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
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 core::cmp::Ordering;
71 use core::hash::{self, Hash};
72 use core::intrinsics::{arith_offset, assume};
73 use core::iter::{FromIterator, FusedIterator, TrustedLen};
74 use core::marker::PhantomData;
78 use core::ops::{InPlace, Index, IndexMut, Place, Placer};
81 use core::ptr::NonNull;
88 use super::range::RangeArgument;
89 use Bound::{Excluded, Included, Unbounded};
91 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
96 /// let mut vec = Vec::new();
100 /// assert_eq!(vec.len(), 2);
101 /// assert_eq!(vec[0], 1);
103 /// assert_eq!(vec.pop(), Some(2));
104 /// assert_eq!(vec.len(), 1);
107 /// assert_eq!(vec[0], 7);
109 /// vec.extend([1, 2, 3].iter().cloned());
112 /// println!("{}", x);
114 /// assert_eq!(vec, [7, 1, 2, 3]);
117 /// The [`vec!`] macro is provided to make initialization more convenient:
120 /// let mut vec = vec![1, 2, 3];
122 /// assert_eq!(vec, [1, 2, 3, 4]);
125 /// It can also initialize each element of a `Vec<T>` with a given value:
128 /// let vec = vec![0; 5];
129 /// assert_eq!(vec, [0, 0, 0, 0, 0]);
132 /// Use a `Vec<T>` as an efficient stack:
135 /// let mut stack = Vec::new();
141 /// while let Some(top) = stack.pop() {
142 /// // Prints 3, 2, 1
143 /// println!("{}", top);
149 /// The `Vec` type allows to access values by index, because it implements the
150 /// [`Index`] trait. An example will be more explicit:
153 /// let v = vec![0, 2, 4, 6];
154 /// println!("{}", v[1]); // it will display '2'
157 /// However be careful: if you try to access an index which isn't in the `Vec`,
158 /// your software will panic! You cannot do this:
161 /// let v = vec![0, 2, 4, 6];
162 /// println!("{}", v[6]); // it will panic!
165 /// In conclusion: always check if the index you want to get really exists
170 /// A `Vec` can be mutable. Slices, on the other hand, are read-only objects.
171 /// To get a slice, use `&`. Example:
174 /// fn read_slice(slice: &[usize]) {
178 /// let v = vec![0, 1];
181 /// // ... and that's all!
182 /// // you can also do it like this:
183 /// let x : &[usize] = &v;
186 /// In Rust, it's more common to pass slices as arguments rather than vectors
187 /// when you just want to provide a read access. The same goes for [`String`] and
190 /// # Capacity and reallocation
192 /// The capacity of a vector is the amount of space allocated for any future
193 /// elements that will be added onto the vector. This is not to be confused with
194 /// the *length* of a vector, which specifies the number of actual elements
195 /// within the vector. If a vector's length exceeds its capacity, its capacity
196 /// will automatically be increased, but its elements will have to be
199 /// For example, a vector with capacity 10 and length 0 would be an empty vector
200 /// with space for 10 more elements. Pushing 10 or fewer elements onto the
201 /// vector will not change its capacity or cause reallocation to occur. However,
202 /// if the vector's length is increased to 11, it will have to reallocate, which
203 /// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`]
204 /// whenever possible to specify how big the vector is expected to get.
208 /// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees
209 /// about its design. This ensures that it's as low-overhead as possible in
210 /// the general case, and can be correctly manipulated in primitive ways
211 /// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`.
212 /// If additional type parameters are added (e.g. to support custom allocators),
213 /// overriding their defaults may change the behavior.
215 /// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length)
216 /// triplet. No more, no less. The order of these fields is completely
217 /// unspecified, and you should use the appropriate methods to modify these.
218 /// The pointer will never be null, so this type is null-pointer-optimized.
220 /// However, the pointer may not actually point to allocated memory. In particular,
221 /// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`],
222 /// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`]
223 /// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized
224 /// types inside a `Vec`, it will not allocate space for them. *Note that in this case
225 /// the `Vec` may not report a [`capacity`] of 0*. `Vec` will allocate if and only
226 /// if [`mem::size_of::<T>`]`() * capacity() > 0`. In general, `Vec`'s allocation
227 /// details are very subtle — if you intend to allocate memory using a `Vec`
228 /// and use it for something else (either to pass to unsafe code, or to build your
229 /// own memory-backed collection), be sure to deallocate this memory by using
230 /// `from_raw_parts` to recover the `Vec` and then dropping it.
232 /// If a `Vec` *has* allocated memory, then the memory it points to is on the heap
233 /// (as defined by the allocator Rust is configured to use by default), and its
234 /// pointer points to [`len`] initialized, contiguous elements in order (what
235 /// you would see if you coerced it to a slice), followed by [`capacity`]` -
236 /// `[`len`] logically uninitialized, contiguous elements.
238 /// `Vec` will never perform a "small optimization" where elements are actually
239 /// stored on the stack for two reasons:
241 /// * It would make it more difficult for unsafe code to correctly manipulate
242 /// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were
243 /// only moved, and it would be more difficult to determine if a `Vec` had
244 /// actually allocated memory.
246 /// * It would penalize the general case, incurring an additional branch
249 /// `Vec` will never automatically shrink itself, even if completely empty. This
250 /// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec`
251 /// and then filling it back up to the same [`len`] should incur no calls to
252 /// the allocator. If you wish to free up unused memory, use
253 /// [`shrink_to_fit`][`shrink_to_fit`].
255 /// [`push`] and [`insert`] will never (re)allocate if the reported capacity is
256 /// sufficient. [`push`] and [`insert`] *will* (re)allocate if
257 /// [`len`]` == `[`capacity`]. That is, the reported capacity is completely
258 /// accurate, and can be relied on. It can even be used to manually free the memory
259 /// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even
260 /// when not necessary.
262 /// `Vec` does not guarantee any particular growth strategy when reallocating
263 /// when full, nor when [`reserve`] is called. The current strategy is basic
264 /// and it may prove desirable to use a non-constant growth factor. Whatever
265 /// strategy is used will of course guarantee `O(1)` amortized [`push`].
267 /// `vec![x; n]`, `vec![a, b, c, d]`, and
268 /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
269 /// with exactly the requested capacity. If [`len`]` == `[`capacity`],
270 /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
271 /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
273 /// `Vec` will not specifically overwrite any data that is removed from it,
274 /// but also won't specifically preserve it. Its uninitialized memory is
275 /// scratch space that it may use however it wants. It will generally just do
276 /// whatever is most efficient or otherwise easy to implement. Do not rely on
277 /// removed data to be erased for security purposes. Even if you drop a `Vec`, its
278 /// buffer may simply be reused by another `Vec`. Even if you zero a `Vec`'s memory
279 /// first, that may not actually happen because the optimizer does not consider
280 /// this a side-effect that must be preserved. There is one case which we will
281 /// not break, however: using `unsafe` code to write to the excess capacity,
282 /// and then increasing the length to match, is always valid.
284 /// `Vec` does not currently guarantee the order in which elements are dropped.
285 /// The order has changed in the past and may change again.
287 /// [`vec!`]: ../../std/macro.vec.html
288 /// [`Index`]: ../../std/ops/trait.Index.html
289 /// [`String`]: ../../std/string/struct.String.html
290 /// [`&str`]: ../../std/primitive.str.html
291 /// [`Vec::with_capacity`]: ../../std/vec/struct.Vec.html#method.with_capacity
292 /// [`Vec::new`]: ../../std/vec/struct.Vec.html#method.new
293 /// [`shrink_to_fit`]: ../../std/vec/struct.Vec.html#method.shrink_to_fit
294 /// [`capacity`]: ../../std/vec/struct.Vec.html#method.capacity
295 /// [`mem::size_of::<T>`]: ../../std/mem/fn.size_of.html
296 /// [`len`]: ../../std/vec/struct.Vec.html#method.len
297 /// [`push`]: ../../std/vec/struct.Vec.html#method.push
298 /// [`insert`]: ../../std/vec/struct.Vec.html#method.insert
299 /// [`reserve`]: ../../std/vec/struct.Vec.html#method.reserve
300 /// [owned slice]: ../../std/boxed/struct.Box.html
301 #[stable(feature = "rust1", since = "1.0.0")]
307 ////////////////////////////////////////////////////////////////////////////////
309 ////////////////////////////////////////////////////////////////////////////////
312 /// Constructs a new, empty `Vec<T>`.
314 /// The vector will not allocate until elements are pushed onto it.
319 /// # #![allow(unused_mut)]
320 /// let mut vec: Vec<i32> = Vec::new();
323 #[stable(feature = "rust1", since = "1.0.0")]
324 pub fn new() -> Vec<T> {
331 /// Constructs a new, empty `Vec<T>` with the specified capacity.
333 /// The vector will be able to hold exactly `capacity` elements without
334 /// reallocating. If `capacity` is 0, the vector will not allocate.
336 /// It is important to note that this function does not specify the *length*
337 /// of the returned vector, but only the *capacity*. For an explanation of
338 /// the difference between length and capacity, see *[Capacity and reallocation]*.
340 /// [Capacity and reallocation]: #capacity-and-reallocation
345 /// let mut vec = Vec::with_capacity(10);
347 /// // The vector contains no items, even though it has capacity for more
348 /// assert_eq!(vec.len(), 0);
350 /// // These are all done without reallocating...
355 /// // ...but this may make the vector reallocate
359 #[stable(feature = "rust1", since = "1.0.0")]
360 pub fn with_capacity(capacity: usize) -> Vec<T> {
362 buf: RawVec::with_capacity(capacity),
367 /// Creates a `Vec<T>` directly from the raw components of another vector.
371 /// This is highly unsafe, due to the number of invariants that aren't
374 /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
375 /// (at least, it's highly likely to be incorrect if it wasn't).
376 /// * `ptr`'s `T` needs to have the same size and alignment as it was allocated with.
377 /// * `length` needs to be less than or equal to `capacity`.
378 /// * `capacity` needs to be the capacity that the pointer was allocated with.
380 /// Violating these may cause problems like corrupting the allocator's
381 /// internal data structures. For example it is **not** safe
382 /// to build a `Vec<u8>` from a pointer to a C `char` array and a `size_t`.
384 /// The ownership of `ptr` is effectively transferred to the
385 /// `Vec<T>` which may then deallocate, reallocate or change the
386 /// contents of memory pointed to by the pointer at will. Ensure
387 /// that nothing else uses the pointer after calling this
390 /// [`String`]: ../../std/string/struct.String.html
399 /// let mut v = vec![1, 2, 3];
401 /// // Pull out the various important pieces of information about `v`
402 /// let p = v.as_mut_ptr();
403 /// let len = v.len();
404 /// let cap = v.capacity();
407 /// // Cast `v` into the void: no destructor run, so we are in
408 /// // complete control of the allocation to which `p` points.
411 /// // Overwrite memory with 4, 5, 6
412 /// for i in 0..len as isize {
413 /// ptr::write(p.offset(i), 4 + i);
416 /// // Put everything back together into a Vec
417 /// let rebuilt = Vec::from_raw_parts(p, len, cap);
418 /// assert_eq!(rebuilt, [4, 5, 6]);
422 #[stable(feature = "rust1", since = "1.0.0")]
423 pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T> {
425 buf: RawVec::from_raw_parts(ptr, capacity),
430 /// Returns the number of elements the vector can hold without
436 /// let vec: Vec<i32> = Vec::with_capacity(10);
437 /// assert_eq!(vec.capacity(), 10);
440 #[stable(feature = "rust1", since = "1.0.0")]
441 pub fn capacity(&self) -> usize {
445 /// Reserves capacity for at least `additional` more elements to be inserted
446 /// in the given `Vec<T>`. The collection may reserve more space to avoid
447 /// frequent reallocations. After calling `reserve`, capacity will be
448 /// greater than or equal to `self.len() + additional`. Does nothing if
449 /// capacity is already sufficient.
453 /// Panics if the new capacity overflows `usize`.
458 /// let mut vec = vec![1];
460 /// assert!(vec.capacity() >= 11);
462 #[stable(feature = "rust1", since = "1.0.0")]
463 pub fn reserve(&mut self, additional: usize) {
464 self.buf.reserve(self.len, additional);
467 /// Reserves the minimum capacity for exactly `additional` more elements to
468 /// be inserted in the given `Vec<T>`. After calling `reserve_exact`,
469 /// capacity will be greater than or equal to `self.len() + additional`.
470 /// Does nothing if the capacity is already sufficient.
472 /// Note that the allocator may give the collection more space than it
473 /// requests. Therefore capacity can not be relied upon to be precisely
474 /// minimal. Prefer `reserve` if future insertions are expected.
478 /// Panics if the new capacity overflows `usize`.
483 /// let mut vec = vec![1];
484 /// vec.reserve_exact(10);
485 /// assert!(vec.capacity() >= 11);
487 #[stable(feature = "rust1", since = "1.0.0")]
488 pub fn reserve_exact(&mut self, additional: usize) {
489 self.buf.reserve_exact(self.len, additional);
492 /// Shrinks the capacity of the vector as much as possible.
494 /// It will drop down as close as possible to the length but the allocator
495 /// may still inform the vector that there is space for a few more elements.
500 /// let mut vec = Vec::with_capacity(10);
501 /// vec.extend([1, 2, 3].iter().cloned());
502 /// assert_eq!(vec.capacity(), 10);
503 /// vec.shrink_to_fit();
504 /// assert!(vec.capacity() >= 3);
506 #[stable(feature = "rust1", since = "1.0.0")]
507 pub fn shrink_to_fit(&mut self) {
508 self.buf.shrink_to_fit(self.len);
511 /// Converts the vector into [`Box<[T]>`][owned slice].
513 /// Note that this will drop any excess capacity.
515 /// [owned slice]: ../../std/boxed/struct.Box.html
520 /// let v = vec![1, 2, 3];
522 /// let slice = v.into_boxed_slice();
525 /// Any excess capacity is removed:
528 /// let mut vec = Vec::with_capacity(10);
529 /// vec.extend([1, 2, 3].iter().cloned());
531 /// assert_eq!(vec.capacity(), 10);
532 /// let slice = vec.into_boxed_slice();
533 /// assert_eq!(slice.into_vec().capacity(), 3);
535 #[stable(feature = "rust1", since = "1.0.0")]
536 pub fn into_boxed_slice(mut self) -> Box<[T]> {
538 self.shrink_to_fit();
539 let buf = ptr::read(&self.buf);
545 /// Shortens the vector, keeping the first `len` elements and dropping
548 /// If `len` is greater than the vector's current length, this has no
551 /// The [`drain`] method can emulate `truncate`, but causes the excess
552 /// elements to be returned instead of dropped.
554 /// Note that this method has no effect on the allocated capacity
559 /// Truncating a five element vector to two elements:
562 /// let mut vec = vec![1, 2, 3, 4, 5];
564 /// assert_eq!(vec, [1, 2]);
567 /// No truncation occurs when `len` is greater than the vector's current
571 /// let mut vec = vec![1, 2, 3];
573 /// assert_eq!(vec, [1, 2, 3]);
576 /// Truncating when `len == 0` is equivalent to calling the [`clear`]
580 /// let mut vec = vec![1, 2, 3];
582 /// assert_eq!(vec, []);
585 /// [`clear`]: #method.clear
586 /// [`drain`]: #method.drain
587 #[stable(feature = "rust1", since = "1.0.0")]
588 pub fn truncate(&mut self, len: usize) {
590 // drop any extra elements
591 while len < self.len {
592 // decrement len before the drop_in_place(), so a panic on Drop
593 // doesn't re-drop the just-failed value.
596 ptr::drop_in_place(self.get_unchecked_mut(len));
601 /// Extracts a slice containing the entire vector.
603 /// Equivalent to `&s[..]`.
608 /// use std::io::{self, Write};
609 /// let buffer = vec![1, 2, 3, 5, 8];
610 /// io::sink().write(buffer.as_slice()).unwrap();
613 #[stable(feature = "vec_as_slice", since = "1.7.0")]
614 pub fn as_slice(&self) -> &[T] {
618 /// Extracts a mutable slice of the entire vector.
620 /// Equivalent to `&mut s[..]`.
625 /// use std::io::{self, Read};
626 /// let mut buffer = vec![0; 3];
627 /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();
630 #[stable(feature = "vec_as_slice", since = "1.7.0")]
631 pub fn as_mut_slice(&mut self) -> &mut [T] {
635 /// Sets the length of a vector.
637 /// This will explicitly set the size of the vector, without actually
638 /// modifying its buffers, so it is up to the caller to ensure that the
639 /// vector is actually the specified size.
646 /// let mut vec = vec!['r', 'u', 's', 't'];
649 /// ptr::drop_in_place(&mut vec[3]);
652 /// assert_eq!(vec, ['r', 'u', 's']);
655 /// In this example, there is a memory leak since the memory locations
656 /// owned by the inner vectors were not freed prior to the `set_len` call:
659 /// let mut vec = vec![vec![1, 0, 0],
667 /// In this example, the vector gets expanded from zero to four items
668 /// without any memory allocations occurring, resulting in vector
669 /// values of unallocated memory:
672 /// let mut vec: Vec<char> = Vec::new();
679 #[stable(feature = "rust1", since = "1.0.0")]
680 pub unsafe fn set_len(&mut self, len: usize) {
684 /// Removes an element from the vector and returns it.
686 /// The removed element is replaced by the last element of the vector.
688 /// This does not preserve ordering, but is O(1).
692 /// Panics if `index` is out of bounds.
697 /// let mut v = vec!["foo", "bar", "baz", "qux"];
699 /// assert_eq!(v.swap_remove(1), "bar");
700 /// assert_eq!(v, ["foo", "qux", "baz"]);
702 /// assert_eq!(v.swap_remove(0), "foo");
703 /// assert_eq!(v, ["baz", "qux"]);
706 #[stable(feature = "rust1", since = "1.0.0")]
707 pub fn swap_remove(&mut self, index: usize) -> T {
708 let length = self.len();
709 self.swap(index, length - 1);
713 /// Inserts an element at position `index` within the vector, shifting all
714 /// elements after it to the right.
718 /// Panics if `index > len`.
723 /// let mut vec = vec![1, 2, 3];
724 /// vec.insert(1, 4);
725 /// assert_eq!(vec, [1, 4, 2, 3]);
726 /// vec.insert(4, 5);
727 /// assert_eq!(vec, [1, 4, 2, 3, 5]);
729 #[stable(feature = "rust1", since = "1.0.0")]
730 pub fn insert(&mut self, index: usize, element: T) {
731 let len = self.len();
732 assert!(index <= len);
734 // space for the new element
735 if len == self.buf.cap() {
741 // The spot to put the new value
743 let p = self.as_mut_ptr().offset(index as isize);
744 // Shift everything over to make space. (Duplicating the
745 // `index`th element into two consecutive places.)
746 ptr::copy(p, p.offset(1), len - index);
747 // Write it in, overwriting the first copy of the `index`th
749 ptr::write(p, element);
751 self.set_len(len + 1);
755 /// Removes and returns the element at position `index` within the vector,
756 /// shifting all elements after it to the left.
760 /// Panics if `index` is out of bounds.
765 /// let mut v = vec![1, 2, 3];
766 /// assert_eq!(v.remove(1), 2);
767 /// assert_eq!(v, [1, 3]);
769 #[stable(feature = "rust1", since = "1.0.0")]
770 pub fn remove(&mut self, index: usize) -> T {
771 let len = self.len();
772 assert!(index < len);
777 // the place we are taking from.
778 let ptr = self.as_mut_ptr().offset(index as isize);
779 // copy it out, unsafely having a copy of the value on
780 // the stack and in the vector at the same time.
781 ret = ptr::read(ptr);
783 // Shift everything down to fill in that spot.
784 ptr::copy(ptr.offset(1), ptr, len - index - 1);
786 self.set_len(len - 1);
791 /// Retains only the elements specified by the predicate.
793 /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
794 /// This method operates in place and preserves the order of the retained
800 /// let mut vec = vec![1, 2, 3, 4];
801 /// vec.retain(|&x| x%2 == 0);
802 /// assert_eq!(vec, [2, 4]);
804 #[stable(feature = "rust1", since = "1.0.0")]
805 pub fn retain<F>(&mut self, mut f: F)
806 where F: FnMut(&T) -> bool
808 self.drain_filter(|x| !f(x));
811 /// Removes all but the first of consecutive elements in the vector that resolve to the same
814 /// If the vector is sorted, this removes all duplicates.
819 /// let mut vec = vec![10, 20, 21, 30, 20];
821 /// vec.dedup_by_key(|i| *i / 10);
823 /// assert_eq!(vec, [10, 20, 30, 20]);
825 #[stable(feature = "dedup_by", since = "1.16.0")]
827 pub fn dedup_by_key<F, K>(&mut self, mut key: F) where F: FnMut(&mut T) -> K, K: PartialEq {
828 self.dedup_by(|a, b| key(a) == key(b))
831 /// Removes all but the first of consecutive elements in the vector satisfying a given equality
834 /// The `same_bucket` function is passed references to two elements from the vector, and
835 /// returns `true` if the elements compare equal, or `false` if they do not. The elements are
836 /// passed in opposite order from their order in the vector, so if `same_bucket(a, b)` returns
837 /// `true`, `a` is removed.
839 /// If the vector is sorted, this removes all duplicates.
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 /// Returns a place for insertion at the back of the `Vec`.
967 /// Using this method with placement syntax is equivalent to [`push`](#method.push),
968 /// but may be more efficient.
973 /// #![feature(collection_placement)]
974 /// #![feature(placement_in_syntax)]
976 /// let mut vec = vec![1, 2];
977 /// vec.place_back() <- 3;
978 /// vec.place_back() <- 4;
979 /// assert_eq!(&vec, &[1, 2, 3, 4]);
981 #[unstable(feature = "collection_placement",
982 reason = "placement protocol is subject to change",
984 pub fn place_back(&mut self) -> PlaceBack<T> {
985 PlaceBack { vec: self }
988 /// Removes the last element from a vector and returns it, or [`None`] if it
991 /// [`None`]: ../../std/option/enum.Option.html#variant.None
996 /// let mut vec = vec![1, 2, 3];
997 /// assert_eq!(vec.pop(), Some(3));
998 /// assert_eq!(vec, [1, 2]);
1001 #[stable(feature = "rust1", since = "1.0.0")]
1002 pub fn pop(&mut self) -> Option<T> {
1008 Some(ptr::read(self.get_unchecked(self.len())))
1013 /// Moves all the elements of `other` into `Self`, leaving `other` empty.
1017 /// Panics if the number of elements in the vector overflows a `usize`.
1022 /// let mut vec = vec![1, 2, 3];
1023 /// let mut vec2 = vec![4, 5, 6];
1024 /// vec.append(&mut vec2);
1025 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
1026 /// assert_eq!(vec2, []);
1029 #[stable(feature = "append", since = "1.4.0")]
1030 pub fn append(&mut self, other: &mut Self) {
1032 self.append_elements(other.as_slice() as _);
1037 /// Appends elements to `Self` from other buffer.
1039 unsafe fn append_elements(&mut self, other: *const [T]) {
1040 let count = (*other).len();
1041 self.reserve(count);
1042 let len = self.len();
1043 ptr::copy_nonoverlapping(other as *const T, self.get_unchecked_mut(len), count);
1047 /// Creates a draining iterator that removes the specified range in the vector
1048 /// and yields the removed items.
1050 /// Note 1: The element range is removed even if the iterator is only
1051 /// partially consumed or not consumed at all.
1053 /// Note 2: It is unspecified how many elements are removed from the vector
1054 /// if the `Drain` value is leaked.
1058 /// Panics if the starting point is greater than the end point or if
1059 /// the end point is greater than the length of the vector.
1064 /// let mut v = vec![1, 2, 3];
1065 /// let u: Vec<_> = v.drain(1..).collect();
1066 /// assert_eq!(v, &[1]);
1067 /// assert_eq!(u, &[2, 3]);
1069 /// // A full range clears the vector
1071 /// assert_eq!(v, &[]);
1073 #[stable(feature = "drain", since = "1.6.0")]
1074 pub fn drain<R>(&mut self, range: R) -> Drain<T>
1075 where R: RangeArgument<usize>
1079 // When the Drain is first created, it shortens the length of
1080 // the source vector to make sure no uninitialized or moved-from elements
1081 // are accessible at all if the Drain's destructor never gets to run.
1083 // Drain will ptr::read out the values to remove.
1084 // When finished, remaining tail of the vec is copied back to cover
1085 // the hole, and the vector length is restored to the new length.
1087 let len = self.len();
1088 let start = match range.start() {
1090 Excluded(&n) => n + 1,
1093 let end = match range.end() {
1094 Included(&n) => n + 1,
1098 assert!(start <= end);
1099 assert!(end <= len);
1102 // set self.vec length's to start, to be safe in case Drain is leaked
1103 self.set_len(start);
1104 // Use the borrow in the IterMut to indicate borrowing behavior of the
1105 // whole Drain iterator (like &mut T).
1106 let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().offset(start as isize),
1110 tail_len: len - end,
1111 iter: range_slice.iter(),
1112 vec: NonNull::from(self),
1117 /// Clears the vector, removing all values.
1119 /// Note that this method has no effect on the allocated capacity
1125 /// let mut v = vec![1, 2, 3];
1129 /// assert!(v.is_empty());
1132 #[stable(feature = "rust1", since = "1.0.0")]
1133 pub fn clear(&mut self) {
1137 /// Returns the number of elements in the vector, also referred to
1138 /// as its 'length'.
1143 /// let a = vec![1, 2, 3];
1144 /// assert_eq!(a.len(), 3);
1147 #[stable(feature = "rust1", since = "1.0.0")]
1148 pub fn len(&self) -> usize {
1152 /// Returns `true` if the vector contains no elements.
1157 /// let mut v = Vec::new();
1158 /// assert!(v.is_empty());
1161 /// assert!(!v.is_empty());
1163 #[stable(feature = "rust1", since = "1.0.0")]
1164 pub fn is_empty(&self) -> bool {
1168 /// Splits the collection into two at the given index.
1170 /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`,
1171 /// and the returned `Self` contains elements `[at, len)`.
1173 /// Note that the capacity of `self` does not change.
1177 /// Panics if `at > len`.
1182 /// let mut vec = vec![1,2,3];
1183 /// let vec2 = vec.split_off(1);
1184 /// assert_eq!(vec, [1]);
1185 /// assert_eq!(vec2, [2, 3]);
1188 #[stable(feature = "split_off", since = "1.4.0")]
1189 pub fn split_off(&mut self, at: usize) -> Self {
1190 assert!(at <= self.len(), "`at` out of bounds");
1192 let other_len = self.len - at;
1193 let mut other = Vec::with_capacity(other_len);
1195 // Unsafely `set_len` and copy items to `other`.
1198 other.set_len(other_len);
1200 ptr::copy_nonoverlapping(self.as_ptr().offset(at as isize),
1208 impl<T: Clone> Vec<T> {
1209 /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
1211 /// If `new_len` is greater than `len`, the `Vec` is extended by the
1212 /// difference, with each additional slot filled with `value`.
1213 /// If `new_len` is less than `len`, the `Vec` is simply truncated.
1215 /// This method requires `Clone` to clone the passed value. If you'd
1216 /// rather create a value with `Default` instead, see [`resize_default`].
1221 /// let mut vec = vec!["hello"];
1222 /// vec.resize(3, "world");
1223 /// assert_eq!(vec, ["hello", "world", "world"]);
1225 /// let mut vec = vec![1, 2, 3, 4];
1226 /// vec.resize(2, 0);
1227 /// assert_eq!(vec, [1, 2]);
1230 /// [`resize_default`]: #method.resize_default
1231 #[stable(feature = "vec_resize", since = "1.5.0")]
1232 pub fn resize(&mut self, new_len: usize, value: T) {
1233 let len = self.len();
1236 self.extend_with(new_len - len, ExtendElement(value))
1238 self.truncate(new_len);
1242 /// Clones and appends all elements in a slice to the `Vec`.
1244 /// Iterates over the slice `other`, clones each element, and then appends
1245 /// it to this `Vec`. The `other` vector is traversed in-order.
1247 /// Note that this function is same as `extend` except that it is
1248 /// specialized to work with slices instead. If and when Rust gets
1249 /// specialization this function will likely be deprecated (but still
1255 /// let mut vec = vec![1];
1256 /// vec.extend_from_slice(&[2, 3, 4]);
1257 /// assert_eq!(vec, [1, 2, 3, 4]);
1259 #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
1260 pub fn extend_from_slice(&mut self, other: &[T]) {
1261 self.spec_extend(other.iter())
1265 impl<T: Default> Vec<T> {
1266 /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
1268 /// If `new_len` is greater than `len`, the `Vec` is extended by the
1269 /// difference, with each additional slot filled with `Default::default()`.
1270 /// If `new_len` is less than `len`, the `Vec` is simply truncated.
1272 /// This method uses `Default` to create new values on every push. If
1273 /// you'd rather `Clone` a given value, use [`resize`].
1279 /// #![feature(vec_resize_default)]
1281 /// let mut vec = vec![1, 2, 3];
1282 /// vec.resize_default(5);
1283 /// assert_eq!(vec, [1, 2, 3, 0, 0]);
1285 /// let mut vec = vec![1, 2, 3, 4];
1286 /// vec.resize_default(2);
1287 /// assert_eq!(vec, [1, 2]);
1290 /// [`resize`]: #method.resize
1291 #[unstable(feature = "vec_resize_default", issue = "41758")]
1292 pub fn resize_default(&mut self, new_len: usize) {
1293 let len = self.len();
1296 self.extend_with(new_len - len, ExtendDefault);
1298 self.truncate(new_len);
1303 // This code generalises `extend_with_{element,default}`.
1304 trait ExtendWith<T> {
1305 fn next(&self) -> T;
1309 struct ExtendElement<T>(T);
1310 impl<T: Clone> ExtendWith<T> for ExtendElement<T> {
1311 fn next(&self) -> T { self.0.clone() }
1312 fn last(self) -> T { self.0 }
1315 struct ExtendDefault;
1316 impl<T: Default> ExtendWith<T> for ExtendDefault {
1317 fn next(&self) -> T { Default::default() }
1318 fn last(self) -> T { Default::default() }
1321 /// Extend the vector by `n` values, using the given generator.
1322 fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, value: E) {
1326 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1327 // Use SetLenOnDrop to work around bug where compiler
1328 // may not realize the store through `ptr` through self.set_len()
1330 let mut local_len = SetLenOnDrop::new(&mut self.len);
1332 // Write all elements except the last one
1334 ptr::write(ptr, value.next());
1335 ptr = ptr.offset(1);
1336 // Increment the length in every step in case next() panics
1337 local_len.increment_len(1);
1341 // We can write the last element directly without cloning needlessly
1342 ptr::write(ptr, value.last());
1343 local_len.increment_len(1);
1346 // len set by scope guard
1351 // Set the length of the vec when the `SetLenOnDrop` value goes out of scope.
1353 // The idea is: The length field in SetLenOnDrop is a local variable
1354 // that the optimizer will see does not alias with any stores through the Vec's data
1355 // pointer. This is a workaround for alias analysis issue #32155
1356 struct SetLenOnDrop<'a> {
1361 impl<'a> SetLenOnDrop<'a> {
1363 fn new(len: &'a mut usize) -> Self {
1364 SetLenOnDrop { local_len: *len, len: len }
1368 fn increment_len(&mut self, increment: usize) {
1369 self.local_len += increment;
1373 impl<'a> Drop for SetLenOnDrop<'a> {
1375 fn drop(&mut self) {
1376 *self.len = self.local_len;
1380 impl<T: PartialEq> Vec<T> {
1381 /// Removes consecutive repeated elements in the vector.
1383 /// If the vector is sorted, this removes all duplicates.
1388 /// let mut vec = vec![1, 2, 2, 3, 2];
1392 /// assert_eq!(vec, [1, 2, 3, 2]);
1394 #[stable(feature = "rust1", since = "1.0.0")]
1396 pub fn dedup(&mut self) {
1397 self.dedup_by(|a, b| a == b)
1400 /// Removes the first instance of `item` from the vector if the item exists.
1405 /// # #![feature(vec_remove_item)]
1406 /// let mut vec = vec![1, 2, 3, 1];
1408 /// vec.remove_item(&1);
1410 /// assert_eq!(vec, vec![2, 3, 1]);
1412 #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")]
1413 pub fn remove_item(&mut self, item: &T) -> Option<T> {
1414 let pos = self.iter().position(|x| *x == *item)?;
1415 Some(self.remove(pos))
1419 ////////////////////////////////////////////////////////////////////////////////
1420 // Internal methods and functions
1421 ////////////////////////////////////////////////////////////////////////////////
1424 #[stable(feature = "rust1", since = "1.0.0")]
1425 pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
1426 <T as SpecFromElem>::from_elem(elem, n)
1429 // Specialization trait used for Vec::from_elem
1430 trait SpecFromElem: Sized {
1431 fn from_elem(elem: Self, n: usize) -> Vec<Self>;
1434 impl<T: Clone> SpecFromElem for T {
1435 default fn from_elem(elem: Self, n: usize) -> Vec<Self> {
1436 let mut v = Vec::with_capacity(n);
1437 v.extend_with(n, ExtendElement(elem));
1442 impl SpecFromElem for u8 {
1444 fn from_elem(elem: u8, n: usize) -> Vec<u8> {
1447 buf: RawVec::with_capacity_zeroed(n),
1452 let mut v = Vec::with_capacity(n);
1453 ptr::write_bytes(v.as_mut_ptr(), elem, n);
1460 macro_rules! impl_spec_from_elem {
1461 ($t: ty, $is_zero: expr) => {
1462 impl SpecFromElem for $t {
1464 fn from_elem(elem: $t, n: usize) -> Vec<$t> {
1467 buf: RawVec::with_capacity_zeroed(n),
1471 let mut v = Vec::with_capacity(n);
1472 v.extend_with(n, ExtendElement(elem));
1479 impl_spec_from_elem!(i8, |x| x == 0);
1480 impl_spec_from_elem!(i16, |x| x == 0);
1481 impl_spec_from_elem!(i32, |x| x == 0);
1482 impl_spec_from_elem!(i64, |x| x == 0);
1483 impl_spec_from_elem!(i128, |x| x == 0);
1484 impl_spec_from_elem!(isize, |x| x == 0);
1486 impl_spec_from_elem!(u16, |x| x == 0);
1487 impl_spec_from_elem!(u32, |x| x == 0);
1488 impl_spec_from_elem!(u64, |x| x == 0);
1489 impl_spec_from_elem!(u128, |x| x == 0);
1490 impl_spec_from_elem!(usize, |x| x == 0);
1492 impl_spec_from_elem!(f32, |x: f32| x == 0. && x.is_sign_positive());
1493 impl_spec_from_elem!(f64, |x: f64| x == 0. && x.is_sign_positive());
1495 ////////////////////////////////////////////////////////////////////////////////
1496 // Common trait implementations for Vec
1497 ////////////////////////////////////////////////////////////////////////////////
1499 #[stable(feature = "rust1", since = "1.0.0")]
1500 impl<T: Clone> Clone for Vec<T> {
1502 fn clone(&self) -> Vec<T> {
1503 <[T]>::to_vec(&**self)
1506 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
1507 // required for this method definition, is not available. Instead use the
1508 // `slice::to_vec` function which is only available with cfg(test)
1509 // NB see the slice::hack module in slice.rs for more information
1511 fn clone(&self) -> Vec<T> {
1512 ::slice::to_vec(&**self)
1515 fn clone_from(&mut self, other: &Vec<T>) {
1516 other.as_slice().clone_into(self);
1520 #[stable(feature = "rust1", since = "1.0.0")]
1521 impl<T: Hash> Hash for Vec<T> {
1523 fn hash<H: hash::Hasher>(&self, state: &mut H) {
1524 Hash::hash(&**self, state)
1528 #[stable(feature = "rust1", since = "1.0.0")]
1529 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1530 impl<T> Index<usize> for Vec<T> {
1534 fn index(&self, index: usize) -> &T {
1535 // NB built-in indexing via `&[T]`
1540 #[stable(feature = "rust1", since = "1.0.0")]
1541 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1542 impl<T> IndexMut<usize> for Vec<T> {
1544 fn index_mut(&mut self, index: usize) -> &mut T {
1545 // NB built-in indexing via `&mut [T]`
1546 &mut (**self)[index]
1550 #[stable(feature = "rust1", since = "1.0.0")]
1551 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1552 impl<T> ops::Index<ops::Range<usize>> for Vec<T> {
1556 fn index(&self, index: ops::Range<usize>) -> &[T] {
1557 Index::index(&**self, index)
1561 #[stable(feature = "rust1", since = "1.0.0")]
1562 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1563 impl<T> ops::Index<ops::RangeTo<usize>> for Vec<T> {
1567 fn index(&self, index: ops::RangeTo<usize>) -> &[T] {
1568 Index::index(&**self, index)
1572 #[stable(feature = "rust1", since = "1.0.0")]
1573 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1574 impl<T> ops::Index<ops::RangeFrom<usize>> for Vec<T> {
1578 fn index(&self, index: ops::RangeFrom<usize>) -> &[T] {
1579 Index::index(&**self, index)
1583 #[stable(feature = "rust1", since = "1.0.0")]
1584 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1585 impl<T> ops::Index<ops::RangeFull> for Vec<T> {
1589 fn index(&self, _index: ops::RangeFull) -> &[T] {
1594 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1595 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1596 impl<T> ops::Index<ops::RangeInclusive<usize>> for Vec<T> {
1600 fn index(&self, index: ops::RangeInclusive<usize>) -> &[T] {
1601 Index::index(&**self, index)
1605 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1606 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1607 impl<T> ops::Index<ops::RangeToInclusive<usize>> for Vec<T> {
1611 fn index(&self, index: ops::RangeToInclusive<usize>) -> &[T] {
1612 Index::index(&**self, index)
1616 #[stable(feature = "rust1", since = "1.0.0")]
1617 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1618 impl<T> ops::IndexMut<ops::Range<usize>> for Vec<T> {
1620 fn index_mut(&mut self, index: ops::Range<usize>) -> &mut [T] {
1621 IndexMut::index_mut(&mut **self, index)
1625 #[stable(feature = "rust1", since = "1.0.0")]
1626 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1627 impl<T> ops::IndexMut<ops::RangeTo<usize>> for Vec<T> {
1629 fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut [T] {
1630 IndexMut::index_mut(&mut **self, index)
1634 #[stable(feature = "rust1", since = "1.0.0")]
1635 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1636 impl<T> ops::IndexMut<ops::RangeFrom<usize>> for Vec<T> {
1638 fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut [T] {
1639 IndexMut::index_mut(&mut **self, index)
1643 #[stable(feature = "rust1", since = "1.0.0")]
1644 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1645 impl<T> ops::IndexMut<ops::RangeFull> for Vec<T> {
1647 fn index_mut(&mut self, _index: ops::RangeFull) -> &mut [T] {
1652 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1653 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1654 impl<T> ops::IndexMut<ops::RangeInclusive<usize>> for Vec<T> {
1656 fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut [T] {
1657 IndexMut::index_mut(&mut **self, index)
1661 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1662 #[rustc_on_unimplemented = "vector indices are of type `usize` or ranges of `usize`"]
1663 impl<T> ops::IndexMut<ops::RangeToInclusive<usize>> for Vec<T> {
1665 fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut [T] {
1666 IndexMut::index_mut(&mut **self, index)
1670 #[stable(feature = "rust1", since = "1.0.0")]
1671 impl<T> ops::Deref for Vec<T> {
1674 fn deref(&self) -> &[T] {
1676 let p = self.buf.ptr();
1677 assume(!p.is_null());
1678 slice::from_raw_parts(p, self.len)
1683 #[stable(feature = "rust1", since = "1.0.0")]
1684 impl<T> ops::DerefMut for Vec<T> {
1685 fn deref_mut(&mut self) -> &mut [T] {
1687 let ptr = self.buf.ptr();
1688 assume(!ptr.is_null());
1689 slice::from_raw_parts_mut(ptr, self.len)
1694 #[stable(feature = "rust1", since = "1.0.0")]
1695 impl<T> FromIterator<T> for Vec<T> {
1697 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> {
1698 <Self as SpecExtend<T, I::IntoIter>>::from_iter(iter.into_iter())
1702 #[stable(feature = "rust1", since = "1.0.0")]
1703 impl<T> IntoIterator for Vec<T> {
1705 type IntoIter = IntoIter<T>;
1707 /// Creates a consuming iterator, that is, one that moves each value out of
1708 /// the vector (from start to end). The vector cannot be used after calling
1714 /// let v = vec!["a".to_string(), "b".to_string()];
1715 /// for s in v.into_iter() {
1716 /// // s has type String, not &String
1717 /// println!("{}", s);
1721 fn into_iter(mut self) -> IntoIter<T> {
1723 let begin = self.as_mut_ptr();
1724 assume(!begin.is_null());
1725 let end = if mem::size_of::<T>() == 0 {
1726 arith_offset(begin as *const i8, self.len() as isize) as *const T
1728 begin.offset(self.len() as isize) as *const T
1730 let cap = self.buf.cap();
1733 buf: NonNull::new_unchecked(begin),
1734 phantom: PhantomData,
1743 #[stable(feature = "rust1", since = "1.0.0")]
1744 impl<'a, T> IntoIterator for &'a Vec<T> {
1746 type IntoIter = slice::Iter<'a, T>;
1748 fn into_iter(self) -> slice::Iter<'a, T> {
1753 #[stable(feature = "rust1", since = "1.0.0")]
1754 impl<'a, T> IntoIterator for &'a mut Vec<T> {
1755 type Item = &'a mut T;
1756 type IntoIter = slice::IterMut<'a, T>;
1758 fn into_iter(self) -> slice::IterMut<'a, T> {
1763 #[stable(feature = "rust1", since = "1.0.0")]
1764 impl<T> Extend<T> for Vec<T> {
1766 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1767 <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter())
1771 // Specialization trait used for Vec::from_iter and Vec::extend
1772 trait SpecExtend<T, I> {
1773 fn from_iter(iter: I) -> Self;
1774 fn spec_extend(&mut self, iter: I);
1777 impl<T, I> SpecExtend<T, I> for Vec<T>
1778 where I: Iterator<Item=T>,
1780 default fn from_iter(mut iterator: I) -> Self {
1781 // Unroll the first iteration, as the vector is going to be
1782 // expanded on this iteration in every case when the iterable is not
1783 // empty, but the loop in extend_desugared() is not going to see the
1784 // vector being full in the few subsequent loop iterations.
1785 // So we get better branch prediction.
1786 let mut vector = match iterator.next() {
1787 None => return Vec::new(),
1789 let (lower, _) = iterator.size_hint();
1790 let mut vector = Vec::with_capacity(lower.saturating_add(1));
1792 ptr::write(vector.get_unchecked_mut(0), element);
1798 <Vec<T> as SpecExtend<T, I>>::spec_extend(&mut vector, iterator);
1802 default fn spec_extend(&mut self, iter: I) {
1803 self.extend_desugared(iter)
1807 impl<T, I> SpecExtend<T, I> for Vec<T>
1808 where I: TrustedLen<Item=T>,
1810 default fn from_iter(iterator: I) -> Self {
1811 let mut vector = Vec::new();
1812 vector.spec_extend(iterator);
1816 default fn spec_extend(&mut self, iterator: I) {
1817 // This is the case for a TrustedLen iterator.
1818 let (low, high) = iterator.size_hint();
1819 if let Some(high_value) = high {
1820 debug_assert_eq!(low, high_value,
1821 "TrustedLen iterator's size hint is not exact: {:?}",
1824 if let Some(additional) = high {
1825 self.reserve(additional);
1827 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1828 let mut local_len = SetLenOnDrop::new(&mut self.len);
1829 for element in iterator {
1830 ptr::write(ptr, element);
1831 ptr = ptr.offset(1);
1832 // NB can't overflow since we would have had to alloc the address space
1833 local_len.increment_len(1);
1837 self.extend_desugared(iterator)
1842 impl<T> SpecExtend<T, IntoIter<T>> for Vec<T> {
1843 fn from_iter(iterator: IntoIter<T>) -> Self {
1844 // A common case is passing a vector into a function which immediately
1845 // re-collects into a vector. We can short circuit this if the IntoIter
1846 // has not been advanced at all.
1847 if iterator.buf.as_ptr() as *const _ == iterator.ptr {
1849 let vec = Vec::from_raw_parts(iterator.buf.as_ptr(),
1852 mem::forget(iterator);
1856 let mut vector = Vec::new();
1857 vector.spec_extend(iterator);
1862 fn spec_extend(&mut self, mut iterator: IntoIter<T>) {
1864 self.append_elements(iterator.as_slice() as _);
1866 iterator.ptr = iterator.end;
1870 impl<'a, T: 'a, I> SpecExtend<&'a T, I> for Vec<T>
1871 where I: Iterator<Item=&'a T>,
1874 default fn from_iter(iterator: I) -> Self {
1875 SpecExtend::from_iter(iterator.cloned())
1878 default fn spec_extend(&mut self, iterator: I) {
1879 self.spec_extend(iterator.cloned())
1883 impl<'a, T: 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T>
1886 fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
1887 let slice = iterator.as_slice();
1888 self.reserve(slice.len());
1890 let len = self.len();
1891 self.set_len(len + slice.len());
1892 self.get_unchecked_mut(len..).copy_from_slice(slice);
1898 fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
1899 // This is the case for a general iterator.
1901 // This function should be the moral equivalent of:
1903 // for item in iterator {
1906 while let Some(element) = iterator.next() {
1907 let len = self.len();
1908 if len == self.capacity() {
1909 let (lower, _) = iterator.size_hint();
1910 self.reserve(lower.saturating_add(1));
1913 ptr::write(self.get_unchecked_mut(len), element);
1914 // NB can't overflow since we would have had to alloc the address space
1915 self.set_len(len + 1);
1920 /// Creates a splicing iterator that replaces the specified range in the vector
1921 /// with the given `replace_with` iterator and yields the removed items.
1922 /// `replace_with` does not need to be the same length as `range`.
1924 /// Note 1: The element range is removed even if the iterator is not
1925 /// consumed until the end.
1927 /// Note 2: It is unspecified how many elements are removed from the vector,
1928 /// if the `Splice` value is leaked.
1930 /// Note 3: The input iterator `replace_with` is only consumed
1931 /// when the `Splice` value is dropped.
1933 /// Note 4: This is optimal if:
1935 /// * The tail (elements in the vector after `range`) is empty,
1936 /// * or `replace_with` yields fewer elements than `range`’s length
1937 /// * or the lower bound of its `size_hint()` is exact.
1939 /// Otherwise, a temporary vector is allocated and the tail is moved twice.
1943 /// Panics if the starting point is greater than the end point or if
1944 /// the end point is greater than the length of the vector.
1949 /// let mut v = vec![1, 2, 3];
1950 /// let new = [7, 8];
1951 /// let u: Vec<_> = v.splice(..2, new.iter().cloned()).collect();
1952 /// assert_eq!(v, &[7, 8, 3]);
1953 /// assert_eq!(u, &[1, 2]);
1956 #[stable(feature = "vec_splice", since = "1.21.0")]
1957 pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<I::IntoIter>
1958 where R: RangeArgument<usize>, I: IntoIterator<Item=T>
1961 drain: self.drain(range),
1962 replace_with: replace_with.into_iter(),
1966 /// Creates an iterator which uses a closure to determine if an element should be removed.
1968 /// If the closure returns true, then the element is removed and yielded.
1969 /// If the closure returns false, the element will remain in the vector and will not be yielded
1970 /// by the iterator.
1972 /// Using this method is equivalent to the following code:
1975 /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 };
1976 /// # let mut vec = vec![1, 2, 3, 4, 5, 6];
1978 /// while i != vec.len() {
1979 /// if some_predicate(&mut vec[i]) {
1980 /// let val = vec.remove(i);
1981 /// // your code here
1987 /// # assert_eq!(vec, vec![1, 4, 5]);
1990 /// But `drain_filter` is easier to use. `drain_filter` is also more efficient,
1991 /// because it can backshift the elements of the array in bulk.
1993 /// Note that `drain_filter` also lets you mutate every element in the filter closure,
1994 /// regardless of whether you choose to keep or remove it.
1999 /// Splitting an array into evens and odds, reusing the original allocation:
2002 /// #![feature(drain_filter)]
2003 /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];
2005 /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
2006 /// let odds = numbers;
2008 /// assert_eq!(evens, vec![2, 4, 6, 8, 14]);
2009 /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);
2011 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2012 pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<T, F>
2013 where F: FnMut(&mut T) -> bool,
2015 let old_len = self.len();
2017 // Guard against us getting leaked (leak amplification)
2018 unsafe { self.set_len(0); }
2030 /// Extend implementation that copies elements out of references before pushing them onto the Vec.
2032 /// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to
2033 /// append the entire slice at once.
2035 /// [`copy_from_slice`]: ../../std/primitive.slice.html#method.copy_from_slice
2036 #[stable(feature = "extend_ref", since = "1.2.0")]
2037 impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> {
2038 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
2039 self.spec_extend(iter.into_iter())
2043 macro_rules! __impl_slice_eq1 {
2044 ($Lhs: ty, $Rhs: ty) => {
2045 __impl_slice_eq1! { $Lhs, $Rhs, Sized }
2047 ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
2048 #[stable(feature = "rust1", since = "1.0.0")]
2049 impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
2051 fn eq(&self, other: &$Rhs) -> bool { self[..] == other[..] }
2053 fn ne(&self, other: &$Rhs) -> bool { self[..] != other[..] }
2058 __impl_slice_eq1! { Vec<A>, Vec<B> }
2059 __impl_slice_eq1! { Vec<A>, &'b [B] }
2060 __impl_slice_eq1! { Vec<A>, &'b mut [B] }
2061 __impl_slice_eq1! { Cow<'a, [A]>, &'b [B], Clone }
2062 __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B], Clone }
2063 __impl_slice_eq1! { Cow<'a, [A]>, Vec<B>, Clone }
2065 macro_rules! array_impls {
2068 // NOTE: some less important impls are omitted to reduce code bloat
2069 __impl_slice_eq1! { Vec<A>, [B; $N] }
2070 __impl_slice_eq1! { Vec<A>, &'b [B; $N] }
2071 // __impl_slice_eq1! { Vec<A>, &'b mut [B; $N] }
2072 // __impl_slice_eq1! { Cow<'a, [A]>, [B; $N], Clone }
2073 // __impl_slice_eq1! { Cow<'a, [A]>, &'b [B; $N], Clone }
2074 // __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
2081 10 11 12 13 14 15 16 17 18 19
2082 20 21 22 23 24 25 26 27 28 29
2086 /// Implements comparison of vectors, lexicographically.
2087 #[stable(feature = "rust1", since = "1.0.0")]
2088 impl<T: PartialOrd> PartialOrd for Vec<T> {
2090 fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> {
2091 PartialOrd::partial_cmp(&**self, &**other)
2095 #[stable(feature = "rust1", since = "1.0.0")]
2096 impl<T: Eq> Eq for Vec<T> {}
2098 /// Implements ordering of vectors, lexicographically.
2099 #[stable(feature = "rust1", since = "1.0.0")]
2100 impl<T: Ord> Ord for Vec<T> {
2102 fn cmp(&self, other: &Vec<T>) -> Ordering {
2103 Ord::cmp(&**self, &**other)
2107 #[stable(feature = "rust1", since = "1.0.0")]
2108 unsafe impl<#[may_dangle] T> Drop for Vec<T> {
2109 fn drop(&mut self) {
2112 ptr::drop_in_place(&mut self[..]);
2114 // RawVec handles deallocation
2118 #[stable(feature = "rust1", since = "1.0.0")]
2119 impl<T> Default for Vec<T> {
2120 /// Creates an empty `Vec<T>`.
2121 fn default() -> Vec<T> {
2126 #[stable(feature = "rust1", since = "1.0.0")]
2127 impl<T: fmt::Debug> fmt::Debug for Vec<T> {
2128 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2129 fmt::Debug::fmt(&**self, f)
2133 #[stable(feature = "rust1", since = "1.0.0")]
2134 impl<T> AsRef<Vec<T>> for Vec<T> {
2135 fn as_ref(&self) -> &Vec<T> {
2140 #[stable(feature = "vec_as_mut", since = "1.5.0")]
2141 impl<T> AsMut<Vec<T>> for Vec<T> {
2142 fn as_mut(&mut self) -> &mut Vec<T> {
2147 #[stable(feature = "rust1", since = "1.0.0")]
2148 impl<T> AsRef<[T]> for Vec<T> {
2149 fn as_ref(&self) -> &[T] {
2154 #[stable(feature = "vec_as_mut", since = "1.5.0")]
2155 impl<T> AsMut<[T]> for Vec<T> {
2156 fn as_mut(&mut self) -> &mut [T] {
2161 #[stable(feature = "rust1", since = "1.0.0")]
2162 impl<'a, T: Clone> From<&'a [T]> for Vec<T> {
2164 fn from(s: &'a [T]) -> Vec<T> {
2168 fn from(s: &'a [T]) -> Vec<T> {
2173 #[stable(feature = "vec_from_mut", since = "1.19.0")]
2174 impl<'a, T: Clone> From<&'a mut [T]> for Vec<T> {
2176 fn from(s: &'a mut [T]) -> Vec<T> {
2180 fn from(s: &'a mut [T]) -> Vec<T> {
2185 #[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
2186 impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where [T]: ToOwned<Owned=Vec<T>> {
2187 fn from(s: Cow<'a, [T]>) -> Vec<T> {
2192 // note: test pulls in libstd, which causes errors here
2194 #[stable(feature = "vec_from_box", since = "1.18.0")]
2195 impl<T> From<Box<[T]>> for Vec<T> {
2196 fn from(s: Box<[T]>) -> Vec<T> {
2201 // note: test pulls in libstd, which causes errors here
2203 #[stable(feature = "box_from_vec", since = "1.20.0")]
2204 impl<T> From<Vec<T>> for Box<[T]> {
2205 fn from(v: Vec<T>) -> Box<[T]> {
2206 v.into_boxed_slice()
2210 #[stable(feature = "rust1", since = "1.0.0")]
2211 impl<'a> From<&'a str> for Vec<u8> {
2212 fn from(s: &'a str) -> Vec<u8> {
2213 From::from(s.as_bytes())
2217 ////////////////////////////////////////////////////////////////////////////////
2219 ////////////////////////////////////////////////////////////////////////////////
2221 #[stable(feature = "cow_from_vec", since = "1.8.0")]
2222 impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> {
2223 fn from(s: &'a [T]) -> Cow<'a, [T]> {
2228 #[stable(feature = "cow_from_vec", since = "1.8.0")]
2229 impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> {
2230 fn from(v: Vec<T>) -> Cow<'a, [T]> {
2235 #[stable(feature = "rust1", since = "1.0.0")]
2236 impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone {
2237 fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {
2238 Cow::Owned(FromIterator::from_iter(it))
2242 ////////////////////////////////////////////////////////////////////////////////
2244 ////////////////////////////////////////////////////////////////////////////////
2246 /// An iterator that moves out of a vector.
2248 /// This `struct` is created by the `into_iter` method on [`Vec`][`Vec`] (provided
2249 /// by the [`IntoIterator`] trait).
2251 /// [`Vec`]: struct.Vec.html
2252 /// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html
2253 #[stable(feature = "rust1", since = "1.0.0")]
2254 pub struct IntoIter<T> {
2256 phantom: PhantomData<T>,
2262 #[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
2263 impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
2264 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2265 f.debug_tuple("IntoIter")
2266 .field(&self.as_slice())
2271 impl<T> IntoIter<T> {
2272 /// Returns the remaining items of this iterator as a slice.
2277 /// let vec = vec!['a', 'b', 'c'];
2278 /// let mut into_iter = vec.into_iter();
2279 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
2280 /// let _ = into_iter.next().unwrap();
2281 /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
2283 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
2284 pub fn as_slice(&self) -> &[T] {
2286 slice::from_raw_parts(self.ptr, self.len())
2290 /// Returns the remaining items of this iterator as a mutable slice.
2295 /// let vec = vec!['a', 'b', 'c'];
2296 /// let mut into_iter = vec.into_iter();
2297 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
2298 /// into_iter.as_mut_slice()[2] = 'z';
2299 /// assert_eq!(into_iter.next().unwrap(), 'a');
2300 /// assert_eq!(into_iter.next().unwrap(), 'b');
2301 /// assert_eq!(into_iter.next().unwrap(), 'z');
2303 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
2304 pub fn as_mut_slice(&mut self) -> &mut [T] {
2306 slice::from_raw_parts_mut(self.ptr as *mut T, self.len())
2311 #[stable(feature = "rust1", since = "1.0.0")]
2312 unsafe impl<T: Send> Send for IntoIter<T> {}
2313 #[stable(feature = "rust1", since = "1.0.0")]
2314 unsafe impl<T: Sync> Sync for IntoIter<T> {}
2316 #[stable(feature = "rust1", since = "1.0.0")]
2317 impl<T> Iterator for IntoIter<T> {
2321 fn next(&mut self) -> Option<T> {
2323 if self.ptr as *const _ == self.end {
2326 if mem::size_of::<T>() == 0 {
2327 // purposefully don't use 'ptr.offset' because for
2328 // vectors with 0-size elements this would return the
2330 self.ptr = arith_offset(self.ptr as *const i8, 1) as *mut T;
2332 // Use a non-null pointer value
2333 // (self.ptr might be null because of wrapping)
2334 Some(ptr::read(1 as *mut T))
2337 self.ptr = self.ptr.offset(1);
2339 Some(ptr::read(old))
2346 fn size_hint(&self) -> (usize, Option<usize>) {
2347 let exact = match self.ptr.offset_to(self.end) {
2348 Some(x) => x as usize,
2349 None => (self.end as usize).wrapping_sub(self.ptr as usize),
2351 (exact, Some(exact))
2355 fn count(self) -> usize {
2360 #[stable(feature = "rust1", since = "1.0.0")]
2361 impl<T> DoubleEndedIterator for IntoIter<T> {
2363 fn next_back(&mut self) -> Option<T> {
2365 if self.end == self.ptr {
2368 if mem::size_of::<T>() == 0 {
2369 // See above for why 'ptr.offset' isn't used
2370 self.end = arith_offset(self.end as *const i8, -1) as *mut T;
2372 // Use a non-null pointer value
2373 // (self.end might be null because of wrapping)
2374 Some(ptr::read(1 as *mut T))
2376 self.end = self.end.offset(-1);
2378 Some(ptr::read(self.end))
2385 #[stable(feature = "rust1", since = "1.0.0")]
2386 impl<T> ExactSizeIterator for IntoIter<T> {
2387 fn is_empty(&self) -> bool {
2388 self.ptr == self.end
2392 #[unstable(feature = "fused", issue = "35602")]
2393 impl<T> FusedIterator for IntoIter<T> {}
2395 #[unstable(feature = "trusted_len", issue = "37572")]
2396 unsafe impl<T> TrustedLen for IntoIter<T> {}
2398 #[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
2399 impl<T: Clone> Clone for IntoIter<T> {
2400 fn clone(&self) -> IntoIter<T> {
2401 self.as_slice().to_owned().into_iter()
2405 #[stable(feature = "rust1", since = "1.0.0")]
2406 unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
2407 fn drop(&mut self) {
2408 // destroy the remaining elements
2409 for _x in self.by_ref() {}
2411 // RawVec handles deallocation
2412 let _ = unsafe { RawVec::from_raw_parts(self.buf.as_ptr(), self.cap) };
2416 /// A draining iterator for `Vec<T>`.
2418 /// This `struct` is created by the [`drain`] method on [`Vec`].
2420 /// [`drain`]: struct.Vec.html#method.drain
2421 /// [`Vec`]: struct.Vec.html
2422 #[stable(feature = "drain", since = "1.6.0")]
2423 pub struct Drain<'a, T: 'a> {
2424 /// Index of tail to preserve
2428 /// Current remaining range to remove
2429 iter: slice::Iter<'a, T>,
2430 vec: NonNull<Vec<T>>,
2433 #[stable(feature = "collection_debug", since = "1.17.0")]
2434 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
2435 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2436 f.debug_tuple("Drain")
2437 .field(&self.iter.as_slice())
2442 #[stable(feature = "drain", since = "1.6.0")]
2443 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
2444 #[stable(feature = "drain", since = "1.6.0")]
2445 unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
2447 #[stable(feature = "drain", since = "1.6.0")]
2448 impl<'a, T> Iterator for Drain<'a, T> {
2452 fn next(&mut self) -> Option<T> {
2453 self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
2456 fn size_hint(&self) -> (usize, Option<usize>) {
2457 self.iter.size_hint()
2461 #[stable(feature = "drain", since = "1.6.0")]
2462 impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
2464 fn next_back(&mut self) -> Option<T> {
2465 self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
2469 #[stable(feature = "drain", since = "1.6.0")]
2470 impl<'a, T> Drop for Drain<'a, T> {
2471 fn drop(&mut self) {
2472 // exhaust self first
2473 while let Some(_) = self.next() {}
2475 if self.tail_len > 0 {
2477 let source_vec = self.vec.as_mut();
2478 // memmove back untouched tail, update to new length
2479 let start = source_vec.len();
2480 let tail = self.tail_start;
2481 let src = source_vec.as_ptr().offset(tail as isize);
2482 let dst = source_vec.as_mut_ptr().offset(start as isize);
2483 ptr::copy(src, dst, self.tail_len);
2484 source_vec.set_len(start + self.tail_len);
2491 #[stable(feature = "drain", since = "1.6.0")]
2492 impl<'a, T> ExactSizeIterator for Drain<'a, T> {
2493 fn is_empty(&self) -> bool {
2494 self.iter.is_empty()
2498 #[unstable(feature = "fused", issue = "35602")]
2499 impl<'a, T> FusedIterator for Drain<'a, T> {}
2501 /// A place for insertion at the back of a `Vec`.
2503 /// See [`Vec::place_back`](struct.Vec.html#method.place_back) for details.
2504 #[must_use = "places do nothing unless written to with `<-` syntax"]
2505 #[unstable(feature = "collection_placement",
2506 reason = "struct name and placement protocol are subject to change",
2509 pub struct PlaceBack<'a, T: 'a> {
2510 vec: &'a mut Vec<T>,
2513 #[unstable(feature = "collection_placement",
2514 reason = "placement protocol is subject to change",
2516 impl<'a, T> Placer<T> for PlaceBack<'a, T> {
2517 type Place = PlaceBack<'a, T>;
2519 fn make_place(self) -> Self {
2520 // This will panic or abort if we would allocate > isize::MAX bytes
2521 // or if the length increment would overflow for zero-sized types.
2522 if self.vec.len == self.vec.buf.cap() {
2523 self.vec.buf.double();
2529 #[unstable(feature = "collection_placement",
2530 reason = "placement protocol is subject to change",
2532 unsafe impl<'a, T> Place<T> for PlaceBack<'a, T> {
2533 fn pointer(&mut self) -> *mut T {
2534 unsafe { self.vec.as_mut_ptr().offset(self.vec.len as isize) }
2538 #[unstable(feature = "collection_placement",
2539 reason = "placement protocol is subject to change",
2541 impl<'a, T> InPlace<T> for PlaceBack<'a, T> {
2542 type Owner = &'a mut T;
2544 unsafe fn finalize(mut self) -> &'a mut T {
2545 let ptr = self.pointer();
2552 /// A splicing iterator for `Vec`.
2554 /// This struct is created by the [`splice()`] method on [`Vec`]. See its
2555 /// documentation for more.
2557 /// [`splice()`]: struct.Vec.html#method.splice
2558 /// [`Vec`]: struct.Vec.html
2560 #[stable(feature = "vec_splice", since = "1.21.0")]
2561 pub struct Splice<'a, I: Iterator + 'a> {
2562 drain: Drain<'a, I::Item>,
2566 #[stable(feature = "vec_splice", since = "1.21.0")]
2567 impl<'a, I: Iterator> Iterator for Splice<'a, I> {
2568 type Item = I::Item;
2570 fn next(&mut self) -> Option<Self::Item> {
2574 fn size_hint(&self) -> (usize, Option<usize>) {
2575 self.drain.size_hint()
2579 #[stable(feature = "vec_splice", since = "1.21.0")]
2580 impl<'a, I: Iterator> DoubleEndedIterator for Splice<'a, I> {
2581 fn next_back(&mut self) -> Option<Self::Item> {
2582 self.drain.next_back()
2586 #[stable(feature = "vec_splice", since = "1.21.0")]
2587 impl<'a, I: Iterator> ExactSizeIterator for Splice<'a, I> {}
2590 #[stable(feature = "vec_splice", since = "1.21.0")]
2591 impl<'a, I: Iterator> Drop for Splice<'a, I> {
2592 fn drop(&mut self) {
2593 // exhaust drain first
2594 while let Some(_) = self.drain.next() {}
2598 if self.drain.tail_len == 0 {
2599 self.drain.vec.as_mut().extend(self.replace_with.by_ref());
2603 // First fill the range left by drain().
2604 if !self.drain.fill(&mut self.replace_with) {
2608 // There may be more elements. Use the lower bound as an estimate.
2609 // FIXME: Is the upper bound a better guess? Or something else?
2610 let (lower_bound, _upper_bound) = self.replace_with.size_hint();
2611 if lower_bound > 0 {
2612 self.drain.move_tail(lower_bound);
2613 if !self.drain.fill(&mut self.replace_with) {
2618 // Collect any remaining elements.
2619 // This is a zero-length vector which does not allocate if `lower_bound` was exact.
2620 let mut collected = self.replace_with.by_ref().collect::<Vec<I::Item>>().into_iter();
2621 // Now we have an exact count.
2622 if collected.len() > 0 {
2623 self.drain.move_tail(collected.len());
2624 let filled = self.drain.fill(&mut collected);
2625 debug_assert!(filled);
2626 debug_assert_eq!(collected.len(), 0);
2629 // Let `Drain::drop` move the tail back if necessary and restore `vec.len`.
2633 /// Private helper methods for `Splice::drop`
2634 impl<'a, T> Drain<'a, T> {
2635 /// The range from `self.vec.len` to `self.tail_start` contains elements
2636 /// that have been moved out.
2637 /// Fill that range as much as possible with new elements from the `replace_with` iterator.
2638 /// Return whether we filled the entire range. (`replace_with.next()` didn’t return `None`.)
2639 unsafe fn fill<I: Iterator<Item=T>>(&mut self, replace_with: &mut I) -> bool {
2640 let vec = self.vec.as_mut();
2641 let range_start = vec.len;
2642 let range_end = self.tail_start;
2643 let range_slice = slice::from_raw_parts_mut(
2644 vec.as_mut_ptr().offset(range_start as isize),
2645 range_end - range_start);
2647 for place in range_slice {
2648 if let Some(new_item) = replace_with.next() {
2649 ptr::write(place, new_item);
2658 /// Make room for inserting more elements before the tail.
2659 unsafe fn move_tail(&mut self, extra_capacity: usize) {
2660 let vec = self.vec.as_mut();
2661 let used_capacity = self.tail_start + self.tail_len;
2662 vec.buf.reserve(used_capacity, extra_capacity);
2664 let new_tail_start = self.tail_start + extra_capacity;
2665 let src = vec.as_ptr().offset(self.tail_start as isize);
2666 let dst = vec.as_mut_ptr().offset(new_tail_start as isize);
2667 ptr::copy(src, dst, self.tail_len);
2668 self.tail_start = new_tail_start;
2672 /// An iterator produced by calling `drain_filter` on Vec.
2673 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2675 pub struct DrainFilter<'a, T: 'a, F>
2676 where F: FnMut(&mut T) -> bool,
2678 vec: &'a mut Vec<T>,
2685 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2686 impl<'a, T, F> Iterator for DrainFilter<'a, T, F>
2687 where F: FnMut(&mut T) -> bool,
2691 fn next(&mut self) -> Option<T> {
2693 while self.idx != self.old_len {
2696 let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
2697 if (self.pred)(&mut v[i]) {
2699 return Some(ptr::read(&v[i]));
2700 } else if self.del > 0 {
2702 let src: *const T = &v[i];
2703 let dst: *mut T = &mut v[i - del];
2704 // This is safe because self.vec has length 0
2705 // thus its elements will not have Drop::drop
2706 // called on them in the event of a panic.
2707 ptr::copy_nonoverlapping(src, dst, 1);
2714 fn size_hint(&self) -> (usize, Option<usize>) {
2715 (0, Some(self.old_len - self.idx))
2719 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2720 impl<'a, T, F> Drop for DrainFilter<'a, T, F>
2721 where F: FnMut(&mut T) -> bool,
2723 fn drop(&mut self) {
2724 for _ in self.by_ref() { }
2727 self.vec.set_len(self.old_len - self.del);