alloc/slice.rs
1//! Utilities for the slice primitive type.
2//!
3//! *[See also the slice primitive type](slice).*
4//!
5//! Most of the structs in this module are iterator types which can only be created
6//! using a certain function. For example, `slice.iter()` yields an [`Iter`].
7//!
8//! A few functions are provided to create a slice from a value reference
9//! or from a raw pointer.
10#![stable(feature = "rust1", since = "1.0.0")]
11
12use core::borrow::{Borrow, BorrowMut};
13#[cfg(not(no_global_oom_handling))]
14use core::cmp::Ordering::{self, Less};
15#[cfg(not(no_global_oom_handling))]
16use core::mem::MaybeUninit;
17#[cfg(not(no_global_oom_handling))]
18use core::ptr;
19#[unstable(feature = "array_chunks", issue = "74985")]
20pub use core::slice::ArrayChunks;
21#[unstable(feature = "array_chunks", issue = "74985")]
22pub use core::slice::ArrayChunksMut;
23#[unstable(feature = "array_windows", issue = "75027")]
24pub use core::slice::ArrayWindows;
25#[stable(feature = "inherent_ascii_escape", since = "1.60.0")]
26pub use core::slice::EscapeAscii;
27#[stable(feature = "get_many_mut", since = "1.86.0")]
28pub use core::slice::GetDisjointMutError;
29#[stable(feature = "slice_get_slice", since = "1.28.0")]
30pub use core::slice::SliceIndex;
31#[cfg(not(no_global_oom_handling))]
32use core::slice::sort;
33#[stable(feature = "slice_group_by", since = "1.77.0")]
34pub use core::slice::{ChunkBy, ChunkByMut};
35#[stable(feature = "rust1", since = "1.0.0")]
36pub use core::slice::{Chunks, Windows};
37#[stable(feature = "chunks_exact", since = "1.31.0")]
38pub use core::slice::{ChunksExact, ChunksExactMut};
39#[stable(feature = "rust1", since = "1.0.0")]
40pub use core::slice::{ChunksMut, Split, SplitMut};
41#[stable(feature = "rust1", since = "1.0.0")]
42pub use core::slice::{Iter, IterMut};
43#[stable(feature = "rchunks", since = "1.31.0")]
44pub use core::slice::{RChunks, RChunksExact, RChunksExactMut, RChunksMut};
45#[stable(feature = "slice_rsplit", since = "1.27.0")]
46pub use core::slice::{RSplit, RSplitMut};
47#[stable(feature = "rust1", since = "1.0.0")]
48pub use core::slice::{RSplitN, RSplitNMut, SplitN, SplitNMut};
49#[stable(feature = "split_inclusive", since = "1.51.0")]
50pub use core::slice::{SplitInclusive, SplitInclusiveMut};
51#[stable(feature = "from_ref", since = "1.28.0")]
52pub use core::slice::{from_mut, from_ref};
53#[unstable(feature = "slice_from_ptr_range", issue = "89792")]
54pub use core::slice::{from_mut_ptr_range, from_ptr_range};
55#[stable(feature = "rust1", since = "1.0.0")]
56pub use core::slice::{from_raw_parts, from_raw_parts_mut};
57#[unstable(feature = "slice_range", issue = "76393")]
58pub use core::slice::{range, try_range};
59
60////////////////////////////////////////////////////////////////////////////////
61// Basic slice extension methods
62////////////////////////////////////////////////////////////////////////////////
63use crate::alloc::Allocator;
64#[cfg(not(no_global_oom_handling))]
65use crate::alloc::Global;
66#[cfg(not(no_global_oom_handling))]
67use crate::borrow::ToOwned;
68use crate::boxed::Box;
69use crate::vec::Vec;
70
71impl<T> [T] {
72 /// Sorts the slice, preserving initial order of equal elements.
73 ///
74 /// This sort is stable (i.e., does not reorder equal elements) and *O*(*n* \* log(*n*))
75 /// worst-case.
76 ///
77 /// If the implementation of [`Ord`] for `T` does not implement a [total order], the function
78 /// may panic; even if the function exits normally, the resulting order of elements in the slice
79 /// is unspecified. See also the note on panicking below.
80 ///
81 /// When applicable, unstable sorting is preferred because it is generally faster than stable
82 /// sorting and it doesn't allocate auxiliary memory. See
83 /// [`sort_unstable`](slice::sort_unstable). The exception are partially sorted slices, which
84 /// may be better served with `slice::sort`.
85 ///
86 /// Sorting types that only implement [`PartialOrd`] such as [`f32`] and [`f64`] require
87 /// additional precautions. For example, `f32::NAN != f32::NAN`, which doesn't fulfill the
88 /// reflexivity requirement of [`Ord`]. By using an alternative comparison function with
89 /// `slice::sort_by` such as [`f32::total_cmp`] or [`f64::total_cmp`] that defines a [total
90 /// order] users can sort slices containing floating-point values. Alternatively, if all values
91 /// in the slice are guaranteed to be in a subset for which [`PartialOrd::partial_cmp`] forms a
92 /// [total order], it's possible to sort the slice with `sort_by(|a, b|
93 /// a.partial_cmp(b).unwrap())`.
94 ///
95 /// # Current implementation
96 ///
97 /// The current implementation is based on [driftsort] by Orson Peters and Lukas Bergdoll, which
98 /// combines the fast average case of quicksort with the fast worst case and partial run
99 /// detection of mergesort, achieving linear time on fully sorted and reversed inputs. On inputs
100 /// with k distinct elements, the expected time to sort the data is *O*(*n* \* log(*k*)).
101 ///
102 /// The auxiliary memory allocation behavior depends on the input length. Short slices are
103 /// handled without allocation, medium sized slices allocate `self.len()` and beyond that it
104 /// clamps at `self.len() / 2`.
105 ///
106 /// # Panics
107 ///
108 /// May panic if the implementation of [`Ord`] for `T` does not implement a [total order], or if
109 /// the [`Ord`] implementation itself panics.
110 ///
111 /// All safe functions on slices preserve the invariant that even if the function panics, all
112 /// original elements will remain in the slice and any possible modifications via interior
113 /// mutability are observed in the input. This ensures that recovery code (for instance inside
114 /// of a `Drop` or following a `catch_unwind`) will still have access to all the original
115 /// elements. For instance, if the slice belongs to a `Vec`, the `Vec::drop` method will be able
116 /// to dispose of all contained elements.
117 ///
118 /// # Examples
119 ///
120 /// ```
121 /// let mut v = [4, -5, 1, -3, 2];
122 ///
123 /// v.sort();
124 /// assert_eq!(v, [-5, -3, 1, 2, 4]);
125 /// ```
126 ///
127 /// [driftsort]: https://github.com/Voultapher/driftsort
128 /// [total order]: https://en.wikipedia.org/wiki/Total_order
129 #[cfg(not(no_global_oom_handling))]
130 #[rustc_allow_incoherent_impl]
131 #[stable(feature = "rust1", since = "1.0.0")]
132 #[inline]
133 pub fn sort(&mut self)
134 where
135 T: Ord,
136 {
137 stable_sort(self, T::lt);
138 }
139
140 /// Sorts the slice with a comparison function, preserving initial order of equal elements.
141 ///
142 /// This sort is stable (i.e., does not reorder equal elements) and *O*(*n* \* log(*n*))
143 /// worst-case.
144 ///
145 /// If the comparison function `compare` does not implement a [total order], the function may
146 /// panic; even if the function exits normally, the resulting order of elements in the slice is
147 /// unspecified. See also the note on panicking below.
148 ///
149 /// For example `|a, b| (a - b).cmp(a)` is a comparison function that is neither transitive nor
150 /// reflexive nor total, `a < b < c < a` with `a = 1, b = 2, c = 3`. For more information and
151 /// examples see the [`Ord`] documentation.
152 ///
153 /// # Current implementation
154 ///
155 /// The current implementation is based on [driftsort] by Orson Peters and Lukas Bergdoll, which
156 /// combines the fast average case of quicksort with the fast worst case and partial run
157 /// detection of mergesort, achieving linear time on fully sorted and reversed inputs. On inputs
158 /// with k distinct elements, the expected time to sort the data is *O*(*n* \* log(*k*)).
159 ///
160 /// The auxiliary memory allocation behavior depends on the input length. Short slices are
161 /// handled without allocation, medium sized slices allocate `self.len()` and beyond that it
162 /// clamps at `self.len() / 2`.
163 ///
164 /// # Panics
165 ///
166 /// May panic if `compare` does not implement a [total order], or if `compare` itself panics.
167 ///
168 /// All safe functions on slices preserve the invariant that even if the function panics, all
169 /// original elements will remain in the slice and any possible modifications via interior
170 /// mutability are observed in the input. This ensures that recovery code (for instance inside
171 /// of a `Drop` or following a `catch_unwind`) will still have access to all the original
172 /// elements. For instance, if the slice belongs to a `Vec`, the `Vec::drop` method will be able
173 /// to dispose of all contained elements.
174 ///
175 /// # Examples
176 ///
177 /// ```
178 /// let mut v = [4, -5, 1, -3, 2];
179 /// v.sort_by(|a, b| a.cmp(b));
180 /// assert_eq!(v, [-5, -3, 1, 2, 4]);
181 ///
182 /// // reverse sorting
183 /// v.sort_by(|a, b| b.cmp(a));
184 /// assert_eq!(v, [4, 2, 1, -3, -5]);
185 /// ```
186 ///
187 /// [driftsort]: https://github.com/Voultapher/driftsort
188 /// [total order]: https://en.wikipedia.org/wiki/Total_order
189 #[cfg(not(no_global_oom_handling))]
190 #[rustc_allow_incoherent_impl]
191 #[stable(feature = "rust1", since = "1.0.0")]
192 #[inline]
193 pub fn sort_by<F>(&mut self, mut compare: F)
194 where
195 F: FnMut(&T, &T) -> Ordering,
196 {
197 stable_sort(self, |a, b| compare(a, b) == Less);
198 }
199
200 /// Sorts the slice with a key extraction function, preserving initial order of equal elements.
201 ///
202 /// This sort is stable (i.e., does not reorder equal elements) and *O*(*m* \* *n* \* log(*n*))
203 /// worst-case, where the key function is *O*(*m*).
204 ///
205 /// If the implementation of [`Ord`] for `K` does not implement a [total order], the function
206 /// may panic; even if the function exits normally, the resulting order of elements in the slice
207 /// is unspecified. See also the note on panicking below.
208 ///
209 /// # Current implementation
210 ///
211 /// The current implementation is based on [driftsort] by Orson Peters and Lukas Bergdoll, which
212 /// combines the fast average case of quicksort with the fast worst case and partial run
213 /// detection of mergesort, achieving linear time on fully sorted and reversed inputs. On inputs
214 /// with k distinct elements, the expected time to sort the data is *O*(*n* \* log(*k*)).
215 ///
216 /// The auxiliary memory allocation behavior depends on the input length. Short slices are
217 /// handled without allocation, medium sized slices allocate `self.len()` and beyond that it
218 /// clamps at `self.len() / 2`.
219 ///
220 /// # Panics
221 ///
222 /// May panic if the implementation of [`Ord`] for `K` does not implement a [total order], or if
223 /// the [`Ord`] implementation or the key-function `f` panics.
224 ///
225 /// All safe functions on slices preserve the invariant that even if the function panics, all
226 /// original elements will remain in the slice and any possible modifications via interior
227 /// mutability are observed in the input. This ensures that recovery code (for instance inside
228 /// of a `Drop` or following a `catch_unwind`) will still have access to all the original
229 /// elements. For instance, if the slice belongs to a `Vec`, the `Vec::drop` method will be able
230 /// to dispose of all contained elements.
231 ///
232 /// # Examples
233 ///
234 /// ```
235 /// let mut v = [4i32, -5, 1, -3, 2];
236 ///
237 /// v.sort_by_key(|k| k.abs());
238 /// assert_eq!(v, [1, 2, -3, 4, -5]);
239 /// ```
240 ///
241 /// [driftsort]: https://github.com/Voultapher/driftsort
242 /// [total order]: https://en.wikipedia.org/wiki/Total_order
243 #[cfg(not(no_global_oom_handling))]
244 #[rustc_allow_incoherent_impl]
245 #[stable(feature = "slice_sort_by_key", since = "1.7.0")]
246 #[inline]
247 pub fn sort_by_key<K, F>(&mut self, mut f: F)
248 where
249 F: FnMut(&T) -> K,
250 K: Ord,
251 {
252 stable_sort(self, |a, b| f(a).lt(&f(b)));
253 }
254
255 /// Sorts the slice with a key extraction function, preserving initial order of equal elements.
256 ///
257 /// This sort is stable (i.e., does not reorder equal elements) and *O*(*m* \* *n* + *n* \*
258 /// log(*n*)) worst-case, where the key function is *O*(*m*).
259 ///
260 /// During sorting, the key function is called at most once per element, by using temporary
261 /// storage to remember the results of key evaluation. The order of calls to the key function is
262 /// unspecified and may change in future versions of the standard library.
263 ///
264 /// If the implementation of [`Ord`] for `K` does not implement a [total order], the function
265 /// may panic; even if the function exits normally, the resulting order of elements in the slice
266 /// is unspecified. See also the note on panicking below.
267 ///
268 /// For simple key functions (e.g., functions that are property accesses or basic operations),
269 /// [`sort_by_key`](slice::sort_by_key) is likely to be faster.
270 ///
271 /// # Current implementation
272 ///
273 /// The current implementation is based on [instruction-parallel-network sort][ipnsort] by Lukas
274 /// Bergdoll, which combines the fast average case of randomized quicksort with the fast worst
275 /// case of heapsort, while achieving linear time on fully sorted and reversed inputs. And
276 /// *O*(*k* \* log(*n*)) where *k* is the number of distinct elements in the input. It leverages
277 /// superscalar out-of-order execution capabilities commonly found in CPUs, to efficiently
278 /// perform the operation.
279 ///
280 /// In the worst case, the algorithm allocates temporary storage in a `Vec<(K, usize)>` the
281 /// length of the slice.
282 ///
283 /// # Panics
284 ///
285 /// May panic if the implementation of [`Ord`] for `K` does not implement a [total order], or if
286 /// the [`Ord`] implementation panics.
287 ///
288 /// All safe functions on slices preserve the invariant that even if the function panics, all
289 /// original elements will remain in the slice and any possible modifications via interior
290 /// mutability are observed in the input. This ensures that recovery code (for instance inside
291 /// of a `Drop` or following a `catch_unwind`) will still have access to all the original
292 /// elements. For instance, if the slice belongs to a `Vec`, the `Vec::drop` method will be able
293 /// to dispose of all contained elements.
294 ///
295 /// # Examples
296 ///
297 /// ```
298 /// let mut v = [4i32, -5, 1, -3, 2, 10];
299 ///
300 /// // Strings are sorted by lexicographical order.
301 /// v.sort_by_cached_key(|k| k.to_string());
302 /// assert_eq!(v, [-3, -5, 1, 10, 2, 4]);
303 /// ```
304 ///
305 /// [ipnsort]: https://github.com/Voultapher/sort-research-rs/tree/main/ipnsort
306 /// [total order]: https://en.wikipedia.org/wiki/Total_order
307 #[cfg(not(no_global_oom_handling))]
308 #[rustc_allow_incoherent_impl]
309 #[stable(feature = "slice_sort_by_cached_key", since = "1.34.0")]
310 #[inline]
311 pub fn sort_by_cached_key<K, F>(&mut self, f: F)
312 where
313 F: FnMut(&T) -> K,
314 K: Ord,
315 {
316 // Helper macro for indexing our vector by the smallest possible type, to reduce allocation.
317 macro_rules! sort_by_key {
318 ($t:ty, $slice:ident, $f:ident) => {{
319 let mut indices: Vec<_> =
320 $slice.iter().map($f).enumerate().map(|(i, k)| (k, i as $t)).collect();
321 // The elements of `indices` are unique, as they are indexed, so any sort will be
322 // stable with respect to the original slice. We use `sort_unstable` here because
323 // it requires no memory allocation.
324 indices.sort_unstable();
325 for i in 0..$slice.len() {
326 let mut index = indices[i].1;
327 while (index as usize) < i {
328 index = indices[index as usize].1;
329 }
330 indices[i].1 = index;
331 $slice.swap(i, index as usize);
332 }
333 }};
334 }
335
336 let len = self.len();
337 if len < 2 {
338 return;
339 }
340
341 // Avoids binary-size usage in cases where the alignment doesn't work out to make this
342 // beneficial or on 32-bit platforms.
343 let is_using_u32_as_idx_type_helpful =
344 const { size_of::<(K, u32)>() < size_of::<(K, usize)>() };
345
346 // It's possible to instantiate this for u8 and u16 but, doing so is very wasteful in terms
347 // of compile-times and binary-size, the peak saved heap memory for u16 is (u8 + u16) -> 4
348 // bytes * u16::MAX vs (u8 + u32) -> 8 bytes * u16::MAX, the saved heap memory is at peak
349 // ~262KB.
350 if is_using_u32_as_idx_type_helpful && len <= (u32::MAX as usize) {
351 return sort_by_key!(u32, self, f);
352 }
353
354 sort_by_key!(usize, self, f)
355 }
356
357 /// Copies `self` into a new `Vec`.
358 ///
359 /// # Examples
360 ///
361 /// ```
362 /// let s = [10, 40, 30];
363 /// let x = s.to_vec();
364 /// // Here, `s` and `x` can be modified independently.
365 /// ```
366 #[cfg(not(no_global_oom_handling))]
367 #[rustc_allow_incoherent_impl]
368 #[rustc_conversion_suggestion]
369 #[stable(feature = "rust1", since = "1.0.0")]
370 #[inline]
371 pub fn to_vec(&self) -> Vec<T>
372 where
373 T: Clone,
374 {
375 self.to_vec_in(Global)
376 }
377
378 /// Copies `self` into a new `Vec` with an allocator.
379 ///
380 /// # Examples
381 ///
382 /// ```
383 /// #![feature(allocator_api)]
384 ///
385 /// use std::alloc::System;
386 ///
387 /// let s = [10, 40, 30];
388 /// let x = s.to_vec_in(System);
389 /// // Here, `s` and `x` can be modified independently.
390 /// ```
391 #[cfg(not(no_global_oom_handling))]
392 #[rustc_allow_incoherent_impl]
393 #[inline]
394 #[unstable(feature = "allocator_api", issue = "32838")]
395 pub fn to_vec_in<A: Allocator>(&self, alloc: A) -> Vec<T, A>
396 where
397 T: Clone,
398 {
399 return T::to_vec(self, alloc);
400
401 trait ConvertVec {
402 fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A>
403 where
404 Self: Sized;
405 }
406
407 impl<T: Clone> ConvertVec for T {
408 #[inline]
409 default fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A> {
410 struct DropGuard<'a, T, A: Allocator> {
411 vec: &'a mut Vec<T, A>,
412 num_init: usize,
413 }
414 impl<'a, T, A: Allocator> Drop for DropGuard<'a, T, A> {
415 #[inline]
416 fn drop(&mut self) {
417 // SAFETY:
418 // items were marked initialized in the loop below
419 unsafe {
420 self.vec.set_len(self.num_init);
421 }
422 }
423 }
424 let mut vec = Vec::with_capacity_in(s.len(), alloc);
425 let mut guard = DropGuard { vec: &mut vec, num_init: 0 };
426 let slots = guard.vec.spare_capacity_mut();
427 // .take(slots.len()) is necessary for LLVM to remove bounds checks
428 // and has better codegen than zip.
429 for (i, b) in s.iter().enumerate().take(slots.len()) {
430 guard.num_init = i;
431 slots[i].write(b.clone());
432 }
433 core::mem::forget(guard);
434 // SAFETY:
435 // the vec was allocated and initialized above to at least this length.
436 unsafe {
437 vec.set_len(s.len());
438 }
439 vec
440 }
441 }
442
443 impl<T: Copy> ConvertVec for T {
444 #[inline]
445 fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A> {
446 let mut v = Vec::with_capacity_in(s.len(), alloc);
447 // SAFETY:
448 // allocated above with the capacity of `s`, and initialize to `s.len()` in
449 // ptr::copy_to_non_overlapping below.
450 unsafe {
451 s.as_ptr().copy_to_nonoverlapping(v.as_mut_ptr(), s.len());
452 v.set_len(s.len());
453 }
454 v
455 }
456 }
457 }
458
459 /// Converts `self` into a vector without clones or allocation.
460 ///
461 /// The resulting vector can be converted back into a box via
462 /// `Vec<T>`'s `into_boxed_slice` method.
463 ///
464 /// # Examples
465 ///
466 /// ```
467 /// let s: Box<[i32]> = Box::new([10, 40, 30]);
468 /// let x = s.into_vec();
469 /// // `s` cannot be used anymore because it has been converted into `x`.
470 ///
471 /// assert_eq!(x, vec![10, 40, 30]);
472 /// ```
473 #[rustc_allow_incoherent_impl]
474 #[stable(feature = "rust1", since = "1.0.0")]
475 #[inline]
476 #[rustc_diagnostic_item = "slice_into_vec"]
477 pub fn into_vec<A: Allocator>(self: Box<Self, A>) -> Vec<T, A> {
478 unsafe {
479 let len = self.len();
480 let (b, alloc) = Box::into_raw_with_allocator(self);
481 Vec::from_raw_parts_in(b as *mut T, len, len, alloc)
482 }
483 }
484
485 /// Creates a vector by copying a slice `n` times.
486 ///
487 /// # Panics
488 ///
489 /// This function will panic if the capacity would overflow.
490 ///
491 /// # Examples
492 ///
493 /// Basic usage:
494 ///
495 /// ```
496 /// assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]);
497 /// ```
498 ///
499 /// A panic upon overflow:
500 ///
501 /// ```should_panic
502 /// // this will panic at runtime
503 /// b"0123456789abcdef".repeat(usize::MAX);
504 /// ```
505 #[rustc_allow_incoherent_impl]
506 #[cfg(not(no_global_oom_handling))]
507 #[stable(feature = "repeat_generic_slice", since = "1.40.0")]
508 pub fn repeat(&self, n: usize) -> Vec<T>
509 where
510 T: Copy,
511 {
512 if n == 0 {
513 return Vec::new();
514 }
515
516 // If `n` is larger than zero, it can be split as
517 // `n = 2^expn + rem (2^expn > rem, expn >= 0, rem >= 0)`.
518 // `2^expn` is the number represented by the leftmost '1' bit of `n`,
519 // and `rem` is the remaining part of `n`.
520
521 // Using `Vec` to access `set_len()`.
522 let capacity = self.len().checked_mul(n).expect("capacity overflow");
523 let mut buf = Vec::with_capacity(capacity);
524
525 // `2^expn` repetition is done by doubling `buf` `expn`-times.
526 buf.extend(self);
527 {
528 let mut m = n >> 1;
529 // If `m > 0`, there are remaining bits up to the leftmost '1'.
530 while m > 0 {
531 // `buf.extend(buf)`:
532 unsafe {
533 ptr::copy_nonoverlapping::<T>(
534 buf.as_ptr(),
535 (buf.as_mut_ptr()).add(buf.len()),
536 buf.len(),
537 );
538 // `buf` has capacity of `self.len() * n`.
539 let buf_len = buf.len();
540 buf.set_len(buf_len * 2);
541 }
542
543 m >>= 1;
544 }
545 }
546
547 // `rem` (`= n - 2^expn`) repetition is done by copying
548 // first `rem` repetitions from `buf` itself.
549 let rem_len = capacity - buf.len(); // `self.len() * rem`
550 if rem_len > 0 {
551 // `buf.extend(buf[0 .. rem_len])`:
552 unsafe {
553 // This is non-overlapping since `2^expn > rem`.
554 ptr::copy_nonoverlapping::<T>(
555 buf.as_ptr(),
556 (buf.as_mut_ptr()).add(buf.len()),
557 rem_len,
558 );
559 // `buf.len() + rem_len` equals to `buf.capacity()` (`= self.len() * n`).
560 buf.set_len(capacity);
561 }
562 }
563 buf
564 }
565
566 /// Flattens a slice of `T` into a single value `Self::Output`.
567 ///
568 /// # Examples
569 ///
570 /// ```
571 /// assert_eq!(["hello", "world"].concat(), "helloworld");
572 /// assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]);
573 /// ```
574 #[rustc_allow_incoherent_impl]
575 #[stable(feature = "rust1", since = "1.0.0")]
576 pub fn concat<Item: ?Sized>(&self) -> <Self as Concat<Item>>::Output
577 where
578 Self: Concat<Item>,
579 {
580 Concat::concat(self)
581 }
582
583 /// Flattens a slice of `T` into a single value `Self::Output`, placing a
584 /// given separator between each.
585 ///
586 /// # Examples
587 ///
588 /// ```
589 /// assert_eq!(["hello", "world"].join(" "), "hello world");
590 /// assert_eq!([[1, 2], [3, 4]].join(&0), [1, 2, 0, 3, 4]);
591 /// assert_eq!([[1, 2], [3, 4]].join(&[0, 0][..]), [1, 2, 0, 0, 3, 4]);
592 /// ```
593 #[rustc_allow_incoherent_impl]
594 #[stable(feature = "rename_connect_to_join", since = "1.3.0")]
595 pub fn join<Separator>(&self, sep: Separator) -> <Self as Join<Separator>>::Output
596 where
597 Self: Join<Separator>,
598 {
599 Join::join(self, sep)
600 }
601
602 /// Flattens a slice of `T` into a single value `Self::Output`, placing a
603 /// given separator between each.
604 ///
605 /// # Examples
606 ///
607 /// ```
608 /// # #![allow(deprecated)]
609 /// assert_eq!(["hello", "world"].connect(" "), "hello world");
610 /// assert_eq!([[1, 2], [3, 4]].connect(&0), [1, 2, 0, 3, 4]);
611 /// ```
612 #[rustc_allow_incoherent_impl]
613 #[stable(feature = "rust1", since = "1.0.0")]
614 #[deprecated(since = "1.3.0", note = "renamed to join", suggestion = "join")]
615 pub fn connect<Separator>(&self, sep: Separator) -> <Self as Join<Separator>>::Output
616 where
617 Self: Join<Separator>,
618 {
619 Join::join(self, sep)
620 }
621}
622
623impl [u8] {
624 /// Returns a vector containing a copy of this slice where each byte
625 /// is mapped to its ASCII upper case equivalent.
626 ///
627 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
628 /// but non-ASCII letters are unchanged.
629 ///
630 /// To uppercase the value in-place, use [`make_ascii_uppercase`].
631 ///
632 /// [`make_ascii_uppercase`]: slice::make_ascii_uppercase
633 #[cfg(not(no_global_oom_handling))]
634 #[rustc_allow_incoherent_impl]
635 #[must_use = "this returns the uppercase bytes as a new Vec, \
636 without modifying the original"]
637 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
638 #[inline]
639 pub fn to_ascii_uppercase(&self) -> Vec<u8> {
640 let mut me = self.to_vec();
641 me.make_ascii_uppercase();
642 me
643 }
644
645 /// Returns a vector containing a copy of this slice where each byte
646 /// is mapped to its ASCII lower case equivalent.
647 ///
648 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
649 /// but non-ASCII letters are unchanged.
650 ///
651 /// To lowercase the value in-place, use [`make_ascii_lowercase`].
652 ///
653 /// [`make_ascii_lowercase`]: slice::make_ascii_lowercase
654 #[cfg(not(no_global_oom_handling))]
655 #[rustc_allow_incoherent_impl]
656 #[must_use = "this returns the lowercase bytes as a new Vec, \
657 without modifying the original"]
658 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
659 #[inline]
660 pub fn to_ascii_lowercase(&self) -> Vec<u8> {
661 let mut me = self.to_vec();
662 me.make_ascii_lowercase();
663 me
664 }
665}
666
667////////////////////////////////////////////////////////////////////////////////
668// Extension traits for slices over specific kinds of data
669////////////////////////////////////////////////////////////////////////////////
670
671/// Helper trait for [`[T]::concat`](slice::concat).
672///
673/// Note: the `Item` type parameter is not used in this trait,
674/// but it allows impls to be more generic.
675/// Without it, we get this error:
676///
677/// ```error
678/// error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predica
679/// --> library/alloc/src/slice.rs:608:6
680/// |
681/// 608 | impl<T: Clone, V: Borrow<[T]>> Concat for [V] {
682/// | ^ unconstrained type parameter
683/// ```
684///
685/// This is because there could exist `V` types with multiple `Borrow<[_]>` impls,
686/// such that multiple `T` types would apply:
687///
688/// ```
689/// # #[allow(dead_code)]
690/// pub struct Foo(Vec<u32>, Vec<String>);
691///
692/// impl std::borrow::Borrow<[u32]> for Foo {
693/// fn borrow(&self) -> &[u32] { &self.0 }
694/// }
695///
696/// impl std::borrow::Borrow<[String]> for Foo {
697/// fn borrow(&self) -> &[String] { &self.1 }
698/// }
699/// ```
700#[unstable(feature = "slice_concat_trait", issue = "27747")]
701pub trait Concat<Item: ?Sized> {
702 #[unstable(feature = "slice_concat_trait", issue = "27747")]
703 /// The resulting type after concatenation
704 type Output;
705
706 /// Implementation of [`[T]::concat`](slice::concat)
707 #[unstable(feature = "slice_concat_trait", issue = "27747")]
708 fn concat(slice: &Self) -> Self::Output;
709}
710
711/// Helper trait for [`[T]::join`](slice::join)
712#[unstable(feature = "slice_concat_trait", issue = "27747")]
713pub trait Join<Separator> {
714 #[unstable(feature = "slice_concat_trait", issue = "27747")]
715 /// The resulting type after concatenation
716 type Output;
717
718 /// Implementation of [`[T]::join`](slice::join)
719 #[unstable(feature = "slice_concat_trait", issue = "27747")]
720 fn join(slice: &Self, sep: Separator) -> Self::Output;
721}
722
723#[cfg(not(no_global_oom_handling))]
724#[unstable(feature = "slice_concat_ext", issue = "27747")]
725impl<T: Clone, V: Borrow<[T]>> Concat<T> for [V] {
726 type Output = Vec<T>;
727
728 fn concat(slice: &Self) -> Vec<T> {
729 let size = slice.iter().map(|slice| slice.borrow().len()).sum();
730 let mut result = Vec::with_capacity(size);
731 for v in slice {
732 result.extend_from_slice(v.borrow())
733 }
734 result
735 }
736}
737
738#[cfg(not(no_global_oom_handling))]
739#[unstable(feature = "slice_concat_ext", issue = "27747")]
740impl<T: Clone, V: Borrow<[T]>> Join<&T> for [V] {
741 type Output = Vec<T>;
742
743 fn join(slice: &Self, sep: &T) -> Vec<T> {
744 let mut iter = slice.iter();
745 let first = match iter.next() {
746 Some(first) => first,
747 None => return vec![],
748 };
749 let size = slice.iter().map(|v| v.borrow().len()).sum::<usize>() + slice.len() - 1;
750 let mut result = Vec::with_capacity(size);
751 result.extend_from_slice(first.borrow());
752
753 for v in iter {
754 result.push(sep.clone());
755 result.extend_from_slice(v.borrow())
756 }
757 result
758 }
759}
760
761#[cfg(not(no_global_oom_handling))]
762#[unstable(feature = "slice_concat_ext", issue = "27747")]
763impl<T: Clone, V: Borrow<[T]>> Join<&[T]> for [V] {
764 type Output = Vec<T>;
765
766 fn join(slice: &Self, sep: &[T]) -> Vec<T> {
767 let mut iter = slice.iter();
768 let first = match iter.next() {
769 Some(first) => first,
770 None => return vec![],
771 };
772 let size =
773 slice.iter().map(|v| v.borrow().len()).sum::<usize>() + sep.len() * (slice.len() - 1);
774 let mut result = Vec::with_capacity(size);
775 result.extend_from_slice(first.borrow());
776
777 for v in iter {
778 result.extend_from_slice(sep);
779 result.extend_from_slice(v.borrow())
780 }
781 result
782 }
783}
784
785////////////////////////////////////////////////////////////////////////////////
786// Standard trait implementations for slices
787////////////////////////////////////////////////////////////////////////////////
788
789#[stable(feature = "rust1", since = "1.0.0")]
790impl<T, A: Allocator> Borrow<[T]> for Vec<T, A> {
791 fn borrow(&self) -> &[T] {
792 &self[..]
793 }
794}
795
796#[stable(feature = "rust1", since = "1.0.0")]
797impl<T, A: Allocator> BorrowMut<[T]> for Vec<T, A> {
798 fn borrow_mut(&mut self) -> &mut [T] {
799 &mut self[..]
800 }
801}
802
803// Specializable trait for implementing ToOwned::clone_into. This is
804// public in the crate and has the Allocator parameter so that
805// vec::clone_from use it too.
806#[cfg(not(no_global_oom_handling))]
807pub(crate) trait SpecCloneIntoVec<T, A: Allocator> {
808 fn clone_into(&self, target: &mut Vec<T, A>);
809}
810
811#[cfg(not(no_global_oom_handling))]
812impl<T: Clone, A: Allocator> SpecCloneIntoVec<T, A> for [T] {
813 default fn clone_into(&self, target: &mut Vec<T, A>) {
814 // drop anything in target that will not be overwritten
815 target.truncate(self.len());
816
817 // target.len <= self.len due to the truncate above, so the
818 // slices here are always in-bounds.
819 let (init, tail) = self.split_at(target.len());
820
821 // reuse the contained values' allocations/resources.
822 target.clone_from_slice(init);
823 target.extend_from_slice(tail);
824 }
825}
826
827#[cfg(not(no_global_oom_handling))]
828impl<T: Copy, A: Allocator> SpecCloneIntoVec<T, A> for [T] {
829 fn clone_into(&self, target: &mut Vec<T, A>) {
830 target.clear();
831 target.extend_from_slice(self);
832 }
833}
834
835#[cfg(not(no_global_oom_handling))]
836#[stable(feature = "rust1", since = "1.0.0")]
837impl<T: Clone> ToOwned for [T] {
838 type Owned = Vec<T>;
839
840 fn to_owned(&self) -> Vec<T> {
841 self.to_vec()
842 }
843
844 fn clone_into(&self, target: &mut Vec<T>) {
845 SpecCloneIntoVec::clone_into(self, target);
846 }
847}
848
849////////////////////////////////////////////////////////////////////////////////
850// Sorting
851////////////////////////////////////////////////////////////////////////////////
852
853#[inline]
854#[cfg(not(no_global_oom_handling))]
855fn stable_sort<T, F>(v: &mut [T], mut is_less: F)
856where
857 F: FnMut(&T, &T) -> bool,
858{
859 sort::stable::sort::<T, F, Vec<T>>(v, &mut is_less);
860}
861
862#[cfg(not(no_global_oom_handling))]
863#[unstable(issue = "none", feature = "std_internals")]
864impl<T> sort::stable::BufGuard<T> for Vec<T> {
865 fn with_capacity(capacity: usize) -> Self {
866 Vec::with_capacity(capacity)
867 }
868
869 fn as_uninit_slice_mut(&mut self) -> &mut [MaybeUninit<T>] {
870 self.spare_capacity_mut()
871 }
872}