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};
77 use core::ops::{InPlace, Index, IndexMut, Place, Placer};
80 use core::ptr::Shared;
87 use super::range::RangeArgument;
88 use Bound::{Excluded, Included, Unbounded};
90 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
95 /// let mut vec = Vec::new();
99 /// assert_eq!(vec.len(), 2);
100 /// assert_eq!(vec[0], 1);
102 /// assert_eq!(vec.pop(), Some(2));
103 /// assert_eq!(vec.len(), 1);
106 /// assert_eq!(vec[0], 7);
108 /// vec.extend([1, 2, 3].iter().cloned());
111 /// println!("{}", x);
113 /// assert_eq!(vec, [7, 1, 2, 3]);
116 /// The [`vec!`] macro is provided to make initialization more convenient:
119 /// let mut vec = vec![1, 2, 3];
121 /// assert_eq!(vec, [1, 2, 3, 4]);
124 /// It can also initialize each element of a `Vec<T>` with a given value:
127 /// let vec = vec![0; 5];
128 /// assert_eq!(vec, [0, 0, 0, 0, 0]);
131 /// Use a `Vec<T>` as an efficient stack:
134 /// let mut stack = Vec::new();
140 /// while let Some(top) = stack.pop() {
141 /// // Prints 3, 2, 1
142 /// println!("{}", top);
148 /// The `Vec` type allows to access values by index, because it implements the
149 /// [`Index`] trait. An example will be more explicit:
152 /// let v = vec![0, 2, 4, 6];
153 /// println!("{}", v[1]); // it will display '2'
156 /// However be careful: if you try to access an index which isn't in the `Vec`,
157 /// your software will panic! You cannot do this:
160 /// let v = vec![0, 2, 4, 6];
161 /// println!("{}", v[6]); // it will panic!
164 /// In conclusion: always check if the index you want to get really exists
169 /// A `Vec` can be mutable. Slices, on the other hand, are read-only objects.
170 /// To get a slice, use `&`. Example:
173 /// fn read_slice(slice: &[usize]) {
177 /// let v = vec![0, 1];
180 /// // ... and that's all!
181 /// // you can also do it like this:
182 /// let x : &[usize] = &v;
185 /// In Rust, it's more common to pass slices as arguments rather than vectors
186 /// when you just want to provide a read access. The same goes for [`String`] and
189 /// # Capacity and reallocation
191 /// The capacity of a vector is the amount of space allocated for any future
192 /// elements that will be added onto the vector. This is not to be confused with
193 /// the *length* of a vector, which specifies the number of actual elements
194 /// within the vector. If a vector's length exceeds its capacity, its capacity
195 /// will automatically be increased, but its elements will have to be
198 /// For example, a vector with capacity 10 and length 0 would be an empty vector
199 /// with space for 10 more elements. Pushing 10 or fewer elements onto the
200 /// vector will not change its capacity or cause reallocation to occur. However,
201 /// if the vector's length is increased to 11, it will have to reallocate, which
202 /// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`]
203 /// whenever possible to specify how big the vector is expected to get.
207 /// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees
208 /// about its design. This ensures that it's as low-overhead as possible in
209 /// the general case, and can be correctly manipulated in primitive ways
210 /// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`.
211 /// If additional type parameters are added (e.g. to support custom allocators),
212 /// overriding their defaults may change the behavior.
214 /// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length)
215 /// triplet. No more, no less. The order of these fields is completely
216 /// unspecified, and you should use the appropriate methods to modify these.
217 /// The pointer will never be null, so this type is null-pointer-optimized.
219 /// However, the pointer may not actually point to allocated memory. In particular,
220 /// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`],
221 /// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`]
222 /// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized
223 /// types inside a `Vec`, it will not allocate space for them. *Note that in this case
224 /// the `Vec` may not report a [`capacity`] of 0*. `Vec` will allocate if and only
225 /// if [`mem::size_of::<T>`]`() * capacity() > 0`. In general, `Vec`'s allocation
226 /// details are subtle enough that it is strongly recommended that you only
227 /// free memory allocated by a `Vec` by creating a new `Vec` and dropping it.
229 /// If a `Vec` *has* allocated memory, then the memory it points to is on the heap
230 /// (as defined by the allocator Rust is configured to use by default), and its
231 /// pointer points to [`len`] initialized elements in order (what you would see
232 /// if you coerced it to a slice), followed by [`capacity`]` - `[`len`]
233 /// logically uninitialized elements.
235 /// `Vec` will never perform a "small optimization" where elements are actually
236 /// stored on the stack for two reasons:
238 /// * It would make it more difficult for unsafe code to correctly manipulate
239 /// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were
240 /// only moved, and it would be more difficult to determine if a `Vec` had
241 /// actually allocated memory.
243 /// * It would penalize the general case, incurring an additional branch
246 /// `Vec` will never automatically shrink itself, even if completely empty. This
247 /// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec`
248 /// and then filling it back up to the same [`len`] should incur no calls to
249 /// the allocator. If you wish to free up unused memory, use
250 /// [`shrink_to_fit`][`shrink_to_fit`].
252 /// [`push`] and [`insert`] will never (re)allocate if the reported capacity is
253 /// sufficient. [`push`] and [`insert`] *will* (re)allocate if
254 /// [`len`]` == `[`capacity`]. That is, the reported capacity is completely
255 /// accurate, and can be relied on. It can even be used to manually free the memory
256 /// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even
257 /// when not necessary.
259 /// `Vec` does not guarantee any particular growth strategy when reallocating
260 /// when full, nor when [`reserve`] is called. The current strategy is basic
261 /// and it may prove desirable to use a non-constant growth factor. Whatever
262 /// strategy is used will of course guarantee `O(1)` amortized [`push`].
264 /// `vec![x; n]`, `vec![a, b, c, d]`, and
265 /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
266 /// with exactly the requested capacity. If [`len`]` == `[`capacity`],
267 /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
268 /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
270 /// `Vec` will not specifically overwrite any data that is removed from it,
271 /// but also won't specifically preserve it. Its uninitialized memory is
272 /// scratch space that it may use however it wants. It will generally just do
273 /// whatever is most efficient or otherwise easy to implement. Do not rely on
274 /// removed data to be erased for security purposes. Even if you drop a `Vec`, its
275 /// buffer may simply be reused by another `Vec`. Even if you zero a `Vec`'s memory
276 /// first, that may not actually happen because the optimizer does not consider
277 /// this a side-effect that must be preserved. There is one case which we will
278 /// not break, however: using `unsafe` code to write to the excess capacity,
279 /// and then increasing the length to match, is always valid.
281 /// `Vec` does not currently guarantee the order in which elements are dropped
282 /// (the order has changed in the past, and may change again).
284 /// [`vec!`]: ../../std/macro.vec.html
285 /// [`Index`]: ../../std/ops/trait.Index.html
286 /// [`String`]: ../../std/string/struct.String.html
287 /// [`&str`]: ../../std/primitive.str.html
288 /// [`Vec::with_capacity`]: ../../std/vec/struct.Vec.html#method.with_capacity
289 /// [`Vec::new`]: ../../std/vec/struct.Vec.html#method.new
290 /// [`shrink_to_fit`]: ../../std/vec/struct.Vec.html#method.shrink_to_fit
291 /// [`capacity`]: ../../std/vec/struct.Vec.html#method.capacity
292 /// [`mem::size_of::<T>`]: ../../std/mem/fn.size_of.html
293 /// [`len`]: ../../std/vec/struct.Vec.html#method.len
294 /// [`push`]: ../../std/vec/struct.Vec.html#method.push
295 /// [`insert`]: ../../std/vec/struct.Vec.html#method.insert
296 /// [`reserve`]: ../../std/vec/struct.Vec.html#method.reserve
297 /// [owned slice]: ../../std/boxed/struct.Box.html
298 #[stable(feature = "rust1", since = "1.0.0")]
304 ////////////////////////////////////////////////////////////////////////////////
306 ////////////////////////////////////////////////////////////////////////////////
309 /// Constructs a new, empty `Vec<T>`.
311 /// The vector will not allocate until elements are pushed onto it.
316 /// # #![allow(unused_mut)]
317 /// let mut vec: Vec<i32> = Vec::new();
320 #[stable(feature = "rust1", since = "1.0.0")]
321 pub fn new() -> Vec<T> {
328 /// Constructs a new, empty `Vec<T>` with the specified capacity.
330 /// The vector will be able to hold exactly `capacity` elements without
331 /// reallocating. If `capacity` is 0, the vector will not allocate.
333 /// It is important to note that this function does not specify the *length*
334 /// of the returned vector, but only the *capacity*. For an explanation of
335 /// the difference between length and capacity, see *[Capacity and reallocation]*.
337 /// [Capacity and reallocation]: #capacity-and-reallocation
342 /// let mut vec = Vec::with_capacity(10);
344 /// // The vector contains no items, even though it has capacity for more
345 /// assert_eq!(vec.len(), 0);
347 /// // These are all done without reallocating...
352 /// // ...but this may make the vector reallocate
356 #[stable(feature = "rust1", since = "1.0.0")]
357 pub fn with_capacity(capacity: usize) -> Vec<T> {
359 buf: RawVec::with_capacity(capacity),
364 /// Creates a `Vec<T>` directly from the raw components of another vector.
368 /// This is highly unsafe, due to the number of invariants that aren't
371 /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
372 /// (at least, it's highly likely to be incorrect if it wasn't).
373 /// * `length` needs to be less than or equal to `capacity`.
374 /// * `capacity` needs to be the capacity that the pointer was allocated with.
376 /// Violating these may cause problems like corrupting the allocator's
377 /// internal data structures. For example it is **not** safe
378 /// to build a `Vec<u8>` from a pointer to a C `char` array and a `size_t`.
380 /// The ownership of `ptr` is effectively transferred to the
381 /// `Vec<T>` which may then deallocate, reallocate or change the
382 /// contents of memory pointed to by the pointer at will. Ensure
383 /// that nothing else uses the pointer after calling this
386 /// [`String`]: ../../std/string/struct.String.html
395 /// let mut v = vec![1, 2, 3];
397 /// // Pull out the various important pieces of information about `v`
398 /// let p = v.as_mut_ptr();
399 /// let len = v.len();
400 /// let cap = v.capacity();
403 /// // Cast `v` into the void: no destructor run, so we are in
404 /// // complete control of the allocation to which `p` points.
407 /// // Overwrite memory with 4, 5, 6
408 /// for i in 0..len as isize {
409 /// ptr::write(p.offset(i), 4 + i);
412 /// // Put everything back together into a Vec
413 /// let rebuilt = Vec::from_raw_parts(p, len, cap);
414 /// assert_eq!(rebuilt, [4, 5, 6]);
418 #[stable(feature = "rust1", since = "1.0.0")]
419 pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T> {
421 buf: RawVec::from_raw_parts(ptr, capacity),
426 /// Returns the number of elements the vector can hold without
432 /// let vec: Vec<i32> = Vec::with_capacity(10);
433 /// assert_eq!(vec.capacity(), 10);
436 #[stable(feature = "rust1", since = "1.0.0")]
437 pub fn capacity(&self) -> usize {
441 /// Reserves capacity for at least `additional` more elements to be inserted
442 /// in the given `Vec<T>`. The collection may reserve more space to avoid
443 /// frequent reallocations. After calling `reserve`, capacity will be
444 /// greater than or equal to `self.len() + additional`. Does nothing if
445 /// capacity is already sufficient.
449 /// Panics if the new capacity overflows `usize`.
454 /// let mut vec = vec![1];
456 /// assert!(vec.capacity() >= 11);
458 #[stable(feature = "rust1", since = "1.0.0")]
459 pub fn reserve(&mut self, additional: usize) {
460 self.buf.reserve(self.len, additional);
463 /// Reserves the minimum capacity for exactly `additional` more elements to
464 /// be inserted in the given `Vec<T>`. After calling `reserve_exact`,
465 /// capacity will be greater than or equal to `self.len() + additional`.
466 /// Does nothing if the capacity is already sufficient.
468 /// Note that the allocator may give the collection more space than it
469 /// requests. Therefore capacity can not be relied upon to be precisely
470 /// minimal. Prefer `reserve` if future insertions are expected.
474 /// Panics if the new capacity overflows `usize`.
479 /// let mut vec = vec![1];
480 /// vec.reserve_exact(10);
481 /// assert!(vec.capacity() >= 11);
483 #[stable(feature = "rust1", since = "1.0.0")]
484 pub fn reserve_exact(&mut self, additional: usize) {
485 self.buf.reserve_exact(self.len, additional);
488 /// Shrinks the capacity of the vector as much as possible.
490 /// It will drop down as close as possible to the length but the allocator
491 /// may still inform the vector that there is space for a few more elements.
496 /// let mut vec = Vec::with_capacity(10);
497 /// vec.extend([1, 2, 3].iter().cloned());
498 /// assert_eq!(vec.capacity(), 10);
499 /// vec.shrink_to_fit();
500 /// assert!(vec.capacity() >= 3);
502 #[stable(feature = "rust1", since = "1.0.0")]
503 pub fn shrink_to_fit(&mut self) {
504 self.buf.shrink_to_fit(self.len);
507 /// Converts the vector into [`Box<[T]>`][owned slice].
509 /// Note that this will drop any excess capacity. Calling this and
510 /// converting back to a vector with [`into_vec`] is equivalent to calling
511 /// [`shrink_to_fit`].
513 /// [owned slice]: ../../std/boxed/struct.Box.html
514 /// [`into_vec`]: ../../std/primitive.slice.html#method.into_vec
515 /// [`shrink_to_fit`]: #method.shrink_to_fit
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` is out of bounds.
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 let len = self.len();
822 self.truncate(len - del);
826 /// Removes all but the first of consecutive elements in the vector that resolve to the same
829 /// If the vector is sorted, this removes all duplicates.
834 /// let mut vec = vec![10, 20, 21, 30, 20];
836 /// vec.dedup_by_key(|i| *i / 10);
838 /// assert_eq!(vec, [10, 20, 30, 20]);
840 #[stable(feature = "dedup_by", since = "1.16.0")]
842 pub fn dedup_by_key<F, K>(&mut self, mut key: F) where F: FnMut(&mut T) -> K, K: PartialEq {
843 self.dedup_by(|a, b| key(a) == key(b))
846 /// Removes all but the first of consecutive elements in the vector satisfying a given equality
849 /// The `same_bucket` function is passed references to two elements from the vector, and
850 /// returns `true` if the elements compare equal, or `false` if they do not. The elements are
851 /// passed in opposite order from their order in the vector, so if `same_bucket(a, b)` returns
852 /// `true`, `a` is removed.
854 /// If the vector is sorted, this removes all duplicates.
859 /// use std::ascii::AsciiExt;
861 /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];
863 /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));
865 /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]);
867 #[stable(feature = "dedup_by", since = "1.16.0")]
868 pub fn dedup_by<F>(&mut self, mut same_bucket: F) where F: FnMut(&mut T, &mut T) -> bool {
870 // Although we have a mutable reference to `self`, we cannot make
871 // *arbitrary* changes. The `same_bucket` calls could panic, so we
872 // must ensure that the vector is in a valid state at all time.
874 // The way that we handle this is by using swaps; we iterate
875 // over all the elements, swapping as we go so that at the end
876 // the elements we wish to keep are in the front, and those we
877 // wish to reject are at the back. We can then truncate the
878 // vector. This operation is still O(n).
880 // Example: We start in this state, where `r` represents "next
881 // read" and `w` represents "next_write`.
884 // +---+---+---+---+---+---+
885 // | 0 | 1 | 1 | 2 | 3 | 3 |
886 // +---+---+---+---+---+---+
889 // Comparing self[r] against self[w-1], this is not a duplicate, so
890 // we swap self[r] and self[w] (no effect as r==w) and then increment both
891 // r and w, leaving us with:
894 // +---+---+---+---+---+---+
895 // | 0 | 1 | 1 | 2 | 3 | 3 |
896 // +---+---+---+---+---+---+
899 // Comparing self[r] against self[w-1], this value is a duplicate,
900 // so we increment `r` but leave everything else unchanged:
903 // +---+---+---+---+---+---+
904 // | 0 | 1 | 1 | 2 | 3 | 3 |
905 // +---+---+---+---+---+---+
908 // Comparing self[r] against self[w-1], this is not a duplicate,
909 // so swap self[r] and self[w] and advance r and w:
912 // +---+---+---+---+---+---+
913 // | 0 | 1 | 2 | 1 | 3 | 3 |
914 // +---+---+---+---+---+---+
917 // Not a duplicate, repeat:
920 // +---+---+---+---+---+---+
921 // | 0 | 1 | 2 | 3 | 1 | 3 |
922 // +---+---+---+---+---+---+
925 // Duplicate, advance r. End of vec. Truncate to w.
932 // Avoid bounds checks by using raw pointers.
933 let p = self.as_mut_ptr();
934 let mut r: usize = 1;
935 let mut w: usize = 1;
938 let p_r = p.offset(r as isize);
939 let p_wm1 = p.offset((w - 1) as isize);
940 if !same_bucket(&mut *p_r, &mut *p_wm1) {
942 let p_w = p_wm1.offset(1);
943 mem::swap(&mut *p_r, &mut *p_w);
954 /// Appends an element to the back of a collection.
958 /// Panics if the number of elements in the vector overflows a `usize`.
963 /// let mut vec = vec![1, 2];
965 /// assert_eq!(vec, [1, 2, 3]);
968 #[stable(feature = "rust1", since = "1.0.0")]
969 pub fn push(&mut self, value: T) {
970 // This will panic or abort if we would allocate > isize::MAX bytes
971 // or if the length increment would overflow for zero-sized types.
972 if self.len == self.buf.cap() {
976 let end = self.as_mut_ptr().offset(self.len as isize);
977 ptr::write(end, value);
982 /// Returns a place for insertion at the back of the `Vec`.
984 /// Using this method with placement syntax is equivalent to [`push`](#method.push),
985 /// but may be more efficient.
990 /// #![feature(collection_placement)]
991 /// #![feature(placement_in_syntax)]
993 /// let mut vec = vec![1, 2];
994 /// vec.place_back() <- 3;
995 /// vec.place_back() <- 4;
996 /// assert_eq!(&vec, &[1, 2, 3, 4]);
998 #[unstable(feature = "collection_placement",
999 reason = "placement protocol is subject to change",
1001 pub fn place_back(&mut self) -> PlaceBack<T> {
1002 PlaceBack { vec: self }
1005 /// Removes the last element from a vector and returns it, or [`None`] if it
1008 /// [`None`]: ../../std/option/enum.Option.html#variant.None
1013 /// let mut vec = vec![1, 2, 3];
1014 /// assert_eq!(vec.pop(), Some(3));
1015 /// assert_eq!(vec, [1, 2]);
1018 #[stable(feature = "rust1", since = "1.0.0")]
1019 pub fn pop(&mut self) -> Option<T> {
1025 Some(ptr::read(self.get_unchecked(self.len())))
1030 /// Moves all the elements of `other` into `Self`, leaving `other` empty.
1034 /// Panics if the number of elements in the vector overflows a `usize`.
1039 /// let mut vec = vec![1, 2, 3];
1040 /// let mut vec2 = vec![4, 5, 6];
1041 /// vec.append(&mut vec2);
1042 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
1043 /// assert_eq!(vec2, []);
1046 #[stable(feature = "append", since = "1.4.0")]
1047 pub fn append(&mut self, other: &mut Self) {
1049 self.append_elements(other.as_slice() as _);
1054 /// Appends elements to `Self` from other buffer.
1056 unsafe fn append_elements(&mut self, other: *const [T]) {
1057 let count = (*other).len();
1058 self.reserve(count);
1059 let len = self.len();
1060 ptr::copy_nonoverlapping(other as *const T, self.get_unchecked_mut(len), count);
1064 /// Creates a draining iterator that removes the specified range in the vector
1065 /// and yields the removed items.
1067 /// Note 1: The element range is removed even if the iterator is only
1068 /// partially consumed or not consumed at all.
1070 /// Note 2: It is unspecified how many elements are removed from the vector
1071 /// if the `Drain` value is leaked.
1075 /// Panics if the starting point is greater than the end point or if
1076 /// the end point is greater than the length of the vector.
1081 /// let mut v = vec![1, 2, 3];
1082 /// let u: Vec<_> = v.drain(1..).collect();
1083 /// assert_eq!(v, &[1]);
1084 /// assert_eq!(u, &[2, 3]);
1086 /// // A full range clears the vector
1088 /// assert_eq!(v, &[]);
1090 #[stable(feature = "drain", since = "1.6.0")]
1091 pub fn drain<R>(&mut self, range: R) -> Drain<T>
1092 where R: RangeArgument<usize>
1096 // When the Drain is first created, it shortens the length of
1097 // the source vector to make sure no uninitalized or moved-from elements
1098 // are accessible at all if the Drain's destructor never gets to run.
1100 // Drain will ptr::read out the values to remove.
1101 // When finished, remaining tail of the vec is copied back to cover
1102 // the hole, and the vector length is restored to the new length.
1104 let len = self.len();
1105 let start = match range.start() {
1107 Excluded(&n) => n + 1,
1110 let end = match range.end() {
1111 Included(&n) => n + 1,
1115 assert!(start <= end);
1116 assert!(end <= len);
1119 // set self.vec length's to start, to be safe in case Drain is leaked
1120 self.set_len(start);
1121 // Use the borrow in the IterMut to indicate borrowing behavior of the
1122 // whole Drain iterator (like &mut T).
1123 let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().offset(start as isize),
1127 tail_len: len - end,
1128 iter: range_slice.iter(),
1129 vec: Shared::from(self),
1134 /// Clears the vector, removing all values.
1136 /// Note that this method has no effect on the allocated capacity
1142 /// let mut v = vec![1, 2, 3];
1146 /// assert!(v.is_empty());
1149 #[stable(feature = "rust1", since = "1.0.0")]
1150 pub fn clear(&mut self) {
1154 /// Returns the number of elements in the vector, also referred to
1155 /// as its 'length'.
1160 /// let a = vec![1, 2, 3];
1161 /// assert_eq!(a.len(), 3);
1164 #[stable(feature = "rust1", since = "1.0.0")]
1165 pub fn len(&self) -> usize {
1169 /// Returns `true` if the vector contains no elements.
1174 /// let mut v = Vec::new();
1175 /// assert!(v.is_empty());
1178 /// assert!(!v.is_empty());
1180 #[stable(feature = "rust1", since = "1.0.0")]
1181 pub fn is_empty(&self) -> bool {
1185 /// Splits the collection into two at the given index.
1187 /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`,
1188 /// and the returned `Self` contains elements `[at, len)`.
1190 /// Note that the capacity of `self` does not change.
1194 /// Panics if `at > len`.
1199 /// let mut vec = vec![1,2,3];
1200 /// let vec2 = vec.split_off(1);
1201 /// assert_eq!(vec, [1]);
1202 /// assert_eq!(vec2, [2, 3]);
1205 #[stable(feature = "split_off", since = "1.4.0")]
1206 pub fn split_off(&mut self, at: usize) -> Self {
1207 assert!(at <= self.len(), "`at` out of bounds");
1209 let other_len = self.len - at;
1210 let mut other = Vec::with_capacity(other_len);
1212 // Unsafely `set_len` and copy items to `other`.
1215 other.set_len(other_len);
1217 ptr::copy_nonoverlapping(self.as_ptr().offset(at as isize),
1225 impl<T: Clone> Vec<T> {
1226 /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
1228 /// If `new_len` is greater than `len`, the `Vec` is extended by the
1229 /// difference, with each additional slot filled with `value`.
1230 /// If `new_len` is less than `len`, the `Vec` is simply truncated.
1232 /// This method requires `Clone` to clone the passed value. If you'd
1233 /// rather create a value with `Default` instead, see [`resize_default`].
1238 /// let mut vec = vec!["hello"];
1239 /// vec.resize(3, "world");
1240 /// assert_eq!(vec, ["hello", "world", "world"]);
1242 /// let mut vec = vec![1, 2, 3, 4];
1243 /// vec.resize(2, 0);
1244 /// assert_eq!(vec, [1, 2]);
1247 /// [`resize_default`]: #method.resize_default
1248 #[stable(feature = "vec_resize", since = "1.5.0")]
1249 pub fn resize(&mut self, new_len: usize, value: T) {
1250 let len = self.len();
1253 self.extend_with(new_len - len, ExtendElement(value))
1255 self.truncate(new_len);
1259 /// Clones and appends all elements in a slice to the `Vec`.
1261 /// Iterates over the slice `other`, clones each element, and then appends
1262 /// it to this `Vec`. The `other` vector is traversed in-order.
1264 /// Note that this function is same as `extend` except that it is
1265 /// specialized to work with slices instead. If and when Rust gets
1266 /// specialization this function will likely be deprecated (but still
1272 /// let mut vec = vec![1];
1273 /// vec.extend_from_slice(&[2, 3, 4]);
1274 /// assert_eq!(vec, [1, 2, 3, 4]);
1276 #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
1277 pub fn extend_from_slice(&mut self, other: &[T]) {
1278 self.spec_extend(other.iter())
1282 impl<T: Default> Vec<T> {
1283 /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
1285 /// If `new_len` is greater than `len`, the `Vec` is extended by the
1286 /// difference, with each additional slot filled with `Default::default()`.
1287 /// If `new_len` is less than `len`, the `Vec` is simply truncated.
1289 /// This method uses `Default` to create new values on every push. If
1290 /// you'd rather `Clone` a given value, use [`resize`].
1296 /// #![feature(vec_resize_default)]
1298 /// let mut vec = vec![1, 2, 3];
1299 /// vec.resize_default(5);
1300 /// assert_eq!(vec, [1, 2, 3, 0, 0]);
1302 /// let mut vec = vec![1, 2, 3, 4];
1303 /// vec.resize_default(2);
1304 /// assert_eq!(vec, [1, 2]);
1307 /// [`resize`]: #method.resize
1308 #[unstable(feature = "vec_resize_default", issue = "41758")]
1309 pub fn resize_default(&mut self, new_len: usize) {
1310 let len = self.len();
1313 self.extend_with(new_len - len, ExtendDefault);
1315 self.truncate(new_len);
1320 // This code generalises `extend_with_{element,default}`.
1321 trait ExtendWith<T> {
1322 fn next(&self) -> T;
1326 struct ExtendElement<T>(T);
1327 impl<T: Clone> ExtendWith<T> for ExtendElement<T> {
1328 fn next(&self) -> T { self.0.clone() }
1329 fn last(self) -> T { self.0 }
1332 struct ExtendDefault;
1333 impl<T: Default> ExtendWith<T> for ExtendDefault {
1334 fn next(&self) -> T { Default::default() }
1335 fn last(self) -> T { Default::default() }
1338 /// Extend the vector by `n` values, using the given generator.
1339 fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, value: E) {
1343 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1344 // Use SetLenOnDrop to work around bug where compiler
1345 // may not realize the store through `ptr` through self.set_len()
1347 let mut local_len = SetLenOnDrop::new(&mut self.len);
1349 // Write all elements except the last one
1351 ptr::write(ptr, value.next());
1352 ptr = ptr.offset(1);
1353 // Increment the length in every step in case next() panics
1354 local_len.increment_len(1);
1358 // We can write the last element directly without cloning needlessly
1359 ptr::write(ptr, value.last());
1360 local_len.increment_len(1);
1363 // len set by scope guard
1368 // Set the length of the vec when the `SetLenOnDrop` value goes out of scope.
1370 // The idea is: The length field in SetLenOnDrop is a local variable
1371 // that the optimizer will see does not alias with any stores through the Vec's data
1372 // pointer. This is a workaround for alias analysis issue #32155
1373 struct SetLenOnDrop<'a> {
1378 impl<'a> SetLenOnDrop<'a> {
1380 fn new(len: &'a mut usize) -> Self {
1381 SetLenOnDrop { local_len: *len, len: len }
1385 fn increment_len(&mut self, increment: usize) {
1386 self.local_len += increment;
1390 impl<'a> Drop for SetLenOnDrop<'a> {
1392 fn drop(&mut self) {
1393 *self.len = self.local_len;
1397 impl<T: PartialEq> Vec<T> {
1398 /// Removes consecutive repeated elements in the vector.
1400 /// If the vector is sorted, this removes all duplicates.
1405 /// let mut vec = vec![1, 2, 2, 3, 2];
1409 /// assert_eq!(vec, [1, 2, 3, 2]);
1411 #[stable(feature = "rust1", since = "1.0.0")]
1413 pub fn dedup(&mut self) {
1414 self.dedup_by(|a, b| a == b)
1417 /// Removes the first instance of `item` from the vector if the item exists.
1422 /// # #![feature(vec_remove_item)]
1423 /// let mut vec = vec![1, 2, 3, 1];
1425 /// vec.remove_item(&1);
1427 /// assert_eq!(vec, vec![2, 3, 1]);
1429 #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")]
1430 pub fn remove_item(&mut self, item: &T) -> Option<T> {
1431 let pos = match self.iter().position(|x| *x == *item) {
1433 None => return None,
1435 Some(self.remove(pos))
1439 ////////////////////////////////////////////////////////////////////////////////
1440 // Internal methods and functions
1441 ////////////////////////////////////////////////////////////////////////////////
1444 #[stable(feature = "rust1", since = "1.0.0")]
1445 pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
1446 <T as SpecFromElem>::from_elem(elem, n)
1449 // Specialization trait used for Vec::from_elem
1450 trait SpecFromElem: Sized {
1451 fn from_elem(elem: Self, n: usize) -> Vec<Self>;
1454 impl<T: Clone> SpecFromElem for T {
1455 default fn from_elem(elem: Self, n: usize) -> Vec<Self> {
1456 let mut v = Vec::with_capacity(n);
1457 v.extend_with(n, ExtendElement(elem));
1462 impl SpecFromElem for u8 {
1464 fn from_elem(elem: u8, n: usize) -> Vec<u8> {
1467 buf: RawVec::with_capacity_zeroed(n),
1472 let mut v = Vec::with_capacity(n);
1473 ptr::write_bytes(v.as_mut_ptr(), elem, n);
1480 macro_rules! impl_spec_from_elem {
1481 ($t: ty, $is_zero: expr) => {
1482 impl SpecFromElem for $t {
1484 fn from_elem(elem: $t, n: usize) -> Vec<$t> {
1487 buf: RawVec::with_capacity_zeroed(n),
1491 let mut v = Vec::with_capacity(n);
1492 v.extend_with(n, ExtendElement(elem));
1499 impl_spec_from_elem!(i8, |x| x == 0);
1500 impl_spec_from_elem!(i16, |x| x == 0);
1501 impl_spec_from_elem!(i32, |x| x == 0);
1502 impl_spec_from_elem!(i64, |x| x == 0);
1503 impl_spec_from_elem!(i128, |x| x == 0);
1504 impl_spec_from_elem!(isize, |x| x == 0);
1506 impl_spec_from_elem!(u16, |x| x == 0);
1507 impl_spec_from_elem!(u32, |x| x == 0);
1508 impl_spec_from_elem!(u64, |x| x == 0);
1509 impl_spec_from_elem!(u128, |x| x == 0);
1510 impl_spec_from_elem!(usize, |x| x == 0);
1512 impl_spec_from_elem!(f32, |x: f32| x == 0. && x.is_sign_positive());
1513 impl_spec_from_elem!(f64, |x: f64| x == 0. && x.is_sign_positive());
1515 ////////////////////////////////////////////////////////////////////////////////
1516 // Common trait implementations for Vec
1517 ////////////////////////////////////////////////////////////////////////////////
1519 #[stable(feature = "rust1", since = "1.0.0")]
1520 impl<T: Clone> Clone for Vec<T> {
1522 fn clone(&self) -> Vec<T> {
1523 <[T]>::to_vec(&**self)
1526 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
1527 // required for this method definition, is not available. Instead use the
1528 // `slice::to_vec` function which is only available with cfg(test)
1529 // NB see the slice::hack module in slice.rs for more information
1531 fn clone(&self) -> Vec<T> {
1532 ::slice::to_vec(&**self)
1535 fn clone_from(&mut self, other: &Vec<T>) {
1536 other.as_slice().clone_into(self);
1540 #[stable(feature = "rust1", since = "1.0.0")]
1541 impl<T: Hash> Hash for Vec<T> {
1543 fn hash<H: hash::Hasher>(&self, state: &mut H) {
1544 Hash::hash(&**self, state)
1548 #[stable(feature = "rust1", since = "1.0.0")]
1549 impl<T> Index<usize> for Vec<T> {
1553 fn index(&self, index: usize) -> &T {
1554 // NB built-in indexing via `&[T]`
1559 #[stable(feature = "rust1", since = "1.0.0")]
1560 impl<T> IndexMut<usize> for Vec<T> {
1562 fn index_mut(&mut self, index: usize) -> &mut T {
1563 // NB built-in indexing via `&mut [T]`
1564 &mut (**self)[index]
1569 #[stable(feature = "rust1", since = "1.0.0")]
1570 impl<T> ops::Index<ops::Range<usize>> for Vec<T> {
1574 fn index(&self, index: ops::Range<usize>) -> &[T] {
1575 Index::index(&**self, index)
1578 #[stable(feature = "rust1", since = "1.0.0")]
1579 impl<T> ops::Index<ops::RangeTo<usize>> for Vec<T> {
1583 fn index(&self, index: ops::RangeTo<usize>) -> &[T] {
1584 Index::index(&**self, index)
1587 #[stable(feature = "rust1", since = "1.0.0")]
1588 impl<T> ops::Index<ops::RangeFrom<usize>> for Vec<T> {
1592 fn index(&self, index: ops::RangeFrom<usize>) -> &[T] {
1593 Index::index(&**self, index)
1596 #[stable(feature = "rust1", since = "1.0.0")]
1597 impl<T> ops::Index<ops::RangeFull> for Vec<T> {
1601 fn index(&self, _index: ops::RangeFull) -> &[T] {
1605 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1606 impl<T> ops::Index<ops::RangeInclusive<usize>> for Vec<T> {
1610 fn index(&self, index: ops::RangeInclusive<usize>) -> &[T] {
1611 Index::index(&**self, index)
1614 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1615 impl<T> ops::Index<ops::RangeToInclusive<usize>> for Vec<T> {
1619 fn index(&self, index: ops::RangeToInclusive<usize>) -> &[T] {
1620 Index::index(&**self, index)
1624 #[stable(feature = "rust1", since = "1.0.0")]
1625 impl<T> ops::IndexMut<ops::Range<usize>> for Vec<T> {
1627 fn index_mut(&mut self, index: ops::Range<usize>) -> &mut [T] {
1628 IndexMut::index_mut(&mut **self, index)
1631 #[stable(feature = "rust1", since = "1.0.0")]
1632 impl<T> ops::IndexMut<ops::RangeTo<usize>> for Vec<T> {
1634 fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut [T] {
1635 IndexMut::index_mut(&mut **self, index)
1638 #[stable(feature = "rust1", since = "1.0.0")]
1639 impl<T> ops::IndexMut<ops::RangeFrom<usize>> for Vec<T> {
1641 fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut [T] {
1642 IndexMut::index_mut(&mut **self, index)
1645 #[stable(feature = "rust1", since = "1.0.0")]
1646 impl<T> ops::IndexMut<ops::RangeFull> for Vec<T> {
1648 fn index_mut(&mut self, _index: ops::RangeFull) -> &mut [T] {
1652 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1653 impl<T> ops::IndexMut<ops::RangeInclusive<usize>> for Vec<T> {
1655 fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut [T] {
1656 IndexMut::index_mut(&mut **self, index)
1659 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
1660 impl<T> ops::IndexMut<ops::RangeToInclusive<usize>> for Vec<T> {
1662 fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut [T] {
1663 IndexMut::index_mut(&mut **self, index)
1667 #[stable(feature = "rust1", since = "1.0.0")]
1668 impl<T> ops::Deref for Vec<T> {
1671 fn deref(&self) -> &[T] {
1673 let p = self.buf.ptr();
1674 assume(!p.is_null());
1675 slice::from_raw_parts(p, self.len)
1680 #[stable(feature = "rust1", since = "1.0.0")]
1681 impl<T> ops::DerefMut for Vec<T> {
1682 fn deref_mut(&mut self) -> &mut [T] {
1684 let ptr = self.buf.ptr();
1685 assume(!ptr.is_null());
1686 slice::from_raw_parts_mut(ptr, self.len)
1691 #[stable(feature = "rust1", since = "1.0.0")]
1692 impl<T> FromIterator<T> for Vec<T> {
1694 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> {
1695 <Self as SpecExtend<T, I::IntoIter>>::from_iter(iter.into_iter())
1699 #[stable(feature = "rust1", since = "1.0.0")]
1700 impl<T> IntoIterator for Vec<T> {
1702 type IntoIter = IntoIter<T>;
1704 /// Creates a consuming iterator, that is, one that moves each value out of
1705 /// the vector (from start to end). The vector cannot be used after calling
1711 /// let v = vec!["a".to_string(), "b".to_string()];
1712 /// for s in v.into_iter() {
1713 /// // s has type String, not &String
1714 /// println!("{}", s);
1718 fn into_iter(mut self) -> IntoIter<T> {
1720 let begin = self.as_mut_ptr();
1721 assume(!begin.is_null());
1722 let end = if mem::size_of::<T>() == 0 {
1723 arith_offset(begin as *const i8, self.len() as isize) as *const T
1725 begin.offset(self.len() as isize) as *const T
1727 let cap = self.buf.cap();
1730 buf: Shared::new_unchecked(begin),
1739 #[stable(feature = "rust1", since = "1.0.0")]
1740 impl<'a, T> IntoIterator for &'a Vec<T> {
1742 type IntoIter = slice::Iter<'a, T>;
1744 fn into_iter(self) -> slice::Iter<'a, T> {
1749 #[stable(feature = "rust1", since = "1.0.0")]
1750 impl<'a, T> IntoIterator for &'a mut Vec<T> {
1751 type Item = &'a mut T;
1752 type IntoIter = slice::IterMut<'a, T>;
1754 fn into_iter(self) -> slice::IterMut<'a, T> {
1759 #[stable(feature = "rust1", since = "1.0.0")]
1760 impl<T> Extend<T> for Vec<T> {
1762 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1763 <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter())
1767 // Specialization trait used for Vec::from_iter and Vec::extend
1768 trait SpecExtend<T, I> {
1769 fn from_iter(iter: I) -> Self;
1770 fn spec_extend(&mut self, iter: I);
1773 impl<T, I> SpecExtend<T, I> for Vec<T>
1774 where I: Iterator<Item=T>,
1776 default fn from_iter(mut iterator: I) -> Self {
1777 // Unroll the first iteration, as the vector is going to be
1778 // expanded on this iteration in every case when the iterable is not
1779 // empty, but the loop in extend_desugared() is not going to see the
1780 // vector being full in the few subsequent loop iterations.
1781 // So we get better branch prediction.
1782 let mut vector = match iterator.next() {
1783 None => return Vec::new(),
1785 let (lower, _) = iterator.size_hint();
1786 let mut vector = Vec::with_capacity(lower.saturating_add(1));
1788 ptr::write(vector.get_unchecked_mut(0), element);
1794 <Vec<T> as SpecExtend<T, I>>::spec_extend(&mut vector, iterator);
1798 default fn spec_extend(&mut self, iter: I) {
1799 self.extend_desugared(iter)
1803 impl<T, I> SpecExtend<T, I> for Vec<T>
1804 where I: TrustedLen<Item=T>,
1806 default fn from_iter(iterator: I) -> Self {
1807 let mut vector = Vec::new();
1808 vector.spec_extend(iterator);
1812 default fn spec_extend(&mut self, iterator: I) {
1813 // This is the case for a TrustedLen iterator.
1814 let (low, high) = iterator.size_hint();
1815 if let Some(high_value) = high {
1816 debug_assert_eq!(low, high_value,
1817 "TrustedLen iterator's size hint is not exact: {:?}",
1820 if let Some(additional) = high {
1821 self.reserve(additional);
1823 let mut ptr = self.as_mut_ptr().offset(self.len() as isize);
1824 let mut local_len = SetLenOnDrop::new(&mut self.len);
1825 for element in iterator {
1826 ptr::write(ptr, element);
1827 ptr = ptr.offset(1);
1828 // NB can't overflow since we would have had to alloc the address space
1829 local_len.increment_len(1);
1833 self.extend_desugared(iterator)
1838 impl<T> SpecExtend<T, IntoIter<T>> for Vec<T> {
1839 fn from_iter(iterator: IntoIter<T>) -> Self {
1840 // A common case is passing a vector into a function which immediately
1841 // re-collects into a vector. We can short circuit this if the IntoIter
1842 // has not been advanced at all.
1843 if iterator.buf.as_ptr() as *const _ == iterator.ptr {
1845 let vec = Vec::from_raw_parts(iterator.buf.as_ptr(),
1848 mem::forget(iterator);
1852 let mut vector = Vec::new();
1853 vector.spec_extend(iterator);
1858 fn spec_extend(&mut self, mut iterator: IntoIter<T>) {
1860 self.append_elements(iterator.as_slice() as _);
1862 iterator.ptr = iterator.end;
1866 impl<'a, T: 'a, I> SpecExtend<&'a T, I> for Vec<T>
1867 where I: Iterator<Item=&'a T>,
1870 default fn from_iter(iterator: I) -> Self {
1871 SpecExtend::from_iter(iterator.cloned())
1874 default fn spec_extend(&mut self, iterator: I) {
1875 self.spec_extend(iterator.cloned())
1879 impl<'a, T: 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T>
1882 fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
1883 let slice = iterator.as_slice();
1884 self.reserve(slice.len());
1886 let len = self.len();
1887 self.set_len(len + slice.len());
1888 self.get_unchecked_mut(len..).copy_from_slice(slice);
1894 fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
1895 // This is the case for a general iterator.
1897 // This function should be the moral equivalent of:
1899 // for item in iterator {
1902 while let Some(element) = iterator.next() {
1903 let len = self.len();
1904 if len == self.capacity() {
1905 let (lower, _) = iterator.size_hint();
1906 self.reserve(lower.saturating_add(1));
1909 ptr::write(self.get_unchecked_mut(len), element);
1910 // NB can't overflow since we would have had to alloc the address space
1911 self.set_len(len + 1);
1916 /// Creates a splicing iterator that replaces the specified range in the vector
1917 /// with the given `replace_with` iterator and yields the removed items.
1918 /// `replace_with` does not need to be the same length as `range`.
1920 /// Note 1: The element range is removed even if the iterator is not
1921 /// consumed until the end.
1923 /// Note 2: It is unspecified how many elements are removed from the vector,
1924 /// if the `Splice` value is leaked.
1926 /// Note 3: The input iterator `replace_with` is only consumed
1927 /// when the `Splice` value is dropped.
1929 /// Note 4: This is optimal if:
1931 /// * The tail (elements in the vector after `range`) is empty,
1932 /// * or `replace_with` yields fewer elements than `range`’s length
1933 /// * or the lower bound of its `size_hint()` is exact.
1935 /// Otherwise, a temporary vector is allocated and the tail is moved twice.
1939 /// Panics if the starting point is greater than the end point or if
1940 /// the end point is greater than the length of the vector.
1945 /// #![feature(splice)]
1946 /// let mut v = vec![1, 2, 3];
1947 /// let new = [7, 8];
1948 /// let u: Vec<_> = v.splice(..2, new.iter().cloned()).collect();
1949 /// assert_eq!(v, &[7, 8, 3]);
1950 /// assert_eq!(u, &[1, 2]);
1953 #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
1954 pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<I::IntoIter>
1955 where R: RangeArgument<usize>, I: IntoIterator<Item=T>
1958 drain: self.drain(range),
1959 replace_with: replace_with.into_iter(),
1963 /// Creates an iterator which uses a closure to determine if an element should be removed.
1965 /// If the closure returns true, then the element is removed and yielded.
1966 /// If the closure returns false, it will try again, and call the closure
1967 /// on the next element, seeing if it passes the test.
1969 /// Using this method is equivalent to the following code:
1972 /// # let some_predicate = |x: &mut i32| { *x == 2 };
1973 /// # let mut vec = vec![1, 2, 3, 4, 5];
1975 /// while i != vec.len() {
1976 /// if some_predicate(&mut vec[i]) {
1977 /// let val = vec.remove(i);
1978 /// // your code here
1984 /// But `drain_filter` is easier to use. `drain_filter` is also more efficient,
1985 /// because it can backshift the elements of the array in bulk.
1987 /// Note that `drain_filter` also lets you mutate every element in the filter closure,
1988 /// regardless of whether you choose to keep or remove it.
1993 /// Splitting an array into evens and odds, reusing the original allocation:
1996 /// #![feature(drain_filter)]
1997 /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];
1999 /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
2000 /// let odds = numbers;
2002 /// assert_eq!(evens, vec![2, 4, 6, 8, 14]);
2003 /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);
2005 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2006 pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<T, F>
2007 where F: FnMut(&mut T) -> bool,
2009 let old_len = self.len();
2011 // Guard against us getting leaked (leak amplification)
2012 unsafe { self.set_len(0); }
2024 /// Extend implementation that copies elements out of references before pushing them onto the Vec.
2026 /// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to
2027 /// append the entire slice at once.
2029 /// [`copy_from_slice`]: ../../std/primitive.slice.html#method.copy_from_slice
2030 #[stable(feature = "extend_ref", since = "1.2.0")]
2031 impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> {
2032 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
2033 self.spec_extend(iter.into_iter())
2037 macro_rules! __impl_slice_eq1 {
2038 ($Lhs: ty, $Rhs: ty) => {
2039 __impl_slice_eq1! { $Lhs, $Rhs, Sized }
2041 ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
2042 #[stable(feature = "rust1", since = "1.0.0")]
2043 impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
2045 fn eq(&self, other: &$Rhs) -> bool { self[..] == other[..] }
2047 fn ne(&self, other: &$Rhs) -> bool { self[..] != other[..] }
2052 __impl_slice_eq1! { Vec<A>, Vec<B> }
2053 __impl_slice_eq1! { Vec<A>, &'b [B] }
2054 __impl_slice_eq1! { Vec<A>, &'b mut [B] }
2055 __impl_slice_eq1! { Cow<'a, [A]>, &'b [B], Clone }
2056 __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B], Clone }
2057 __impl_slice_eq1! { Cow<'a, [A]>, Vec<B>, Clone }
2059 macro_rules! array_impls {
2062 // NOTE: some less important impls are omitted to reduce code bloat
2063 __impl_slice_eq1! { Vec<A>, [B; $N] }
2064 __impl_slice_eq1! { Vec<A>, &'b [B; $N] }
2065 // __impl_slice_eq1! { Vec<A>, &'b mut [B; $N] }
2066 // __impl_slice_eq1! { Cow<'a, [A]>, [B; $N], Clone }
2067 // __impl_slice_eq1! { Cow<'a, [A]>, &'b [B; $N], Clone }
2068 // __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
2075 10 11 12 13 14 15 16 17 18 19
2076 20 21 22 23 24 25 26 27 28 29
2080 /// Implements comparison of vectors, lexicographically.
2081 #[stable(feature = "rust1", since = "1.0.0")]
2082 impl<T: PartialOrd> PartialOrd for Vec<T> {
2084 fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> {
2085 PartialOrd::partial_cmp(&**self, &**other)
2089 #[stable(feature = "rust1", since = "1.0.0")]
2090 impl<T: Eq> Eq for Vec<T> {}
2092 /// Implements ordering of vectors, lexicographically.
2093 #[stable(feature = "rust1", since = "1.0.0")]
2094 impl<T: Ord> Ord for Vec<T> {
2096 fn cmp(&self, other: &Vec<T>) -> Ordering {
2097 Ord::cmp(&**self, &**other)
2101 #[stable(feature = "rust1", since = "1.0.0")]
2102 unsafe impl<#[may_dangle] T> Drop for Vec<T> {
2103 fn drop(&mut self) {
2106 ptr::drop_in_place(&mut self[..]);
2108 // RawVec handles deallocation
2112 #[stable(feature = "rust1", since = "1.0.0")]
2113 impl<T> Default for Vec<T> {
2114 /// Creates an empty `Vec<T>`.
2115 fn default() -> Vec<T> {
2120 #[stable(feature = "rust1", since = "1.0.0")]
2121 impl<T: fmt::Debug> fmt::Debug for Vec<T> {
2122 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2123 fmt::Debug::fmt(&**self, f)
2127 #[stable(feature = "rust1", since = "1.0.0")]
2128 impl<T> AsRef<Vec<T>> for Vec<T> {
2129 fn as_ref(&self) -> &Vec<T> {
2134 #[stable(feature = "vec_as_mut", since = "1.5.0")]
2135 impl<T> AsMut<Vec<T>> for Vec<T> {
2136 fn as_mut(&mut self) -> &mut Vec<T> {
2141 #[stable(feature = "rust1", since = "1.0.0")]
2142 impl<T> AsRef<[T]> for Vec<T> {
2143 fn as_ref(&self) -> &[T] {
2148 #[stable(feature = "vec_as_mut", since = "1.5.0")]
2149 impl<T> AsMut<[T]> for Vec<T> {
2150 fn as_mut(&mut self) -> &mut [T] {
2155 #[stable(feature = "rust1", since = "1.0.0")]
2156 impl<'a, T: Clone> From<&'a [T]> for Vec<T> {
2158 fn from(s: &'a [T]) -> Vec<T> {
2162 fn from(s: &'a [T]) -> Vec<T> {
2167 #[stable(feature = "vec_from_mut", since = "1.19.0")]
2168 impl<'a, T: Clone> From<&'a mut [T]> for Vec<T> {
2170 fn from(s: &'a mut [T]) -> Vec<T> {
2174 fn from(s: &'a mut [T]) -> Vec<T> {
2179 #[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
2180 impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where [T]: ToOwned<Owned=Vec<T>> {
2181 fn from(s: Cow<'a, [T]>) -> Vec<T> {
2186 // note: test pulls in libstd, which causes errors here
2188 #[stable(feature = "vec_from_box", since = "1.18.0")]
2189 impl<T> From<Box<[T]>> for Vec<T> {
2190 fn from(s: Box<[T]>) -> Vec<T> {
2195 // note: test pulls in libstd, which causes errors here
2197 #[stable(feature = "box_from_vec", since = "1.20.0")]
2198 impl<T> From<Vec<T>> for Box<[T]> {
2199 fn from(v: Vec<T>) -> Box<[T]> {
2200 v.into_boxed_slice()
2204 #[stable(feature = "rust1", since = "1.0.0")]
2205 impl<'a> From<&'a str> for Vec<u8> {
2206 fn from(s: &'a str) -> Vec<u8> {
2207 From::from(s.as_bytes())
2211 ////////////////////////////////////////////////////////////////////////////////
2213 ////////////////////////////////////////////////////////////////////////////////
2215 #[stable(feature = "cow_from_vec", since = "1.8.0")]
2216 impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> {
2217 fn from(s: &'a [T]) -> Cow<'a, [T]> {
2222 #[stable(feature = "cow_from_vec", since = "1.8.0")]
2223 impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> {
2224 fn from(v: Vec<T>) -> Cow<'a, [T]> {
2229 #[stable(feature = "rust1", since = "1.0.0")]
2230 impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone {
2231 fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {
2232 Cow::Owned(FromIterator::from_iter(it))
2236 ////////////////////////////////////////////////////////////////////////////////
2238 ////////////////////////////////////////////////////////////////////////////////
2240 /// An iterator that moves out of a vector.
2242 /// This `struct` is created by the `into_iter` method on [`Vec`][`Vec`] (provided
2243 /// by the [`IntoIterator`] trait).
2245 /// [`Vec`]: struct.Vec.html
2246 /// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html
2247 #[stable(feature = "rust1", since = "1.0.0")]
2248 pub struct IntoIter<T> {
2255 #[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
2256 impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
2257 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2258 f.debug_tuple("IntoIter")
2259 .field(&self.as_slice())
2264 impl<T> IntoIter<T> {
2265 /// Returns the remaining items of this iterator as a slice.
2270 /// let vec = vec!['a', 'b', 'c'];
2271 /// let mut into_iter = vec.into_iter();
2272 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
2273 /// let _ = into_iter.next().unwrap();
2274 /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
2276 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
2277 pub fn as_slice(&self) -> &[T] {
2279 slice::from_raw_parts(self.ptr, self.len())
2283 /// Returns the remaining items of this iterator as a mutable slice.
2288 /// let vec = vec!['a', 'b', 'c'];
2289 /// let mut into_iter = vec.into_iter();
2290 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
2291 /// into_iter.as_mut_slice()[2] = 'z';
2292 /// assert_eq!(into_iter.next().unwrap(), 'a');
2293 /// assert_eq!(into_iter.next().unwrap(), 'b');
2294 /// assert_eq!(into_iter.next().unwrap(), 'z');
2296 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
2297 pub fn as_mut_slice(&mut self) -> &mut [T] {
2299 slice::from_raw_parts_mut(self.ptr as *mut T, self.len())
2304 #[stable(feature = "rust1", since = "1.0.0")]
2305 unsafe impl<T: Send> Send for IntoIter<T> {}
2306 #[stable(feature = "rust1", since = "1.0.0")]
2307 unsafe impl<T: Sync> Sync for IntoIter<T> {}
2309 #[stable(feature = "rust1", since = "1.0.0")]
2310 impl<T> Iterator for IntoIter<T> {
2314 fn next(&mut self) -> Option<T> {
2316 if self.ptr as *const _ == self.end {
2319 if mem::size_of::<T>() == 0 {
2320 // purposefully don't use 'ptr.offset' because for
2321 // vectors with 0-size elements this would return the
2323 self.ptr = arith_offset(self.ptr as *const i8, 1) as *mut T;
2325 // Use a non-null pointer value
2326 // (self.ptr might be null because of wrapping)
2327 Some(ptr::read(1 as *mut T))
2330 self.ptr = self.ptr.offset(1);
2332 Some(ptr::read(old))
2339 fn size_hint(&self) -> (usize, Option<usize>) {
2340 let exact = match self.ptr.offset_to(self.end) {
2341 Some(x) => x as usize,
2342 None => (self.end as usize).wrapping_sub(self.ptr as usize),
2344 (exact, Some(exact))
2348 fn count(self) -> usize {
2353 #[stable(feature = "rust1", since = "1.0.0")]
2354 impl<T> DoubleEndedIterator for IntoIter<T> {
2356 fn next_back(&mut self) -> Option<T> {
2358 if self.end == self.ptr {
2361 if mem::size_of::<T>() == 0 {
2362 // See above for why 'ptr.offset' isn't used
2363 self.end = arith_offset(self.end as *const i8, -1) as *mut T;
2365 // Use a non-null pointer value
2366 // (self.end might be null because of wrapping)
2367 Some(ptr::read(1 as *mut T))
2369 self.end = self.end.offset(-1);
2371 Some(ptr::read(self.end))
2378 #[stable(feature = "rust1", since = "1.0.0")]
2379 impl<T> ExactSizeIterator for IntoIter<T> {
2380 fn is_empty(&self) -> bool {
2381 self.ptr == self.end
2385 #[unstable(feature = "fused", issue = "35602")]
2386 impl<T> FusedIterator for IntoIter<T> {}
2388 #[unstable(feature = "trusted_len", issue = "37572")]
2389 unsafe impl<T> TrustedLen for IntoIter<T> {}
2391 #[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
2392 impl<T: Clone> Clone for IntoIter<T> {
2393 fn clone(&self) -> IntoIter<T> {
2394 self.as_slice().to_owned().into_iter()
2398 #[stable(feature = "rust1", since = "1.0.0")]
2399 unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
2400 fn drop(&mut self) {
2401 // destroy the remaining elements
2402 for _x in self.by_ref() {}
2404 // RawVec handles deallocation
2405 let _ = unsafe { RawVec::from_raw_parts(self.buf.as_ptr(), self.cap) };
2409 /// A draining iterator for `Vec<T>`.
2411 /// This `struct` is created by the [`drain`] method on [`Vec`].
2413 /// [`drain`]: struct.Vec.html#method.drain
2414 /// [`Vec`]: struct.Vec.html
2415 #[stable(feature = "drain", since = "1.6.0")]
2416 pub struct Drain<'a, T: 'a> {
2417 /// Index of tail to preserve
2421 /// Current remaining range to remove
2422 iter: slice::Iter<'a, T>,
2423 vec: Shared<Vec<T>>,
2426 #[stable(feature = "collection_debug", since = "1.17.0")]
2427 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
2428 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2429 f.debug_tuple("Drain")
2430 .field(&self.iter.as_slice())
2435 #[stable(feature = "drain", since = "1.6.0")]
2436 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
2437 #[stable(feature = "drain", since = "1.6.0")]
2438 unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
2440 #[stable(feature = "drain", since = "1.6.0")]
2441 impl<'a, T> Iterator for Drain<'a, T> {
2445 fn next(&mut self) -> Option<T> {
2446 self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
2449 fn size_hint(&self) -> (usize, Option<usize>) {
2450 self.iter.size_hint()
2454 #[stable(feature = "drain", since = "1.6.0")]
2455 impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
2457 fn next_back(&mut self) -> Option<T> {
2458 self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
2462 #[stable(feature = "drain", since = "1.6.0")]
2463 impl<'a, T> Drop for Drain<'a, T> {
2464 fn drop(&mut self) {
2465 // exhaust self first
2466 while let Some(_) = self.next() {}
2468 if self.tail_len > 0 {
2470 let source_vec = self.vec.as_mut();
2471 // memmove back untouched tail, update to new length
2472 let start = source_vec.len();
2473 let tail = self.tail_start;
2474 let src = source_vec.as_ptr().offset(tail as isize);
2475 let dst = source_vec.as_mut_ptr().offset(start as isize);
2476 ptr::copy(src, dst, self.tail_len);
2477 source_vec.set_len(start + self.tail_len);
2484 #[stable(feature = "drain", since = "1.6.0")]
2485 impl<'a, T> ExactSizeIterator for Drain<'a, T> {
2486 fn is_empty(&self) -> bool {
2487 self.iter.is_empty()
2491 #[unstable(feature = "fused", issue = "35602")]
2492 impl<'a, T> FusedIterator for Drain<'a, T> {}
2494 /// A place for insertion at the back of a `Vec`.
2496 /// See [`Vec::place_back`](struct.Vec.html#method.place_back) for details.
2497 #[must_use = "places do nothing unless written to with `<-` syntax"]
2498 #[unstable(feature = "collection_placement",
2499 reason = "struct name and placement protocol are subject to change",
2502 pub struct PlaceBack<'a, T: 'a> {
2503 vec: &'a mut Vec<T>,
2506 #[unstable(feature = "collection_placement",
2507 reason = "placement protocol is subject to change",
2509 impl<'a, T> Placer<T> for PlaceBack<'a, T> {
2510 type Place = PlaceBack<'a, T>;
2512 fn make_place(self) -> Self {
2513 // This will panic or abort if we would allocate > isize::MAX bytes
2514 // or if the length increment would overflow for zero-sized types.
2515 if self.vec.len == self.vec.buf.cap() {
2516 self.vec.buf.double();
2522 #[unstable(feature = "collection_placement",
2523 reason = "placement protocol is subject to change",
2525 impl<'a, T> Place<T> for PlaceBack<'a, T> {
2526 fn pointer(&mut self) -> *mut T {
2527 unsafe { self.vec.as_mut_ptr().offset(self.vec.len as isize) }
2531 #[unstable(feature = "collection_placement",
2532 reason = "placement protocol is subject to change",
2534 impl<'a, T> InPlace<T> for PlaceBack<'a, T> {
2535 type Owner = &'a mut T;
2537 unsafe fn finalize(mut self) -> &'a mut T {
2538 let ptr = self.pointer();
2545 /// A splicing iterator for `Vec`.
2547 /// This struct is created by the [`splice()`] method on [`Vec`]. See its
2548 /// documentation for more.
2550 /// [`splice()`]: struct.Vec.html#method.splice
2551 /// [`Vec`]: struct.Vec.html
2553 #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
2554 pub struct Splice<'a, I: Iterator + 'a> {
2555 drain: Drain<'a, I::Item>,
2559 #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
2560 impl<'a, I: Iterator> Iterator for Splice<'a, I> {
2561 type Item = I::Item;
2563 fn next(&mut self) -> Option<Self::Item> {
2567 fn size_hint(&self) -> (usize, Option<usize>) {
2568 self.drain.size_hint()
2572 #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
2573 impl<'a, I: Iterator> DoubleEndedIterator for Splice<'a, I> {
2574 fn next_back(&mut self) -> Option<Self::Item> {
2575 self.drain.next_back()
2579 #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
2580 impl<'a, I: Iterator> ExactSizeIterator for Splice<'a, I> {}
2583 #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
2584 impl<'a, I: Iterator> Drop for Splice<'a, I> {
2585 fn drop(&mut self) {
2586 // exhaust drain first
2587 while let Some(_) = self.drain.next() {}
2591 if self.drain.tail_len == 0 {
2592 self.drain.vec.as_mut().extend(self.replace_with.by_ref());
2596 // First fill the range left by drain().
2597 if !self.drain.fill(&mut self.replace_with) {
2601 // There may be more elements. Use the lower bound as an estimate.
2602 // FIXME: Is the upper bound a better guess? Or something else?
2603 let (lower_bound, _upper_bound) = self.replace_with.size_hint();
2604 if lower_bound > 0 {
2605 self.drain.move_tail(lower_bound);
2606 if !self.drain.fill(&mut self.replace_with) {
2611 // Collect any remaining elements.
2612 // This is a zero-length vector which does not allocate if `lower_bound` was exact.
2613 let mut collected = self.replace_with.by_ref().collect::<Vec<I::Item>>().into_iter();
2614 // Now we have an exact count.
2615 if collected.len() > 0 {
2616 self.drain.move_tail(collected.len());
2617 let filled = self.drain.fill(&mut collected);
2618 debug_assert!(filled);
2619 debug_assert_eq!(collected.len(), 0);
2622 // Let `Drain::drop` move the tail back if necessary and restore `vec.len`.
2626 /// Private helper methods for `Splice::drop`
2627 impl<'a, T> Drain<'a, T> {
2628 /// The range from `self.vec.len` to `self.tail_start` contains elements
2629 /// that have been moved out.
2630 /// Fill that range as much as possible with new elements from the `replace_with` iterator.
2631 /// Return whether we filled the entire range. (`replace_with.next()` didn’t return `None`.)
2632 unsafe fn fill<I: Iterator<Item=T>>(&mut self, replace_with: &mut I) -> bool {
2633 let vec = self.vec.as_mut();
2634 let range_start = vec.len;
2635 let range_end = self.tail_start;
2636 let range_slice = slice::from_raw_parts_mut(
2637 vec.as_mut_ptr().offset(range_start as isize),
2638 range_end - range_start);
2640 for place in range_slice {
2641 if let Some(new_item) = replace_with.next() {
2642 ptr::write(place, new_item);
2651 /// Make room for inserting more elements before the tail.
2652 unsafe fn move_tail(&mut self, extra_capacity: usize) {
2653 let vec = self.vec.as_mut();
2654 let used_capacity = self.tail_start + self.tail_len;
2655 vec.buf.reserve(used_capacity, extra_capacity);
2657 let new_tail_start = self.tail_start + extra_capacity;
2658 let src = vec.as_ptr().offset(self.tail_start as isize);
2659 let dst = vec.as_mut_ptr().offset(new_tail_start as isize);
2660 ptr::copy(src, dst, self.tail_len);
2661 self.tail_start = new_tail_start;
2665 /// An iterator produced by calling `drain_filter` on Vec.
2666 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2668 pub struct DrainFilter<'a, T: 'a, F>
2669 where F: FnMut(&mut T) -> bool,
2671 vec: &'a mut Vec<T>,
2678 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2679 impl<'a, T, F> Iterator for DrainFilter<'a, T, F>
2680 where F: FnMut(&mut T) -> bool,
2684 fn next(&mut self) -> Option<T> {
2686 while self.idx != self.old_len {
2689 let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
2690 if (self.pred)(&mut v[i]) {
2692 return Some(ptr::read(&v[i]));
2693 } else if self.del > 0 {
2694 v.swap(i - self.del, i);
2701 fn size_hint(&self) -> (usize, Option<usize>) {
2702 (0, Some(self.old_len - self.idx))
2706 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2707 impl<'a, T, F> Drop for DrainFilter<'a, T, F>
2708 where F: FnMut(&mut T) -> bool,
2710 fn drop(&mut self) {
2711 for _ in self.by_ref() { }
2714 self.vec.set_len(self.old_len - self.del);