1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A contiguous growable array type with heap-allocated contents, written
12 //! `Vec<T>` but pronounced 'vector.'
14 //! Vectors have `O(1)` indexing, amortized `O(1)` push (to the end) and
15 //! `O(1)` pop (from the end).
19 //! You can explicitly create a [`Vec<T>`] with [`new()`]:
22 //! let v: Vec<i32> = Vec::new();
25 //! ...or by using the [`vec!`] macro:
28 //! let v: Vec<i32> = vec![];
30 //! let v = vec![1, 2, 3, 4, 5];
32 //! let v = vec![0; 10]; // ten zeroes
35 //! You can [`push`] values onto the end of a vector (which will grow the vector
39 //! let mut v = vec![1, 2];
44 //! Popping values works in much the same way:
47 //! let mut v = vec![1, 2];
49 //! let two = v.pop();
52 //! Vectors also support indexing (through the [`Index`] and [`IndexMut`] traits):
55 //! let mut v = vec![1, 2, 3];
60 //! [`Vec<T>`]: ../../std/vec/struct.Vec.html
61 //! [`new()`]: ../../std/vec/struct.Vec.html#method.new
62 //! [`push`]: ../../std/vec/struct.Vec.html#method.push
63 //! [`Index`]: ../../std/ops/trait.Index.html
64 //! [`IndexMut`]: ../../std/ops/trait.IndexMut.html
65 //! [`vec!`]: ../../std/macro.vec.html
67 #![stable(feature = "rust1", since = "1.0.0")]
69 use alloc::boxed::Box;
70 use alloc::heap::EMPTY;
71 use alloc::raw_vec::RawVec;
74 use core::cmp::Ordering;
76 use core::hash::{self, Hash};
77 use core::intrinsics::{arith_offset, assume};
78 use core::iter::{FromIterator, FusedIterator, TrustedLen};
80 use core::ops::{InPlace, Index, IndexMut, Place, Placer};
83 use core::ptr::Shared;
86 use super::range::RangeArgument;
87 use Bound::{Excluded, Included, Unbounded};
89 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
94 /// let mut vec = Vec::new();
98 /// assert_eq!(vec.len(), 2);
99 /// assert_eq!(vec[0], 1);
101 /// assert_eq!(vec.pop(), Some(2));
102 /// assert_eq!(vec.len(), 1);
105 /// assert_eq!(vec[0], 7);
107 /// vec.extend([1, 2, 3].iter().cloned());
110 /// println!("{}", x);
112 /// assert_eq!(vec, [7, 1, 2, 3]);
115 /// The [`vec!`] macro is provided to make initialization more convenient:
118 /// let mut vec = vec![1, 2, 3];
120 /// assert_eq!(vec, [1, 2, 3, 4]);
123 /// It can also initialize each element of a `Vec<T>` with a given value:
126 /// let vec = vec![0; 5];
127 /// assert_eq!(vec, [0, 0, 0, 0, 0]);
130 /// Use a `Vec<T>` as an efficient stack:
133 /// let mut stack = Vec::new();
139 /// while let Some(top) = stack.pop() {
140 /// // Prints 3, 2, 1
141 /// println!("{}", top);
147 /// The `Vec` type allows to access values by index, because it implements the
148 /// [`Index`] trait. An example will be more explicit:
151 /// let v = vec![0, 2, 4, 6];
152 /// println!("{}", v[1]); // it will display '2'
155 /// However be careful: if you try to access an index which isn't in the `Vec`,
156 /// your software will panic! You cannot do this:
159 /// let v = vec![0, 2, 4, 6];
160 /// println!("{}", v[6]); // it will panic!
163 /// In conclusion: always check if the index you want to get really exists
168 /// A `Vec` can be mutable. Slices, on the other hand, are read-only objects.
169 /// To get a slice, use `&`. Example:
172 /// fn read_slice(slice: &[usize]) {
176 /// let v = vec![0, 1];
179 /// // ... and that's all!
180 /// // you can also do it like this:
181 /// let x : &[usize] = &v;
184 /// In Rust, it's more common to pass slices as arguments rather than vectors
185 /// when you just want to provide a read access. The same goes for [`String`] and
188 /// # Capacity and reallocation
190 /// The capacity of a vector is the amount of space allocated for any future
191 /// elements that will be added onto the vector. This is not to be confused with
192 /// the *length* of a vector, which specifies the number of actual elements
193 /// within the vector. If a vector's length exceeds its capacity, its capacity
194 /// will automatically be increased, but its elements will have to be
197 /// For example, a vector with capacity 10 and length 0 would be an empty vector
198 /// with space for 10 more elements. Pushing 10 or fewer elements onto the
199 /// vector will not change its capacity or cause reallocation to occur. However,
200 /// if the vector's length is increased to 11, it will have to reallocate, which
201 /// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`]
202 /// whenever possible to specify how big the vector is expected to get.
206 /// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees
207 /// about its design. This ensures that it's as low-overhead as possible in
208 /// the general case, and can be correctly manipulated in primitive ways
209 /// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`.
210 /// If additional type parameters are added (e.g. to support custom allocators),
211 /// overriding their defaults may change the behavior.
213 /// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length)
214 /// triplet. No more, no less. The order of these fields is completely
215 /// unspecified, and you should use the appropriate methods to modify these.
216 /// The pointer will never be null, so this type is null-pointer-optimized.
218 /// However, the pointer may not actually point to allocated memory. In particular,
219 /// if you construct a `Vec` with capacity 0 via [`Vec::new()`], [`vec![]`][`vec!`],
220 /// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit()`]
221 /// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized
222 /// types inside a `Vec`, it will not allocate space for them. *Note that in this case
223 /// the `Vec` may not report a [`capacity()`] of 0*. `Vec` will allocate if and only
224 /// if [`mem::size_of::<T>()`]` * capacity() > 0`. In general, `Vec`'s allocation
225 /// details are subtle enough that it is strongly recommended that you only
226 /// free memory allocated by a `Vec` by creating a new `Vec` and dropping it.
228 /// If a `Vec` *has* allocated memory, then the memory it points to is on the heap
229 /// (as defined by the allocator Rust is configured to use by default), and its
230 /// pointer points to [`len()`] initialized elements in order (what you would see
231 /// if you coerced it to a slice), followed by [`capacity()`]` - `[`len()`]
232 /// logically uninitialized elements.
234 /// `Vec` will never perform a "small optimization" where elements are actually
235 /// stored on the stack for two reasons:
237 /// * It would make it more difficult for unsafe code to correctly manipulate
238 /// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were
239 /// only moved, and it would be more difficult to determine if a `Vec` had
240 /// actually allocated memory.
242 /// * It would penalize the general case, incurring an additional branch
245 /// `Vec` will never automatically shrink itself, even if completely empty. This
246 /// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec`
247 /// and then filling it back up to the same [`len()`] should incur no calls to
248 /// the allocator. If you wish to free up unused memory, use
249 /// [`shrink_to_fit`][`shrink_to_fit()`].
251 /// [`push`] and [`insert`] will never (re)allocate if the reported capacity is
252 /// sufficient. [`push`] and [`insert`] *will* (re)allocate if
253 /// [`len()`]` == `[`capacity()`]. That is, the reported capacity is completely
254 /// accurate, and can be relied on. It can even be used to manually free the memory
255 /// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even
256 /// when not necessary.
258 /// `Vec` does not guarantee any particular growth strategy when reallocating
259 /// when full, nor when [`reserve`] is called. The current strategy is basic
260 /// and it may prove desirable to use a non-constant growth factor. Whatever
261 /// strategy is used will of course guarantee `O(1)` amortized [`push`].
263 /// `vec![x; n]`, `vec![a, b, c, d]`, and
264 /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
265 /// with exactly the requested capacity. If [`len()`]` == `[`capacity()`],
266 /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
267 /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
269 /// `Vec` will not specifically overwrite any data that is removed from it,
270 /// but also won't specifically preserve it. Its uninitialized memory is
271 /// scratch space that it may use however it wants. It will generally just do
272 /// whatever is most efficient or otherwise easy to implement. Do not rely on
273 /// removed data to be erased for security purposes. Even if you drop a `Vec`, its
274 /// buffer may simply be reused by another `Vec`. Even if you zero a `Vec`'s memory
275 /// first, that may not actually happen because the optimizer does not consider
276 /// this a side-effect that must be preserved.
278 /// `Vec` does not currently guarantee the order in which elements are dropped
279 /// (the order has changed in the past, and may change again).
281 /// [`vec!`]: ../../std/macro.vec.html
282 /// [`Index`]: ../../std/ops/trait.Index.html
283 /// [`String`]: ../../std/string/struct.String.html
284 /// [`&str`]: ../../std/primitive.str.html
285 /// [`Vec::with_capacity`]: ../../std/vec/struct.Vec.html#method.with_capacity
286 /// [`Vec::new()`]: ../../std/vec/struct.Vec.html#method.new
287 /// [`shrink_to_fit()`]: ../../std/vec/struct.Vec.html#method.shrink_to_fit
288 /// [`capacity()`]: ../../std/vec/struct.Vec.html#method.capacity
289 /// [`mem::size_of::<T>()`]: ../../std/mem/fn.size_of.html
290 /// [`len()`]: ../../std/vec/struct.Vec.html#method.len
291 /// [`push`]: ../../std/vec/struct.Vec.html#method.push
292 /// [`insert`]: ../../std/vec/struct.Vec.html#method.insert
293 /// [`reserve`]: ../../std/vec/struct.Vec.html#method.reserve
294 /// [owned slice]: ../../std/boxed/struct.Box.html
295 #[stable(feature = "rust1", since = "1.0.0")]
301 ////////////////////////////////////////////////////////////////////////////////
303 ////////////////////////////////////////////////////////////////////////////////
306 /// Constructs a new, empty `Vec<T>`.
308 /// The vector will not allocate until elements are pushed onto it.
313 /// # #![allow(unused_mut)]
314 /// let mut vec: Vec<i32> = Vec::new();
317 #[stable(feature = "rust1", since = "1.0.0")]
318 pub fn new() -> Vec<T> {
325 /// Constructs a new, empty `Vec<T>` with the specified capacity.
327 /// The vector will be able to hold exactly `capacity` elements without
328 /// reallocating. If `capacity` is 0, the vector will not allocate.
330 /// It is important to note that this function does not specify the *length*
331 /// of the returned vector, but only the *capacity*. For an explanation of
332 /// the difference between length and capacity, see *[Capacity and reallocation]*.
334 /// [Capacity and reallocation]: #capacity-and-reallocation
339 /// let mut vec = Vec::with_capacity(10);
341 /// // The vector contains no items, even though it has capacity for more
342 /// assert_eq!(vec.len(), 0);
344 /// // These are all done without reallocating...
349 /// // ...but this may make the vector reallocate
353 #[stable(feature = "rust1", since = "1.0.0")]
354 pub fn with_capacity(capacity: usize) -> Vec<T> {
356 buf: RawVec::with_capacity(capacity),
361 /// Creates a `Vec<T>` directly from the raw components of another vector.
365 /// This is highly unsafe, due to the number of invariants that aren't
368 /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
369 /// (at least, it's highly likely to be incorrect if it wasn't).
370 /// * `length` needs to be less than or equal to `capacity`.
371 /// * `capacity` needs to be the capacity that the pointer was allocated with.
373 /// Violating these may cause problems like corrupting the allocator's
374 /// internal datastructures. For example it is **not** safe
375 /// to build a `Vec<u8>` from a pointer to a C `char` array and a `size_t`.
377 /// The ownership of `ptr` is effectively transferred to the
378 /// `Vec<T>` which may then deallocate, reallocate or change the
379 /// contents of memory pointed to by the pointer at will. Ensure
380 /// that nothing else uses the pointer after calling this
383 /// [`String`]: ../../std/string/struct.String.html
392 /// let mut v = vec![1, 2, 3];
394 /// // Pull out the various important pieces of information about `v`
395 /// let p = v.as_mut_ptr();
396 /// let len = v.len();
397 /// let cap = v.capacity();
400 /// // Cast `v` into the void: no destructor run, so we are in
401 /// // complete control of the allocation to which `p` points.
404 /// // Overwrite memory with 4, 5, 6
405 /// for i in 0..len as isize {
406 /// ptr::write(p.offset(i), 4 + i);
409 /// // Put everything back together into a Vec
410 /// let rebuilt = Vec::from_raw_parts(p, len, cap);
411 /// assert_eq!(rebuilt, [4, 5, 6]);
415 #[stable(feature = "rust1", since = "1.0.0")]
416 pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T> {
418 buf: RawVec::from_raw_parts(ptr, capacity),
423 /// Returns the number of elements the vector can hold without
429 /// let vec: Vec<i32> = Vec::with_capacity(10);
430 /// assert_eq!(vec.capacity(), 10);
433 #[stable(feature = "rust1", since = "1.0.0")]
434 pub fn capacity(&self) -> usize {
438 /// Reserves capacity for at least `additional` more elements to be inserted
439 /// in the given `Vec<T>`. The collection may reserve more space to avoid
440 /// frequent reallocations.
444 /// Panics if the new capacity overflows `usize`.
449 /// let mut vec = vec![1];
451 /// assert!(vec.capacity() >= 11);
453 #[stable(feature = "rust1", since = "1.0.0")]
454 pub fn reserve(&mut self, additional: usize) {
455 self.buf.reserve(self.len, additional);
458 /// Reserves the minimum capacity for exactly `additional` more elements to
459 /// be inserted in the given `Vec<T>`. Does nothing if the capacity is already
462 /// Note that the allocator may give the collection more space than it
463 /// requests. Therefore capacity can not be relied upon to be precisely
464 /// minimal. Prefer `reserve` if future insertions are expected.
468 /// Panics if the new capacity overflows `usize`.
473 /// let mut vec = vec![1];
474 /// vec.reserve_exact(10);
475 /// assert!(vec.capacity() >= 11);
477 #[stable(feature = "rust1", since = "1.0.0")]
478 pub fn reserve_exact(&mut self, additional: usize) {
479 self.buf.reserve_exact(self.len, additional);
482 /// Shrinks the capacity of the vector as much as possible.
484 /// It will drop down as close as possible to the length but the allocator
485 /// may still inform the vector that there is space for a few more elements.
490 /// let mut vec = Vec::with_capacity(10);
491 /// vec.extend([1, 2, 3].iter().cloned());
492 /// assert_eq!(vec.capacity(), 10);
493 /// vec.shrink_to_fit();
494 /// assert!(vec.capacity() >= 3);
496 #[stable(feature = "rust1", since = "1.0.0")]
497 pub fn shrink_to_fit(&mut self) {
498 self.buf.shrink_to_fit(self.len);
501 /// Converts the vector into [`Box<[T]>`][owned slice].
503 /// Note that this will drop any excess capacity. Calling this and
504 /// converting back to a vector with [`into_vec()`] is equivalent to calling
505 /// [`shrink_to_fit()`].
507 /// [owned slice]: ../../std/boxed/struct.Box.html
508 /// [`into_vec()`]: ../../std/primitive.slice.html#method.into_vec
509 /// [`shrink_to_fit()`]: #method.shrink_to_fit
514 /// let v = vec![1, 2, 3];
516 /// let slice = v.into_boxed_slice();
519 /// Any excess capacity is removed:
522 /// let mut vec = Vec::with_capacity(10);
523 /// vec.extend([1, 2, 3].iter().cloned());
525 /// assert_eq!(vec.capacity(), 10);
526 /// let slice = vec.into_boxed_slice();
527 /// assert_eq!(slice.into_vec().capacity(), 3);
529 #[stable(feature = "rust1", since = "1.0.0")]
530 pub fn into_boxed_slice(mut self) -> Box<[T]> {
532 self.shrink_to_fit();
533 let buf = ptr::read(&self.buf);
539 /// Shortens the vector, keeping the first `len` elements and dropping
542 /// If `len` is greater than the vector's current length, this has no
545 /// The [`drain`] method can emulate `truncate`, but causes the excess
546 /// elements to be returned instead of dropped.
550 /// Truncating a five element vector to two elements:
553 /// let mut vec = vec![1, 2, 3, 4, 5];
555 /// assert_eq!(vec, [1, 2]);
558 /// No truncation occurs when `len` is greater than the vector's current
562 /// let mut vec = vec![1, 2, 3];
564 /// assert_eq!(vec, [1, 2, 3]);
567 /// Truncating when `len == 0` is equivalent to calling the [`clear`]
571 /// let mut vec = vec![1, 2, 3];
573 /// assert_eq!(vec, []);
576 /// [`clear`]: #method.clear
577 /// [`drain`]: #method.drain
578 #[stable(feature = "rust1", since = "1.0.0")]
579 pub fn truncate(&mut self, len: usize) {
581 // drop any extra elements
582 while len < self.len {
583 // decrement len before the drop_in_place(), so a panic on Drop
584 // doesn't re-drop the just-failed value.
587 ptr::drop_in_place(self.get_unchecked_mut(len));
592 /// Extracts a slice containing the entire vector.
594 /// Equivalent to `&s[..]`.
599 /// use std::io::{self, Write};
600 /// let buffer = vec![1, 2, 3, 5, 8];
601 /// io::sink().write(buffer.as_slice()).unwrap();
604 #[stable(feature = "vec_as_slice", since = "1.7.0")]
605 pub fn as_slice(&self) -> &[T] {
609 /// Extracts a mutable slice of the entire vector.
611 /// Equivalent to `&mut s[..]`.
616 /// use std::io::{self, Read};
617 /// let mut buffer = vec![0; 3];
618 /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();
621 #[stable(feature = "vec_as_slice", since = "1.7.0")]
622 pub fn as_mut_slice(&mut self) -> &mut [T] {
626 /// Sets the length of a vector.
628 /// This will explicitly set the size of the vector, without actually
629 /// modifying its buffers, so it is up to the caller to ensure that the
630 /// vector is actually the specified size.
637 /// let mut vec = vec!['r', 'u', 's', 't'];
640 /// ptr::drop_in_place(&mut vec[3]);
643 /// assert_eq!(vec, ['r', 'u', 's']);
646 /// In this example, there is a memory leak since the memory locations
647 /// owned by the inner vectors were not freed prior to the `set_len` call:
650 /// let mut vec = vec![vec![1, 0, 0],
658 /// In this example, the vector gets expanded from zero to four items
659 /// without any memory allocations occurring, resulting in vector
660 /// values of unallocated memory:
663 /// let mut vec: Vec<char> = Vec::new();
670 #[stable(feature = "rust1", since = "1.0.0")]
671 pub unsafe fn set_len(&mut self, len: usize) {
675 /// Removes an element from anywhere in the vector and return it, replacing
676 /// it with the last element.
678 /// This does not preserve ordering, but is O(1).
682 /// Panics if `index` is out of bounds.
687 /// let mut v = vec!["foo", "bar", "baz", "qux"];
689 /// assert_eq!(v.swap_remove(1), "bar");
690 /// assert_eq!(v, ["foo", "qux", "baz"]);
692 /// assert_eq!(v.swap_remove(0), "foo");
693 /// assert_eq!(v, ["baz", "qux"]);
696 #[stable(feature = "rust1", since = "1.0.0")]
697 pub fn swap_remove(&mut self, index: usize) -> T {
698 let length = self.len();
699 self.swap(index, length - 1);
703 /// Inserts an element at position `index` within the vector, shifting all
704 /// elements after it to the right.
708 /// Panics if `index` is out of bounds.
713 /// let mut vec = vec![1, 2, 3];
714 /// vec.insert(1, 4);
715 /// assert_eq!(vec, [1, 4, 2, 3]);
716 /// vec.insert(4, 5);
717 /// assert_eq!(vec, [1, 4, 2, 3, 5]);
719 #[stable(feature = "rust1", since = "1.0.0")]
720 pub fn insert(&mut self, index: usize, element: T) {
721 let len = self.len();
722 assert!(index <= len);
724 // space for the new element
725 if len == self.buf.cap() {
731 // The spot to put the new value
733 let p = self.as_mut_ptr().offset(index as isize);
734 // Shift everything over to make space. (Duplicating the
735 // `index`th element into two consecutive places.)
736 ptr::copy(p, p.offset(1), len - index);
737 // Write it in, overwriting the first copy of the `index`th
739 ptr::write(p, element);
741 self.set_len(len + 1);
745 /// Removes and returns the element at position `index` within the vector,
746 /// shifting all elements after it to the left.
750 /// Panics if `index` is out of bounds.
755 /// let mut v = vec![1, 2, 3];
756 /// assert_eq!(v.remove(1), 2);
757 /// assert_eq!(v, [1, 3]);
759 #[stable(feature = "rust1", since = "1.0.0")]
760 pub fn remove(&mut self, index: usize) -> T {
761 let len = self.len();
762 assert!(index < len);
767 // the place we are taking from.
768 let ptr = self.as_mut_ptr().offset(index as isize);
769 // copy it out, unsafely having a copy of the value on
770 // the stack and in the vector at the same time.
771 ret = ptr::read(ptr);
773 // Shift everything down to fill in that spot.
774 ptr::copy(ptr.offset(1), ptr, len - index - 1);
776 self.set_len(len - 1);
781 /// Retains only the elements specified by the predicate.
783 /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
784 /// This method operates in place and preserves the order of the retained
790 /// let mut vec = vec![1, 2, 3, 4];
791 /// vec.retain(|&x| x%2 == 0);
792 /// assert_eq!(vec, [2, 4]);
794 #[stable(feature = "rust1", since = "1.0.0")]
795 pub fn retain<F>(&mut self, mut f: F)
796 where F: FnMut(&T) -> bool
798 let len = self.len();
812 self.truncate(len - del);
816 /// Removes consecutive elements in the vector that resolve to the same key.
818 /// If the vector is sorted, this removes all duplicates.
823 /// let mut vec = vec![10, 20, 21, 30, 20];
825 /// vec.dedup_by_key(|i| *i / 10);
827 /// assert_eq!(vec, [10, 20, 30, 20]);
829 #[stable(feature = "dedup_by", since = "1.16.0")]
831 pub fn dedup_by_key<F, K>(&mut self, mut key: F) where F: FnMut(&mut T) -> K, K: PartialEq {
832 self.dedup_by(|a, b| key(a) == key(b))
835 /// Removes consecutive elements in the vector that resolve to the same key.
837 /// If the vector is sorted, this removes all duplicates.
842 /// use std::ascii::AsciiExt;
844 /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];
846 /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));
848 /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]);
850 #[stable(feature = "dedup_by", since = "1.16.0")]
851 pub fn dedup_by<F>(&mut self, mut same_bucket: F) where F: FnMut(&mut T, &mut T) -> bool {
853 // Although we have a mutable reference to `self`, we cannot make
854 // *arbitrary* changes. The `same_bucket` calls could panic, so we
855 // must ensure that the vector is in a valid state at all time.
857 // The way that we handle this is by using swaps; we iterate
858 // over all the elements, swapping as we go so that at the end
859 // the elements we wish to keep are in the front, and those we
860 // wish to reject are at the back. We can then truncate the
861 // vector. This operation is still O(n).
863 // Example: We start in this state, where `r` represents "next
864 // read" and `w` represents "next_write`.
867 // +---+---+---+---+---+---+
868 // | 0 | 1 | 1 | 2 | 3 | 3 |
869 // +---+---+---+---+---+---+
872 // Comparing self[r] against self[w-1], this is not a duplicate, so
873 // we swap self[r] and self[w] (no effect as r==w) and then increment both
874 // r and w, leaving us with:
877 // +---+---+---+---+---+---+
878 // | 0 | 1 | 1 | 2 | 3 | 3 |
879 // +---+---+---+---+---+---+
882 // Comparing self[r] against self[w-1], this value is a duplicate,
883 // so we increment `r` but leave everything else unchanged:
886 // +---+---+---+---+---+---+
887 // | 0 | 1 | 1 | 2 | 3 | 3 |
888 // +---+---+---+---+---+---+
891 // Comparing self[r] against self[w-1], this is not a duplicate,
892 // so swap self[r] and self[w] and advance r and w:
895 // +---+---+---+---+---+---+
896 // | 0 | 1 | 2 | 1 | 3 | 3 |
897 // +---+---+---+---+---+---+
900 // Not a duplicate, repeat:
903 // +---+---+---+---+---+---+
904 // | 0 | 1 | 2 | 3 | 1 | 3 |
905 // +---+---+---+---+---+---+
908 // Duplicate, advance r. End of vec. Truncate to w.
915 // Avoid bounds checks by using raw pointers.
916 let p = self.as_mut_ptr();
917 let mut r: usize = 1;
918 let mut w: usize = 1;
921 let p_r = p.offset(r as isize);
922 let p_wm1 = p.offset((w - 1) as isize);
923 if !same_bucket(&mut *p_r, &mut *p_wm1) {
925 let p_w = p_wm1.offset(1);
926 mem::swap(&mut *p_r, &mut *p_w);
937 /// Appends an element to the back of a collection.
941 /// Panics if the number of elements in the vector overflows a `usize`.
946 /// let mut vec = vec![1, 2];
948 /// assert_eq!(vec, [1, 2, 3]);
951 #[stable(feature = "rust1", since = "1.0.0")]
952 pub fn push(&mut self, value: T) {
953 // This will panic or abort if we would allocate > isize::MAX bytes
954 // or if the length increment would overflow for zero-sized types.
955 if self.len == self.buf.cap() {
959 let end = self.as_mut_ptr().offset(self.len as isize);
960 ptr::write(end, value);
965 /// Removes the last element from a vector and returns it, or [`None`] if it
968 /// [`None`]: ../../std/option/enum.Option.html#variant.None
973 /// let mut vec = vec![1, 2, 3];
974 /// assert_eq!(vec.pop(), Some(3));
975 /// assert_eq!(vec, [1, 2]);
978 #[stable(feature = "rust1", since = "1.0.0")]
979 pub fn pop(&mut self) -> Option<T> {
985 Some(ptr::read(self.get_unchecked(self.len())))
990 /// Moves all the elements of `other` into `Self`, leaving `other` empty.
994 /// Panics if the number of elements in the vector overflows a `usize`.
999 /// let mut vec = vec![1, 2, 3];
1000 /// let mut vec2 = vec![4, 5, 6];
1001 /// vec.append(&mut vec2);
1002 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
1003 /// assert_eq!(vec2, []);
1006 #[stable(feature = "append", since = "1.4.0")]
1007 pub fn append(&mut self, other: &mut Self) {
1008 self.reserve(other.len());
1009 let len = self.len();
1011 ptr::copy_nonoverlapping(other.as_ptr(), self.get_unchecked_mut(len), other.len());
1014 self.len += other.len();
1020 /// Create a draining iterator that removes the specified range in the vector
1021 /// and yields the removed items.
1023 /// Note 1: The element range is removed even if the iterator is only
1024 /// partially consumed or not consumed at all.
1026 /// Note 2: It is unspecified how many elements are removed from the vector,
1027 /// if the `Drain` value is leaked.
1031 /// Panics if the starting point is greater than the end point or if
1032 /// the end point is greater than the length of the vector.
1037 /// let mut v = vec![1, 2, 3];
1038 /// let u: Vec<_> = v.drain(1..).collect();
1039 /// assert_eq!(v, &[1]);
1040 /// assert_eq!(u, &[2, 3]);
1042 /// // A full range clears the vector
1044 /// assert_eq!(v, &[]);
1046 #[stable(feature = "drain", since = "1.6.0")]
1047 pub fn drain<R>(&mut self, range: R) -> Drain<T>
1048 where R: RangeArgument<usize>
1052 // When the Drain is first created, it shortens the length of
1053 // the source vector to make sure no uninitalized or moved-from elements
1054 // are accessible at all if the Drain's destructor never gets to run.
1056 // Drain will ptr::read out the values to remove.
1057 // When finished, remaining tail of the vec is copied back to cover
1058 // the hole, and the vector length is restored to the new length.
1060 let len = self.len();
1061 let start = match range.start() {
1063 Excluded(&n) => n + 1,
1066 let end = match range.end() {
1067 Included(&n) => n + 1,
1071 assert!(start <= end);
1072 assert!(end <= len);
1075 // set self.vec length's to start, to be safe in case Drain is leaked
1076 self.set_len(start);
1077 // Use the borrow in the IterMut to indicate borrowing behavior of the
1078 // whole Drain iterator (like &mut T).
1079 let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().offset(start as isize),
1083 tail_len: len - end,
1084 iter: range_slice.iter(),
1085 vec: Shared::new(self as *mut _),
1090 /// Clears the vector, removing all values.
1095 /// let mut v = vec![1, 2, 3];
1099 /// assert!(v.is_empty());
1102 #[stable(feature = "rust1", since = "1.0.0")]
1103 pub fn clear(&mut self) {
1107 /// Returns the number of elements in the vector.
1112 /// let a = vec![1, 2, 3];
1113 /// assert_eq!(a.len(), 3);
1116 #[stable(feature = "rust1", since = "1.0.0")]
1117 pub fn len(&self) -> usize {
1121 /// Returns `true` if the vector contains no elements.
1126 /// let mut v = Vec::new();
1127 /// assert!(v.is_empty());
1130 /// assert!(!v.is_empty());
1132 #[stable(feature = "rust1", since = "1.0.0")]
1133 pub fn is_empty(&self) -> bool {
1137 /// Splits the collection into two at the given index.
1139 /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`,
1140 /// and the returned `Self` contains elements `[at, len)`.
1142 /// Note that the capacity of `self` does not change.
1146 /// Panics if `at > len`.
1151 /// let mut vec = vec![1,2,3];
1152 /// let vec2 = vec.split_off(1);
1153 /// assert_eq!(vec, [1]);
1154 /// assert_eq!(vec2, [2, 3]);
1157 #[stable(feature = "split_off", since = "1.4.0")]
1158 pub fn split_off(&mut self, at: usize) -> Self {
1159 assert!(at <= self.len(), "`at` out of bounds");
1161 let other_len = self.len - at;
1162 let mut other = Vec::with_capacity(other_len);
1164 // Unsafely `set_len` and copy items to `other`.
1167 other.set_len(other_len);
1169 ptr::copy_nonoverlapping(self.as_ptr().offset(at as isize),
1177 impl<T: Clone> Vec<T> {
1178 /// Resizes the `Vec` in-place so that `len()` is equal to `new_len`.
1180 /// If `new_len` is greater than `len()`, the `Vec` is extended by the
1181 /// difference, with each additional slot filled with `value`.
1182 /// If `new_len` is less than `len()`, the `Vec` is simply truncated.
1187 /// let mut vec = vec!["hello"];
1188 /// vec.resize(3, "world");
1189 /// assert_eq!(vec, ["hello", "world", "world"]);
1191 /// let mut vec = vec![1, 2, 3, 4];
1192 /// vec.resize(2, 0);
1193 /// assert_eq!(vec, [1, 2]);
1195 #[stable(feature = "vec_resize", since = "1.5.0")]
1196 pub fn resize(&mut self, new_len: usize, value: T) {
1197 let len = self.len();
1200 self.extend_with_element(new_len - len, value);
1202 self.truncate(new_len);
1206 /// Extend the vector by `n` additional clones of `value`.
1207 fn extend_with_element(&mut self, n: usize, value: T) {
1211 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1212 // Use SetLenOnDrop to work around bug where compiler
1213 // may not realize the store through `ptr` trough self.set_len()
1215 let mut local_len = SetLenOnDrop::new(&mut self.len);
1217 // Write all elements except the last one
1219 ptr::write(ptr, value.clone());
1220 ptr = ptr.offset(1);
1221 // Increment the length in every step in case clone() panics
1222 local_len.increment_len(1);
1226 // We can write the last element directly without cloning needlessly
1227 ptr::write(ptr, value);
1228 local_len.increment_len(1);
1231 // len set by scope guard
1235 /// Clones and appends all elements in a slice to the `Vec`.
1237 /// Iterates over the slice `other`, clones each element, and then appends
1238 /// it to this `Vec`. The `other` vector is traversed in-order.
1240 /// Note that this function is same as `extend` except that it is
1241 /// specialized to work with slices instead. If and when Rust gets
1242 /// specialization this function will likely be deprecated (but still
1248 /// let mut vec = vec![1];
1249 /// vec.extend_from_slice(&[2, 3, 4]);
1250 /// assert_eq!(vec, [1, 2, 3, 4]);
1252 #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
1253 pub fn extend_from_slice(&mut self, other: &[T]) {
1254 self.spec_extend(other.iter())
1257 /// Returns a place for insertion at the back of the `Vec`.
1259 /// Using this method with placement syntax is equivalent to [`push`](#method.push),
1260 /// but may be more efficient.
1265 /// #![feature(collection_placement)]
1266 /// #![feature(placement_in_syntax)]
1268 /// let mut vec = vec![1, 2];
1269 /// vec.place_back() <- 3;
1270 /// vec.place_back() <- 4;
1271 /// assert_eq!(&vec, &[1, 2, 3, 4]);
1273 #[unstable(feature = "collection_placement",
1274 reason = "placement protocol is subject to change",
1276 pub fn place_back(&mut self) -> PlaceBack<T> {
1277 PlaceBack { vec: self }
1281 // Set the length of the vec when the `SetLenOnDrop` value goes out of scope.
1283 // The idea is: The length field in SetLenOnDrop is a local variable
1284 // that the optimizer will see does not alias with any stores through the Vec's data
1285 // pointer. This is a workaround for alias analysis issue #32155
1286 struct SetLenOnDrop<'a> {
1291 impl<'a> SetLenOnDrop<'a> {
1293 fn new(len: &'a mut usize) -> Self {
1294 SetLenOnDrop { local_len: *len, len: len }
1298 fn increment_len(&mut self, increment: usize) {
1299 self.local_len += increment;
1303 impl<'a> Drop for SetLenOnDrop<'a> {
1305 fn drop(&mut self) {
1306 *self.len = self.local_len;
1310 impl<T: PartialEq> Vec<T> {
1311 /// Removes consecutive repeated elements in the vector.
1313 /// If the vector is sorted, this removes all duplicates.
1318 /// let mut vec = vec![1, 2, 2, 3, 2];
1322 /// assert_eq!(vec, [1, 2, 3, 2]);
1324 #[stable(feature = "rust1", since = "1.0.0")]
1326 pub fn dedup(&mut self) {
1327 self.dedup_by(|a, b| a == b)
1331 ////////////////////////////////////////////////////////////////////////////////
1332 // Internal methods and functions
1333 ////////////////////////////////////////////////////////////////////////////////
1336 #[stable(feature = "rust1", since = "1.0.0")]
1337 pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
1338 let mut v = Vec::with_capacity(n);
1339 v.extend_with_element(n, elem);
1343 ////////////////////////////////////////////////////////////////////////////////
1344 // Common trait implementations for Vec
1345 ////////////////////////////////////////////////////////////////////////////////
1347 #[stable(feature = "rust1", since = "1.0.0")]
1348 impl<T: Clone> Clone for Vec<T> {
1350 fn clone(&self) -> Vec<T> {
1351 <[T]>::to_vec(&**self)
1354 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
1355 // required for this method definition, is not available. Instead use the
1356 // `slice::to_vec` function which is only available with cfg(test)
1357 // NB see the slice::hack module in slice.rs for more information
1359 fn clone(&self) -> Vec<T> {
1360 ::slice::to_vec(&**self)
1363 fn clone_from(&mut self, other: &Vec<T>) {
1364 // drop anything in self that will not be overwritten
1365 self.truncate(other.len());
1366 let len = self.len();
1368 // reuse the contained values' allocations/resources.
1369 self.clone_from_slice(&other[..len]);
1371 // self.len <= other.len due to the truncate above, so the
1372 // slice here is always in-bounds.
1373 self.extend_from_slice(&other[len..]);
1377 #[stable(feature = "rust1", since = "1.0.0")]
1378 impl<T: Hash> Hash for Vec<T> {
1380 fn hash<H: hash::Hasher>(&self, state: &mut H) {
1381 Hash::hash(&**self, state)
1385 #[stable(feature = "rust1", since = "1.0.0")]
1386 impl<T> Index<usize> for Vec<T> {
1390 fn index(&self, index: usize) -> &T {
1391 // NB built-in indexing via `&[T]`
1396 #[stable(feature = "rust1", since = "1.0.0")]
1397 impl<T> IndexMut<usize> for Vec<T> {
1399 fn index_mut(&mut self, index: usize) -> &mut T {
1400 // NB built-in indexing via `&mut [T]`
1401 &mut (**self)[index]
1406 #[stable(feature = "rust1", since = "1.0.0")]
1407 impl<T> ops::Index<ops::Range<usize>> for Vec<T> {
1411 fn index(&self, index: ops::Range<usize>) -> &[T] {
1412 Index::index(&**self, index)
1415 #[stable(feature = "rust1", since = "1.0.0")]
1416 impl<T> ops::Index<ops::RangeTo<usize>> for Vec<T> {
1420 fn index(&self, index: ops::RangeTo<usize>) -> &[T] {
1421 Index::index(&**self, index)
1424 #[stable(feature = "rust1", since = "1.0.0")]
1425 impl<T> ops::Index<ops::RangeFrom<usize>> for Vec<T> {
1429 fn index(&self, index: ops::RangeFrom<usize>) -> &[T] {
1430 Index::index(&**self, index)
1433 #[stable(feature = "rust1", since = "1.0.0")]
1434 impl<T> ops::Index<ops::RangeFull> for Vec<T> {
1438 fn index(&self, _index: ops::RangeFull) -> &[T] {
1442 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1443 impl<T> ops::Index<ops::RangeInclusive<usize>> for Vec<T> {
1447 fn index(&self, index: ops::RangeInclusive<usize>) -> &[T] {
1448 Index::index(&**self, index)
1451 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1452 impl<T> ops::Index<ops::RangeToInclusive<usize>> for Vec<T> {
1456 fn index(&self, index: ops::RangeToInclusive<usize>) -> &[T] {
1457 Index::index(&**self, index)
1461 #[stable(feature = "rust1", since = "1.0.0")]
1462 impl<T> ops::IndexMut<ops::Range<usize>> for Vec<T> {
1464 fn index_mut(&mut self, index: ops::Range<usize>) -> &mut [T] {
1465 IndexMut::index_mut(&mut **self, index)
1468 #[stable(feature = "rust1", since = "1.0.0")]
1469 impl<T> ops::IndexMut<ops::RangeTo<usize>> for Vec<T> {
1471 fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut [T] {
1472 IndexMut::index_mut(&mut **self, index)
1475 #[stable(feature = "rust1", since = "1.0.0")]
1476 impl<T> ops::IndexMut<ops::RangeFrom<usize>> for Vec<T> {
1478 fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut [T] {
1479 IndexMut::index_mut(&mut **self, index)
1482 #[stable(feature = "rust1", since = "1.0.0")]
1483 impl<T> ops::IndexMut<ops::RangeFull> for Vec<T> {
1485 fn index_mut(&mut self, _index: ops::RangeFull) -> &mut [T] {
1489 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1490 impl<T> ops::IndexMut<ops::RangeInclusive<usize>> for Vec<T> {
1492 fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut [T] {
1493 IndexMut::index_mut(&mut **self, index)
1496 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1497 impl<T> ops::IndexMut<ops::RangeToInclusive<usize>> for Vec<T> {
1499 fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut [T] {
1500 IndexMut::index_mut(&mut **self, index)
1504 #[stable(feature = "rust1", since = "1.0.0")]
1505 impl<T> ops::Deref for Vec<T> {
1508 fn deref(&self) -> &[T] {
1510 let p = self.buf.ptr();
1511 assume(!p.is_null());
1512 slice::from_raw_parts(p, self.len)
1517 #[stable(feature = "rust1", since = "1.0.0")]
1518 impl<T> ops::DerefMut for Vec<T> {
1519 fn deref_mut(&mut self) -> &mut [T] {
1521 let ptr = self.buf.ptr();
1522 assume(!ptr.is_null());
1523 slice::from_raw_parts_mut(ptr, self.len)
1528 #[stable(feature = "rust1", since = "1.0.0")]
1529 impl<T> FromIterator<T> for Vec<T> {
1531 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> {
1532 <Self as SpecExtend<_, _>>::from_iter(iter.into_iter())
1536 #[stable(feature = "rust1", since = "1.0.0")]
1537 impl<T> IntoIterator for Vec<T> {
1539 type IntoIter = IntoIter<T>;
1541 /// Creates a consuming iterator, that is, one that moves each value out of
1542 /// the vector (from start to end). The vector cannot be used after calling
1548 /// let v = vec!["a".to_string(), "b".to_string()];
1549 /// for s in v.into_iter() {
1550 /// // s has type String, not &String
1551 /// println!("{}", s);
1555 fn into_iter(mut self) -> IntoIter<T> {
1557 let begin = self.as_mut_ptr();
1558 assume(!begin.is_null());
1559 let end = if mem::size_of::<T>() == 0 {
1560 arith_offset(begin as *const i8, self.len() as isize) as *const T
1562 begin.offset(self.len() as isize) as *const T
1564 let cap = self.buf.cap();
1567 buf: Shared::new(begin),
1576 #[stable(feature = "rust1", since = "1.0.0")]
1577 impl<'a, T> IntoIterator for &'a Vec<T> {
1579 type IntoIter = slice::Iter<'a, T>;
1581 fn into_iter(self) -> slice::Iter<'a, T> {
1586 #[stable(feature = "rust1", since = "1.0.0")]
1587 impl<'a, T> IntoIterator for &'a mut Vec<T> {
1588 type Item = &'a mut T;
1589 type IntoIter = slice::IterMut<'a, T>;
1591 fn into_iter(mut self) -> slice::IterMut<'a, T> {
1596 #[stable(feature = "rust1", since = "1.0.0")]
1597 impl<T> Extend<T> for Vec<T> {
1599 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1600 self.spec_extend(iter.into_iter())
1604 // Specialization trait used for Vec::from_iter and Vec::extend
1605 trait SpecExtend<T, I> {
1606 fn from_iter(iter: I) -> Self;
1607 fn spec_extend(&mut self, iter: I);
1610 impl<T, I> SpecExtend<T, I> for Vec<T>
1611 where I: Iterator<Item=T>,
1613 default fn from_iter(mut iterator: I) -> Self {
1614 // Unroll the first iteration, as the vector is going to be
1615 // expanded on this iteration in every case when the iterable is not
1616 // empty, but the loop in extend_desugared() is not going to see the
1617 // vector being full in the few subsequent loop iterations.
1618 // So we get better branch prediction.
1619 let mut vector = match iterator.next() {
1620 None => return Vec::new(),
1622 let (lower, _) = iterator.size_hint();
1623 let mut vector = Vec::with_capacity(lower.saturating_add(1));
1625 ptr::write(vector.get_unchecked_mut(0), element);
1631 vector.spec_extend(iterator);
1635 default fn spec_extend(&mut self, iter: I) {
1636 self.extend_desugared(iter)
1640 impl<T, I> SpecExtend<T, I> for Vec<T>
1641 where I: TrustedLen<Item=T>,
1643 fn from_iter(iterator: I) -> Self {
1644 let mut vector = Vec::new();
1645 vector.spec_extend(iterator);
1649 fn spec_extend(&mut self, iterator: I) {
1650 // This is the case for a TrustedLen iterator.
1651 let (low, high) = iterator.size_hint();
1652 if let Some(high_value) = high {
1653 debug_assert_eq!(low, high_value,
1654 "TrustedLen iterator's size hint is not exact: {:?}",
1657 if let Some(additional) = high {
1658 self.reserve(additional);
1660 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1661 let mut local_len = SetLenOnDrop::new(&mut self.len);
1662 for element in iterator {
1663 ptr::write(ptr, element);
1664 ptr = ptr.offset(1);
1665 // NB can't overflow since we would have had to alloc the address space
1666 local_len.increment_len(1);
1670 self.extend_desugared(iterator)
1675 impl<'a, T: 'a, I> SpecExtend<&'a T, I> for Vec<T>
1676 where I: Iterator<Item=&'a T>,
1679 default fn from_iter(iterator: I) -> Self {
1680 SpecExtend::from_iter(iterator.cloned())
1683 default fn spec_extend(&mut self, iterator: I) {
1684 self.spec_extend(iterator.cloned())
1688 impl<'a, T: 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T>
1691 fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
1692 let slice = iterator.as_slice();
1693 self.reserve(slice.len());
1695 let len = self.len();
1696 self.set_len(len + slice.len());
1697 self.get_unchecked_mut(len..).copy_from_slice(slice);
1703 fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
1704 // This is the case for a general iterator.
1706 // This function should be the moral equivalent of:
1708 // for item in iterator {
1711 while let Some(element) = iterator.next() {
1712 let len = self.len();
1713 if len == self.capacity() {
1714 let (lower, _) = iterator.size_hint();
1715 self.reserve(lower.saturating_add(1));
1718 ptr::write(self.get_unchecked_mut(len), element);
1719 // NB can't overflow since we would have had to alloc the address space
1720 self.set_len(len + 1);
1726 #[stable(feature = "extend_ref", since = "1.2.0")]
1727 impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> {
1728 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
1729 self.spec_extend(iter.into_iter())
1733 macro_rules! __impl_slice_eq1 {
1734 ($Lhs: ty, $Rhs: ty) => {
1735 __impl_slice_eq1! { $Lhs, $Rhs, Sized }
1737 ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
1738 #[stable(feature = "rust1", since = "1.0.0")]
1739 impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
1741 fn eq(&self, other: &$Rhs) -> bool { self[..] == other[..] }
1743 fn ne(&self, other: &$Rhs) -> bool { self[..] != other[..] }
1748 __impl_slice_eq1! { Vec<A>, Vec<B> }
1749 __impl_slice_eq1! { Vec<A>, &'b [B] }
1750 __impl_slice_eq1! { Vec<A>, &'b mut [B] }
1751 __impl_slice_eq1! { Cow<'a, [A]>, &'b [B], Clone }
1752 __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B], Clone }
1753 __impl_slice_eq1! { Cow<'a, [A]>, Vec<B>, Clone }
1755 macro_rules! array_impls {
1758 // NOTE: some less important impls are omitted to reduce code bloat
1759 __impl_slice_eq1! { Vec<A>, [B; $N] }
1760 __impl_slice_eq1! { Vec<A>, &'b [B; $N] }
1761 // __impl_slice_eq1! { Vec<A>, &'b mut [B; $N] }
1762 // __impl_slice_eq1! { Cow<'a, [A]>, [B; $N], Clone }
1763 // __impl_slice_eq1! { Cow<'a, [A]>, &'b [B; $N], Clone }
1764 // __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
1771 10 11 12 13 14 15 16 17 18 19
1772 20 21 22 23 24 25 26 27 28 29
1776 #[stable(feature = "rust1", since = "1.0.0")]
1777 impl<T: PartialOrd> PartialOrd for Vec<T> {
1779 fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> {
1780 PartialOrd::partial_cmp(&**self, &**other)
1784 #[stable(feature = "rust1", since = "1.0.0")]
1785 impl<T: Eq> Eq for Vec<T> {}
1787 #[stable(feature = "rust1", since = "1.0.0")]
1788 impl<T: Ord> Ord for Vec<T> {
1790 fn cmp(&self, other: &Vec<T>) -> Ordering {
1791 Ord::cmp(&**self, &**other)
1795 #[stable(feature = "rust1", since = "1.0.0")]
1796 unsafe impl<#[may_dangle] T> Drop for Vec<T> {
1797 fn drop(&mut self) {
1800 ptr::drop_in_place(&mut self[..]);
1802 // RawVec handles deallocation
1806 #[stable(feature = "rust1", since = "1.0.0")]
1807 impl<T> Default for Vec<T> {
1808 /// Creates an empty `Vec<T>`.
1809 fn default() -> Vec<T> {
1814 #[stable(feature = "rust1", since = "1.0.0")]
1815 impl<T: fmt::Debug> fmt::Debug for Vec<T> {
1816 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1817 fmt::Debug::fmt(&**self, f)
1821 #[stable(feature = "rust1", since = "1.0.0")]
1822 impl<T> AsRef<Vec<T>> for Vec<T> {
1823 fn as_ref(&self) -> &Vec<T> {
1828 #[stable(feature = "vec_as_mut", since = "1.5.0")]
1829 impl<T> AsMut<Vec<T>> for Vec<T> {
1830 fn as_mut(&mut self) -> &mut Vec<T> {
1835 #[stable(feature = "rust1", since = "1.0.0")]
1836 impl<T> AsRef<[T]> for Vec<T> {
1837 fn as_ref(&self) -> &[T] {
1842 #[stable(feature = "vec_as_mut", since = "1.5.0")]
1843 impl<T> AsMut<[T]> for Vec<T> {
1844 fn as_mut(&mut self) -> &mut [T] {
1849 #[stable(feature = "rust1", since = "1.0.0")]
1850 impl<'a, T: Clone> From<&'a [T]> for Vec<T> {
1852 fn from(s: &'a [T]) -> Vec<T> {
1856 fn from(s: &'a [T]) -> Vec<T> {
1861 #[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
1862 impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where [T]: ToOwned<Owned=Vec<T>> {
1863 fn from(s: Cow<'a, [T]>) -> Vec<T> {
1868 #[stable(feature = "rust1", since = "1.0.0")]
1869 impl<'a> From<&'a str> for Vec<u8> {
1870 fn from(s: &'a str) -> Vec<u8> {
1871 From::from(s.as_bytes())
1875 ////////////////////////////////////////////////////////////////////////////////
1877 ////////////////////////////////////////////////////////////////////////////////
1879 #[stable(feature = "cow_from_vec", since = "1.7.0")]
1880 impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> {
1881 fn from(s: &'a [T]) -> Cow<'a, [T]> {
1886 #[stable(feature = "cow_from_vec", since = "1.7.0")]
1887 impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> {
1888 fn from(v: Vec<T>) -> Cow<'a, [T]> {
1893 #[stable(feature = "rust1", since = "1.0.0")]
1894 impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone {
1895 fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {
1896 Cow::Owned(FromIterator::from_iter(it))
1900 ////////////////////////////////////////////////////////////////////////////////
1902 ////////////////////////////////////////////////////////////////////////////////
1904 /// An iterator that moves out of a vector.
1906 /// This `struct` is created by the `into_iter` method on [`Vec`][`Vec`] (provided
1907 /// by the [`IntoIterator`] trait).
1909 /// [`Vec`]: struct.Vec.html
1910 /// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html
1911 #[stable(feature = "rust1", since = "1.0.0")]
1912 pub struct IntoIter<T> {
1919 #[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
1920 impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
1921 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1922 f.debug_tuple("IntoIter")
1923 .field(&self.as_slice())
1928 impl<T> IntoIter<T> {
1929 /// Returns the remaining items of this iterator as a slice.
1934 /// let vec = vec!['a', 'b', 'c'];
1935 /// let mut into_iter = vec.into_iter();
1936 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
1937 /// let _ = into_iter.next().unwrap();
1938 /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
1940 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
1941 pub fn as_slice(&self) -> &[T] {
1943 slice::from_raw_parts(self.ptr, self.len())
1947 /// Returns the remaining items of this iterator as a mutable slice.
1952 /// let vec = vec!['a', 'b', 'c'];
1953 /// let mut into_iter = vec.into_iter();
1954 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
1955 /// into_iter.as_mut_slice()[2] = 'z';
1956 /// assert_eq!(into_iter.next().unwrap(), 'a');
1957 /// assert_eq!(into_iter.next().unwrap(), 'b');
1958 /// assert_eq!(into_iter.next().unwrap(), 'z');
1960 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
1961 pub fn as_mut_slice(&mut self) -> &mut [T] {
1963 slice::from_raw_parts_mut(self.ptr as *mut T, self.len())
1968 #[stable(feature = "rust1", since = "1.0.0")]
1969 unsafe impl<T: Send> Send for IntoIter<T> {}
1970 #[stable(feature = "rust1", since = "1.0.0")]
1971 unsafe impl<T: Sync> Sync for IntoIter<T> {}
1973 #[stable(feature = "rust1", since = "1.0.0")]
1974 impl<T> Iterator for IntoIter<T> {
1978 fn next(&mut self) -> Option<T> {
1980 if self.ptr as *const _ == self.end {
1983 if mem::size_of::<T>() == 0 {
1984 // purposefully don't use 'ptr.offset' because for
1985 // vectors with 0-size elements this would return the
1987 self.ptr = arith_offset(self.ptr as *const i8, 1) as *mut T;
1989 // Use a non-null pointer value
1990 Some(ptr::read(EMPTY as *mut T))
1993 self.ptr = self.ptr.offset(1);
1995 Some(ptr::read(old))
2002 fn size_hint(&self) -> (usize, Option<usize>) {
2003 let diff = (self.end as usize) - (self.ptr as usize);
2004 let size = mem::size_of::<T>();
2011 (exact, Some(exact))
2015 fn count(self) -> usize {
2020 #[stable(feature = "rust1", since = "1.0.0")]
2021 impl<T> DoubleEndedIterator for IntoIter<T> {
2023 fn next_back(&mut self) -> Option<T> {
2025 if self.end == self.ptr {
2028 if mem::size_of::<T>() == 0 {
2029 // See above for why 'ptr.offset' isn't used
2030 self.end = arith_offset(self.end as *const i8, -1) as *mut T;
2032 // Use a non-null pointer value
2033 Some(ptr::read(EMPTY as *mut T))
2035 self.end = self.end.offset(-1);
2037 Some(ptr::read(self.end))
2044 #[stable(feature = "rust1", since = "1.0.0")]
2045 impl<T> ExactSizeIterator for IntoIter<T> {
2046 fn is_empty(&self) -> bool {
2047 self.ptr == self.end
2051 #[unstable(feature = "fused", issue = "35602")]
2052 impl<T> FusedIterator for IntoIter<T> {}
2054 #[unstable(feature = "trusted_len", issue = "37572")]
2055 unsafe impl<T> TrustedLen for IntoIter<T> {}
2057 #[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
2058 impl<T: Clone> Clone for IntoIter<T> {
2059 fn clone(&self) -> IntoIter<T> {
2060 self.as_slice().to_owned().into_iter()
2064 #[stable(feature = "rust1", since = "1.0.0")]
2065 unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
2066 fn drop(&mut self) {
2067 // destroy the remaining elements
2068 for _x in self.by_ref() {}
2070 // RawVec handles deallocation
2071 let _ = unsafe { RawVec::from_raw_parts(*self.buf, self.cap) };
2075 /// A draining iterator for `Vec<T>`.
2077 /// This `struct` is created by the [`drain`] method on [`Vec`].
2079 /// [`drain`]: struct.Vec.html#method.drain
2080 /// [`Vec`]: struct.Vec.html
2081 #[stable(feature = "drain", since = "1.6.0")]
2082 pub struct Drain<'a, T: 'a> {
2083 /// Index of tail to preserve
2087 /// Current remaining range to remove
2088 iter: slice::Iter<'a, T>,
2089 vec: Shared<Vec<T>>,
2092 #[stable(feature = "collection_debug", since = "1.17.0")]
2093 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
2094 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2095 f.debug_tuple("Drain")
2096 .field(&self.iter.as_slice())
2101 #[stable(feature = "drain", since = "1.6.0")]
2102 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
2103 #[stable(feature = "drain", since = "1.6.0")]
2104 unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
2106 #[stable(feature = "drain", since = "1.6.0")]
2107 impl<'a, T> Iterator for Drain<'a, T> {
2111 fn next(&mut self) -> Option<T> {
2112 self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
2115 fn size_hint(&self) -> (usize, Option<usize>) {
2116 self.iter.size_hint()
2120 #[stable(feature = "drain", since = "1.6.0")]
2121 impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
2123 fn next_back(&mut self) -> Option<T> {
2124 self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
2128 #[stable(feature = "drain", since = "1.6.0")]
2129 impl<'a, T> Drop for Drain<'a, T> {
2130 fn drop(&mut self) {
2131 // exhaust self first
2132 while let Some(_) = self.next() {}
2134 if self.tail_len > 0 {
2136 let source_vec = &mut **self.vec;
2137 // memmove back untouched tail, update to new length
2138 let start = source_vec.len();
2139 let tail = self.tail_start;
2140 let src = source_vec.as_ptr().offset(tail as isize);
2141 let dst = source_vec.as_mut_ptr().offset(start as isize);
2142 ptr::copy(src, dst, self.tail_len);
2143 source_vec.set_len(start + self.tail_len);
2150 #[stable(feature = "drain", since = "1.6.0")]
2151 impl<'a, T> ExactSizeIterator for Drain<'a, T> {
2152 fn is_empty(&self) -> bool {
2153 self.iter.is_empty()
2157 #[unstable(feature = "fused", issue = "35602")]
2158 impl<'a, T> FusedIterator for Drain<'a, T> {}
2160 /// A place for insertion at the back of a `Vec`.
2162 /// See [`Vec::place_back`](struct.Vec.html#method.place_back) for details.
2163 #[must_use = "places do nothing unless written to with `<-` syntax"]
2164 #[unstable(feature = "collection_placement",
2165 reason = "struct name and placement protocol are subject to change",
2168 pub struct PlaceBack<'a, T: 'a> {
2169 vec: &'a mut Vec<T>,
2172 #[unstable(feature = "collection_placement",
2173 reason = "placement protocol is subject to change",
2175 impl<'a, T> Placer<T> for PlaceBack<'a, T> {
2176 type Place = PlaceBack<'a, T>;
2178 fn make_place(self) -> Self {
2179 // This will panic or abort if we would allocate > isize::MAX bytes
2180 // or if the length increment would overflow for zero-sized types.
2181 if self.vec.len == self.vec.buf.cap() {
2182 self.vec.buf.double();
2188 #[unstable(feature = "collection_placement",
2189 reason = "placement protocol is subject to change",
2191 impl<'a, T> Place<T> for PlaceBack<'a, T> {
2192 fn pointer(&mut self) -> *mut T {
2193 unsafe { self.vec.as_mut_ptr().offset(self.vec.len as isize) }
2197 #[unstable(feature = "collection_placement",
2198 reason = "placement protocol is subject to change",
2200 impl<'a, T> InPlace<T> for PlaceBack<'a, T> {
2201 type Owner = &'a mut T;
2203 unsafe fn finalize(mut self) -> &'a mut T {
2204 let ptr = self.pointer();