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
::{self, 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
;
76 use core
::ops
::Bound
::{Excluded, Included, Unbounded}
;
77 use core
::ops
::{Index, IndexMut, RangeBounds}
;
80 use core
::ptr
::NonNull
;
83 use collections
::CollectionAllocErr
;
89 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
94 /// let mut vec = Vec::new();
98 /// assert_eq!(vec.len(), 2);
99 /// assert_eq!(vec[0], 1);
101 /// assert_eq!(vec.pop(), Some(2));
102 /// assert_eq!(vec.len(), 1);
105 /// assert_eq!(vec[0], 7);
107 /// vec.extend([1, 2, 3].iter().cloned());
110 /// println!("{}", x);
112 /// assert_eq!(vec, [7, 1, 2, 3]);
115 /// The [`vec!`] macro is provided to make initialization more convenient:
118 /// let mut vec = vec![1, 2, 3];
120 /// assert_eq!(vec, [1, 2, 3, 4]);
123 /// It can also initialize each element of a `Vec<T>` with a given value:
126 /// let vec = vec![0; 5];
127 /// assert_eq!(vec, [0, 0, 0, 0, 0]);
130 /// Use a `Vec<T>` as an efficient stack:
133 /// let mut stack = Vec::new();
139 /// while let Some(top) = stack.pop() {
140 /// // Prints 3, 2, 1
141 /// println!("{}", top);
147 /// The `Vec` type allows to access values by index, because it implements the
148 /// [`Index`] trait. An example will be more explicit:
151 /// let v = vec![0, 2, 4, 6];
152 /// println!("{}", v[1]); // it will display '2'
155 /// However be careful: if you try to access an index which isn't in the `Vec`,
156 /// your software will panic! You cannot do this:
159 /// let v = vec![0, 2, 4, 6];
160 /// println!("{}", v[6]); // it will panic!
163 /// In conclusion: always check if the index you want to get really exists
168 /// A `Vec` can be mutable. Slices, on the other hand, are read-only objects.
169 /// To get a slice, use `&`. Example:
172 /// fn read_slice(slice: &[usize]) {
176 /// let v = vec![0, 1];
179 /// // ... and that's all!
180 /// // you can also do it like this:
181 /// let x : &[usize] = &v;
184 /// In Rust, it's more common to pass slices as arguments rather than vectors
185 /// when you just want to provide a read access. The same goes for [`String`] and
188 /// # Capacity and reallocation
190 /// The capacity of a vector is the amount of space allocated for any future
191 /// elements that will be added onto the vector. This is not to be confused with
192 /// the *length* of a vector, which specifies the number of actual elements
193 /// within the vector. If a vector's length exceeds its capacity, its capacity
194 /// will automatically be increased, but its elements will have to be
197 /// For example, a vector with capacity 10 and length 0 would be an empty vector
198 /// with space for 10 more elements. Pushing 10 or fewer elements onto the
199 /// vector will not change its capacity or cause reallocation to occur. However,
200 /// if the vector's length is increased to 11, it will have to reallocate, which
201 /// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`]
202 /// whenever possible to specify how big the vector is expected to get.
206 /// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees
207 /// about its design. This ensures that it's as low-overhead as possible in
208 /// the general case, and can be correctly manipulated in primitive ways
209 /// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`.
210 /// If additional type parameters are added (e.g. to support custom allocators),
211 /// overriding their defaults may change the behavior.
213 /// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length)
214 /// triplet. No more, no less. The order of these fields is completely
215 /// unspecified, and you should use the appropriate methods to modify these.
216 /// The pointer will never be null, so this type is null-pointer-optimized.
218 /// However, the pointer may not actually point to allocated memory. In particular,
219 /// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`],
220 /// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`]
221 /// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized
222 /// types inside a `Vec`, it will not allocate space for them. *Note that in this case
223 /// the `Vec` may not report a [`capacity`] of 0*. `Vec` will allocate if and only
224 /// if [`mem::size_of::<T>`]`() * capacity() > 0`. In general, `Vec`'s allocation
225 /// details are very subtle — if you intend to allocate memory using a `Vec`
226 /// and use it for something else (either to pass to unsafe code, or to build your
227 /// own memory-backed collection), be sure to deallocate this memory by using
228 /// `from_raw_parts` to recover the `Vec` and then dropping it.
230 /// If a `Vec` *has* allocated memory, then the memory it points to is on the heap
231 /// (as defined by the allocator Rust is configured to use by default), and its
232 /// pointer points to [`len`] initialized, contiguous elements in order (what
233 /// you would see if you coerced it to a slice), followed by [`capacity`]` -
234 /// `[`len`] logically uninitialized, contiguous elements.
236 /// `Vec` will never perform a "small optimization" where elements are actually
237 /// stored on the stack for two reasons:
239 /// * It would make it more difficult for unsafe code to correctly manipulate
240 /// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were
241 /// only moved, and it would be more difficult to determine if a `Vec` had
242 /// actually allocated memory.
244 /// * It would penalize the general case, incurring an additional branch
247 /// `Vec` will never automatically shrink itself, even if completely empty. This
248 /// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec`
249 /// and then filling it back up to the same [`len`] should incur no calls to
250 /// the allocator. If you wish to free up unused memory, use
251 /// [`shrink_to_fit`][`shrink_to_fit`].
253 /// [`push`] and [`insert`] will never (re)allocate if the reported capacity is
254 /// sufficient. [`push`] and [`insert`] *will* (re)allocate if
255 /// [`len`]` == `[`capacity`]. That is, the reported capacity is completely
256 /// accurate, and can be relied on. It can even be used to manually free the memory
257 /// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even
258 /// when not necessary.
260 /// `Vec` does not guarantee any particular growth strategy when reallocating
261 /// when full, nor when [`reserve`] is called. The current strategy is basic
262 /// and it may prove desirable to use a non-constant growth factor. Whatever
263 /// strategy is used will of course guarantee `O(1)` amortized [`push`].
265 /// `vec![x; n]`, `vec![a, b, c, d]`, and
266 /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
267 /// with exactly the requested capacity. If [`len`]` == `[`capacity`],
268 /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
269 /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
271 /// `Vec` will not specifically overwrite any data that is removed from it,
272 /// but also won't specifically preserve it. Its uninitialized memory is
273 /// scratch space that it may use however it wants. It will generally just do
274 /// whatever is most efficient or otherwise easy to implement. Do not rely on
275 /// removed data to be erased for security purposes. Even if you drop a `Vec`, its
276 /// buffer may simply be reused by another `Vec`. Even if you zero a `Vec`'s memory
277 /// first, that may not actually happen because the optimizer does not consider
278 /// this a side-effect that must be preserved. There is one case which we will
279 /// not break, however: using `unsafe` code to write to the excess capacity,
280 /// and then increasing the length to match, is always valid.
282 /// `Vec` does not currently guarantee the order in which elements are dropped.
283 /// The order has changed in the past and may change again.
285 /// [`vec!`]: ../../std/macro.vec.html
286 /// [`Index`]: ../../std/ops/trait.Index.html
287 /// [`String`]: ../../std/string/struct.String.html
288 /// [`&str`]: ../../std/primitive.str.html
289 /// [`Vec::with_capacity`]: ../../std/vec/struct.Vec.html#method.with_capacity
290 /// [`Vec::new`]: ../../std/vec/struct.Vec.html#method.new
291 /// [`shrink_to_fit`]: ../../std/vec/struct.Vec.html#method.shrink_to_fit
292 /// [`capacity`]: ../../std/vec/struct.Vec.html#method.capacity
293 /// [`mem::size_of::<T>`]: ../../std/mem/fn.size_of.html
294 /// [`len`]: ../../std/vec/struct.Vec.html#method.len
295 /// [`push`]: ../../std/vec/struct.Vec.html#method.push
296 /// [`insert`]: ../../std/vec/struct.Vec.html#method.insert
297 /// [`reserve`]: ../../std/vec/struct.Vec.html#method.reserve
298 /// [owned slice]: ../../std/boxed/struct.Box.html
299 #[stable(feature = "rust1", since = "1.0.0")]
305 ////////////////////////////////////////////////////////////////////////////////
307 ////////////////////////////////////////////////////////////////////////////////
310 /// Constructs a new, empty `Vec<T>`.
312 /// The vector will not allocate until elements are pushed onto it.
317 /// # #![allow(unused_mut)]
318 /// let mut vec: Vec<i32> = Vec::new();
321 #[stable(feature = "rust1", since = "1.0.0")]
322 #[rustc_const_unstable(feature = "const_vec_new")]
323 pub const fn new() -> Vec
<T
> {
330 /// Constructs a new, empty `Vec<T>` with the specified capacity.
332 /// The vector will be able to hold exactly `capacity` elements without
333 /// reallocating. If `capacity` is 0, the vector will not allocate.
335 /// It is important to note that although the returned vector has the
336 /// *capacity* specified, the vector will have a zero *length*. For an
337 /// explanation of the difference between length and capacity, see
338 /// *[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 /// Tries to reserve capacity for at least `additional` more elements to be inserted
493 /// in the given `Vec<T>`. The collection may reserve more space to avoid
494 /// frequent reallocations. After calling `reserve`, capacity will be
495 /// greater than or equal to `self.len() + additional`. Does nothing if
496 /// capacity is already sufficient.
500 /// If the capacity overflows, or the allocator reports a failure, then an error
506 /// #![feature(try_reserve)]
507 /// use std::collections::CollectionAllocErr;
509 /// fn process_data(data: &[u32]) -> Result<Vec<u32>, CollectionAllocErr> {
510 /// let mut output = Vec::new();
512 /// // Pre-reserve the memory, exiting if we can't
513 /// output.try_reserve(data.len())?;
515 /// // Now we know this can't OOM in the middle of our complex work
516 /// output.extend(data.iter().map(|&val| {
517 /// val * 2 + 5 // very complicated
522 /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
524 #[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
525 pub fn try_reserve(&mut self, additional
: usize) -> Result
<(), CollectionAllocErr
> {
526 self.buf
.try_reserve(self.len
, additional
)
529 /// Tries to reserves the minimum capacity for exactly `additional` more elements to
530 /// be inserted in the given `Vec<T>`. After calling `reserve_exact`,
531 /// capacity will be greater than or equal to `self.len() + additional`.
532 /// Does nothing if the capacity is already sufficient.
534 /// Note that the allocator may give the collection more space than it
535 /// requests. Therefore capacity can not be relied upon to be precisely
536 /// minimal. Prefer `reserve` if future insertions are expected.
540 /// If the capacity overflows, or the allocator reports a failure, then an error
546 /// #![feature(try_reserve)]
547 /// use std::collections::CollectionAllocErr;
549 /// fn process_data(data: &[u32]) -> Result<Vec<u32>, CollectionAllocErr> {
550 /// let mut output = Vec::new();
552 /// // Pre-reserve the memory, exiting if we can't
553 /// output.try_reserve(data.len())?;
555 /// // Now we know this can't OOM in the middle of our complex work
556 /// output.extend(data.iter().map(|&val| {
557 /// val * 2 + 5 // very complicated
562 /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
564 #[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
565 pub fn try_reserve_exact(&mut self, additional
: usize) -> Result
<(), CollectionAllocErr
> {
566 self.buf
.try_reserve_exact(self.len
, additional
)
569 /// Shrinks the capacity of the vector as much as possible.
571 /// It will drop down as close as possible to the length but the allocator
572 /// may still inform the vector that there is space for a few more elements.
577 /// let mut vec = Vec::with_capacity(10);
578 /// vec.extend([1, 2, 3].iter().cloned());
579 /// assert_eq!(vec.capacity(), 10);
580 /// vec.shrink_to_fit();
581 /// assert!(vec.capacity() >= 3);
583 #[stable(feature = "rust1", since = "1.0.0")]
584 pub fn shrink_to_fit(&mut self) {
585 if self.capacity() != self.len
{
586 self.buf
.shrink_to_fit(self.len
);
590 /// Shrinks the capacity of the vector with a lower bound.
592 /// The capacity will remain at least as large as both the length
593 /// and the supplied value.
595 /// Panics if the current capacity is smaller than the supplied
596 /// minimum capacity.
601 /// #![feature(shrink_to)]
602 /// let mut vec = Vec::with_capacity(10);
603 /// vec.extend([1, 2, 3].iter().cloned());
604 /// assert_eq!(vec.capacity(), 10);
605 /// vec.shrink_to(4);
606 /// assert!(vec.capacity() >= 4);
607 /// vec.shrink_to(0);
608 /// assert!(vec.capacity() >= 3);
610 #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
611 pub fn shrink_to(&mut self, min_capacity
: usize) {
612 self.buf
.shrink_to_fit(cmp
::max(self.len
, min_capacity
));
615 /// Converts the vector into [`Box<[T]>`][owned slice].
617 /// Note that this will drop any excess capacity.
619 /// [owned slice]: ../../std/boxed/struct.Box.html
624 /// let v = vec![1, 2, 3];
626 /// let slice = v.into_boxed_slice();
629 /// Any excess capacity is removed:
632 /// let mut vec = Vec::with_capacity(10);
633 /// vec.extend([1, 2, 3].iter().cloned());
635 /// assert_eq!(vec.capacity(), 10);
636 /// let slice = vec.into_boxed_slice();
637 /// assert_eq!(slice.into_vec().capacity(), 3);
639 #[stable(feature = "rust1", since = "1.0.0")]
640 pub fn into_boxed_slice(mut self) -> Box
<[T
]> {
642 self.shrink_to_fit();
643 let buf
= ptr
::read(&self.buf
);
649 /// Shortens the vector, keeping the first `len` elements and dropping
652 /// If `len` is greater than the vector's current length, this has no
655 /// The [`drain`] method can emulate `truncate`, but causes the excess
656 /// elements to be returned instead of dropped.
658 /// Note that this method has no effect on the allocated capacity
663 /// Truncating a five element vector to two elements:
666 /// let mut vec = vec![1, 2, 3, 4, 5];
668 /// assert_eq!(vec, [1, 2]);
671 /// No truncation occurs when `len` is greater than the vector's current
675 /// let mut vec = vec![1, 2, 3];
677 /// assert_eq!(vec, [1, 2, 3]);
680 /// Truncating when `len == 0` is equivalent to calling the [`clear`]
684 /// let mut vec = vec![1, 2, 3];
686 /// assert_eq!(vec, []);
689 /// [`clear`]: #method.clear
690 /// [`drain`]: #method.drain
691 #[stable(feature = "rust1", since = "1.0.0")]
692 pub fn truncate(&mut self, len
: usize) {
693 let current_len
= self.len
;
695 let mut ptr
= self.as_mut_ptr().add(self.len
);
696 // Set the final length at the end, keeping in mind that
697 // dropping an element might panic. Works around a missed
698 // optimization, as seen in the following issue:
699 // https://github.com/rust-lang/rust/issues/51802
700 let mut local_len
= SetLenOnDrop
::new(&mut self.len
);
702 // drop any extra elements
703 for _
in len
..current_len
{
704 local_len
.decrement_len(1);
705 ptr
= ptr
.offset(-1);
706 ptr
::drop_in_place(ptr
);
711 /// Extracts a slice containing the entire vector.
713 /// Equivalent to `&s[..]`.
718 /// use std::io::{self, Write};
719 /// let buffer = vec![1, 2, 3, 5, 8];
720 /// io::sink().write(buffer.as_slice()).unwrap();
723 #[stable(feature = "vec_as_slice", since = "1.7.0")]
724 pub fn as_slice(&self) -> &[T
] {
728 /// Extracts a mutable slice of the entire vector.
730 /// Equivalent to `&mut s[..]`.
735 /// use std::io::{self, Read};
736 /// let mut buffer = vec![0; 3];
737 /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();
740 #[stable(feature = "vec_as_slice", since = "1.7.0")]
741 pub fn as_mut_slice(&mut self) -> &mut [T
] {
745 /// Sets the length of a vector.
747 /// This will explicitly set the size of the vector, without actually
748 /// modifying its buffers, so it is up to the caller to ensure that the
749 /// vector is actually the specified size.
756 /// let mut vec = vec!['r', 'u', 's', 't'];
759 /// ptr::drop_in_place(&mut vec[3]);
762 /// assert_eq!(vec, ['r', 'u', 's']);
765 /// In this example, there is a memory leak since the memory locations
766 /// owned by the inner vectors were not freed prior to the `set_len` call:
769 /// let mut vec = vec![vec![1, 0, 0],
777 /// In this example, the vector gets expanded from zero to four items
778 /// without any memory allocations occurring, resulting in vector
779 /// values of unallocated memory:
782 /// let mut vec: Vec<char> = Vec::new();
789 #[stable(feature = "rust1", since = "1.0.0")]
790 pub unsafe fn set_len(&mut self, len
: usize) {
794 /// Removes an element from the vector and returns it.
796 /// The removed element is replaced by the last element of the vector.
798 /// This does not preserve ordering, but is O(1).
802 /// Panics if `index` is out of bounds.
807 /// let mut v = vec!["foo", "bar", "baz", "qux"];
809 /// assert_eq!(v.swap_remove(1), "bar");
810 /// assert_eq!(v, ["foo", "qux", "baz"]);
812 /// assert_eq!(v.swap_remove(0), "foo");
813 /// assert_eq!(v, ["baz", "qux"]);
816 #[stable(feature = "rust1", since = "1.0.0")]
817 pub fn swap_remove(&mut self, index
: usize) -> T
{
819 // We replace self[index] with the last element. Note that if the
820 // bounds check on hole succeeds there must be a last element (which
821 // can be self[index] itself).
822 let hole
: *mut T
= &mut self[index
];
823 let last
= ptr
::read(self.get_unchecked(self.len
- 1));
825 ptr
::replace(hole
, last
)
829 /// Inserts an element at position `index` within the vector, shifting all
830 /// elements after it to the right.
834 /// Panics if `index > len`.
839 /// let mut vec = vec![1, 2, 3];
840 /// vec.insert(1, 4);
841 /// assert_eq!(vec, [1, 4, 2, 3]);
842 /// vec.insert(4, 5);
843 /// assert_eq!(vec, [1, 4, 2, 3, 5]);
845 #[stable(feature = "rust1", since = "1.0.0")]
846 pub fn insert(&mut self, index
: usize, element
: T
) {
847 let len
= self.len();
848 assert
!(index
<= len
);
850 // space for the new element
851 if len
== self.buf
.cap() {
857 // The spot to put the new value
859 let p
= self.as_mut_ptr().add(index
);
860 // Shift everything over to make space. (Duplicating the
861 // `index`th element into two consecutive places.)
862 ptr
::copy(p
, p
.offset(1), len
- index
);
863 // Write it in, overwriting the first copy of the `index`th
865 ptr
::write(p
, element
);
867 self.set_len(len
+ 1);
871 /// Removes and returns the element at position `index` within the vector,
872 /// shifting all elements after it to the left.
876 /// Panics if `index` is out of bounds.
881 /// let mut v = vec![1, 2, 3];
882 /// assert_eq!(v.remove(1), 2);
883 /// assert_eq!(v, [1, 3]);
885 #[stable(feature = "rust1", since = "1.0.0")]
886 pub fn remove(&mut self, index
: usize) -> T
{
887 let len
= self.len();
888 assert
!(index
< len
);
893 // the place we are taking from.
894 let ptr
= self.as_mut_ptr().add(index
);
895 // copy it out, unsafely having a copy of the value on
896 // the stack and in the vector at the same time.
897 ret
= ptr
::read(ptr
);
899 // Shift everything down to fill in that spot.
900 ptr
::copy(ptr
.offset(1), ptr
, len
- index
- 1);
902 self.set_len(len
- 1);
907 /// Retains only the elements specified by the predicate.
909 /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
910 /// This method operates in place and preserves the order of the retained
916 /// let mut vec = vec![1, 2, 3, 4];
917 /// vec.retain(|&x| x%2 == 0);
918 /// assert_eq!(vec, [2, 4]);
920 #[stable(feature = "rust1", since = "1.0.0")]
921 pub fn retain
<F
>(&mut self, mut f
: F
)
922 where F
: FnMut(&T
) -> bool
924 self.drain_filter(|x
| !f(x
));
927 /// Removes all but the first of consecutive elements in the vector that resolve to the same
930 /// If the vector is sorted, this removes all duplicates.
935 /// let mut vec = vec![10, 20, 21, 30, 20];
937 /// vec.dedup_by_key(|i| *i / 10);
939 /// assert_eq!(vec, [10, 20, 30, 20]);
941 #[stable(feature = "dedup_by", since = "1.16.0")]
943 pub fn dedup_by_key
<F
, K
>(&mut self, mut key
: F
) where F
: FnMut(&mut T
) -> K
, K
: PartialEq
{
944 self.dedup_by(|a
, b
| key(a
) == key(b
))
947 /// Removes all but the first of consecutive elements in the vector satisfying a given equality
950 /// The `same_bucket` function is passed references to two elements from the vector, and
951 /// returns `true` if the elements compare equal, or `false` if they do not. The elements are
952 /// passed in opposite order from their order in the vector, so if `same_bucket(a, b)` returns
953 /// `true`, `a` is removed.
955 /// If the vector is sorted, this removes all duplicates.
960 /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];
962 /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));
964 /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]);
966 #[stable(feature = "dedup_by", since = "1.16.0")]
967 pub fn dedup_by
<F
>(&mut self, mut same_bucket
: F
) where F
: FnMut(&mut T
, &mut T
) -> bool
{
969 // Although we have a mutable reference to `self`, we cannot make
970 // *arbitrary* changes. The `same_bucket` calls could panic, so we
971 // must ensure that the vector is in a valid state at all time.
973 // The way that we handle this is by using swaps; we iterate
974 // over all the elements, swapping as we go so that at the end
975 // the elements we wish to keep are in the front, and those we
976 // wish to reject are at the back. We can then truncate the
977 // vector. This operation is still O(n).
979 // Example: We start in this state, where `r` represents "next
980 // read" and `w` represents "next_write`.
983 // +---+---+---+---+---+---+
984 // | 0 | 1 | 1 | 2 | 3 | 3 |
985 // +---+---+---+---+---+---+
988 // Comparing self[r] against self[w-1], this is not a duplicate, so
989 // we swap self[r] and self[w] (no effect as r==w) and then increment both
990 // r and w, leaving us with:
993 // +---+---+---+---+---+---+
994 // | 0 | 1 | 1 | 2 | 3 | 3 |
995 // +---+---+---+---+---+---+
998 // Comparing self[r] against self[w-1], this value is a duplicate,
999 // so we increment `r` but leave everything else unchanged:
1002 // +---+---+---+---+---+---+
1003 // | 0 | 1 | 1 | 2 | 3 | 3 |
1004 // +---+---+---+---+---+---+
1007 // Comparing self[r] against self[w-1], this is not a duplicate,
1008 // so swap self[r] and self[w] and advance r and w:
1011 // +---+---+---+---+---+---+
1012 // | 0 | 1 | 2 | 1 | 3 | 3 |
1013 // +---+---+---+---+---+---+
1016 // Not a duplicate, repeat:
1019 // +---+---+---+---+---+---+
1020 // | 0 | 1 | 2 | 3 | 1 | 3 |
1021 // +---+---+---+---+---+---+
1024 // Duplicate, advance r. End of vec. Truncate to w.
1026 let ln
= self.len();
1031 // Avoid bounds checks by using raw pointers.
1032 let p
= self.as_mut_ptr();
1033 let mut r
: usize = 1;
1034 let mut w
: usize = 1;
1038 let p_wm1
= p
.add(w
- 1);
1039 if !same_bucket(&mut *p_r
, &mut *p_wm1
) {
1041 let p_w
= p_wm1
.offset(1);
1042 mem
::swap(&mut *p_r
, &mut *p_w
);
1053 /// Appends an element to the back of a collection.
1057 /// Panics if the number of elements in the vector overflows a `usize`.
1062 /// let mut vec = vec![1, 2];
1064 /// assert_eq!(vec, [1, 2, 3]);
1067 #[stable(feature = "rust1", since = "1.0.0")]
1068 pub fn push(&mut self, value
: T
) {
1069 // This will panic or abort if we would allocate > isize::MAX bytes
1070 // or if the length increment would overflow for zero-sized types.
1071 if self.len
== self.buf
.cap() {
1075 let end
= self.as_mut_ptr().add(self.len
);
1076 ptr
::write(end
, value
);
1081 /// Removes the last element from a vector and returns it, or [`None`] if it
1084 /// [`None`]: ../../std/option/enum.Option.html#variant.None
1089 /// let mut vec = vec![1, 2, 3];
1090 /// assert_eq!(vec.pop(), Some(3));
1091 /// assert_eq!(vec, [1, 2]);
1094 #[stable(feature = "rust1", since = "1.0.0")]
1095 pub fn pop(&mut self) -> Option
<T
> {
1101 Some(ptr
::read(self.get_unchecked(self.len())))
1106 /// Moves all the elements of `other` into `Self`, leaving `other` empty.
1110 /// Panics if the number of elements in the vector overflows a `usize`.
1115 /// let mut vec = vec![1, 2, 3];
1116 /// let mut vec2 = vec![4, 5, 6];
1117 /// vec.append(&mut vec2);
1118 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
1119 /// assert_eq!(vec2, []);
1122 #[stable(feature = "append", since = "1.4.0")]
1123 pub fn append(&mut self, other
: &mut Self) {
1125 self.append_elements(other
.as_slice() as _
);
1130 /// Appends elements to `Self` from other buffer.
1132 unsafe fn append_elements(&mut self, other
: *const [T
]) {
1133 let count
= (*other
).len();
1134 self.reserve(count
);
1135 let len
= self.len();
1136 ptr
::copy_nonoverlapping(other
as *const T
, self.get_unchecked_mut(len
), count
);
1140 /// Creates a draining iterator that removes the specified range in the vector
1141 /// and yields the removed items.
1143 /// Note 1: The element range is removed even if the iterator is only
1144 /// partially consumed or not consumed at all.
1146 /// Note 2: It is unspecified how many elements are removed from the vector
1147 /// if the `Drain` value is leaked.
1151 /// Panics if the starting point is greater than the end point or if
1152 /// the end point is greater than the length of the vector.
1157 /// let mut v = vec![1, 2, 3];
1158 /// let u: Vec<_> = v.drain(1..).collect();
1159 /// assert_eq!(v, &[1]);
1160 /// assert_eq!(u, &[2, 3]);
1162 /// // A full range clears the vector
1164 /// assert_eq!(v, &[]);
1166 #[stable(feature = "drain", since = "1.6.0")]
1167 pub fn drain
<R
>(&mut self, range
: R
) -> Drain
<T
>
1168 where R
: RangeBounds
<usize>
1172 // When the Drain is first created, it shortens the length of
1173 // the source vector to make sure no uninitialized or moved-from elements
1174 // are accessible at all if the Drain's destructor never gets to run.
1176 // Drain will ptr::read out the values to remove.
1177 // When finished, remaining tail of the vec is copied back to cover
1178 // the hole, and the vector length is restored to the new length.
1180 let len
= self.len();
1181 let start
= match range
.start_bound() {
1183 Excluded(&n
) => n
+ 1,
1186 let end
= match range
.end_bound() {
1187 Included(&n
) => n
+ 1,
1191 assert
!(start
<= end
);
1192 assert
!(end
<= len
);
1195 // set self.vec length's to start, to be safe in case Drain is leaked
1196 self.set_len(start
);
1197 // Use the borrow in the IterMut to indicate borrowing behavior of the
1198 // whole Drain iterator (like &mut T).
1199 let range_slice
= slice
::from_raw_parts_mut(self.as_mut_ptr().add(start
),
1203 tail_len
: len
- end
,
1204 iter
: range_slice
.iter(),
1205 vec
: NonNull
::from(self),
1210 /// Clears the vector, removing all values.
1212 /// Note that this method has no effect on the allocated capacity
1218 /// let mut v = vec![1, 2, 3];
1222 /// assert!(v.is_empty());
1225 #[stable(feature = "rust1", since = "1.0.0")]
1226 pub fn clear(&mut self) {
1230 /// Returns the number of elements in the vector, also referred to
1231 /// as its 'length'.
1236 /// let a = vec![1, 2, 3];
1237 /// assert_eq!(a.len(), 3);
1240 #[stable(feature = "rust1", since = "1.0.0")]
1241 pub fn len(&self) -> usize {
1245 /// Returns `true` if the vector contains no elements.
1250 /// let mut v = Vec::new();
1251 /// assert!(v.is_empty());
1254 /// assert!(!v.is_empty());
1256 #[stable(feature = "rust1", since = "1.0.0")]
1257 pub fn is_empty(&self) -> bool
{
1261 /// Splits the collection into two at the given index.
1263 /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`,
1264 /// and the returned `Self` contains elements `[at, len)`.
1266 /// Note that the capacity of `self` does not change.
1270 /// Panics if `at > len`.
1275 /// let mut vec = vec![1,2,3];
1276 /// let vec2 = vec.split_off(1);
1277 /// assert_eq!(vec, [1]);
1278 /// assert_eq!(vec2, [2, 3]);
1281 #[stable(feature = "split_off", since = "1.4.0")]
1282 pub fn split_off(&mut self, at
: usize) -> Self {
1283 assert
!(at
<= self.len(), "`at` out of bounds");
1285 let other_len
= self.len
- at
;
1286 let mut other
= Vec
::with_capacity(other_len
);
1288 // Unsafely `set_len` and copy items to `other`.
1291 other
.set_len(other_len
);
1293 ptr
::copy_nonoverlapping(self.as_ptr().add(at
),
1300 /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
1302 /// If `new_len` is greater than `len`, the `Vec` is extended by the
1303 /// difference, with each additional slot filled with the result of
1304 /// calling the closure `f`. The return values from `f` will end up
1305 /// in the `Vec` in the order they have been generated.
1307 /// If `new_len` is less than `len`, the `Vec` is simply truncated.
1309 /// This method uses a closure to create new values on every push. If
1310 /// you'd rather [`Clone`] a given value, use [`resize`]. If you want
1311 /// to use the [`Default`] trait to generate values, you can pass
1312 /// [`Default::default()`] as the second argument..
1317 /// #![feature(vec_resize_with)]
1319 /// let mut vec = vec![1, 2, 3];
1320 /// vec.resize_with(5, Default::default);
1321 /// assert_eq!(vec, [1, 2, 3, 0, 0]);
1323 /// let mut vec = vec![];
1325 /// vec.resize_with(4, || { p *= 2; p });
1326 /// assert_eq!(vec, [2, 4, 8, 16]);
1329 /// [`resize`]: #method.resize
1330 /// [`Clone`]: ../../std/clone/trait.Clone.html
1331 #[unstable(feature = "vec_resize_with", issue = "41758")]
1332 pub fn resize_with
<F
>(&mut self, new_len
: usize, f
: F
)
1333 where F
: FnMut() -> T
1335 let len
= self.len();
1337 self.extend_with(new_len
- len
, ExtendFunc(f
));
1339 self.truncate(new_len
);
1344 impl<T
: Clone
> Vec
<T
> {
1345 /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
1347 /// If `new_len` is greater than `len`, the `Vec` is extended by the
1348 /// difference, with each additional slot filled with `value`.
1349 /// If `new_len` is less than `len`, the `Vec` is simply truncated.
1351 /// This method requires [`Clone`] to be able clone the passed value. If
1352 /// you need more flexibility (or want to rely on [`Default`] instead of
1353 /// [`Clone`]), use [`resize_with`].
1358 /// let mut vec = vec!["hello"];
1359 /// vec.resize(3, "world");
1360 /// assert_eq!(vec, ["hello", "world", "world"]);
1362 /// let mut vec = vec![1, 2, 3, 4];
1363 /// vec.resize(2, 0);
1364 /// assert_eq!(vec, [1, 2]);
1367 /// [`Clone`]: ../../std/clone/trait.Clone.html
1368 /// [`Default`]: ../../std/default/trait.Default.html
1369 /// [`resize_with`]: #method.resize_with
1370 #[stable(feature = "vec_resize", since = "1.5.0")]
1371 pub fn resize(&mut self, new_len
: usize, value
: T
) {
1372 let len
= self.len();
1375 self.extend_with(new_len
- len
, ExtendElement(value
))
1377 self.truncate(new_len
);
1381 /// Clones and appends all elements in a slice to the `Vec`.
1383 /// Iterates over the slice `other`, clones each element, and then appends
1384 /// it to this `Vec`. The `other` vector is traversed in-order.
1386 /// Note that this function is same as [`extend`] except that it is
1387 /// specialized to work with slices instead. If and when Rust gets
1388 /// specialization this function will likely be deprecated (but still
1394 /// let mut vec = vec![1];
1395 /// vec.extend_from_slice(&[2, 3, 4]);
1396 /// assert_eq!(vec, [1, 2, 3, 4]);
1399 /// [`extend`]: #method.extend
1400 #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
1401 pub fn extend_from_slice(&mut self, other
: &[T
]) {
1402 self.spec_extend(other
.iter())
1406 impl<T
: Default
> Vec
<T
> {
1407 /// Resizes the `Vec` in-place so that `len` is equal to `new_len`.
1409 /// If `new_len` is greater than `len`, the `Vec` is extended by the
1410 /// difference, with each additional slot filled with [`Default::default()`].
1411 /// If `new_len` is less than `len`, the `Vec` is simply truncated.
1413 /// This method uses [`Default`] to create new values on every push. If
1414 /// you'd rather [`Clone`] a given value, use [`resize`].
1419 /// #![feature(vec_resize_default)]
1421 /// let mut vec = vec![1, 2, 3];
1422 /// vec.resize_default(5);
1423 /// assert_eq!(vec, [1, 2, 3, 0, 0]);
1425 /// let mut vec = vec![1, 2, 3, 4];
1426 /// vec.resize_default(2);
1427 /// assert_eq!(vec, [1, 2]);
1430 /// [`resize`]: #method.resize
1431 /// [`Default::default()`]: ../../std/default/trait.Default.html#tymethod.default
1432 /// [`Default`]: ../../std/default/trait.Default.html
1433 /// [`Clone`]: ../../std/clone/trait.Clone.html
1434 #[unstable(feature = "vec_resize_default", issue = "41758")]
1435 pub fn resize_default(&mut self, new_len
: usize) {
1436 let len
= self.len();
1439 self.extend_with(new_len
- len
, ExtendDefault
);
1441 self.truncate(new_len
);
1446 // This code generalises `extend_with_{element,default}`.
1447 trait ExtendWith
<T
> {
1448 fn next(&mut self) -> T
;
1452 struct ExtendElement
<T
>(T
);
1453 impl<T
: Clone
> ExtendWith
<T
> for ExtendElement
<T
> {
1454 fn next(&mut self) -> T { self.0.clone() }
1455 fn last(self) -> T { self.0 }
1458 struct ExtendDefault
;
1459 impl<T
: Default
> ExtendWith
<T
> for ExtendDefault
{
1460 fn next(&mut self) -> T { Default::default() }
1461 fn last(self) -> T { Default::default() }
1464 struct ExtendFunc
<F
>(F
);
1465 impl<T
, F
: FnMut() -> T
> ExtendWith
<T
> for ExtendFunc
<F
> {
1466 fn next(&mut self) -> T { (self.0)() }
1467 fn last(mut self) -> T { (self.0)() }
1471 /// Extend the vector by `n` values, using the given generator.
1472 fn extend_with
<E
: ExtendWith
<T
>>(&mut self, n
: usize, mut value
: E
) {
1476 let mut ptr
= self.as_mut_ptr().add(self.len());
1477 // Use SetLenOnDrop to work around bug where compiler
1478 // may not realize the store through `ptr` through self.set_len()
1480 let mut local_len
= SetLenOnDrop
::new(&mut self.len
);
1482 // Write all elements except the last one
1484 ptr
::write(ptr
, value
.next());
1485 ptr
= ptr
.offset(1);
1486 // Increment the length in every step in case next() panics
1487 local_len
.increment_len(1);
1491 // We can write the last element directly without cloning needlessly
1492 ptr
::write(ptr
, value
.last());
1493 local_len
.increment_len(1);
1496 // len set by scope guard
1501 // Set the length of the vec when the `SetLenOnDrop` value goes out of scope.
1503 // The idea is: The length field in SetLenOnDrop is a local variable
1504 // that the optimizer will see does not alias with any stores through the Vec's data
1505 // pointer. This is a workaround for alias analysis issue #32155
1506 struct SetLenOnDrop
<'a
> {
1511 impl<'a
> SetLenOnDrop
<'a
> {
1513 fn new(len
: &'a
mut usize) -> Self {
1514 SetLenOnDrop { local_len: *len, len: len }
1518 fn increment_len(&mut self, increment
: usize) {
1519 self.local_len
+= increment
;
1523 fn decrement_len(&mut self, decrement
: usize) {
1524 self.local_len
-= decrement
;
1528 impl<'a
> Drop
for SetLenOnDrop
<'a
> {
1530 fn drop(&mut self) {
1531 *self.len
= self.local_len
;
1535 impl<T
: PartialEq
> Vec
<T
> {
1536 /// Removes consecutive repeated elements in the vector.
1538 /// If the vector is sorted, this removes all duplicates.
1543 /// let mut vec = vec![1, 2, 2, 3, 2];
1547 /// assert_eq!(vec, [1, 2, 3, 2]);
1549 #[stable(feature = "rust1", since = "1.0.0")]
1551 pub fn dedup(&mut self) {
1552 self.dedup_by(|a
, b
| a
== b
)
1555 /// Removes the first instance of `item` from the vector if the item exists.
1560 /// # #![feature(vec_remove_item)]
1561 /// let mut vec = vec![1, 2, 3, 1];
1563 /// vec.remove_item(&1);
1565 /// assert_eq!(vec, vec![2, 3, 1]);
1567 #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")]
1568 pub fn remove_item(&mut self, item
: &T
) -> Option
<T
> {
1569 let pos
= self.iter().position(|x
| *x
== *item
)?
;
1570 Some(self.remove(pos
))
1574 ////////////////////////////////////////////////////////////////////////////////
1575 // Internal methods and functions
1576 ////////////////////////////////////////////////////////////////////////////////
1579 #[stable(feature = "rust1", since = "1.0.0")]
1580 pub fn from_elem
<T
: Clone
>(elem
: T
, n
: usize) -> Vec
<T
> {
1581 <T
as SpecFromElem
>::from_elem(elem
, n
)
1584 // Specialization trait used for Vec::from_elem
1585 trait SpecFromElem
: Sized
{
1586 fn from_elem(elem
: Self, n
: usize) -> Vec
<Self>;
1589 impl<T
: Clone
> SpecFromElem
for T
{
1590 default fn from_elem(elem
: Self, n
: usize) -> Vec
<Self> {
1591 let mut v
= Vec
::with_capacity(n
);
1592 v
.extend_with(n
, ExtendElement(elem
));
1597 impl SpecFromElem
for u8 {
1599 fn from_elem(elem
: u8, n
: usize) -> Vec
<u8> {
1602 buf
: RawVec
::with_capacity_zeroed(n
),
1607 let mut v
= Vec
::with_capacity(n
);
1608 ptr
::write_bytes(v
.as_mut_ptr(), elem
, n
);
1615 impl<T
: Clone
+ IsZero
> SpecFromElem
for T
{
1617 fn from_elem(elem
: T
, n
: usize) -> Vec
<T
> {
1620 buf
: RawVec
::with_capacity_zeroed(n
),
1624 let mut v
= Vec
::with_capacity(n
);
1625 v
.extend_with(n
, ExtendElement(elem
));
1630 unsafe trait IsZero
{
1631 /// Whether this value is zero
1632 fn is_zero(&self) -> bool
;
1635 macro_rules
! impl_is_zero
{
1636 ($t
: ty
, $is_zero
: expr
) => {
1637 unsafe impl IsZero
for $t
{
1639 fn is_zero(&self) -> bool
{
1646 impl_is_zero
!(i8, |x
| x
== 0);
1647 impl_is_zero
!(i16, |x
| x
== 0);
1648 impl_is_zero
!(i32, |x
| x
== 0);
1649 impl_is_zero
!(i64, |x
| x
== 0);
1650 impl_is_zero
!(i128
, |x
| x
== 0);
1651 impl_is_zero
!(isize, |x
| x
== 0);
1653 impl_is_zero
!(u16, |x
| x
== 0);
1654 impl_is_zero
!(u32, |x
| x
== 0);
1655 impl_is_zero
!(u64, |x
| x
== 0);
1656 impl_is_zero
!(u128
, |x
| x
== 0);
1657 impl_is_zero
!(usize, |x
| x
== 0);
1659 impl_is_zero
!(char, |x
| x
== '
\0'
);
1661 impl_is_zero
!(f32, |x
: f32| x
.to_bits() == 0);
1662 impl_is_zero
!(f64, |x
: f64| x
.to_bits() == 0);
1664 unsafe impl<T
: ?Sized
> IsZero
for *const T
{
1666 fn is_zero(&self) -> bool
{
1671 unsafe impl<T
: ?Sized
> IsZero
for *mut T
{
1673 fn is_zero(&self) -> bool
{
1679 ////////////////////////////////////////////////////////////////////////////////
1680 // Common trait implementations for Vec
1681 ////////////////////////////////////////////////////////////////////////////////
1683 #[stable(feature = "rust1", since = "1.0.0")]
1684 impl<T
: Clone
> Clone
for Vec
<T
> {
1686 fn clone(&self) -> Vec
<T
> {
1687 <[T
]>::to_vec(&**self)
1690 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
1691 // required for this method definition, is not available. Instead use the
1692 // `slice::to_vec` function which is only available with cfg(test)
1693 // NB see the slice::hack module in slice.rs for more information
1695 fn clone(&self) -> Vec
<T
> {
1696 ::slice
::to_vec(&**self)
1699 fn clone_from(&mut self, other
: &Vec
<T
>) {
1700 other
.as_slice().clone_into(self);
1704 #[stable(feature = "rust1", since = "1.0.0")]
1705 impl<T
: Hash
> Hash
for Vec
<T
> {
1707 fn hash
<H
: hash
::Hasher
>(&self, state
: &mut H
) {
1708 Hash
::hash(&**self, state
)
1712 #[stable(feature = "rust1", since = "1.0.0")]
1713 #[rustc_on_unimplemented(
1714 message
="vector indices are of type `usize` or ranges of `usize`",
1715 label
="vector indices are of type `usize` or ranges of `usize`",
1717 impl<T
, I
> Index
<I
> for Vec
<T
>
1719 I
: ::core
::slice
::SliceIndex
<[T
]>,
1721 type Output
= I
::Output
;
1724 fn index(&self, index
: I
) -> &Self::Output
{
1725 Index
::index(&**self, index
)
1729 #[stable(feature = "rust1", since = "1.0.0")]
1730 #[rustc_on_unimplemented(
1731 message
="vector indices are of type `usize` or ranges of `usize`",
1732 label
="vector indices are of type `usize` or ranges of `usize`",
1734 impl<T
, I
> IndexMut
<I
> for Vec
<T
>
1736 I
: ::core
::slice
::SliceIndex
<[T
]>,
1739 fn index_mut(&mut self, index
: I
) -> &mut Self::Output
{
1740 IndexMut
::index_mut(&mut **self, index
)
1744 #[stable(feature = "rust1", since = "1.0.0")]
1745 impl<T
> ops
::Deref
for Vec
<T
> {
1748 fn deref(&self) -> &[T
] {
1750 let p
= self.buf
.ptr();
1751 assume(!p
.is_null());
1752 slice
::from_raw_parts(p
, self.len
)
1757 #[stable(feature = "rust1", since = "1.0.0")]
1758 impl<T
> ops
::DerefMut
for Vec
<T
> {
1759 fn deref_mut(&mut self) -> &mut [T
] {
1761 let ptr
= self.buf
.ptr();
1762 assume(!ptr
.is_null());
1763 slice
::from_raw_parts_mut(ptr
, self.len
)
1768 #[stable(feature = "rust1", since = "1.0.0")]
1769 impl<T
> FromIterator
<T
> for Vec
<T
> {
1771 fn from_iter
<I
: IntoIterator
<Item
= T
>>(iter
: I
) -> Vec
<T
> {
1772 <Self as SpecExtend
<T
, I
::IntoIter
>>::from_iter(iter
.into_iter())
1776 #[stable(feature = "rust1", since = "1.0.0")]
1777 impl<T
> IntoIterator
for Vec
<T
> {
1779 type IntoIter
= IntoIter
<T
>;
1781 /// Creates a consuming iterator, that is, one that moves each value out of
1782 /// the vector (from start to end). The vector cannot be used after calling
1788 /// let v = vec!["a".to_string(), "b".to_string()];
1789 /// for s in v.into_iter() {
1790 /// // s has type String, not &String
1791 /// println!("{}", s);
1795 fn into_iter(mut self) -> IntoIter
<T
> {
1797 let begin
= self.as_mut_ptr();
1798 assume(!begin
.is_null());
1799 let end
= if mem
::size_of
::<T
>() == 0 {
1800 arith_offset(begin
as *const i8, self.len() as isize) as *const T
1802 begin
.add(self.len()) as *const T
1804 let cap
= self.buf
.cap();
1807 buf
: NonNull
::new_unchecked(begin
),
1808 phantom
: PhantomData
,
1817 #[stable(feature = "rust1", since = "1.0.0")]
1818 impl<'a
, T
> IntoIterator
for &'a Vec
<T
> {
1820 type IntoIter
= slice
::Iter
<'a
, T
>;
1822 fn into_iter(self) -> slice
::Iter
<'a
, T
> {
1827 #[stable(feature = "rust1", since = "1.0.0")]
1828 impl<'a
, T
> IntoIterator
for &'a
mut Vec
<T
> {
1829 type Item
= &'a
mut T
;
1830 type IntoIter
= slice
::IterMut
<'a
, T
>;
1832 fn into_iter(self) -> slice
::IterMut
<'a
, T
> {
1837 #[stable(feature = "rust1", since = "1.0.0")]
1838 impl<T
> Extend
<T
> for Vec
<T
> {
1840 fn extend
<I
: IntoIterator
<Item
= T
>>(&mut self, iter
: I
) {
1841 <Self as SpecExtend
<T
, I
::IntoIter
>>::spec_extend(self, iter
.into_iter())
1845 // Specialization trait used for Vec::from_iter and Vec::extend
1846 trait SpecExtend
<T
, I
> {
1847 fn from_iter(iter
: I
) -> Self;
1848 fn spec_extend(&mut self, iter
: I
);
1851 impl<T
, I
> SpecExtend
<T
, I
> for Vec
<T
>
1852 where I
: Iterator
<Item
=T
>,
1854 default fn from_iter(mut iterator
: I
) -> Self {
1855 // Unroll the first iteration, as the vector is going to be
1856 // expanded on this iteration in every case when the iterable is not
1857 // empty, but the loop in extend_desugared() is not going to see the
1858 // vector being full in the few subsequent loop iterations.
1859 // So we get better branch prediction.
1860 let mut vector
= match iterator
.next() {
1861 None
=> return Vec
::new(),
1863 let (lower
, _
) = iterator
.size_hint();
1864 let mut vector
= Vec
::with_capacity(lower
.saturating_add(1));
1866 ptr
::write(vector
.get_unchecked_mut(0), element
);
1872 <Vec
<T
> as SpecExtend
<T
, I
>>::spec_extend(&mut vector
, iterator
);
1876 default fn spec_extend(&mut self, iter
: I
) {
1877 self.extend_desugared(iter
)
1881 impl<T
, I
> SpecExtend
<T
, I
> for Vec
<T
>
1882 where I
: TrustedLen
<Item
=T
>,
1884 default fn from_iter(iterator
: I
) -> Self {
1885 let mut vector
= Vec
::new();
1886 vector
.spec_extend(iterator
);
1890 default fn spec_extend(&mut self, iterator
: I
) {
1891 // This is the case for a TrustedLen iterator.
1892 let (low
, high
) = iterator
.size_hint();
1893 if let Some(high_value
) = high
{
1894 debug_assert_eq
!(low
, high_value
,
1895 "TrustedLen iterator's size hint is not exact: {:?}",
1898 if let Some(additional
) = high
{
1899 self.reserve(additional
);
1901 let mut ptr
= self.as_mut_ptr().add(self.len());
1902 let mut local_len
= SetLenOnDrop
::new(&mut self.len
);
1903 for element
in iterator
{
1904 ptr
::write(ptr
, element
);
1905 ptr
= ptr
.offset(1);
1906 // NB can't overflow since we would have had to alloc the address space
1907 local_len
.increment_len(1);
1911 self.extend_desugared(iterator
)
1916 impl<T
> SpecExtend
<T
, IntoIter
<T
>> for Vec
<T
> {
1917 fn from_iter(iterator
: IntoIter
<T
>) -> Self {
1918 // A common case is passing a vector into a function which immediately
1919 // re-collects into a vector. We can short circuit this if the IntoIter
1920 // has not been advanced at all.
1921 if iterator
.buf
.as_ptr() as *const _
== iterator
.ptr
{
1923 let vec
= Vec
::from_raw_parts(iterator
.buf
.as_ptr(),
1926 mem
::forget(iterator
);
1930 let mut vector
= Vec
::new();
1931 vector
.spec_extend(iterator
);
1936 fn spec_extend(&mut self, mut iterator
: IntoIter
<T
>) {
1938 self.append_elements(iterator
.as_slice() as _
);
1940 iterator
.ptr
= iterator
.end
;
1944 impl<'a
, T
: 'a
, I
> SpecExtend
<&'a T
, I
> for Vec
<T
>
1945 where I
: Iterator
<Item
=&'a T
>,
1948 default fn from_iter(iterator
: I
) -> Self {
1949 SpecExtend
::from_iter(iterator
.cloned())
1952 default fn spec_extend(&mut self, iterator
: I
) {
1953 self.spec_extend(iterator
.cloned())
1957 impl<'a
, T
: 'a
> SpecExtend
<&'a T
, slice
::Iter
<'a
, T
>> for Vec
<T
>
1960 fn spec_extend(&mut self, iterator
: slice
::Iter
<'a
, T
>) {
1961 let slice
= iterator
.as_slice();
1962 self.reserve(slice
.len());
1964 let len
= self.len();
1965 self.set_len(len
+ slice
.len());
1966 self.get_unchecked_mut(len
..).copy_from_slice(slice
);
1972 fn extend_desugared
<I
: Iterator
<Item
= T
>>(&mut self, mut iterator
: I
) {
1973 // This is the case for a general iterator.
1975 // This function should be the moral equivalent of:
1977 // for item in iterator {
1980 while let Some(element
) = iterator
.next() {
1981 let len
= self.len();
1982 if len
== self.capacity() {
1983 let (lower
, _
) = iterator
.size_hint();
1984 self.reserve(lower
.saturating_add(1));
1987 ptr
::write(self.get_unchecked_mut(len
), element
);
1988 // NB can't overflow since we would have had to alloc the address space
1989 self.set_len(len
+ 1);
1994 /// Creates a splicing iterator that replaces the specified range in the vector
1995 /// with the given `replace_with` iterator and yields the removed items.
1996 /// `replace_with` does not need to be the same length as `range`.
1998 /// Note 1: The element range is removed even if the iterator is not
1999 /// consumed until the end.
2001 /// Note 2: It is unspecified how many elements are removed from the vector,
2002 /// if the `Splice` value is leaked.
2004 /// Note 3: The input iterator `replace_with` is only consumed
2005 /// when the `Splice` value is dropped.
2007 /// Note 4: This is optimal if:
2009 /// * The tail (elements in the vector after `range`) is empty,
2010 /// * or `replace_with` yields fewer elements than `range`’s length
2011 /// * or the lower bound of its `size_hint()` is exact.
2013 /// Otherwise, a temporary vector is allocated and the tail is moved twice.
2017 /// Panics if the starting point is greater than the end point or if
2018 /// the end point is greater than the length of the vector.
2023 /// let mut v = vec![1, 2, 3];
2024 /// let new = [7, 8];
2025 /// let u: Vec<_> = v.splice(..2, new.iter().cloned()).collect();
2026 /// assert_eq!(v, &[7, 8, 3]);
2027 /// assert_eq!(u, &[1, 2]);
2030 #[stable(feature = "vec_splice", since = "1.21.0")]
2031 pub fn splice
<R
, I
>(&mut self, range
: R
, replace_with
: I
) -> Splice
<I
::IntoIter
>
2032 where R
: RangeBounds
<usize>, I
: IntoIterator
<Item
=T
>
2035 drain
: self.drain(range
),
2036 replace_with
: replace_with
.into_iter(),
2040 /// Creates an iterator which uses a closure to determine if an element should be removed.
2042 /// If the closure returns true, then the element is removed and yielded.
2043 /// If the closure returns false, the element will remain in the vector and will not be yielded
2044 /// by the iterator.
2046 /// Using this method is equivalent to the following code:
2049 /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 };
2050 /// # let mut vec = vec![1, 2, 3, 4, 5, 6];
2052 /// while i != vec.len() {
2053 /// if some_predicate(&mut vec[i]) {
2054 /// let val = vec.remove(i);
2055 /// // your code here
2061 /// # assert_eq!(vec, vec![1, 4, 5]);
2064 /// But `drain_filter` is easier to use. `drain_filter` is also more efficient,
2065 /// because it can backshift the elements of the array in bulk.
2067 /// Note that `drain_filter` also lets you mutate every element in the filter closure,
2068 /// regardless of whether you choose to keep or remove it.
2073 /// Splitting an array into evens and odds, reusing the original allocation:
2076 /// #![feature(drain_filter)]
2077 /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];
2079 /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
2080 /// let odds = numbers;
2082 /// assert_eq!(evens, vec![2, 4, 6, 8, 14]);
2083 /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);
2085 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2086 pub fn drain_filter
<F
>(&mut self, filter
: F
) -> DrainFilter
<T
, F
>
2087 where F
: FnMut(&mut T
) -> bool
,
2089 let old_len
= self.len();
2091 // Guard against us getting leaked (leak amplification)
2092 unsafe { self.set_len(0); }
2104 /// Extend implementation that copies elements out of references before pushing them onto the Vec.
2106 /// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to
2107 /// append the entire slice at once.
2109 /// [`copy_from_slice`]: ../../std/primitive.slice.html#method.copy_from_slice
2110 #[stable(feature = "extend_ref", since = "1.2.0")]
2111 impl<'a
, T
: 'a
+ Copy
> Extend
<&'a T
> for Vec
<T
> {
2112 fn extend
<I
: IntoIterator
<Item
= &'a T
>>(&mut self, iter
: I
) {
2113 self.spec_extend(iter
.into_iter())
2117 macro_rules
! __impl_slice_eq1
{
2118 ($Lhs
: ty
, $Rhs
: ty
) => {
2119 __impl_slice_eq1
! { $Lhs, $Rhs, Sized }
2121 ($Lhs
: ty
, $Rhs
: ty
, $Bound
: ident
) => {
2122 #[stable(feature = "rust1", since = "1.0.0")]
2123 impl<'a
, 'b
, A
: $Bound
, B
> PartialEq
<$Rhs
> for $Lhs
where A
: PartialEq
<B
> {
2125 fn eq(&self, other
: &$Rhs
) -> bool { self[..] == other[..] }
2127 fn ne(&self, other
: &$Rhs
) -> bool { self[..] != other[..] }
2132 __impl_slice_eq1
! { Vec<A>, Vec<B> }
2133 __impl_slice_eq1
! { Vec<A>, &'b [B] }
2134 __impl_slice_eq1
! { Vec<A>, &'b mut [B] }
2135 __impl_slice_eq1
! { Cow<'a, [A]>, &'b [B], Clone }
2136 __impl_slice_eq1
! { Cow<'a, [A]>, &'b mut [B], Clone }
2137 __impl_slice_eq1
! { Cow<'a, [A]>, Vec<B>, Clone }
2139 macro_rules
! array_impls
{
2142 // NOTE: some less important impls are omitted to reduce code bloat
2143 __impl_slice_eq1
! { Vec<A>, [B; $N] }
2144 __impl_slice_eq1
! { Vec<A>, &'b [B; $N] }
2145 // __impl_slice_eq1! { Vec<A>, &'b mut [B; $N] }
2146 // __impl_slice_eq1! { Cow<'a, [A]>, [B; $N], Clone }
2147 // __impl_slice_eq1! { Cow<'a, [A]>, &'b [B; $N], Clone }
2148 // __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
2155 10 11 12 13 14 15 16 17 18 19
2156 20 21 22 23 24 25 26 27 28 29
2160 /// Implements comparison of vectors, lexicographically.
2161 #[stable(feature = "rust1", since = "1.0.0")]
2162 impl<T
: PartialOrd
> PartialOrd
for Vec
<T
> {
2164 fn partial_cmp(&self, other
: &Vec
<T
>) -> Option
<Ordering
> {
2165 PartialOrd
::partial_cmp(&**self, &**other
)
2169 #[stable(feature = "rust1", since = "1.0.0")]
2170 impl<T
: Eq
> Eq
for Vec
<T
> {}
2172 /// Implements ordering of vectors, lexicographically.
2173 #[stable(feature = "rust1", since = "1.0.0")]
2174 impl<T
: Ord
> Ord
for Vec
<T
> {
2176 fn cmp(&self, other
: &Vec
<T
>) -> Ordering
{
2177 Ord
::cmp(&**self, &**other
)
2181 #[stable(feature = "rust1", since = "1.0.0")]
2182 unsafe impl<#[may_dangle] T> Drop for Vec<T> {
2183 fn drop(&mut self) {
2186 ptr
::drop_in_place(&mut self[..]);
2188 // RawVec handles deallocation
2192 #[stable(feature = "rust1", since = "1.0.0")]
2193 impl<T
> Default
for Vec
<T
> {
2194 /// Creates an empty `Vec<T>`.
2195 fn default() -> Vec
<T
> {
2200 #[stable(feature = "rust1", since = "1.0.0")]
2201 impl<T
: fmt
::Debug
> fmt
::Debug
for Vec
<T
> {
2202 fn fmt(&self, f
: &mut fmt
::Formatter
) -> fmt
::Result
{
2203 fmt
::Debug
::fmt(&**self, f
)
2207 #[stable(feature = "rust1", since = "1.0.0")]
2208 impl<T
> AsRef
<Vec
<T
>> for Vec
<T
> {
2209 fn as_ref(&self) -> &Vec
<T
> {
2214 #[stable(feature = "vec_as_mut", since = "1.5.0")]
2215 impl<T
> AsMut
<Vec
<T
>> for Vec
<T
> {
2216 fn as_mut(&mut self) -> &mut Vec
<T
> {
2221 #[stable(feature = "rust1", since = "1.0.0")]
2222 impl<T
> AsRef
<[T
]> for Vec
<T
> {
2223 fn as_ref(&self) -> &[T
] {
2228 #[stable(feature = "vec_as_mut", since = "1.5.0")]
2229 impl<T
> AsMut
<[T
]> for Vec
<T
> {
2230 fn as_mut(&mut self) -> &mut [T
] {
2235 #[stable(feature = "rust1", since = "1.0.0")]
2236 impl<'a
, T
: Clone
> From
<&'a
[T
]> for Vec
<T
> {
2238 fn from(s
: &'a
[T
]) -> Vec
<T
> {
2242 fn from(s
: &'a
[T
]) -> Vec
<T
> {
2247 #[stable(feature = "vec_from_mut", since = "1.19.0")]
2248 impl<'a
, T
: Clone
> From
<&'a
mut [T
]> for Vec
<T
> {
2250 fn from(s
: &'a
mut [T
]) -> Vec
<T
> {
2254 fn from(s
: &'a
mut [T
]) -> Vec
<T
> {
2259 #[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
2260 impl<'a
, T
> From
<Cow
<'a
, [T
]>> for Vec
<T
> where [T
]: ToOwned
<Owned
=Vec
<T
>> {
2261 fn from(s
: Cow
<'a
, [T
]>) -> Vec
<T
> {
2266 // note: test pulls in libstd, which causes errors here
2268 #[stable(feature = "vec_from_box", since = "1.18.0")]
2269 impl<T
> From
<Box
<[T
]>> for Vec
<T
> {
2270 fn from(s
: Box
<[T
]>) -> Vec
<T
> {
2275 // note: test pulls in libstd, which causes errors here
2277 #[stable(feature = "box_from_vec", since = "1.20.0")]
2278 impl<T
> From
<Vec
<T
>> for Box
<[T
]> {
2279 fn from(v
: Vec
<T
>) -> Box
<[T
]> {
2280 v
.into_boxed_slice()
2284 #[stable(feature = "rust1", since = "1.0.0")]
2285 impl<'a
> From
<&'a
str> for Vec
<u8> {
2286 fn from(s
: &'a
str) -> Vec
<u8> {
2287 From
::from(s
.as_bytes())
2291 ////////////////////////////////////////////////////////////////////////////////
2293 ////////////////////////////////////////////////////////////////////////////////
2295 #[stable(feature = "cow_from_vec", since = "1.8.0")]
2296 impl<'a
, T
: Clone
> From
<&'a
[T
]> for Cow
<'a
, [T
]> {
2297 fn from(s
: &'a
[T
]) -> Cow
<'a
, [T
]> {
2302 #[stable(feature = "cow_from_vec", since = "1.8.0")]
2303 impl<'a
, T
: Clone
> From
<Vec
<T
>> for Cow
<'a
, [T
]> {
2304 fn from(v
: Vec
<T
>) -> Cow
<'a
, [T
]> {
2309 #[stable(feature = "cow_from_vec_ref", since = "1.28.0")]
2310 impl<'a
, T
: Clone
> From
<&'a Vec
<T
>> for Cow
<'a
, [T
]> {
2311 fn from(v
: &'a Vec
<T
>) -> Cow
<'a
, [T
]> {
2312 Cow
::Borrowed(v
.as_slice())
2316 #[stable(feature = "rust1", since = "1.0.0")]
2317 impl<'a
, T
> FromIterator
<T
> for Cow
<'a
, [T
]> where T
: Clone
{
2318 fn from_iter
<I
: IntoIterator
<Item
= T
>>(it
: I
) -> Cow
<'a
, [T
]> {
2319 Cow
::Owned(FromIterator
::from_iter(it
))
2323 ////////////////////////////////////////////////////////////////////////////////
2325 ////////////////////////////////////////////////////////////////////////////////
2327 /// An iterator that moves out of a vector.
2329 /// This `struct` is created by the `into_iter` method on [`Vec`][`Vec`] (provided
2330 /// by the [`IntoIterator`] trait).
2332 /// [`Vec`]: struct.Vec.html
2333 /// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html
2334 #[stable(feature = "rust1", since = "1.0.0")]
2335 pub struct IntoIter
<T
> {
2337 phantom
: PhantomData
<T
>,
2343 #[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
2344 impl<T
: fmt
::Debug
> fmt
::Debug
for IntoIter
<T
> {
2345 fn fmt(&self, f
: &mut fmt
::Formatter
) -> fmt
::Result
{
2346 f
.debug_tuple("IntoIter")
2347 .field(&self.as_slice())
2352 impl<T
> IntoIter
<T
> {
2353 /// Returns the remaining items of this iterator as a slice.
2358 /// let vec = vec!['a', 'b', 'c'];
2359 /// let mut into_iter = vec.into_iter();
2360 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
2361 /// let _ = into_iter.next().unwrap();
2362 /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
2364 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
2365 pub fn as_slice(&self) -> &[T
] {
2367 slice
::from_raw_parts(self.ptr
, self.len())
2371 /// Returns the remaining items of this iterator as a mutable slice.
2376 /// let vec = vec!['a', 'b', 'c'];
2377 /// let mut into_iter = vec.into_iter();
2378 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
2379 /// into_iter.as_mut_slice()[2] = 'z';
2380 /// assert_eq!(into_iter.next().unwrap(), 'a');
2381 /// assert_eq!(into_iter.next().unwrap(), 'b');
2382 /// assert_eq!(into_iter.next().unwrap(), 'z');
2384 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
2385 pub fn as_mut_slice(&mut self) -> &mut [T
] {
2387 slice
::from_raw_parts_mut(self.ptr
as *mut T
, self.len())
2392 #[stable(feature = "rust1", since = "1.0.0")]
2393 unsafe impl<T
: Send
> Send
for IntoIter
<T
> {}
2394 #[stable(feature = "rust1", since = "1.0.0")]
2395 unsafe impl<T
: Sync
> Sync
for IntoIter
<T
> {}
2397 #[stable(feature = "rust1", since = "1.0.0")]
2398 impl<T
> Iterator
for IntoIter
<T
> {
2402 fn next(&mut self) -> Option
<T
> {
2404 if self.ptr
as *const _
== self.end
{
2407 if mem
::size_of
::<T
>() == 0 {
2408 // purposefully don't use 'ptr.offset' because for
2409 // vectors with 0-size elements this would return the
2411 self.ptr
= arith_offset(self.ptr
as *const i8, 1) as *mut T
;
2413 // Make up a value of this ZST.
2417 self.ptr
= self.ptr
.offset(1);
2419 Some(ptr
::read(old
))
2426 fn size_hint(&self) -> (usize, Option
<usize>) {
2427 let exact
= if mem
::size_of
::<T
>() == 0 {
2428 (self.end
as usize).wrapping_sub(self.ptr
as usize)
2430 unsafe { self.end.offset_from(self.ptr) as usize }
2432 (exact
, Some(exact
))
2436 fn count(self) -> usize {
2441 #[stable(feature = "rust1", since = "1.0.0")]
2442 impl<T
> DoubleEndedIterator
for IntoIter
<T
> {
2444 fn next_back(&mut self) -> Option
<T
> {
2446 if self.end
== self.ptr
{
2449 if mem
::size_of
::<T
>() == 0 {
2450 // See above for why 'ptr.offset' isn't used
2451 self.end
= arith_offset(self.end
as *const i8, -1) as *mut T
;
2453 // Make up a value of this ZST.
2456 self.end
= self.end
.offset(-1);
2458 Some(ptr
::read(self.end
))
2465 #[stable(feature = "rust1", since = "1.0.0")]
2466 impl<T
> ExactSizeIterator
for IntoIter
<T
> {
2467 fn is_empty(&self) -> bool
{
2468 self.ptr
== self.end
2472 #[stable(feature = "fused", since = "1.26.0")]
2473 impl<T
> FusedIterator
for IntoIter
<T
> {}
2475 #[unstable(feature = "trusted_len", issue = "37572")]
2476 unsafe impl<T
> TrustedLen
for IntoIter
<T
> {}
2478 #[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
2479 impl<T
: Clone
> Clone
for IntoIter
<T
> {
2480 fn clone(&self) -> IntoIter
<T
> {
2481 self.as_slice().to_owned().into_iter()
2485 #[stable(feature = "rust1", since = "1.0.0")]
2486 unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
2487 fn drop(&mut self) {
2488 // destroy the remaining elements
2489 for _x
in self.by_ref() {}
2491 // RawVec handles deallocation
2492 let _
= unsafe { RawVec::from_raw_parts(self.buf.as_ptr(), self.cap) }
;
2496 /// A draining iterator for `Vec<T>`.
2498 /// This `struct` is created by the [`drain`] method on [`Vec`].
2500 /// [`drain`]: struct.Vec.html#method.drain
2501 /// [`Vec`]: struct.Vec.html
2502 #[stable(feature = "drain", since = "1.6.0")]
2503 pub struct Drain
<'a
, T
: 'a
> {
2504 /// Index of tail to preserve
2508 /// Current remaining range to remove
2509 iter
: slice
::Iter
<'a
, T
>,
2510 vec
: NonNull
<Vec
<T
>>,
2513 #[stable(feature = "collection_debug", since = "1.17.0")]
2514 impl<'a
, T
: 'a
+ fmt
::Debug
> fmt
::Debug
for Drain
<'a
, T
> {
2515 fn fmt(&self, f
: &mut fmt
::Formatter
) -> fmt
::Result
{
2516 f
.debug_tuple("Drain")
2517 .field(&self.iter
.as_slice())
2522 #[stable(feature = "drain", since = "1.6.0")]
2523 unsafe impl<'a
, T
: Sync
> Sync
for Drain
<'a
, T
> {}
2524 #[stable(feature = "drain", since = "1.6.0")]
2525 unsafe impl<'a
, T
: Send
> Send
for Drain
<'a
, T
> {}
2527 #[stable(feature = "drain", since = "1.6.0")]
2528 impl<'a
, T
> Iterator
for Drain
<'a
, T
> {
2532 fn next(&mut self) -> Option
<T
> {
2533 self.iter
.next().map(|elt
| unsafe { ptr::read(elt as *const _) }
)
2536 fn size_hint(&self) -> (usize, Option
<usize>) {
2537 self.iter
.size_hint()
2541 #[stable(feature = "drain", since = "1.6.0")]
2542 impl<'a
, T
> DoubleEndedIterator
for Drain
<'a
, T
> {
2544 fn next_back(&mut self) -> Option
<T
> {
2545 self.iter
.next_back().map(|elt
| unsafe { ptr::read(elt as *const _) }
)
2549 #[stable(feature = "drain", since = "1.6.0")]
2550 impl<'a
, T
> Drop
for Drain
<'a
, T
> {
2551 fn drop(&mut self) {
2552 // exhaust self first
2553 self.for_each(drop
);
2555 if self.tail_len
> 0 {
2557 let source_vec
= self.vec
.as_mut();
2558 // memmove back untouched tail, update to new length
2559 let start
= source_vec
.len();
2560 let tail
= self.tail_start
;
2562 let src
= source_vec
.as_ptr().add(tail
);
2563 let dst
= source_vec
.as_mut_ptr().add(start
);
2564 ptr
::copy(src
, dst
, self.tail_len
);
2566 source_vec
.set_len(start
+ self.tail_len
);
2573 #[stable(feature = "drain", since = "1.6.0")]
2574 impl<'a
, T
> ExactSizeIterator
for Drain
<'a
, T
> {
2575 fn is_empty(&self) -> bool
{
2576 self.iter
.is_empty()
2580 #[stable(feature = "fused", since = "1.26.0")]
2581 impl<'a
, T
> FusedIterator
for Drain
<'a
, T
> {}
2583 /// A splicing iterator for `Vec`.
2585 /// This struct is created by the [`splice()`] method on [`Vec`]. See its
2586 /// documentation for more.
2588 /// [`splice()`]: struct.Vec.html#method.splice
2589 /// [`Vec`]: struct.Vec.html
2591 #[stable(feature = "vec_splice", since = "1.21.0")]
2592 pub struct Splice
<'a
, I
: Iterator
+ 'a
> {
2593 drain
: Drain
<'a
, I
::Item
>,
2597 #[stable(feature = "vec_splice", since = "1.21.0")]
2598 impl<'a
, I
: Iterator
> Iterator
for Splice
<'a
, I
> {
2599 type Item
= I
::Item
;
2601 fn next(&mut self) -> Option
<Self::Item
> {
2605 fn size_hint(&self) -> (usize, Option
<usize>) {
2606 self.drain
.size_hint()
2610 #[stable(feature = "vec_splice", since = "1.21.0")]
2611 impl<'a
, I
: Iterator
> DoubleEndedIterator
for Splice
<'a
, I
> {
2612 fn next_back(&mut self) -> Option
<Self::Item
> {
2613 self.drain
.next_back()
2617 #[stable(feature = "vec_splice", since = "1.21.0")]
2618 impl<'a
, I
: Iterator
> ExactSizeIterator
for Splice
<'a
, I
> {}
2621 #[stable(feature = "vec_splice", since = "1.21.0")]
2622 impl<'a
, I
: Iterator
> Drop
for Splice
<'a
, I
> {
2623 fn drop(&mut self) {
2624 self.drain
.by_ref().for_each(drop
);
2627 if self.drain
.tail_len
== 0 {
2628 self.drain
.vec
.as_mut().extend(self.replace_with
.by_ref());
2632 // First fill the range left by drain().
2633 if !self.drain
.fill(&mut self.replace_with
) {
2637 // There may be more elements. Use the lower bound as an estimate.
2638 // FIXME: Is the upper bound a better guess? Or something else?
2639 let (lower_bound
, _upper_bound
) = self.replace_with
.size_hint();
2640 if lower_bound
> 0 {
2641 self.drain
.move_tail(lower_bound
);
2642 if !self.drain
.fill(&mut self.replace_with
) {
2647 // Collect any remaining elements.
2648 // This is a zero-length vector which does not allocate if `lower_bound` was exact.
2649 let mut collected
= self.replace_with
.by_ref().collect
::<Vec
<I
::Item
>>().into_iter();
2650 // Now we have an exact count.
2651 if collected
.len() > 0 {
2652 self.drain
.move_tail(collected
.len());
2653 let filled
= self.drain
.fill(&mut collected
);
2654 debug_assert
!(filled
);
2655 debug_assert_eq
!(collected
.len(), 0);
2658 // Let `Drain::drop` move the tail back if necessary and restore `vec.len`.
2662 /// Private helper methods for `Splice::drop`
2663 impl<'a
, T
> Drain
<'a
, T
> {
2664 /// The range from `self.vec.len` to `self.tail_start` contains elements
2665 /// that have been moved out.
2666 /// Fill that range as much as possible with new elements from the `replace_with` iterator.
2667 /// Return whether we filled the entire range. (`replace_with.next()` didn’t return `None`.)
2668 unsafe fn fill
<I
: Iterator
<Item
=T
>>(&mut self, replace_with
: &mut I
) -> bool
{
2669 let vec
= self.vec
.as_mut();
2670 let range_start
= vec
.len
;
2671 let range_end
= self.tail_start
;
2672 let range_slice
= slice
::from_raw_parts_mut(
2673 vec
.as_mut_ptr().add(range_start
),
2674 range_end
- range_start
);
2676 for place
in range_slice
{
2677 if let Some(new_item
) = replace_with
.next() {
2678 ptr
::write(place
, new_item
);
2687 /// Make room for inserting more elements before the tail.
2688 unsafe fn move_tail(&mut self, extra_capacity
: usize) {
2689 let vec
= self.vec
.as_mut();
2690 let used_capacity
= self.tail_start
+ self.tail_len
;
2691 vec
.buf
.reserve(used_capacity
, extra_capacity
);
2693 let new_tail_start
= self.tail_start
+ extra_capacity
;
2694 let src
= vec
.as_ptr().add(self.tail_start
);
2695 let dst
= vec
.as_mut_ptr().add(new_tail_start
);
2696 ptr
::copy(src
, dst
, self.tail_len
);
2697 self.tail_start
= new_tail_start
;
2701 /// An iterator produced by calling `drain_filter` on Vec.
2702 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2704 pub struct DrainFilter
<'a
, T
: 'a
, F
>
2705 where F
: FnMut(&mut T
) -> bool
,
2707 vec
: &'a
mut Vec
<T
>,
2714 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2715 impl<'a
, T
, F
> Iterator
for DrainFilter
<'a
, T
, F
>
2716 where F
: FnMut(&mut T
) -> bool
,
2720 fn next(&mut self) -> Option
<T
> {
2722 while self.idx
!= self.old_len
{
2725 let v
= slice
::from_raw_parts_mut(self.vec
.as_mut_ptr(), self.old_len
);
2726 if (self.pred
)(&mut v
[i
]) {
2728 return Some(ptr
::read(&v
[i
]));
2729 } else if self.del
> 0 {
2731 let src
: *const T
= &v
[i
];
2732 let dst
: *mut T
= &mut v
[i
- del
];
2733 // This is safe because self.vec has length 0
2734 // thus its elements will not have Drop::drop
2735 // called on them in the event of a panic.
2736 ptr
::copy_nonoverlapping(src
, dst
, 1);
2743 fn size_hint(&self) -> (usize, Option
<usize>) {
2744 (0, Some(self.old_len
- self.idx
))
2748 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
2749 impl<'a
, T
, F
> Drop
for DrainFilter
<'a
, T
, F
>
2750 where F
: FnMut(&mut T
) -> bool
,
2752 fn drop(&mut self) {
2753 self.for_each(drop
);
2755 self.vec
.set_len(self.old_len
- self.del
);