/
vec.rs
2596 lines (2302 loc) · 74.6 KB
/
vec.rs
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! A growable list type, written `Vec<T>` but pronounced 'vector.'
//!
//! Vectors have `O(1)` indexing, push (to the end) and pop (from the end).
use core::prelude::*;
use alloc::boxed::Box;
use alloc::heap::{EMPTY, allocate, reallocate, deallocate};
use core::cmp::max;
use core::default::Default;
use core::fmt;
use core::kinds::marker::{ContravariantLifetime, InvariantType};
use core::mem;
use core::num::{Int, UnsignedInt};
use core::ops;
use core::ptr;
use core::raw::Slice as RawSlice;
use core::uint;
use slice::{CloneSliceAllocPrelude};
/// An owned, growable vector.
///
/// # Examples
///
/// ```
/// let mut vec = Vec::new();
/// vec.push(1i);
/// vec.push(2i);
///
/// assert_eq!(vec.len(), 2);
/// assert_eq!(vec[0], 1);
///
/// assert_eq!(vec.pop(), Some(2));
/// assert_eq!(vec.len(), 1);
///
/// vec[0] = 7i;
/// assert_eq!(vec[0], 7);
///
/// vec.push_all(&[1, 2, 3]);
///
/// for x in vec.iter() {
/// println!("{}", x);
/// }
/// assert_eq!(vec, vec![7i, 1, 2, 3]);
/// ```
///
/// The `vec!` macro is provided to make initialization more convenient:
///
/// ```
/// let mut vec = vec![1i, 2i, 3i];
/// vec.push(4);
/// assert_eq!(vec, vec![1, 2, 3, 4]);
/// ```
///
/// Use a `Vec` as an efficient stack:
///
/// ```
/// let mut stack = Vec::new();
///
/// stack.push(1i);
/// stack.push(2i);
/// stack.push(3i);
///
/// loop {
/// let top = match stack.pop() {
/// None => break, // empty
/// Some(x) => x,
/// };
/// // Prints 3, 2, 1
/// println!("{}", top);
/// }
/// ```
///
/// # Capacity and reallocation
///
/// The capacity of a vector is the amount of space allocated for any future
/// elements that will be added onto the vector. This is not to be confused
/// with the *length* of a vector, which specifies the number of actual
/// elements within the vector. If a vector's length exceeds its capacity,
/// its capacity will automatically be increased, but its elements will
/// have to be reallocated.
///
/// For example, a vector with capacity 10 and length 0 would be an empty
/// vector with space for 10 more elements. Pushing 10 or fewer elements onto
/// the vector will not change its capacity or cause reallocation to occur.
/// However, if the vector's length is increased to 11, it will have to
/// reallocate, which can be slow. For this reason, it is recommended
/// to use `Vec::with_capacity` whenever possible to specify how big the vector
/// is expected to get.
#[unsafe_no_drop_flag]
#[stable]
pub struct Vec<T> {
ptr: *mut T,
len: uint,
cap: uint,
}
impl<T> Vec<T> {
/// Constructs a new, empty `Vec`.
///
/// The vector will not allocate until elements are pushed onto it.
///
/// # Example
///
/// ```
/// let mut vec: Vec<int> = Vec::new();
/// ```
#[inline]
#[stable]
pub fn new() -> Vec<T> {
// We want ptr to never be NULL so instead we set it to some arbitrary
// non-null value which is fine since we never call deallocate on the ptr
// if cap is 0. The reason for this is because the pointer of a slice
// being NULL would break the null pointer optimization for enums.
Vec { ptr: EMPTY as *mut T, len: 0, cap: 0 }
}
/// Constructs a new, empty `Vec` with the specified capacity.
///
/// The vector will be able to hold exactly `capacity` elements without
/// reallocating. If `capacity` is 0, the vector will not allocate.
///
/// It is important to note that this function does not specify the
/// *length* of the returned vector, but only the *capacity*. (For an
/// explanation of the difference between length and capacity, see
/// the main `Vec` docs above, 'Capacity and reallocation'.) To create
/// a vector of a given length, use `Vec::from_elem` or `Vec::from_fn`.
///
/// # Example
///
/// ```
/// let mut vec: Vec<int> = Vec::with_capacity(10);
///
/// // The vector contains no items, even though it has capacity for more
/// assert_eq!(vec.len(), 0);
///
/// // These are all done without reallocating...
/// for i in range(0i, 10) {
/// vec.push(i);
/// }
///
/// // ...but this may make the vector reallocate
/// vec.push(11);
/// ```
#[inline]
#[stable]
pub fn with_capacity(capacity: uint) -> Vec<T> {
if mem::size_of::<T>() == 0 {
Vec { ptr: EMPTY as *mut T, len: 0, cap: uint::MAX }
} else if capacity == 0 {
Vec::new()
} else {
let size = capacity.checked_mul(mem::size_of::<T>())
.expect("capacity overflow");
let ptr = unsafe { allocate(size, mem::min_align_of::<T>()) };
Vec { ptr: ptr as *mut T, len: 0, cap: capacity }
}
}
/// Creates and initializes a `Vec`.
///
/// Creates a `Vec` of size `length` and initializes the elements to the
/// value returned by the closure `op`.
///
/// # Example
///
/// ```
/// let vec = Vec::from_fn(3, |idx| idx * 2);
/// assert_eq!(vec, vec![0, 2, 4]);
/// ```
#[inline]
#[unstable = "the naming is uncertain as well as this migrating to unboxed \
closures in the future"]
pub fn from_fn(length: uint, op: |uint| -> T) -> Vec<T> {
unsafe {
let mut xs = Vec::with_capacity(length);
while xs.len < length {
let len = xs.len;
ptr::write(xs.as_mut_slice().unsafe_mut(len), op(len));
xs.len += 1;
}
xs
}
}
/// Creates a `Vec<T>` directly from the raw constituents.
///
/// This is highly unsafe:
///
/// - if `ptr` is null, then `length` and `capacity` should be 0
/// - `ptr` must point to an allocation of size `capacity`
/// - there must be `length` valid instances of type `T` at the
/// beginning of that allocation
/// - `ptr` must be allocated by the default `Vec` allocator
///
/// # Example
///
/// ```
/// use std::ptr;
/// use std::mem;
///
/// fn main() {
/// let mut v = vec![1i, 2, 3];
///
/// // Pull out the various important pieces of information about `v`
/// let p = v.as_mut_ptr();
/// let len = v.len();
/// let cap = v.capacity();
///
/// unsafe {
/// // Cast `v` into the void: no destructor run, so we are in
/// // complete control of the allocation to which `p` points.
/// mem::forget(v);
///
/// // Overwrite memory with 4, 5, 6
/// for i in range(0, len as int) {
/// ptr::write(p.offset(i), 4 + i);
/// }
///
/// // Put everything back together into a Vec
/// let rebuilt = Vec::from_raw_parts(p, len, cap);
/// assert_eq!(rebuilt, vec![4i, 5i, 6i]);
/// }
/// }
/// ```
#[unstable = "needs finalization"]
pub unsafe fn from_raw_parts(ptr: *mut T, length: uint,
capacity: uint) -> Vec<T> {
Vec { ptr: ptr, len: length, cap: capacity }
}
/// Creates a vector by copying the elements from a raw pointer.
///
/// This function will copy `elts` contiguous elements starting at `ptr`
/// into a new allocation owned by the returned `Vec`. The elements of the
/// buffer are copied into the vector without cloning, as if `ptr::read()`
/// were called on them.
#[inline]
#[unstable = "just renamed from raw::from_buf"]
pub unsafe fn from_raw_buf(ptr: *const T, elts: uint) -> Vec<T> {
let mut dst = Vec::with_capacity(elts);
dst.set_len(elts);
ptr::copy_nonoverlapping_memory(dst.as_mut_ptr(), ptr, elts);
dst
}
/// Consumes the `Vec`, partitioning it based on a predicate.
///
/// Partitions the `Vec` into two `Vec`s `(A,B)`, where all elements of `A`
/// satisfy `f` and all elements of `B` do not. The order of elements is
/// preserved.
///
/// # Example
///
/// ```
/// let vec = vec![1i, 2i, 3i, 4i];
/// let (even, odd) = vec.partition(|&n| n % 2 == 0);
/// assert_eq!(even, vec![2, 4]);
/// assert_eq!(odd, vec![1, 3]);
/// ```
#[inline]
#[experimental]
pub fn partition(self, f: |&T| -> bool) -> (Vec<T>, Vec<T>) {
let mut lefts = Vec::new();
let mut rights = Vec::new();
for elt in self.into_iter() {
if f(&elt) {
lefts.push(elt);
} else {
rights.push(elt);
}
}
(lefts, rights)
}
}
impl<T: Clone> Vec<T> {
/// Constructs a `Vec` with copies of a value.
///
/// Creates a `Vec` with `length` copies of `value`.
///
/// # Example
/// ```
/// let vec = Vec::from_elem(3, "hi");
/// println!("{}", vec); // prints [hi, hi, hi]
/// ```
#[inline]
#[unstable = "this functionality may become more generic over all collections"]
pub fn from_elem(length: uint, value: T) -> Vec<T> {
unsafe {
let mut xs = Vec::with_capacity(length);
while xs.len < length {
let len = xs.len;
ptr::write(xs.as_mut_slice().unsafe_mut(len),
value.clone());
xs.len += 1;
}
xs
}
}
/// Appends all elements in a slice to the `Vec`.
///
/// Iterates over the slice `other`, clones each element, and then appends
/// it to this `Vec`. The `other` vector is traversed in-order.
///
/// # Example
///
/// ```
/// let mut vec = vec![1i];
/// vec.push_all(&[2i, 3, 4]);
/// assert_eq!(vec, vec![1, 2, 3, 4]);
/// ```
#[inline]
#[experimental]
pub fn push_all(&mut self, other: &[T]) {
self.reserve(other.len());
for i in range(0, other.len()) {
let len = self.len();
// Unsafe code so this can be optimised to a memcpy (or something similarly
// fast) when T is Copy. LLVM is easily confused, so any extra operations
// during the loop can prevent this optimisation.
unsafe {
ptr::write(
self.as_mut_slice().unsafe_mut(len),
other.unsafe_get(i).clone());
self.set_len(len + 1);
}
}
}
/// Grows the `Vec` in-place.
///
/// Adds `n` copies of `value` to the `Vec`.
///
/// # Example
///
/// ```
/// let mut vec = vec!["hello"];
/// vec.grow(2, "world");
/// assert_eq!(vec, vec!["hello", "world", "world"]);
/// ```
#[stable]
pub fn grow(&mut self, n: uint, value: T) {
self.reserve(n);
let mut i: uint = 0u;
while i < n {
self.push(value.clone());
i += 1u;
}
}
/// Partitions a vector based on a predicate.
///
/// Clones the elements of the vector, partitioning them into two `Vec`s
/// `(a, b)`, where all elements of `a` satisfy `f` and all elements of `b`
/// do not. The order of elements is preserved.
///
/// # Example
///
/// ```
/// let vec = vec![1i, 2, 3, 4];
/// let (even, odd) = vec.partitioned(|&n| n % 2 == 0);
/// assert_eq!(even, vec![2i, 4]);
/// assert_eq!(odd, vec![1i, 3]);
/// ```
#[experimental]
pub fn partitioned(&self, f: |&T| -> bool) -> (Vec<T>, Vec<T>) {
let mut lefts = Vec::new();
let mut rights = Vec::new();
for elt in self.iter() {
if f(elt) {
lefts.push(elt.clone());
} else {
rights.push(elt.clone());
}
}
(lefts, rights)
}
}
#[unstable]
impl<T:Clone> Clone for Vec<T> {
fn clone(&self) -> Vec<T> { self.as_slice().to_vec() }
fn clone_from(&mut self, other: &Vec<T>) {
// drop anything in self that will not be overwritten
if self.len() > other.len() {
self.truncate(other.len())
}
// reuse the contained values' allocations/resources.
for (place, thing) in self.iter_mut().zip(other.iter()) {
place.clone_from(thing)
}
// self.len <= other.len due to the truncate above, so the
// slice here is always in-bounds.
let slice = other[self.len()..];
self.push_all(slice);
}
}
#[experimental = "waiting on Index stability"]
impl<T> Index<uint,T> for Vec<T> {
#[inline]
fn index<'a>(&'a self, index: &uint) -> &'a T {
&self.as_slice()[*index]
}
}
impl<T> IndexMut<uint,T> for Vec<T> {
#[inline]
fn index_mut<'a>(&'a mut self, index: &uint) -> &'a mut T {
&mut self.as_mut_slice()[*index]
}
}
impl<T> ops::Slice<uint, [T]> for Vec<T> {
#[inline]
fn as_slice_<'a>(&'a self) -> &'a [T] {
self.as_slice()
}
#[inline]
fn slice_from_or_fail<'a>(&'a self, start: &uint) -> &'a [T] {
self.as_slice().slice_from_or_fail(start)
}
#[inline]
fn slice_to_or_fail<'a>(&'a self, end: &uint) -> &'a [T] {
self.as_slice().slice_to_or_fail(end)
}
#[inline]
fn slice_or_fail<'a>(&'a self, start: &uint, end: &uint) -> &'a [T] {
self.as_slice().slice_or_fail(start, end)
}
}
impl<T> ops::SliceMut<uint, [T]> for Vec<T> {
#[inline]
fn as_mut_slice_<'a>(&'a mut self) -> &'a mut [T] {
self.as_mut_slice()
}
#[inline]
fn slice_from_or_fail_mut<'a>(&'a mut self, start: &uint) -> &'a mut [T] {
self.as_mut_slice().slice_from_or_fail_mut(start)
}
#[inline]
fn slice_to_or_fail_mut<'a>(&'a mut self, end: &uint) -> &'a mut [T] {
self.as_mut_slice().slice_to_or_fail_mut(end)
}
#[inline]
fn slice_or_fail_mut<'a>(&'a mut self, start: &uint, end: &uint) -> &'a mut [T] {
self.as_mut_slice().slice_or_fail_mut(start, end)
}
}
#[experimental = "waiting on Deref stability"]
impl<T> ops::Deref<[T]> for Vec<T> {
fn deref<'a>(&'a self) -> &'a [T] { self.as_slice() }
}
#[experimental = "waiting on DerefMut stability"]
impl<T> ops::DerefMut<[T]> for Vec<T> {
fn deref_mut<'a>(&'a mut self) -> &'a mut [T] { self.as_mut_slice() }
}
#[experimental = "waiting on FromIterator stability"]
impl<T> FromIterator<T> for Vec<T> {
#[inline]
fn from_iter<I:Iterator<T>>(mut iterator: I) -> Vec<T> {
let (lower, _) = iterator.size_hint();
let mut vector = Vec::with_capacity(lower);
for element in iterator {
vector.push(element)
}
vector
}
}
#[experimental = "waiting on Extend stability"]
impl<T> Extend<T> for Vec<T> {
#[inline]
fn extend<I: Iterator<T>>(&mut self, mut iterator: I) {
let (lower, _) = iterator.size_hint();
self.reserve(lower);
for element in iterator {
self.push(element)
}
}
}
#[unstable = "waiting on PartialEq stability"]
impl<T: PartialEq> PartialEq for Vec<T> {
#[inline]
fn eq(&self, other: &Vec<T>) -> bool {
self.as_slice() == other.as_slice()
}
}
#[unstable = "waiting on PartialOrd stability"]
impl<T: PartialOrd> PartialOrd for Vec<T> {
#[inline]
fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> {
self.as_slice().partial_cmp(other.as_slice())
}
}
#[unstable = "waiting on Eq stability"]
impl<T: Eq> Eq for Vec<T> {}
#[experimental]
impl<T: PartialEq, V: AsSlice<T>> Equiv<V> for Vec<T> {
#[inline]
fn equiv(&self, other: &V) -> bool { self.as_slice() == other.as_slice() }
}
#[unstable = "waiting on Ord stability"]
impl<T: Ord> Ord for Vec<T> {
#[inline]
fn cmp(&self, other: &Vec<T>) -> Ordering {
self.as_slice().cmp(other.as_slice())
}
}
// FIXME: #13996: need a way to mark the return value as `noalias`
#[inline(never)]
unsafe fn alloc_or_realloc<T>(ptr: *mut T, old_size: uint, size: uint) -> *mut T {
if old_size == 0 {
allocate(size, mem::min_align_of::<T>()) as *mut T
} else {
reallocate(ptr as *mut u8, old_size, size, mem::min_align_of::<T>()) as *mut T
}
}
#[inline]
unsafe fn dealloc<T>(ptr: *mut T, len: uint) {
if mem::size_of::<T>() != 0 {
deallocate(ptr as *mut u8,
len * mem::size_of::<T>(),
mem::min_align_of::<T>())
}
}
impl<T> Vec<T> {
/// Returns the number of elements the vector can hold without
/// reallocating.
///
/// # Example
///
/// ```
/// let vec: Vec<int> = Vec::with_capacity(10);
/// assert_eq!(vec.capacity(), 10);
/// ```
#[inline]
#[stable]
pub fn capacity(&self) -> uint {
self.cap
}
/// Deprecated: Renamed to `reserve`.
#[deprecated = "Renamed to `reserve`"]
pub fn reserve_additional(&mut self, extra: uint) {
self.reserve(extra)
}
/// Reserves capacity for at least `additional` more elements to be inserted in the given
/// `Vec`. The collection may reserve more space to avoid frequent reallocations.
///
/// # Panics
///
/// Panics if the new capacity overflows `uint`.
///
/// # Example
///
/// ```
/// let mut vec: Vec<int> = vec![1];
/// vec.reserve(10);
/// assert!(vec.capacity() >= 11);
/// ```
#[unstable = "matches collection reform specification, waiting for dust to settle"]
pub fn reserve(&mut self, additional: uint) {
if self.cap - self.len < additional {
match self.len.checked_add(additional) {
None => panic!("Vec::reserve: `uint` overflow"),
// if the checked_add
Some(new_cap) => {
let amort_cap = new_cap.next_power_of_two();
// next_power_of_two will overflow to exactly 0 for really big capacities
if amort_cap == 0 {
self.grow_capacity(new_cap);
} else {
self.grow_capacity(amort_cap);
}
}
}
}
}
/// Reserves the minimum capacity for exactly `additional` more elements to be inserted in the
/// given `Vec`. Does nothing if the capacity is already sufficient.
///
/// Note that the allocator may give the collection more space than it requests. Therefore
/// capacity can not be relied upon to be precisely minimal. Prefer `reserve` if future
/// insertions are expected.
///
/// # Panics
///
/// Panics if the new capacity overflows `uint`.
///
/// # Example
///
/// ```
/// let mut vec: Vec<int> = vec![1];
/// vec.reserve_exact(10);
/// assert!(vec.capacity() >= 11);
/// ```
#[unstable = "matches collection reform specification, waiting for dust to settle"]
pub fn reserve_exact(&mut self, additional: uint) {
if self.cap - self.len < additional {
match self.len.checked_add(additional) {
None => panic!("Vec::reserve: `uint` overflow"),
Some(new_cap) => self.grow_capacity(new_cap)
}
}
}
/// Shrinks the capacity of the vector as much as possible. It will drop
/// down as close as possible to the length but the allocator may still
/// inform the vector that there is space for a few more elements.
///
/// # Example
///
/// ```
/// let mut vec: Vec<int> = Vec::with_capacity(10);
/// vec.push_all(&[1, 2, 3]);
/// assert_eq!(vec.capacity(), 10);
/// vec.shrink_to_fit();
/// assert!(vec.capacity() >= 3);
/// ```
#[stable]
pub fn shrink_to_fit(&mut self) {
if mem::size_of::<T>() == 0 { return }
if self.len == 0 {
if self.cap != 0 {
unsafe {
dealloc(self.ptr, self.cap)
}
self.cap = 0;
}
} else {
unsafe {
// Overflow check is unnecessary as the vector is already at
// least this large.
self.ptr = reallocate(self.ptr as *mut u8,
self.cap * mem::size_of::<T>(),
self.len * mem::size_of::<T>(),
mem::min_align_of::<T>()) as *mut T;
if self.ptr.is_null() { ::alloc::oom() }
}
self.cap = self.len;
}
}
/// Convert the vector into Box<[T]>.
///
/// Note that this will drop any excess capacity. Calling this and converting back to a vector
/// with `into_vec()` is equivalent to calling `shrink_to_fit()`.
#[experimental]
pub fn into_boxed_slice(mut self) -> Box<[T]> {
self.shrink_to_fit();
unsafe {
let xs: Box<[T]> = mem::transmute(self.as_mut_slice());
mem::forget(self);
xs
}
}
/// Shorten a vector, dropping excess elements.
///
/// If `len` is greater than the vector's current length, this has no
/// effect.
///
/// # Example
///
/// ```
/// let mut vec = vec![1i, 2, 3, 4];
/// vec.truncate(2);
/// assert_eq!(vec, vec![1, 2]);
/// ```
#[unstable = "matches collection reform specification; waiting on panic semantics"]
pub fn truncate(&mut self, len: uint) {
unsafe {
// drop any extra elements
while len < self.len {
// decrement len before the read(), so a panic on Drop doesn't
// re-drop the just-failed value.
self.len -= 1;
ptr::read(self.as_slice().unsafe_get(self.len));
}
}
}
/// Returns a mutable slice of the elements of `self`.
///
/// # Example
///
/// ```
/// fn foo(slice: &mut [int]) {}
///
/// let mut vec = vec![1i, 2];
/// foo(vec.as_mut_slice());
/// ```
#[inline]
#[stable]
pub fn as_mut_slice<'a>(&'a mut self) -> &'a mut [T] {
unsafe {
mem::transmute(RawSlice {
data: self.ptr as *const T,
len: self.len,
})
}
}
/// Creates a consuming iterator, that is, one that moves each
/// value out of the vector (from start to end). The vector cannot
/// be used after calling this.
///
/// # Example
///
/// ```
/// let v = vec!["a".to_string(), "b".to_string()];
/// for s in v.into_iter() {
/// // s has type String, not &String
/// println!("{}", s);
/// }
/// ```
#[inline]
#[unstable = "matches collection reform specification, waiting for dust to settle"]
pub fn into_iter(self) -> MoveItems<T> {
unsafe {
let ptr = self.ptr;
let cap = self.cap;
let begin = self.ptr as *const T;
let end = if mem::size_of::<T>() == 0 {
(ptr as uint + self.len()) as *const T
} else {
ptr.offset(self.len() as int) as *const T
};
mem::forget(self);
MoveItems { allocation: ptr, cap: cap, ptr: begin, end: end }
}
}
/// Sets the length of a vector.
///
/// This will explicitly set the size of the vector, without actually
/// modifying its buffers, so it is up to the caller to ensure that the
/// vector is actually the specified size.
///
/// # Example
///
/// ```
/// let mut v = vec![1u, 2, 3, 4];
/// unsafe {
/// v.set_len(1);
/// }
/// ```
#[inline]
#[stable]
pub unsafe fn set_len(&mut self, len: uint) {
self.len = len;
}
/// Removes an element from anywhere in the vector and return it, replacing
/// it with the last element. This does not preserve ordering, but is O(1).
///
/// Returns `None` if `index` is out of bounds.
///
/// # Example
/// ```
/// let mut v = vec!["foo", "bar", "baz", "qux"];
///
/// assert_eq!(v.swap_remove(1), Some("bar"));
/// assert_eq!(v, vec!["foo", "qux", "baz"]);
///
/// assert_eq!(v.swap_remove(0), Some("foo"));
/// assert_eq!(v, vec!["baz", "qux"]);
///
/// assert_eq!(v.swap_remove(2), None);
/// ```
#[inline]
#[unstable = "the naming of this function may be altered"]
pub fn swap_remove(&mut self, index: uint) -> Option<T> {
let length = self.len();
if length > 0 && index < length - 1 {
self.as_mut_slice().swap(index, length - 1);
} else if index >= length {
return None
}
self.pop()
}
/// Inserts an element at position `index` within the vector, shifting all
/// elements after position `i` one position to the right.
///
/// # Panics
///
/// Panics if `index` is not between `0` and the vector's length (both
/// bounds inclusive).
///
/// # Example
///
/// ```
/// let mut vec = vec![1i, 2, 3];
/// vec.insert(1, 4);
/// assert_eq!(vec, vec![1, 4, 2, 3]);
/// vec.insert(4, 5);
/// assert_eq!(vec, vec![1, 4, 2, 3, 5]);
/// ```
#[unstable = "panic semantics need settling"]
pub fn insert(&mut self, index: uint, element: T) {
let len = self.len();
assert!(index <= len);
// space for the new element
self.reserve(1);
unsafe { // infallible
// The spot to put the new value
{
let p = self.as_mut_ptr().offset(index as int);
// Shift everything over to make space. (Duplicating the
// `index`th element into two consecutive places.)
ptr::copy_memory(p.offset(1), &*p, len - index);
// Write it in, overwriting the first copy of the `index`th
// element.
ptr::write(&mut *p, element);
}
self.set_len(len + 1);
}
}
/// Removes and returns the element at position `index` within the vector,
/// shifting all elements after position `index` one position to the left.
/// Returns `None` if `i` is out of bounds.
///
/// # Example
///
/// ```
/// let mut v = vec![1i, 2, 3];
/// assert_eq!(v.remove(1), Some(2));
/// assert_eq!(v, vec![1, 3]);
///
/// assert_eq!(v.remove(4), None);
/// // v is unchanged:
/// assert_eq!(v, vec![1, 3]);
/// ```
#[unstable = "panic semantics need settling"]
pub fn remove(&mut self, index: uint) -> Option<T> {
let len = self.len();
if index < len {
unsafe { // infallible
let ret;
{
// the place we are taking from.
let ptr = self.as_mut_ptr().offset(index as int);
// copy it out, unsafely having a copy of the value on
// the stack and in the vector at the same time.
ret = Some(ptr::read(ptr as *const T));
// Shift everything down to fill in that spot.
ptr::copy_memory(ptr, &*ptr.offset(1), len - index - 1);
}
self.set_len(len - 1);
ret
}
} else {
None
}
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` such that `f(&e)` returns false.
/// This method operates in place and preserves the order of the retained elements.
///
/// # Example
///
/// ```
/// let mut vec = vec![1i, 2, 3, 4];
/// vec.retain(|&x| x%2 == 0);
/// assert_eq!(vec, vec![2, 4]);
/// ```
#[unstable = "the closure argument may become an unboxed closure"]
pub fn retain(&mut self, f: |&T| -> bool) {
let len = self.len();
let mut del = 0u;
{
let v = self.as_mut_slice();
for i in range(0u, len) {
if !f(&v[i]) {
del += 1;
} else if del > 0 {
v.swap(i-del, i);
}
}
}
if del > 0 {
self.truncate(len - del);
}
}
/// Expands a vector in place, initializing the new elements to the result of a function.
///
/// The vector is grown by `n` elements. The i-th new element are initialized to the value
/// returned by `f(i)` where `i` is in the range [0, n).
///
/// # Example
///
/// ```
/// let mut vec = vec![0u, 1];
/// vec.grow_fn(3, |i| i);
/// assert_eq!(vec, vec![0, 1, 0, 1, 2]);
/// ```
#[unstable = "this function may be renamed or change to unboxed closures"]
pub fn grow_fn(&mut self, n: uint, f: |uint| -> T) {
self.reserve(n);
for i in range(0u, n) {
self.push(f(i));
}
}
/// Appends an element to the back of a collection.
///
/// # Panics
///
/// Panics if the number of elements in the vector overflows a `uint`.
///
/// # Example
///
/// ```rust
/// let mut vec = vec!(1i, 2);
/// vec.push(3);
/// assert_eq!(vec, vec!(1, 2, 3));
/// ```
#[inline]
#[stable]
pub fn push(&mut self, value: T) {
if mem::size_of::<T>() == 0 {
// zero-size types consume no memory, so we can't rely on the address space running out
self.len = self.len.checked_add(1).expect("length overflow");
unsafe { mem::forget(value); }
return
}
if self.len == self.cap {
let old_size = self.cap * mem::size_of::<T>();
let size = max(old_size, 2 * mem::size_of::<T>()) * 2;
if old_size > size { panic!("capacity overflow") }
unsafe {
self.ptr = alloc_or_realloc(self.ptr, old_size, size);
if self.ptr.is_null() { ::alloc::oom() }
}
self.cap = max(self.cap, 2) * 2;
}
unsafe {
let end = (self.ptr as *const T).offset(self.len as int) as *mut T;
ptr::write(&mut *end, value);
self.len += 1;
}
}
/// Removes the last element from a vector and returns it, or `None` if
/// it is empty.
///
/// # Example
///