1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A contiguous growable array type with heap-allocated contents, written
12 //! `Vec<T>` but pronounced 'vector.'
14 //! Vectors have `O(1)` indexing, amortized `O(1)` push (to the end) and
15 //! `O(1)` pop (from the end).
19 //! You can explicitly create a `Vec<T>` with `new()`:
22 //! let v: Vec<i32> = Vec::new();
25 //! ...or by using the `vec!` macro:
28 //! let v: Vec<i32> = vec![];
30 //! let v = vec![1, 2, 3, 4, 5];
32 //! let v = vec![0; 10]; // ten zeroes
35 //! You can `push` values onto the end of a vector (which will grow the vector
39 //! let mut v = vec![1, 2];
44 //! Popping values works in much the same way:
47 //! let mut v = vec![1, 2];
49 //! let two = v.pop();
52 //! Vectors also support indexing (through the `Index` and `IndexMut` traits):
55 //! let mut v = vec![1, 2, 3];
60 #![stable(feature = "rust1", since = "1.0.0")]
62 use alloc::raw_vec::RawVec;
63 use alloc::boxed::Box;
64 use alloc::heap::EMPTY;
65 use core::cmp::Ordering;
67 use core::hash::{self, Hash};
68 use core::intrinsics::{arith_offset, assume, needs_drop};
69 use core::iter::FromIterator;
71 use core::ops::{Index, IndexMut};
77 use borrow::{Cow, IntoCow};
79 use super::range::RangeArgument;
81 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector.'
86 /// let mut vec = Vec::new();
90 /// assert_eq!(vec.len(), 2);
91 /// assert_eq!(vec[0], 1);
93 /// assert_eq!(vec.pop(), Some(2));
94 /// assert_eq!(vec.len(), 1);
97 /// assert_eq!(vec[0], 7);
99 /// vec.extend([1, 2, 3].iter().cloned());
102 /// println!("{}", x);
104 /// assert_eq!(vec, [7, 1, 2, 3]);
107 /// The `vec!` macro is provided to make initialization more convenient:
110 /// let mut vec = vec![1, 2, 3];
112 /// assert_eq!(vec, [1, 2, 3, 4]);
115 /// It can also initialize each element of a `Vec<T>` with a given value:
118 /// let vec = vec![0; 5];
119 /// assert_eq!(vec, [0, 0, 0, 0, 0]);
122 /// Use a `Vec<T>` as an efficient stack:
125 /// let mut stack = Vec::new();
131 /// while let Some(top) = stack.pop() {
132 /// // Prints 3, 2, 1
133 /// println!("{}", top);
137 /// # Capacity and reallocation
139 /// The capacity of a vector is the amount of space allocated for any future
140 /// elements that will be added onto the vector. This is not to be confused with
141 /// the *length* of a vector, which specifies the number of actual elements
142 /// within the vector. If a vector's length exceeds its capacity, its capacity
143 /// will automatically be increased, but its elements will have to be
146 /// For example, a vector with capacity 10 and length 0 would be an empty vector
147 /// with space for 10 more elements. Pushing 10 or fewer elements onto the
148 /// vector will not change its capacity or cause reallocation to occur. However,
149 /// if the vector's length is increased to 11, it will have to reallocate, which
150 /// can be slow. For this reason, it is recommended to use `Vec::with_capacity`
151 /// whenever possible to specify how big the vector is expected to get.
155 /// Due to its incredibly fundamental nature, Vec makes a lot of guarantees
156 /// about its design. This ensures that it's as low-overhead as possible in
157 /// the general case, and can be correctly manipulated in primitive ways
158 /// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`.
159 /// If additional type parameters are added (e.g. to support custom allocators),
160 /// overriding their defaults may change the behavior.
162 /// Most fundamentally, Vec is and always will be a (pointer, capacity, length)
163 /// triplet. No more, no less. The order of these fields is completely
164 /// unspecified, and you should use the appropriate methods to modify these.
165 /// The pointer will never be null, so this type is null-pointer-optimized.
167 /// However, the pointer may not actually point to allocated memory. In particular,
168 /// if you construct a Vec with capacity 0 via `Vec::new()`, `vec![]`,
169 /// `Vec::with_capacity(0)`, or by calling `shrink_to_fit()` on an empty Vec, it
170 /// will not allocate memory. Similarly, if you store zero-sized types inside
171 /// a Vec, it will not allocate space for them. *Note that in this case the
172 /// Vec may not report a `capacity()` of 0*. Vec will allocate if and only
173 /// if `mem::size_of::<T>() * capacity() > 0`. In general, Vec's allocation
174 /// details are subtle enough that it is strongly recommended that you only
175 /// free memory allocated by a Vec by creating a new Vec and dropping it.
177 /// If a Vec *has* allocated memory, then the memory it points to is on the heap
178 /// (as defined by the allocator Rust is configured to use by default), and its
179 /// pointer points to `len()` initialized elements in order (what you would see
180 /// if you coerced it to a slice), followed by `capacity() - len()` logically
181 /// uninitialized elements.
183 /// Vec will never perform a "small optimization" where elements are actually
184 /// stored on the stack for two reasons:
186 /// * It would make it more difficult for unsafe code to correctly manipulate
187 /// a Vec. The contents of a Vec wouldn't have a stable address if it were
188 /// only moved, and it would be more difficult to determine if a Vec had
189 /// actually allocated memory.
191 /// * It would penalize the general case, incurring an additional branch
194 /// Vec will never automatically shrink itself, even if completely empty. This
195 /// ensures no unnecessary allocations or deallocations occur. Emptying a Vec
196 /// and then filling it back up to the same `len()` should incur no calls to
197 /// the allocator. If you wish to free up unused memory, use `shrink_to_fit`.
199 /// `push` and `insert` will never (re)allocate if the reported capacity is
200 /// sufficient. `push` and `insert` *will* (re)allocate if `len() == capacity()`.
201 /// That is, the reported capacity is completely accurate, and can be relied on.
202 /// It can even be used to manually free the memory allocated by a Vec if
203 /// desired. Bulk insertion methods *may* reallocate, even when not necessary.
205 /// Vec does not guarantee any particular growth strategy when reallocating
206 /// when full, nor when `reserve` is called. The current strategy is basic
207 /// and it may prove desirable to use a non-constant growth factor. Whatever
208 /// strategy is used will of course guarantee `O(1)` amortized `push`.
210 /// `vec![x; n]`, `vec![a, b, c, d]`, and `Vec::with_capacity(n)`, will all
211 /// produce a Vec with exactly the requested capacity. If `len() == capacity()`,
212 /// (as is the case for the `vec!` macro), then a `Vec<T>` can be converted
213 /// to and from a `Box<[T]>` without reallocating or moving the elements.
215 /// Vec will not specifically overwrite any data that is removed from it,
216 /// but also won't specifically preserve it. Its uninitialized memory is
217 /// scratch space that it may use however it wants. It will generally just do
218 /// whatever is most efficient or otherwise easy to implement. Do not rely on
219 /// removed data to be erased for security purposes. Even if you drop a Vec, its
220 /// buffer may simply be reused by another Vec. Even if you zero a Vec's memory
221 /// first, that may not actually happen because the optimizer does not consider
222 /// this a side-effect that must be preserved.
224 /// Vec does not currently guarantee the order in which elements are dropped
225 /// (the order has changed in the past, and may change again).
227 #[unsafe_no_drop_flag]
228 #[stable(feature = "rust1", since = "1.0.0")]
234 ////////////////////////////////////////////////////////////////////////////////
236 ////////////////////////////////////////////////////////////////////////////////
239 /// Constructs a new, empty `Vec<T>`.
241 /// The vector will not allocate until elements are pushed onto it.
246 /// # #![allow(unused_mut)]
247 /// let mut vec: Vec<i32> = Vec::new();
250 #[stable(feature = "rust1", since = "1.0.0")]
251 pub fn new() -> Vec<T> {
258 /// Constructs a new, empty `Vec<T>` with the specified capacity.
260 /// The vector will be able to hold exactly `capacity` elements without
261 /// reallocating. If `capacity` is 0, the vector will not allocate.
263 /// It is important to note that this function does not specify the *length*
264 /// of the returned vector, but only the *capacity*. (For an explanation of
265 /// the difference between length and capacity, see the main `Vec<T>` docs
266 /// above, 'Capacity and reallocation'.)
271 /// let mut vec = Vec::with_capacity(10);
273 /// // The vector contains no items, even though it has capacity for more
274 /// assert_eq!(vec.len(), 0);
276 /// // These are all done without reallocating...
281 /// // ...but this may make the vector reallocate
285 #[stable(feature = "rust1", since = "1.0.0")]
286 pub fn with_capacity(capacity: usize) -> Vec<T> {
288 buf: RawVec::with_capacity(capacity),
293 /// Creates a `Vec<T>` directly from the raw components of another vector.
297 /// This is highly unsafe, due to the number of invariants that aren't
300 /// * `ptr` needs to have been previously allocated via `String`/`Vec<T>`
301 /// (at least, it's highly likely to be incorrect if it wasn't).
302 /// * `length` needs to be the length that less than or equal to `capacity`.
303 /// * `capacity` needs to be the capacity that the pointer was allocated with.
305 /// Violating these may cause problems like corrupting the allocator's
306 /// internal datastructures.
315 /// let mut v = vec![1, 2, 3];
317 /// // Pull out the various important pieces of information about `v`
318 /// let p = v.as_mut_ptr();
319 /// let len = v.len();
320 /// let cap = v.capacity();
323 /// // Cast `v` into the void: no destructor run, so we are in
324 /// // complete control of the allocation to which `p` points.
327 /// // Overwrite memory with 4, 5, 6
328 /// for i in 0..len as isize {
329 /// ptr::write(p.offset(i), 4 + i);
332 /// // Put everything back together into a Vec
333 /// let rebuilt = Vec::from_raw_parts(p, len, cap);
334 /// assert_eq!(rebuilt, [4, 5, 6]);
338 #[stable(feature = "rust1", since = "1.0.0")]
339 pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T> {
341 buf: RawVec::from_raw_parts(ptr, capacity),
346 /// Returns the number of elements the vector can hold without
352 /// let vec: Vec<i32> = Vec::with_capacity(10);
353 /// assert_eq!(vec.capacity(), 10);
356 #[stable(feature = "rust1", since = "1.0.0")]
357 pub fn capacity(&self) -> usize {
361 /// Reserves capacity for at least `additional` more elements to be inserted
362 /// in the given `Vec<T>`. The collection may reserve more space to avoid
363 /// frequent reallocations.
367 /// Panics if the new capacity overflows `usize`.
372 /// let mut vec = vec![1];
374 /// assert!(vec.capacity() >= 11);
376 #[stable(feature = "rust1", since = "1.0.0")]
377 pub fn reserve(&mut self, additional: usize) {
378 self.buf.reserve(self.len, additional);
381 /// Reserves the minimum capacity for exactly `additional` more elements to
382 /// be inserted in the given `Vec<T>`. Does nothing if the capacity is already
385 /// Note that the allocator may give the collection more space than it
386 /// requests. Therefore capacity can not be relied upon to be precisely
387 /// minimal. Prefer `reserve` if future insertions are expected.
391 /// Panics if the new capacity overflows `usize`.
396 /// let mut vec = vec![1];
397 /// vec.reserve_exact(10);
398 /// assert!(vec.capacity() >= 11);
400 #[stable(feature = "rust1", since = "1.0.0")]
401 pub fn reserve_exact(&mut self, additional: usize) {
402 self.buf.reserve_exact(self.len, additional);
405 /// Shrinks the capacity of the vector as much as possible.
407 /// It will drop down as close as possible to the length but the allocator
408 /// may still inform the vector that there is space for a few more elements.
413 /// let mut vec = Vec::with_capacity(10);
414 /// vec.extend([1, 2, 3].iter().cloned());
415 /// assert_eq!(vec.capacity(), 10);
416 /// vec.shrink_to_fit();
417 /// assert!(vec.capacity() >= 3);
419 #[stable(feature = "rust1", since = "1.0.0")]
420 pub fn shrink_to_fit(&mut self) {
421 self.buf.shrink_to_fit(self.len);
424 /// Converts the vector into Box<[T]>.
426 /// Note that this will drop any excess capacity. Calling this and
427 /// converting back to a vector with `into_vec()` is equivalent to calling
428 /// `shrink_to_fit()`.
429 #[stable(feature = "rust1", since = "1.0.0")]
430 pub fn into_boxed_slice(mut self) -> Box<[T]> {
432 self.shrink_to_fit();
433 let buf = ptr::read(&self.buf);
439 /// Shorten a vector to be `len` elements long, dropping excess elements.
441 /// If `len` is greater than the vector's current length, this has no
447 /// let mut vec = vec![1, 2, 3, 4, 5];
449 /// assert_eq!(vec, [1, 2]);
451 #[stable(feature = "rust1", since = "1.0.0")]
452 pub fn truncate(&mut self, len: usize) {
454 // drop any extra elements
455 while len < self.len {
456 // decrement len before the read(), so a panic on Drop doesn't
457 // re-drop the just-failed value.
459 ptr::read(self.get_unchecked(self.len));
464 /// Extracts a slice containing the entire vector.
466 /// Equivalent to `&s[..]`.
468 #[stable(feature = "vec_as_slice", since = "1.7.0")]
469 pub fn as_slice(&self) -> &[T] {
473 /// Extracts a mutable slice of the entire vector.
475 /// Equivalent to `&mut s[..]`.
477 #[stable(feature = "vec_as_slice", since = "1.7.0")]
478 pub fn as_mut_slice(&mut self) -> &mut [T] {
482 /// Sets the length of a vector.
484 /// This will explicitly set the size of the vector, without actually
485 /// modifying its buffers, so it is up to the caller to ensure that the
486 /// vector is actually the specified size.
491 /// let mut v = vec![1, 2, 3, 4];
497 #[stable(feature = "rust1", since = "1.0.0")]
498 pub unsafe fn set_len(&mut self, len: usize) {
502 /// Removes an element from anywhere in the vector and return it, replacing
503 /// it with the last element.
505 /// This does not preserve ordering, but is O(1).
509 /// Panics if `index` is out of bounds.
514 /// let mut v = vec!["foo", "bar", "baz", "qux"];
516 /// assert_eq!(v.swap_remove(1), "bar");
517 /// assert_eq!(v, ["foo", "qux", "baz"]);
519 /// assert_eq!(v.swap_remove(0), "foo");
520 /// assert_eq!(v, ["baz", "qux"]);
523 #[stable(feature = "rust1", since = "1.0.0")]
524 pub fn swap_remove(&mut self, index: usize) -> T {
525 let length = self.len();
526 self.swap(index, length - 1);
530 /// Inserts an element at position `index` within the vector, shifting all
531 /// elements after it to the right.
535 /// Panics if `index` is greater than the vector's length.
540 /// let mut vec = vec![1, 2, 3];
541 /// vec.insert(1, 4);
542 /// assert_eq!(vec, [1, 4, 2, 3]);
543 /// vec.insert(4, 5);
544 /// assert_eq!(vec, [1, 4, 2, 3, 5]);
546 #[stable(feature = "rust1", since = "1.0.0")]
547 pub fn insert(&mut self, index: usize, element: T) {
548 let len = self.len();
549 assert!(index <= len);
551 // space for the new element
552 if len == self.buf.cap() {
558 // The spot to put the new value
560 let p = self.as_mut_ptr().offset(index as isize);
561 // Shift everything over to make space. (Duplicating the
562 // `index`th element into two consecutive places.)
563 ptr::copy(p, p.offset(1), len - index);
564 // Write it in, overwriting the first copy of the `index`th
566 ptr::write(p, element);
568 self.set_len(len + 1);
572 /// Removes and returns the element at position `index` within the vector,
573 /// shifting all elements after it to the left.
577 /// Panics if `index` is out of bounds.
582 /// let mut v = vec![1, 2, 3];
583 /// assert_eq!(v.remove(1), 2);
584 /// assert_eq!(v, [1, 3]);
586 #[stable(feature = "rust1", since = "1.0.0")]
587 pub fn remove(&mut self, index: usize) -> T {
588 let len = self.len();
589 assert!(index < len);
594 // the place we are taking from.
595 let ptr = self.as_mut_ptr().offset(index as isize);
596 // copy it out, unsafely having a copy of the value on
597 // the stack and in the vector at the same time.
598 ret = ptr::read(ptr);
600 // Shift everything down to fill in that spot.
601 ptr::copy(ptr.offset(1), ptr, len - index - 1);
603 self.set_len(len - 1);
608 /// Retains only the elements specified by the predicate.
610 /// In other words, remove all elements `e` such that `f(&e)` returns false.
611 /// This method operates in place and preserves the order of the retained
617 /// let mut vec = vec![1, 2, 3, 4];
618 /// vec.retain(|&x| x%2 == 0);
619 /// assert_eq!(vec, [2, 4]);
621 #[stable(feature = "rust1", since = "1.0.0")]
622 pub fn retain<F>(&mut self, mut f: F)
623 where F: FnMut(&T) -> bool
625 let len = self.len();
639 self.truncate(len - del);
643 /// Appends an element to the back of a collection.
647 /// Panics if the number of elements in the vector overflows a `usize`.
652 /// let mut vec = vec![1, 2];
654 /// assert_eq!(vec, [1, 2, 3]);
657 #[stable(feature = "rust1", since = "1.0.0")]
658 pub fn push(&mut self, value: T) {
659 // This will panic or abort if we would allocate > isize::MAX bytes
660 // or if the length increment would overflow for zero-sized types.
661 if self.len == self.buf.cap() {
665 let end = self.as_mut_ptr().offset(self.len as isize);
666 ptr::write(end, value);
671 /// Removes the last element from a vector and returns it, or `None` if it
677 /// let mut vec = vec![1, 2, 3];
678 /// assert_eq!(vec.pop(), Some(3));
679 /// assert_eq!(vec, [1, 2]);
682 #[stable(feature = "rust1", since = "1.0.0")]
683 pub fn pop(&mut self) -> Option<T> {
689 Some(ptr::read(self.get_unchecked(self.len())))
694 /// Moves all the elements of `other` into `Self`, leaving `other` empty.
698 /// Panics if the number of elements in the vector overflows a `usize`.
703 /// let mut vec = vec![1, 2, 3];
704 /// let mut vec2 = vec![4, 5, 6];
705 /// vec.append(&mut vec2);
706 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
707 /// assert_eq!(vec2, []);
710 #[stable(feature = "append", since = "1.4.0")]
711 pub fn append(&mut self, other: &mut Self) {
712 self.reserve(other.len());
713 let len = self.len();
715 ptr::copy_nonoverlapping(other.as_ptr(), self.get_unchecked_mut(len), other.len());
718 self.len += other.len();
724 /// Create a draining iterator that removes the specified range in the vector
725 /// and yields the removed items.
727 /// Note 1: The element range is removed even if the iterator is not
728 /// consumed until the end.
730 /// Note 2: It is unspecified how many elements are removed from the vector,
731 /// if the `Drain` value is leaked.
735 /// Panics if the starting point is greater than the end point or if
736 /// the end point is greater than the length of the vector.
741 /// let mut v = vec![1, 2, 3];
742 /// let u: Vec<_> = v.drain(1..).collect();
743 /// assert_eq!(v, &[1]);
744 /// assert_eq!(u, &[2, 3]);
746 /// // A full range clears the vector
748 /// assert_eq!(v, &[]);
750 #[stable(feature = "drain", since = "1.6.0")]
751 pub fn drain<R>(&mut self, range: R) -> Drain<T>
752 where R: RangeArgument<usize>
756 // When the Drain is first created, it shortens the length of
757 // the source vector to make sure no uninitalized or moved-from elements
758 // are accessible at all if the Drain's destructor never gets to run.
760 // Drain will ptr::read out the values to remove.
761 // When finished, remaining tail of the vec is copied back to cover
762 // the hole, and the vector length is restored to the new length.
764 let len = self.len();
765 let start = *range.start().unwrap_or(&0);
766 let end = *range.end().unwrap_or(&len);
767 assert!(start <= end);
771 // set self.vec length's to start, to be safe in case Drain is leaked
773 // Use the borrow in the IterMut to indicate borrowing behavior of the
774 // whole Drain iterator (like &mut T).
775 let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().offset(start as isize),
780 iter: range_slice.iter_mut(),
786 /// Clears the vector, removing all values.
791 /// let mut v = vec![1, 2, 3];
795 /// assert!(v.is_empty());
798 #[stable(feature = "rust1", since = "1.0.0")]
799 pub fn clear(&mut self) {
803 /// Returns the number of elements in the vector.
808 /// let a = vec![1, 2, 3];
809 /// assert_eq!(a.len(), 3);
812 #[stable(feature = "rust1", since = "1.0.0")]
813 pub fn len(&self) -> usize {
817 /// Returns `true` if the vector contains no elements.
822 /// let mut v = Vec::new();
823 /// assert!(v.is_empty());
826 /// assert!(!v.is_empty());
828 #[stable(feature = "rust1", since = "1.0.0")]
829 pub fn is_empty(&self) -> bool {
833 /// Splits the collection into two at the given index.
835 /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`,
836 /// and the returned `Self` contains elements `[at, len)`.
838 /// Note that the capacity of `self` does not change.
842 /// Panics if `at > len`.
847 /// let mut vec = vec![1,2,3];
848 /// let vec2 = vec.split_off(1);
849 /// assert_eq!(vec, [1]);
850 /// assert_eq!(vec2, [2, 3]);
853 #[stable(feature = "split_off", since = "1.4.0")]
854 pub fn split_off(&mut self, at: usize) -> Self {
855 assert!(at <= self.len(), "`at` out of bounds");
857 let other_len = self.len - at;
858 let mut other = Vec::with_capacity(other_len);
860 // Unsafely `set_len` and copy items to `other`.
863 other.set_len(other_len);
865 ptr::copy_nonoverlapping(self.as_ptr().offset(at as isize),
873 impl<T: Clone> Vec<T> {
874 /// Resizes the `Vec` in-place so that `len()` is equal to `new_len`.
876 /// If `new_len` is greater than `len()`, the `Vec` is extended by the
877 /// difference, with each additional slot filled with `value`.
878 /// If `new_len` is less than `len()`, the `Vec` is simply truncated.
883 /// let mut vec = vec!["hello"];
884 /// vec.resize(3, "world");
885 /// assert_eq!(vec, ["hello", "world", "world"]);
887 /// let mut vec = vec![1, 2, 3, 4];
888 /// vec.resize(2, 0);
889 /// assert_eq!(vec, [1, 2]);
891 #[stable(feature = "vec_resize", since = "1.5.0")]
892 pub fn resize(&mut self, new_len: usize, value: T) {
893 let len = self.len();
896 self.extend_with_element(new_len - len, value);
898 self.truncate(new_len);
902 /// Extend the vector by `n` additional clones of `value`.
903 fn extend_with_element(&mut self, n: usize, value: T) {
907 let len = self.len();
908 let mut ptr = self.as_mut_ptr().offset(len as isize);
909 // Write all elements except the last one
911 ptr::write(ptr, value.clone());
913 // Increment the length in every step in case clone() panics
914 self.set_len(len + i);
918 // We can write the last element directly without cloning needlessly
919 ptr::write(ptr, value);
920 self.set_len(len + n);
925 #[allow(missing_docs)]
927 #[unstable(feature = "vec_push_all",
928 reason = "likely to be replaced by a more optimized extend",
930 #[rustc_deprecated(reason = "renamed to extend_from_slice",
932 pub fn push_all(&mut self, other: &[T]) {
933 self.extend_from_slice(other)
936 /// Appends all elements in a slice to the `Vec`.
938 /// Iterates over the slice `other`, clones each element, and then appends
939 /// it to this `Vec`. The `other` vector is traversed in-order.
941 /// Note that this function is same as `extend` except that it is
942 /// specialized to work with slices instead. If and when Rust gets
943 /// specialization this function will likely be deprecated (but still
949 /// let mut vec = vec![1];
950 /// vec.extend_from_slice(&[2, 3, 4]);
951 /// assert_eq!(vec, [1, 2, 3, 4]);
953 #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
954 pub fn extend_from_slice(&mut self, other: &[T]) {
955 self.reserve(other.len());
957 for i in 0..other.len() {
958 let len = self.len();
960 // Unsafe code so this can be optimised to a memcpy (or something
961 // similarly fast) when T is Copy. LLVM is easily confused, so any
962 // extra operations during the loop can prevent this optimisation.
964 ptr::write(self.get_unchecked_mut(len), other.get_unchecked(i).clone());
965 self.set_len(len + 1);
971 impl<T: PartialEq> Vec<T> {
972 /// Removes consecutive repeated elements in the vector.
974 /// If the vector is sorted, this removes all duplicates.
979 /// let mut vec = vec![1, 2, 2, 3, 2];
983 /// assert_eq!(vec, [1, 2, 3, 2]);
985 #[stable(feature = "rust1", since = "1.0.0")]
986 pub fn dedup(&mut self) {
988 // Although we have a mutable reference to `self`, we cannot make
989 // *arbitrary* changes. The `PartialEq` comparisons could panic, so we
990 // must ensure that the vector is in a valid state at all time.
992 // The way that we handle this is by using swaps; we iterate
993 // over all the elements, swapping as we go so that at the end
994 // the elements we wish to keep are in the front, and those we
995 // wish to reject are at the back. We can then truncate the
996 // vector. This operation is still O(n).
998 // Example: We start in this state, where `r` represents "next
999 // read" and `w` represents "next_write`.
1002 // +---+---+---+---+---+---+
1003 // | 0 | 1 | 1 | 2 | 3 | 3 |
1004 // +---+---+---+---+---+---+
1007 // Comparing self[r] against self[w-1], this is not a duplicate, so
1008 // we swap self[r] and self[w] (no effect as r==w) and then increment both
1009 // r and w, leaving us with:
1012 // +---+---+---+---+---+---+
1013 // | 0 | 1 | 1 | 2 | 3 | 3 |
1014 // +---+---+---+---+---+---+
1017 // Comparing self[r] against self[w-1], this value is a duplicate,
1018 // so we increment `r` but leave everything else unchanged:
1021 // +---+---+---+---+---+---+
1022 // | 0 | 1 | 1 | 2 | 3 | 3 |
1023 // +---+---+---+---+---+---+
1026 // Comparing self[r] against self[w-1], this is not a duplicate,
1027 // so swap self[r] and self[w] and advance r and w:
1030 // +---+---+---+---+---+---+
1031 // | 0 | 1 | 2 | 1 | 3 | 3 |
1032 // +---+---+---+---+---+---+
1035 // Not a duplicate, repeat:
1038 // +---+---+---+---+---+---+
1039 // | 0 | 1 | 2 | 3 | 1 | 3 |
1040 // +---+---+---+---+---+---+
1043 // Duplicate, advance r. End of vec. Truncate to w.
1045 let ln = self.len();
1050 // Avoid bounds checks by using raw pointers.
1051 let p = self.as_mut_ptr();
1052 let mut r: usize = 1;
1053 let mut w: usize = 1;
1056 let p_r = p.offset(r as isize);
1057 let p_wm1 = p.offset((w - 1) as isize);
1060 let p_w = p_wm1.offset(1);
1061 mem::swap(&mut *p_r, &mut *p_w);
1073 ////////////////////////////////////////////////////////////////////////////////
1074 // Internal methods and functions
1075 ////////////////////////////////////////////////////////////////////////////////
1078 #[stable(feature = "rust1", since = "1.0.0")]
1079 pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
1080 let mut v = Vec::with_capacity(n);
1081 v.extend_with_element(n, elem);
1085 ////////////////////////////////////////////////////////////////////////////////
1086 // Common trait implementations for Vec
1087 ////////////////////////////////////////////////////////////////////////////////
1089 #[stable(feature = "rust1", since = "1.0.0")]
1090 impl<T: Clone> Clone for Vec<T> {
1092 fn clone(&self) -> Vec<T> {
1093 <[T]>::to_vec(&**self)
1096 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
1097 // required for this method definition, is not available. Instead use the
1098 // `slice::to_vec` function which is only available with cfg(test)
1099 // NB see the slice::hack module in slice.rs for more information
1101 fn clone(&self) -> Vec<T> {
1102 ::slice::to_vec(&**self)
1105 fn clone_from(&mut self, other: &Vec<T>) {
1106 // drop anything in self that will not be overwritten
1107 self.truncate(other.len());
1108 let len = self.len();
1110 // reuse the contained values' allocations/resources.
1111 self.clone_from_slice(&other[..len]);
1113 // self.len <= other.len due to the truncate above, so the
1114 // slice here is always in-bounds.
1115 self.extend_from_slice(&other[len..]);
1119 #[stable(feature = "rust1", since = "1.0.0")]
1120 impl<T: Hash> Hash for Vec<T> {
1122 fn hash<H: hash::Hasher>(&self, state: &mut H) {
1123 Hash::hash(&**self, state)
1127 #[stable(feature = "rust1", since = "1.0.0")]
1128 impl<T> Index<usize> for Vec<T> {
1132 fn index(&self, index: usize) -> &T {
1133 // NB built-in indexing via `&[T]`
1138 #[stable(feature = "rust1", since = "1.0.0")]
1139 impl<T> IndexMut<usize> for Vec<T> {
1141 fn index_mut(&mut self, index: usize) -> &mut T {
1142 // NB built-in indexing via `&mut [T]`
1143 &mut (**self)[index]
1148 #[stable(feature = "rust1", since = "1.0.0")]
1149 impl<T> ops::Index<ops::Range<usize>> for Vec<T> {
1153 fn index(&self, index: ops::Range<usize>) -> &[T] {
1154 Index::index(&**self, index)
1157 #[stable(feature = "rust1", since = "1.0.0")]
1158 impl<T> ops::Index<ops::RangeTo<usize>> for Vec<T> {
1162 fn index(&self, index: ops::RangeTo<usize>) -> &[T] {
1163 Index::index(&**self, index)
1166 #[stable(feature = "rust1", since = "1.0.0")]
1167 impl<T> ops::Index<ops::RangeFrom<usize>> for Vec<T> {
1171 fn index(&self, index: ops::RangeFrom<usize>) -> &[T] {
1172 Index::index(&**self, index)
1175 #[stable(feature = "rust1", since = "1.0.0")]
1176 impl<T> ops::Index<ops::RangeFull> for Vec<T> {
1180 fn index(&self, _index: ops::RangeFull) -> &[T] {
1185 #[stable(feature = "rust1", since = "1.0.0")]
1186 impl<T> ops::IndexMut<ops::Range<usize>> for Vec<T> {
1188 fn index_mut(&mut self, index: ops::Range<usize>) -> &mut [T] {
1189 IndexMut::index_mut(&mut **self, index)
1192 #[stable(feature = "rust1", since = "1.0.0")]
1193 impl<T> ops::IndexMut<ops::RangeTo<usize>> for Vec<T> {
1195 fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut [T] {
1196 IndexMut::index_mut(&mut **self, index)
1199 #[stable(feature = "rust1", since = "1.0.0")]
1200 impl<T> ops::IndexMut<ops::RangeFrom<usize>> for Vec<T> {
1202 fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut [T] {
1203 IndexMut::index_mut(&mut **self, index)
1206 #[stable(feature = "rust1", since = "1.0.0")]
1207 impl<T> ops::IndexMut<ops::RangeFull> for Vec<T> {
1209 fn index_mut(&mut self, _index: ops::RangeFull) -> &mut [T] {
1214 #[stable(feature = "rust1", since = "1.0.0")]
1215 impl<T> ops::Deref for Vec<T> {
1218 fn deref(&self) -> &[T] {
1220 let p = self.buf.ptr();
1221 assume(!p.is_null());
1222 slice::from_raw_parts(p, self.len)
1227 #[stable(feature = "rust1", since = "1.0.0")]
1228 impl<T> ops::DerefMut for Vec<T> {
1229 fn deref_mut(&mut self) -> &mut [T] {
1231 let ptr = self.buf.ptr();
1232 assume(!ptr.is_null());
1233 slice::from_raw_parts_mut(ptr, self.len)
1238 #[stable(feature = "rust1", since = "1.0.0")]
1239 impl<T> FromIterator<T> for Vec<T> {
1241 fn from_iter<I: IntoIterator<Item = T>>(iterable: I) -> Vec<T> {
1242 // Unroll the first iteration, as the vector is going to be
1243 // expanded on this iteration in every case when the iterable is not
1244 // empty, but the loop in extend_desugared() is not going to see the
1245 // vector being full in the few subsequent loop iterations.
1246 // So we get better branch prediction.
1247 let mut iterator = iterable.into_iter();
1248 let mut vector = match iterator.next() {
1249 None => return Vec::new(),
1251 let (lower, _) = iterator.size_hint();
1252 let mut vector = Vec::with_capacity(lower.saturating_add(1));
1254 ptr::write(vector.get_unchecked_mut(0), element);
1260 vector.extend_desugared(iterator);
1265 #[stable(feature = "rust1", since = "1.0.0")]
1266 impl<T> IntoIterator for Vec<T> {
1268 type IntoIter = IntoIter<T>;
1270 /// Creates a consuming iterator, that is, one that moves each value out of
1271 /// the vector (from start to end). The vector cannot be used after calling
1277 /// let v = vec!["a".to_string(), "b".to_string()];
1278 /// for s in v.into_iter() {
1279 /// // s has type String, not &String
1280 /// println!("{}", s);
1284 fn into_iter(mut self) -> IntoIter<T> {
1286 let ptr = self.as_mut_ptr();
1287 assume(!ptr.is_null());
1288 let begin = ptr as *const T;
1289 let end = if mem::size_of::<T>() == 0 {
1290 arith_offset(ptr as *const i8, self.len() as isize) as *const T
1292 ptr.offset(self.len() as isize) as *const T
1294 let buf = ptr::read(&self.buf);
1305 #[stable(feature = "rust1", since = "1.0.0")]
1306 impl<'a, T> IntoIterator for &'a Vec<T> {
1308 type IntoIter = slice::Iter<'a, T>;
1310 fn into_iter(self) -> slice::Iter<'a, T> {
1315 #[stable(feature = "rust1", since = "1.0.0")]
1316 impl<'a, T> IntoIterator for &'a mut Vec<T> {
1317 type Item = &'a mut T;
1318 type IntoIter = slice::IterMut<'a, T>;
1320 fn into_iter(mut self) -> slice::IterMut<'a, T> {
1325 #[stable(feature = "rust1", since = "1.0.0")]
1326 impl<T> Extend<T> for Vec<T> {
1328 fn extend<I: IntoIterator<Item = T>>(&mut self, iterable: I) {
1329 self.extend_desugared(iterable.into_iter())
1334 fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
1335 // This function should be the moral equivalent of:
1337 // for item in iterator {
1340 while let Some(element) = iterator.next() {
1341 let len = self.len();
1342 if len == self.capacity() {
1343 let (lower, _) = iterator.size_hint();
1344 self.reserve(lower.saturating_add(1));
1347 ptr::write(self.get_unchecked_mut(len), element);
1348 // NB can't overflow since we would have had to alloc the address space
1349 self.set_len(len + 1);
1355 #[stable(feature = "extend_ref", since = "1.2.0")]
1356 impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> {
1357 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
1358 self.extend(iter.into_iter().cloned());
1362 macro_rules! __impl_slice_eq1 {
1363 ($Lhs: ty, $Rhs: ty) => {
1364 __impl_slice_eq1! { $Lhs, $Rhs, Sized }
1366 ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
1367 #[stable(feature = "rust1", since = "1.0.0")]
1368 impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
1370 fn eq(&self, other: &$Rhs) -> bool { self[..] == other[..] }
1372 fn ne(&self, other: &$Rhs) -> bool { self[..] != other[..] }
1377 __impl_slice_eq1! { Vec<A>, Vec<B> }
1378 __impl_slice_eq1! { Vec<A>, &'b [B] }
1379 __impl_slice_eq1! { Vec<A>, &'b mut [B] }
1380 __impl_slice_eq1! { Cow<'a, [A]>, &'b [B], Clone }
1381 __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B], Clone }
1382 __impl_slice_eq1! { Cow<'a, [A]>, Vec<B>, Clone }
1384 macro_rules! array_impls {
1387 // NOTE: some less important impls are omitted to reduce code bloat
1388 __impl_slice_eq1! { Vec<A>, [B; $N] }
1389 __impl_slice_eq1! { Vec<A>, &'b [B; $N] }
1390 // __impl_slice_eq1! { Vec<A>, &'b mut [B; $N] }
1391 // __impl_slice_eq1! { Cow<'a, [A]>, [B; $N], Clone }
1392 // __impl_slice_eq1! { Cow<'a, [A]>, &'b [B; $N], Clone }
1393 // __impl_slice_eq1! { Cow<'a, [A]>, &'b mut [B; $N], Clone }
1400 10 11 12 13 14 15 16 17 18 19
1401 20 21 22 23 24 25 26 27 28 29
1405 #[stable(feature = "rust1", since = "1.0.0")]
1406 impl<T: PartialOrd> PartialOrd for Vec<T> {
1408 fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> {
1409 PartialOrd::partial_cmp(&**self, &**other)
1413 #[stable(feature = "rust1", since = "1.0.0")]
1414 impl<T: Eq> Eq for Vec<T> {}
1416 #[stable(feature = "rust1", since = "1.0.0")]
1417 impl<T: Ord> Ord for Vec<T> {
1419 fn cmp(&self, other: &Vec<T>) -> Ordering {
1420 Ord::cmp(&**self, &**other)
1424 #[stable(feature = "rust1", since = "1.0.0")]
1425 impl<T> Drop for Vec<T> {
1426 #[unsafe_destructor_blind_to_params]
1427 fn drop(&mut self) {
1428 if self.buf.unsafe_no_drop_flag_needs_drop() {
1430 // The branch on needs_drop() is an -O1 performance optimization.
1431 // Without the branch, dropping Vec<u8> takes linear time.
1432 if needs_drop::<T>() {
1433 for x in self.iter_mut() {
1434 ptr::drop_in_place(x);
1439 // RawVec handles deallocation
1443 #[stable(feature = "rust1", since = "1.0.0")]
1444 impl<T> Default for Vec<T> {
1445 fn default() -> Vec<T> {
1450 #[stable(feature = "rust1", since = "1.0.0")]
1451 impl<T: fmt::Debug> fmt::Debug for Vec<T> {
1452 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1453 fmt::Debug::fmt(&**self, f)
1457 #[stable(feature = "rust1", since = "1.0.0")]
1458 impl<T> AsRef<Vec<T>> for Vec<T> {
1459 fn as_ref(&self) -> &Vec<T> {
1464 #[stable(feature = "vec_as_mut", since = "1.5.0")]
1465 impl<T> AsMut<Vec<T>> for Vec<T> {
1466 fn as_mut(&mut self) -> &mut Vec<T> {
1471 #[stable(feature = "rust1", since = "1.0.0")]
1472 impl<T> AsRef<[T]> for Vec<T> {
1473 fn as_ref(&self) -> &[T] {
1478 #[stable(feature = "vec_as_mut", since = "1.5.0")]
1479 impl<T> AsMut<[T]> for Vec<T> {
1480 fn as_mut(&mut self) -> &mut [T] {
1485 #[stable(feature = "rust1", since = "1.0.0")]
1486 impl<'a, T: Clone> From<&'a [T]> for Vec<T> {
1488 fn from(s: &'a [T]) -> Vec<T> {
1492 fn from(s: &'a [T]) -> Vec<T> {
1497 #[stable(feature = "rust1", since = "1.0.0")]
1498 impl<'a> From<&'a str> for Vec<u8> {
1499 fn from(s: &'a str) -> Vec<u8> {
1500 From::from(s.as_bytes())
1504 ////////////////////////////////////////////////////////////////////////////////
1506 ////////////////////////////////////////////////////////////////////////////////
1508 #[stable(feature = "cow_from_vec", since = "1.7.0")]
1509 impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> {
1510 fn from(s: &'a [T]) -> Cow<'a, [T]> {
1515 #[stable(feature = "cow_from_vec", since = "1.7.0")]
1516 impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> {
1517 fn from(v: Vec<T>) -> Cow<'a, [T]> {
1522 #[stable(feature = "rust1", since = "1.0.0")]
1523 impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone {
1524 fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {
1525 Cow::Owned(FromIterator::from_iter(it))
1529 #[stable(feature = "rust1", since = "1.0.0")]
1530 #[allow(deprecated)]
1531 impl<'a, T: 'a> IntoCow<'a, [T]> for Vec<T> where T: Clone {
1532 fn into_cow(self) -> Cow<'a, [T]> {
1537 #[stable(feature = "rust1", since = "1.0.0")]
1538 #[allow(deprecated)]
1539 impl<'a, T> IntoCow<'a, [T]> for &'a [T] where T: Clone {
1540 fn into_cow(self) -> Cow<'a, [T]> {
1545 ////////////////////////////////////////////////////////////////////////////////
1547 ////////////////////////////////////////////////////////////////////////////////
1549 /// An iterator that moves out of a vector.
1550 #[stable(feature = "rust1", since = "1.0.0")]
1551 pub struct IntoIter<T> {
1557 #[stable(feature = "rust1", since = "1.0.0")]
1558 unsafe impl<T: Send> Send for IntoIter<T> {}
1559 #[stable(feature = "rust1", since = "1.0.0")]
1560 unsafe impl<T: Sync> Sync for IntoIter<T> {}
1562 #[stable(feature = "rust1", since = "1.0.0")]
1563 impl<T> Iterator for IntoIter<T> {
1567 fn next(&mut self) -> Option<T> {
1569 if self.ptr == self.end {
1572 if mem::size_of::<T>() == 0 {
1573 // purposefully don't use 'ptr.offset' because for
1574 // vectors with 0-size elements this would return the
1576 self.ptr = arith_offset(self.ptr as *const i8, 1) as *const T;
1578 // Use a non-null pointer value
1579 Some(ptr::read(EMPTY as *mut T))
1582 self.ptr = self.ptr.offset(1);
1584 Some(ptr::read(old))
1591 fn size_hint(&self) -> (usize, Option<usize>) {
1592 let diff = (self.end as usize) - (self.ptr as usize);
1593 let size = mem::size_of::<T>();
1600 (exact, Some(exact))
1604 fn count(self) -> usize {
1609 #[stable(feature = "rust1", since = "1.0.0")]
1610 impl<T> DoubleEndedIterator for IntoIter<T> {
1612 fn next_back(&mut self) -> Option<T> {
1614 if self.end == self.ptr {
1617 if mem::size_of::<T>() == 0 {
1618 // See above for why 'ptr.offset' isn't used
1619 self.end = arith_offset(self.end as *const i8, -1) as *const T;
1621 // Use a non-null pointer value
1622 Some(ptr::read(EMPTY as *mut T))
1624 self.end = self.end.offset(-1);
1626 Some(ptr::read(self.end))
1633 #[stable(feature = "rust1", since = "1.0.0")]
1634 impl<T> ExactSizeIterator for IntoIter<T> {}
1636 #[stable(feature = "rust1", since = "1.0.0")]
1637 impl<T> Drop for IntoIter<T> {
1638 #[unsafe_destructor_blind_to_params]
1639 fn drop(&mut self) {
1640 // destroy the remaining elements
1643 // RawVec handles deallocation
1647 /// A draining iterator for `Vec<T>`.
1648 #[stable(feature = "drain", since = "1.6.0")]
1649 pub struct Drain<'a, T: 'a> {
1650 /// Index of tail to preserve
1654 /// Current remaining range to remove
1655 iter: slice::IterMut<'a, T>,
1659 #[stable(feature = "drain", since = "1.6.0")]
1660 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
1661 #[stable(feature = "drain", since = "1.6.0")]
1662 unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
1664 #[stable(feature = "rust1", since = "1.0.0")]
1665 impl<'a, T> Iterator for Drain<'a, T> {
1669 fn next(&mut self) -> Option<T> {
1670 self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
1673 fn size_hint(&self) -> (usize, Option<usize>) {
1674 self.iter.size_hint()
1678 #[stable(feature = "rust1", since = "1.0.0")]
1679 impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
1681 fn next_back(&mut self) -> Option<T> {
1682 self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
1686 #[stable(feature = "rust1", since = "1.0.0")]
1687 impl<'a, T> Drop for Drain<'a, T> {
1688 fn drop(&mut self) {
1689 // exhaust self first
1690 while let Some(_) = self.next() {}
1692 if self.tail_len > 0 {
1694 let source_vec = &mut *self.vec;
1695 // memmove back untouched tail, update to new length
1696 let start = source_vec.len();
1697 let tail = self.tail_start;
1698 let src = source_vec.as_ptr().offset(tail as isize);
1699 let dst = source_vec.as_mut_ptr().offset(start as isize);
1700 ptr::copy(src, dst, self.tail_len);
1701 source_vec.set_len(start + self.tail_len);
1708 #[stable(feature = "rust1", since = "1.0.0")]
1709 impl<'a, T> ExactSizeIterator for Drain<'a, T> {}