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. After calling `reserve`, capacity will be
441 /// greater than or equal to `self.len() + additional`. Does nothing if
442 /// capacity is already sufficient.
446 /// Panics if the new capacity overflows `usize`.
451 /// let mut vec = vec![1];
453 /// assert!(vec.capacity() >= 11);
455 #[stable(feature = "rust1", since = "1.0.0")]
456 pub fn reserve(&mut self, additional: usize) {
457 self.buf.reserve(self.len, additional);
460 /// Reserves the minimum capacity for exactly `additional` more elements to
461 /// be inserted in the given `Vec<T>`. After calling `reserve_exact`,
462 /// capacity will be greater than or equal to `self.len() + additional`.
463 /// Does nothing if the capacity is already sufficient.
465 /// Note that the allocator may give the collection more space than it
466 /// requests. Therefore capacity can not be relied upon to be precisely
467 /// minimal. Prefer `reserve` if future insertions are expected.
471 /// Panics if the new capacity overflows `usize`.
476 /// let mut vec = vec![1];
477 /// vec.reserve_exact(10);
478 /// assert!(vec.capacity() >= 11);
480 #[stable(feature = "rust1", since = "1.0.0")]
481 pub fn reserve_exact(&mut self, additional: usize) {
482 self.buf.reserve_exact(self.len, additional);
485 /// Shrinks the capacity of the vector as much as possible.
487 /// It will drop down as close as possible to the length but the allocator
488 /// may still inform the vector that there is space for a few more elements.
493 /// let mut vec = Vec::with_capacity(10);
494 /// vec.extend([1, 2, 3].iter().cloned());
495 /// assert_eq!(vec.capacity(), 10);
496 /// vec.shrink_to_fit();
497 /// assert!(vec.capacity() >= 3);
499 #[stable(feature = "rust1", since = "1.0.0")]
500 pub fn shrink_to_fit(&mut self) {
501 self.buf.shrink_to_fit(self.len);
504 /// Converts the vector into [`Box<[T]>`][owned slice].
506 /// Note that this will drop any excess capacity. Calling this and
507 /// converting back to a vector with [`into_vec`] is equivalent to calling
508 /// [`shrink_to_fit`].
510 /// [owned slice]: ../../std/boxed/struct.Box.html
511 /// [`into_vec`]: ../../std/primitive.slice.html#method.into_vec
512 /// [`shrink_to_fit`]: #method.shrink_to_fit
517 /// let v = vec![1, 2, 3];
519 /// let slice = v.into_boxed_slice();
522 /// Any excess capacity is removed:
525 /// let mut vec = Vec::with_capacity(10);
526 /// vec.extend([1, 2, 3].iter().cloned());
528 /// assert_eq!(vec.capacity(), 10);
529 /// let slice = vec.into_boxed_slice();
530 /// assert_eq!(slice.into_vec().capacity(), 3);
532 #[stable(feature = "rust1", since = "1.0.0")]
533 pub fn into_boxed_slice(mut self) -> Box<[T]> {
535 self.shrink_to_fit();
536 let buf = ptr::read(&self.buf);
542 /// Shortens the vector, keeping the first `len` elements and dropping
545 /// If `len` is greater than the vector's current length, this has no
548 /// The [`drain`] method can emulate `truncate`, but causes the excess
549 /// elements to be returned instead of dropped.
551 /// Note that this method has no effect on the allocated capacity
556 /// Truncating a five element vector to two elements:
559 /// let mut vec = vec![1, 2, 3, 4, 5];
561 /// assert_eq!(vec, [1, 2]);
564 /// No truncation occurs when `len` is greater than the vector's current
568 /// let mut vec = vec![1, 2, 3];
570 /// assert_eq!(vec, [1, 2, 3]);
573 /// Truncating when `len == 0` is equivalent to calling the [`clear`]
577 /// let mut vec = vec![1, 2, 3];
579 /// assert_eq!(vec, []);
582 /// [`clear`]: #method.clear
583 /// [`drain`]: #method.drain
584 #[stable(feature = "rust1", since = "1.0.0")]
585 pub fn truncate(&mut self, len: usize) {
587 // drop any extra elements
588 while len < self.len {
589 // decrement len before the drop_in_place(), so a panic on Drop
590 // doesn't re-drop the just-failed value.
593 ptr::drop_in_place(self.get_unchecked_mut(len));
598 /// Extracts a slice containing the entire vector.
600 /// Equivalent to `&s[..]`.
605 /// use std::io::{self, Write};
606 /// let buffer = vec![1, 2, 3, 5, 8];
607 /// io::sink().write(buffer.as_slice()).unwrap();
610 #[stable(feature = "vec_as_slice", since = "1.7.0")]
611 pub fn as_slice(&self) -> &[T] {
615 /// Extracts a mutable slice of the entire vector.
617 /// Equivalent to `&mut s[..]`.
622 /// use std::io::{self, Read};
623 /// let mut buffer = vec![0; 3];
624 /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();
627 #[stable(feature = "vec_as_slice", since = "1.7.0")]
628 pub fn as_mut_slice(&mut self) -> &mut [T] {
632 /// Sets the length of a vector.
634 /// This will explicitly set the size of the vector, without actually
635 /// modifying its buffers, so it is up to the caller to ensure that the
636 /// vector is actually the specified size.
643 /// let mut vec = vec!['r', 'u', 's', 't'];
646 /// ptr::drop_in_place(&mut vec[3]);
649 /// assert_eq!(vec, ['r', 'u', 's']);
652 /// In this example, there is a memory leak since the memory locations
653 /// owned by the inner vectors were not freed prior to the `set_len` call:
656 /// let mut vec = vec![vec![1, 0, 0],
664 /// In this example, the vector gets expanded from zero to four items
665 /// without any memory allocations occurring, resulting in vector
666 /// values of unallocated memory:
669 /// let mut vec: Vec<char> = Vec::new();
676 #[stable(feature = "rust1", since = "1.0.0")]
677 pub unsafe fn set_len(&mut self, len: usize) {
681 /// Removes an element from anywhere in the vector and return it, replacing
682 /// it with the last element.
684 /// This does not preserve ordering, but is O(1).
688 /// Panics if `index` is out of bounds.
693 /// let mut v = vec!["foo", "bar", "baz", "qux"];
695 /// assert_eq!(v.swap_remove(1), "bar");
696 /// assert_eq!(v, ["foo", "qux", "baz"]);
698 /// assert_eq!(v.swap_remove(0), "foo");
699 /// assert_eq!(v, ["baz", "qux"]);
702 #[stable(feature = "rust1", since = "1.0.0")]
703 pub fn swap_remove(&mut self, index: usize) -> T {
704 let length = self.len();
705 self.swap(index, length - 1);
709 /// Inserts an element at position `index` within the vector, shifting all
710 /// elements after it to the right.
714 /// Panics if `index` is out of bounds.
719 /// let mut vec = vec![1, 2, 3];
720 /// vec.insert(1, 4);
721 /// assert_eq!(vec, [1, 4, 2, 3]);
722 /// vec.insert(4, 5);
723 /// assert_eq!(vec, [1, 4, 2, 3, 5]);
725 #[stable(feature = "rust1", since = "1.0.0")]
726 pub fn insert(&mut self, index: usize, element: T) {
727 let len = self.len();
728 assert!(index <= len);
730 // space for the new element
731 if len == self.buf.cap() {
737 // The spot to put the new value
739 let p = self.as_mut_ptr().offset(index as isize);
740 // Shift everything over to make space. (Duplicating the
741 // `index`th element into two consecutive places.)
742 ptr::copy(p, p.offset(1), len - index);
743 // Write it in, overwriting the first copy of the `index`th
745 ptr::write(p, element);
747 self.set_len(len + 1);
751 /// Removes and returns the element at position `index` within the vector,
752 /// shifting all elements after it to the left.
756 /// Panics if `index` is out of bounds.
761 /// let mut v = vec![1, 2, 3];
762 /// assert_eq!(v.remove(1), 2);
763 /// assert_eq!(v, [1, 3]);
765 #[stable(feature = "rust1", since = "1.0.0")]
766 pub fn remove(&mut self, index: usize) -> T {
767 let len = self.len();
768 assert!(index < len);
773 // the place we are taking from.
774 let ptr = self.as_mut_ptr().offset(index as isize);
775 // copy it out, unsafely having a copy of the value on
776 // the stack and in the vector at the same time.
777 ret = ptr::read(ptr);
779 // Shift everything down to fill in that spot.
780 ptr::copy(ptr.offset(1), ptr, len - index - 1);
782 self.set_len(len - 1);
787 /// Retains only the elements specified by the predicate.
789 /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
790 /// This method operates in place and preserves the order of the retained
796 /// let mut vec = vec![1, 2, 3, 4];
797 /// vec.retain(|&x| x%2 == 0);
798 /// assert_eq!(vec, [2, 4]);
800 #[stable(feature = "rust1", since = "1.0.0")]
801 pub fn retain<F>(&mut self, mut f: F)
802 where F: FnMut(&T) -> bool
804 let len = self.len();
818 self.truncate(len - del);
822 /// Removes consecutive elements in the vector that resolve to the same key.
824 /// If the vector is sorted, this removes all duplicates.
829 /// let mut vec = vec![10, 20, 21, 30, 20];
831 /// vec.dedup_by_key(|i| *i / 10);
833 /// assert_eq!(vec, [10, 20, 30, 20]);
835 #[stable(feature = "dedup_by", since = "1.16.0")]
837 pub fn dedup_by_key<F, K>(&mut self, mut key: F) where F: FnMut(&mut T) -> K, K: PartialEq {
838 self.dedup_by(|a, b| key(a) == key(b))
841 /// Removes consecutive elements in the vector that resolve to the same key.
843 /// If the vector is sorted, this removes all duplicates.
848 /// use std::ascii::AsciiExt;
850 /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];
852 /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));
854 /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]);
856 #[stable(feature = "dedup_by", since = "1.16.0")]
857 pub fn dedup_by<F>(&mut self, mut same_bucket: F) where F: FnMut(&mut T, &mut T) -> bool {
859 // Although we have a mutable reference to `self`, we cannot make
860 // *arbitrary* changes. The `same_bucket` calls could panic, so we
861 // must ensure that the vector is in a valid state at all time.
863 // The way that we handle this is by using swaps; we iterate
864 // over all the elements, swapping as we go so that at the end
865 // the elements we wish to keep are in the front, and those we
866 // wish to reject are at the back. We can then truncate the
867 // vector. This operation is still O(n).
869 // Example: We start in this state, where `r` represents "next
870 // read" and `w` represents "next_write`.
873 // +---+---+---+---+---+---+
874 // | 0 | 1 | 1 | 2 | 3 | 3 |
875 // +---+---+---+---+---+---+
878 // Comparing self[r] against self[w-1], this is not a duplicate, so
879 // we swap self[r] and self[w] (no effect as r==w) and then increment both
880 // r and w, leaving us with:
883 // +---+---+---+---+---+---+
884 // | 0 | 1 | 1 | 2 | 3 | 3 |
885 // +---+---+---+---+---+---+
888 // Comparing self[r] against self[w-1], this value is a duplicate,
889 // so we increment `r` but leave everything else unchanged:
892 // +---+---+---+---+---+---+
893 // | 0 | 1 | 1 | 2 | 3 | 3 |
894 // +---+---+---+---+---+---+
897 // Comparing self[r] against self[w-1], this is not a duplicate,
898 // so swap self[r] and self[w] and advance r and w:
901 // +---+---+---+---+---+---+
902 // | 0 | 1 | 2 | 1 | 3 | 3 |
903 // +---+---+---+---+---+---+
906 // Not a duplicate, repeat:
909 // +---+---+---+---+---+---+
910 // | 0 | 1 | 2 | 3 | 1 | 3 |
911 // +---+---+---+---+---+---+
914 // Duplicate, advance r. End of vec. Truncate to w.
921 // Avoid bounds checks by using raw pointers.
922 let p = self.as_mut_ptr();
923 let mut r: usize = 1;
924 let mut w: usize = 1;
927 let p_r = p.offset(r as isize);
928 let p_wm1 = p.offset((w - 1) as isize);
929 if !same_bucket(&mut *p_r, &mut *p_wm1) {
931 let p_w = p_wm1.offset(1);
932 mem::swap(&mut *p_r, &mut *p_w);
943 /// Appends an element to the back of a collection.
947 /// Panics if the number of elements in the vector overflows a `usize`.
952 /// let mut vec = vec![1, 2];
954 /// assert_eq!(vec, [1, 2, 3]);
957 #[stable(feature = "rust1", since = "1.0.0")]
958 pub fn push(&mut self, value: T) {
959 // This will panic or abort if we would allocate > isize::MAX bytes
960 // or if the length increment would overflow for zero-sized types.
961 if self.len == self.buf.cap() {
965 let end = self.as_mut_ptr().offset(self.len as isize);
966 ptr::write(end, value);
971 /// Removes the last element from a vector and returns it, or [`None`] if it
974 /// [`None`]: ../../std/option/enum.Option.html#variant.None
979 /// let mut vec = vec![1, 2, 3];
980 /// assert_eq!(vec.pop(), Some(3));
981 /// assert_eq!(vec, [1, 2]);
984 #[stable(feature = "rust1", since = "1.0.0")]
985 pub fn pop(&mut self) -> Option<T> {
991 Some(ptr::read(self.get_unchecked(self.len())))
996 /// Moves all the elements of `other` into `Self`, leaving `other` empty.
1000 /// Panics if the number of elements in the vector overflows a `usize`.
1005 /// let mut vec = vec![1, 2, 3];
1006 /// let mut vec2 = vec![4, 5, 6];
1007 /// vec.append(&mut vec2);
1008 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
1009 /// assert_eq!(vec2, []);
1012 #[stable(feature = "append", since = "1.4.0")]
1013 pub fn append(&mut self, other: &mut Self) {
1014 self.reserve(other.len());
1015 let len = self.len();
1017 ptr::copy_nonoverlapping(other.as_ptr(), self.get_unchecked_mut(len), other.len());
1020 self.len += other.len();
1026 /// Create a draining iterator that removes the specified range in the vector
1027 /// and yields the removed items.
1029 /// Note 1: The element range is removed even if the iterator is only
1030 /// partially consumed or not consumed at all.
1032 /// Note 2: It is unspecified how many elements are removed from the vector,
1033 /// if the `Drain` value is leaked.
1037 /// Panics if the starting point is greater than the end point or if
1038 /// the end point is greater than the length of the vector.
1043 /// let mut v = vec![1, 2, 3];
1044 /// let u: Vec<_> = v.drain(1..).collect();
1045 /// assert_eq!(v, &[1]);
1046 /// assert_eq!(u, &[2, 3]);
1048 /// // A full range clears the vector
1050 /// assert_eq!(v, &[]);
1052 #[stable(feature = "drain", since = "1.6.0")]
1053 pub fn drain<R>(&mut self, range: R) -> Drain<T>
1054 where R: RangeArgument<usize>
1058 // When the Drain is first created, it shortens the length of
1059 // the source vector to make sure no uninitalized or moved-from elements
1060 // are accessible at all if the Drain's destructor never gets to run.
1062 // Drain will ptr::read out the values to remove.
1063 // When finished, remaining tail of the vec is copied back to cover
1064 // the hole, and the vector length is restored to the new length.
1066 let len = self.len();
1067 let start = match range.start() {
1069 Excluded(&n) => n + 1,
1072 let end = match range.end() {
1073 Included(&n) => n + 1,
1077 assert!(start <= end);
1078 assert!(end <= len);
1081 // set self.vec length's to start, to be safe in case Drain is leaked
1082 self.set_len(start);
1083 // Use the borrow in the IterMut to indicate borrowing behavior of the
1084 // whole Drain iterator (like &mut T).
1085 let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().offset(start as isize),
1089 tail_len: len - end,
1090 iter: range_slice.iter(),
1091 vec: Shared::new(self as *mut _),
1096 /// Clears the vector, removing all values.
1098 /// Note that this method has no effect on the allocated capacity
1104 /// let mut v = vec![1, 2, 3];
1108 /// assert!(v.is_empty());
1111 #[stable(feature = "rust1", since = "1.0.0")]
1112 pub fn clear(&mut self) {
1116 /// Returns the number of elements in the vector.
1121 /// let a = vec![1, 2, 3];
1122 /// assert_eq!(a.len(), 3);
1125 #[stable(feature = "rust1", since = "1.0.0")]
1126 pub fn len(&self) -> usize {
1130 /// Returns `true` if the vector contains no elements.
1135 /// let mut v = Vec::new();
1136 /// assert!(v.is_empty());
1139 /// assert!(!v.is_empty());
1141 #[stable(feature = "rust1", since = "1.0.0")]
1142 pub fn is_empty(&self) -> bool {
1146 /// Splits the collection into two at the given index.
1148 /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`,
1149 /// and the returned `Self` contains elements `[at, len)`.
1151 /// Note that the capacity of `self` does not change.
1155 /// Panics if `at > len`.
1160 /// let mut vec = vec![1,2,3];
1161 /// let vec2 = vec.split_off(1);
1162 /// assert_eq!(vec, [1]);
1163 /// assert_eq!(vec2, [2, 3]);
1166 #[stable(feature = "split_off", since = "1.4.0")]
1167 pub fn split_off(&mut self, at: usize) -> Self {
1168 assert!(at <= self.len(), "`at` out of bounds");
1170 let other_len = self.len - at;
1171 let mut other = Vec::with_capacity(other_len);
1173 // Unsafely `set_len` and copy items to `other`.
1176 other.set_len(other_len);
1178 ptr::copy_nonoverlapping(self.as_ptr().offset(at as isize),
1186 impl<T: Clone> Vec<T> {
1187 /// Resizes the `Vec` in-place so that `len()` is equal to `new_len`.
1189 /// If `new_len` is greater than `len()`, the `Vec` is extended by the
1190 /// difference, with each additional slot filled with `value`.
1191 /// If `new_len` is less than `len()`, the `Vec` is simply truncated.
1196 /// let mut vec = vec!["hello"];
1197 /// vec.resize(3, "world");
1198 /// assert_eq!(vec, ["hello", "world", "world"]);
1200 /// let mut vec = vec![1, 2, 3, 4];
1201 /// vec.resize(2, 0);
1202 /// assert_eq!(vec, [1, 2]);
1204 #[stable(feature = "vec_resize", since = "1.5.0")]
1205 pub fn resize(&mut self, new_len: usize, value: T) {
1206 let len = self.len();
1209 self.extend_with_element(new_len - len, value);
1211 self.truncate(new_len);
1215 /// Extend the vector by `n` additional clones of `value`.
1216 fn extend_with_element(&mut self, n: usize, value: T) {
1220 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1221 // Use SetLenOnDrop to work around bug where compiler
1222 // may not realize the store through `ptr` through self.set_len()
1224 let mut local_len = SetLenOnDrop::new(&mut self.len);
1226 // Write all elements except the last one
1228 ptr::write(ptr, value.clone());
1229 ptr = ptr.offset(1);
1230 // Increment the length in every step in case clone() panics
1231 local_len.increment_len(1);
1235 // We can write the last element directly without cloning needlessly
1236 ptr::write(ptr, value);
1237 local_len.increment_len(1);
1240 // len set by scope guard
1244 /// Clones and appends all elements in a slice to the `Vec`.
1246 /// Iterates over the slice `other`, clones each element, and then appends
1247 /// it to this `Vec`. The `other` vector is traversed in-order.
1249 /// Note that this function is same as `extend` except that it is
1250 /// specialized to work with slices instead. If and when Rust gets
1251 /// specialization this function will likely be deprecated (but still
1257 /// let mut vec = vec![1];
1258 /// vec.extend_from_slice(&[2, 3, 4]);
1259 /// assert_eq!(vec, [1, 2, 3, 4]);
1261 #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
1262 pub fn extend_from_slice(&mut self, other: &[T]) {
1263 self.spec_extend(other.iter())
1266 /// Returns a place for insertion at the back of the `Vec`.
1268 /// Using this method with placement syntax is equivalent to [`push`](#method.push),
1269 /// but may be more efficient.
1274 /// #![feature(collection_placement)]
1275 /// #![feature(placement_in_syntax)]
1277 /// let mut vec = vec![1, 2];
1278 /// vec.place_back() <- 3;
1279 /// vec.place_back() <- 4;
1280 /// assert_eq!(&vec, &[1, 2, 3, 4]);
1282 #[unstable(feature = "collection_placement",
1283 reason = "placement protocol is subject to change",
1285 pub fn place_back(&mut self) -> PlaceBack<T> {
1286 PlaceBack { vec: self }
1290 // Set the length of the vec when the `SetLenOnDrop` value goes out of scope.
1292 // The idea is: The length field in SetLenOnDrop is a local variable
1293 // that the optimizer will see does not alias with any stores through the Vec's data
1294 // pointer. This is a workaround for alias analysis issue #32155
1295 struct SetLenOnDrop<'a> {
1300 impl<'a> SetLenOnDrop<'a> {
1302 fn new(len: &'a mut usize) -> Self {
1303 SetLenOnDrop { local_len: *len, len: len }
1307 fn increment_len(&mut self, increment: usize) {
1308 self.local_len += increment;
1312 impl<'a> Drop for SetLenOnDrop<'a> {
1314 fn drop(&mut self) {
1315 *self.len = self.local_len;
1319 impl<T: PartialEq> Vec<T> {
1320 /// Removes consecutive repeated elements in the vector.
1322 /// If the vector is sorted, this removes all duplicates.
1327 /// let mut vec = vec![1, 2, 2, 3, 2];
1331 /// assert_eq!(vec, [1, 2, 3, 2]);
1333 #[stable(feature = "rust1", since = "1.0.0")]
1335 pub fn dedup(&mut self) {
1336 self.dedup_by(|a, b| a == b)
1339 /// Removes the first instance of `item` from the vector if the item exists.
1344 ///# #![feature(vec_remove_item)]
1345 /// let mut vec = vec![1, 2, 3, 1];
1347 /// vec.remove_item(&1);
1349 /// assert_eq!(vec, vec![2, 3, 1]);
1351 #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")]
1352 pub fn remove_item(&mut self, item: &T) -> Option<T> {
1353 let pos = match self.iter().position(|x| *x == *item) {
1355 None => return None,
1357 Some(self.remove(pos))
1361 ////////////////////////////////////////////////////////////////////////////////
1362 // Internal methods and functions
1363 ////////////////////////////////////////////////////////////////////////////////
1366 #[stable(feature = "rust1", since = "1.0.0")]
1367 pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
1368 let mut v = Vec::with_capacity(n);
1369 v.extend_with_element(n, elem);
1373 ////////////////////////////////////////////////////////////////////////////////
1374 // Common trait implementations for Vec
1375 ////////////////////////////////////////////////////////////////////////////////
1377 #[stable(feature = "rust1", since = "1.0.0")]
1378 impl<T: Clone> Clone for Vec<T> {
1380 fn clone(&self) -> Vec<T> {
1381 <[T]>::to_vec(&**self)
1384 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
1385 // required for this method definition, is not available. Instead use the
1386 // `slice::to_vec` function which is only available with cfg(test)
1387 // NB see the slice::hack module in slice.rs for more information
1389 fn clone(&self) -> Vec<T> {
1390 ::slice::to_vec(&**self)
1393 fn clone_from(&mut self, other: &Vec<T>) {
1394 // drop anything in self that will not be overwritten
1395 self.truncate(other.len());
1396 let len = self.len();
1398 // reuse the contained values' allocations/resources.
1399 self.clone_from_slice(&other[..len]);
1401 // self.len <= other.len due to the truncate above, so the
1402 // slice here is always in-bounds.
1403 self.extend_from_slice(&other[len..]);
1407 #[stable(feature = "rust1", since = "1.0.0")]
1408 impl<T: Hash> Hash for Vec<T> {
1410 fn hash<H: hash::Hasher>(&self, state: &mut H) {
1411 Hash::hash(&**self, state)
1415 #[stable(feature = "rust1", since = "1.0.0")]
1416 impl<T> Index<usize> for Vec<T> {
1420 fn index(&self, index: usize) -> &T {
1421 // NB built-in indexing via `&[T]`
1426 #[stable(feature = "rust1", since = "1.0.0")]
1427 impl<T> IndexMut<usize> for Vec<T> {
1429 fn index_mut(&mut self, index: usize) -> &mut T {
1430 // NB built-in indexing via `&mut [T]`
1431 &mut (**self)[index]
1436 #[stable(feature = "rust1", since = "1.0.0")]
1437 impl<T> ops::Index<ops::Range<usize>> for Vec<T> {
1441 fn index(&self, index: ops::Range<usize>) -> &[T] {
1442 Index::index(&**self, index)
1445 #[stable(feature = "rust1", since = "1.0.0")]
1446 impl<T> ops::Index<ops::RangeTo<usize>> for Vec<T> {
1450 fn index(&self, index: ops::RangeTo<usize>) -> &[T] {
1451 Index::index(&**self, index)
1454 #[stable(feature = "rust1", since = "1.0.0")]
1455 impl<T> ops::Index<ops::RangeFrom<usize>> for Vec<T> {
1459 fn index(&self, index: ops::RangeFrom<usize>) -> &[T] {
1460 Index::index(&**self, index)
1463 #[stable(feature = "rust1", since = "1.0.0")]
1464 impl<T> ops::Index<ops::RangeFull> for Vec<T> {
1468 fn index(&self, _index: ops::RangeFull) -> &[T] {
1472 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1473 impl<T> ops::Index<ops::RangeInclusive<usize>> for Vec<T> {
1477 fn index(&self, index: ops::RangeInclusive<usize>) -> &[T] {
1478 Index::index(&**self, index)
1481 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1482 impl<T> ops::Index<ops::RangeToInclusive<usize>> for Vec<T> {
1486 fn index(&self, index: ops::RangeToInclusive<usize>) -> &[T] {
1487 Index::index(&**self, index)
1491 #[stable(feature = "rust1", since = "1.0.0")]
1492 impl<T> ops::IndexMut<ops::Range<usize>> for Vec<T> {
1494 fn index_mut(&mut self, index: ops::Range<usize>) -> &mut [T] {
1495 IndexMut::index_mut(&mut **self, index)
1498 #[stable(feature = "rust1", since = "1.0.0")]
1499 impl<T> ops::IndexMut<ops::RangeTo<usize>> for Vec<T> {
1501 fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut [T] {
1502 IndexMut::index_mut(&mut **self, index)
1505 #[stable(feature = "rust1", since = "1.0.0")]
1506 impl<T> ops::IndexMut<ops::RangeFrom<usize>> for Vec<T> {
1508 fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut [T] {
1509 IndexMut::index_mut(&mut **self, index)
1512 #[stable(feature = "rust1", since = "1.0.0")]
1513 impl<T> ops::IndexMut<ops::RangeFull> for Vec<T> {
1515 fn index_mut(&mut self, _index: ops::RangeFull) -> &mut [T] {
1519 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1520 impl<T> ops::IndexMut<ops::RangeInclusive<usize>> for Vec<T> {
1522 fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut [T] {
1523 IndexMut::index_mut(&mut **self, index)
1526 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1527 impl<T> ops::IndexMut<ops::RangeToInclusive<usize>> for Vec<T> {
1529 fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut [T] {
1530 IndexMut::index_mut(&mut **self, index)
1534 #[stable(feature = "rust1", since = "1.0.0")]
1535 impl<T> ops::Deref for Vec<T> {
1538 fn deref(&self) -> &[T] {
1540 let p = self.buf.ptr();
1541 assume(!p.is_null());
1542 slice::from_raw_parts(p, self.len)
1547 #[stable(feature = "rust1", since = "1.0.0")]
1548 impl<T> ops::DerefMut for Vec<T> {
1549 fn deref_mut(&mut self) -> &mut [T] {
1551 let ptr = self.buf.ptr();
1552 assume(!ptr.is_null());
1553 slice::from_raw_parts_mut(ptr, self.len)
1558 #[stable(feature = "rust1", since = "1.0.0")]
1559 impl<T> FromIterator<T> for Vec<T> {
1561 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> {
1562 <Self as SpecExtend<_, _>>::from_iter(iter.into_iter())
1566 #[stable(feature = "rust1", since = "1.0.0")]
1567 impl<T> IntoIterator for Vec<T> {
1569 type IntoIter = IntoIter<T>;
1571 /// Creates a consuming iterator, that is, one that moves each value out of
1572 /// the vector (from start to end). The vector cannot be used after calling
1578 /// let v = vec!["a".to_string(), "b".to_string()];
1579 /// for s in v.into_iter() {
1580 /// // s has type String, not &String
1581 /// println!("{}", s);
1585 fn into_iter(mut self) -> IntoIter<T> {
1587 let begin = self.as_mut_ptr();
1588 assume(!begin.is_null());
1589 let end = if mem::size_of::<T>() == 0 {
1590 arith_offset(begin as *const i8, self.len() as isize) as *const T
1592 begin.offset(self.len() as isize) as *const T
1594 let cap = self.buf.cap();
1597 buf: Shared::new(begin),
1606 #[stable(feature = "rust1", since = "1.0.0")]
1607 impl<'a, T> IntoIterator for &'a Vec<T> {
1609 type IntoIter = slice::Iter<'a, T>;
1611 fn into_iter(self) -> slice::Iter<'a, T> {
1616 #[stable(feature = "rust1", since = "1.0.0")]
1617 impl<'a, T> IntoIterator for &'a mut Vec<T> {
1618 type Item = &'a mut T;
1619 type IntoIter = slice::IterMut<'a, T>;
1621 fn into_iter(mut self) -> slice::IterMut<'a, T> {
1626 #[stable(feature = "rust1", since = "1.0.0")]
1627 impl<T> Extend<T> for Vec<T> {
1629 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1630 self.spec_extend(iter.into_iter())
1634 // Specialization trait used for Vec::from_iter and Vec::extend
1635 trait SpecExtend<T, I> {
1636 fn from_iter(iter: I) -> Self;
1637 fn spec_extend(&mut self, iter: I);
1640 impl<T, I> SpecExtend<T, I> for Vec<T>
1641 where I: Iterator<Item=T>,
1643 default fn from_iter(mut iterator: I) -> Self {
1644 // Unroll the first iteration, as the vector is going to be
1645 // expanded on this iteration in every case when the iterable is not
1646 // empty, but the loop in extend_desugared() is not going to see the
1647 // vector being full in the few subsequent loop iterations.
1648 // So we get better branch prediction.
1649 let mut vector = match iterator.next() {
1650 None => return Vec::new(),
1652 let (lower, _) = iterator.size_hint();
1653 let mut vector = Vec::with_capacity(lower.saturating_add(1));
1655 ptr::write(vector.get_unchecked_mut(0), element);
1661 vector.spec_extend(iterator);
1665 default fn spec_extend(&mut self, iter: I) {
1666 self.extend_desugared(iter)
1670 impl<T, I> SpecExtend<T, I> for Vec<T>
1671 where I: TrustedLen<Item=T>,
1673 fn from_iter(iterator: I) -> Self {
1674 let mut vector = Vec::new();
1675 vector.spec_extend(iterator);
1679 fn spec_extend(&mut self, iterator: I) {
1680 // This is the case for a TrustedLen iterator.
1681 let (low, high) = iterator.size_hint();
1682 if let Some(high_value) = high {
1683 debug_assert_eq!(low, high_value,
1684 "TrustedLen iterator's size hint is not exact: {:?}",
1687 if let Some(additional) = high {
1688 self.reserve(additional);
1690 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1691 let mut local_len = SetLenOnDrop::new(&mut self.len);
1692 for element in iterator {
1693 ptr::write(ptr, element);
1694 ptr = ptr.offset(1);
1695 // NB can't overflow since we would have had to alloc the address space
1696 local_len.increment_len(1);
1700 self.extend_desugared(iterator)
1705 impl<'a, T: 'a, I> SpecExtend<&'a T, I> for Vec<T>
1706 where I: Iterator<Item=&'a T>,
1709 default fn from_iter(iterator: I) -> Self {
1710 SpecExtend::from_iter(iterator.cloned())
1713 default fn spec_extend(&mut self, iterator: I) {
1714 self.spec_extend(iterator.cloned())
1718 impl<'a, T: 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T>
1721 fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
1722 let slice = iterator.as_slice();
1723 self.reserve(slice.len());
1725 let len = self.len();
1726 self.set_len(len + slice.len());
1727 self.get_unchecked_mut(len..).copy_from_slice(slice);
1733 fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
1734 // This is the case for a general iterator.
1736 // This function should be the moral equivalent of:
1738 // for item in iterator {
1741 while let Some(element) = iterator.next() {
1742 let len = self.len();
1743 if len == self.capacity() {
1744 let (lower, _) = iterator.size_hint();
1745 self.reserve(lower.saturating_add(1));
1748 ptr::write(self.get_unchecked_mut(len), element);
1749 // NB can't overflow since we would have had to alloc the address space
1750 self.set_len(len + 1);
1756 #[stable(feature = "extend_ref", since = "1.2.0")]
1757 impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> {
1758 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
1759 self.spec_extend(iter.into_iter())
1763 macro_rules! __impl_slice_eq1 {
1764 ($Lhs: ty, $Rhs: ty) => {
1765 __impl_slice_eq1! { $Lhs, $Rhs, Sized }
1767 ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
1768 #[stable(feature = "rust1", since = "1.0.0")]
1769 impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
1771 fn eq(&self, other: &$Rhs) -> bool { self[..] == other[..] }
1773 fn ne(&self, other: &$Rhs) -> bool { self[..] != other[..] }
1778 __impl_slice_eq1! { Vec<A>, Vec<B> }
1779 __impl_slice_eq1! { Vec<A>, &'b [B] }
1780 __impl_slice_eq1! { Vec<A>, &'b mut [B] }
1781 __impl_slice_eq1! { Cow<'a, [A]>, &'b [B], Clone }
1782 __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B], Clone }
1783 __impl_slice_eq1! { Cow<'a, [A]>, Vec<B>, Clone }
1785 macro_rules! array_impls {
1788 // NOTE: some less important impls are omitted to reduce code bloat
1789 __impl_slice_eq1! { Vec<A>, [B; $N] }
1790 __impl_slice_eq1! { Vec<A>, &'b [B; $N] }
1791 // __impl_slice_eq1! { Vec<A>, &'b mut [B; $N] }
1792 // __impl_slice_eq1! { Cow<'a, [A]>, [B; $N], Clone }
1793 // __impl_slice_eq1! { Cow<'a, [A]>, &'b [B; $N], Clone }
1794 // __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
1801 10 11 12 13 14 15 16 17 18 19
1802 20 21 22 23 24 25 26 27 28 29
1806 /// Implements comparison of vectors, lexicographically.
1807 #[stable(feature = "rust1", since = "1.0.0")]
1808 impl<T: PartialOrd> PartialOrd for Vec<T> {
1810 fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> {
1811 PartialOrd::partial_cmp(&**self, &**other)
1815 #[stable(feature = "rust1", since = "1.0.0")]
1816 impl<T: Eq> Eq for Vec<T> {}
1818 /// Implements ordering of vectors, lexicographically.
1819 #[stable(feature = "rust1", since = "1.0.0")]
1820 impl<T: Ord> Ord for Vec<T> {
1822 fn cmp(&self, other: &Vec<T>) -> Ordering {
1823 Ord::cmp(&**self, &**other)
1827 #[stable(feature = "rust1", since = "1.0.0")]
1828 unsafe impl<#[may_dangle] T> Drop for Vec<T> {
1829 fn drop(&mut self) {
1832 ptr::drop_in_place(&mut self[..]);
1834 // RawVec handles deallocation
1838 #[stable(feature = "rust1", since = "1.0.0")]
1839 impl<T> Default for Vec<T> {
1840 /// Creates an empty `Vec<T>`.
1841 fn default() -> Vec<T> {
1846 #[stable(feature = "rust1", since = "1.0.0")]
1847 impl<T: fmt::Debug> fmt::Debug for Vec<T> {
1848 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1849 fmt::Debug::fmt(&**self, f)
1853 #[stable(feature = "rust1", since = "1.0.0")]
1854 impl<T> AsRef<Vec<T>> for Vec<T> {
1855 fn as_ref(&self) -> &Vec<T> {
1860 #[stable(feature = "vec_as_mut", since = "1.5.0")]
1861 impl<T> AsMut<Vec<T>> for Vec<T> {
1862 fn as_mut(&mut self) -> &mut Vec<T> {
1867 #[stable(feature = "rust1", since = "1.0.0")]
1868 impl<T> AsRef<[T]> for Vec<T> {
1869 fn as_ref(&self) -> &[T] {
1874 #[stable(feature = "vec_as_mut", since = "1.5.0")]
1875 impl<T> AsMut<[T]> for Vec<T> {
1876 fn as_mut(&mut self) -> &mut [T] {
1881 #[stable(feature = "rust1", since = "1.0.0")]
1882 impl<'a, T: Clone> From<&'a [T]> for Vec<T> {
1884 fn from(s: &'a [T]) -> Vec<T> {
1888 fn from(s: &'a [T]) -> Vec<T> {
1893 #[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
1894 impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where [T]: ToOwned<Owned=Vec<T>> {
1895 fn from(s: Cow<'a, [T]>) -> Vec<T> {
1900 // note: test pulls in libstd, which causes errors here
1902 #[stable(feature = "vec_from_box", since = "1.17.0")]
1903 impl<T> From<Box<[T]>> for Vec<T> {
1904 fn from(s: Box<[T]>) -> Vec<T> {
1909 #[stable(feature = "box_from_vec", since = "1.17.0")]
1910 impl<T> Into<Box<[T]>> for Vec<T> {
1911 fn into(self) -> Box<[T]> {
1912 self.into_boxed_slice()
1916 #[stable(feature = "rust1", since = "1.0.0")]
1917 impl<'a> From<&'a str> for Vec<u8> {
1918 fn from(s: &'a str) -> Vec<u8> {
1919 From::from(s.as_bytes())
1923 ////////////////////////////////////////////////////////////////////////////////
1925 ////////////////////////////////////////////////////////////////////////////////
1927 #[stable(feature = "cow_from_vec", since = "1.7.0")]
1928 impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> {
1929 fn from(s: &'a [T]) -> Cow<'a, [T]> {
1934 #[stable(feature = "cow_from_vec", since = "1.7.0")]
1935 impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> {
1936 fn from(v: Vec<T>) -> Cow<'a, [T]> {
1941 #[stable(feature = "rust1", since = "1.0.0")]
1942 impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone {
1943 fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {
1944 Cow::Owned(FromIterator::from_iter(it))
1948 ////////////////////////////////////////////////////////////////////////////////
1950 ////////////////////////////////////////////////////////////////////////////////
1952 /// An iterator that moves out of a vector.
1954 /// This `struct` is created by the `into_iter` method on [`Vec`][`Vec`] (provided
1955 /// by the [`IntoIterator`] trait).
1957 /// [`Vec`]: struct.Vec.html
1958 /// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html
1959 #[stable(feature = "rust1", since = "1.0.0")]
1960 pub struct IntoIter<T> {
1967 #[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
1968 impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
1969 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1970 f.debug_tuple("IntoIter")
1971 .field(&self.as_slice())
1976 impl<T> IntoIter<T> {
1977 /// Returns the remaining items of this iterator as a slice.
1982 /// let vec = vec!['a', 'b', 'c'];
1983 /// let mut into_iter = vec.into_iter();
1984 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
1985 /// let _ = into_iter.next().unwrap();
1986 /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
1988 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
1989 pub fn as_slice(&self) -> &[T] {
1991 slice::from_raw_parts(self.ptr, self.len())
1995 /// Returns the remaining items of this iterator as a mutable slice.
2000 /// let vec = vec!['a', 'b', 'c'];
2001 /// let mut into_iter = vec.into_iter();
2002 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
2003 /// into_iter.as_mut_slice()[2] = 'z';
2004 /// assert_eq!(into_iter.next().unwrap(), 'a');
2005 /// assert_eq!(into_iter.next().unwrap(), 'b');
2006 /// assert_eq!(into_iter.next().unwrap(), 'z');
2008 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
2009 pub fn as_mut_slice(&mut self) -> &mut [T] {
2011 slice::from_raw_parts_mut(self.ptr as *mut T, self.len())
2016 #[stable(feature = "rust1", since = "1.0.0")]
2017 unsafe impl<T: Send> Send for IntoIter<T> {}
2018 #[stable(feature = "rust1", since = "1.0.0")]
2019 unsafe impl<T: Sync> Sync for IntoIter<T> {}
2021 #[stable(feature = "rust1", since = "1.0.0")]
2022 impl<T> Iterator for IntoIter<T> {
2026 fn next(&mut self) -> Option<T> {
2028 if self.ptr as *const _ == self.end {
2031 if mem::size_of::<T>() == 0 {
2032 // purposefully don't use 'ptr.offset' because for
2033 // vectors with 0-size elements this would return the
2035 self.ptr = arith_offset(self.ptr as *const i8, 1) as *mut T;
2037 // Use a non-null pointer value
2038 Some(ptr::read(EMPTY as *mut T))
2041 self.ptr = self.ptr.offset(1);
2043 Some(ptr::read(old))
2050 fn size_hint(&self) -> (usize, Option<usize>) {
2051 let diff = (self.end as usize) - (self.ptr as usize);
2052 let size = mem::size_of::<T>();
2059 (exact, Some(exact))
2063 fn count(self) -> usize {
2068 #[stable(feature = "rust1", since = "1.0.0")]
2069 impl<T> DoubleEndedIterator for IntoIter<T> {
2071 fn next_back(&mut self) -> Option<T> {
2073 if self.end == self.ptr {
2076 if mem::size_of::<T>() == 0 {
2077 // See above for why 'ptr.offset' isn't used
2078 self.end = arith_offset(self.end as *const i8, -1) as *mut T;
2080 // Use a non-null pointer value
2081 Some(ptr::read(EMPTY as *mut T))
2083 self.end = self.end.offset(-1);
2085 Some(ptr::read(self.end))
2092 #[stable(feature = "rust1", since = "1.0.0")]
2093 impl<T> ExactSizeIterator for IntoIter<T> {
2094 fn is_empty(&self) -> bool {
2095 self.ptr == self.end
2099 #[unstable(feature = "fused", issue = "35602")]
2100 impl<T> FusedIterator for IntoIter<T> {}
2102 #[unstable(feature = "trusted_len", issue = "37572")]
2103 unsafe impl<T> TrustedLen for IntoIter<T> {}
2105 #[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
2106 impl<T: Clone> Clone for IntoIter<T> {
2107 fn clone(&self) -> IntoIter<T> {
2108 self.as_slice().to_owned().into_iter()
2112 #[stable(feature = "rust1", since = "1.0.0")]
2113 unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
2114 fn drop(&mut self) {
2115 // destroy the remaining elements
2116 for _x in self.by_ref() {}
2118 // RawVec handles deallocation
2119 let _ = unsafe { RawVec::from_raw_parts(*self.buf, self.cap) };
2123 /// A draining iterator for `Vec<T>`.
2125 /// This `struct` is created by the [`drain`] method on [`Vec`].
2127 /// [`drain`]: struct.Vec.html#method.drain
2128 /// [`Vec`]: struct.Vec.html
2129 #[stable(feature = "drain", since = "1.6.0")]
2130 pub struct Drain<'a, T: 'a> {
2131 /// Index of tail to preserve
2135 /// Current remaining range to remove
2136 iter: slice::Iter<'a, T>,
2137 vec: Shared<Vec<T>>,
2140 #[stable(feature = "collection_debug", since = "1.17.0")]
2141 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
2142 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2143 f.debug_tuple("Drain")
2144 .field(&self.iter.as_slice())
2149 #[stable(feature = "drain", since = "1.6.0")]
2150 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
2151 #[stable(feature = "drain", since = "1.6.0")]
2152 unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
2154 #[stable(feature = "drain", since = "1.6.0")]
2155 impl<'a, T> Iterator for Drain<'a, T> {
2159 fn next(&mut self) -> Option<T> {
2160 self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
2163 fn size_hint(&self) -> (usize, Option<usize>) {
2164 self.iter.size_hint()
2168 #[stable(feature = "drain", since = "1.6.0")]
2169 impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
2171 fn next_back(&mut self) -> Option<T> {
2172 self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
2176 #[stable(feature = "drain", since = "1.6.0")]
2177 impl<'a, T> Drop for Drain<'a, T> {
2178 fn drop(&mut self) {
2179 // exhaust self first
2180 while let Some(_) = self.next() {}
2182 if self.tail_len > 0 {
2184 let source_vec = &mut **self.vec;
2185 // memmove back untouched tail, update to new length
2186 let start = source_vec.len();
2187 let tail = self.tail_start;
2188 let src = source_vec.as_ptr().offset(tail as isize);
2189 let dst = source_vec.as_mut_ptr().offset(start as isize);
2190 ptr::copy(src, dst, self.tail_len);
2191 source_vec.set_len(start + self.tail_len);
2198 #[stable(feature = "drain", since = "1.6.0")]
2199 impl<'a, T> ExactSizeIterator for Drain<'a, T> {
2200 fn is_empty(&self) -> bool {
2201 self.iter.is_empty()
2205 #[unstable(feature = "fused", issue = "35602")]
2206 impl<'a, T> FusedIterator for Drain<'a, T> {}
2208 /// A place for insertion at the back of a `Vec`.
2210 /// See [`Vec::place_back`](struct.Vec.html#method.place_back) for details.
2211 #[must_use = "places do nothing unless written to with `<-` syntax"]
2212 #[unstable(feature = "collection_placement",
2213 reason = "struct name and placement protocol are subject to change",
2216 pub struct PlaceBack<'a, T: 'a> {
2217 vec: &'a mut Vec<T>,
2220 #[unstable(feature = "collection_placement",
2221 reason = "placement protocol is subject to change",
2223 impl<'a, T> Placer<T> for PlaceBack<'a, T> {
2224 type Place = PlaceBack<'a, T>;
2226 fn make_place(self) -> Self {
2227 // This will panic or abort if we would allocate > isize::MAX bytes
2228 // or if the length increment would overflow for zero-sized types.
2229 if self.vec.len == self.vec.buf.cap() {
2230 self.vec.buf.double();
2236 #[unstable(feature = "collection_placement",
2237 reason = "placement protocol is subject to change",
2239 impl<'a, T> Place<T> for PlaceBack<'a, T> {
2240 fn pointer(&mut self) -> *mut T {
2241 unsafe { self.vec.as_mut_ptr().offset(self.vec.len as isize) }
2245 #[unstable(feature = "collection_placement",
2246 reason = "placement protocol is subject to change",
2248 impl<'a, T> InPlace<T> for PlaceBack<'a, T> {
2249 type Owner = &'a mut T;
2251 unsafe fn finalize(mut self) -> &'a mut T {
2252 let ptr = self.pointer();