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