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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 | |
83c7162d | 45 | use core::char::{decode_utf16, REPLACEMENT_CHARACTER}; |
1a4d82fc JJ |
46 | use core::fmt; |
47 | use core::hash; | |
9e0c209e | 48 | use core::iter::{FromIterator, FusedIterator}; |
9fa01778 | 49 | use core::ops::Bound::{Excluded, Included, Unbounded}; |
1b1a35ee | 50 | use core::ops::{self, Add, AddAssign, Index, IndexMut, Range, RangeBounds}; |
1a4d82fc | 51 | use core::ptr; |
dfeec247 | 52 | use core::str::{lossy, pattern::Pattern}; |
1a4d82fc | 53 | |
9fa01778 | 54 | use crate::borrow::{Cow, ToOwned}; |
9fa01778 | 55 | use crate::boxed::Box; |
dfeec247 XL |
56 | use crate::collections::TryReserveError; |
57 | use crate::str::{self, from_boxed_utf8_unchecked, Chars, FromStr, Utf8Error}; | |
9fa01778 | 58 | use crate::vec::Vec; |
1a4d82fc | 59 | |
29967ef6 | 60 | /// A UTF-8–encoded, growable string. |
92a42be0 SL |
61 | /// |
62 | /// The `String` type is the most common string type that has ownership over the | |
63 | /// contents of the string. It has a close relationship with its borrowed | |
64 | /// counterpart, the primitive [`str`]. | |
65 | /// | |
92a42be0 SL |
66 | /// # Examples |
67 | /// | |
3dfed10e XL |
68 | /// You can create a `String` from [a literal string][`str`] with [`String::from`]: |
69 | /// | |
70 | /// [`String::from`]: From::from | |
92a42be0 SL |
71 | /// |
72 | /// ``` | |
73 | /// let hello = String::from("Hello, world!"); | |
74 | /// ``` | |
75 | /// | |
cc61c64b XL |
76 | /// You can append a [`char`] to a `String` with the [`push`] method, and |
77 | /// append a [`&str`] with the [`push_str`] method: | |
92a42be0 SL |
78 | /// |
79 | /// ``` | |
80 | /// let mut hello = String::from("Hello, "); | |
81 | /// | |
82 | /// hello.push('w'); | |
83 | /// hello.push_str("orld!"); | |
84 | /// ``` | |
85 | /// | |
3dfed10e XL |
86 | /// [`push`]: String::push |
87 | /// [`push_str`]: String::push_str | |
92a42be0 SL |
88 | /// |
89 | /// If you have a vector of UTF-8 bytes, you can create a `String` from it with | |
cc61c64b | 90 | /// the [`from_utf8`] method: |
92a42be0 SL |
91 | /// |
92 | /// ``` | |
93 | /// // some bytes, in a vector | |
94 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
95 | /// | |
96 | /// // We know these bytes are valid, so we'll use `unwrap()`. | |
97 | /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); | |
98 | /// | |
99 | /// assert_eq!("💖", sparkle_heart); | |
100 | /// ``` | |
101 | /// | |
3dfed10e | 102 | /// [`from_utf8`]: String::from_utf8 |
92a42be0 SL |
103 | /// |
104 | /// # UTF-8 | |
105 | /// | |
106 | /// `String`s are always valid UTF-8. This has a few implications, the first of | |
107 | /// which is that if you need a non-UTF-8 string, consider [`OsString`]. It is | |
108 | /// similar, but without the UTF-8 constraint. The second implication is that | |
109 | /// you cannot index into a `String`: | |
110 | /// | |
041b39d2 | 111 | /// ```compile_fail,E0277 |
92a42be0 SL |
112 | /// let s = "hello"; |
113 | /// | |
114 | /// println!("The first letter of s is {}", s[0]); // ERROR!!! | |
115 | /// ``` | |
116 | /// | |
54a0048b | 117 | /// [`OsString`]: ../../std/ffi/struct.OsString.html |
92a42be0 SL |
118 | /// |
119 | /// Indexing is intended to be a constant-time operation, but UTF-8 encoding | |
9e0c209e | 120 | /// does not allow us to do this. Furthermore, it's not clear what sort of |
92a42be0 | 121 | /// thing the index should return: a byte, a codepoint, or a grapheme cluster. |
cc61c64b | 122 | /// The [`bytes`] and [`chars`] methods return iterators over the first |
92a42be0 SL |
123 | /// two, respectively. |
124 | /// | |
3dfed10e XL |
125 | /// [`bytes`]: str::bytes |
126 | /// [`chars`]: str::chars | |
92a42be0 SL |
127 | /// |
128 | /// # Deref | |
129 | /// | |
130 | /// `String`s implement [`Deref`]`<Target=str>`, and so inherit all of [`str`]'s | |
3b2f2976 | 131 | /// methods. In addition, this means that you can pass a `String` to a |
92a42be0 SL |
132 | /// function which takes a [`&str`] by using an ampersand (`&`): |
133 | /// | |
134 | /// ``` | |
135 | /// fn takes_str(s: &str) { } | |
136 | /// | |
137 | /// let s = String::from("Hello"); | |
138 | /// | |
139 | /// takes_str(&s); | |
140 | /// ``` | |
141 | /// | |
92a42be0 SL |
142 | /// This will create a [`&str`] from the `String` and pass it in. This |
143 | /// conversion is very inexpensive, and so generally, functions will accept | |
3b2f2976 XL |
144 | /// [`&str`]s as arguments unless they need a `String` for some specific |
145 | /// reason. | |
146 | /// | |
147 | /// In certain cases Rust doesn't have enough information to make this | |
148 | /// conversion, known as [`Deref`] coercion. In the following example a string | |
149 | /// slice [`&'a str`][`&str`] implements the trait `TraitExample`, and the function | |
150 | /// `example_func` takes anything that implements the trait. In this case Rust | |
151 | /// would need to make two implicit conversions, which Rust doesn't have the | |
152 | /// means to do. For that reason, the following example will not compile. | |
153 | /// | |
154 | /// ```compile_fail,E0277 | |
155 | /// trait TraitExample {} | |
156 | /// | |
157 | /// impl<'a> TraitExample for &'a str {} | |
92a42be0 | 158 | /// |
3b2f2976 XL |
159 | /// fn example_func<A: TraitExample>(example_arg: A) {} |
160 | /// | |
e74abb32 XL |
161 | /// let example_string = String::from("example_string"); |
162 | /// example_func(&example_string); | |
3b2f2976 XL |
163 | /// ``` |
164 | /// | |
165 | /// There are two options that would work instead. The first would be to | |
166 | /// change the line `example_func(&example_string);` to | |
167 | /// `example_func(example_string.as_str());`, using the method [`as_str()`] | |
168 | /// to explicitly extract the string slice containing the string. The second | |
169 | /// way changes `example_func(&example_string);` to | |
170 | /// `example_func(&*example_string);`. In this case we are dereferencing a | |
171 | /// `String` to a [`str`][`&str`], then referencing the [`str`][`&str`] back to | |
172 | /// [`&str`]. The second way is more idiomatic, however both work to do the | |
173 | /// conversion explicitly rather than relying on the implicit conversion. | |
92a42be0 SL |
174 | /// |
175 | /// # Representation | |
176 | /// | |
177 | /// A `String` is made up of three components: a pointer to some bytes, a | |
178 | /// length, and a capacity. The pointer points to an internal buffer `String` | |
179 | /// uses to store its data. The length is the number of bytes currently stored | |
180 | /// in the buffer, and the capacity is the size of the buffer in bytes. As such, | |
181 | /// the length will always be less than or equal to the capacity. | |
182 | /// | |
183 | /// This buffer is always stored on the heap. | |
184 | /// | |
cc61c64b | 185 | /// You can look at these with the [`as_ptr`], [`len`], and [`capacity`] |
92a42be0 SL |
186 | /// methods: |
187 | /// | |
188 | /// ``` | |
189 | /// use std::mem; | |
190 | /// | |
191 | /// let story = String::from("Once upon a time..."); | |
192 | /// | |
e74abb32 XL |
193 | // FIXME Update this when vec_into_raw_parts is stabilized |
194 | /// // Prevent automatically dropping the String's data | |
195 | /// let mut story = mem::ManuallyDrop::new(story); | |
196 | /// | |
197 | /// let ptr = story.as_mut_ptr(); | |
92a42be0 SL |
198 | /// let len = story.len(); |
199 | /// let capacity = story.capacity(); | |
200 | /// | |
a7813a04 | 201 | /// // story has nineteen bytes |
92a42be0 SL |
202 | /// assert_eq!(19, len); |
203 | /// | |
92a42be0 | 204 | /// // We can re-build a String out of ptr, len, and capacity. This is all |
7453a54e | 205 | /// // unsafe because we are responsible for making sure the components are |
92a42be0 | 206 | /// // valid: |
e74abb32 | 207 | /// let s = unsafe { String::from_raw_parts(ptr, len, capacity) } ; |
92a42be0 SL |
208 | /// |
209 | /// assert_eq!(String::from("Once upon a time..."), s); | |
210 | /// ``` | |
211 | /// | |
3dfed10e XL |
212 | /// [`as_ptr`]: str::as_ptr |
213 | /// [`len`]: String::len | |
214 | /// [`capacity`]: String::capacity | |
92a42be0 SL |
215 | /// |
216 | /// If a `String` has enough capacity, adding elements to it will not | |
217 | /// re-allocate. For example, consider this program: | |
218 | /// | |
219 | /// ``` | |
220 | /// let mut s = String::new(); | |
221 | /// | |
222 | /// println!("{}", s.capacity()); | |
223 | /// | |
224 | /// for _ in 0..5 { | |
225 | /// s.push_str("hello"); | |
226 | /// println!("{}", s.capacity()); | |
227 | /// } | |
228 | /// ``` | |
229 | /// | |
230 | /// This will output the following: | |
231 | /// | |
232 | /// ```text | |
233 | /// 0 | |
234 | /// 5 | |
235 | /// 10 | |
236 | /// 20 | |
237 | /// 20 | |
238 | /// 40 | |
239 | /// ``` | |
240 | /// | |
241 | /// At first, we have no memory allocated at all, but as we append to the | |
242 | /// string, it increases its capacity appropriately. If we instead use the | |
cc61c64b | 243 | /// [`with_capacity`] method to allocate the correct capacity initially: |
92a42be0 SL |
244 | /// |
245 | /// ``` | |
246 | /// let mut s = String::with_capacity(25); | |
247 | /// | |
248 | /// println!("{}", s.capacity()); | |
249 | /// | |
250 | /// for _ in 0..5 { | |
251 | /// s.push_str("hello"); | |
252 | /// println!("{}", s.capacity()); | |
253 | /// } | |
254 | /// ``` | |
255 | /// | |
3dfed10e | 256 | /// [`with_capacity`]: String::with_capacity |
92a42be0 SL |
257 | /// |
258 | /// We end up with a different output: | |
259 | /// | |
260 | /// ```text | |
261 | /// 25 | |
262 | /// 25 | |
263 | /// 25 | |
264 | /// 25 | |
265 | /// 25 | |
266 | /// 25 | |
267 | /// ``` | |
268 | /// | |
269 | /// Here, there's no need to allocate more memory inside the loop. | |
3b2f2976 | 270 | /// |
3dfed10e XL |
271 | /// [`str`]: prim@str |
272 | /// [`&str`]: prim@str | |
273 | /// [`Deref`]: core::ops::Deref | |
274 | /// [`as_str()`]: String::as_str | |
b039eaaf | 275 | #[derive(PartialOrd, Eq, Ord)] |
f9f354fc | 276 | #[cfg_attr(not(test), rustc_diagnostic_item = "string_type")] |
85aaf69f | 277 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
278 | pub struct String { |
279 | vec: Vec<u8>, | |
280 | } | |
281 | ||
92a42be0 SL |
282 | /// A possible error value when converting a `String` from a UTF-8 byte vector. |
283 | /// | |
cc61c64b | 284 | /// This type is the error type for the [`from_utf8`] method on [`String`]. It |
92a42be0 | 285 | /// is designed in such a way to carefully avoid reallocations: the |
cc61c64b | 286 | /// [`into_bytes`] method will give back the byte vector that was used in the |
92a42be0 SL |
287 | /// conversion attempt. |
288 | /// | |
3dfed10e XL |
289 | /// [`from_utf8`]: String::from_utf8 |
290 | /// [`into_bytes`]: FromUtf8Error::into_bytes | |
92a42be0 SL |
291 | /// |
292 | /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may | |
293 | /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's | |
294 | /// an analogue to `FromUtf8Error`, and you can get one from a `FromUtf8Error` | |
cc61c64b | 295 | /// through the [`utf8_error`] method. |
92a42be0 | 296 | /// |
3dfed10e XL |
297 | /// [`Utf8Error`]: core::str::Utf8Error |
298 | /// [`std::str`]: core::str | |
299 | /// [`&str`]: prim@str | |
300 | /// [`utf8_error`]: Self::utf8_error | |
92a42be0 SL |
301 | /// |
302 | /// # Examples | |
303 | /// | |
304 | /// Basic usage: | |
305 | /// | |
306 | /// ``` | |
307 | /// // some invalid bytes, in a vector | |
308 | /// let bytes = vec![0, 159]; | |
309 | /// | |
310 | /// let value = String::from_utf8(bytes); | |
311 | /// | |
312 | /// assert!(value.is_err()); | |
313 | /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes()); | |
314 | /// ``` | |
85aaf69f | 315 | #[stable(feature = "rust1", since = "1.0.0")] |
74b04a01 | 316 | #[derive(Debug, Clone, PartialEq, Eq)] |
1a4d82fc JJ |
317 | pub struct FromUtf8Error { |
318 | bytes: Vec<u8>, | |
319 | error: Utf8Error, | |
320 | } | |
321 | ||
92a42be0 SL |
322 | /// A possible error value when converting a `String` from a UTF-16 byte slice. |
323 | /// | |
cc61c64b | 324 | /// This type is the error type for the [`from_utf16`] method on [`String`]. |
92a42be0 | 325 | /// |
3dfed10e | 326 | /// [`from_utf16`]: String::from_utf16 |
92a42be0 SL |
327 | /// # Examples |
328 | /// | |
329 | /// Basic usage: | |
330 | /// | |
331 | /// ``` | |
332 | /// // 𝄞mu<invalid>ic | |
333 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, | |
334 | /// 0xD800, 0x0069, 0x0063]; | |
335 | /// | |
336 | /// assert!(String::from_utf16(v).is_err()); | |
337 | /// ``` | |
85aaf69f SL |
338 | #[stable(feature = "rust1", since = "1.0.0")] |
339 | #[derive(Debug)] | |
1a4d82fc JJ |
340 | pub struct FromUtf16Error(()); |
341 | ||
342 | impl String { | |
9cc50fc6 SL |
343 | /// Creates a new empty `String`. |
344 | /// | |
345 | /// Given that the `String` is empty, this will not allocate any initial | |
346 | /// buffer. While that means that this initial operation is very | |
0531ce1d | 347 | /// inexpensive, it may cause excessive allocation later when you add |
9cc50fc6 | 348 | /// data. If you have an idea of how much data the `String` will hold, |
cc61c64b | 349 | /// consider the [`with_capacity`] method to prevent excessive |
9cc50fc6 SL |
350 | /// re-allocation. |
351 | /// | |
3dfed10e | 352 | /// [`with_capacity`]: String::with_capacity |
1a4d82fc JJ |
353 | /// |
354 | /// # Examples | |
355 | /// | |
9cc50fc6 SL |
356 | /// Basic usage: |
357 | /// | |
1a4d82fc | 358 | /// ``` |
9cc50fc6 | 359 | /// let s = String::new(); |
1a4d82fc JJ |
360 | /// ``` |
361 | #[inline] | |
dfeec247 | 362 | #[rustc_const_stable(feature = "const_string_new", since = "1.32.0")] |
85aaf69f | 363 | #[stable(feature = "rust1", since = "1.0.0")] |
94b46f34 | 364 | pub const fn new() -> String { |
92a42be0 | 365 | String { vec: Vec::new() } |
1a4d82fc JJ |
366 | } |
367 | ||
9cc50fc6 SL |
368 | /// Creates a new empty `String` with a particular capacity. |
369 | /// | |
370 | /// `String`s have an internal buffer to hold their data. The capacity is | |
cc61c64b | 371 | /// the length of that buffer, and can be queried with the [`capacity`] |
9cc50fc6 SL |
372 | /// method. This method creates an empty `String`, but one with an initial |
373 | /// buffer that can hold `capacity` bytes. This is useful when you may be | |
374 | /// appending a bunch of data to the `String`, reducing the number of | |
375 | /// reallocations it needs to do. | |
376 | /// | |
3dfed10e | 377 | /// [`capacity`]: String::capacity |
9cc50fc6 SL |
378 | /// |
379 | /// If the given capacity is `0`, no allocation will occur, and this method | |
cc61c64b | 380 | /// is identical to the [`new`] method. |
9cc50fc6 | 381 | /// |
3dfed10e | 382 | /// [`new`]: String::new |
1a4d82fc JJ |
383 | /// |
384 | /// # Examples | |
385 | /// | |
9cc50fc6 SL |
386 | /// Basic usage: |
387 | /// | |
1a4d82fc JJ |
388 | /// ``` |
389 | /// let mut s = String::with_capacity(10); | |
92a42be0 SL |
390 | /// |
391 | /// // The String contains no chars, even though it has capacity for more | |
392 | /// assert_eq!(s.len(), 0); | |
393 | /// | |
394 | /// // These are all done without reallocating... | |
395 | /// let cap = s.capacity(); | |
a1dfa0c6 | 396 | /// for _ in 0..10 { |
92a42be0 SL |
397 | /// s.push('a'); |
398 | /// } | |
399 | /// | |
400 | /// assert_eq!(s.capacity(), cap); | |
401 | /// | |
74b04a01 | 402 | /// // ...but this may make the string reallocate |
92a42be0 | 403 | /// s.push('a'); |
1a4d82fc JJ |
404 | /// ``` |
405 | #[inline] | |
85aaf69f SL |
406 | #[stable(feature = "rust1", since = "1.0.0")] |
407 | pub fn with_capacity(capacity: usize) -> String { | |
92a42be0 | 408 | String { vec: Vec::with_capacity(capacity) } |
1a4d82fc JJ |
409 | } |
410 | ||
c34b1796 AL |
411 | // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is |
412 | // required for this method definition, is not available. Since we don't | |
413 | // require this method for testing purposes, I'll just stub it | |
414 | // NB see the slice::hack module in slice.rs for more information | |
415 | #[inline] | |
416 | #[cfg(test)] | |
417 | pub fn from_str(_: &str) -> String { | |
418 | panic!("not available with cfg(test)"); | |
1a4d82fc JJ |
419 | } |
420 | ||
b039eaaf SL |
421 | /// Converts a vector of bytes to a `String`. |
422 | /// | |
e74abb32 | 423 | /// A string ([`String`]) is made of bytes ([`u8`]), and a vector of bytes |
9cc50fc6 | 424 | /// ([`Vec<u8>`]) is made of bytes, so this function converts between the |
b039eaaf SL |
425 | /// two. Not all byte slices are valid `String`s, however: `String` |
426 | /// requires that it is valid UTF-8. `from_utf8()` checks to ensure that | |
427 | /// the bytes are valid UTF-8, and then does the conversion. | |
428 | /// | |
429 | /// If you are sure that the byte slice is valid UTF-8, and you don't want | |
430 | /// to incur the overhead of the validity check, there is an unsafe version | |
cc61c64b | 431 | /// of this function, [`from_utf8_unchecked`], which has the same behavior |
9cc50fc6 | 432 | /// but skips the check. |
b039eaaf | 433 | /// |
b039eaaf SL |
434 | /// This method will take care to not copy the vector, for efficiency's |
435 | /// sake. | |
436 | /// | |
3b2f2976 | 437 | /// If you need a [`&str`] instead of a `String`, consider |
cc61c64b | 438 | /// [`str::from_utf8`]. |
b039eaaf | 439 | /// |
e74abb32 | 440 | /// The inverse of this method is [`into_bytes`]. |
8bb4bdeb | 441 | /// |
7453a54e | 442 | /// # Errors |
1a4d82fc | 443 | /// |
3b2f2976 | 444 | /// Returns [`Err`] if the slice is not UTF-8 with a description as to why the |
b039eaaf | 445 | /// provided bytes are not UTF-8. The vector you moved in is also included. |
1a4d82fc JJ |
446 | /// |
447 | /// # Examples | |
448 | /// | |
b039eaaf SL |
449 | /// Basic usage: |
450 | /// | |
c34b1796 | 451 | /// ``` |
b039eaaf SL |
452 | /// // some bytes, in a vector |
453 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
454 | /// | |
92a42be0 | 455 | /// // We know these bytes are valid, so we'll use `unwrap()`. |
b039eaaf SL |
456 | /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); |
457 | /// | |
458 | /// assert_eq!("💖", sparkle_heart); | |
459 | /// ``` | |
460 | /// | |
461 | /// Incorrect bytes: | |
462 | /// | |
1a4d82fc | 463 | /// ``` |
b039eaaf SL |
464 | /// // some invalid bytes, in a vector |
465 | /// let sparkle_heart = vec![0, 159, 146, 150]; | |
466 | /// | |
467 | /// assert!(String::from_utf8(sparkle_heart).is_err()); | |
468 | /// ``` | |
469 | /// | |
9cc50fc6 SL |
470 | /// See the docs for [`FromUtf8Error`] for more details on what you can do |
471 | /// with this error. | |
b039eaaf | 472 | /// |
3dfed10e XL |
473 | /// [`from_utf8_unchecked`]: String::from_utf8_unchecked |
474 | /// [`Vec<u8>`]: crate::vec::Vec | |
475 | /// [`&str`]: prim@str | |
476 | /// [`into_bytes`]: String::into_bytes | |
1a4d82fc | 477 | #[inline] |
85aaf69f | 478 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 479 | pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> { |
85aaf69f | 480 | match str::from_utf8(&vec) { |
a1dfa0c6 | 481 | Ok(..) => Ok(String { vec }), |
dfeec247 | 482 | Err(e) => Err(FromUtf8Error { bytes: vec, error: e }), |
1a4d82fc JJ |
483 | } |
484 | } | |
485 | ||
7453a54e | 486 | /// Converts a slice of bytes to a string, including invalid characters. |
b039eaaf | 487 | /// |
7453a54e SL |
488 | /// Strings are made of bytes ([`u8`]), and a slice of bytes |
489 | /// ([`&[u8]`][byteslice]) is made of bytes, so this function converts | |
490 | /// between the two. Not all byte slices are valid strings, however: strings | |
491 | /// are required to be valid UTF-8. During this conversion, | |
9cc50fc6 | 492 | /// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with |
b7449926 | 493 | /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], which looks like this: � |
b039eaaf | 494 | /// |
54a0048b | 495 | /// [byteslice]: ../../std/primitive.slice.html |
3dfed10e | 496 | /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER |
9cc50fc6 | 497 | /// |
b039eaaf SL |
498 | /// If you are sure that the byte slice is valid UTF-8, and you don't want |
499 | /// to incur the overhead of the conversion, there is an unsafe version | |
cc61c64b | 500 | /// of this function, [`from_utf8_unchecked`], which has the same behavior |
9cc50fc6 | 501 | /// but skips the checks. |
b039eaaf | 502 | /// |
3dfed10e | 503 | /// [`from_utf8_unchecked`]: String::from_utf8_unchecked |
b039eaaf | 504 | /// |
7453a54e SL |
505 | /// This function returns a [`Cow<'a, str>`]. If our byte slice is invalid |
506 | /// UTF-8, then we need to insert the replacement characters, which will | |
507 | /// change the size of the string, and hence, require a `String`. But if | |
508 | /// it's already valid UTF-8, we don't need a new allocation. This return | |
509 | /// type allows us to handle both cases. | |
b039eaaf | 510 | /// |
3dfed10e | 511 | /// [`Cow<'a, str>`]: crate::borrow::Cow |
1a4d82fc JJ |
512 | /// |
513 | /// # Examples | |
514 | /// | |
b039eaaf SL |
515 | /// Basic usage: |
516 | /// | |
c34b1796 | 517 | /// ``` |
b039eaaf SL |
518 | /// // some bytes, in a vector |
519 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
520 | /// | |
7453a54e | 521 | /// let sparkle_heart = String::from_utf8_lossy(&sparkle_heart); |
b039eaaf SL |
522 | /// |
523 | /// assert_eq!("💖", sparkle_heart); | |
524 | /// ``` | |
525 | /// | |
526 | /// Incorrect bytes: | |
527 | /// | |
528 | /// ``` | |
529 | /// // some invalid bytes | |
1a4d82fc JJ |
530 | /// let input = b"Hello \xF0\x90\x80World"; |
531 | /// let output = String::from_utf8_lossy(input); | |
b039eaaf SL |
532 | /// |
533 | /// assert_eq!("Hello �World", output); | |
1a4d82fc | 534 | /// ``` |
85aaf69f | 535 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 536 | pub fn from_utf8_lossy(v: &[u8]) -> Cow<'_, str> { |
041b39d2 | 537 | let mut iter = lossy::Utf8Lossy::from_bytes(v).chunks(); |
1a4d82fc | 538 | |
041b39d2 XL |
539 | let (first_valid, first_broken) = if let Some(chunk) = iter.next() { |
540 | let lossy::Utf8LossyChunk { valid, broken } = chunk; | |
541 | if valid.len() == v.len() { | |
542 | debug_assert!(broken.is_empty()); | |
543 | return Cow::Borrowed(valid); | |
544 | } | |
545 | (valid, broken) | |
546 | } else { | |
547 | return Cow::Borrowed(""); | |
548 | }; | |
1a4d82fc | 549 | |
0731742a | 550 | const REPLACEMENT: &str = "\u{FFFD}"; |
1a4d82fc | 551 | |
041b39d2 XL |
552 | let mut res = String::with_capacity(v.len()); |
553 | res.push_str(first_valid); | |
554 | if !first_broken.is_empty() { | |
555 | res.push_str(REPLACEMENT); | |
1a4d82fc JJ |
556 | } |
557 | ||
041b39d2 XL |
558 | for lossy::Utf8LossyChunk { valid, broken } in iter { |
559 | res.push_str(valid); | |
560 | if !broken.is_empty() { | |
561 | res.push_str(REPLACEMENT); | |
1a4d82fc JJ |
562 | } |
563 | } | |
041b39d2 | 564 | |
1a4d82fc JJ |
565 | Cow::Owned(res) |
566 | } | |
567 | ||
29967ef6 | 568 | /// Decode a UTF-16–encoded vector `v` into a `String`, returning [`Err`] |
1a4d82fc JJ |
569 | /// if `v` contains any invalid data. |
570 | /// | |
571 | /// # Examples | |
572 | /// | |
9cc50fc6 SL |
573 | /// Basic usage: |
574 | /// | |
c34b1796 | 575 | /// ``` |
1a4d82fc | 576 | /// // 𝄞music |
92a42be0 SL |
577 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, |
578 | /// 0x0073, 0x0069, 0x0063]; | |
9cc50fc6 SL |
579 | /// assert_eq!(String::from("𝄞music"), |
580 | /// String::from_utf16(v).unwrap()); | |
1a4d82fc JJ |
581 | /// |
582 | /// // 𝄞mu<invalid>ic | |
92a42be0 SL |
583 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, |
584 | /// 0xD800, 0x0069, 0x0063]; | |
1a4d82fc JJ |
585 | /// assert!(String::from_utf16(v).is_err()); |
586 | /// ``` | |
85aaf69f | 587 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 588 | pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error> { |
a1dfa0c6 XL |
589 | // This isn't done via collect::<Result<_, _>>() for performance reasons. |
590 | // FIXME: the function can be simplified again when #48994 is closed. | |
591 | let mut ret = String::with_capacity(v.len()); | |
592 | for c in decode_utf16(v.iter().cloned()) { | |
593 | if let Ok(c) = c { | |
594 | ret.push(c); | |
595 | } else { | |
596 | return Err(FromUtf16Error(())); | |
597 | } | |
598 | } | |
599 | Ok(ret) | |
1a4d82fc JJ |
600 | } |
601 | ||
29967ef6 | 602 | /// Decode a UTF-16–encoded slice `v` into a `String`, replacing |
b7449926 | 603 | /// invalid data with [the replacement character (`U+FFFD`)][U+FFFD]. |
1a4d82fc | 604 | /// |
ea8adc8c XL |
605 | /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`], |
606 | /// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8 | |
607 | /// conversion requires a memory allocation. | |
608 | /// | |
3dfed10e XL |
609 | /// [`from_utf8_lossy`]: String::from_utf8_lossy |
610 | /// [`Cow<'a, str>`]: crate::borrow::Cow | |
611 | /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER | |
ea8adc8c | 612 | /// |
1a4d82fc JJ |
613 | /// # Examples |
614 | /// | |
9cc50fc6 SL |
615 | /// Basic usage: |
616 | /// | |
c34b1796 | 617 | /// ``` |
1a4d82fc JJ |
618 | /// // 𝄞mus<invalid>ic<invalid> |
619 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, | |
620 | /// 0x0073, 0xDD1E, 0x0069, 0x0063, | |
621 | /// 0xD834]; | |
622 | /// | |
9cc50fc6 SL |
623 | /// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"), |
624 | /// String::from_utf16_lossy(v)); | |
1a4d82fc | 625 | /// ``` |
85aaf69f SL |
626 | #[inline] |
627 | #[stable(feature = "rust1", since = "1.0.0")] | |
1a4d82fc | 628 | pub fn from_utf16_lossy(v: &[u16]) -> String { |
e9174d1e | 629 | decode_utf16(v.iter().cloned()).map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)).collect() |
1a4d82fc JJ |
630 | } |
631 | ||
e74abb32 XL |
632 | /// Decomposes a `String` into its raw components. |
633 | /// | |
634 | /// Returns the raw pointer to the underlying data, the length of | |
635 | /// the string (in bytes), and the allocated capacity of the data | |
636 | /// (in bytes). These are the same arguments in the same order as | |
637 | /// the arguments to [`from_raw_parts`]. | |
638 | /// | |
639 | /// After calling this function, the caller is responsible for the | |
640 | /// memory previously managed by the `String`. The only way to do | |
641 | /// this is to convert the raw pointer, length, and capacity back | |
642 | /// into a `String` with the [`from_raw_parts`] function, allowing | |
643 | /// the destructor to perform the cleanup. | |
644 | /// | |
3dfed10e | 645 | /// [`from_raw_parts`]: String::from_raw_parts |
e74abb32 XL |
646 | /// |
647 | /// # Examples | |
648 | /// | |
649 | /// ``` | |
650 | /// #![feature(vec_into_raw_parts)] | |
651 | /// let s = String::from("hello"); | |
652 | /// | |
653 | /// let (ptr, len, cap) = s.into_raw_parts(); | |
654 | /// | |
655 | /// let rebuilt = unsafe { String::from_raw_parts(ptr, len, cap) }; | |
656 | /// assert_eq!(rebuilt, "hello"); | |
657 | /// ``` | |
658 | #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] | |
659 | pub fn into_raw_parts(self) -> (*mut u8, usize, usize) { | |
660 | self.vec.into_raw_parts() | |
661 | } | |
662 | ||
1a4d82fc JJ |
663 | /// Creates a new `String` from a length, capacity, and pointer. |
664 | /// | |
b039eaaf | 665 | /// # Safety |
c1a9b12d | 666 | /// |
9cc50fc6 SL |
667 | /// This is highly unsafe, due to the number of invariants that aren't |
668 | /// checked: | |
669 | /// | |
3dfed10e | 670 | /// * The memory at `buf` needs to have been previously allocated by the |
60c5eb7d | 671 | /// same allocator the standard library uses, with a required alignment of exactly 1. |
9cc50fc6 SL |
672 | /// * `length` needs to be less than or equal to `capacity`. |
673 | /// * `capacity` needs to be the correct value. | |
3dfed10e | 674 | /// * The first `length` bytes at `buf` need to be valid UTF-8. |
9cc50fc6 SL |
675 | /// |
676 | /// Violating these may cause problems like corrupting the allocator's | |
3b2f2976 | 677 | /// internal data structures. |
9cc50fc6 | 678 | /// |
3dfed10e | 679 | /// The ownership of `buf` is effectively transferred to the |
5bcae85e SL |
680 | /// `String` which may then deallocate, reallocate or change the |
681 | /// contents of memory pointed to by the pointer at will. Ensure | |
682 | /// that nothing else uses the pointer after calling this | |
683 | /// function. | |
684 | /// | |
9cc50fc6 SL |
685 | /// # Examples |
686 | /// | |
687 | /// Basic usage: | |
688 | /// | |
689 | /// ``` | |
690 | /// use std::mem; | |
691 | /// | |
692 | /// unsafe { | |
693 | /// let s = String::from("hello"); | |
e74abb32 XL |
694 | /// |
695 | // FIXME Update this when vec_into_raw_parts is stabilized | |
696 | /// // Prevent automatically dropping the String's data | |
697 | /// let mut s = mem::ManuallyDrop::new(s); | |
698 | /// | |
699 | /// let ptr = s.as_mut_ptr(); | |
9cc50fc6 SL |
700 | /// let len = s.len(); |
701 | /// let capacity = s.capacity(); | |
702 | /// | |
e74abb32 | 703 | /// let s = String::from_raw_parts(ptr, len, capacity); |
c34b1796 | 704 | /// |
9cc50fc6 SL |
705 | /// assert_eq!(String::from("hello"), s); |
706 | /// } | |
707 | /// ``` | |
1a4d82fc | 708 | #[inline] |
85aaf69f SL |
709 | #[stable(feature = "rust1", since = "1.0.0")] |
710 | pub unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String { | |
f035d41b | 711 | unsafe { String { vec: Vec::from_raw_parts(buf, length, capacity) } } |
1a4d82fc JJ |
712 | } |
713 | ||
b039eaaf SL |
714 | /// Converts a vector of bytes to a `String` without checking that the |
715 | /// string contains valid UTF-8. | |
716 | /// | |
cc61c64b | 717 | /// See the safe version, [`from_utf8`], for more details. |
b039eaaf | 718 | /// |
3dfed10e | 719 | /// [`from_utf8`]: String::from_utf8 |
b039eaaf SL |
720 | /// |
721 | /// # Safety | |
722 | /// | |
9cc50fc6 SL |
723 | /// This function is unsafe because it does not check that the bytes passed |
724 | /// to it are valid UTF-8. If this constraint is violated, it may cause | |
725 | /// memory unsafety issues with future users of the `String`, as the rest of | |
726 | /// the standard library assumes that `String`s are valid UTF-8. | |
b039eaaf SL |
727 | /// |
728 | /// # Examples | |
729 | /// | |
730 | /// Basic usage: | |
731 | /// | |
732 | /// ``` | |
733 | /// // some bytes, in a vector | |
734 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
735 | /// | |
736 | /// let sparkle_heart = unsafe { | |
737 | /// String::from_utf8_unchecked(sparkle_heart) | |
738 | /// }; | |
739 | /// | |
740 | /// assert_eq!("💖", sparkle_heart); | |
741 | /// ``` | |
1a4d82fc | 742 | #[inline] |
85aaf69f | 743 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
744 | pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String { |
745 | String { vec: bytes } | |
746 | } | |
747 | ||
9cc50fc6 SL |
748 | /// Converts a `String` into a byte vector. |
749 | /// | |
750 | /// This consumes the `String`, so we do not need to copy its contents. | |
1a4d82fc JJ |
751 | /// |
752 | /// # Examples | |
753 | /// | |
9cc50fc6 SL |
754 | /// Basic usage: |
755 | /// | |
1a4d82fc | 756 | /// ``` |
62682a34 | 757 | /// let s = String::from("hello"); |
1a4d82fc | 758 | /// let bytes = s.into_bytes(); |
9cc50fc6 SL |
759 | /// |
760 | /// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]); | |
1a4d82fc JJ |
761 | /// ``` |
762 | #[inline] | |
85aaf69f | 763 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
764 | pub fn into_bytes(self) -> Vec<u8> { |
765 | self.vec | |
766 | } | |
767 | ||
b7449926 | 768 | /// Extracts a string slice containing the entire `String`. |
ea8adc8c XL |
769 | /// |
770 | /// # Examples | |
771 | /// | |
772 | /// Basic usage: | |
773 | /// | |
774 | /// ``` | |
775 | /// let s = String::from("foo"); | |
776 | /// | |
777 | /// assert_eq!("foo", s.as_str()); | |
778 | /// ``` | |
c34b1796 | 779 | #[inline] |
9cc50fc6 | 780 | #[stable(feature = "string_as_str", since = "1.7.0")] |
c34b1796 AL |
781 | pub fn as_str(&self) -> &str { |
782 | self | |
783 | } | |
784 | ||
ea8adc8c XL |
785 | /// Converts a `String` into a mutable string slice. |
786 | /// | |
787 | /// # Examples | |
788 | /// | |
789 | /// Basic usage: | |
790 | /// | |
791 | /// ``` | |
ea8adc8c XL |
792 | /// let mut s = String::from("foobar"); |
793 | /// let s_mut_str = s.as_mut_str(); | |
794 | /// | |
795 | /// s_mut_str.make_ascii_uppercase(); | |
796 | /// | |
797 | /// assert_eq!("FOOBAR", s_mut_str); | |
798 | /// ``` | |
9cc50fc6 SL |
799 | #[inline] |
800 | #[stable(feature = "string_as_str", since = "1.7.0")] | |
801 | pub fn as_mut_str(&mut self) -> &mut str { | |
802 | self | |
803 | } | |
804 | ||
805 | /// Appends a given string slice onto the end of this `String`. | |
1a4d82fc JJ |
806 | /// |
807 | /// # Examples | |
808 | /// | |
9cc50fc6 SL |
809 | /// Basic usage: |
810 | /// | |
1a4d82fc | 811 | /// ``` |
62682a34 | 812 | /// let mut s = String::from("foo"); |
9cc50fc6 | 813 | /// |
1a4d82fc | 814 | /// s.push_str("bar"); |
9cc50fc6 SL |
815 | /// |
816 | /// assert_eq!("foobar", s); | |
1a4d82fc JJ |
817 | /// ``` |
818 | #[inline] | |
85aaf69f | 819 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 820 | pub fn push_str(&mut self, string: &str) { |
92a42be0 | 821 | self.vec.extend_from_slice(string.as_bytes()) |
1a4d82fc JJ |
822 | } |
823 | ||
9cc50fc6 | 824 | /// Returns this `String`'s capacity, in bytes. |
1a4d82fc JJ |
825 | /// |
826 | /// # Examples | |
827 | /// | |
9cc50fc6 SL |
828 | /// Basic usage: |
829 | /// | |
1a4d82fc JJ |
830 | /// ``` |
831 | /// let s = String::with_capacity(10); | |
9cc50fc6 | 832 | /// |
1a4d82fc JJ |
833 | /// assert!(s.capacity() >= 10); |
834 | /// ``` | |
835 | #[inline] | |
85aaf69f SL |
836 | #[stable(feature = "rust1", since = "1.0.0")] |
837 | pub fn capacity(&self) -> usize { | |
1a4d82fc JJ |
838 | self.vec.capacity() |
839 | } | |
840 | ||
9cc50fc6 SL |
841 | /// Ensures that this `String`'s capacity is at least `additional` bytes |
842 | /// larger than its length. | |
843 | /// | |
844 | /// The capacity may be increased by more than `additional` bytes if it | |
845 | /// chooses, to prevent frequent reallocations. | |
846 | /// | |
cc61c64b | 847 | /// If you do not want this "at least" behavior, see the [`reserve_exact`] |
9cc50fc6 SL |
848 | /// method. |
849 | /// | |
1a4d82fc JJ |
850 | /// # Panics |
851 | /// | |
3b2f2976 XL |
852 | /// Panics if the new capacity overflows [`usize`]. |
853 | /// | |
3dfed10e | 854 | /// [`reserve_exact`]: String::reserve_exact |
1a4d82fc JJ |
855 | /// |
856 | /// # Examples | |
857 | /// | |
9cc50fc6 SL |
858 | /// Basic usage: |
859 | /// | |
1a4d82fc JJ |
860 | /// ``` |
861 | /// let mut s = String::new(); | |
9cc50fc6 | 862 | /// |
1a4d82fc | 863 | /// s.reserve(10); |
9cc50fc6 | 864 | /// |
1a4d82fc JJ |
865 | /// assert!(s.capacity() >= 10); |
866 | /// ``` | |
9cc50fc6 SL |
867 | /// |
868 | /// This may not actually increase the capacity: | |
869 | /// | |
870 | /// ``` | |
871 | /// let mut s = String::with_capacity(10); | |
872 | /// s.push('a'); | |
873 | /// s.push('b'); | |
874 | /// | |
875 | /// // s now has a length of 2 and a capacity of 10 | |
876 | /// assert_eq!(2, s.len()); | |
877 | /// assert_eq!(10, s.capacity()); | |
878 | /// | |
879 | /// // Since we already have an extra 8 capacity, calling this... | |
880 | /// s.reserve(8); | |
881 | /// | |
882 | /// // ... doesn't actually increase. | |
883 | /// assert_eq!(10, s.capacity()); | |
884 | /// ``` | |
1a4d82fc | 885 | #[inline] |
85aaf69f SL |
886 | #[stable(feature = "rust1", since = "1.0.0")] |
887 | pub fn reserve(&mut self, additional: usize) { | |
1a4d82fc JJ |
888 | self.vec.reserve(additional) |
889 | } | |
890 | ||
9cc50fc6 SL |
891 | /// Ensures that this `String`'s capacity is `additional` bytes |
892 | /// larger than its length. | |
1a4d82fc | 893 | /// |
cc61c64b | 894 | /// Consider using the [`reserve`] method unless you absolutely know |
9cc50fc6 SL |
895 | /// better than the allocator. |
896 | /// | |
3dfed10e | 897 | /// [`reserve`]: String::reserve |
1a4d82fc JJ |
898 | /// |
899 | /// # Panics | |
900 | /// | |
85aaf69f | 901 | /// Panics if the new capacity overflows `usize`. |
1a4d82fc JJ |
902 | /// |
903 | /// # Examples | |
904 | /// | |
9cc50fc6 SL |
905 | /// Basic usage: |
906 | /// | |
1a4d82fc JJ |
907 | /// ``` |
908 | /// let mut s = String::new(); | |
9cc50fc6 | 909 | /// |
62682a34 | 910 | /// s.reserve_exact(10); |
9cc50fc6 | 911 | /// |
1a4d82fc JJ |
912 | /// assert!(s.capacity() >= 10); |
913 | /// ``` | |
9cc50fc6 SL |
914 | /// |
915 | /// This may not actually increase the capacity: | |
916 | /// | |
917 | /// ``` | |
918 | /// let mut s = String::with_capacity(10); | |
919 | /// s.push('a'); | |
920 | /// s.push('b'); | |
921 | /// | |
922 | /// // s now has a length of 2 and a capacity of 10 | |
923 | /// assert_eq!(2, s.len()); | |
924 | /// assert_eq!(10, s.capacity()); | |
925 | /// | |
926 | /// // Since we already have an extra 8 capacity, calling this... | |
927 | /// s.reserve_exact(8); | |
928 | /// | |
929 | /// // ... doesn't actually increase. | |
930 | /// assert_eq!(10, s.capacity()); | |
931 | /// ``` | |
1a4d82fc | 932 | #[inline] |
85aaf69f SL |
933 | #[stable(feature = "rust1", since = "1.0.0")] |
934 | pub fn reserve_exact(&mut self, additional: usize) { | |
1a4d82fc JJ |
935 | self.vec.reserve_exact(additional) |
936 | } | |
937 | ||
0531ce1d XL |
938 | /// Tries to reserve capacity for at least `additional` more elements to be inserted |
939 | /// in the given `String`. The collection may reserve more space to avoid | |
940 | /// frequent reallocations. After calling `reserve`, capacity will be | |
941 | /// greater than or equal to `self.len() + additional`. Does nothing if | |
942 | /// capacity is already sufficient. | |
943 | /// | |
944 | /// # Errors | |
945 | /// | |
946 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
947 | /// is returned. | |
948 | /// | |
949 | /// # Examples | |
950 | /// | |
951 | /// ``` | |
952 | /// #![feature(try_reserve)] | |
e1599b0c | 953 | /// use std::collections::TryReserveError; |
0531ce1d | 954 | /// |
e1599b0c | 955 | /// fn process_data(data: &str) -> Result<String, TryReserveError> { |
0531ce1d XL |
956 | /// let mut output = String::new(); |
957 | /// | |
958 | /// // Pre-reserve the memory, exiting if we can't | |
959 | /// output.try_reserve(data.len())?; | |
960 | /// | |
961 | /// // Now we know this can't OOM in the middle of our complex work | |
962 | /// output.push_str(data); | |
963 | /// | |
964 | /// Ok(output) | |
965 | /// } | |
966 | /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?"); | |
967 | /// ``` | |
dfeec247 | 968 | #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] |
e1599b0c | 969 | pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { |
0531ce1d XL |
970 | self.vec.try_reserve(additional) |
971 | } | |
972 | ||
973 | /// Tries to reserves the minimum capacity for exactly `additional` more elements to | |
974 | /// be inserted in the given `String`. After calling `reserve_exact`, | |
975 | /// capacity will be greater than or equal to `self.len() + additional`. | |
976 | /// Does nothing if the capacity is already sufficient. | |
977 | /// | |
978 | /// Note that the allocator may give the collection more space than it | |
9fa01778 | 979 | /// requests. Therefore, capacity can not be relied upon to be precisely |
0531ce1d XL |
980 | /// minimal. Prefer `reserve` if future insertions are expected. |
981 | /// | |
982 | /// # Errors | |
983 | /// | |
984 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
985 | /// is returned. | |
986 | /// | |
987 | /// # Examples | |
988 | /// | |
989 | /// ``` | |
990 | /// #![feature(try_reserve)] | |
e1599b0c | 991 | /// use std::collections::TryReserveError; |
0531ce1d | 992 | /// |
e1599b0c | 993 | /// fn process_data(data: &str) -> Result<String, TryReserveError> { |
0531ce1d XL |
994 | /// let mut output = String::new(); |
995 | /// | |
996 | /// // Pre-reserve the memory, exiting if we can't | |
997 | /// output.try_reserve(data.len())?; | |
998 | /// | |
999 | /// // Now we know this can't OOM in the middle of our complex work | |
1000 | /// output.push_str(data); | |
1001 | /// | |
1002 | /// Ok(output) | |
1003 | /// } | |
1004 | /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?"); | |
1005 | /// ``` | |
dfeec247 XL |
1006 | #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] |
1007 | pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { | |
0531ce1d XL |
1008 | self.vec.try_reserve_exact(additional) |
1009 | } | |
1010 | ||
9cc50fc6 | 1011 | /// Shrinks the capacity of this `String` to match its length. |
1a4d82fc JJ |
1012 | /// |
1013 | /// # Examples | |
1014 | /// | |
9cc50fc6 SL |
1015 | /// Basic usage: |
1016 | /// | |
1a4d82fc | 1017 | /// ``` |
62682a34 | 1018 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1019 | /// |
1a4d82fc JJ |
1020 | /// s.reserve(100); |
1021 | /// assert!(s.capacity() >= 100); | |
9cc50fc6 | 1022 | /// |
1a4d82fc | 1023 | /// s.shrink_to_fit(); |
9cc50fc6 | 1024 | /// assert_eq!(3, s.capacity()); |
1a4d82fc JJ |
1025 | /// ``` |
1026 | #[inline] | |
85aaf69f | 1027 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1028 | pub fn shrink_to_fit(&mut self) { |
1029 | self.vec.shrink_to_fit() | |
1030 | } | |
1031 | ||
0531ce1d XL |
1032 | /// Shrinks the capacity of this `String` with a lower bound. |
1033 | /// | |
1034 | /// The capacity will remain at least as large as both the length | |
1035 | /// and the supplied value. | |
1036 | /// | |
1037 | /// Panics if the current capacity is smaller than the supplied | |
1038 | /// minimum capacity. | |
1039 | /// | |
1040 | /// # Examples | |
1041 | /// | |
1042 | /// ``` | |
1043 | /// #![feature(shrink_to)] | |
1044 | /// let mut s = String::from("foo"); | |
1045 | /// | |
1046 | /// s.reserve(100); | |
1047 | /// assert!(s.capacity() >= 100); | |
1048 | /// | |
1049 | /// s.shrink_to(10); | |
1050 | /// assert!(s.capacity() >= 10); | |
1051 | /// s.shrink_to(0); | |
1052 | /// assert!(s.capacity() >= 3); | |
1053 | /// ``` | |
1054 | #[inline] | |
dfeec247 | 1055 | #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")] |
0531ce1d XL |
1056 | pub fn shrink_to(&mut self, min_capacity: usize) { |
1057 | self.vec.shrink_to(min_capacity) | |
1058 | } | |
1059 | ||
3b2f2976 XL |
1060 | /// Appends the given [`char`] to the end of this `String`. |
1061 | /// | |
1a4d82fc JJ |
1062 | /// # Examples |
1063 | /// | |
9cc50fc6 SL |
1064 | /// Basic usage: |
1065 | /// | |
1a4d82fc | 1066 | /// ``` |
62682a34 | 1067 | /// let mut s = String::from("abc"); |
9cc50fc6 | 1068 | /// |
1a4d82fc JJ |
1069 | /// s.push('1'); |
1070 | /// s.push('2'); | |
1071 | /// s.push('3'); | |
9cc50fc6 SL |
1072 | /// |
1073 | /// assert_eq!("abc123", s); | |
1a4d82fc JJ |
1074 | /// ``` |
1075 | #[inline] | |
85aaf69f | 1076 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1077 | pub fn push(&mut self, ch: char) { |
62682a34 SL |
1078 | match ch.len_utf8() { |
1079 | 1 => self.vec.push(ch as u8), | |
32a655c1 | 1080 | _ => self.vec.extend_from_slice(ch.encode_utf8(&mut [0; 4]).as_bytes()), |
1a4d82fc JJ |
1081 | } |
1082 | } | |
1083 | ||
9cc50fc6 | 1084 | /// Returns a byte slice of this `String`'s contents. |
1a4d82fc | 1085 | /// |
8bb4bdeb XL |
1086 | /// The inverse of this method is [`from_utf8`]. |
1087 | /// | |
3dfed10e | 1088 | /// [`from_utf8`]: String::from_utf8 |
8bb4bdeb | 1089 | /// |
1a4d82fc JJ |
1090 | /// # Examples |
1091 | /// | |
9cc50fc6 SL |
1092 | /// Basic usage: |
1093 | /// | |
1a4d82fc | 1094 | /// ``` |
62682a34 | 1095 | /// let s = String::from("hello"); |
9cc50fc6 SL |
1096 | /// |
1097 | /// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes()); | |
1a4d82fc JJ |
1098 | /// ``` |
1099 | #[inline] | |
85aaf69f SL |
1100 | #[stable(feature = "rust1", since = "1.0.0")] |
1101 | pub fn as_bytes(&self) -> &[u8] { | |
1102 | &self.vec | |
1a4d82fc JJ |
1103 | } |
1104 | ||
9cc50fc6 | 1105 | /// Shortens this `String` to the specified length. |
1a4d82fc | 1106 | /// |
a7813a04 XL |
1107 | /// If `new_len` is greater than the string's current length, this has no |
1108 | /// effect. | |
1109 | /// | |
8bb4bdeb XL |
1110 | /// Note that this method has no effect on the allocated capacity |
1111 | /// of the string | |
1112 | /// | |
1a4d82fc JJ |
1113 | /// # Panics |
1114 | /// | |
a7813a04 | 1115 | /// Panics if `new_len` does not lie on a [`char`] boundary. |
9cc50fc6 | 1116 | /// |
1a4d82fc JJ |
1117 | /// # Examples |
1118 | /// | |
9cc50fc6 SL |
1119 | /// Basic usage: |
1120 | /// | |
1a4d82fc | 1121 | /// ``` |
62682a34 | 1122 | /// let mut s = String::from("hello"); |
9cc50fc6 | 1123 | /// |
1a4d82fc | 1124 | /// s.truncate(2); |
9cc50fc6 SL |
1125 | /// |
1126 | /// assert_eq!("he", s); | |
1a4d82fc JJ |
1127 | /// ``` |
1128 | #[inline] | |
85aaf69f SL |
1129 | #[stable(feature = "rust1", since = "1.0.0")] |
1130 | pub fn truncate(&mut self, new_len: usize) { | |
a7813a04 XL |
1131 | if new_len <= self.len() { |
1132 | assert!(self.is_char_boundary(new_len)); | |
1133 | self.vec.truncate(new_len) | |
1134 | } | |
1a4d82fc JJ |
1135 | } |
1136 | ||
1137 | /// Removes the last character from the string buffer and returns it. | |
9cc50fc6 | 1138 | /// |
3b2f2976 XL |
1139 | /// Returns [`None`] if this `String` is empty. |
1140 | /// | |
1a4d82fc JJ |
1141 | /// # Examples |
1142 | /// | |
9cc50fc6 SL |
1143 | /// Basic usage: |
1144 | /// | |
1a4d82fc | 1145 | /// ``` |
62682a34 | 1146 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1147 | /// |
1a4d82fc JJ |
1148 | /// assert_eq!(s.pop(), Some('o')); |
1149 | /// assert_eq!(s.pop(), Some('o')); | |
1150 | /// assert_eq!(s.pop(), Some('f')); | |
9cc50fc6 | 1151 | /// |
1a4d82fc JJ |
1152 | /// assert_eq!(s.pop(), None); |
1153 | /// ``` | |
1154 | #[inline] | |
85aaf69f | 1155 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1156 | pub fn pop(&mut self) -> Option<char> { |
ff7c6d11 | 1157 | let ch = self.chars().rev().next()?; |
54a0048b | 1158 | let newlen = self.len() - ch.len_utf8(); |
1a4d82fc | 1159 | unsafe { |
54a0048b | 1160 | self.vec.set_len(newlen); |
1a4d82fc JJ |
1161 | } |
1162 | Some(ch) | |
1163 | } | |
1164 | ||
3b2f2976 | 1165 | /// Removes a [`char`] from this `String` at a byte position and returns it. |
1a4d82fc | 1166 | /// |
3dfed10e | 1167 | /// This is an *O*(*n*) operation, as it requires copying every element in the |
1a4d82fc JJ |
1168 | /// buffer. |
1169 | /// | |
1170 | /// # Panics | |
1171 | /// | |
9cc50fc6 SL |
1172 | /// Panics if `idx` is larger than or equal to the `String`'s length, |
1173 | /// or if it does not lie on a [`char`] boundary. | |
1174 | /// | |
1a4d82fc JJ |
1175 | /// # Examples |
1176 | /// | |
9cc50fc6 SL |
1177 | /// Basic usage: |
1178 | /// | |
1a4d82fc | 1179 | /// ``` |
62682a34 | 1180 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1181 | /// |
1a4d82fc JJ |
1182 | /// assert_eq!(s.remove(0), 'f'); |
1183 | /// assert_eq!(s.remove(1), 'o'); | |
1184 | /// assert_eq!(s.remove(0), 'o'); | |
1185 | /// ``` | |
85aaf69f SL |
1186 | #[inline] |
1187 | #[stable(feature = "rust1", since = "1.0.0")] | |
1188 | pub fn remove(&mut self, idx: usize) -> char { | |
54a0048b SL |
1189 | let ch = match self[idx..].chars().next() { |
1190 | Some(ch) => ch, | |
1191 | None => panic!("cannot remove a char from the end of a string"), | |
1192 | }; | |
1a4d82fc | 1193 | |
c34b1796 | 1194 | let next = idx + ch.len_utf8(); |
54a0048b | 1195 | let len = self.len(); |
1a4d82fc | 1196 | unsafe { |
dfeec247 | 1197 | ptr::copy(self.vec.as_ptr().add(next), self.vec.as_mut_ptr().add(idx), len - next); |
1a4d82fc JJ |
1198 | self.vec.set_len(len - (next - idx)); |
1199 | } | |
1200 | ch | |
1201 | } | |
1202 | ||
3b2f2976 XL |
1203 | /// Retains only the characters specified by the predicate. |
1204 | /// | |
1205 | /// In other words, remove all characters `c` such that `f(c)` returns `false`. | |
48663c56 XL |
1206 | /// This method operates in place, visiting each character exactly once in the |
1207 | /// original order, and preserves the order of the retained characters. | |
3b2f2976 XL |
1208 | /// |
1209 | /// # Examples | |
1210 | /// | |
1211 | /// ``` | |
3b2f2976 XL |
1212 | /// let mut s = String::from("f_o_ob_ar"); |
1213 | /// | |
1214 | /// s.retain(|c| c != '_'); | |
1215 | /// | |
1216 | /// assert_eq!(s, "foobar"); | |
1217 | /// ``` | |
48663c56 XL |
1218 | /// |
1219 | /// The exact order may be useful for tracking external state, like an index. | |
1220 | /// | |
1221 | /// ``` | |
1222 | /// let mut s = String::from("abcde"); | |
1223 | /// let keep = [false, true, true, false, true]; | |
1224 | /// let mut i = 0; | |
1225 | /// s.retain(|_| (keep[i], i += 1).0); | |
1226 | /// assert_eq!(s, "bce"); | |
1227 | /// ``` | |
3b2f2976 | 1228 | #[inline] |
0531ce1d | 1229 | #[stable(feature = "string_retain", since = "1.26.0")] |
3b2f2976 | 1230 | pub fn retain<F>(&mut self, mut f: F) |
dfeec247 XL |
1231 | where |
1232 | F: FnMut(char) -> bool, | |
3b2f2976 XL |
1233 | { |
1234 | let len = self.len(); | |
1235 | let mut del_bytes = 0; | |
1236 | let mut idx = 0; | |
1237 | ||
29967ef6 XL |
1238 | unsafe { |
1239 | self.vec.set_len(0); | |
1240 | } | |
1241 | ||
3b2f2976 | 1242 | while idx < len { |
dfeec247 | 1243 | let ch = unsafe { self.get_unchecked(idx..len).chars().next().unwrap() }; |
3b2f2976 XL |
1244 | let ch_len = ch.len_utf8(); |
1245 | ||
1246 | if !f(ch) { | |
1247 | del_bytes += ch_len; | |
1248 | } else if del_bytes > 0 { | |
1249 | unsafe { | |
dfeec247 XL |
1250 | ptr::copy( |
1251 | self.vec.as_ptr().add(idx), | |
1252 | self.vec.as_mut_ptr().add(idx - del_bytes), | |
1253 | ch_len, | |
1254 | ); | |
3b2f2976 XL |
1255 | } |
1256 | } | |
1257 | ||
1258 | // Point idx to the next char | |
1259 | idx += ch_len; | |
1260 | } | |
1261 | ||
29967ef6 XL |
1262 | unsafe { |
1263 | self.vec.set_len(len - del_bytes); | |
3b2f2976 XL |
1264 | } |
1265 | } | |
1266 | ||
9cc50fc6 | 1267 | /// Inserts a character into this `String` at a byte position. |
1a4d82fc | 1268 | /// |
3dfed10e | 1269 | /// This is an *O*(*n*) operation as it requires copying every element in the |
1a4d82fc JJ |
1270 | /// buffer. |
1271 | /// | |
1272 | /// # Panics | |
1273 | /// | |
9cc50fc6 SL |
1274 | /// Panics if `idx` is larger than the `String`'s length, or if it does not |
1275 | /// lie on a [`char`] boundary. | |
1276 | /// | |
9cc50fc6 SL |
1277 | /// # Examples |
1278 | /// | |
1279 | /// Basic usage: | |
1280 | /// | |
1281 | /// ``` | |
1282 | /// let mut s = String::with_capacity(3); | |
1283 | /// | |
1284 | /// s.insert(0, 'f'); | |
1285 | /// s.insert(1, 'o'); | |
1286 | /// s.insert(2, 'o'); | |
1287 | /// | |
1288 | /// assert_eq!("foo", s); | |
1289 | /// ``` | |
85aaf69f SL |
1290 | #[inline] |
1291 | #[stable(feature = "rust1", since = "1.0.0")] | |
1292 | pub fn insert(&mut self, idx: usize, ch: char) { | |
1a4d82fc | 1293 | assert!(self.is_char_boundary(idx)); |
c30ab7b3 SL |
1294 | let mut bits = [0; 4]; |
1295 | let bits = ch.encode_utf8(&mut bits).as_bytes(); | |
5bcae85e SL |
1296 | |
1297 | unsafe { | |
c30ab7b3 | 1298 | self.insert_bytes(idx, bits); |
5bcae85e SL |
1299 | } |
1300 | } | |
1301 | ||
1302 | unsafe fn insert_bytes(&mut self, idx: usize, bytes: &[u8]) { | |
1303 | let len = self.len(); | |
1304 | let amt = bytes.len(); | |
54a0048b | 1305 | self.vec.reserve(amt); |
1a4d82fc | 1306 | |
f035d41b XL |
1307 | unsafe { |
1308 | ptr::copy(self.vec.as_ptr().add(idx), self.vec.as_mut_ptr().add(idx + amt), len - idx); | |
1309 | ptr::copy(bytes.as_ptr(), self.vec.as_mut_ptr().add(idx), amt); | |
1310 | self.vec.set_len(len + amt); | |
1311 | } | |
5bcae85e SL |
1312 | } |
1313 | ||
1314 | /// Inserts a string slice into this `String` at a byte position. | |
1315 | /// | |
3dfed10e | 1316 | /// This is an *O*(*n*) operation as it requires copying every element in the |
5bcae85e SL |
1317 | /// buffer. |
1318 | /// | |
1319 | /// # Panics | |
1320 | /// | |
1321 | /// Panics if `idx` is larger than the `String`'s length, or if it does not | |
1322 | /// lie on a [`char`] boundary. | |
1323 | /// | |
5bcae85e SL |
1324 | /// # Examples |
1325 | /// | |
1326 | /// Basic usage: | |
1327 | /// | |
1328 | /// ``` | |
5bcae85e SL |
1329 | /// let mut s = String::from("bar"); |
1330 | /// | |
1331 | /// s.insert_str(0, "foo"); | |
1332 | /// | |
1333 | /// assert_eq!("foobar", s); | |
1334 | /// ``` | |
1335 | #[inline] | |
32a655c1 | 1336 | #[stable(feature = "insert_str", since = "1.16.0")] |
5bcae85e | 1337 | pub fn insert_str(&mut self, idx: usize, string: &str) { |
5bcae85e SL |
1338 | assert!(self.is_char_boundary(idx)); |
1339 | ||
1a4d82fc | 1340 | unsafe { |
5bcae85e | 1341 | self.insert_bytes(idx, string.as_bytes()); |
1a4d82fc JJ |
1342 | } |
1343 | } | |
1344 | ||
9cc50fc6 | 1345 | /// Returns a mutable reference to the contents of this `String`. |
1a4d82fc | 1346 | /// |
9cc50fc6 SL |
1347 | /// # Safety |
1348 | /// | |
1349 | /// This function is unsafe because it does not check that the bytes passed | |
1350 | /// to it are valid UTF-8. If this constraint is violated, it may cause | |
1351 | /// memory unsafety issues with future users of the `String`, as the rest of | |
1352 | /// the standard library assumes that `String`s are valid UTF-8. | |
1a4d82fc JJ |
1353 | /// |
1354 | /// # Examples | |
1355 | /// | |
9cc50fc6 SL |
1356 | /// Basic usage: |
1357 | /// | |
1a4d82fc | 1358 | /// ``` |
62682a34 | 1359 | /// let mut s = String::from("hello"); |
9cc50fc6 | 1360 | /// |
1a4d82fc JJ |
1361 | /// unsafe { |
1362 | /// let vec = s.as_mut_vec(); | |
9cc50fc6 SL |
1363 | /// assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]); |
1364 | /// | |
1a4d82fc JJ |
1365 | /// vec.reverse(); |
1366 | /// } | |
c34b1796 | 1367 | /// assert_eq!(s, "olleh"); |
1a4d82fc | 1368 | /// ``` |
85aaf69f SL |
1369 | #[inline] |
1370 | #[stable(feature = "rust1", since = "1.0.0")] | |
1371 | pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8> { | |
1a4d82fc JJ |
1372 | &mut self.vec |
1373 | } | |
1374 | ||
60c5eb7d XL |
1375 | /// Returns the length of this `String`, in bytes, not [`char`]s or |
1376 | /// graphemes. In other words, it may not be what a human considers the | |
1377 | /// length of the string. | |
1a4d82fc JJ |
1378 | /// |
1379 | /// # Examples | |
1380 | /// | |
9cc50fc6 SL |
1381 | /// Basic usage: |
1382 | /// | |
1a4d82fc | 1383 | /// ``` |
9cc50fc6 | 1384 | /// let a = String::from("foo"); |
1a4d82fc | 1385 | /// assert_eq!(a.len(), 3); |
60c5eb7d XL |
1386 | /// |
1387 | /// let fancy_f = String::from("ƒoo"); | |
1388 | /// assert_eq!(fancy_f.len(), 4); | |
1389 | /// assert_eq!(fancy_f.chars().count(), 3); | |
1a4d82fc JJ |
1390 | /// ``` |
1391 | #[inline] | |
85aaf69f | 1392 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1393 | pub fn len(&self) -> usize { |
1394 | self.vec.len() | |
1395 | } | |
1a4d82fc | 1396 | |
9fa01778 | 1397 | /// Returns `true` if this `String` has a length of zero, and `false` otherwise. |
1a4d82fc JJ |
1398 | /// |
1399 | /// # Examples | |
1400 | /// | |
9cc50fc6 SL |
1401 | /// Basic usage: |
1402 | /// | |
1a4d82fc JJ |
1403 | /// ``` |
1404 | /// let mut v = String::new(); | |
1405 | /// assert!(v.is_empty()); | |
9cc50fc6 | 1406 | /// |
1a4d82fc JJ |
1407 | /// v.push('a'); |
1408 | /// assert!(!v.is_empty()); | |
1409 | /// ``` | |
85aaf69f SL |
1410 | #[inline] |
1411 | #[stable(feature = "rust1", since = "1.0.0")] | |
92a42be0 SL |
1412 | pub fn is_empty(&self) -> bool { |
1413 | self.len() == 0 | |
1414 | } | |
1a4d82fc | 1415 | |
fc512014 | 1416 | /// Splits the string into two at the given byte index. |
476ff2be | 1417 | /// |
8bb4bdeb XL |
1418 | /// Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and |
1419 | /// the returned `String` contains bytes `[at, len)`. `at` must be on the | |
1420 | /// boundary of a UTF-8 code point. | |
476ff2be | 1421 | /// |
8bb4bdeb | 1422 | /// Note that the capacity of `self` does not change. |
476ff2be SL |
1423 | /// |
1424 | /// # Panics | |
1425 | /// | |
8bb4bdeb | 1426 | /// Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last |
476ff2be SL |
1427 | /// code point of the string. |
1428 | /// | |
1429 | /// # Examples | |
1430 | /// | |
1431 | /// ``` | |
476ff2be SL |
1432 | /// # fn main() { |
1433 | /// let mut hello = String::from("Hello, World!"); | |
1434 | /// let world = hello.split_off(7); | |
1435 | /// assert_eq!(hello, "Hello, "); | |
1436 | /// assert_eq!(world, "World!"); | |
1437 | /// # } | |
1438 | /// ``` | |
1439 | #[inline] | |
32a655c1 | 1440 | #[stable(feature = "string_split_off", since = "1.16.0")] |
ba9703b0 | 1441 | #[must_use = "use `.truncate()` if you don't need the other half"] |
8bb4bdeb XL |
1442 | pub fn split_off(&mut self, at: usize) -> String { |
1443 | assert!(self.is_char_boundary(at)); | |
1444 | let other = self.vec.split_off(at); | |
476ff2be SL |
1445 | unsafe { String::from_utf8_unchecked(other) } |
1446 | } | |
1447 | ||
9cc50fc6 SL |
1448 | /// Truncates this `String`, removing all contents. |
1449 | /// | |
1450 | /// While this means the `String` will have a length of zero, it does not | |
1451 | /// touch its capacity. | |
1a4d82fc JJ |
1452 | /// |
1453 | /// # Examples | |
1454 | /// | |
9cc50fc6 SL |
1455 | /// Basic usage: |
1456 | /// | |
1a4d82fc | 1457 | /// ``` |
9cc50fc6 SL |
1458 | /// let mut s = String::from("foo"); |
1459 | /// | |
1a4d82fc | 1460 | /// s.clear(); |
9cc50fc6 | 1461 | /// |
1a4d82fc | 1462 | /// assert!(s.is_empty()); |
9cc50fc6 SL |
1463 | /// assert_eq!(0, s.len()); |
1464 | /// assert_eq!(3, s.capacity()); | |
1a4d82fc JJ |
1465 | /// ``` |
1466 | #[inline] | |
85aaf69f | 1467 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1468 | pub fn clear(&mut self) { |
1469 | self.vec.clear() | |
1470 | } | |
d9579d0f | 1471 | |
b7449926 XL |
1472 | /// Creates a draining iterator that removes the specified range in the `String` |
1473 | /// and yields the removed `chars`. | |
9cc50fc6 SL |
1474 | /// |
1475 | /// Note: The element range is removed even if the iterator is not | |
1476 | /// consumed until the end. | |
d9579d0f AL |
1477 | /// |
1478 | /// # Panics | |
1479 | /// | |
9cc50fc6 SL |
1480 | /// Panics if the starting point or end point do not lie on a [`char`] |
1481 | /// boundary, or if they're out of bounds. | |
1482 | /// | |
d9579d0f AL |
1483 | /// # Examples |
1484 | /// | |
9cc50fc6 SL |
1485 | /// Basic usage: |
1486 | /// | |
d9579d0f | 1487 | /// ``` |
d9579d0f AL |
1488 | /// let mut s = String::from("α is alpha, β is beta"); |
1489 | /// let beta_offset = s.find('β').unwrap_or(s.len()); | |
1490 | /// | |
1491 | /// // Remove the range up until the β from the string | |
1492 | /// let t: String = s.drain(..beta_offset).collect(); | |
1493 | /// assert_eq!(t, "α is alpha, "); | |
1494 | /// assert_eq!(s, "β is beta"); | |
1495 | /// | |
1496 | /// // A full range clears the string | |
1497 | /// s.drain(..); | |
1498 | /// assert_eq!(s, ""); | |
1499 | /// ``` | |
92a42be0 | 1500 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 1501 | pub fn drain<R>(&mut self, range: R) -> Drain<'_> |
dfeec247 XL |
1502 | where |
1503 | R: RangeBounds<usize>, | |
92a42be0 | 1504 | { |
d9579d0f AL |
1505 | // Memory safety |
1506 | // | |
1507 | // The String version of Drain does not have the memory safety issues | |
1508 | // of the vector version. The data is just plain bytes. | |
1509 | // Because the range removal happens in Drop, if the Drain iterator is leaked, | |
1510 | // the removal will not happen. | |
29967ef6 | 1511 | let Range { start, end } = range.assert_len(self.len()); |
1b1a35ee XL |
1512 | assert!(self.is_char_boundary(start)); |
1513 | assert!(self.is_char_boundary(end)); | |
d9579d0f AL |
1514 | |
1515 | // Take out two simultaneous borrows. The &mut String won't be accessed | |
1516 | // until iteration is over, in Drop. | |
1517 | let self_ptr = self as *mut _; | |
29967ef6 | 1518 | // SAFETY: `assert_len` and `is_char_boundary` do the appropriate bounds checks. |
1b1a35ee | 1519 | let chars_iter = unsafe { self.get_unchecked(start..end) }.chars(); |
d9579d0f | 1520 | |
dfeec247 | 1521 | Drain { start, end, iter: chars_iter, string: self_ptr } |
d9579d0f | 1522 | } |
c1a9b12d | 1523 | |
83c7162d | 1524 | /// Removes the specified range in the string, |
ea8adc8c XL |
1525 | /// and replaces it with the given string. |
1526 | /// The given string doesn't need to be the same length as the range. | |
7cac9316 | 1527 | /// |
7cac9316 XL |
1528 | /// # Panics |
1529 | /// | |
1530 | /// Panics if the starting point or end point do not lie on a [`char`] | |
1531 | /// boundary, or if they're out of bounds. | |
1532 | /// | |
7cac9316 XL |
1533 | /// # Examples |
1534 | /// | |
1535 | /// Basic usage: | |
1536 | /// | |
1537 | /// ``` | |
7cac9316 XL |
1538 | /// let mut s = String::from("α is alpha, β is beta"); |
1539 | /// let beta_offset = s.find('β').unwrap_or(s.len()); | |
1540 | /// | |
1541 | /// // Replace the range up until the β from the string | |
83c7162d | 1542 | /// s.replace_range(..beta_offset, "Α is capital alpha; "); |
7cac9316 XL |
1543 | /// assert_eq!(s, "Α is capital alpha; β is beta"); |
1544 | /// ``` | |
83c7162d XL |
1545 | #[stable(feature = "splice", since = "1.27.0")] |
1546 | pub fn replace_range<R>(&mut self, range: R, replace_with: &str) | |
dfeec247 XL |
1547 | where |
1548 | R: RangeBounds<usize>, | |
7cac9316 XL |
1549 | { |
1550 | // Memory safety | |
1551 | // | |
83c7162d | 1552 | // Replace_range does not have the memory safety issues of a vector Splice. |
7cac9316 | 1553 | // of the vector version. The data is just plain bytes. |
ea8adc8c | 1554 | |
94b46f34 | 1555 | match range.start_bound() { |
dfeec247 XL |
1556 | Included(&n) => assert!(self.is_char_boundary(n)), |
1557 | Excluded(&n) => assert!(self.is_char_boundary(n + 1)), | |
1558 | Unbounded => {} | |
7cac9316 | 1559 | }; |
94b46f34 | 1560 | match range.end_bound() { |
dfeec247 XL |
1561 | Included(&n) => assert!(self.is_char_boundary(n + 1)), |
1562 | Excluded(&n) => assert!(self.is_char_boundary(n)), | |
1563 | Unbounded => {} | |
7cac9316 XL |
1564 | }; |
1565 | ||
dfeec247 | 1566 | unsafe { self.as_mut_vec() }.splice(range, replace_with.bytes()); |
7cac9316 XL |
1567 | } |
1568 | ||
3b2f2976 | 1569 | /// Converts this `String` into a [`Box`]`<`[`str`]`>`. |
9cc50fc6 SL |
1570 | /// |
1571 | /// This will drop any excess capacity. | |
1572 | /// | |
3dfed10e | 1573 | /// [`str`]: prim@str |
3b2f2976 | 1574 | /// |
9cc50fc6 SL |
1575 | /// # Examples |
1576 | /// | |
1577 | /// Basic usage: | |
1578 | /// | |
1579 | /// ``` | |
1580 | /// let s = String::from("hello"); | |
c1a9b12d | 1581 | /// |
9cc50fc6 SL |
1582 | /// let b = s.into_boxed_str(); |
1583 | /// ``` | |
e9174d1e | 1584 | #[stable(feature = "box_str", since = "1.4.0")] |
83c7162d | 1585 | #[inline] |
e9174d1e | 1586 | pub fn into_boxed_str(self) -> Box<str> { |
c1a9b12d | 1587 | let slice = self.vec.into_boxed_slice(); |
041b39d2 | 1588 | unsafe { from_boxed_utf8_unchecked(slice) } |
c1a9b12d | 1589 | } |
1a4d82fc JJ |
1590 | } |
1591 | ||
1592 | impl FromUtf8Error { | |
cc61c64b XL |
1593 | /// Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`. |
1594 | /// | |
1595 | /// # Examples | |
1596 | /// | |
1597 | /// Basic usage: | |
1598 | /// | |
1599 | /// ``` | |
cc61c64b XL |
1600 | /// // some invalid bytes, in a vector |
1601 | /// let bytes = vec![0, 159]; | |
1602 | /// | |
1603 | /// let value = String::from_utf8(bytes); | |
1604 | /// | |
1605 | /// assert_eq!(&[0, 159], value.unwrap_err().as_bytes()); | |
1606 | /// ``` | |
0531ce1d | 1607 | #[stable(feature = "from_utf8_error_as_bytes", since = "1.26.0")] |
cc61c64b XL |
1608 | pub fn as_bytes(&self) -> &[u8] { |
1609 | &self.bytes[..] | |
1610 | } | |
1611 | ||
92a42be0 SL |
1612 | /// Returns the bytes that were attempted to convert to a `String`. |
1613 | /// | |
1614 | /// This method is carefully constructed to avoid allocation. It will | |
1615 | /// consume the error, moving out the bytes, so that a copy of the bytes | |
1616 | /// does not need to be made. | |
1617 | /// | |
1618 | /// # Examples | |
1619 | /// | |
1620 | /// Basic usage: | |
1621 | /// | |
1622 | /// ``` | |
1623 | /// // some invalid bytes, in a vector | |
1624 | /// let bytes = vec![0, 159]; | |
1625 | /// | |
1626 | /// let value = String::from_utf8(bytes); | |
1627 | /// | |
1628 | /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes()); | |
1629 | /// ``` | |
85aaf69f | 1630 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1631 | pub fn into_bytes(self) -> Vec<u8> { |
1632 | self.bytes | |
1633 | } | |
1a4d82fc | 1634 | |
92a42be0 SL |
1635 | /// Fetch a `Utf8Error` to get more details about the conversion failure. |
1636 | /// | |
1637 | /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may | |
1638 | /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's | |
1639 | /// an analogue to `FromUtf8Error`. See its documentation for more details | |
1640 | /// on using it. | |
1641 | /// | |
3dfed10e XL |
1642 | /// [`std::str`]: core::str |
1643 | /// [`&str`]: prim@str | |
92a42be0 SL |
1644 | /// |
1645 | /// # Examples | |
1646 | /// | |
1647 | /// Basic usage: | |
1648 | /// | |
1649 | /// ``` | |
1650 | /// // some invalid bytes, in a vector | |
1651 | /// let bytes = vec![0, 159]; | |
1652 | /// | |
1653 | /// let error = String::from_utf8(bytes).unwrap_err().utf8_error(); | |
1654 | /// | |
1655 | /// // the first byte is invalid here | |
1656 | /// assert_eq!(1, error.valid_up_to()); | |
1657 | /// ``` | |
85aaf69f | 1658 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1659 | pub fn utf8_error(&self) -> Utf8Error { |
1660 | self.error | |
1661 | } | |
1a4d82fc JJ |
1662 | } |
1663 | ||
85aaf69f SL |
1664 | #[stable(feature = "rust1", since = "1.0.0")] |
1665 | impl fmt::Display for FromUtf8Error { | |
9fa01778 | 1666 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1667 | fmt::Display::fmt(&self.error, f) |
1a4d82fc JJ |
1668 | } |
1669 | } | |
1670 | ||
85aaf69f SL |
1671 | #[stable(feature = "rust1", since = "1.0.0")] |
1672 | impl fmt::Display for FromUtf16Error { | |
9fa01778 | 1673 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1674 | fmt::Display::fmt("invalid utf-16: lone surrogate found", f) |
1a4d82fc JJ |
1675 | } |
1676 | } | |
1677 | ||
b039eaaf SL |
1678 | #[stable(feature = "rust1", since = "1.0.0")] |
1679 | impl Clone for String { | |
1680 | fn clone(&self) -> Self { | |
1681 | String { vec: self.vec.clone() } | |
1682 | } | |
1683 | ||
1684 | fn clone_from(&mut self, source: &Self) { | |
1685 | self.vec.clone_from(&source.vec); | |
1686 | } | |
1687 | } | |
1688 | ||
85aaf69f | 1689 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1690 | impl FromIterator<char> for String { |
54a0048b | 1691 | fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String { |
1a4d82fc | 1692 | let mut buf = String::new(); |
54a0048b | 1693 | buf.extend(iter); |
1a4d82fc JJ |
1694 | buf |
1695 | } | |
1696 | } | |
1697 | ||
8bb4bdeb XL |
1698 | #[stable(feature = "string_from_iter_by_ref", since = "1.17.0")] |
1699 | impl<'a> FromIterator<&'a char> for String { | |
1700 | fn from_iter<I: IntoIterator<Item = &'a char>>(iter: I) -> String { | |
1701 | let mut buf = String::new(); | |
1702 | buf.extend(iter); | |
1703 | buf | |
1704 | } | |
1705 | } | |
1706 | ||
85aaf69f | 1707 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1708 | impl<'a> FromIterator<&'a str> for String { |
54a0048b | 1709 | fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String { |
e9174d1e | 1710 | let mut buf = String::new(); |
54a0048b | 1711 | buf.extend(iter); |
e9174d1e SL |
1712 | buf |
1713 | } | |
1714 | } | |
1715 | ||
1716 | #[stable(feature = "extend_string", since = "1.4.0")] | |
1717 | impl FromIterator<String> for String { | |
54a0048b | 1718 | fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String { |
0731742a XL |
1719 | let mut iterator = iter.into_iter(); |
1720 | ||
1721 | // Because we're iterating over `String`s, we can avoid at least | |
1722 | // one allocation by getting the first string from the iterator | |
1723 | // and appending to it all the subsequent strings. | |
1724 | match iterator.next() { | |
1725 | None => String::new(), | |
1726 | Some(mut buf) => { | |
1727 | buf.extend(iterator); | |
1728 | buf | |
1729 | } | |
1730 | } | |
1a4d82fc JJ |
1731 | } |
1732 | } | |
1733 | ||
f035d41b XL |
1734 | #[stable(feature = "box_str2", since = "1.45.0")] |
1735 | impl FromIterator<Box<str>> for String { | |
1736 | fn from_iter<I: IntoIterator<Item = Box<str>>>(iter: I) -> String { | |
1737 | let mut buf = String::new(); | |
1738 | buf.extend(iter); | |
1739 | buf | |
1740 | } | |
1741 | } | |
1742 | ||
7cac9316 XL |
1743 | #[stable(feature = "herd_cows", since = "1.19.0")] |
1744 | impl<'a> FromIterator<Cow<'a, str>> for String { | |
1745 | fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String { | |
0731742a XL |
1746 | let mut iterator = iter.into_iter(); |
1747 | ||
1748 | // Because we're iterating over CoWs, we can (potentially) avoid at least | |
1749 | // one allocation by getting the first item and appending to it all the | |
1750 | // subsequent items. | |
1751 | match iterator.next() { | |
1752 | None => String::new(), | |
1753 | Some(cow) => { | |
1754 | let mut buf = cow.into_owned(); | |
1755 | buf.extend(iterator); | |
1756 | buf | |
1757 | } | |
1758 | } | |
7cac9316 XL |
1759 | } |
1760 | } | |
1761 | ||
bd371182 | 1762 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1763 | impl Extend<char> for String { |
54a0048b SL |
1764 | fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) { |
1765 | let iterator = iter.into_iter(); | |
1a4d82fc JJ |
1766 | let (lower_bound, _) = iterator.size_hint(); |
1767 | self.reserve(lower_bound); | |
0731742a | 1768 | iterator.for_each(move |c| self.push(c)); |
1a4d82fc | 1769 | } |
f9f354fc XL |
1770 | |
1771 | #[inline] | |
1772 | fn extend_one(&mut self, c: char) { | |
1773 | self.push(c); | |
1774 | } | |
1775 | ||
1776 | #[inline] | |
1777 | fn extend_reserve(&mut self, additional: usize) { | |
1778 | self.reserve(additional); | |
1779 | } | |
1a4d82fc JJ |
1780 | } |
1781 | ||
62682a34 SL |
1782 | #[stable(feature = "extend_ref", since = "1.2.0")] |
1783 | impl<'a> Extend<&'a char> for String { | |
54a0048b SL |
1784 | fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) { |
1785 | self.extend(iter.into_iter().cloned()); | |
62682a34 | 1786 | } |
f9f354fc XL |
1787 | |
1788 | #[inline] | |
1789 | fn extend_one(&mut self, &c: &'a char) { | |
1790 | self.push(c); | |
1791 | } | |
1792 | ||
1793 | #[inline] | |
1794 | fn extend_reserve(&mut self, additional: usize) { | |
1795 | self.reserve(additional); | |
1796 | } | |
62682a34 SL |
1797 | } |
1798 | ||
bd371182 | 1799 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1800 | impl<'a> Extend<&'a str> for String { |
54a0048b | 1801 | fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) { |
0731742a | 1802 | iter.into_iter().for_each(move |s| self.push_str(s)); |
1a4d82fc | 1803 | } |
f9f354fc XL |
1804 | |
1805 | #[inline] | |
1806 | fn extend_one(&mut self, s: &'a str) { | |
1807 | self.push_str(s); | |
1808 | } | |
1a4d82fc JJ |
1809 | } |
1810 | ||
f035d41b XL |
1811 | #[stable(feature = "box_str2", since = "1.45.0")] |
1812 | impl Extend<Box<str>> for String { | |
1813 | fn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I) { | |
1814 | iter.into_iter().for_each(move |s| self.push_str(&s)); | |
1815 | } | |
1816 | } | |
1817 | ||
e9174d1e SL |
1818 | #[stable(feature = "extend_string", since = "1.4.0")] |
1819 | impl Extend<String> for String { | |
54a0048b | 1820 | fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) { |
0731742a | 1821 | iter.into_iter().for_each(move |s| self.push_str(&s)); |
e9174d1e | 1822 | } |
f9f354fc XL |
1823 | |
1824 | #[inline] | |
1825 | fn extend_one(&mut self, s: String) { | |
1826 | self.push_str(&s); | |
1827 | } | |
e9174d1e SL |
1828 | } |
1829 | ||
7cac9316 XL |
1830 | #[stable(feature = "herd_cows", since = "1.19.0")] |
1831 | impl<'a> Extend<Cow<'a, str>> for String { | |
1832 | fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) { | |
0731742a | 1833 | iter.into_iter().for_each(move |s| self.push_str(&s)); |
7cac9316 | 1834 | } |
f9f354fc XL |
1835 | |
1836 | #[inline] | |
1837 | fn extend_one(&mut self, s: Cow<'a, str>) { | |
1838 | self.push_str(&s); | |
1839 | } | |
7cac9316 XL |
1840 | } |
1841 | ||
ba9703b0 XL |
1842 | /// A convenience impl that delegates to the impl for `&str`. |
1843 | /// | |
1844 | /// # Examples | |
1845 | /// | |
1846 | /// ``` | |
1847 | /// assert_eq!(String::from("Hello world").find("world"), Some(6)); | |
1848 | /// ``` | |
dfeec247 XL |
1849 | #[unstable( |
1850 | feature = "pattern", | |
1851 | reason = "API not fully fleshed out and ready to be stabilized", | |
1852 | issue = "27721" | |
1853 | )] | |
c34b1796 AL |
1854 | impl<'a, 'b> Pattern<'a> for &'b String { |
1855 | type Searcher = <&'b str as Pattern<'a>>::Searcher; | |
1856 | ||
1857 | fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher { | |
1858 | self[..].into_searcher(haystack) | |
1859 | } | |
1860 | ||
1861 | #[inline] | |
1862 | fn is_contained_in(self, haystack: &'a str) -> bool { | |
1863 | self[..].is_contained_in(haystack) | |
1864 | } | |
1865 | ||
1866 | #[inline] | |
1867 | fn is_prefix_of(self, haystack: &'a str) -> bool { | |
1868 | self[..].is_prefix_of(haystack) | |
1869 | } | |
ba9703b0 XL |
1870 | |
1871 | #[inline] | |
1872 | fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> { | |
1873 | self[..].strip_prefix_of(haystack) | |
1874 | } | |
1875 | ||
1876 | #[inline] | |
1877 | fn is_suffix_of(self, haystack: &'a str) -> bool { | |
1878 | self[..].is_suffix_of(haystack) | |
1879 | } | |
1880 | ||
1881 | #[inline] | |
1882 | fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> { | |
1883 | self[..].strip_suffix_of(haystack) | |
1884 | } | |
c34b1796 AL |
1885 | } |
1886 | ||
85aaf69f | 1887 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1888 | impl PartialEq for String { |
1889 | #[inline] | |
92a42be0 SL |
1890 | fn eq(&self, other: &String) -> bool { |
1891 | PartialEq::eq(&self[..], &other[..]) | |
1892 | } | |
1a4d82fc | 1893 | #[inline] |
92a42be0 SL |
1894 | fn ne(&self, other: &String) -> bool { |
1895 | PartialEq::ne(&self[..], &other[..]) | |
1896 | } | |
1a4d82fc JJ |
1897 | } |
1898 | ||
1899 | macro_rules! impl_eq { | |
1900 | ($lhs:ty, $rhs: ty) => { | |
85aaf69f | 1901 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 1902 | #[allow(unused_lifetimes)] |
92a42be0 | 1903 | impl<'a, 'b> PartialEq<$rhs> for $lhs { |
1a4d82fc | 1904 | #[inline] |
dfeec247 XL |
1905 | fn eq(&self, other: &$rhs) -> bool { |
1906 | PartialEq::eq(&self[..], &other[..]) | |
1907 | } | |
1a4d82fc | 1908 | #[inline] |
dfeec247 XL |
1909 | fn ne(&self, other: &$rhs) -> bool { |
1910 | PartialEq::ne(&self[..], &other[..]) | |
1911 | } | |
1a4d82fc JJ |
1912 | } |
1913 | ||
85aaf69f | 1914 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 1915 | #[allow(unused_lifetimes)] |
92a42be0 | 1916 | impl<'a, 'b> PartialEq<$lhs> for $rhs { |
1a4d82fc | 1917 | #[inline] |
dfeec247 XL |
1918 | fn eq(&self, other: &$lhs) -> bool { |
1919 | PartialEq::eq(&self[..], &other[..]) | |
1920 | } | |
1a4d82fc | 1921 | #[inline] |
dfeec247 XL |
1922 | fn ne(&self, other: &$lhs) -> bool { |
1923 | PartialEq::ne(&self[..], &other[..]) | |
1924 | } | |
1a4d82fc | 1925 | } |
dfeec247 | 1926 | }; |
1a4d82fc JJ |
1927 | } |
1928 | ||
9346a6ac | 1929 | impl_eq! { String, str } |
1a4d82fc | 1930 | impl_eq! { String, &'a str } |
9346a6ac | 1931 | impl_eq! { Cow<'a, str>, str } |
92a42be0 | 1932 | impl_eq! { Cow<'a, str>, &'b str } |
85aaf69f | 1933 | impl_eq! { Cow<'a, str>, String } |
1a4d82fc | 1934 | |
85aaf69f | 1935 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1936 | impl Default for String { |
9e0c209e | 1937 | /// Creates an empty `String`. |
85aaf69f | 1938 | #[inline] |
1a4d82fc JJ |
1939 | fn default() -> String { |
1940 | String::new() | |
1941 | } | |
1942 | } | |
1943 | ||
85aaf69f SL |
1944 | #[stable(feature = "rust1", since = "1.0.0")] |
1945 | impl fmt::Display for String { | |
1946 | #[inline] | |
9fa01778 | 1947 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1948 | fmt::Display::fmt(&**self, f) |
1a4d82fc JJ |
1949 | } |
1950 | } | |
1951 | ||
85aaf69f SL |
1952 | #[stable(feature = "rust1", since = "1.0.0")] |
1953 | impl fmt::Debug for String { | |
1954 | #[inline] | |
9fa01778 | 1955 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1956 | fmt::Debug::fmt(&**self, f) |
1a4d82fc JJ |
1957 | } |
1958 | } | |
1959 | ||
85aaf69f | 1960 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1961 | impl hash::Hash for String { |
1a4d82fc | 1962 | #[inline] |
85aaf69f | 1963 | fn hash<H: hash::Hasher>(&self, hasher: &mut H) { |
1a4d82fc JJ |
1964 | (**self).hash(hasher) |
1965 | } | |
1966 | } | |
1967 | ||
8bb4bdeb XL |
1968 | /// Implements the `+` operator for concatenating two strings. |
1969 | /// | |
1970 | /// This consumes the `String` on the left-hand side and re-uses its buffer (growing it if | |
1971 | /// necessary). This is done to avoid allocating a new `String` and copying the entire contents on | |
3dfed10e | 1972 | /// every operation, which would lead to *O*(*n*^2) running time when building an *n*-byte string by |
8bb4bdeb XL |
1973 | /// repeated concatenation. |
1974 | /// | |
1975 | /// The string on the right-hand side is only borrowed; its contents are copied into the returned | |
1976 | /// `String`. | |
1977 | /// | |
1978 | /// # Examples | |
1979 | /// | |
1980 | /// Concatenating two `String`s takes the first by value and borrows the second: | |
1981 | /// | |
1982 | /// ``` | |
1983 | /// let a = String::from("hello"); | |
1984 | /// let b = String::from(" world"); | |
1985 | /// let c = a + &b; | |
1986 | /// // `a` is moved and can no longer be used here. | |
1987 | /// ``` | |
1988 | /// | |
1989 | /// If you want to keep using the first `String`, you can clone it and append to the clone instead: | |
1990 | /// | |
1991 | /// ``` | |
1992 | /// let a = String::from("hello"); | |
1993 | /// let b = String::from(" world"); | |
1994 | /// let c = a.clone() + &b; | |
1995 | /// // `a` is still valid here. | |
1996 | /// ``` | |
1997 | /// | |
1998 | /// Concatenating `&str` slices can be done by converting the first to a `String`: | |
1999 | /// | |
2000 | /// ``` | |
2001 | /// let a = "hello"; | |
2002 | /// let b = " world"; | |
2003 | /// let c = a.to_string() + b; | |
2004 | /// ``` | |
bd371182 | 2005 | #[stable(feature = "rust1", since = "1.0.0")] |
9fa01778 | 2006 | impl Add<&str> for String { |
1a4d82fc JJ |
2007 | type Output = String; |
2008 | ||
85aaf69f | 2009 | #[inline] |
1a4d82fc JJ |
2010 | fn add(mut self, other: &str) -> String { |
2011 | self.push_str(other); | |
2012 | self | |
2013 | } | |
2014 | } | |
2015 | ||
8bb4bdeb XL |
2016 | /// Implements the `+=` operator for appending to a `String`. |
2017 | /// | |
b7449926 | 2018 | /// This has the same behavior as the [`push_str`][String::push_str] method. |
5bcae85e | 2019 | #[stable(feature = "stringaddassign", since = "1.12.0")] |
9fa01778 | 2020 | impl AddAssign<&str> for String { |
5bcae85e SL |
2021 | #[inline] |
2022 | fn add_assign(&mut self, other: &str) { | |
2023 | self.push_str(other); | |
2024 | } | |
2025 | } | |
2026 | ||
85aaf69f SL |
2027 | #[stable(feature = "rust1", since = "1.0.0")] |
2028 | impl ops::Index<ops::Range<usize>> for String { | |
1a4d82fc | 2029 | type Output = str; |
c34b1796 | 2030 | |
1a4d82fc | 2031 | #[inline] |
c34b1796 AL |
2032 | fn index(&self, index: ops::Range<usize>) -> &str { |
2033 | &self[..][index] | |
1a4d82fc JJ |
2034 | } |
2035 | } | |
85aaf69f SL |
2036 | #[stable(feature = "rust1", since = "1.0.0")] |
2037 | impl ops::Index<ops::RangeTo<usize>> for String { | |
1a4d82fc | 2038 | type Output = str; |
c34b1796 | 2039 | |
1a4d82fc | 2040 | #[inline] |
c34b1796 AL |
2041 | fn index(&self, index: ops::RangeTo<usize>) -> &str { |
2042 | &self[..][index] | |
1a4d82fc JJ |
2043 | } |
2044 | } | |
85aaf69f SL |
2045 | #[stable(feature = "rust1", since = "1.0.0")] |
2046 | impl ops::Index<ops::RangeFrom<usize>> for String { | |
1a4d82fc | 2047 | type Output = str; |
c34b1796 | 2048 | |
1a4d82fc | 2049 | #[inline] |
c34b1796 AL |
2050 | fn index(&self, index: ops::RangeFrom<usize>) -> &str { |
2051 | &self[..][index] | |
1a4d82fc JJ |
2052 | } |
2053 | } | |
85aaf69f SL |
2054 | #[stable(feature = "rust1", since = "1.0.0")] |
2055 | impl ops::Index<ops::RangeFull> for String { | |
1a4d82fc | 2056 | type Output = str; |
c34b1796 | 2057 | |
1a4d82fc | 2058 | #[inline] |
c34b1796 | 2059 | fn index(&self, _index: ops::RangeFull) -> &str { |
e9174d1e | 2060 | unsafe { str::from_utf8_unchecked(&self.vec) } |
1a4d82fc JJ |
2061 | } |
2062 | } | |
0531ce1d | 2063 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2064 | impl ops::Index<ops::RangeInclusive<usize>> for String { |
2065 | type Output = str; | |
2066 | ||
2067 | #[inline] | |
2068 | fn index(&self, index: ops::RangeInclusive<usize>) -> &str { | |
2069 | Index::index(&**self, index) | |
2070 | } | |
2071 | } | |
0531ce1d | 2072 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2073 | impl ops::Index<ops::RangeToInclusive<usize>> for String { |
2074 | type Output = str; | |
2075 | ||
2076 | #[inline] | |
2077 | fn index(&self, index: ops::RangeToInclusive<usize>) -> &str { | |
2078 | Index::index(&**self, index) | |
2079 | } | |
2080 | } | |
1a4d82fc | 2081 | |
7cac9316 | 2082 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2083 | impl ops::IndexMut<ops::Range<usize>> for String { |
2084 | #[inline] | |
2085 | fn index_mut(&mut self, index: ops::Range<usize>) -> &mut str { | |
2086 | &mut self[..][index] | |
2087 | } | |
2088 | } | |
7cac9316 | 2089 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2090 | impl ops::IndexMut<ops::RangeTo<usize>> for String { |
2091 | #[inline] | |
2092 | fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut str { | |
2093 | &mut self[..][index] | |
2094 | } | |
2095 | } | |
7cac9316 | 2096 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2097 | impl ops::IndexMut<ops::RangeFrom<usize>> for String { |
2098 | #[inline] | |
2099 | fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut str { | |
2100 | &mut self[..][index] | |
2101 | } | |
2102 | } | |
7cac9316 | 2103 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2104 | impl ops::IndexMut<ops::RangeFull> for String { |
2105 | #[inline] | |
2106 | fn index_mut(&mut self, _index: ops::RangeFull) -> &mut str { | |
cc61c64b | 2107 | unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) } |
c1a9b12d SL |
2108 | } |
2109 | } | |
0531ce1d | 2110 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2111 | impl ops::IndexMut<ops::RangeInclusive<usize>> for String { |
2112 | #[inline] | |
2113 | fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut str { | |
2114 | IndexMut::index_mut(&mut **self, index) | |
2115 | } | |
2116 | } | |
0531ce1d | 2117 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2118 | impl ops::IndexMut<ops::RangeToInclusive<usize>> for String { |
2119 | #[inline] | |
2120 | fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut str { | |
2121 | IndexMut::index_mut(&mut **self, index) | |
2122 | } | |
2123 | } | |
c1a9b12d | 2124 | |
85aaf69f | 2125 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
2126 | impl ops::Deref for String { |
2127 | type Target = str; | |
2128 | ||
85aaf69f SL |
2129 | #[inline] |
2130 | fn deref(&self) -> &str { | |
e9174d1e | 2131 | unsafe { str::from_utf8_unchecked(&self.vec) } |
1a4d82fc JJ |
2132 | } |
2133 | } | |
2134 | ||
7cac9316 | 2135 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d | 2136 | impl ops::DerefMut for String { |
85aaf69f | 2137 | #[inline] |
c1a9b12d | 2138 | fn deref_mut(&mut self) -> &mut str { |
cc61c64b | 2139 | unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) } |
1a4d82fc JJ |
2140 | } |
2141 | } | |
2142 | ||
74b04a01 | 2143 | /// A type alias for [`Infallible`]. |
92a42be0 | 2144 | /// |
74b04a01 | 2145 | /// This alias exists for backwards compatibility, and may be eventually deprecated. |
92a42be0 | 2146 | /// |
3dfed10e | 2147 | /// [`Infallible`]: core::convert::Infallible |
b039eaaf | 2148 | #[stable(feature = "str_parse_error", since = "1.5.0")] |
9fa01778 | 2149 | pub type ParseError = core::convert::Infallible; |
bd371182 AL |
2150 | |
2151 | #[stable(feature = "rust1", since = "1.0.0")] | |
1a4d82fc | 2152 | impl FromStr for String { |
9fa01778 | 2153 | type Err = core::convert::Infallible; |
1a4d82fc | 2154 | #[inline] |
74b04a01 | 2155 | fn from_str(s: &str) -> Result<String, Self::Err> { |
62682a34 | 2156 | Ok(String::from(s)) |
1a4d82fc JJ |
2157 | } |
2158 | } | |
2159 | ||
92a42be0 SL |
2160 | /// A trait for converting a value to a `String`. |
2161 | /// | |
2162 | /// This trait is automatically implemented for any type which implements the | |
2163 | /// [`Display`] trait. As such, `ToString` shouldn't be implemented directly: | |
2164 | /// [`Display`] should be implemented instead, and you get the `ToString` | |
2165 | /// implementation for free. | |
2166 | /// | |
3dfed10e | 2167 | /// [`Display`]: fmt::Display |
85aaf69f | 2168 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 2169 | pub trait ToString { |
92a42be0 SL |
2170 | /// Converts the given value to a `String`. |
2171 | /// | |
2172 | /// # Examples | |
2173 | /// | |
2174 | /// Basic usage: | |
2175 | /// | |
2176 | /// ``` | |
2177 | /// let i = 5; | |
2178 | /// let five = String::from("5"); | |
2179 | /// | |
2180 | /// assert_eq!(five, i.to_string()); | |
2181 | /// ``` | |
2c00a5a8 | 2182 | #[rustc_conversion_suggestion] |
85aaf69f | 2183 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
2184 | fn to_string(&self) -> String; |
2185 | } | |
2186 | ||
8bb4bdeb XL |
2187 | /// # Panics |
2188 | /// | |
2189 | /// In this implementation, the `to_string` method panics | |
2190 | /// if the `Display` implementation returns an error. | |
2191 | /// This indicates an incorrect `Display` implementation | |
2192 | /// since `fmt::Write for String` never returns an error itself. | |
85aaf69f SL |
2193 | #[stable(feature = "rust1", since = "1.0.0")] |
2194 | impl<T: fmt::Display + ?Sized> ToString for T { | |
3dfed10e | 2195 | // A common guideline is to not inline generic functions. However, |
29967ef6 XL |
2196 | // removing `#[inline]` from this method causes non-negligible regressions. |
2197 | // See <https://github.com/rust-lang/rust/pull/74852>, the last attempt | |
2198 | // to try to remove it. | |
85aaf69f | 2199 | #[inline] |
54a0048b | 2200 | default fn to_string(&self) -> String { |
9fa01778 | 2201 | use fmt::Write; |
1a4d82fc | 2202 | let mut buf = String::new(); |
8bb4bdeb | 2203 | buf.write_fmt(format_args!("{}", self)) |
dfeec247 | 2204 | .expect("a Display implementation returned an error unexpectedly"); |
1a4d82fc JJ |
2205 | buf |
2206 | } | |
2207 | } | |
2208 | ||
f035d41b XL |
2209 | #[stable(feature = "char_to_string_specialization", since = "1.46.0")] |
2210 | impl ToString for char { | |
2211 | #[inline] | |
2212 | fn to_string(&self) -> String { | |
2213 | String::from(self.encode_utf8(&mut [0; 4])) | |
2214 | } | |
2215 | } | |
2216 | ||
54a0048b SL |
2217 | #[stable(feature = "str_to_string_specialization", since = "1.9.0")] |
2218 | impl ToString for str { | |
2219 | #[inline] | |
2220 | fn to_string(&self) -> String { | |
2221 | String::from(self) | |
2222 | } | |
2223 | } | |
2224 | ||
8bb4bdeb | 2225 | #[stable(feature = "cow_str_to_string_specialization", since = "1.17.0")] |
9fa01778 | 2226 | impl ToString for Cow<'_, str> { |
8bb4bdeb XL |
2227 | #[inline] |
2228 | fn to_string(&self) -> String { | |
2229 | self[..].to_owned() | |
2230 | } | |
2231 | } | |
2232 | ||
2233 | #[stable(feature = "string_to_string_specialization", since = "1.17.0")] | |
2234 | impl ToString for String { | |
2235 | #[inline] | |
2236 | fn to_string(&self) -> String { | |
2237 | self.to_owned() | |
2238 | } | |
2239 | } | |
2240 | ||
85aaf69f | 2241 | #[stable(feature = "rust1", since = "1.0.0")] |
c34b1796 | 2242 | impl AsRef<str> for String { |
d9579d0f | 2243 | #[inline] |
c34b1796 AL |
2244 | fn as_ref(&self) -> &str { |
2245 | self | |
2246 | } | |
2247 | } | |
2248 | ||
74b04a01 XL |
2249 | #[stable(feature = "string_as_mut", since = "1.43.0")] |
2250 | impl AsMut<str> for String { | |
2251 | #[inline] | |
2252 | fn as_mut(&mut self) -> &mut str { | |
2253 | self | |
2254 | } | |
2255 | } | |
2256 | ||
bd371182 AL |
2257 | #[stable(feature = "rust1", since = "1.0.0")] |
2258 | impl AsRef<[u8]> for String { | |
2259 | #[inline] | |
2260 | fn as_ref(&self) -> &[u8] { | |
2261 | self.as_bytes() | |
2262 | } | |
2263 | } | |
2264 | ||
c34b1796 | 2265 | #[stable(feature = "rust1", since = "1.0.0")] |
532ac7d7 | 2266 | impl From<&str> for String { |
0bf4aa26 | 2267 | #[inline] |
532ac7d7 | 2268 | fn from(s: &str) -> String { |
54a0048b | 2269 | s.to_owned() |
c34b1796 AL |
2270 | } |
2271 | } | |
2272 | ||
ba9703b0 XL |
2273 | #[stable(feature = "from_mut_str_for_string", since = "1.44.0")] |
2274 | impl From<&mut str> for String { | |
2275 | /// Converts a `&mut str` into a `String`. | |
2276 | /// | |
2277 | /// The result is allocated on the heap. | |
2278 | #[inline] | |
2279 | fn from(s: &mut str) -> String { | |
2280 | s.to_owned() | |
2281 | } | |
2282 | } | |
2283 | ||
48663c56 XL |
2284 | #[stable(feature = "from_ref_string", since = "1.35.0")] |
2285 | impl From<&String> for String { | |
2286 | #[inline] | |
2287 | fn from(s: &String) -> String { | |
2288 | s.clone() | |
2289 | } | |
2290 | } | |
2291 | ||
cc61c64b XL |
2292 | // note: test pulls in libstd, which causes errors here |
2293 | #[cfg(not(test))] | |
7cac9316 | 2294 | #[stable(feature = "string_from_box", since = "1.18.0")] |
cc61c64b | 2295 | impl From<Box<str>> for String { |
a1dfa0c6 XL |
2296 | /// Converts the given boxed `str` slice to a `String`. |
2297 | /// It is notable that the `str` slice is owned. | |
2298 | /// | |
2299 | /// # Examples | |
2300 | /// | |
2301 | /// Basic usage: | |
2302 | /// | |
2303 | /// ``` | |
2304 | /// let s1: String = String::from("hello world"); | |
2305 | /// let s2: Box<str> = s1.into_boxed_str(); | |
2306 | /// let s3: String = String::from(s2); | |
2307 | /// | |
2308 | /// assert_eq!("hello world", s3) | |
2309 | /// ``` | |
cc61c64b XL |
2310 | fn from(s: Box<str>) -> String { |
2311 | s.into_string() | |
2312 | } | |
2313 | } | |
2314 | ||
041b39d2 XL |
2315 | #[stable(feature = "box_from_str", since = "1.20.0")] |
2316 | impl From<String> for Box<str> { | |
a1dfa0c6 XL |
2317 | /// Converts the given `String` to a boxed `str` slice that is owned. |
2318 | /// | |
2319 | /// # Examples | |
2320 | /// | |
2321 | /// Basic usage: | |
2322 | /// | |
2323 | /// ``` | |
2324 | /// let s1: String = String::from("hello world"); | |
2325 | /// let s2: Box<str> = Box::from(s1); | |
2326 | /// let s3: String = String::from(s2); | |
2327 | /// | |
2328 | /// assert_eq!("hello world", s3) | |
2329 | /// ``` | |
041b39d2 XL |
2330 | fn from(s: String) -> Box<str> { |
2331 | s.into_boxed_str() | |
cc61c64b XL |
2332 | } |
2333 | } | |
2334 | ||
c30ab7b3 SL |
2335 | #[stable(feature = "string_from_cow_str", since = "1.14.0")] |
2336 | impl<'a> From<Cow<'a, str>> for String { | |
2337 | fn from(s: Cow<'a, str>) -> String { | |
2338 | s.into_owned() | |
2339 | } | |
2340 | } | |
2341 | ||
c34b1796 AL |
2342 | #[stable(feature = "rust1", since = "1.0.0")] |
2343 | impl<'a> From<&'a str> for Cow<'a, str> { | |
2344 | #[inline] | |
2345 | fn from(s: &'a str) -> Cow<'a, str> { | |
2346 | Cow::Borrowed(s) | |
2347 | } | |
2348 | } | |
2349 | ||
2350 | #[stable(feature = "rust1", since = "1.0.0")] | |
2351 | impl<'a> From<String> for Cow<'a, str> { | |
2352 | #[inline] | |
2353 | fn from(s: String) -> Cow<'a, str> { | |
2354 | Cow::Owned(s) | |
2355 | } | |
2356 | } | |
2357 | ||
94b46f34 XL |
2358 | #[stable(feature = "cow_from_string_ref", since = "1.28.0")] |
2359 | impl<'a> From<&'a String> for Cow<'a, str> { | |
2360 | #[inline] | |
2361 | fn from(s: &'a String) -> Cow<'a, str> { | |
2362 | Cow::Borrowed(s.as_str()) | |
2363 | } | |
2364 | } | |
2365 | ||
5bcae85e SL |
2366 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] |
2367 | impl<'a> FromIterator<char> for Cow<'a, str> { | |
2368 | fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> { | |
2369 | Cow::Owned(FromIterator::from_iter(it)) | |
2370 | } | |
2371 | } | |
2372 | ||
2373 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] | |
2374 | impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str> { | |
2375 | fn from_iter<I: IntoIterator<Item = &'b str>>(it: I) -> Cow<'a, str> { | |
2376 | Cow::Owned(FromIterator::from_iter(it)) | |
2377 | } | |
2378 | } | |
2379 | ||
2380 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] | |
2381 | impl<'a> FromIterator<String> for Cow<'a, str> { | |
2382 | fn from_iter<I: IntoIterator<Item = String>>(it: I) -> Cow<'a, str> { | |
2383 | Cow::Owned(FromIterator::from_iter(it)) | |
2384 | } | |
2385 | } | |
2386 | ||
c30ab7b3 SL |
2387 | #[stable(feature = "from_string_for_vec_u8", since = "1.14.0")] |
2388 | impl From<String> for Vec<u8> { | |
a1dfa0c6 XL |
2389 | /// Converts the given `String` to a vector `Vec` that holds values of type `u8`. |
2390 | /// | |
2391 | /// # Examples | |
2392 | /// | |
2393 | /// Basic usage: | |
2394 | /// | |
2395 | /// ``` | |
2396 | /// let s1 = String::from("hello world"); | |
2397 | /// let v1 = Vec::from(s1); | |
2398 | /// | |
2399 | /// for b in v1 { | |
2400 | /// println!("{}", b); | |
2401 | /// } | |
2402 | /// ``` | |
32a655c1 | 2403 | fn from(string: String) -> Vec<u8> { |
c30ab7b3 | 2404 | string.into_bytes() |
c34b1796 AL |
2405 | } |
2406 | } | |
2407 | ||
85aaf69f SL |
2408 | #[stable(feature = "rust1", since = "1.0.0")] |
2409 | impl fmt::Write for String { | |
2410 | #[inline] | |
1a4d82fc JJ |
2411 | fn write_str(&mut self, s: &str) -> fmt::Result { |
2412 | self.push_str(s); | |
2413 | Ok(()) | |
2414 | } | |
d9579d0f AL |
2415 | |
2416 | #[inline] | |
2417 | fn write_char(&mut self, c: char) -> fmt::Result { | |
2418 | self.push(c); | |
2419 | Ok(()) | |
2420 | } | |
2421 | } | |
2422 | ||
2423 | /// A draining iterator for `String`. | |
7453a54e | 2424 | /// |
cc61c64b | 2425 | /// This struct is created by the [`drain`] method on [`String`]. See its |
7453a54e SL |
2426 | /// documentation for more. |
2427 | /// | |
3dfed10e | 2428 | /// [`drain`]: String::drain |
92a42be0 | 2429 | #[stable(feature = "drain", since = "1.6.0")] |
d9579d0f AL |
2430 | pub struct Drain<'a> { |
2431 | /// Will be used as &'a mut String in the destructor | |
2432 | string: *mut String, | |
2433 | /// Start of part to remove | |
2434 | start: usize, | |
2435 | /// End of part to remove | |
2436 | end: usize, | |
2437 | /// Current remaining range to remove | |
2438 | iter: Chars<'a>, | |
2439 | } | |
2440 | ||
8bb4bdeb | 2441 | #[stable(feature = "collection_debug", since = "1.17.0")] |
9fa01778 XL |
2442 | impl fmt::Debug for Drain<'_> { |
2443 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
1b1a35ee | 2444 | f.debug_tuple("Drain").field(&self.as_str()).finish() |
8bb4bdeb XL |
2445 | } |
2446 | } | |
2447 | ||
92a42be0 | 2448 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2449 | unsafe impl Sync for Drain<'_> {} |
92a42be0 | 2450 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2451 | unsafe impl Send for Drain<'_> {} |
d9579d0f | 2452 | |
92a42be0 | 2453 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2454 | impl Drop for Drain<'_> { |
d9579d0f AL |
2455 | fn drop(&mut self) { |
2456 | unsafe { | |
2457 | // Use Vec::drain. "Reaffirm" the bounds checks to avoid | |
2458 | // panic code being inserted again. | |
2459 | let self_vec = (*self.string).as_mut_vec(); | |
2460 | if self.start <= self.end && self.end <= self_vec.len() { | |
2461 | self_vec.drain(self.start..self.end); | |
2462 | } | |
2463 | } | |
2464 | } | |
2465 | } | |
2466 | ||
1b1a35ee XL |
2467 | impl<'a> Drain<'a> { |
2468 | /// Returns the remaining (sub)string of this iterator as a slice. | |
2469 | /// | |
2470 | /// # Examples | |
2471 | /// | |
2472 | /// ``` | |
2473 | /// #![feature(string_drain_as_str)] | |
2474 | /// let mut s = String::from("abc"); | |
2475 | /// let mut drain = s.drain(..); | |
2476 | /// assert_eq!(drain.as_str(), "abc"); | |
2477 | /// let _ = drain.next().unwrap(); | |
2478 | /// assert_eq!(drain.as_str(), "bc"); | |
2479 | /// ``` | |
2480 | #[unstable(feature = "string_drain_as_str", issue = "76905")] // Note: uncomment AsRef impls below when stabilizing. | |
2481 | pub fn as_str(&self) -> &str { | |
2482 | self.iter.as_str() | |
2483 | } | |
2484 | } | |
2485 | ||
2486 | // Uncomment when stabilizing `string_drain_as_str`. | |
2487 | // #[unstable(feature = "string_drain_as_str", issue = "76905")] | |
2488 | // impl<'a> AsRef<str> for Drain<'a> { | |
2489 | // fn as_ref(&self) -> &str { | |
2490 | // self.as_str() | |
2491 | // } | |
2492 | // } | |
2493 | // | |
2494 | // #[unstable(feature = "string_drain_as_str", issue = "76905")] | |
2495 | // impl<'a> AsRef<[u8]> for Drain<'a> { | |
2496 | // fn as_ref(&self) -> &[u8] { | |
2497 | // self.as_str().as_bytes() | |
2498 | // } | |
2499 | // } | |
2500 | ||
92a42be0 | 2501 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2502 | impl Iterator for Drain<'_> { |
d9579d0f AL |
2503 | type Item = char; |
2504 | ||
2505 | #[inline] | |
2506 | fn next(&mut self) -> Option<char> { | |
2507 | self.iter.next() | |
2508 | } | |
2509 | ||
2510 | fn size_hint(&self) -> (usize, Option<usize>) { | |
2511 | self.iter.size_hint() | |
2512 | } | |
416331ca XL |
2513 | |
2514 | #[inline] | |
2515 | fn last(mut self) -> Option<char> { | |
2516 | self.next_back() | |
2517 | } | |
d9579d0f AL |
2518 | } |
2519 | ||
92a42be0 | 2520 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2521 | impl DoubleEndedIterator for Drain<'_> { |
d9579d0f AL |
2522 | #[inline] |
2523 | fn next_back(&mut self) -> Option<char> { | |
2524 | self.iter.next_back() | |
2525 | } | |
1a4d82fc | 2526 | } |
9e0c209e | 2527 | |
0531ce1d | 2528 | #[stable(feature = "fused", since = "1.26.0")] |
9fa01778 | 2529 | impl FusedIterator for Drain<'_> {} |
f035d41b XL |
2530 | |
2531 | #[stable(feature = "from_char_for_string", since = "1.46.0")] | |
2532 | impl From<char> for String { | |
2533 | #[inline] | |
2534 | fn from(c: char) -> Self { | |
2535 | c.to_string() | |
2536 | } | |
2537 | } |