70 | #[cfg(not(no_global_oom_handling))] | |
71 | use crate::str::{from_boxed_utf8_unchecked, FromStr}; | |
9fa01778 | 72 | use crate::vec::Vec; |
1a4d82fc | 73 | |
29967ef6 | 74 | /// A UTF-8–encoded, growable string. |
92a42be0 SL |
75 | /// |
76 | /// The `String` type is the most common string type that has ownership over the | |
77 | /// contents of the string. It has a close relationship with its borrowed | |
78 | /// counterpart, the primitive [`str`]. | |
79 | /// | |
92a42be0 SL |
80 | /// # Examples |
81 | /// | |
c295e0f8 | 82 | /// You can create a `String` from [a literal string][`&str`] with [`String::from`]: |
3dfed10e XL |
83 | /// |
84 | /// [`String::from`]: From::from | |
92a42be0 SL |
85 | /// |
86 | /// ``` | |
87 | /// let hello = String::from("Hello, world!"); | |
88 | /// ``` | |
89 | /// | |
cc61c64b XL |
90 | /// You can append a [`char`] to a `String` with the [`push`] method, and |
91 | /// append a [`&str`] with the [`push_str`] method: | |
92a42be0 SL |
92 | /// |
93 | /// ``` | |
94 | /// let mut hello = String::from("Hello, "); | |
95 | /// | |
96 | /// hello.push('w'); | |
97 | /// hello.push_str("orld!"); | |
98 | /// ``` | |
99 | /// | |
3dfed10e XL |
100 | /// [`push`]: String::push |
101 | /// [`push_str`]: String::push_str | |
92a42be0 SL |
102 | /// |
103 | /// If you have a vector of UTF-8 bytes, you can create a `String` from it with | |
cc61c64b | 104 | /// the [`from_utf8`] method: |
92a42be0 SL |
105 | /// |
106 | /// ``` | |
107 | /// // some bytes, in a vector | |
108 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
109 | /// | |
110 | /// // We know these bytes are valid, so we'll use `unwrap()`. | |
111 | /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); | |
112 | /// | |
113 | /// assert_eq!("💖", sparkle_heart); | |
114 | /// ``` | |
115 | /// | |
3dfed10e | 116 | /// [`from_utf8`]: String::from_utf8 |
92a42be0 SL |
117 | /// |
118 | /// # UTF-8 | |
119 | /// | |
120 | /// `String`s are always valid UTF-8. This has a few implications, the first of | |
121 | /// which is that if you need a non-UTF-8 string, consider [`OsString`]. It is | |
122 | /// similar, but without the UTF-8 constraint. The second implication is that | |
123 | /// you cannot index into a `String`: | |
124 | /// | |
041b39d2 | 125 | /// ```compile_fail,E0277 |
92a42be0 SL |
126 | /// let s = "hello"; |
127 | /// | |
128 | /// println!("The first letter of s is {}", s[0]); // ERROR!!! | |
129 | /// ``` | |
130 | /// | |
c295e0f8 | 131 | /// [`OsString`]: ../../std/ffi/struct.OsString.html "ffi::OsString" |
92a42be0 SL |
132 | /// |
133 | /// Indexing is intended to be a constant-time operation, but UTF-8 encoding | |
9e0c209e | 134 | /// does not allow us to do this. Furthermore, it's not clear what sort of |
92a42be0 | 135 | /// thing the index should return: a byte, a codepoint, or a grapheme cluster. |
cc61c64b | 136 | /// The [`bytes`] and [`chars`] methods return iterators over the first |
92a42be0 SL |
137 | /// two, respectively. |
138 | /// | |
3dfed10e XL |
139 | /// [`bytes`]: str::bytes |
140 | /// [`chars`]: str::chars | |
92a42be0 SL |
141 | /// |
142 | /// # Deref | |
143 | /// | |
c295e0f8 | 144 | /// `String` implements <code>[Deref]<Target = [str]></code>, and so inherits all of [`str`]'s |
3b2f2976 | 145 | /// methods. In addition, this means that you can pass a `String` to a |
92a42be0 SL |
146 | /// function which takes a [`&str`] by using an ampersand (`&`): |
147 | /// | |
148 | /// ``` | |
149 | /// fn takes_str(s: &str) { } | |
150 | /// | |
151 | /// let s = String::from("Hello"); | |
152 | /// | |
153 | /// takes_str(&s); | |
154 | /// ``` | |
155 | /// | |
92a42be0 SL |
156 | /// This will create a [`&str`] from the `String` and pass it in. This |
157 | /// conversion is very inexpensive, and so generally, functions will accept | |
3b2f2976 XL |
158 | /// [`&str`]s as arguments unless they need a `String` for some specific |
159 | /// reason. | |
160 | /// | |
161 | /// In certain cases Rust doesn't have enough information to make this | |
162 | /// conversion, known as [`Deref`] coercion. In the following example a string | |
163 | /// slice [`&'a str`][`&str`] implements the trait `TraitExample`, and the function | |
164 | /// `example_func` takes anything that implements the trait. In this case Rust | |
165 | /// would need to make two implicit conversions, which Rust doesn't have the | |
166 | /// means to do. For that reason, the following example will not compile. | |
167 | /// | |
168 | /// ```compile_fail,E0277 | |
169 | /// trait TraitExample {} | |
170 | /// | |
171 | /// impl<'a> TraitExample for &'a str {} | |
92a42be0 | 172 | /// |
3b2f2976 XL |
173 | /// fn example_func<A: TraitExample>(example_arg: A) {} |
174 | /// | |
e74abb32 XL |
175 | /// let example_string = String::from("example_string"); |
176 | /// example_func(&example_string); | |
3b2f2976 XL |
177 | /// ``` |
178 | /// | |
179 | /// There are two options that would work instead. The first would be to | |
180 | /// change the line `example_func(&example_string);` to | |
181 | /// `example_func(example_string.as_str());`, using the method [`as_str()`] | |
182 | /// to explicitly extract the string slice containing the string. The second | |
183 | /// way changes `example_func(&example_string);` to | |
184 | /// `example_func(&*example_string);`. In this case we are dereferencing a | |
c295e0f8 | 185 | /// `String` to a [`str`], then referencing the [`str`] back to |
3b2f2976 XL |
186 | /// [`&str`]. The second way is more idiomatic, however both work to do the |
187 | /// conversion explicitly rather than relying on the implicit conversion. | |
92a42be0 SL |
188 | /// |
189 | /// # Representation | |
190 | /// | |
191 | /// A `String` is made up of three components: a pointer to some bytes, a | |
192 | /// length, and a capacity. The pointer points to an internal buffer `String` | |
193 | /// uses to store its data. The length is the number of bytes currently stored | |
194 | /// in the buffer, and the capacity is the size of the buffer in bytes. As such, | |
195 | /// the length will always be less than or equal to the capacity. | |
196 | /// | |
197 | /// This buffer is always stored on the heap. | |
198 | /// | |
cc61c64b | 199 | /// You can look at these with the [`as_ptr`], [`len`], and [`capacity`] |
92a42be0 SL |
200 | /// methods: |
201 | /// | |
202 | /// ``` | |
203 | /// use std::mem; | |
204 | /// | |
205 | /// let story = String::from("Once upon a time..."); | |
206 | /// | |
e74abb32 XL |
207 | // FIXME Update this when vec_into_raw_parts is stabilized |
208 | /// // Prevent automatically dropping the String's data | |
209 | /// let mut story = mem::ManuallyDrop::new(story); | |
210 | /// | |
211 | /// let ptr = story.as_mut_ptr(); | |
92a42be0 SL |
212 | /// let len = story.len(); |
213 | /// let capacity = story.capacity(); | |
214 | /// | |
a7813a04 | 215 | /// // story has nineteen bytes |
92a42be0 SL |
216 | /// assert_eq!(19, len); |
217 | /// | |
92a42be0 | 218 | /// // We can re-build a String out of ptr, len, and capacity. This is all |
7453a54e | 219 | /// // unsafe because we are responsible for making sure the components are |
92a42be0 | 220 | /// // valid: |
e74abb32 | 221 | /// let s = unsafe { String::from_raw_parts(ptr, len, capacity) } ; |
92a42be0 SL |
222 | /// |
223 | /// assert_eq!(String::from("Once upon a time..."), s); | |
224 | /// ``` | |
225 | /// | |
3dfed10e XL |
226 | /// [`as_ptr`]: str::as_ptr |
227 | /// [`len`]: String::len | |
228 | /// [`capacity`]: String::capacity | |
92a42be0 SL |
229 | /// |
230 | /// If a `String` has enough capacity, adding elements to it will not | |
231 | /// re-allocate. For example, consider this program: | |
232 | /// | |
233 | /// ``` | |
234 | /// let mut s = String::new(); | |
235 | /// | |
236 | /// println!("{}", s.capacity()); | |
237 | /// | |
238 | /// for _ in 0..5 { | |
239 | /// s.push_str("hello"); | |
240 | /// println!("{}", s.capacity()); | |
241 | /// } | |
242 | /// ``` | |
243 | /// | |
244 | /// This will output the following: | |
245 | /// | |
246 | /// ```text | |
247 | /// 0 | |
248 | /// 5 | |
249 | /// 10 | |
250 | /// 20 | |
251 | /// 20 | |
252 | /// 40 | |
253 | /// ``` | |
254 | /// | |
255 | /// At first, we have no memory allocated at all, but as we append to the | |
256 | /// string, it increases its capacity appropriately. If we instead use the | |
cc61c64b | 257 | /// [`with_capacity`] method to allocate the correct capacity initially: |
92a42be0 SL |
258 | /// |
259 | /// ``` | |
260 | /// let mut s = String::with_capacity(25); | |
261 | /// | |
262 | /// println!("{}", s.capacity()); | |
263 | /// | |
264 | /// for _ in 0..5 { | |
265 | /// s.push_str("hello"); | |
266 | /// println!("{}", s.capacity()); | |
267 | /// } | |
268 | /// ``` | |
269 | /// | |
3dfed10e | 270 | /// [`with_capacity`]: String::with_capacity |
92a42be0 SL |
271 | /// |
272 | /// We end up with a different output: | |
273 | /// | |
274 | /// ```text | |
275 | /// 25 | |
276 | /// 25 | |
277 | /// 25 | |
278 | /// 25 | |
279 | /// 25 | |
280 | /// 25 | |
281 | /// ``` | |
282 | /// | |
283 | /// Here, there's no need to allocate more memory inside the loop. | |
3b2f2976 | 284 | /// |
c295e0f8 XL |
285 | /// [str]: prim@str "str" |
286 | /// [`str`]: prim@str "str" | |
287 | /// [`&str`]: prim@str "&str" | |
288 | /// [Deref]: core::ops::Deref "ops::Deref" | |
289 | /// [`Deref`]: core::ops::Deref "ops::Deref" | |
3dfed10e | 290 | /// [`as_str()`]: String::as_str |
b039eaaf | 291 | #[derive(PartialOrd, Eq, Ord)] |
c295e0f8 | 292 | #[cfg_attr(not(test), rustc_diagnostic_item = "String")] |
85aaf69f | 293 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
294 | pub struct String { |
295 | vec: Vec<u8>, | |
296 | } | |
297 | ||
92a42be0 SL |
298 | /// A possible error value when converting a `String` from a UTF-8 byte vector. |
299 | /// | |
cc61c64b | 300 | /// This type is the error type for the [`from_utf8`] method on [`String`]. It |
92a42be0 | 301 | /// is designed in such a way to carefully avoid reallocations: the |
cc61c64b | 302 | /// [`into_bytes`] method will give back the byte vector that was used in the |
92a42be0 SL |
303 | /// conversion attempt. |
304 | /// | |
3dfed10e XL |
305 | /// [`from_utf8`]: String::from_utf8 |
306 | /// [`into_bytes`]: FromUtf8Error::into_bytes | |
92a42be0 SL |
307 | /// |
308 | /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may | |
309 | /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's | |
310 | /// an analogue to `FromUtf8Error`, and you can get one from a `FromUtf8Error` | |
cc61c64b | 311 | /// through the [`utf8_error`] method. |
92a42be0 | 312 | /// |
c295e0f8 XL |
313 | /// [`Utf8Error`]: str::Utf8Error "std::str::Utf8Error" |
314 | /// [`std::str`]: core::str "std::str" | |
315 | /// [`&str`]: prim@str "&str" | |
316 | /// [`utf8_error`]: FromUtf8Error::utf8_error | |
92a42be0 SL |
317 | /// |
318 | /// # Examples | |
319 | /// | |
320 | /// Basic usage: | |
321 | /// | |
322 | /// ``` | |
323 | /// // some invalid bytes, in a vector | |
324 | /// let bytes = vec![0, 159]; | |
325 | /// | |
326 | /// let value = String::from_utf8(bytes); | |
327 | /// | |
328 | /// assert!(value.is_err()); | |
329 | /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes()); | |
330 | /// ``` | |
85aaf69f | 331 | #[stable(feature = "rust1", since = "1.0.0")] |
17df50a5 XL |
332 | #[cfg_attr(not(no_global_oom_handling), derive(Clone))] |
333 | #[derive(Debug, PartialEq, Eq)] | |
1a4d82fc JJ |
334 | pub struct FromUtf8Error { |
335 | bytes: Vec<u8>, | |
336 | error: Utf8Error, | |
337 | } | |
338 | ||
92a42be0 SL |
339 | /// A possible error value when converting a `String` from a UTF-16 byte slice. |
340 | /// | |
cc61c64b | 341 | /// This type is the error type for the [`from_utf16`] method on [`String`]. |
92a42be0 | 342 | /// |
3dfed10e | 343 | /// [`from_utf16`]: String::from_utf16 |
92a42be0 SL |
344 | /// # Examples |
345 | /// | |
346 | /// Basic usage: | |
347 | /// | |
348 | /// ``` | |
349 | /// // 𝄞mu<invalid>ic | |
350 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, | |
351 | /// 0xD800, 0x0069, 0x0063]; | |
352 | /// | |
353 | /// assert!(String::from_utf16(v).is_err()); | |
354 | /// ``` | |
85aaf69f SL |
355 | #[stable(feature = "rust1", since = "1.0.0")] |
356 | #[derive(Debug)] | |
1a4d82fc JJ |
357 | pub struct FromUtf16Error(()); |
358 | ||
359 | impl String { | |
9cc50fc6 SL |
360 | /// Creates a new empty `String`. |
361 | /// | |
362 | /// Given that the `String` is empty, this will not allocate any initial | |
363 | /// buffer. While that means that this initial operation is very | |
0531ce1d | 364 | /// inexpensive, it may cause excessive allocation later when you add |
9cc50fc6 | 365 | /// data. If you have an idea of how much data the `String` will hold, |
cc61c64b | 366 | /// consider the [`with_capacity`] method to prevent excessive |
9cc50fc6 SL |
367 | /// re-allocation. |
368 | /// | |
3dfed10e | 369 | /// [`with_capacity`]: String::with_capacity |
1a4d82fc JJ |
370 | /// |
371 | /// # Examples | |
372 | /// | |
9cc50fc6 SL |
373 | /// Basic usage: |
374 | /// | |
1a4d82fc | 375 | /// ``` |
9cc50fc6 | 376 | /// let s = String::new(); |
1a4d82fc JJ |
377 | /// ``` |
378 | #[inline] | |
cdc7bbd5 | 379 | #[rustc_const_stable(feature = "const_string_new", since = "1.39.0")] |
85aaf69f | 380 | #[stable(feature = "rust1", since = "1.0.0")] |
c295e0f8 | 381 | #[must_use] |
94b46f34 | 382 | pub const fn new() -> String { |
92a42be0 | 383 | String { vec: Vec::new() } |
1a4d82fc JJ |
384 | } |
385 | ||
9cc50fc6 SL |
386 | /// Creates a new empty `String` with a particular capacity. |
387 | /// | |
388 | /// `String`s have an internal buffer to hold their data. The capacity is | |
cc61c64b | 389 | /// the length of that buffer, and can be queried with the [`capacity`] |
9cc50fc6 SL |
390 | /// method. This method creates an empty `String`, but one with an initial |
391 | /// buffer that can hold `capacity` bytes. This is useful when you may be | |
392 | /// appending a bunch of data to the `String`, reducing the number of | |
393 | /// reallocations it needs to do. | |
394 | /// | |
3dfed10e | 395 | /// [`capacity`]: String::capacity |
9cc50fc6 SL |
396 | /// |
397 | /// If the given capacity is `0`, no allocation will occur, and this method | |
cc61c64b | 398 | /// is identical to the [`new`] method. |
9cc50fc6 | 399 | /// |
3dfed10e | 400 | /// [`new`]: String::new |
1a4d82fc JJ |
401 | /// |
402 | /// # Examples | |
403 | /// | |
9cc50fc6 SL |
404 | /// Basic usage: |
405 | /// | |
1a4d82fc JJ |
406 | /// ``` |
407 | /// let mut s = String::with_capacity(10); | |
92a42be0 SL |
408 | /// |
409 | /// // The String contains no chars, even though it has capacity for more | |
410 | /// assert_eq!(s.len(), 0); | |
411 | /// | |
412 | /// // These are all done without reallocating... | |
413 | /// let cap = s.capacity(); | |
a1dfa0c6 | 414 | /// for _ in 0..10 { |
92a42be0 SL |
415 | /// s.push('a'); |
416 | /// } | |
417 | /// | |
418 | /// assert_eq!(s.capacity(), cap); | |
419 | /// | |
74b04a01 | 420 | /// // ...but this may make the string reallocate |
92a42be0 | 421 | /// s.push('a'); |
1a4d82fc | 422 | /// ``` |
17df50a5 | 423 | #[cfg(not(no_global_oom_handling))] |
1a4d82fc | 424 | #[inline] |
85aaf69f | 425 | #[stable(feature = "rust1", since = "1.0.0")] |
c295e0f8 | 426 | #[must_use] |
85aaf69f | 427 | pub fn with_capacity(capacity: usize) -> String { |
92a42be0 | 428 | String { vec: Vec::with_capacity(capacity) } |
1a4d82fc JJ |
429 | } |
430 | ||
c34b1796 AL |
431 | // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is |
432 | // required for this method definition, is not available. Since we don't | |
433 | // require this method for testing purposes, I'll just stub it | |
434 | // NB see the slice::hack module in slice.rs for more information | |
435 | #[inline] | |
436 | #[cfg(test)] | |
437 | pub fn from_str(_: &str) -> String { | |
438 | panic!("not available with cfg(test)"); | |
1a4d82fc JJ |
439 | } |
440 | ||
b039eaaf SL |
441 | /// Converts a vector of bytes to a `String`. |
442 | /// | |
e74abb32 | 443 | /// A string ([`String`]) is made of bytes ([`u8`]), and a vector of bytes |
9cc50fc6 | 444 | /// ([`Vec<u8>`]) is made of bytes, so this function converts between the |
b039eaaf SL |
445 | /// two. Not all byte slices are valid `String`s, however: `String` |
446 | /// requires that it is valid UTF-8. `from_utf8()` checks to ensure that | |
447 | /// the bytes are valid UTF-8, and then does the conversion. | |
448 | /// | |
449 | /// If you are sure that the byte slice is valid UTF-8, and you don't want | |
450 | /// to incur the overhead of the validity check, there is an unsafe version | |
cc61c64b | 451 | /// of this function, [`from_utf8_unchecked`], which has the same behavior |
9cc50fc6 | 452 | /// but skips the check. |
b039eaaf | 453 | /// |
b039eaaf SL |
454 | /// This method will take care to not copy the vector, for efficiency's |
455 | /// sake. | |
456 | /// | |
3b2f2976 | 457 | /// If you need a [`&str`] instead of a `String`, consider |
cc61c64b | 458 | /// [`str::from_utf8`]. |
b039eaaf | 459 | /// |
e74abb32 | 460 | /// The inverse of this method is [`into_bytes`]. |
8bb4bdeb | 461 | /// |
7453a54e | 462 | /// # Errors |
1a4d82fc | 463 | /// |
3b2f2976 | 464 | /// Returns [`Err`] if the slice is not UTF-8 with a description as to why the |
b039eaaf | 465 | /// provided bytes are not UTF-8. The vector you moved in is also included. |
1a4d82fc JJ |
466 | /// |
467 | /// # Examples | |
468 | /// | |
b039eaaf SL |
469 | /// Basic usage: |
470 | /// | |
c34b1796 | 471 | /// ``` |
b039eaaf SL |
472 | /// // some bytes, in a vector |
473 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
474 | /// | |
92a42be0 | 475 | /// // We know these bytes are valid, so we'll use `unwrap()`. |
b039eaaf SL |
476 | /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); |
477 | /// | |
478 | /// assert_eq!("💖", sparkle_heart); | |
479 | /// ``` | |
480 | /// | |
481 | /// Incorrect bytes: | |
482 | /// | |
1a4d82fc | 483 | /// ``` |
b039eaaf SL |
484 | /// // some invalid bytes, in a vector |
485 | /// let sparkle_heart = vec![0, 159, 146, 150]; | |
486 | /// | |
487 | /// assert!(String::from_utf8(sparkle_heart).is_err()); | |
488 | /// ``` | |
489 | /// | |
9cc50fc6 SL |
490 | /// See the docs for [`FromUtf8Error`] for more details on what you can do |
491 | /// with this error. | |
b039eaaf | 492 | /// |
3dfed10e | 493 | /// [`from_utf8_unchecked`]: String::from_utf8_unchecked |
c295e0f8 XL |
494 | /// [`Vec<u8>`]: crate::vec::Vec "Vec" |
495 | /// [`&str`]: prim@str "&str" | |
3dfed10e | 496 | /// [`into_bytes`]: String::into_bytes |
1a4d82fc | 497 | #[inline] |
85aaf69f | 498 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 499 | pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> { |
85aaf69f | 500 | match str::from_utf8(&vec) { |
a1dfa0c6 | 501 | Ok(..) => Ok(String { vec }), |
dfeec247 | 502 | Err(e) => Err(FromUtf8Error { bytes: vec, error: e }), |
1a4d82fc JJ |
503 | } |
504 | } | |
505 | ||
7453a54e | 506 | /// Converts a slice of bytes to a string, including invalid characters. |
b039eaaf | 507 | /// |
7453a54e SL |
508 | /// Strings are made of bytes ([`u8`]), and a slice of bytes |
509 | /// ([`&[u8]`][byteslice]) is made of bytes, so this function converts | |
510 | /// between the two. Not all byte slices are valid strings, however: strings | |
511 | /// are required to be valid UTF-8. During this conversion, | |
9cc50fc6 | 512 | /// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with |
b7449926 | 513 | /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], which looks like this: � |
b039eaaf | 514 | /// |
6a06907d | 515 | /// [byteslice]: prim@slice |
3dfed10e | 516 | /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER |
9cc50fc6 | 517 | /// |
b039eaaf SL |
518 | /// If you are sure that the byte slice is valid UTF-8, and you don't want |
519 | /// to incur the overhead of the conversion, there is an unsafe version | |
cc61c64b | 520 | /// of this function, [`from_utf8_unchecked`], which has the same behavior |
9cc50fc6 | 521 | /// but skips the checks. |
b039eaaf | 522 | /// |
3dfed10e | 523 | /// [`from_utf8_unchecked`]: String::from_utf8_unchecked |
b039eaaf | 524 | /// |
7453a54e SL |
525 | /// This function returns a [`Cow<'a, str>`]. If our byte slice is invalid |
526 | /// UTF-8, then we need to insert the replacement characters, which will | |
527 | /// change the size of the string, and hence, require a `String`. But if | |
528 | /// it's already valid UTF-8, we don't need a new allocation. This return | |
529 | /// type allows us to handle both cases. | |
b039eaaf | 530 | /// |
c295e0f8 | 531 | /// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow" |
1a4d82fc JJ |
532 | /// |
533 | /// # Examples | |
534 | /// | |
b039eaaf SL |
535 | /// Basic usage: |
536 | /// | |
c34b1796 | 537 | /// ``` |
b039eaaf SL |
538 | /// // some bytes, in a vector |
539 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
540 | /// | |
7453a54e | 541 | /// let sparkle_heart = String::from_utf8_lossy(&sparkle_heart); |
b039eaaf SL |
542 | /// |
543 | /// assert_eq!("💖", sparkle_heart); | |
544 | /// ``` | |
545 | /// | |
546 | /// Incorrect bytes: | |
547 | /// | |
548 | /// ``` | |
549 | /// // some invalid bytes | |
1a4d82fc JJ |
550 | /// let input = b"Hello \xF0\x90\x80World"; |
551 | /// let output = String::from_utf8_lossy(input); | |
b039eaaf SL |
552 | /// |
553 | /// assert_eq!("Hello �World", output); | |
1a4d82fc | 554 | /// ``` |
3c0e092e | 555 | #[must_use] |
17df50a5 | 556 | #[cfg(not(no_global_oom_handling))] |
85aaf69f | 557 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 558 | pub fn from_utf8_lossy(v: &[u8]) -> Cow<'_, str> { |
041b39d2 | 559 | let mut iter = lossy::Utf8Lossy::from_bytes(v).chunks(); |
1a4d82fc | 560 | |
a2a8927a | 561 | let first_valid = if let Some(chunk) = iter.next() { |
041b39d2 | 562 | let lossy::Utf8LossyChunk { valid, broken } = chunk; |
a2a8927a XL |
563 | if broken.is_empty() { |
564 | debug_assert_eq!(valid.len(), v.len()); | |
041b39d2 XL |
565 | return Cow::Borrowed(valid); |
566 | } | |
a2a8927a | 567 | valid |
041b39d2 XL |
568 | } else { |
569 | return Cow::Borrowed(""); | |
570 | }; | |
1a4d82fc | 571 | |
0731742a | 572 | const REPLACEMENT: &str = "\u{FFFD}"; |
1a4d82fc | 573 | |
041b39d2 XL |
574 | let mut res = String::with_capacity(v.len()); |
575 | res.push_str(first_valid); | |
a2a8927a | 576 | res.push_str(REPLACEMENT); |
1a4d82fc | 577 | |
041b39d2 XL |
578 | for lossy::Utf8LossyChunk { valid, broken } in iter { |
579 | res.push_str(valid); | |
580 | if !broken.is_empty() { | |
581 | res.push_str(REPLACEMENT); | |
1a4d82fc JJ |
582 | } |
583 | } | |
041b39d2 | 584 | |
1a4d82fc JJ |
585 | Cow::Owned(res) |
586 | } | |
587 | ||
29967ef6 | 588 | /// Decode a UTF-16–encoded vector `v` into a `String`, returning [`Err`] |
1a4d82fc JJ |
589 | /// if `v` contains any invalid data. |
590 | /// | |
591 | /// # Examples | |
592 | /// | |
9cc50fc6 SL |
593 | /// Basic usage: |
594 | /// | |
c34b1796 | 595 | /// ``` |
1a4d82fc | 596 | /// // 𝄞music |
92a42be0 SL |
597 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, |
598 | /// 0x0073, 0x0069, 0x0063]; | |
9cc50fc6 SL |
599 | /// assert_eq!(String::from("𝄞music"), |
600 | /// String::from_utf16(v).unwrap()); | |
1a4d82fc JJ |
601 | /// |
602 | /// // 𝄞mu<invalid>ic | |
92a42be0 SL |
603 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, |
604 | /// 0xD800, 0x0069, 0x0063]; | |
1a4d82fc JJ |
605 | /// assert!(String::from_utf16(v).is_err()); |
606 | /// ``` | |
17df50a5 | 607 | #[cfg(not(no_global_oom_handling))] |
85aaf69f | 608 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 609 | pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error> { |
a1dfa0c6 XL |
610 | // This isn't done via collect::<Result<_, _>>() for performance reasons. |
611 | // FIXME: the function can be simplified again when #48994 is closed. | |
612 | let mut ret = String::with_capacity(v.len()); | |
613 | for c in decode_utf16(v.iter().cloned()) { | |
614 | if let Ok(c) = c { | |
615 | ret.push(c); | |
616 | } else { | |
617 | return Err(FromUtf16Error(())); | |
618 | } | |
619 | } | |
620 | Ok(ret) | |
1a4d82fc JJ |
621 | } |
622 | ||
29967ef6 | 623 | /// Decode a UTF-16–encoded slice `v` into a `String`, replacing |
b7449926 | 624 | /// invalid data with [the replacement character (`U+FFFD`)][U+FFFD]. |
1a4d82fc | 625 | /// |
ea8adc8c XL |
626 | /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`], |
627 | /// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8 | |
628 | /// conversion requires a memory allocation. | |
629 | /// | |
3dfed10e | 630 | /// [`from_utf8_lossy`]: String::from_utf8_lossy |
c295e0f8 | 631 | /// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow" |
3dfed10e | 632 | /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER |
ea8adc8c | 633 | /// |
1a4d82fc JJ |
634 | /// # Examples |
635 | /// | |
9cc50fc6 SL |
636 | /// Basic usage: |
637 | /// | |
c34b1796 | 638 | /// ``` |
1a4d82fc JJ |
639 | /// // 𝄞mus<invalid>ic<invalid> |
640 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, | |
641 | /// 0x0073, 0xDD1E, 0x0069, 0x0063, | |
642 | /// 0xD834]; | |
643 | /// | |
9cc50fc6 SL |
644 | /// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"), |
645 | /// String::from_utf16_lossy(v)); | |
1a4d82fc | 646 | /// ``` |
17df50a5 | 647 | #[cfg(not(no_global_oom_handling))] |
3c0e092e | 648 | #[must_use] |
85aaf69f SL |
649 | #[inline] |
650 | #[stable(feature = "rust1", since = "1.0.0")] | |
1a4d82fc | 651 | pub fn from_utf16_lossy(v: &[u16]) -> String { |
e9174d1e | 652 | decode_utf16(v.iter().cloned()).map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)).collect() |
1a4d82fc JJ |
653 | } |
654 | ||
e74abb32 XL |
655 | /// Decomposes a `String` into its raw components. |
656 | /// | |
657 | /// Returns the raw pointer to the underlying data, the length of | |
658 | /// the string (in bytes), and the allocated capacity of the data | |
659 | /// (in bytes). These are the same arguments in the same order as | |
660 | /// the arguments to [`from_raw_parts`]. | |
661 | /// | |
662 | /// After calling this function, the caller is responsible for the | |
663 | /// memory previously managed by the `String`. The only way to do | |
664 | /// this is to convert the raw pointer, length, and capacity back | |
665 | /// into a `String` with the [`from_raw_parts`] function, allowing | |
666 | /// the destructor to perform the cleanup. | |
667 | /// | |
3dfed10e | 668 | /// [`from_raw_parts`]: String::from_raw_parts |
e74abb32 XL |
669 | /// |
670 | /// # Examples | |
671 | /// | |
672 | /// ``` | |
673 | /// #![feature(vec_into_raw_parts)] | |
674 | /// let s = String::from("hello"); | |
675 | /// | |
676 | /// let (ptr, len, cap) = s.into_raw_parts(); | |
677 | /// | |
678 | /// let rebuilt = unsafe { String::from_raw_parts(ptr, len, cap) }; | |
679 | /// assert_eq!(rebuilt, "hello"); | |
680 | /// ``` | |
c295e0f8 | 681 | #[must_use = "`self` will be dropped if the result is not used"] |
e74abb32 XL |
682 | #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] |
683 | pub fn into_raw_parts(self) -> (*mut u8, usize, usize) { | |
684 | self.vec.into_raw_parts() | |
685 | } | |
686 | ||
1a4d82fc JJ |
687 | /// Creates a new `String` from a length, capacity, and pointer. |
688 | /// | |
b039eaaf | 689 | /// # Safety |
c1a9b12d | 690 | /// |
9cc50fc6 SL |
691 | /// This is highly unsafe, due to the number of invariants that aren't |
692 | /// checked: | |
693 | /// | |
3dfed10e | 694 | /// * The memory at `buf` needs to have been previously allocated by the |
60c5eb7d | 695 | /// same allocator the standard library uses, with a required alignment of exactly 1. |
9cc50fc6 SL |
696 | /// * `length` needs to be less than or equal to `capacity`. |
697 | /// * `capacity` needs to be the correct value. | |
3dfed10e | 698 | /// * The first `length` bytes at `buf` need to be valid UTF-8. |
9cc50fc6 SL |
699 | /// |
700 | /// Violating these may cause problems like corrupting the allocator's | |
3b2f2976 | 701 | /// internal data structures. |
9cc50fc6 | 702 | /// |
3dfed10e | 703 | /// The ownership of `buf` is effectively transferred to the |
5bcae85e SL |
704 | /// `String` which may then deallocate, reallocate or change the |
705 | /// contents of memory pointed to by the pointer at will. Ensure | |
706 | /// that nothing else uses the pointer after calling this | |
707 | /// function. | |
708 | /// | |
9cc50fc6 SL |
709 | /// # Examples |
710 | /// | |
711 | /// Basic usage: | |
712 | /// | |
713 | /// ``` | |
714 | /// use std::mem; | |
715 | /// | |
716 | /// unsafe { | |
717 | /// let s = String::from("hello"); | |
e74abb32 XL |
718 | /// |
719 | // FIXME Update this when vec_into_raw_parts is stabilized | |
720 | /// // Prevent automatically dropping the String's data | |
721 | /// let mut s = mem::ManuallyDrop::new(s); | |
722 | /// | |
723 | /// let ptr = s.as_mut_ptr(); | |
9cc50fc6 SL |
724 | /// let len = s.len(); |
725 | /// let capacity = s.capacity(); | |
726 | /// | |
e74abb32 | 727 | /// let s = String::from_raw_parts(ptr, len, capacity); |
c34b1796 | 728 | /// |
9cc50fc6 SL |
729 | /// assert_eq!(String::from("hello"), s); |
730 | /// } | |
731 | /// ``` | |
1a4d82fc | 732 | #[inline] |
85aaf69f SL |
733 | #[stable(feature = "rust1", since = "1.0.0")] |
734 | pub unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String { | |
f035d41b | 735 | unsafe { String { vec: Vec::from_raw_parts(buf, length, capacity) } } |
1a4d82fc JJ |
736 | } |
737 | ||
b039eaaf SL |
738 | /// Converts a vector of bytes to a `String` without checking that the |
739 | /// string contains valid UTF-8. | |
740 | /// | |
cc61c64b | 741 | /// See the safe version, [`from_utf8`], for more details. |
b039eaaf | 742 | /// |
3dfed10e | 743 | /// [`from_utf8`]: String::from_utf8 |
b039eaaf SL |
744 | /// |
745 | /// # Safety | |
746 | /// | |
9cc50fc6 SL |
747 | /// This function is unsafe because it does not check that the bytes passed |
748 | /// to it are valid UTF-8. If this constraint is violated, it may cause | |
749 | /// memory unsafety issues with future users of the `String`, as the rest of | |
750 | /// the standard library assumes that `String`s are valid UTF-8. | |
b039eaaf SL |
751 | /// |
752 | /// # Examples | |
753 | /// | |
754 | /// Basic usage: | |
755 | /// | |
756 | /// ``` | |
757 | /// // some bytes, in a vector | |
758 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
759 | /// | |
760 | /// let sparkle_heart = unsafe { | |
761 | /// String::from_utf8_unchecked(sparkle_heart) | |
762 | /// }; | |
763 | /// | |
764 | /// assert_eq!("💖", sparkle_heart); | |
765 | /// ``` | |
1a4d82fc | 766 | #[inline] |
c295e0f8 | 767 | #[must_use] |
85aaf69f | 768 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
769 | pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String { |
770 | String { vec: bytes } | |
771 | } | |
772 | ||
9cc50fc6 SL |
773 | /// Converts a `String` into a byte vector. |
774 | /// | |
775 | /// This consumes the `String`, so we do not need to copy its contents. | |
1a4d82fc JJ |
776 | /// |
777 | /// # Examples | |
778 | /// | |
9cc50fc6 SL |
779 | /// Basic usage: |
780 | /// | |
1a4d82fc | 781 | /// ``` |
62682a34 | 782 | /// let s = String::from("hello"); |
1a4d82fc | 783 | /// let bytes = s.into_bytes(); |
9cc50fc6 SL |
784 | /// |
785 | /// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]); | |
1a4d82fc JJ |
786 | /// ``` |
787 | #[inline] | |
c295e0f8 | 788 | #[must_use = "`self` will be dropped if the result is not used"] |
85aaf69f | 789 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
790 | pub fn into_bytes(self) -> Vec<u8> { |
791 | self.vec | |
792 | } | |
793 | ||
b7449926 | 794 | /// Extracts a string slice containing the entire `String`. |
ea8adc8c XL |
795 | /// |
796 | /// # Examples | |
797 | /// | |
798 | /// Basic usage: | |
799 | /// | |
800 | /// ``` | |
801 | /// let s = String::from("foo"); | |
802 | /// | |
803 | /// assert_eq!("foo", s.as_str()); | |
804 | /// ``` | |
c34b1796 | 805 | #[inline] |
c295e0f8 | 806 | #[must_use] |
9cc50fc6 | 807 | #[stable(feature = "string_as_str", since = "1.7.0")] |
c34b1796 AL |
808 | pub fn as_str(&self) -> &str { |
809 | self | |
810 | } | |
811 | ||
ea8adc8c XL |
812 | /// Converts a `String` into a mutable string slice. |
813 | /// | |
814 | /// # Examples | |
815 | /// | |
816 | /// Basic usage: | |
817 | /// | |
818 | /// ``` | |
ea8adc8c XL |
819 | /// let mut s = String::from("foobar"); |
820 | /// let s_mut_str = s.as_mut_str(); | |
821 | /// | |
822 | /// s_mut_str.make_ascii_uppercase(); | |
823 | /// | |
824 | /// assert_eq!("FOOBAR", s_mut_str); | |
825 | /// ``` | |
9cc50fc6 | 826 | #[inline] |
c295e0f8 | 827 | #[must_use] |
9cc50fc6 SL |
828 | #[stable(feature = "string_as_str", since = "1.7.0")] |
829 | pub fn as_mut_str(&mut self) -> &mut str { | |
830 | self | |
831 | } | |
832 | ||
833 | /// Appends a given string slice onto the end of this `String`. | |
1a4d82fc JJ |
834 | /// |
835 | /// # Examples | |
836 | /// | |
9cc50fc6 SL |
837 | /// Basic usage: |
838 | /// | |
1a4d82fc | 839 | /// ``` |
62682a34 | 840 | /// let mut s = String::from("foo"); |
9cc50fc6 | 841 | /// |
1a4d82fc | 842 | /// s.push_str("bar"); |
9cc50fc6 SL |
843 | /// |
844 | /// assert_eq!("foobar", s); | |
1a4d82fc | 845 | /// ``` |
17df50a5 | 846 | #[cfg(not(no_global_oom_handling))] |
1a4d82fc | 847 | #[inline] |
85aaf69f | 848 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 849 | pub fn push_str(&mut self, string: &str) { |
92a42be0 | 850 | self.vec.extend_from_slice(string.as_bytes()) |
1a4d82fc JJ |
851 | } |
852 | ||
17df50a5 XL |
853 | /// Copies elements from `src` range to the end of the string. |
854 | /// | |
855 | /// ## Panics | |
856 | /// | |
857 | /// Panics if the starting point or end point do not lie on a [`char`] | |
858 | /// boundary, or if they're out of bounds. | |
859 | /// | |
860 | /// ## Examples | |
861 | /// | |
862 | /// ``` | |
863 | /// #![feature(string_extend_from_within)] | |
864 | /// let mut string = String::from("abcde"); | |
865 | /// | |
866 | /// string.extend_from_within(2..); | |
867 | /// assert_eq!(string, "abcdecde"); | |
868 | /// | |
869 | /// string.extend_from_within(..2); | |
870 | /// assert_eq!(string, "abcdecdeab"); | |
871 | /// | |
872 | /// string.extend_from_within(4..8); | |
873 | /// assert_eq!(string, "abcdecdeabecde"); | |
874 | /// ``` | |
875 | #[cfg(not(no_global_oom_handling))] | |
876 | #[unstable(feature = "string_extend_from_within", issue = "none")] | |
877 | pub fn extend_from_within<R>(&mut self, src: R) | |
878 | where | |
879 | R: RangeBounds<usize>, | |
880 | { | |
881 | let src @ Range { start, end } = slice::range(src, ..self.len()); | |
882 | ||
883 | assert!(self.is_char_boundary(start)); | |
884 | assert!(self.is_char_boundary(end)); | |
885 | ||
886 | self.vec.extend_from_within(src); | |
887 | } | |
888 | ||
9cc50fc6 | 889 | /// Returns this `String`'s capacity, in bytes. |
1a4d82fc JJ |
890 | /// |
891 | /// # Examples | |
892 | /// | |
9cc50fc6 SL |
893 | /// Basic usage: |
894 | /// | |
1a4d82fc JJ |
895 | /// ``` |
896 | /// let s = String::with_capacity(10); | |
9cc50fc6 | 897 | /// |
1a4d82fc JJ |
898 | /// assert!(s.capacity() >= 10); |
899 | /// ``` | |
900 | #[inline] | |
3c0e092e | 901 | #[must_use] |
85aaf69f SL |
902 | #[stable(feature = "rust1", since = "1.0.0")] |
903 | pub fn capacity(&self) -> usize { | |
1a4d82fc JJ |
904 | self.vec.capacity() |
905 | } | |
906 | ||
9cc50fc6 SL |
907 | /// Ensures that this `String`'s capacity is at least `additional` bytes |
908 | /// larger than its length. | |
909 | /// | |
910 | /// The capacity may be increased by more than `additional` bytes if it | |
911 | /// chooses, to prevent frequent reallocations. | |
912 | /// | |
cc61c64b | 913 | /// If you do not want this "at least" behavior, see the [`reserve_exact`] |
9cc50fc6 SL |
914 | /// method. |
915 | /// | |
1a4d82fc JJ |
916 | /// # Panics |
917 | /// | |
3b2f2976 XL |
918 | /// Panics if the new capacity overflows [`usize`]. |
919 | /// | |
3dfed10e | 920 | /// [`reserve_exact`]: String::reserve_exact |
1a4d82fc JJ |
921 | /// |
922 | /// # Examples | |
923 | /// | |
9cc50fc6 SL |
924 | /// Basic usage: |
925 | /// | |
1a4d82fc JJ |
926 | /// ``` |
927 | /// let mut s = String::new(); | |
9cc50fc6 | 928 | /// |
1a4d82fc | 929 | /// s.reserve(10); |
9cc50fc6 | 930 | /// |
1a4d82fc JJ |
931 | /// assert!(s.capacity() >= 10); |
932 | /// ``` | |
9cc50fc6 | 933 | /// |
94222f64 | 934 | /// This might not actually increase the capacity: |
9cc50fc6 SL |
935 | /// |
936 | /// ``` | |
937 | /// let mut s = String::with_capacity(10); | |
938 | /// s.push('a'); | |
939 | /// s.push('b'); | |
940 | /// | |
941 | /// // s now has a length of 2 and a capacity of 10 | |
942 | /// assert_eq!(2, s.len()); | |
943 | /// assert_eq!(10, s.capacity()); | |
944 | /// | |
945 | /// // Since we already have an extra 8 capacity, calling this... | |
946 | /// s.reserve(8); | |
947 | /// | |
948 | /// // ... doesn't actually increase. | |
949 | /// assert_eq!(10, s.capacity()); | |
950 | /// ``` | |
17df50a5 | 951 | #[cfg(not(no_global_oom_handling))] |
1a4d82fc | 952 | #[inline] |
85aaf69f SL |
953 | #[stable(feature = "rust1", since = "1.0.0")] |
954 | pub fn reserve(&mut self, additional: usize) { | |
1a4d82fc JJ |
955 | self.vec.reserve(additional) |
956 | } | |
957 | ||
9cc50fc6 SL |
958 | /// Ensures that this `String`'s capacity is `additional` bytes |
959 | /// larger than its length. | |
1a4d82fc | 960 | /// |
cc61c64b | 961 | /// Consider using the [`reserve`] method unless you absolutely know |
9cc50fc6 SL |
962 | /// better than the allocator. |
963 | /// | |
3dfed10e | 964 | /// [`reserve`]: String::reserve |
1a4d82fc JJ |
965 | /// |
966 | /// # Panics | |
967 | /// | |
85aaf69f | 968 | /// Panics if the new capacity overflows `usize`. |
1a4d82fc JJ |
969 | /// |
970 | /// # Examples | |
971 | /// | |
9cc50fc6 SL |
972 | /// Basic usage: |
973 | /// | |
1a4d82fc JJ |
974 | /// ``` |
975 | /// let mut s = String::new(); | |
9cc50fc6 | 976 | /// |
62682a34 | 977 | /// s.reserve_exact(10); |
9cc50fc6 | 978 | /// |
1a4d82fc JJ |
979 | /// assert!(s.capacity() >= 10); |
980 | /// ``` | |
9cc50fc6 | 981 | /// |
94222f64 | 982 | /// This might not actually increase the capacity: |
9cc50fc6 SL |
983 | /// |
984 | /// ``` | |
985 | /// let mut s = String::with_capacity(10); | |
986 | /// s.push('a'); | |
987 | /// s.push('b'); | |
988 | /// | |
989 | /// // s now has a length of 2 and a capacity of 10 | |
990 | /// assert_eq!(2, s.len()); | |
991 | /// assert_eq!(10, s.capacity()); | |
992 | /// | |
993 | /// // Since we already have an extra 8 capacity, calling this... | |
994 | /// s.reserve_exact(8); | |
995 | /// | |
996 | /// // ... doesn't actually increase. | |
997 | /// assert_eq!(10, s.capacity()); | |
998 | /// ``` | |
17df50a5 | 999 | #[cfg(not(no_global_oom_handling))] |
1a4d82fc | 1000 | #[inline] |
85aaf69f SL |
1001 | #[stable(feature = "rust1", since = "1.0.0")] |
1002 | pub fn reserve_exact(&mut self, additional: usize) { | |
1a4d82fc JJ |
1003 | self.vec.reserve_exact(additional) |
1004 | } | |
1005 | ||
0531ce1d XL |
1006 | /// Tries to reserve capacity for at least `additional` more elements to be inserted |
1007 | /// in the given `String`. The collection may reserve more space to avoid | |
1008 | /// frequent reallocations. After calling `reserve`, capacity will be | |
1009 | /// greater than or equal to `self.len() + additional`. Does nothing if | |
1010 | /// capacity is already sufficient. | |
1011 | /// | |
1012 | /// # Errors | |
1013 | /// | |
1014 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
1015 | /// is returned. | |
1016 | /// | |
1017 | /// # Examples | |
1018 | /// | |
1019 | /// ``` | |
e1599b0c | 1020 | /// use std::collections::TryReserveError; |
0531ce1d | 1021 | /// |
e1599b0c | 1022 | /// fn process_data(data: &str) -> Result<String, TryReserveError> { |
0531ce1d XL |
1023 | /// let mut output = String::new(); |
1024 | /// | |
1025 | /// // Pre-reserve the memory, exiting if we can't | |
1026 | /// output.try_reserve(data.len())?; | |
1027 | /// | |
1028 | /// // Now we know this can't OOM in the middle of our complex work | |
1029 | /// output.push_str(data); | |
1030 | /// | |
1031 | /// Ok(output) | |
1032 | /// } | |
1033 | /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?"); | |
1034 | /// ``` | |
c295e0f8 | 1035 | #[stable(feature = "try_reserve", since = "1.57.0")] |
e1599b0c | 1036 | pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { |
0531ce1d XL |
1037 | self.vec.try_reserve(additional) |
1038 | } | |
1039 | ||
5869c6ff | 1040 | /// Tries to reserve the minimum capacity for exactly `additional` more elements to |
0531ce1d XL |
1041 | /// be inserted in the given `String`. After calling `reserve_exact`, |
1042 | /// capacity will be greater than or equal to `self.len() + additional`. | |
1043 | /// Does nothing if the capacity is already sufficient. | |
1044 | /// | |
1045 | /// Note that the allocator may give the collection more space than it | |
9fa01778 | 1046 | /// requests. Therefore, capacity can not be relied upon to be precisely |
a2a8927a | 1047 | /// minimal. Prefer [`try_reserve`] if future insertions are expected. |
94222f64 | 1048 | /// |
a2a8927a | 1049 | /// [`try_reserve`]: String::try_reserve |
0531ce1d XL |
1050 | /// |
1051 | /// # Errors | |
1052 | /// | |
1053 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
1054 | /// is returned. | |
1055 | /// | |
1056 | /// # Examples | |
1057 | /// | |
1058 | /// ``` | |
e1599b0c | 1059 | /// use std::collections::TryReserveError; |
0531ce1d | 1060 | /// |
e1599b0c | 1061 | /// fn process_data(data: &str) -> Result<String, TryReserveError> { |
0531ce1d XL |
1062 | /// let mut output = String::new(); |
1063 | /// | |
1064 | /// // Pre-reserve the memory, exiting if we can't | |
a2a8927a | 1065 | /// output.try_reserve_exact(data.len())?; |
0531ce1d XL |
1066 | /// |
1067 | /// // Now we know this can't OOM in the middle of our complex work | |
1068 | /// output.push_str(data); | |
1069 | /// | |
1070 | /// Ok(output) | |
1071 | /// } | |
1072 | /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?"); | |
1073 | /// ``` | |
c295e0f8 | 1074 | #[stable(feature = "try_reserve", since = "1.57.0")] |
dfeec247 | 1075 | pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { |
0531ce1d XL |
1076 | self.vec.try_reserve_exact(additional) |
1077 | } | |
1078 | ||
9cc50fc6 | 1079 | /// Shrinks the capacity of this `String` to match its length. |
1a4d82fc JJ |
1080 | /// |
1081 | /// # Examples | |
1082 | /// | |
9cc50fc6 SL |
1083 | /// Basic usage: |
1084 | /// | |
1a4d82fc | 1085 | /// ``` |
62682a34 | 1086 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1087 | /// |
1a4d82fc JJ |
1088 | /// s.reserve(100); |
1089 | /// assert!(s.capacity() >= 100); | |
9cc50fc6 | 1090 | /// |
1a4d82fc | 1091 | /// s.shrink_to_fit(); |
9cc50fc6 | 1092 | /// assert_eq!(3, s.capacity()); |
1a4d82fc | 1093 | /// ``` |
17df50a5 | 1094 | #[cfg(not(no_global_oom_handling))] |
1a4d82fc | 1095 | #[inline] |
85aaf69f | 1096 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1097 | pub fn shrink_to_fit(&mut self) { |
1098 | self.vec.shrink_to_fit() | |
1099 | } | |
1100 | ||
0531ce1d XL |
1101 | /// Shrinks the capacity of this `String` with a lower bound. |
1102 | /// | |
1103 | /// The capacity will remain at least as large as both the length | |
1104 | /// and the supplied value. | |
1105 | /// | |
5869c6ff | 1106 | /// If the current capacity is less than the lower limit, this is a no-op. |
0531ce1d XL |
1107 | /// |
1108 | /// # Examples | |
1109 | /// | |
1110 | /// ``` | |
0531ce1d XL |
1111 | /// let mut s = String::from("foo"); |
1112 | /// | |
1113 | /// s.reserve(100); | |
1114 | /// assert!(s.capacity() >= 100); | |
1115 | /// | |
1116 | /// s.shrink_to(10); | |
1117 | /// assert!(s.capacity() >= 10); | |
1118 | /// s.shrink_to(0); | |
1119 | /// assert!(s.capacity() >= 3); | |
1120 | /// ``` | |
17df50a5 | 1121 | #[cfg(not(no_global_oom_handling))] |
0531ce1d | 1122 | #[inline] |
94222f64 | 1123 | #[stable(feature = "shrink_to", since = "1.56.0")] |
0531ce1d XL |
1124 | pub fn shrink_to(&mut self, min_capacity: usize) { |
1125 | self.vec.shrink_to(min_capacity) | |
1126 | } | |
1127 | ||
3b2f2976 XL |
1128 | /// Appends the given [`char`] to the end of this `String`. |
1129 | /// | |
1a4d82fc JJ |
1130 | /// # Examples |
1131 | /// | |
9cc50fc6 SL |
1132 | /// Basic usage: |
1133 | /// | |
1a4d82fc | 1134 | /// ``` |
62682a34 | 1135 | /// let mut s = String::from("abc"); |
9cc50fc6 | 1136 | /// |
1a4d82fc JJ |
1137 | /// s.push('1'); |
1138 | /// s.push('2'); | |
1139 | /// s.push('3'); | |
9cc50fc6 SL |
1140 | /// |
1141 | /// assert_eq!("abc123", s); | |
1a4d82fc | 1142 | /// ``` |
17df50a5 | 1143 | #[cfg(not(no_global_oom_handling))] |
1a4d82fc | 1144 | #[inline] |
85aaf69f | 1145 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1146 | pub fn push(&mut self, ch: char) { |
62682a34 SL |
1147 | match ch.len_utf8() { |
1148 | 1 => self.vec.push(ch as u8), | |
32a655c1 | 1149 | _ => self.vec.extend_from_slice(ch.encode_utf8(&mut [0; 4]).as_bytes()), |
1a4d82fc JJ |
1150 | } |
1151 | } | |
1152 | ||
9cc50fc6 | 1153 | /// Returns a byte slice of this `String`'s contents. |
1a4d82fc | 1154 | /// |
8bb4bdeb XL |
1155 | /// The inverse of this method is [`from_utf8`]. |
1156 | /// | |
3dfed10e | 1157 | /// [`from_utf8`]: String::from_utf8 |
8bb4bdeb | 1158 | /// |
1a4d82fc JJ |
1159 | /// # Examples |
1160 | /// | |
9cc50fc6 SL |
1161 | /// Basic usage: |
1162 | /// | |
1a4d82fc | 1163 | /// ``` |
62682a34 | 1164 | /// let s = String::from("hello"); |
9cc50fc6 SL |
1165 | /// |
1166 | /// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes()); | |
1a4d82fc JJ |
1167 | /// ``` |
1168 | #[inline] | |
c295e0f8 | 1169 | #[must_use] |
85aaf69f SL |
1170 | #[stable(feature = "rust1", since = "1.0.0")] |
1171 | pub fn as_bytes(&self) -> &[u8] { | |
1172 | &self.vec | |
1a4d82fc JJ |
1173 | } |
1174 | ||
9cc50fc6 | 1175 | /// Shortens this `String` to the specified length. |
1a4d82fc | 1176 | /// |
a7813a04 XL |
1177 | /// If `new_len` is greater than the string's current length, this has no |
1178 | /// effect. | |
1179 | /// | |
8bb4bdeb XL |
1180 | /// Note that this method has no effect on the allocated capacity |
1181 | /// of the string | |
1182 | /// | |
1a4d82fc JJ |
1183 | /// # Panics |
1184 | /// | |
a7813a04 | 1185 | /// Panics if `new_len` does not lie on a [`char`] boundary. |
9cc50fc6 | 1186 | /// |
1a4d82fc JJ |
1187 | /// # Examples |
1188 | /// | |
9cc50fc6 SL |
1189 | /// Basic usage: |
1190 | /// | |
1a4d82fc | 1191 | /// ``` |
62682a34 | 1192 | /// let mut s = String::from("hello"); |
9cc50fc6 | 1193 | /// |
1a4d82fc | 1194 | /// s.truncate(2); |
9cc50fc6 SL |
1195 | /// |
1196 | /// assert_eq!("he", s); | |
1a4d82fc JJ |
1197 | /// ``` |
1198 | #[inline] | |
85aaf69f SL |
1199 | #[stable(feature = "rust1", since = "1.0.0")] |
1200 | pub fn truncate(&mut self, new_len: usize) { | |
a7813a04 XL |
1201 | if new_len <= self.len() { |
1202 | assert!(self.is_char_boundary(new_len)); | |
1203 | self.vec.truncate(new_len) | |
1204 | } | |
1a4d82fc JJ |
1205 | } |
1206 | ||
1207 | /// Removes the last character from the string buffer and returns it. | |
9cc50fc6 | 1208 | /// |
3b2f2976 XL |
1209 | /// Returns [`None`] if this `String` is empty. |
1210 | /// | |
1a4d82fc JJ |
1211 | /// # Examples |
1212 | /// | |
9cc50fc6 SL |
1213 | /// Basic usage: |
1214 | /// | |
1a4d82fc | 1215 | /// ``` |
62682a34 | 1216 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1217 | /// |
1a4d82fc JJ |
1218 | /// assert_eq!(s.pop(), Some('o')); |
1219 | /// assert_eq!(s.pop(), Some('o')); | |
1220 | /// assert_eq!(s.pop(), Some('f')); | |
9cc50fc6 | 1221 | /// |
1a4d82fc JJ |
1222 | /// assert_eq!(s.pop(), None); |
1223 | /// ``` | |
1224 | #[inline] | |
85aaf69f | 1225 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1226 | pub fn pop(&mut self) -> Option<char> { |
ff7c6d11 | 1227 | let ch = self.chars().rev().next()?; |
54a0048b | 1228 | let newlen = self.len() - ch.len_utf8(); |
1a4d82fc | 1229 | unsafe { |
54a0048b | 1230 | self.vec.set_len(newlen); |
1a4d82fc JJ |
1231 | } |
1232 | Some(ch) | |
1233 | } | |
1234 | ||
3b2f2976 | 1235 | /// Removes a [`char`] from this `String` at a byte position and returns it. |
1a4d82fc | 1236 | /// |
3dfed10e | 1237 | /// This is an *O*(*n*) operation, as it requires copying every element in the |
1a4d82fc JJ |
1238 | /// buffer. |
1239 | /// | |
1240 | /// # Panics | |
1241 | /// | |
9cc50fc6 SL |
1242 | /// Panics if `idx` is larger than or equal to the `String`'s length, |
1243 | /// or if it does not lie on a [`char`] boundary. | |
1244 | /// | |
1a4d82fc JJ |
1245 | /// # Examples |
1246 | /// | |
9cc50fc6 SL |
1247 | /// Basic usage: |
1248 | /// | |
1a4d82fc | 1249 | /// ``` |
62682a34 | 1250 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1251 | /// |
1a4d82fc JJ |
1252 | /// assert_eq!(s.remove(0), 'f'); |
1253 | /// assert_eq!(s.remove(1), 'o'); | |
1254 | /// assert_eq!(s.remove(0), 'o'); | |
1255 | /// ``` | |
85aaf69f SL |
1256 | #[inline] |
1257 | #[stable(feature = "rust1", since = "1.0.0")] | |
1258 | pub fn remove(&mut self, idx: usize) -> char { | |
54a0048b SL |
1259 | let ch = match self[idx..].chars().next() { |
1260 | Some(ch) => ch, | |
1261 | None => panic!("cannot remove a char from the end of a string"), | |
1262 | }; | |
1a4d82fc | 1263 | |
c34b1796 | 1264 | let next = idx + ch.len_utf8(); |
54a0048b | 1265 | let len = self.len(); |
1a4d82fc | 1266 | unsafe { |
dfeec247 | 1267 | ptr::copy(self.vec.as_ptr().add(next), self.vec.as_mut_ptr().add(idx), len - next); |
1a4d82fc JJ |
1268 | self.vec.set_len(len - (next - idx)); |
1269 | } | |
1270 | ch | |
1271 | } | |
1272 | ||
6a06907d XL |
1273 | /// Remove all matches of pattern `pat` in the `String`. |
1274 | /// | |
1275 | /// # Examples | |
1276 | /// | |
1277 | /// ``` | |
1278 | /// #![feature(string_remove_matches)] | |
1279 | /// let mut s = String::from("Trees are not green, the sky is not blue."); | |
1280 | /// s.remove_matches("not "); | |
1281 | /// assert_eq!("Trees are green, the sky is blue.", s); | |
1282 | /// ``` | |
1283 | /// | |
1284 | /// Matches will be detected and removed iteratively, so in cases where | |
1285 | /// patterns overlap, only the first pattern will be removed: | |
1286 | /// | |
1287 | /// ``` | |
1288 | /// #![feature(string_remove_matches)] | |
1289 | /// let mut s = String::from("banana"); | |
1290 | /// s.remove_matches("ana"); | |
1291 | /// assert_eq!("bna", s); | |
1292 | /// ``` | |
17df50a5 | 1293 | #[cfg(not(no_global_oom_handling))] |
6a06907d XL |
1294 | #[unstable(feature = "string_remove_matches", reason = "new API", issue = "72826")] |
1295 | pub fn remove_matches<'a, P>(&'a mut self, pat: P) | |
1296 | where | |
1297 | P: for<'x> Pattern<'x>, | |
1298 | { | |
1299 | use core::str::pattern::Searcher; | |
1300 | ||
17df50a5 | 1301 | let rejections = { |
6a06907d | 1302 | let mut searcher = pat.into_searcher(self); |
17df50a5 XL |
1303 | // Per Searcher::next: |
1304 | // | |
1305 | // A Match result needs to contain the whole matched pattern, | |
1306 | // however Reject results may be split up into arbitrary many | |
1307 | // adjacent fragments. Both ranges may have zero length. | |
1308 | // | |
1309 | // In practice the implementation of Searcher::next_match tends to | |
1310 | // be more efficient, so we use it here and do some work to invert | |
1311 | // matches into rejections since that's what we want to copy below. | |
1312 | let mut front = 0; | |
1313 | let rejections: Vec<_> = from_fn(|| { | |
1314 | let (start, end) = searcher.next_match()?; | |
1315 | let prev_front = front; | |
1316 | front = end; | |
1317 | Some((prev_front, start)) | |
1318 | }) | |
1319 | .collect(); | |
1320 | rejections.into_iter().chain(core::iter::once((front, self.len()))) | |
6a06907d XL |
1321 | }; |
1322 | ||
17df50a5 XL |
1323 | let mut len = 0; |
1324 | let ptr = self.vec.as_mut_ptr(); | |
1325 | ||
1326 | for (start, end) in rejections { | |
1327 | let count = end - start; | |
1328 | if start != len { | |
1329 | // SAFETY: per Searcher::next: | |
1330 | // | |
1331 | // The stream of Match and Reject values up to a Done will | |
1332 | // contain index ranges that are adjacent, non-overlapping, | |
1333 | // covering the whole haystack, and laying on utf8 | |
1334 | // boundaries. | |
1335 | unsafe { | |
1336 | ptr::copy(ptr.add(start), ptr.add(len), count); | |
1337 | } | |
1338 | } | |
1339 | len += count; | |
1340 | } | |
6a06907d | 1341 | |
6a06907d | 1342 | unsafe { |
17df50a5 | 1343 | self.vec.set_len(len); |
6a06907d XL |
1344 | } |
1345 | } | |
1346 | ||
3b2f2976 XL |
1347 | /// Retains only the characters specified by the predicate. |
1348 | /// | |
1349 | /// In other words, remove all characters `c` such that `f(c)` returns `false`. | |
48663c56 XL |
1350 | /// This method operates in place, visiting each character exactly once in the |
1351 | /// original order, and preserves the order of the retained characters. | |
3b2f2976 XL |
1352 | /// |
1353 | /// # Examples | |
1354 | /// | |
1355 | /// ``` | |
3b2f2976 XL |
1356 | /// let mut s = String::from("f_o_ob_ar"); |
1357 | /// | |
1358 | /// s.retain(|c| c != '_'); | |
1359 | /// | |
1360 | /// assert_eq!(s, "foobar"); | |
1361 | /// ``` | |
48663c56 | 1362 | /// |
94222f64 XL |
1363 | /// Because the elements are visited exactly once in the original order, |
1364 | /// external state may be used to decide which elements to keep. | |
48663c56 XL |
1365 | /// |
1366 | /// ``` | |
1367 | /// let mut s = String::from("abcde"); | |
1368 | /// let keep = [false, true, true, false, true]; | |
94222f64 XL |
1369 | /// let mut iter = keep.iter(); |
1370 | /// s.retain(|_| *iter.next().unwrap()); | |
48663c56 XL |
1371 | /// assert_eq!(s, "bce"); |
1372 | /// ``` | |
3b2f2976 | 1373 | #[inline] |
0531ce1d | 1374 | #[stable(feature = "string_retain", since = "1.26.0")] |
3b2f2976 | 1375 | pub fn retain<F>(&mut self, mut f: F) |
dfeec247 XL |
1376 | where |
1377 | F: FnMut(char) -> bool, | |
3b2f2976 | 1378 | { |
cdc7bbd5 XL |
1379 | struct SetLenOnDrop<'a> { |
1380 | s: &'a mut String, | |
1381 | idx: usize, | |
1382 | del_bytes: usize, | |
1383 | } | |
3b2f2976 | 1384 | |
cdc7bbd5 XL |
1385 | impl<'a> Drop for SetLenOnDrop<'a> { |
1386 | fn drop(&mut self) { | |
1387 | let new_len = self.idx - self.del_bytes; | |
1388 | debug_assert!(new_len <= self.s.len()); | |
1389 | unsafe { self.s.vec.set_len(new_len) }; | |
1390 | } | |
29967ef6 XL |
1391 | } |
1392 | ||
cdc7bbd5 XL |
1393 | let len = self.len(); |
1394 | let mut guard = SetLenOnDrop { s: self, idx: 0, del_bytes: 0 }; | |
1395 | ||
1396 | while guard.idx < len { | |
1397 | let ch = unsafe { guard.s.get_unchecked(guard.idx..len).chars().next().unwrap() }; | |
3b2f2976 XL |
1398 | let ch_len = ch.len_utf8(); |
1399 | ||
1400 | if !f(ch) { | |
cdc7bbd5 XL |
1401 | guard.del_bytes += ch_len; |
1402 | } else if guard.del_bytes > 0 { | |
3b2f2976 | 1403 | unsafe { |
dfeec247 | 1404 | ptr::copy( |
cdc7bbd5 XL |
1405 | guard.s.vec.as_ptr().add(guard.idx), |
1406 | guard.s.vec.as_mut_ptr().add(guard.idx - guard.del_bytes), | |
dfeec247 XL |
1407 | ch_len, |
1408 | ); | |
3b2f2976 XL |
1409 | } |
1410 | } | |
1411 | ||
1412 | // Point idx to the next char | |
cdc7bbd5 | 1413 | guard.idx += ch_len; |
3b2f2976 XL |
1414 | } |
1415 | ||
cdc7bbd5 | 1416 | drop(guard); |
3b2f2976 XL |
1417 | } |
1418 | ||
9cc50fc6 | 1419 | /// Inserts a character into this `String` at a byte position. |
1a4d82fc | 1420 | /// |
3dfed10e | 1421 | /// This is an *O*(*n*) operation as it requires copying every element in the |
1a4d82fc JJ |
1422 | /// buffer. |
1423 | /// | |
1424 | /// # Panics | |
1425 | /// | |
9cc50fc6 SL |
1426 | /// Panics if `idx` is larger than the `String`'s length, or if it does not |
1427 | /// lie on a [`char`] boundary. | |
1428 | /// | |
9cc50fc6 SL |
1429 | /// # Examples |
1430 | /// | |
1431 | /// Basic usage: | |
1432 | /// | |
1433 | /// ``` | |
1434 | /// let mut s = String::with_capacity(3); | |
1435 | /// | |
1436 | /// s.insert(0, 'f'); | |
1437 | /// s.insert(1, 'o'); | |
1438 | /// s.insert(2, 'o'); | |
1439 | /// | |
1440 | /// assert_eq!("foo", s); | |
1441 | /// ``` | |
17df50a5 | 1442 | #[cfg(not(no_global_oom_handling))] |
85aaf69f SL |
1443 | #[inline] |
1444 | #[stable(feature = "rust1", since = "1.0.0")] | |
1445 | pub fn insert(&mut self, idx: usize, ch: char) { | |
1a4d82fc | 1446 | assert!(self.is_char_boundary(idx)); |
c30ab7b3 SL |
1447 | let mut bits = [0; 4]; |
1448 | let bits = ch.encode_utf8(&mut bits).as_bytes(); | |
5bcae85e SL |
1449 | |
1450 | unsafe { | |
c30ab7b3 | 1451 | self.insert_bytes(idx, bits); |
5bcae85e SL |
1452 | } |
1453 | } | |
1454 | ||
17df50a5 | 1455 | #[cfg(not(no_global_oom_handling))] |
5bcae85e SL |
1456 | unsafe fn insert_bytes(&mut self, idx: usize, bytes: &[u8]) { |
1457 | let len = self.len(); | |
1458 | let amt = bytes.len(); | |
54a0048b | 1459 | self.vec.reserve(amt); |
1a4d82fc | 1460 | |
f035d41b XL |
1461 | unsafe { |
1462 | ptr::copy(self.vec.as_ptr().add(idx), self.vec.as_mut_ptr().add(idx + amt), len - idx); | |
136023e0 | 1463 | ptr::copy_nonoverlapping(bytes.as_ptr(), self.vec.as_mut_ptr().add(idx), amt); |
f035d41b XL |
1464 | self.vec.set_len(len + amt); |
1465 | } | |
5bcae85e SL |
1466 | } |
1467 | ||
1468 | /// Inserts a string slice into this `String` at a byte position. | |
1469 | /// | |
3dfed10e | 1470 | /// This is an *O*(*n*) operation as it requires copying every element in the |
5bcae85e SL |
1471 | /// buffer. |
1472 | /// | |
1473 | /// # Panics | |
1474 | /// | |
1475 | /// Panics if `idx` is larger than the `String`'s length, or if it does not | |
1476 | /// lie on a [`char`] boundary. | |
1477 | /// | |
5bcae85e SL |
1478 | /// # Examples |
1479 | /// | |
1480 | /// Basic usage: | |
1481 | /// | |
1482 | /// ``` | |
5bcae85e SL |
1483 | /// let mut s = String::from("bar"); |
1484 | /// | |
1485 | /// s.insert_str(0, "foo"); | |
1486 | /// | |
1487 | /// assert_eq!("foobar", s); | |
1488 | /// ``` | |
17df50a5 | 1489 | #[cfg(not(no_global_oom_handling))] |
5bcae85e | 1490 | #[inline] |
32a655c1 | 1491 | #[stable(feature = "insert_str", since = "1.16.0")] |
5bcae85e | 1492 | pub fn insert_str(&mut self, idx: usize, string: &str) { |
5bcae85e SL |
1493 | assert!(self.is_char_boundary(idx)); |
1494 | ||
1a4d82fc | 1495 | unsafe { |
5bcae85e | 1496 | self.insert_bytes(idx, string.as_bytes()); |
1a4d82fc JJ |
1497 | } |
1498 | } | |
1499 | ||
9cc50fc6 | 1500 | /// Returns a mutable reference to the contents of this `String`. |
1a4d82fc | 1501 | /// |
9cc50fc6 SL |
1502 | /// # Safety |
1503 | /// | |
3c0e092e XL |
1504 | /// This function is unsafe because the returned `&mut Vec` allows writing |
1505 | /// bytes which are not valid UTF-8. If this constraint is violated, using | |
1506 | /// the original `String` after dropping the `&mut Vec` may violate memory | |
1507 | /// safety, as the rest of the standard library assumes that `String`s are | |
1508 | /// valid UTF-8. | |
1a4d82fc JJ |
1509 | /// |
1510 | /// # Examples | |
1511 | /// | |
9cc50fc6 SL |
1512 | /// Basic usage: |
1513 | /// | |
1a4d82fc | 1514 | /// ``` |
62682a34 | 1515 | /// let mut s = String::from("hello"); |
9cc50fc6 | 1516 | /// |
1a4d82fc JJ |
1517 | /// unsafe { |
1518 | /// let vec = s.as_mut_vec(); | |
9cc50fc6 SL |
1519 | /// assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]); |
1520 | /// | |
1a4d82fc JJ |
1521 | /// vec.reverse(); |
1522 | /// } | |
c34b1796 | 1523 | /// assert_eq!(s, "olleh"); |
1a4d82fc | 1524 | /// ``` |
85aaf69f SL |
1525 | #[inline] |
1526 | #[stable(feature = "rust1", since = "1.0.0")] | |
1527 | pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8> { | |
1a4d82fc JJ |
1528 | &mut self.vec |
1529 | } | |
1530 | ||
60c5eb7d | 1531 | /// Returns the length of this `String`, in bytes, not [`char`]s or |
94222f64 | 1532 | /// graphemes. In other words, it might not be what a human considers the |
60c5eb7d | 1533 | /// length of the string. |
1a4d82fc JJ |
1534 | /// |
1535 | /// # Examples | |
1536 | /// | |
9cc50fc6 SL |
1537 | /// Basic usage: |
1538 | /// | |
1a4d82fc | 1539 | /// ``` |
9cc50fc6 | 1540 | /// let a = String::from("foo"); |
1a4d82fc | 1541 | /// assert_eq!(a.len(), 3); |
60c5eb7d XL |
1542 | /// |
1543 | /// let fancy_f = String::from("ƒoo"); | |
1544 | /// assert_eq!(fancy_f.len(), 4); | |
1545 | /// assert_eq!(fancy_f.chars().count(), 3); | |
1a4d82fc JJ |
1546 | /// ``` |
1547 | #[inline] | |
3c0e092e | 1548 | #[must_use] |
85aaf69f | 1549 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1550 | pub fn len(&self) -> usize { |
1551 | self.vec.len() | |
1552 | } | |
1a4d82fc | 1553 | |
9fa01778 | 1554 | /// Returns `true` if this `String` has a length of zero, and `false` otherwise. |
1a4d82fc JJ |
1555 | /// |
1556 | /// # Examples | |
1557 | /// | |
9cc50fc6 SL |
1558 | /// Basic usage: |
1559 | /// | |
1a4d82fc JJ |
1560 | /// ``` |
1561 | /// let mut v = String::new(); | |
1562 | /// assert!(v.is_empty()); | |
9cc50fc6 | 1563 | /// |
1a4d82fc JJ |
1564 | /// v.push('a'); |
1565 | /// assert!(!v.is_empty()); | |
1566 | /// ``` | |
85aaf69f | 1567 | #[inline] |
3c0e092e | 1568 | #[must_use] |
85aaf69f | 1569 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1570 | pub fn is_empty(&self) -> bool { |
1571 | self.len() == 0 | |
1572 | } | |
1a4d82fc | 1573 | |
fc512014 | 1574 | /// Splits the string into two at the given byte index. |
476ff2be | 1575 | /// |
8bb4bdeb XL |
1576 | /// Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and |
1577 | /// the returned `String` contains bytes `[at, len)`. `at` must be on the | |
1578 | /// boundary of a UTF-8 code point. | |
476ff2be | 1579 | /// |
8bb4bdeb | 1580 | /// Note that the capacity of `self` does not change. |
476ff2be SL |
1581 | /// |
1582 | /// # Panics | |
1583 | /// | |
8bb4bdeb | 1584 | /// Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last |
476ff2be SL |
1585 | /// code point of the string. |
1586 | /// | |
1587 | /// # Examples | |
1588 | /// | |
1589 | /// ``` | |
476ff2be SL |
1590 | /// # fn main() { |
1591 | /// let mut hello = String::from("Hello, World!"); | |
1592 | /// let world = hello.split_off(7); | |
1593 | /// assert_eq!(hello, "Hello, "); | |
1594 | /// assert_eq!(world, "World!"); | |
1595 | /// # } | |
1596 | /// ``` | |
17df50a5 | 1597 | #[cfg(not(no_global_oom_handling))] |
476ff2be | 1598 | #[inline] |
32a655c1 | 1599 | #[stable(feature = "string_split_off", since = "1.16.0")] |
ba9703b0 | 1600 | #[must_use = "use `.truncate()` if you don't need the other half"] |
8bb4bdeb XL |
1601 | pub fn split_off(&mut self, at: usize) -> String { |
1602 | assert!(self.is_char_boundary(at)); | |
1603 | let other = self.vec.split_off(at); | |
476ff2be SL |
1604 | unsafe { String::from_utf8_unchecked(other) } |
1605 | } | |
1606 | ||
9cc50fc6 SL |
1607 | /// Truncates this `String`, removing all contents. |
1608 | /// | |
1609 | /// While this means the `String` will have a length of zero, it does not | |
1610 | /// touch its capacity. | |
1a4d82fc JJ |
1611 | /// |
1612 | /// # Examples | |
1613 | /// | |
9cc50fc6 SL |
1614 | /// Basic usage: |
1615 | /// | |
1a4d82fc | 1616 | /// ``` |
9cc50fc6 SL |
1617 | /// let mut s = String::from("foo"); |
1618 | /// | |
1a4d82fc | 1619 | /// s.clear(); |
9cc50fc6 | 1620 | /// |
1a4d82fc | 1621 | /// assert!(s.is_empty()); |
9cc50fc6 SL |
1622 | /// assert_eq!(0, s.len()); |
1623 | /// assert_eq!(3, s.capacity()); | |
1a4d82fc JJ |
1624 | /// ``` |
1625 | #[inline] | |
85aaf69f | 1626 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1627 | pub fn clear(&mut self) { |
1628 | self.vec.clear() | |
1629 | } | |
d9579d0f | 1630 | |
5099ac24 FG |
1631 | /// Removes the specified range from the string in bulk, returning all |
1632 | /// removed characters as an iterator. | |
9cc50fc6 | 1633 | /// |
5099ac24 FG |
1634 | /// The returned iterator keeps a mutable borrow on the string to optimize |
1635 | /// its implementation. | |
d9579d0f AL |
1636 | /// |
1637 | /// # Panics | |
1638 | /// | |
9cc50fc6 SL |
1639 | /// Panics if the starting point or end point do not lie on a [`char`] |
1640 | /// boundary, or if they're out of bounds. | |
1641 | /// | |
5099ac24 FG |
1642 | /// # Leaking |
1643 | /// | |
1644 | /// If the returned iterator goes out of scope without being dropped (due to | |
1645 | /// [`core::mem::forget`], for example), the string may still contain a copy | |
1646 | /// of any drained characters, or may have lost characters arbitrarily, | |
1647 | /// including characters outside the range. | |
1648 | /// | |
d9579d0f AL |
1649 | /// # Examples |
1650 | /// | |
9cc50fc6 SL |
1651 | /// Basic usage: |
1652 | /// | |
d9579d0f | 1653 | /// ``` |
d9579d0f AL |
1654 | /// let mut s = String::from("α is alpha, β is beta"); |
1655 | /// let beta_offset = s.find('β').unwrap_or(s.len()); | |
1656 | /// | |
1657 | /// // Remove the range up until the β from the string | |
1658 | /// let t: String = s.drain(..beta_offset).collect(); | |
1659 | /// assert_eq!(t, "α is alpha, "); | |
1660 | /// assert_eq!(s, "β is beta"); | |
1661 | /// | |
5099ac24 | 1662 | /// // A full range clears the string, like `clear()` does |
d9579d0f AL |
1663 | /// s.drain(..); |
1664 | /// assert_eq!(s, ""); | |
1665 | /// ``` | |
92a42be0 | 1666 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 1667 | pub fn drain<R>(&mut self, range: R) -> Drain<'_> |
dfeec247 XL |
1668 | where |
1669 | R: RangeBounds<usize>, | |
92a42be0 | 1670 | { |
d9579d0f AL |
1671 | // Memory safety |
1672 | // | |
1673 | // The String version of Drain does not have the memory safety issues | |
1674 | // of the vector version. The data is just plain bytes. | |
1675 | // Because the range removal happens in Drop, if the Drain iterator is leaked, | |
1676 | // the removal will not happen. | |
6a06907d | 1677 | let Range { start, end } = slice::range(range, ..self.len()); |
1b1a35ee XL |
1678 | assert!(self.is_char_boundary(start)); |
1679 | assert!(self.is_char_boundary(end)); | |
d9579d0f AL |
1680 | |
1681 | // Take out two simultaneous borrows. The &mut String won't be accessed | |
1682 | // until iteration is over, in Drop. | |
1683 | let self_ptr = self as *mut _; | |
6a06907d | 1684 | // SAFETY: `slice::range` and `is_char_boundary` do the appropriate bounds checks. |
1b1a35ee | 1685 | let chars_iter = unsafe { self.get_unchecked(start..end) }.chars(); |
d9579d0f | 1686 | |
dfeec247 | 1687 | Drain { start, end, iter: chars_iter, string: self_ptr } |
d9579d0f | 1688 | } |
c1a9b12d | 1689 | |
83c7162d | 1690 | /// Removes the specified range in the string, |
ea8adc8c XL |
1691 | /// and replaces it with the given string. |
1692 | /// The given string doesn't need to be the same length as the range. | |
7cac9316 | 1693 | /// |
7cac9316 XL |
1694 | /// # Panics |
1695 | /// | |
1696 | /// Panics if the starting point or end point do not lie on a [`char`] | |
1697 | /// boundary, or if they're out of bounds. | |
1698 | /// | |
7cac9316 XL |
1699 | /// # Examples |
1700 | /// | |
1701 | /// Basic usage: | |
1702 | /// | |
1703 | /// ``` | |
7cac9316 XL |
1704 | /// let mut s = String::from("α is alpha, β is beta"); |
1705 | /// let beta_offset = s.find('β').unwrap_or(s.len()); | |
1706 | /// | |
1707 | /// // Replace the range up until the β from the string | |
83c7162d | 1708 | /// s.replace_range(..beta_offset, "Α is capital alpha; "); |
7cac9316 XL |
1709 | /// assert_eq!(s, "Α is capital alpha; β is beta"); |
1710 | /// ``` | |
17df50a5 | 1711 | #[cfg(not(no_global_oom_handling))] |
83c7162d XL |
1712 | #[stable(feature = "splice", since = "1.27.0")] |
1713 | pub fn replace_range<R>(&mut self, range: R, replace_with: &str) | |
dfeec247 XL |
1714 | where |
1715 | R: RangeBounds<usize>, | |
7cac9316 XL |
1716 | { |
1717 | // Memory safety | |
1718 | // | |
83c7162d | 1719 | // Replace_range does not have the memory safety issues of a vector Splice. |
7cac9316 | 1720 | // of the vector version. The data is just plain bytes. |
ea8adc8c | 1721 | |
5869c6ff XL |
1722 | // WARNING: Inlining this variable would be unsound (#81138) |
1723 | let start = range.start_bound(); | |
1724 | match start { | |
dfeec247 XL |
1725 | Included(&n) => assert!(self.is_char_boundary(n)), |
1726 | Excluded(&n) => assert!(self.is_char_boundary(n + 1)), | |
1727 | Unbounded => {} | |
7cac9316 | 1728 | }; |
5869c6ff XL |
1729 | // WARNING: Inlining this variable would be unsound (#81138) |
1730 | let end = range.end_bound(); | |
1731 | match end { | |
dfeec247 XL |
1732 | Included(&n) => assert!(self.is_char_boundary(n + 1)), |
1733 | Excluded(&n) => assert!(self.is_char_boundary(n)), | |
1734 | Unbounded => {} | |
7cac9316 XL |
1735 | }; |
1736 | ||
5869c6ff XL |
1737 | // Using `range` again would be unsound (#81138) |
1738 | // We assume the bounds reported by `range` remain the same, but | |
1739 | // an adversarial implementation could change between calls | |
1740 | unsafe { self.as_mut_vec() }.splice((start, end), replace_with.bytes()); | |
7cac9316 XL |
1741 | } |
1742 | ||
c295e0f8 | 1743 | /// Converts this `String` into a <code>[Box]<[str]></code>. |
9cc50fc6 SL |
1744 | /// |
1745 | /// This will drop any excess capacity. | |
1746 | /// | |
c295e0f8 | 1747 | /// [str]: prim@str "str" |
3b2f2976 | 1748 | /// |
9cc50fc6 SL |
1749 | /// # Examples |
1750 | /// | |
1751 | /// Basic usage: | |
1752 | /// | |
1753 | /// ``` | |
1754 | /// let s = String::from("hello"); | |
c1a9b12d | 1755 | /// |
9cc50fc6 SL |
1756 | /// let b = s.into_boxed_str(); |
1757 | /// ``` | |
17df50a5 | 1758 | #[cfg(not(no_global_oom_handling))] |
e9174d1e | 1759 | #[stable(feature = "box_str", since = "1.4.0")] |
c295e0f8 | 1760 | #[must_use = "`self` will be dropped if the result is not used"] |
83c7162d | 1761 | #[inline] |
e9174d1e | 1762 | pub fn into_boxed_str(self) -> Box<str> { |
c1a9b12d | 1763 | let slice = self.vec.into_boxed_slice(); |
041b39d2 | 1764 | unsafe { from_boxed_utf8_unchecked(slice) } |
c1a9b12d | 1765 | } |
1a4d82fc JJ |
1766 | } |
1767 | ||
1768 | impl FromUtf8Error { | |
cc61c64b XL |
1769 | /// Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`. |
1770 | /// | |
1771 | /// # Examples | |
1772 | /// | |
1773 | /// Basic usage: | |
1774 | /// | |
1775 | /// ``` | |
cc61c64b XL |
1776 | /// // some invalid bytes, in a vector |
1777 | /// let bytes = vec![0, 159]; | |
1778 | /// | |
1779 | /// let value = String::from_utf8(bytes); | |
1780 | /// | |
1781 | /// assert_eq!(&[0, 159], value.unwrap_err().as_bytes()); | |
1782 | /// ``` | |
c295e0f8 | 1783 | #[must_use] |
0531ce1d | 1784 | #[stable(feature = "from_utf8_error_as_bytes", since = "1.26.0")] |
cc61c64b XL |
1785 | pub fn as_bytes(&self) -> &[u8] { |
1786 | &self.bytes[..] | |
1787 | } | |
1788 | ||
92a42be0 SL |
1789 | /// Returns the bytes that were attempted to convert to a `String`. |
1790 | /// | |
1791 | /// This method is carefully constructed to avoid allocation. It will | |
1792 | /// consume the error, moving out the bytes, so that a copy of the bytes | |
1793 | /// does not need to be made. | |
1794 | /// | |
1795 | /// # Examples | |
1796 | /// | |
1797 | /// Basic usage: | |
1798 | /// | |
1799 | /// ``` | |
1800 | /// // some invalid bytes, in a vector | |
1801 | /// let bytes = vec![0, 159]; | |
1802 | /// | |
1803 | /// let value = String::from_utf8(bytes); | |
1804 | /// | |
1805 | /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes()); | |
1806 | /// ``` | |
c295e0f8 | 1807 | #[must_use = "`self` will be dropped if the result is not used"] |
85aaf69f | 1808 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1809 | pub fn into_bytes(self) -> Vec<u8> { |
1810 | self.bytes | |
1811 | } | |
1a4d82fc | 1812 | |
92a42be0 SL |
1813 | /// Fetch a `Utf8Error` to get more details about the conversion failure. |
1814 | /// | |
1815 | /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may | |
1816 | /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's | |
1817 | /// an analogue to `FromUtf8Error`. See its documentation for more details | |
1818 | /// on using it. | |
1819 | /// | |
c295e0f8 XL |
1820 | /// [`std::str`]: core::str "std::str" |
1821 | /// [`&str`]: prim@str "&str" | |
92a42be0 SL |
1822 | /// |
1823 | /// # Examples | |
1824 | /// | |
1825 | /// Basic usage: | |
1826 | /// | |
1827 | /// ``` | |
1828 | /// // some invalid bytes, in a vector | |
1829 | /// let bytes = vec![0, 159]; | |
1830 | /// | |
1831 | /// let error = String::from_utf8(bytes).unwrap_err().utf8_error(); | |
1832 | /// | |
1833 | /// // the first byte is invalid here | |
1834 | /// assert_eq!(1, error.valid_up_to()); | |
1835 | /// ``` | |
3c0e092e | 1836 | #[must_use] |
85aaf69f | 1837 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1838 | pub fn utf8_error(&self) -> Utf8Error { |
1839 | self.error | |
1840 | } | |
1a4d82fc JJ |
1841 | } |
1842 | ||
85aaf69f SL |
1843 | #[stable(feature = "rust1", since = "1.0.0")] |
1844 | impl fmt::Display for FromUtf8Error { | |
9fa01778 | 1845 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1846 | fmt::Display::fmt(&self.error, f) |
1a4d82fc JJ |
1847 | } |
1848 | } | |
1849 | ||
85aaf69f SL |
1850 | #[stable(feature = "rust1", since = "1.0.0")] |
1851 | impl fmt::Display for FromUtf16Error { | |
9fa01778 | 1852 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1853 | fmt::Display::fmt("invalid utf-16: lone surrogate found", f) |
1a4d82fc JJ |
1854 | } |
1855 | } | |
1856 | ||
17df50a5 | 1857 | #[cfg(not(no_global_oom_handling))] |
b039eaaf SL |
1858 | #[stable(feature = "rust1", since = "1.0.0")] |
1859 | impl Clone for String { | |
1860 | fn clone(&self) -> Self { | |
1861 | String { vec: self.vec.clone() } | |
1862 | } | |
1863 | ||
1864 | fn clone_from(&mut self, source: &Self) { | |
1865 | self.vec.clone_from(&source.vec); | |
1866 | } | |
1867 | } | |
1868 | ||
17df50a5 | 1869 | #[cfg(not(no_global_oom_handling))] |
85aaf69f | 1870 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1871 | impl FromIterator<char> for String { |
54a0048b | 1872 | fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String { |
1a4d82fc | 1873 | let mut buf = String::new(); |
54a0048b | 1874 | buf.extend(iter); |
1a4d82fc JJ |
1875 | buf |
1876 | } | |
1877 | } | |
1878 | ||
17df50a5 | 1879 | #[cfg(not(no_global_oom_handling))] |
8bb4bdeb XL |
1880 | #[stable(feature = "string_from_iter_by_ref", since = "1.17.0")] |
1881 | impl<'a> FromIterator<&'a char> for String { | |
1882 | fn from_iter<I: IntoIterator<Item = &'a char>>(iter: I) -> String { | |
1883 | let mut buf = String::new(); | |
1884 | buf.extend(iter); | |
1885 | buf | |
1886 | } | |
1887 | } | |
1888 | ||
17df50a5 | 1889 | #[cfg(not(no_global_oom_handling))] |
85aaf69f | 1890 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1891 | impl<'a> FromIterator<&'a str> for String { |
54a0048b | 1892 | fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String { |
e9174d1e | 1893 | let mut buf = String::new(); |
54a0048b | 1894 | buf.extend(iter); |
e9174d1e SL |
1895 | buf |
1896 | } | |
1897 | } | |
1898 | ||
17df50a5 | 1899 | #[cfg(not(no_global_oom_handling))] |
e9174d1e SL |
1900 | #[stable(feature = "extend_string", since = "1.4.0")] |
1901 | impl FromIterator<String> for String { | |
54a0048b | 1902 | fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String { |
0731742a XL |
1903 | let mut iterator = iter.into_iter(); |
1904 | ||
1905 | // Because we're iterating over `String`s, we can avoid at least | |
1906 | // one allocation by getting the first string from the iterator | |
1907 | // and appending to it all the subsequent strings. | |
1908 | match iterator.next() { | |
1909 | None => String::new(), | |
1910 | Some(mut buf) => { | |
1911 | buf.extend(iterator); | |
1912 | buf | |
1913 | } | |
1914 | } | |
1a4d82fc JJ |
1915 | } |
1916 | } | |
1917 | ||
17df50a5 | 1918 | #[cfg(not(no_global_oom_handling))] |
f035d41b XL |
1919 | #[stable(feature = "box_str2", since = "1.45.0")] |
1920 | impl FromIterator<Box<str>> for String { | |
1921 | fn from_iter<I: IntoIterator<Item = Box<str>>>(iter: I) -> String { | |
1922 | let mut buf = String::new(); | |
1923 | buf.extend(iter); | |
1924 | buf | |
1925 | } | |
1926 | } | |
1927 | ||
17df50a5 | 1928 | #[cfg(not(no_global_oom_handling))] |
7cac9316 XL |
1929 | #[stable(feature = "herd_cows", since = "1.19.0")] |
1930 | impl<'a> FromIterator<Cow<'a, str>> for String { | |
1931 | fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String { | |
0731742a XL |
1932 | let mut iterator = iter.into_iter(); |
1933 | ||
1934 | // Because we're iterating over CoWs, we can (potentially) avoid at least | |
1935 | // one allocation by getting the first item and appending to it all the | |
1936 | // subsequent items. | |
1937 | match iterator.next() { | |
1938 | None => String::new(), | |
1939 | Some(cow) => { | |
1940 | let mut buf = cow.into_owned(); | |
1941 | buf.extend(iterator); | |
1942 | buf | |
1943 | } | |
1944 | } | |
7cac9316 XL |
1945 | } |
1946 | } | |
1947 | ||
17df50a5 | 1948 | #[cfg(not(no_global_oom_handling))] |
bd371182 | 1949 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1950 | impl Extend<char> for String { |
54a0048b SL |
1951 | fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) { |
1952 | let iterator = iter.into_iter(); | |
1a4d82fc JJ |
1953 | let (lower_bound, _) = iterator.size_hint(); |
1954 | self.reserve(lower_bound); | |
0731742a | 1955 | iterator.for_each(move |c| self.push(c)); |
1a4d82fc | 1956 | } |
f9f354fc XL |
1957 | |
1958 | #[inline] | |
1959 | fn extend_one(&mut self, c: char) { | |
1960 | self.push(c); | |
1961 | } | |
1962 | ||
1963 | #[inline] | |
1964 | fn extend_reserve(&mut self, additional: usize) { | |
1965 | self.reserve(additional); | |
1966 | } | |
1a4d82fc JJ |
1967 | } |
1968 | ||
17df50a5 | 1969 | #[cfg(not(no_global_oom_handling))] |
62682a34 SL |
1970 | #[stable(feature = "extend_ref", since = "1.2.0")] |
1971 | impl<'a> Extend<&'a char> for String { | |
54a0048b SL |
1972 | fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) { |
1973 | self.extend(iter.into_iter().cloned()); | |
62682a34 | 1974 | } |
f9f354fc XL |
1975 | |
1976 | #[inline] | |
1977 | fn extend_one(&mut self, &c: &'a char) { | |
1978 | self.push(c); | |
1979 | } | |
1980 | ||
1981 | #[inline] | |
1982 | fn extend_reserve(&mut self, additional: usize) { | |
1983 | self.reserve(additional); | |
1984 | } | |
62682a34 SL |
1985 | } |
1986 | ||
17df50a5 | 1987 | #[cfg(not(no_global_oom_handling))] |
bd371182 | 1988 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1989 | impl<'a> Extend<&'a str> for String { |
54a0048b | 1990 | fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) { |
0731742a | 1991 | iter.into_iter().for_each(move |s| self.push_str(s)); |
1a4d82fc | 1992 | } |
f9f354fc XL |
1993 | |
1994 | #[inline] | |
1995 | fn extend_one(&mut self, s: &'a str) { | |
1996 | self.push_str(s); | |
1997 | } | |
1a4d82fc JJ |
1998 | } |
1999 | ||
17df50a5 | 2000 | #[cfg(not(no_global_oom_handling))] |
f035d41b XL |
2001 | #[stable(feature = "box_str2", since = "1.45.0")] |
2002 | impl Extend<Box<str>> for String { | |
2003 | fn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I) { | |
2004 | iter.into_iter().for_each(move |s| self.push_str(&s)); | |
2005 | } | |
2006 | } | |
2007 | ||
17df50a5 | 2008 | #[cfg(not(no_global_oom_handling))] |
e9174d1e SL |
2009 | #[stable(feature = "extend_string", since = "1.4.0")] |
2010 | impl Extend<String> for String { | |
54a0048b | 2011 | fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) { |
0731742a | 2012 | iter.into_iter().for_each(move |s| self.push_str(&s)); |
e9174d1e | 2013 | } |
f9f354fc XL |
2014 | |
2015 | #[inline] | |
2016 | fn extend_one(&mut self, s: String) { | |
2017 | self.push_str(&s); | |
2018 | } | |
e9174d1e SL |
2019 | } |
2020 | ||
17df50a5 | 2021 | #[cfg(not(no_global_oom_handling))] |
7cac9316 XL |
2022 | #[stable(feature = "herd_cows", since = "1.19.0")] |
2023 | impl<'a> Extend<Cow<'a, str>> for String { | |
2024 | fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) { | |
0731742a | 2025 | iter.into_iter().for_each(move |s| self.push_str(&s)); |
7cac9316 | 2026 | } |
f9f354fc XL |
2027 | |
2028 | #[inline] | |
2029 | fn extend_one(&mut self, s: Cow<'a, str>) { | |
2030 | self.push_str(&s); | |
2031 | } | |
7cac9316 XL |
2032 | } |
2033 | ||
ba9703b0 XL |
2034 | /// A convenience impl that delegates to the impl for `&str`. |
2035 | /// | |
2036 | /// # Examples | |
2037 | /// | |
2038 | /// ``` | |
2039 | /// assert_eq!(String::from("Hello world").find("world"), Some(6)); | |
2040 | /// ``` | |
dfeec247 XL |
2041 | #[unstable( |
2042 | feature = "pattern", | |
2043 | reason = "API not fully fleshed out and ready to be stabilized", | |
2044 | issue = "27721" | |
2045 | )] | |
c34b1796 AL |
2046 | impl<'a, 'b> Pattern<'a> for &'b String { |
2047 | type Searcher = <&'b str as Pattern<'a>>::Searcher; | |
2048 | ||
2049 | fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher { | |
2050 | self[..].into_searcher(haystack) | |
2051 | } | |
2052 | ||
2053 | #[inline] | |
2054 | fn is_contained_in(self, haystack: &'a str) -> bool { | |
2055 | self[..].is_contained_in(haystack) | |
2056 | } | |
2057 | ||
2058 | #[inline] | |
2059 | fn is_prefix_of(self, haystack: &'a str) -> bool { | |
2060 | self[..].is_prefix_of(haystack) | |
2061 | } | |
ba9703b0 XL |
2062 | |
2063 | #[inline] | |
2064 | fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> { | |
2065 | self[..].strip_prefix_of(haystack) | |
2066 | } | |
2067 | ||
2068 | #[inline] | |
2069 | fn is_suffix_of(self, haystack: &'a str) -> bool { | |
2070 | self[..].is_suffix_of(haystack) | |
2071 | } | |
2072 | ||
2073 | #[inline] | |
2074 | fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> { | |
2075 | self[..].strip_suffix_of(haystack) | |
2076 | } | |
c34b1796 AL |
2077 | } |
2078 | ||
85aaf69f | 2079 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
2080 | impl PartialEq for String { |
2081 | #[inline] | |
92a42be0 SL |
2082 | fn eq(&self, other: &String) -> bool { |
2083 | PartialEq::eq(&self[..], &other[..]) | |
2084 | } | |
1a4d82fc | 2085 | #[inline] |
92a42be0 SL |
2086 | fn ne(&self, other: &String) -> bool { |
2087 | PartialEq::ne(&self[..], &other[..]) | |
2088 | } | |
1a4d82fc JJ |
2089 | } |
2090 | ||
2091 | macro_rules! impl_eq { | |
2092 | ($lhs:ty, $rhs: ty) => { | |
85aaf69f | 2093 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 2094 | #[allow(unused_lifetimes)] |
92a42be0 | 2095 | impl<'a, 'b> PartialEq<$rhs> for $lhs { |
1a4d82fc | 2096 | #[inline] |
dfeec247 XL |
2097 | fn eq(&self, other: &$rhs) -> bool { |
2098 | PartialEq::eq(&self[..], &other[..]) | |
2099 | } | |
1a4d82fc | 2100 | #[inline] |
dfeec247 XL |
2101 | fn ne(&self, other: &$rhs) -> bool { |
2102 | PartialEq::ne(&self[..], &other[..]) | |
2103 | } | |
1a4d82fc JJ |
2104 | } |
2105 | ||
85aaf69f | 2106 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 2107 | #[allow(unused_lifetimes)] |
92a42be0 | 2108 | impl<'a, 'b> PartialEq<$lhs> for $rhs { |
1a4d82fc | 2109 | #[inline] |
dfeec247 XL |
2110 | fn eq(&self, other: &$lhs) -> bool { |
2111 | PartialEq::eq(&self[..], &other[..]) | |
2112 | } | |
1a4d82fc | 2113 | #[inline] |
dfeec247 XL |
2114 | fn ne(&self, other: &$lhs) -> bool { |
2115 | PartialEq::ne(&self[..], &other[..]) | |
2116 | } | |
1a4d82fc | 2117 | } |
dfeec247 | 2118 | }; |
1a4d82fc JJ |
2119 | } |
2120 | ||
9346a6ac | 2121 | impl_eq! { String, str } |
1a4d82fc | 2122 | impl_eq! { String, &'a str } |
17df50a5 | 2123 | #[cfg(not(no_global_oom_handling))] |
9346a6ac | 2124 | impl_eq! { Cow<'a, str>, str } |
17df50a5 | 2125 | #[cfg(not(no_global_oom_handling))] |
92a42be0 | 2126 | impl_eq! { Cow<'a, str>, &'b str } |
17df50a5 | 2127 | #[cfg(not(no_global_oom_handling))] |
85aaf69f | 2128 | impl_eq! { Cow<'a, str>, String } |
1a4d82fc | 2129 | |
85aaf69f | 2130 | #[stable(feature = "rust1", since = "1.0.0")] |
94222f64 XL |
2131 | #[rustc_const_unstable(feature = "const_default_impls", issue = "87864")] |
2132 | impl const Default for String { | |
9e0c209e | 2133 | /// Creates an empty `String`. |
85aaf69f | 2134 | #[inline] |
1a4d82fc JJ |
2135 | fn default() -> String { |
2136 | String::new() | |
2137 | } | |
2138 | } | |
2139 | ||
85aaf69f SL |
2140 | #[stable(feature = "rust1", since = "1.0.0")] |
2141 | impl fmt::Display for String { | |
2142 | #[inline] | |
9fa01778 | 2143 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 2144 | fmt::Display::fmt(&**self, f) |
1a4d82fc JJ |
2145 | } |
2146 | } | |
2147 | ||
85aaf69f SL |
2148 | #[stable(feature = "rust1", since = "1.0.0")] |
2149 | impl fmt::Debug for String { | |
2150 | #[inline] | |
9fa01778 | 2151 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 2152 | fmt::Debug::fmt(&**self, f) |
1a4d82fc JJ |
2153 | } |
2154 | } | |
2155 | ||
85aaf69f | 2156 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 2157 | impl hash::Hash for String { |
1a4d82fc | 2158 | #[inline] |
85aaf69f | 2159 | fn hash<H: hash::Hasher>(&self, hasher: &mut H) { |
1a4d82fc JJ |
2160 | (**self).hash(hasher) |
2161 | } | |
2162 | } | |
2163 | ||
8bb4bdeb XL |
2164 | /// Implements the `+` operator for concatenating two strings. |
2165 | /// | |
2166 | /// This consumes the `String` on the left-hand side and re-uses its buffer (growing it if | |
2167 | /// necessary). This is done to avoid allocating a new `String` and copying the entire contents on | |
3dfed10e | 2168 | /// every operation, which would lead to *O*(*n*^2) running time when building an *n*-byte string by |
8bb4bdeb XL |
2169 | /// repeated concatenation. |
2170 | /// | |
2171 | /// The string on the right-hand side is only borrowed; its contents are copied into the returned | |
2172 | /// `String`. | |
2173 | /// | |
2174 | /// # Examples | |
2175 | /// | |
2176 | /// Concatenating two `String`s takes the first by value and borrows the second: | |
2177 | /// | |
2178 | /// ``` | |
2179 | /// let a = String::from("hello"); | |
2180 | /// let b = String::from(" world"); | |
2181 | /// let c = a + &b; | |
2182 | /// // `a` is moved and can no longer be used here. | |
2183 | /// ``` | |
2184 | /// | |
2185 | /// If you want to keep using the first `String`, you can clone it and append to the clone instead: | |
2186 | /// | |
2187 | /// ``` | |
2188 | /// let a = String::from("hello"); | |
2189 | /// let b = String::from(" world"); | |
2190 | /// let c = a.clone() + &b; | |
2191 | /// // `a` is still valid here. | |
2192 | /// ``` | |
2193 | /// | |
2194 | /// Concatenating `&str` slices can be done by converting the first to a `String`: | |
2195 | /// | |
2196 | /// ``` | |
2197 | /// let a = "hello"; | |
2198 | /// let b = " world"; | |
2199 | /// let c = a.to_string() + b; | |
2200 | /// ``` | |
17df50a5 | 2201 | #[cfg(not(no_global_oom_handling))] |
bd371182 | 2202 | #[stable(feature = "rust1", since = "1.0.0")] |
9fa01778 | 2203 | impl Add<&str> for String { |
1a4d82fc JJ |
2204 | type Output = String; |
2205 | ||
85aaf69f | 2206 | #[inline] |
1a4d82fc JJ |
2207 | fn add(mut self, other: &str) -> String { |
2208 | self.push_str(other); | |
2209 | self | |
2210 | } | |
2211 | } | |
2212 | ||
8bb4bdeb XL |
2213 | /// Implements the `+=` operator for appending to a `String`. |
2214 | /// | |
b7449926 | 2215 | /// This has the same behavior as the [`push_str`][String::push_str] method. |
17df50a5 | 2216 | #[cfg(not(no_global_oom_handling))] |
5bcae85e | 2217 | #[stable(feature = "stringaddassign", since = "1.12.0")] |
9fa01778 | 2218 | impl AddAssign<&str> for String { |
5bcae85e SL |
2219 | #[inline] |
2220 | fn add_assign(&mut self, other: &str) { | |
2221 | self.push_str(other); | |
2222 | } | |
2223 | } | |
2224 | ||
85aaf69f SL |
2225 | #[stable(feature = "rust1", since = "1.0.0")] |
2226 | impl ops::Index<ops::Range<usize>> for String { | |
1a4d82fc | 2227 | type Output = str; |
c34b1796 | 2228 | |
1a4d82fc | 2229 | #[inline] |
c34b1796 AL |
2230 | fn index(&self, index: ops::Range<usize>) -> &str { |
2231 | &self[..][index] | |
1a4d82fc JJ |
2232 | } |
2233 | } | |
85aaf69f SL |
2234 | #[stable(feature = "rust1", since = "1.0.0")] |
2235 | impl ops::Index<ops::RangeTo<usize>> for String { | |
1a4d82fc | 2236 | type Output = str; |
c34b1796 | 2237 | |
1a4d82fc | 2238 | #[inline] |
c34b1796 AL |
2239 | fn index(&self, index: ops::RangeTo<usize>) -> &str { |
2240 | &self[..][index] | |
1a4d82fc JJ |
2241 | } |
2242 | } | |
85aaf69f SL |
2243 | #[stable(feature = "rust1", since = "1.0.0")] |
2244 | impl ops::Index<ops::RangeFrom<usize>> for String { | |
1a4d82fc | 2245 | type Output = str; |
c34b1796 | 2246 | |
1a4d82fc | 2247 | #[inline] |
c34b1796 AL |
2248 | fn index(&self, index: ops::RangeFrom<usize>) -> &str { |
2249 | &self[..][index] | |
1a4d82fc JJ |
2250 | } |
2251 | } | |
85aaf69f SL |
2252 | #[stable(feature = "rust1", since = "1.0.0")] |
2253 | impl ops::Index<ops::RangeFull> for String { | |
1a4d82fc | 2254 | type Output = str; |
c34b1796 | 2255 | |
1a4d82fc | 2256 | #[inline] |
c34b1796 | 2257 | fn index(&self, _index: ops::RangeFull) -> &str { |
e9174d1e | 2258 | unsafe { str::from_utf8_unchecked(&self.vec) } |
1a4d82fc JJ |
2259 | } |
2260 | } | |
0531ce1d | 2261 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2262 | impl ops::Index<ops::RangeInclusive<usize>> for String { |
2263 | type Output = str; | |
2264 | ||
2265 | #[inline] | |
2266 | fn index(&self, index: ops::RangeInclusive<usize>) -> &str { | |
2267 | Index::index(&**self, index) | |
2268 | } | |
2269 | } | |
0531ce1d | 2270 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2271 | impl ops::Index<ops::RangeToInclusive<usize>> for String { |
2272 | type Output = str; | |
2273 | ||
2274 | #[inline] | |
2275 | fn index(&self, index: ops::RangeToInclusive<usize>) -> &str { | |
2276 | Index::index(&**self, index) | |
2277 | } | |
2278 | } | |
1a4d82fc | 2279 | |
7cac9316 | 2280 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2281 | impl ops::IndexMut<ops::Range<usize>> for String { |
2282 | #[inline] | |
2283 | fn index_mut(&mut self, index: ops::Range<usize>) -> &mut str { | |
2284 | &mut self[..][index] | |
2285 | } | |
2286 | } | |
7cac9316 | 2287 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2288 | impl ops::IndexMut<ops::RangeTo<usize>> for String { |
2289 | #[inline] | |
2290 | fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut str { | |
2291 | &mut self[..][index] | |
2292 | } | |
2293 | } | |
7cac9316 | 2294 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2295 | impl ops::IndexMut<ops::RangeFrom<usize>> for String { |
2296 | #[inline] | |
2297 | fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut str { | |
2298 | &mut self[..][index] | |
2299 | } | |
2300 | } | |
7cac9316 | 2301 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2302 | impl ops::IndexMut<ops::RangeFull> for String { |
2303 | #[inline] | |
2304 | fn index_mut(&mut self, _index: ops::RangeFull) -> &mut str { | |
cc61c64b | 2305 | unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) } |
c1a9b12d SL |
2306 | } |
2307 | } | |
0531ce1d | 2308 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2309 | impl ops::IndexMut<ops::RangeInclusive<usize>> for String { |
2310 | #[inline] | |
2311 | fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut str { | |
2312 | IndexMut::index_mut(&mut **self, index) | |
2313 | } | |
2314 | } | |
0531ce1d | 2315 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2316 | impl ops::IndexMut<ops::RangeToInclusive<usize>> for String { |
2317 | #[inline] | |
2318 | fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut str { | |
2319 | IndexMut::index_mut(&mut **self, index) | |
2320 | } | |
2321 | } | |
c1a9b12d | 2322 | |
85aaf69f | 2323 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
2324 | impl ops::Deref for String { |
2325 | type Target = str; | |
2326 | ||
85aaf69f SL |
2327 | #[inline] |
2328 | fn deref(&self) -> &str { | |
e9174d1e | 2329 | unsafe { str::from_utf8_unchecked(&self.vec) } |
1a4d82fc JJ |
2330 | } |
2331 | } | |
2332 | ||
7cac9316 | 2333 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d | 2334 | impl ops::DerefMut for String { |
85aaf69f | 2335 | #[inline] |
c1a9b12d | 2336 | fn deref_mut(&mut self) -> &mut str { |
cc61c64b | 2337 | unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) } |
1a4d82fc JJ |
2338 | } |
2339 | } | |
2340 | ||
74b04a01 | 2341 | /// A type alias for [`Infallible`]. |
92a42be0 | 2342 | /// |
74b04a01 | 2343 | /// This alias exists for backwards compatibility, and may be eventually deprecated. |
92a42be0 | 2344 | /// |
c295e0f8 | 2345 | /// [`Infallible`]: core::convert::Infallible "convert::Infallible" |
b039eaaf | 2346 | #[stable(feature = "str_parse_error", since = "1.5.0")] |
9fa01778 | 2347 | pub type ParseError = core::convert::Infallible; |
bd371182 | 2348 | |
17df50a5 | 2349 | #[cfg(not(no_global_oom_handling))] |
bd371182 | 2350 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 2351 | impl FromStr for String { |
9fa01778 | 2352 | type Err = core::convert::Infallible; |
1a4d82fc | 2353 | #[inline] |
74b04a01 | 2354 | fn from_str(s: &str) -> Result<String, Self::Err> { |
62682a34 | 2355 | Ok(String::from(s)) |
1a4d82fc JJ |
2356 | } |
2357 | } | |
2358 | ||
92a42be0 SL |
2359 | /// A trait for converting a value to a `String`. |
2360 | /// | |
2361 | /// This trait is automatically implemented for any type which implements the | |
2362 | /// [`Display`] trait. As such, `ToString` shouldn't be implemented directly: | |
2363 | /// [`Display`] should be implemented instead, and you get the `ToString` | |
2364 | /// implementation for free. | |
2365 | /// | |
3dfed10e | 2366 | /// [`Display`]: fmt::Display |
6a06907d | 2367 | #[cfg_attr(not(test), rustc_diagnostic_item = "ToString")] |
85aaf69f | 2368 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 2369 | pub trait ToString { |
92a42be0 SL |
2370 | /// Converts the given value to a `String`. |
2371 | /// | |
2372 | /// # Examples | |
2373 | /// | |
2374 | /// Basic usage: | |
2375 | /// | |
2376 | /// ``` | |
2377 | /// let i = 5; | |
2378 | /// let five = String::from("5"); | |
2379 | /// | |
2380 | /// assert_eq!(five, i.to_string()); | |
2381 | /// ``` | |
2c00a5a8 | 2382 | #[rustc_conversion_suggestion] |
85aaf69f | 2383 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
2384 | fn to_string(&self) -> String; |
2385 | } | |
2386 | ||
8bb4bdeb XL |
2387 | /// # Panics |
2388 | /// | |
2389 | /// In this implementation, the `to_string` method panics | |
2390 | /// if the `Display` implementation returns an error. | |
2391 | /// This indicates an incorrect `Display` implementation | |
2392 | /// since `fmt::Write for String` never returns an error itself. | |
17df50a5 | 2393 | #[cfg(not(no_global_oom_handling))] |
85aaf69f SL |
2394 | #[stable(feature = "rust1", since = "1.0.0")] |
2395 | impl<T: fmt::Display + ?Sized> ToString for T { | |
3dfed10e | 2396 | // A common guideline is to not inline generic functions. However, |
29967ef6 XL |
2397 | // removing `#[inline]` from this method causes non-negligible regressions. |
2398 | // See <https://github.com/rust-lang/rust/pull/74852>, the last attempt | |
2399 | // to try to remove it. | |
85aaf69f | 2400 | #[inline] |
54a0048b | 2401 | default fn to_string(&self) -> String { |
1a4d82fc | 2402 | let mut buf = String::new(); |
17df50a5 XL |
2403 | let mut formatter = core::fmt::Formatter::new(&mut buf); |
2404 | // Bypass format_args!() to avoid write_str with zero-length strs | |
2405 | fmt::Display::fmt(self, &mut formatter) | |
dfeec247 | 2406 | .expect("a Display implementation returned an error unexpectedly"); |
1a4d82fc JJ |
2407 | buf |
2408 | } | |
2409 | } | |
2410 | ||
17df50a5 | 2411 | #[cfg(not(no_global_oom_handling))] |
f035d41b XL |
2412 | #[stable(feature = "char_to_string_specialization", since = "1.46.0")] |
2413 | impl ToString for char { | |
2414 | #[inline] | |
2415 | fn to_string(&self) -> String { | |
2416 | String::from(self.encode_utf8(&mut [0; 4])) | |
2417 | } | |
2418 | } | |
2419 | ||
17df50a5 XL |
2420 | #[cfg(not(no_global_oom_handling))] |
2421 | #[stable(feature = "u8_to_string_specialization", since = "1.54.0")] | |
2422 | impl ToString for u8 { | |
2423 | #[inline] | |
2424 | fn to_string(&self) -> String { | |
2425 | let mut buf = String::with_capacity(3); | |
2426 | let mut n = *self; | |
2427 | if n >= 10 { | |
2428 | if n >= 100 { | |
2429 | buf.push((b'0' + n / 100) as char); | |
2430 | n %= 100; | |
2431 | } | |
2432 | buf.push((b'0' + n / 10) as char); | |
2433 | n %= 10; | |
2434 | } | |
2435 | buf.push((b'0' + n) as char); | |
2436 | buf | |
2437 | } | |
2438 | } | |
2439 | ||
2440 | #[cfg(not(no_global_oom_handling))] | |
2441 | #[stable(feature = "i8_to_string_specialization", since = "1.54.0")] | |
2442 | impl ToString for i8 { | |
2443 | #[inline] | |
2444 | fn to_string(&self) -> String { | |
2445 | let mut buf = String::with_capacity(4); | |
2446 | if self.is_negative() { | |
2447 | buf.push('-'); | |
2448 | } | |
2449 | let mut n = self.unsigned_abs(); | |
2450 | if n >= 10 { | |
2451 | if n >= 100 { | |
2452 | buf.push('1'); | |
2453 | n -= 100; | |
2454 | } | |
2455 | buf.push((b'0' + n / 10) as char); | |
2456 | n %= 10; | |
2457 | } | |
2458 | buf.push((b'0' + n) as char); | |
2459 | buf | |
2460 | } | |
2461 | } | |
2462 | ||
2463 | #[cfg(not(no_global_oom_handling))] | |
54a0048b SL |
2464 | #[stable(feature = "str_to_string_specialization", since = "1.9.0")] |
2465 | impl ToString for str { | |
2466 | #[inline] | |
2467 | fn to_string(&self) -> String { | |
2468 | String::from(self) | |
2469 | } | |
2470 | } | |
2471 | ||
17df50a5 | 2472 | #[cfg(not(no_global_oom_handling))] |
8bb4bdeb | 2473 | #[stable(feature = "cow_str_to_string_specialization", since = "1.17.0")] |
9fa01778 | 2474 | impl ToString for Cow<'_, str> { |
8bb4bdeb XL |
2475 | #[inline] |
2476 | fn to_string(&self) -> String { | |
2477 | self[..].to_owned() | |
2478 | } | |
2479 | } | |
2480 | ||
17df50a5 | 2481 | #[cfg(not(no_global_oom_handling))] |
8bb4bdeb XL |
2482 | #[stable(feature = "string_to_string_specialization", since = "1.17.0")] |
2483 | impl ToString for String { | |
2484 | #[inline] | |
2485 | fn to_string(&self) -> String { | |
2486 | self.to_owned() | |
2487 | } | |
2488 | } | |
2489 | ||
85aaf69f | 2490 | #[stable(feature = "rust1", since = "1.0.0")] |
c34b1796 | 2491 | impl AsRef<str> for String { |
d9579d0f | 2492 | #[inline] |
c34b1796 AL |
2493 | fn as_ref(&self) -> &str { |
2494 | self | |
2495 | } | |
2496 | } | |
2497 | ||
74b04a01 XL |
2498 | #[stable(feature = "string_as_mut", since = "1.43.0")] |
2499 | impl AsMut<str> for String { | |
2500 | #[inline] | |
2501 | fn as_mut(&mut self) -> &mut str { | |
2502 | self | |
2503 | } | |
2504 | } | |
2505 | ||
bd371182 AL |
2506 | #[stable(feature = "rust1", since = "1.0.0")] |
2507 | impl AsRef<[u8]> for String { | |
2508 | #[inline] | |
2509 | fn as_ref(&self) -> &[u8] { | |
2510 | self.as_bytes() | |
2511 | } | |
2512 | } | |
2513 | ||
17df50a5 | 2514 | #[cfg(not(no_global_oom_handling))] |
c34b1796 | 2515 | #[stable(feature = "rust1", since = "1.0.0")] |
532ac7d7 | 2516 | impl From<&str> for String { |
17df50a5 XL |
2517 | /// Converts a `&str` into a [`String`]. |
2518 | /// | |
2519 | /// The result is allocated on the heap. | |
0bf4aa26 | 2520 | #[inline] |
532ac7d7 | 2521 | fn from(s: &str) -> String { |
54a0048b | 2522 | s.to_owned() |
c34b1796 AL |
2523 | } |
2524 | } | |
2525 | ||
17df50a5 | 2526 | #[cfg(not(no_global_oom_handling))] |
ba9703b0 XL |
2527 | #[stable(feature = "from_mut_str_for_string", since = "1.44.0")] |
2528 | impl From<&mut str> for String { | |
17df50a5 | 2529 | /// Converts a `&mut str` into a [`String`]. |
ba9703b0 XL |
2530 | /// |
2531 | /// The result is allocated on the heap. | |
2532 | #[inline] | |
2533 | fn from(s: &mut str) -> String { | |
2534 | s.to_owned() | |
2535 | } | |
2536 | } | |
2537 | ||
17df50a5 | 2538 | #[cfg(not(no_global_oom_handling))] |
48663c56 XL |
2539 | #[stable(feature = "from_ref_string", since = "1.35.0")] |
2540 | impl From<&String> for String { | |
17df50a5 XL |
2541 | /// Converts a `&String` into a [`String`]. |
2542 | /// | |
2543 | /// This clones `s` and returns the clone. | |
48663c56 XL |
2544 | #[inline] |
2545 | fn from(s: &String) -> String { | |
2546 | s.clone() | |
2547 | } | |
2548 | } | |
2549 | ||
cc61c64b XL |
2550 | // note: test pulls in libstd, which causes errors here |
2551 | #[cfg(not(test))] | |
7cac9316 | 2552 | #[stable(feature = "string_from_box", since = "1.18.0")] |
cc61c64b | 2553 | impl From<Box<str>> for String { |
17df50a5 | 2554 | /// Converts the given boxed `str` slice to a [`String`]. |
a1dfa0c6 XL |
2555 | /// It is notable that the `str` slice is owned. |
2556 | /// | |
2557 | /// # Examples | |
2558 | /// | |
2559 | /// Basic usage: | |
2560 | /// | |
2561 | /// ``` | |
2562 | /// let s1: String = String::from("hello world"); | |
2563 | /// let s2: Box<str> = s1.into_boxed_str(); | |
2564 | /// let s3: String = String::from(s2); | |
2565 | /// | |
2566 | /// assert_eq!("hello world", s3) | |
2567 | /// ``` | |
cc61c64b XL |
2568 | fn from(s: Box<str>) -> String { |
2569 | s.into_string() | |
2570 | } | |
2571 | } | |
2572 | ||
17df50a5 | 2573 | #[cfg(not(no_global_oom_handling))] |
041b39d2 XL |
2574 | #[stable(feature = "box_from_str", since = "1.20.0")] |
2575 | impl From<String> for Box<str> { | |
17df50a5 | 2576 | /// Converts the given [`String`] to a boxed `str` slice that is owned. |
a1dfa0c6 XL |
2577 | /// |
2578 | /// # Examples | |
2579 | /// | |
2580 | /// Basic usage: | |
2581 | /// | |
2582 | /// ``` | |
2583 | /// let s1: String = String::from("hello world"); | |
2584 | /// let s2: Box<str> = Box::from(s1); | |
2585 | /// let s3: String = String::from(s2); | |
2586 | /// | |
2587 | /// assert_eq!("hello world", s3) | |
2588 | /// ``` | |
041b39d2 XL |
2589 | fn from(s: String) -> Box<str> { |
2590 | s.into_boxed_str() | |
cc61c64b XL |
2591 | } |
2592 | } | |
2593 | ||
17df50a5 | 2594 | #[cfg(not(no_global_oom_handling))] |
c30ab7b3 SL |
2595 | #[stable(feature = "string_from_cow_str", since = "1.14.0")] |
2596 | impl<'a> From<Cow<'a, str>> for String { | |
17df50a5 XL |
2597 | /// Converts a clone-on-write string to an owned |
2598 | /// instance of [`String`]. | |
2599 | /// | |
2600 | /// This extracts the owned string, | |
2601 | /// clones the string if it is not already owned. | |
2602 | /// | |
2603 | /// # Example | |
2604 | /// | |
2605 | /// ``` | |
2606 | /// # use std::borrow::Cow; | |
2607 | /// // If the string is not owned... | |
2608 | /// let cow: Cow<str> = Cow::Borrowed("eggplant"); | |
2609 | /// // It will allocate on the heap and copy the string. | |
2610 | /// let owned: String = String::from(cow); | |
2611 | /// assert_eq!(&owned[..], "eggplant"); | |
2612 | /// ``` | |
c30ab7b3 SL |
2613 | fn from(s: Cow<'a, str>) -> String { |
2614 | s.into_owned() | |
2615 | } | |
2616 | } | |
2617 | ||
17df50a5 | 2618 | #[cfg(not(no_global_oom_handling))] |
c34b1796 AL |
2619 | #[stable(feature = "rust1", since = "1.0.0")] |
2620 | impl<'a> From<&'a str> for Cow<'a, str> { | |
17df50a5 | 2621 | /// Converts a string slice into a [`Borrowed`] variant. |
6a06907d XL |
2622 | /// No heap allocation is performed, and the string |
2623 | /// is not copied. | |
2624 | /// | |
2625 | /// # Example | |
2626 | /// | |
2627 | /// ``` | |
2628 | /// # use std::borrow::Cow; | |
2629 | /// assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant")); | |
2630 | /// ``` | |
17df50a5 | 2631 | /// |
c295e0f8 | 2632 | /// [`Borrowed`]: crate::borrow::Cow::Borrowed "borrow::Cow::Borrowed" |
c34b1796 AL |
2633 | #[inline] |
2634 | fn from(s: &'a str) -> Cow<'a, str> { | |
2635 | Cow::Borrowed(s) | |
2636 | } | |
2637 | } | |
2638 | ||
17df50a5 | 2639 | #[cfg(not(no_global_oom_handling))] |
c34b1796 AL |
2640 | #[stable(feature = "rust1", since = "1.0.0")] |
2641 | impl<'a> From<String> for Cow<'a, str> { | |
17df50a5 | 2642 | /// Converts a [`String`] into an [`Owned`] variant. |
6a06907d XL |
2643 | /// No heap allocation is performed, and the string |
2644 | /// is not copied. | |
2645 | /// | |
2646 | /// # Example | |
2647 | /// | |
2648 | /// ``` | |
2649 | /// # use std::borrow::Cow; | |
2650 | /// let s = "eggplant".to_string(); | |
2651 | /// let s2 = "eggplant".to_string(); | |
2652 | /// assert_eq!(Cow::from(s), Cow::<'static, str>::Owned(s2)); | |
2653 | /// ``` | |
17df50a5 | 2654 | /// |
c295e0f8 | 2655 | /// [`Owned`]: crate::borrow::Cow::Owned "borrow::Cow::Owned" |
c34b1796 AL |
2656 | #[inline] |
2657 | fn from(s: String) -> Cow<'a, str> { | |
2658 | Cow::Owned(s) | |
2659 | } | |
2660 | } | |
2661 | ||
17df50a5 | 2662 | #[cfg(not(no_global_oom_handling))] |
94b46f34 XL |
2663 | #[stable(feature = "cow_from_string_ref", since = "1.28.0")] |
2664 | impl<'a> From<&'a String> for Cow<'a, str> { | |
17df50a5 | 2665 | /// Converts a [`String`] reference into a [`Borrowed`] variant. |
6a06907d XL |
2666 | /// No heap allocation is performed, and the string |
2667 | /// is not copied. | |
2668 | /// | |
2669 | /// # Example | |
2670 | /// | |
2671 | /// ``` | |
2672 | /// # use std::borrow::Cow; | |
2673 | /// let s = "eggplant".to_string(); | |
2674 | /// assert_eq!(Cow::from(&s), Cow::Borrowed("eggplant")); | |
2675 | /// ``` | |
17df50a5 | 2676 | /// |
c295e0f8 | 2677 | /// [`Borrowed`]: crate::borrow::Cow::Borrowed "borrow::Cow::Borrowed" |
94b46f34 XL |
2678 | #[inline] |
2679 | fn from(s: &'a String) -> Cow<'a, str> { | |
2680 | Cow::Borrowed(s.as_str()) | |
2681 | } | |
2682 | } | |
2683 | ||
17df50a5 | 2684 | #[cfg(not(no_global_oom_handling))] |
5bcae85e SL |
2685 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] |
2686 | impl<'a> FromIterator<char> for Cow<'a, str> { | |
2687 | fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> { | |
2688 | Cow::Owned(FromIterator::from_iter(it)) | |
2689 | } | |
2690 | } | |
2691 | ||
17df50a5 | 2692 | #[cfg(not(no_global_oom_handling))] |
5bcae85e SL |
2693 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] |
2694 | impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str> { | |
2695 | fn from_iter<I: IntoIterator<Item = &'b str>>(it: I) -> Cow<'a, str> { | |
2696 | Cow::Owned(FromIterator::from_iter(it)) | |
2697 | } | |
2698 | } | |
2699 | ||
17df50a5 | 2700 | #[cfg(not(no_global_oom_handling))] |
5bcae85e SL |
2701 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] |
2702 | impl<'a> FromIterator<String> for Cow<'a, str> { | |
2703 | fn from_iter<I: IntoIterator<Item = String>>(it: I) -> Cow<'a, str> { | |
2704 | Cow::Owned(FromIterator::from_iter(it)) | |
2705 | } | |
2706 | } | |
2707 | ||
c30ab7b3 SL |
2708 | #[stable(feature = "from_string_for_vec_u8", since = "1.14.0")] |
2709 | impl From<String> for Vec<u8> { | |
17df50a5 | 2710 | /// Converts the given [`String`] to a vector [`Vec`] that holds values of type [`u8`]. |
a1dfa0c6 XL |
2711 | /// |
2712 | /// # Examples | |
2713 | /// | |
2714 | /// Basic usage: | |
2715 | /// | |
2716 | /// ``` | |
2717 | /// let s1 = String::from("hello world"); | |
2718 | /// let v1 = Vec::from(s1); | |
2719 | /// | |
2720 | /// for b in v1 { | |
2721 | /// println!("{}", b); | |
2722 | /// } | |
2723 | /// ``` | |
32a655c1 | 2724 | fn from(string: String) -> Vec<u8> { |
c30ab7b3 | 2725 | string.into_bytes() |
c34b1796 AL |
2726 | } |
2727 | } | |
2728 | ||
17df50a5 | 2729 | #[cfg(not(no_global_oom_handling))] |
85aaf69f SL |
2730 | #[stable(feature = "rust1", since = "1.0.0")] |
2731 | impl fmt::Write for String { | |
2732 | #[inline] | |
1a4d82fc JJ |
2733 | fn write_str(&mut self, s: &str) -> fmt::Result { |
2734 | self.push_str(s); | |
2735 | Ok(()) | |
2736 | } | |
d9579d0f AL |
2737 | |
2738 | #[inline] | |
2739 | fn write_char(&mut self, c: char) -> fmt::Result { | |
2740 | self.push(c); | |
2741 | Ok(()) | |
2742 | } | |
2743 | } | |
2744 | ||
2745 | /// A draining iterator for `String`. | |
7453a54e | 2746 | /// |
cc61c64b | 2747 | /// This struct is created by the [`drain`] method on [`String`]. See its |
7453a54e SL |
2748 | /// documentation for more. |
2749 | /// | |
3dfed10e | 2750 | /// [`drain`]: String::drain |
92a42be0 | 2751 | #[stable(feature = "drain", since = "1.6.0")] |
d9579d0f AL |
2752 | pub struct Drain<'a> { |
2753 | /// Will be used as &'a mut String in the destructor | |
2754 | string: *mut String, | |
2755 | /// Start of part to remove | |
2756 | start: usize, | |
2757 | /// End of part to remove | |
2758 | end: usize, | |
2759 | /// Current remaining range to remove | |
2760 | iter: Chars<'a>, | |
2761 | } | |
2762 | ||
8bb4bdeb | 2763 | #[stable(feature = "collection_debug", since = "1.17.0")] |
9fa01778 XL |
2764 | impl fmt::Debug for Drain<'_> { |
2765 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
1b1a35ee | 2766 | f.debug_tuple("Drain").field(&self.as_str()).finish() |
8bb4bdeb XL |
2767 | } |
2768 | } | |
2769 | ||
92a42be0 | 2770 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2771 | unsafe impl Sync for Drain<'_> {} |
92a42be0 | 2772 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2773 | unsafe impl Send for Drain<'_> {} |
d9579d0f | 2774 | |
92a42be0 | 2775 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2776 | impl Drop for Drain<'_> { |
d9579d0f AL |
2777 | fn drop(&mut self) { |
2778 | unsafe { | |
2779 | // Use Vec::drain. "Reaffirm" the bounds checks to avoid | |
2780 | // panic code being inserted again. | |
2781 | let self_vec = (*self.string).as_mut_vec(); | |
2782 | if self.start <= self.end && self.end <= self_vec.len() { | |
2783 | self_vec.drain(self.start..self.end); | |
2784 | } | |
2785 | } | |
2786 | } | |
2787 | } | |
2788 | ||
1b1a35ee XL |
2789 | impl<'a> Drain<'a> { |
2790 | /// Returns the remaining (sub)string of this iterator as a slice. | |
2791 | /// | |
2792 | /// # Examples | |
2793 | /// | |
2794 | /// ``` | |
1b1a35ee XL |
2795 | /// let mut s = String::from("abc"); |
2796 | /// let mut drain = s.drain(..); | |
2797 | /// assert_eq!(drain.as_str(), "abc"); | |
2798 | /// let _ = drain.next().unwrap(); | |
2799 | /// assert_eq!(drain.as_str(), "bc"); | |
2800 | /// ``` | |
c295e0f8 | 2801 | #[must_use] |
136023e0 | 2802 | #[stable(feature = "string_drain_as_str", since = "1.55.0")] |
1b1a35ee XL |
2803 | pub fn as_str(&self) -> &str { |
2804 | self.iter.as_str() | |
2805 | } | |
2806 | } | |
2807 | ||
136023e0 XL |
2808 | #[stable(feature = "string_drain_as_str", since = "1.55.0")] |
2809 | impl<'a> AsRef<str> for Drain<'a> { | |
2810 | fn as_ref(&self) -> &str { | |
2811 | self.as_str() | |
2812 | } | |
2813 | } | |
2814 | ||
2815 | #[stable(feature = "string_drain_as_str", since = "1.55.0")] | |
2816 | impl<'a> AsRef<[u8]> for Drain<'a> { | |
2817 | fn as_ref(&self) -> &[u8] { | |
2818 | self.as_str().as_bytes() | |
2819 | } | |
2820 | } | |
1b1a35ee | 2821 | |
92a42be0 | 2822 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2823 | impl Iterator for Drain<'_> { |
d9579d0f AL |
2824 | type Item = char; |
2825 | ||
2826 | #[inline] | |
2827 | fn next(&mut self) -> Option<char> { | |
2828 | self.iter.next() | |
2829 | } | |
2830 | ||
2831 | fn size_hint(&self) -> (usize, Option<usize>) { | |
2832 | self.iter.size_hint() | |
2833 | } | |
416331ca XL |
2834 | |
2835 | #[inline] | |
2836 | fn last(mut self) -> Option<char> { | |
2837 | self.next_back() | |
2838 | } | |
d9579d0f AL |
2839 | } |
2840 | ||
92a42be0 | 2841 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2842 | impl DoubleEndedIterator for Drain<'_> { |
d9579d0f AL |
2843 | #[inline] |
2844 | fn next_back(&mut self) -> Option<char> { | |
2845 | self.iter.next_back() | |
2846 | } | |
1a4d82fc | 2847 | } |
9e0c209e | 2848 | |
0531ce1d | 2849 | #[stable(feature = "fused", since = "1.26.0")] |
9fa01778 | 2850 | impl FusedIterator for Drain<'_> {} |
f035d41b | 2851 | |
17df50a5 | 2852 | #[cfg(not(no_global_oom_handling))] |
f035d41b XL |
2853 | #[stable(feature = "from_char_for_string", since = "1.46.0")] |
2854 | impl From<char> for String { | |
17df50a5 XL |
2855 | /// Allocates an owned [`String`] from a single character. |
2856 | /// | |
2857 | /// # Example | |
2858 | /// ```rust | |
2859 | /// let c: char = 'a'; | |
2860 | /// let s: String = String::from(c); | |
2861 | /// assert_eq!("a", &s[..]); | |
2862 | /// ``` | |
f035d41b XL |
2863 | #[inline] |
2864 | fn from(c: char) -> Self { | |
2865 | c.to_string() | |
2866 | } | |
2867 | } |