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Diffstat (limited to 'src/liballoc/vec.rs')
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diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs deleted file mode 100644 index f5a3d0cd4af..00000000000 --- a/src/liballoc/vec.rs +++ /dev/null @@ -1,3122 +0,0 @@ -// ignore-tidy-filelength -//! A contiguous growable array type with heap-allocated contents, written -//! `Vec<T>`. -//! -//! Vectors have `O(1)` indexing, amortized `O(1)` push (to the end) and -//! `O(1)` pop (from the end). -//! -//! Vectors ensure they never allocate more than `isize::MAX` bytes. -//! -//! # Examples -//! -//! You can explicitly create a [`Vec<T>`] with [`new`]: -//! -//! ``` -//! let v: Vec<i32> = Vec::new(); -//! ``` -//! -//! ...or by using the [`vec!`] macro: -//! -//! ``` -//! let v: Vec<i32> = vec![]; -//! -//! let v = vec![1, 2, 3, 4, 5]; -//! -//! let v = vec![0; 10]; // ten zeroes -//! ``` -//! -//! You can [`push`] values onto the end of a vector (which will grow the vector -//! as needed): -//! -//! ``` -//! let mut v = vec![1, 2]; -//! -//! v.push(3); -//! ``` -//! -//! Popping values works in much the same way: -//! -//! ``` -//! let mut v = vec![1, 2]; -//! -//! let two = v.pop(); -//! ``` -//! -//! Vectors also support indexing (through the [`Index`] and [`IndexMut`] traits): -//! -//! ``` -//! let mut v = vec![1, 2, 3]; -//! let three = v[2]; -//! v[1] = v[1] + 5; -//! ``` -//! -//! [`Vec<T>`]: ../../std/vec/struct.Vec.html -//! [`new`]: ../../std/vec/struct.Vec.html#method.new -//! [`push`]: ../../std/vec/struct.Vec.html#method.push -//! [`Index`]: ../../std/ops/trait.Index.html -//! [`IndexMut`]: ../../std/ops/trait.IndexMut.html -//! [`vec!`]: ../../std/macro.vec.html - -#![stable(feature = "rust1", since = "1.0.0")] - -use core::cmp::{self, Ordering}; -use core::fmt; -use core::hash::{Hash, Hasher}; -use core::intrinsics::{arith_offset, assume}; -use core::iter::{FromIterator, FusedIterator, TrustedLen}; -use core::marker::PhantomData; -use core::mem::{self, ManuallyDrop}; -use core::ops::Bound::{Excluded, Included, Unbounded}; -use core::ops::{self, Index, IndexMut, RangeBounds}; -use core::ptr::{self, NonNull}; -use core::slice::{self, SliceIndex}; - -use crate::borrow::{Cow, ToOwned}; -use crate::boxed::Box; -use crate::collections::TryReserveError; -use crate::raw_vec::RawVec; - -/// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'. -/// -/// # Examples -/// -/// ``` -/// let mut vec = Vec::new(); -/// vec.push(1); -/// vec.push(2); -/// -/// assert_eq!(vec.len(), 2); -/// assert_eq!(vec[0], 1); -/// -/// assert_eq!(vec.pop(), Some(2)); -/// assert_eq!(vec.len(), 1); -/// -/// vec[0] = 7; -/// assert_eq!(vec[0], 7); -/// -/// vec.extend([1, 2, 3].iter().copied()); -/// -/// for x in &vec { -/// println!("{}", x); -/// } -/// assert_eq!(vec, [7, 1, 2, 3]); -/// ``` -/// -/// The [`vec!`] macro is provided to make initialization more convenient: -/// -/// ``` -/// let mut vec = vec![1, 2, 3]; -/// vec.push(4); -/// assert_eq!(vec, [1, 2, 3, 4]); -/// ``` -/// -/// It can also initialize each element of a `Vec<T>` with a given value. -/// This may be more efficient than performing allocation and initialization -/// in separate steps, especially when initializing a vector of zeros: -/// -/// ``` -/// let vec = vec![0; 5]; -/// assert_eq!(vec, [0, 0, 0, 0, 0]); -/// -/// // The following is equivalent, but potentially slower: -/// let mut vec1 = Vec::with_capacity(5); -/// vec1.resize(5, 0); -/// ``` -/// -/// Use a `Vec<T>` as an efficient stack: -/// -/// ``` -/// let mut stack = Vec::new(); -/// -/// stack.push(1); -/// stack.push(2); -/// stack.push(3); -/// -/// while let Some(top) = stack.pop() { -/// // Prints 3, 2, 1 -/// println!("{}", top); -/// } -/// ``` -/// -/// # Indexing -/// -/// The `Vec` type allows to access values by index, because it implements the -/// [`Index`] trait. An example will be more explicit: -/// -/// ``` -/// let v = vec![0, 2, 4, 6]; -/// println!("{}", v[1]); // it will display '2' -/// ``` -/// -/// However be careful: if you try to access an index which isn't in the `Vec`, -/// your software will panic! You cannot do this: -/// -/// ```should_panic -/// let v = vec![0, 2, 4, 6]; -/// println!("{}", v[6]); // it will panic! -/// ``` -/// -/// Use [`get`] and [`get_mut`] if you want to check whether the index is in -/// the `Vec`. -/// -/// # Slicing -/// -/// A `Vec` can be mutable. Slices, on the other hand, are read-only objects. -/// To get a slice, use `&`. Example: -/// -/// ``` -/// fn read_slice(slice: &[usize]) { -/// // ... -/// } -/// -/// let v = vec![0, 1]; -/// read_slice(&v); -/// -/// // ... and that's all! -/// // you can also do it like this: -/// let x : &[usize] = &v; -/// ``` -/// -/// In Rust, it's more common to pass slices as arguments rather than vectors -/// when you just want to provide read access. The same goes for [`String`] and -/// [`&str`]. -/// -/// # 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. -/// -/// # Guarantees -/// -/// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees -/// about its design. This ensures that it's as low-overhead as possible in -/// the general case, and can be correctly manipulated in primitive ways -/// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`. -/// If additional type parameters are added (e.g., to support custom allocators), -/// overriding their defaults may change the behavior. -/// -/// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length) -/// triplet. No more, no less. The order of these fields is completely -/// unspecified, and you should use the appropriate methods to modify these. -/// The pointer will never be null, so this type is null-pointer-optimized. -/// -/// However, the pointer may not actually point to allocated memory. In particular, -/// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`], -/// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`] -/// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized -/// types inside a `Vec`, it will not allocate space for them. *Note that in this case -/// the `Vec` may not report a [`capacity`] of 0*. `Vec` will allocate if and only -/// if [`mem::size_of::<T>`]`() * capacity() > 0`. In general, `Vec`'s allocation -/// details are very subtle — if you intend to allocate memory using a `Vec` -/// and use it for something else (either to pass to unsafe code, or to build your -/// own memory-backed collection), be sure to deallocate this memory by using -/// `from_raw_parts` to recover the `Vec` and then dropping it. -/// -/// If a `Vec` *has* allocated memory, then the memory it points to is on the heap -/// (as defined by the allocator Rust is configured to use by default), and its -/// pointer points to [`len`] initialized, contiguous elements in order (what -/// you would see if you coerced it to a slice), followed by [`capacity`]` - -/// `[`len`] logically uninitialized, contiguous elements. -/// -/// `Vec` will never perform a "small optimization" where elements are actually -/// stored on the stack for two reasons: -/// -/// * It would make it more difficult for unsafe code to correctly manipulate -/// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were -/// only moved, and it would be more difficult to determine if a `Vec` had -/// actually allocated memory. -/// -/// * It would penalize the general case, incurring an additional branch -/// on every access. -/// -/// `Vec` will never automatically shrink itself, even if completely empty. This -/// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec` -/// and then filling it back up to the same [`len`] should incur no calls to -/// the allocator. If you wish to free up unused memory, use -/// [`shrink_to_fit`]. -/// -/// [`push`] and [`insert`] will never (re)allocate if the reported capacity is -/// sufficient. [`push`] and [`insert`] *will* (re)allocate if -/// [`len`]` == `[`capacity`]. That is, the reported capacity is completely -/// accurate, and can be relied on. It can even be used to manually free the memory -/// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even -/// when not necessary. -/// -/// `Vec` does not guarantee any particular growth strategy when reallocating -/// when full, nor when [`reserve`] is called. The current strategy is basic -/// and it may prove desirable to use a non-constant growth factor. Whatever -/// strategy is used will of course guarantee `O(1)` amortized [`push`]. -/// -/// `vec![x; n]`, `vec![a, b, c, d]`, and -/// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec` -/// with exactly the requested capacity. If [`len`]` == `[`capacity`], -/// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to -/// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements. -/// -/// `Vec` will not specifically overwrite any data that is removed from it, -/// but also won't specifically preserve it. Its uninitialized memory is -/// scratch space that it may use however it wants. It will generally just do -/// whatever is most efficient or otherwise easy to implement. Do not rely on -/// removed data to be erased for security purposes. Even if you drop a `Vec`, its -/// buffer may simply be reused by another `Vec`. Even if you zero a `Vec`'s memory -/// first, that may not actually happen because the optimizer does not consider -/// this a side-effect that must be preserved. There is one case which we will -/// not break, however: using `unsafe` code to write to the excess capacity, -/// and then increasing the length to match, is always valid. -/// -/// `Vec` does not currently guarantee the order in which elements are dropped. -/// The order has changed in the past and may change again. -/// -/// [`vec!`]: ../../std/macro.vec.html -/// [`get`]: ../../std/vec/struct.Vec.html#method.get -/// [`get_mut`]: ../../std/vec/struct.Vec.html#method.get_mut -/// [`Index`]: ../../std/ops/trait.Index.html -/// [`String`]: ../../std/string/struct.String.html -/// [`&str`]: ../../std/primitive.str.html -/// [`Vec::with_capacity`]: ../../std/vec/struct.Vec.html#method.with_capacity -/// [`Vec::new`]: ../../std/vec/struct.Vec.html#method.new -/// [`shrink_to_fit`]: ../../std/vec/struct.Vec.html#method.shrink_to_fit -/// [`capacity`]: ../../std/vec/struct.Vec.html#method.capacity -/// [`mem::size_of::<T>`]: ../../std/mem/fn.size_of.html -/// [`len`]: ../../std/vec/struct.Vec.html#method.len -/// [`push`]: ../../std/vec/struct.Vec.html#method.push -/// [`insert`]: ../../std/vec/struct.Vec.html#method.insert -/// [`reserve`]: ../../std/vec/struct.Vec.html#method.reserve -/// [owned slice]: ../../std/boxed/struct.Box.html -#[stable(feature = "rust1", since = "1.0.0")] -#[cfg_attr(not(test), rustc_diagnostic_item = "vec_type")] -pub struct Vec<T> { - buf: RawVec<T>, - len: usize, -} - -//////////////////////////////////////////////////////////////////////////////// -// Inherent methods -//////////////////////////////////////////////////////////////////////////////// - -impl<T> Vec<T> { - /// Constructs a new, empty `Vec<T>`. - /// - /// The vector will not allocate until elements are pushed onto it. - /// - /// # Examples - /// - /// ``` - /// # #![allow(unused_mut)] - /// let mut vec: Vec<i32> = Vec::new(); - /// ``` - #[inline] - #[rustc_const_stable(feature = "const_vec_new", since = "1.39.0")] - #[stable(feature = "rust1", since = "1.0.0")] - pub const fn new() -> Vec<T> { - Vec { buf: RawVec::NEW, len: 0 } - } - - /// Constructs a new, empty `Vec<T>` 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 although the returned vector has the - /// *capacity* specified, the vector will have a zero *length*. For an - /// explanation of the difference between length and capacity, see - /// *[Capacity and reallocation]*. - /// - /// [Capacity and reallocation]: #capacity-and-reallocation - /// - /// # Examples - /// - /// ``` - /// let mut vec = Vec::with_capacity(10); - /// - /// // The vector contains no items, even though it has capacity for more - /// assert_eq!(vec.len(), 0); - /// assert_eq!(vec.capacity(), 10); - /// - /// // These are all done without reallocating... - /// for i in 0..10 { - /// vec.push(i); - /// } - /// assert_eq!(vec.len(), 10); - /// assert_eq!(vec.capacity(), 10); - /// - /// // ...but this may make the vector reallocate - /// vec.push(11); - /// assert_eq!(vec.len(), 11); - /// assert!(vec.capacity() >= 11); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn with_capacity(capacity: usize) -> Vec<T> { - Vec { buf: RawVec::with_capacity(capacity), len: 0 } - } - - /// Decomposes a `Vec<T>` into its raw components. - /// - /// Returns the raw pointer to the underlying data, the length of - /// the vector (in elements), and the allocated capacity of the - /// data (in elements). These are the same arguments in the same - /// order as the arguments to [`from_raw_parts`]. - /// - /// After calling this function, the caller is responsible for the - /// memory previously managed by the `Vec`. The only way to do - /// this is to convert the raw pointer, length, and capacity back - /// into a `Vec` with the [`from_raw_parts`] function, allowing - /// the destructor to perform the cleanup. - /// - /// [`from_raw_parts`]: #method.from_raw_parts - /// - /// # Examples - /// - /// ``` - /// #![feature(vec_into_raw_parts)] - /// let v: Vec<i32> = vec![-1, 0, 1]; - /// - /// let (ptr, len, cap) = v.into_raw_parts(); - /// - /// let rebuilt = unsafe { - /// // We can now make changes to the components, such as - /// // transmuting the raw pointer to a compatible type. - /// let ptr = ptr as *mut u32; - /// - /// Vec::from_raw_parts(ptr, len, cap) - /// }; - /// assert_eq!(rebuilt, [4294967295, 0, 1]); - /// ``` - #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] - pub fn into_raw_parts(self) -> (*mut T, usize, usize) { - let mut me = ManuallyDrop::new(self); - (me.as_mut_ptr(), me.len(), me.capacity()) - } - - /// Creates a `Vec<T>` directly from the raw components of another vector. - /// - /// # Safety - /// - /// This is highly unsafe, due to the number of invariants that aren't - /// checked: - /// - /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>` - /// (at least, it's highly likely to be incorrect if it wasn't). - /// * `T` needs to have the same size and alignment as what `ptr` was allocated with. - /// (`T` having a less strict alignment is not sufficient, the alignment really - /// needs to be equal to satsify the [`dealloc`] requirement that memory must be - /// allocated and deallocated with the same layout.) - /// * `length` needs to be less than or equal to `capacity`. - /// * `capacity` needs to be the capacity that the pointer was allocated with. - /// - /// Violating these may cause problems like corrupting the allocator's - /// internal data structures. For example it is **not** safe - /// to build a `Vec<u8>` from a pointer to a C `char` array with length `size_t`. - /// It's also not safe to build one from a `Vec<u16>` and its length, because - /// the allocator cares about the alignment, and these two types have different - /// alignments. The buffer was allocated with alignment 2 (for `u16`), but after - /// turning it into a `Vec<u8>` it'll be deallocated with alignment 1. - /// - /// The ownership of `ptr` is effectively transferred to the - /// `Vec<T>` which may then deallocate, reallocate or change the - /// contents of memory pointed to by the pointer at will. Ensure - /// that nothing else uses the pointer after calling this - /// function. - /// - /// [`String`]: ../../std/string/struct.String.html - /// [`dealloc`]: ../../alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc - /// - /// # Examples - /// - /// ``` - /// use std::ptr; - /// use std::mem; - /// - /// let v = vec![1, 2, 3]; - /// - // FIXME Update this when vec_into_raw_parts is stabilized - /// // Prevent running `v`'s destructor so we are in complete control - /// // of the allocation. - /// let mut v = mem::ManuallyDrop::new(v); - /// - /// // 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 { - /// // Overwrite memory with 4, 5, 6 - /// for i in 0..len as isize { - /// 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, [4, 5, 6]); - /// } - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T> { - unsafe { Vec { buf: RawVec::from_raw_parts(ptr, capacity), len: length } } - } - - /// Returns the number of elements the vector can hold without - /// reallocating. - /// - /// # Examples - /// - /// ``` - /// let vec: Vec<i32> = Vec::with_capacity(10); - /// assert_eq!(vec.capacity(), 10); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn capacity(&self) -> usize { - self.buf.capacity() - } - - /// Reserves capacity for at least `additional` more elements to be inserted - /// in the given `Vec<T>`. The collection may reserve more space to avoid - /// frequent reallocations. After calling `reserve`, capacity will be - /// greater than or equal to `self.len() + additional`. Does nothing if - /// capacity is already sufficient. - /// - /// # Panics - /// - /// Panics if the new capacity exceeds `isize::MAX` bytes. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1]; - /// vec.reserve(10); - /// assert!(vec.capacity() >= 11); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn reserve(&mut self, additional: usize) { - self.buf.reserve(self.len, additional); - } - - /// Reserves the minimum capacity for exactly `additional` more elements to - /// be inserted in the given `Vec<T>`. After calling `reserve_exact`, - /// capacity will be greater than or equal to `self.len() + additional`. - /// 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 `usize`. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1]; - /// vec.reserve_exact(10); - /// assert!(vec.capacity() >= 11); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn reserve_exact(&mut self, additional: usize) { - self.buf.reserve_exact(self.len, additional); - } - - /// Tries to reserve capacity for at least `additional` more elements to be inserted - /// in the given `Vec<T>`. The collection may reserve more space to avoid - /// frequent reallocations. After calling `reserve`, capacity will be - /// greater than or equal to `self.len() + additional`. Does nothing if - /// capacity is already sufficient. - /// - /// # Errors - /// - /// If the capacity overflows, or the allocator reports a failure, then an error - /// is returned. - /// - /// # Examples - /// - /// ``` - /// #![feature(try_reserve)] - /// use std::collections::TryReserveError; - /// - /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { - /// let mut output = Vec::new(); - /// - /// // Pre-reserve the memory, exiting if we can't - /// output.try_reserve(data.len())?; - /// - /// // Now we know this can't OOM in the middle of our complex work - /// output.extend(data.iter().map(|&val| { - /// val * 2 + 5 // very complicated - /// })); - /// - /// Ok(output) - /// } - /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); - /// ``` - #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] - pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { - self.buf.try_reserve(self.len, additional) - } - - /// Tries to reserves the minimum capacity for exactly `additional` more elements to - /// be inserted in the given `Vec<T>`. After calling `reserve_exact`, - /// capacity will be greater than or equal to `self.len() + additional`. - /// 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. - /// - /// # Errors - /// - /// If the capacity overflows, or the allocator reports a failure, then an error - /// is returned. - /// - /// # Examples - /// - /// ``` - /// #![feature(try_reserve)] - /// use std::collections::TryReserveError; - /// - /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { - /// let mut output = Vec::new(); - /// - /// // Pre-reserve the memory, exiting if we can't - /// output.try_reserve(data.len())?; - /// - /// // Now we know this can't OOM in the middle of our complex work - /// output.extend(data.iter().map(|&val| { - /// val * 2 + 5 // very complicated - /// })); - /// - /// Ok(output) - /// } - /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); - /// ``` - #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] - pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { - self.buf.try_reserve_exact(self.len, additional) - } - - /// 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. - /// - /// # Examples - /// - /// ``` - /// let mut vec = Vec::with_capacity(10); - /// vec.extend([1, 2, 3].iter().cloned()); - /// assert_eq!(vec.capacity(), 10); - /// vec.shrink_to_fit(); - /// assert!(vec.capacity() >= 3); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn shrink_to_fit(&mut self) { - if self.capacity() != self.len { - self.buf.shrink_to_fit(self.len); - } - } - - /// Shrinks the capacity of the vector with a lower bound. - /// - /// The capacity will remain at least as large as both the length - /// and the supplied value. - /// - /// # Panics - /// - /// Panics if the current capacity is smaller than the supplied - /// minimum capacity. - /// - /// # Examples - /// - /// ``` - /// #![feature(shrink_to)] - /// let mut vec = Vec::with_capacity(10); - /// vec.extend([1, 2, 3].iter().cloned()); - /// assert_eq!(vec.capacity(), 10); - /// vec.shrink_to(4); - /// assert!(vec.capacity() >= 4); - /// vec.shrink_to(0); - /// assert!(vec.capacity() >= 3); - /// ``` - #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")] - pub fn shrink_to(&mut self, min_capacity: usize) { - self.buf.shrink_to_fit(cmp::max(self.len, min_capacity)); - } - - /// Converts the vector into [`Box<[T]>`][owned slice]. - /// - /// Note that this will drop any excess capacity. - /// - /// [owned slice]: ../../std/boxed/struct.Box.html - /// - /// # Examples - /// - /// ``` - /// let v = vec![1, 2, 3]; - /// - /// let slice = v.into_boxed_slice(); - /// ``` - /// - /// Any excess capacity is removed: - /// - /// ``` - /// let mut vec = Vec::with_capacity(10); - /// vec.extend([1, 2, 3].iter().cloned()); - /// - /// assert_eq!(vec.capacity(), 10); - /// let slice = vec.into_boxed_slice(); - /// assert_eq!(slice.into_vec().capacity(), 3); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn into_boxed_slice(mut self) -> Box<[T]> { - unsafe { - self.shrink_to_fit(); - let me = ManuallyDrop::new(self); - let buf = ptr::read(&me.buf); - let len = me.len(); - buf.into_box(len).assume_init() - } - } - - /// Shortens the vector, keeping the first `len` elements and dropping - /// the rest. - /// - /// If `len` is greater than the vector's current length, this has no - /// effect. - /// - /// The [`drain`] method can emulate `truncate`, but causes the excess - /// elements to be returned instead of dropped. - /// - /// Note that this method has no effect on the allocated capacity - /// of the vector. - /// - /// # Examples - /// - /// Truncating a five element vector to two elements: - /// - /// ``` - /// let mut vec = vec![1, 2, 3, 4, 5]; - /// vec.truncate(2); - /// assert_eq!(vec, [1, 2]); - /// ``` - /// - /// No truncation occurs when `len` is greater than the vector's current - /// length: - /// - /// ``` - /// let mut vec = vec![1, 2, 3]; - /// vec.truncate(8); - /// assert_eq!(vec, [1, 2, 3]); - /// ``` - /// - /// Truncating when `len == 0` is equivalent to calling the [`clear`] - /// method. - /// - /// ``` - /// let mut vec = vec![1, 2, 3]; - /// vec.truncate(0); - /// assert_eq!(vec, []); - /// ``` - /// - /// [`clear`]: #method.clear - /// [`drain`]: #method.drain - #[stable(feature = "rust1", since = "1.0.0")] - pub fn truncate(&mut self, len: usize) { - // This is safe because: - // - // * the slice passed to `drop_in_place` is valid; the `len > self.len` - // case avoids creating an invalid slice, and - // * the `len` of the vector is shrunk before calling `drop_in_place`, - // such that no value will be dropped twice in case `drop_in_place` - // were to panic once (if it panics twice, the program aborts). - unsafe { - if len > self.len { - return; - } - let remaining_len = self.len - len; - let s = ptr::slice_from_raw_parts_mut(self.as_mut_ptr().add(len), remaining_len); - self.len = len; - ptr::drop_in_place(s); - } - } - - /// Extracts a slice containing the entire vector. - /// - /// Equivalent to `&s[..]`. - /// - /// # Examples - /// - /// ``` - /// use std::io::{self, Write}; - /// let buffer = vec![1, 2, 3, 5, 8]; - /// io::sink().write(buffer.as_slice()).unwrap(); - /// ``` - #[inline] - #[stable(feature = "vec_as_slice", since = "1.7.0")] - pub fn as_slice(&self) -> &[T] { - self - } - - /// Extracts a mutable slice of the entire vector. - /// - /// Equivalent to `&mut s[..]`. - /// - /// # Examples - /// - /// ``` - /// use std::io::{self, Read}; - /// let mut buffer = vec![0; 3]; - /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap(); - /// ``` - #[inline] - #[stable(feature = "vec_as_slice", since = "1.7.0")] - pub fn as_mut_slice(&mut self) -> &mut [T] { - self - } - - /// Returns a raw pointer to the vector's buffer. - /// - /// The caller must ensure that the vector outlives the pointer this - /// function returns, or else it will end up pointing to garbage. - /// Modifying the vector may cause its buffer to be reallocated, - /// which would also make any pointers to it invalid. - /// - /// The caller must also ensure that the memory the pointer (non-transitively) points to - /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer - /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`]. - /// - /// # Examples - /// - /// ``` - /// let x = vec![1, 2, 4]; - /// let x_ptr = x.as_ptr(); - /// - /// unsafe { - /// for i in 0..x.len() { - /// assert_eq!(*x_ptr.add(i), 1 << i); - /// } - /// } - /// ``` - /// - /// [`as_mut_ptr`]: #method.as_mut_ptr - #[stable(feature = "vec_as_ptr", since = "1.37.0")] - #[inline] - pub fn as_ptr(&self) -> *const T { - // We shadow the slice method of the same name to avoid going through - // `deref`, which creates an intermediate reference. - let ptr = self.buf.ptr(); - unsafe { - assume(!ptr.is_null()); - } - ptr - } - - /// Returns an unsafe mutable pointer to the vector's buffer. - /// - /// The caller must ensure that the vector outlives the pointer this - /// function returns, or else it will end up pointing to garbage. - /// Modifying the vector may cause its buffer to be reallocated, - /// which would also make any pointers to it invalid. - /// - /// # Examples - /// - /// ``` - /// // Allocate vector big enough for 4 elements. - /// let size = 4; - /// let mut x: Vec<i32> = Vec::with_capacity(size); - /// let x_ptr = x.as_mut_ptr(); - /// - /// // Initialize elements via raw pointer writes, then set length. - /// unsafe { - /// for i in 0..size { - /// *x_ptr.add(i) = i as i32; - /// } - /// x.set_len(size); - /// } - /// assert_eq!(&*x, &[0,1,2,3]); - /// ``` - #[stable(feature = "vec_as_ptr", since = "1.37.0")] - #[inline] - pub fn as_mut_ptr(&mut self) -> *mut T { - // We shadow the slice method of the same name to avoid going through - // `deref_mut`, which creates an intermediate reference. - let ptr = self.buf.ptr(); - unsafe { - assume(!ptr.is_null()); - } - ptr - } - - /// Forces the length of the vector to `new_len`. - /// - /// This is a low-level operation that maintains none of the normal - /// invariants of the type. Normally changing the length of a vector - /// is done using one of the safe operations instead, such as - /// [`truncate`], [`resize`], [`extend`], or [`clear`]. - /// - /// [`truncate`]: #method.truncate - /// [`resize`]: #method.resize - /// [`extend`]: ../../std/iter/trait.Extend.html#tymethod.extend - /// [`clear`]: #method.clear - /// - /// # Safety - /// - /// - `new_len` must be less than or equal to [`capacity()`]. - /// - The elements at `old_len..new_len` must be initialized. - /// - /// [`capacity()`]: #method.capacity - /// - /// # Examples - /// - /// This method can be useful for situations in which the vector - /// is serving as a buffer for other code, particularly over FFI: - /// - /// ```no_run - /// # #![allow(dead_code)] - /// # // This is just a minimal skeleton for the doc example; - /// # // don't use this as a starting point for a real library. - /// # pub struct StreamWrapper { strm: *mut std::ffi::c_void } - /// # const Z_OK: i32 = 0; - /// # extern "C" { - /// # fn deflateGetDictionary( - /// # strm: *mut std::ffi::c_void, - /// # dictionary: *mut u8, - /// # dictLength: *mut usize, - /// # ) -> i32; - /// # } - /// # impl StreamWrapper { - /// pub fn get_dictionary(&self) -> Option<Vec<u8>> { - /// // Per the FFI method's docs, "32768 bytes is always enough". - /// let mut dict = Vec::with_capacity(32_768); - /// let mut dict_length = 0; - /// // SAFETY: When `deflateGetDictionary` returns `Z_OK`, it holds that: - /// // 1. `dict_length` elements were initialized. - /// // 2. `dict_length` <= the capacity (32_768) - /// // which makes `set_len` safe to call. - /// unsafe { - /// // Make the FFI call... - /// let r = deflateGetDictionary(self.strm, dict.as_mut_ptr(), &mut dict_length); - /// if r == Z_OK { - /// // ...and update the length to what was initialized. - /// dict.set_len(dict_length); - /// Some(dict) - /// } else { - /// None - /// } - /// } - /// } - /// # } - /// ``` - /// - /// While the following example is sound, there is a memory leak since - /// the inner vectors were not freed prior to the `set_len` call: - /// - /// ``` - /// let mut vec = vec![vec![1, 0, 0], - /// vec![0, 1, 0], - /// vec![0, 0, 1]]; - /// // SAFETY: - /// // 1. `old_len..0` is empty so no elements need to be initialized. - /// // 2. `0 <= capacity` always holds whatever `capacity` is. - /// unsafe { - /// vec.set_len(0); - /// } - /// ``` - /// - /// Normally, here, one would use [`clear`] instead to correctly drop - /// the contents and thus not leak memory. - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub unsafe fn set_len(&mut self, new_len: usize) { - debug_assert!(new_len <= self.capacity()); - - self.len = new_len; - } - - /// Removes an element from the vector and returns it. - /// - /// The removed element is replaced by the last element of the vector. - /// - /// This does not preserve ordering, but is O(1). - /// - /// # Panics - /// - /// Panics if `index` is out of bounds. - /// - /// # Examples - /// - /// ``` - /// let mut v = vec!["foo", "bar", "baz", "qux"]; - /// - /// assert_eq!(v.swap_remove(1), "bar"); - /// assert_eq!(v, ["foo", "qux", "baz"]); - /// - /// assert_eq!(v.swap_remove(0), "foo"); - /// assert_eq!(v, ["baz", "qux"]); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn swap_remove(&mut self, index: usize) -> T { - #[cold] - #[inline(never)] - fn assert_failed(index: usize, len: usize) -> ! { - panic!("swap_remove index (is {}) should be < len (is {})", index, len); - } - - let len = self.len(); - if index >= len { - assert_failed(index, len); - } - unsafe { - // We replace self[index] with the last element. Note that if the - // bounds check above succeeds there must be a last element (which - // can be self[index] itself). - let last = ptr::read(self.as_ptr().add(len - 1)); - let hole = self.as_mut_ptr().add(index); - self.set_len(len - 1); - ptr::replace(hole, last) - } - } - - /// Inserts an element at position `index` within the vector, shifting all - /// elements after it to the right. - /// - /// # Panics - /// - /// Panics if `index > len`. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1, 2, 3]; - /// vec.insert(1, 4); - /// assert_eq!(vec, [1, 4, 2, 3]); - /// vec.insert(4, 5); - /// assert_eq!(vec, [1, 4, 2, 3, 5]); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn insert(&mut self, index: usize, element: T) { - #[cold] - #[inline(never)] - fn assert_failed(index: usize, len: usize) -> ! { - panic!("insertion index (is {}) should be <= len (is {})", index, len); - } - - let len = self.len(); - if index > len { - assert_failed(index, len); - } - - // space for the new element - if len == self.buf.capacity() { - self.reserve(1); - } - - unsafe { - // infallible - // The spot to put the new value - { - let p = self.as_mut_ptr().add(index); - // Shift everything over to make space. (Duplicating the - // `index`th element into two consecutive places.) - ptr::copy(p, p.offset(1), len - index); - // Write it in, overwriting the first copy of the `index`th - // element. - ptr::write(p, element); - } - self.set_len(len + 1); - } - } - - /// Removes and returns the element at position `index` within the vector, - /// shifting all elements after it to the left. - /// - /// # Panics - /// - /// Panics if `index` is out of bounds. - /// - /// # Examples - /// - /// ``` - /// let mut v = vec![1, 2, 3]; - /// assert_eq!(v.remove(1), 2); - /// assert_eq!(v, [1, 3]); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn remove(&mut self, index: usize) -> T { - #[cold] - #[inline(never)] - fn assert_failed(index: usize, len: usize) -> ! { - panic!("removal index (is {}) should be < len (is {})", index, len); - } - - let len = self.len(); - if index >= len { - assert_failed(index, len); - } - unsafe { - // infallible - let ret; - { - // the place we are taking from. - let ptr = self.as_mut_ptr().add(index); - // copy it out, unsafely having a copy of the value on - // the stack and in the vector at the same time. - ret = ptr::read(ptr); - - // Shift everything down to fill in that spot. - ptr::copy(ptr.offset(1), ptr, len - index - 1); - } - self.set_len(len - 1); - ret - } - } - - /// 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, visiting each element exactly once in the - /// original order, and preserves the order of the retained elements. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1, 2, 3, 4]; - /// vec.retain(|&x| x % 2 == 0); - /// assert_eq!(vec, [2, 4]); - /// ``` - /// - /// The exact order may be useful for tracking external state, like an index. - /// - /// ``` - /// let mut vec = vec![1, 2, 3, 4, 5]; - /// let keep = [false, true, true, false, true]; - /// let mut i = 0; - /// vec.retain(|_| (keep[i], i += 1).0); - /// assert_eq!(vec, [2, 3, 5]); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn retain<F>(&mut self, mut f: F) - where - F: FnMut(&T) -> bool, - { - let len = self.len(); - let mut del = 0; - { - let v = &mut **self; - - for i in 0..len { - if !f(&v[i]) { - del += 1; - } else if del > 0 { - v.swap(i - del, i); - } - } - } - if del > 0 { - self.truncate(len - del); - } - } - - /// Removes all but the first of consecutive elements in the vector that resolve to the same - /// key. - /// - /// If the vector is sorted, this removes all duplicates. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![10, 20, 21, 30, 20]; - /// - /// vec.dedup_by_key(|i| *i / 10); - /// - /// assert_eq!(vec, [10, 20, 30, 20]); - /// ``` - #[stable(feature = "dedup_by", since = "1.16.0")] - #[inline] - pub fn dedup_by_key<F, K>(&mut self, mut key: F) - where - F: FnMut(&mut T) -> K, - K: PartialEq, - { - self.dedup_by(|a, b| key(a) == key(b)) - } - - /// Removes all but the first of consecutive elements in the vector satisfying a given equality - /// relation. - /// - /// The `same_bucket` function is passed references to two elements from the vector and - /// must determine if the elements compare equal. The elements are passed in opposite order - /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is removed. - /// - /// If the vector is sorted, this removes all duplicates. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"]; - /// - /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b)); - /// - /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]); - /// ``` - #[stable(feature = "dedup_by", since = "1.16.0")] - pub fn dedup_by<F>(&mut self, same_bucket: F) - where - F: FnMut(&mut T, &mut T) -> bool, - { - let len = { - let (dedup, _) = self.as_mut_slice().partition_dedup_by(same_bucket); - dedup.len() - }; - self.truncate(len); - } - - /// Appends an element to the back of a collection. - /// - /// # Panics - /// - /// Panics if the new capacity exceeds `isize::MAX` bytes. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1, 2]; - /// vec.push(3); - /// assert_eq!(vec, [1, 2, 3]); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn push(&mut self, value: T) { - // This will panic or abort if we would allocate > isize::MAX bytes - // or if the length increment would overflow for zero-sized types. - if self.len == self.buf.capacity() { - self.reserve(1); - } - unsafe { - let end = self.as_mut_ptr().add(self.len); - ptr::write(end, value); - self.len += 1; - } - } - - /// Removes the last element from a vector and returns it, or [`None`] if it - /// is empty. - /// - /// [`None`]: ../../std/option/enum.Option.html#variant.None - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1, 2, 3]; - /// assert_eq!(vec.pop(), Some(3)); - /// assert_eq!(vec, [1, 2]); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn pop(&mut self) -> Option<T> { - if self.len == 0 { - None - } else { - unsafe { - self.len -= 1; - Some(ptr::read(self.as_ptr().add(self.len()))) - } - } - } - - /// Moves all the elements of `other` into `Self`, leaving `other` empty. - /// - /// # Panics - /// - /// Panics if the number of elements in the vector overflows a `usize`. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1, 2, 3]; - /// let mut vec2 = vec![4, 5, 6]; - /// vec.append(&mut vec2); - /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]); - /// assert_eq!(vec2, []); - /// ``` - #[inline] - #[stable(feature = "append", since = "1.4.0")] - pub fn append(&mut self, other: &mut Self) { - unsafe { - self.append_elements(other.as_slice() as _); - other.set_len(0); - } - } - - /// Appends elements to `Self` from other buffer. - #[inline] - unsafe fn append_elements(&mut self, other: *const [T]) { - let count = unsafe { (*other).len() }; - self.reserve(count); - let len = self.len(); - unsafe { ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count) }; - self.len += count; - } - - /// Creates a draining iterator that removes the specified range in the vector - /// and yields the removed items. - /// - /// When the iterator **is** dropped, all elements in the range are removed - /// from the vector, even if the iterator was not fully consumed. If the - /// iterator **is not** dropped (with [`mem::forget`] for example), it is - /// unspecified how many elements are removed. - /// - /// # Panics - /// - /// Panics if the starting point is greater than the end point or if - /// the end point is greater than the length of the vector. - /// - /// # Examples - /// - /// ``` - /// let mut v = vec![1, 2, 3]; - /// let u: Vec<_> = v.drain(1..).collect(); - /// assert_eq!(v, &[1]); - /// assert_eq!(u, &[2, 3]); - /// - /// // A full range clears the vector - /// v.drain(..); - /// assert_eq!(v, &[]); - /// ``` - #[stable(feature = "drain", since = "1.6.0")] - pub fn drain<R>(&mut self, range: R) -> Drain<'_, T> - where - R: RangeBounds<usize>, - { - // Memory safety - // - // When the Drain is first created, it shortens the length of - // the source vector to make sure no uninitialized or moved-from elements - // are accessible at all if the Drain's destructor never gets to run. - // - // Drain will ptr::read out the values to remove. - // When finished, remaining tail of the vec is copied back to cover - // the hole, and the vector length is restored to the new length. - // - let len = self.len(); - let start = match range.start_bound() { - Included(&n) => n, - Excluded(&n) => n + 1, - Unbounded => 0, - }; - let end = match range.end_bound() { - Included(&n) => n + 1, - Excluded(&n) => n, - Unbounded => len, - }; - - #[cold] - #[inline(never)] - fn start_assert_failed(start: usize, end: usize) -> ! { - panic!("start drain index (is {}) should be <= end drain index (is {})", start, end); - } - - #[cold] - #[inline(never)] - fn end_assert_failed(end: usize, len: usize) -> ! { - panic!("end drain index (is {}) should be <= len (is {})", end, len); - } - - if start > end { - start_assert_failed(start, end); - } - if end > len { - end_assert_failed(end, len); - } - - unsafe { - // set self.vec length's to start, to be safe in case Drain is leaked - self.set_len(start); - // Use the borrow in the IterMut to indicate borrowing behavior of the - // whole Drain iterator (like &mut T). - let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(start), end - start); - Drain { - tail_start: end, - tail_len: len - end, - iter: range_slice.iter(), - vec: NonNull::from(self), - } - } - } - - /// Clears the vector, removing all values. - /// - /// Note that this method has no effect on the allocated capacity - /// of the vector. - /// - /// # Examples - /// - /// ``` - /// let mut v = vec![1, 2, 3]; - /// - /// v.clear(); - /// - /// assert!(v.is_empty()); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn clear(&mut self) { - self.truncate(0) - } - - /// Returns the number of elements in the vector, also referred to - /// as its 'length'. - /// - /// # Examples - /// - /// ``` - /// let a = vec![1, 2, 3]; - /// assert_eq!(a.len(), 3); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn len(&self) -> usize { - self.len - } - - /// Returns `true` if the vector contains no elements. - /// - /// # Examples - /// - /// ``` - /// let mut v = Vec::new(); - /// assert!(v.is_empty()); - /// - /// v.push(1); - /// assert!(!v.is_empty()); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn is_empty(&self) -> bool { - self.len() == 0 - } - - /// Splits the collection into two at the given index. - /// - /// Returns a newly allocated vector containing the elements in the range - /// `[at, len)`. After the call, the original vector will be left containing - /// the elements `[0, at)` with its previous capacity unchanged. - /// - /// # Panics - /// - /// Panics if `at > len`. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1,2,3]; - /// let vec2 = vec.split_off(1); - /// assert_eq!(vec, [1]); - /// assert_eq!(vec2, [2, 3]); - /// ``` - #[inline] - #[must_use = "use `.truncate()` if you don't need the other half"] - #[stable(feature = "split_off", since = "1.4.0")] - pub fn split_off(&mut self, at: usize) -> Self { - #[cold] - #[inline(never)] - fn assert_failed(at: usize, len: usize) -> ! { - panic!("`at` split index (is {}) should be <= len (is {})", at, len); - } - - if at > self.len() { - assert_failed(at, self.len()); - } - - let other_len = self.len - at; - let mut other = Vec::with_capacity(other_len); - - // Unsafely `set_len` and copy items to `other`. - unsafe { - self.set_len(at); - other.set_len(other_len); - - ptr::copy_nonoverlapping(self.as_ptr().add(at), other.as_mut_ptr(), other.len()); - } - other - } - - /// Resizes the `Vec` in-place so that `len` is equal to `new_len`. - /// - /// If `new_len` is greater than `len`, the `Vec` is extended by the - /// difference, with each additional slot filled with the result of - /// calling the closure `f`. The return values from `f` will end up - /// in the `Vec` in the order they have been generated. - /// - /// If `new_len` is less than `len`, the `Vec` is simply truncated. - /// - /// This method uses a closure to create new values on every push. If - /// you'd rather [`Clone`] a given value, use [`resize`]. If you want - /// to use the [`Default`] trait to generate values, you can pass - /// [`Default::default()`] as the second argument. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1, 2, 3]; - /// vec.resize_with(5, Default::default); - /// assert_eq!(vec, [1, 2, 3, 0, 0]); - /// - /// let mut vec = vec![]; - /// let mut p = 1; - /// vec.resize_with(4, || { p *= 2; p }); - /// assert_eq!(vec, [2, 4, 8, 16]); - /// ``` - /// - /// [`resize`]: #method.resize - /// [`Clone`]: ../../std/clone/trait.Clone.html - #[stable(feature = "vec_resize_with", since = "1.33.0")] - pub fn resize_with<F>(&mut self, new_len: usize, f: F) - where - F: FnMut() -> T, - { - let len = self.len(); - if new_len > len { - self.extend_with(new_len - len, ExtendFunc(f)); - } else { - self.truncate(new_len); - } - } - - /// Consumes and leaks the `Vec`, returning a mutable reference to the contents, - /// `&'a mut [T]`. Note that the type `T` must outlive the chosen lifetime - /// `'a`. If the type has only static references, or none at all, then this - /// may be chosen to be `'static`. - /// - /// This function is similar to the `leak` function on `Box`. - /// - /// This function is mainly useful for data that lives for the remainder of - /// the program's life. Dropping the returned reference will cause a memory - /// leak. - /// - /// # Examples - /// - /// Simple usage: - /// - /// ``` - /// #![feature(vec_leak)] - /// - /// let x = vec![1, 2, 3]; - /// let static_ref: &'static mut [usize] = Vec::leak(x); - /// static_ref[0] += 1; - /// assert_eq!(static_ref, &[2, 2, 3]); - /// ``` - #[unstable(feature = "vec_leak", issue = "62195")] - #[inline] - pub fn leak<'a>(vec: Vec<T>) -> &'a mut [T] - where - T: 'a, // Technically not needed, but kept to be explicit. - { - Box::leak(vec.into_boxed_slice()) - } -} - -impl<T: Clone> Vec<T> { - /// Resizes the `Vec` in-place so that `len` is equal to `new_len`. - /// - /// If `new_len` is greater than `len`, the `Vec` is extended by the - /// difference, with each additional slot filled with `value`. - /// If `new_len` is less than `len`, the `Vec` is simply truncated. - /// - /// This method requires `T` to implement [`Clone`], - /// in order to be able to clone the passed value. - /// If you need more flexibility (or want to rely on [`Default`] instead of - /// [`Clone`]), use [`resize_with`]. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec!["hello"]; - /// vec.resize(3, "world"); - /// assert_eq!(vec, ["hello", "world", "world"]); - /// - /// let mut vec = vec![1, 2, 3, 4]; - /// vec.resize(2, 0); - /// assert_eq!(vec, [1, 2]); - /// ``` - /// - /// [`Clone`]: ../../std/clone/trait.Clone.html - /// [`Default`]: ../../std/default/trait.Default.html - /// [`resize_with`]: #method.resize_with - #[stable(feature = "vec_resize", since = "1.5.0")] - pub fn resize(&mut self, new_len: usize, value: T) { - let len = self.len(); - - if new_len > len { - self.extend_with(new_len - len, ExtendElement(value)) - } else { - self.truncate(new_len); - } - } - - /// Clones and 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. - /// - /// Note that this function is same as [`extend`] except that it is - /// specialized to work with slices instead. If and when Rust gets - /// specialization this function will likely be deprecated (but still - /// available). - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1]; - /// vec.extend_from_slice(&[2, 3, 4]); - /// assert_eq!(vec, [1, 2, 3, 4]); - /// ``` - /// - /// [`extend`]: #method.extend - #[stable(feature = "vec_extend_from_slice", since = "1.6.0")] - pub fn extend_from_slice(&mut self, other: &[T]) { - self.spec_extend(other.iter()) - } -} - -impl<T: Default> Vec<T> { - /// Resizes the `Vec` in-place so that `len` is equal to `new_len`. - /// - /// If `new_len` is greater than `len`, the `Vec` is extended by the - /// difference, with each additional slot filled with [`Default::default()`]. - /// If `new_len` is less than `len`, the `Vec` is simply truncated. - /// - /// This method uses [`Default`] to create new values on every push. If - /// you'd rather [`Clone`] a given value, use [`resize`]. - /// - /// # Examples - /// - /// ``` - /// # #![allow(deprecated)] - /// #![feature(vec_resize_default)] - /// - /// let mut vec = vec![1, 2, 3]; - /// vec.resize_default(5); - /// assert_eq!(vec, [1, 2, 3, 0, 0]); - /// - /// let mut vec = vec![1, 2, 3, 4]; - /// vec.resize_default(2); - /// assert_eq!(vec, [1, 2]); - /// ``` - /// - /// [`resize`]: #method.resize - /// [`Default::default()`]: ../../std/default/trait.Default.html#tymethod.default - /// [`Default`]: ../../std/default/trait.Default.html - /// [`Clone`]: ../../std/clone/trait.Clone.html - #[unstable(feature = "vec_resize_default", issue = "41758")] - #[rustc_deprecated( - reason = "This is moving towards being removed in favor \ - of `.resize_with(Default::default)`. If you disagree, please comment \ - in the tracking issue.", - since = "1.33.0" - )] - pub fn resize_default(&mut self, new_len: usize) { - let len = self.len(); - - if new_len > len { - self.extend_with(new_len - len, ExtendDefault); - } else { - self.truncate(new_len); - } - } -} - -// This code generalizes `extend_with_{element,default}`. -trait ExtendWith<T> { - fn next(&mut self) -> T; - fn last(self) -> T; -} - -struct ExtendElement<T>(T); -impl<T: Clone> ExtendWith<T> for ExtendElement<T> { - fn next(&mut self) -> T { - self.0.clone() - } - fn last(self) -> T { - self.0 - } -} - -struct ExtendDefault; -impl<T: Default> ExtendWith<T> for ExtendDefault { - fn next(&mut self) -> T { - Default::default() - } - fn last(self) -> T { - Default::default() - } -} - -struct ExtendFunc<F>(F); -impl<T, F: FnMut() -> T> ExtendWith<T> for ExtendFunc<F> { - fn next(&mut self) -> T { - (self.0)() - } - fn last(mut self) -> T { - (self.0)() - } -} - -impl<T> Vec<T> { - /// Extend the vector by `n` values, using the given generator. - fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) { - self.reserve(n); - - unsafe { - let mut ptr = self.as_mut_ptr().add(self.len()); - // Use SetLenOnDrop to work around bug where compiler - // may not realize the store through `ptr` through self.set_len() - // don't alias. - let mut local_len = SetLenOnDrop::new(&mut self.len); - - // Write all elements except the last one - for _ in 1..n { - ptr::write(ptr, value.next()); - ptr = ptr.offset(1); - // Increment the length in every step in case next() panics - local_len.increment_len(1); - } - - if n > 0 { - // We can write the last element directly without cloning needlessly - ptr::write(ptr, value.last()); - local_len.increment_len(1); - } - - // len set by scope guard - } - } -} - -// Set the length of the vec when the `SetLenOnDrop` value goes out of scope. -// -// The idea is: The length field in SetLenOnDrop is a local variable -// that the optimizer will see does not alias with any stores through the Vec's data -// pointer. This is a workaround for alias analysis issue #32155 -struct SetLenOnDrop<'a> { - len: &'a mut usize, - local_len: usize, -} - -impl<'a> SetLenOnDrop<'a> { - #[inline] - fn new(len: &'a mut usize) -> Self { - SetLenOnDrop { local_len: *len, len } - } - - #[inline] - fn increment_len(&mut self, increment: usize) { - self.local_len += increment; - } -} - -impl Drop for SetLenOnDrop<'_> { - #[inline] - fn drop(&mut self) { - *self.len = self.local_len; - } -} - -impl<T: PartialEq> Vec<T> { - /// Removes consecutive repeated elements in the vector according to the - /// [`PartialEq`] trait implementation. - /// - /// If the vector is sorted, this removes all duplicates. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec![1, 2, 2, 3, 2]; - /// - /// vec.dedup(); - /// - /// assert_eq!(vec, [1, 2, 3, 2]); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - #[inline] - pub fn dedup(&mut self) { - self.dedup_by(|a, b| a == b) - } -} - -impl<T> Vec<T> { - /// Removes the first instance of `item` from the vector if the item exists. - /// - /// This method will be removed soon. - #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")] - #[rustc_deprecated( - reason = "Removing the first item equal to a needle is already easily possible \ - with iterators and the current Vec methods. Furthermore, having a method for \ - one particular case of removal (linear search, only the first item, no swap remove) \ - but not for others is inconsistent. This method will be removed soon.", - since = "1.46.0" - )] - pub fn remove_item<V>(&mut self, item: &V) -> Option<T> - where - T: PartialEq<V>, - { - let pos = self.iter().position(|x| *x == *item)?; - Some(self.remove(pos)) - } -} - -//////////////////////////////////////////////////////////////////////////////// -// Internal methods and functions -//////////////////////////////////////////////////////////////////////////////// - -#[doc(hidden)] -#[stable(feature = "rust1", since = "1.0.0")] -pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> { - <T as SpecFromElem>::from_elem(elem, n) -} - -// Specialization trait used for Vec::from_elem -trait SpecFromElem: Sized { - fn from_elem(elem: Self, n: usize) -> Vec<Self>; -} - -impl<T: Clone> SpecFromElem for T { - default fn from_elem(elem: Self, n: usize) -> Vec<Self> { - let mut v = Vec::with_capacity(n); - v.extend_with(n, ExtendElement(elem)); - v - } -} - -impl SpecFromElem for i8 { - #[inline] - fn from_elem(elem: i8, n: usize) -> Vec<i8> { - if elem == 0 { - return Vec { buf: RawVec::with_capacity_zeroed(n), len: n }; - } - unsafe { - let mut v = Vec::with_capacity(n); - ptr::write_bytes(v.as_mut_ptr(), elem as u8, n); - v.set_len(n); - v - } - } -} - -impl SpecFromElem for u8 { - #[inline] - fn from_elem(elem: u8, n: usize) -> Vec<u8> { - if elem == 0 { - return Vec { buf: RawVec::with_capacity_zeroed(n), len: n }; - } - unsafe { - let mut v = Vec::with_capacity(n); - ptr::write_bytes(v.as_mut_ptr(), elem, n); - v.set_len(n); - v - } - } -} - -impl<T: Clone + IsZero> SpecFromElem for T { - #[inline] - fn from_elem(elem: T, n: usize) -> Vec<T> { - if elem.is_zero() { - return Vec { buf: RawVec::with_capacity_zeroed(n), len: n }; - } - let mut v = Vec::with_capacity(n); - v.extend_with(n, ExtendElement(elem)); - v - } -} - -#[rustc_specialization_trait] -unsafe trait IsZero { - /// Whether this value is zero - fn is_zero(&self) -> bool; -} - -macro_rules! impl_is_zero { - ($t:ty, $is_zero:expr) => { - unsafe impl IsZero for $t { - #[inline] - fn is_zero(&self) -> bool { - $is_zero(*self) - } - } - }; -} - -impl_is_zero!(i16, |x| x == 0); -impl_is_zero!(i32, |x| x == 0); -impl_is_zero!(i64, |x| x == 0); -impl_is_zero!(i128, |x| x == 0); -impl_is_zero!(isize, |x| x == 0); - -impl_is_zero!(u16, |x| x == 0); -impl_is_zero!(u32, |x| x == 0); -impl_is_zero!(u64, |x| x == 0); -impl_is_zero!(u128, |x| x == 0); -impl_is_zero!(usize, |x| x == 0); - -impl_is_zero!(bool, |x| x == false); -impl_is_zero!(char, |x| x == '\0'); - -impl_is_zero!(f32, |x: f32| x.to_bits() == 0); -impl_is_zero!(f64, |x: f64| x.to_bits() == 0); - -unsafe impl<T> IsZero for *const T { - #[inline] - fn is_zero(&self) -> bool { - (*self).is_null() - } -} - -unsafe impl<T> IsZero for *mut T { - #[inline] - fn is_zero(&self) -> bool { - (*self).is_null() - } -} - -// `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null. -// For fat pointers, the bytes that would be the pointer metadata in the `Some` -// variant are padding in the `None` variant, so ignoring them and -// zero-initializing instead is ok. -// `Option<&mut T>` never implements `Clone`, so there's no need for an impl of -// `SpecFromElem`. - -unsafe impl<T: ?Sized> IsZero for Option<&T> { - #[inline] - fn is_zero(&self) -> bool { - self.is_none() - } -} - -unsafe impl<T: ?Sized> IsZero for Option<Box<T>> { - #[inline] - fn is_zero(&self) -> bool { - self.is_none() - } -} - -//////////////////////////////////////////////////////////////////////////////// -// Common trait implementations for Vec -//////////////////////////////////////////////////////////////////////////////// - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> ops::Deref for Vec<T> { - type Target = [T]; - - fn deref(&self) -> &[T] { - unsafe { slice::from_raw_parts(self.as_ptr(), self.len) } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> ops::DerefMut for Vec<T> { - fn deref_mut(&mut self) -> &mut [T] { - unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: Clone> Clone for Vec<T> { - #[cfg(not(test))] - fn clone(&self) -> Vec<T> { - <[T]>::to_vec(&**self) - } - - // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is - // required for this method definition, is not available. Instead use the - // `slice::to_vec` function which is only available with cfg(test) - // NB see the slice::hack module in slice.rs for more information - #[cfg(test)] - fn clone(&self) -> Vec<T> { - crate::slice::to_vec(&**self) - } - - fn clone_from(&mut self, other: &Vec<T>) { - other.as_slice().clone_into(self); - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: Hash> Hash for Vec<T> { - #[inline] - fn hash<H: Hasher>(&self, state: &mut H) { - Hash::hash(&**self, state) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -#[rustc_on_unimplemented( - message = "vector indices are of type `usize` or ranges of `usize`", - label = "vector indices are of type `usize` or ranges of `usize`" -)] -impl<T, I: SliceIndex<[T]>> Index<I> for Vec<T> { - type Output = I::Output; - - #[inline] - fn index(&self, index: I) -> &Self::Output { - Index::index(&**self, index) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -#[rustc_on_unimplemented( - message = "vector indices are of type `usize` or ranges of `usize`", - label = "vector indices are of type `usize` or ranges of `usize`" -)] -impl<T, I: SliceIndex<[T]>> IndexMut<I> for Vec<T> { - #[inline] - fn index_mut(&mut self, index: I) -> &mut Self::Output { - IndexMut::index_mut(&mut **self, index) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> FromIterator<T> for Vec<T> { - #[inline] - fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> { - <Self as SpecExtend<T, I::IntoIter>>::from_iter(iter.into_iter()) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> IntoIterator for Vec<T> { - type Item = T; - type IntoIter = IntoIter<T>; - - /// 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. - /// - /// # Examples - /// - /// ``` - /// let v = vec!["a".to_string(), "b".to_string()]; - /// for s in v.into_iter() { - /// // s has type String, not &String - /// println!("{}", s); - /// } - /// ``` - #[inline] - fn into_iter(self) -> IntoIter<T> { - unsafe { - let mut me = ManuallyDrop::new(self); - let begin = me.as_mut_ptr(); - let end = if mem::size_of::<T>() == 0 { - arith_offset(begin as *const i8, me.len() as isize) as *const T - } else { - begin.add(me.len()) as *const T - }; - let cap = me.buf.capacity(); - IntoIter { - buf: NonNull::new_unchecked(begin), - phantom: PhantomData, - cap, - ptr: begin, - end, - } - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> IntoIterator for &'a Vec<T> { - type Item = &'a T; - type IntoIter = slice::Iter<'a, T>; - - fn into_iter(self) -> slice::Iter<'a, T> { - self.iter() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> IntoIterator for &'a mut Vec<T> { - type Item = &'a mut T; - type IntoIter = slice::IterMut<'a, T>; - - fn into_iter(self) -> slice::IterMut<'a, T> { - self.iter_mut() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> Extend<T> for Vec<T> { - #[inline] - fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { - <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter()) - } - - #[inline] - fn extend_one(&mut self, item: T) { - self.push(item); - } - - #[inline] - fn extend_reserve(&mut self, additional: usize) { - self.reserve(additional); - } -} - -// Specialization trait used for Vec::from_iter and Vec::extend -trait SpecExtend<T, I> { - fn from_iter(iter: I) -> Self; - fn spec_extend(&mut self, iter: I); -} - -impl<T, I> SpecExtend<T, I> for Vec<T> -where - I: Iterator<Item = T>, -{ - default fn from_iter(mut iterator: I) -> Self { - // Unroll the first iteration, as the vector is going to be - // expanded on this iteration in every case when the iterable is not - // empty, but the loop in extend_desugared() is not going to see the - // vector being full in the few subsequent loop iterations. - // So we get better branch prediction. - let mut vector = match iterator.next() { - None => return Vec::new(), - Some(element) => { - let (lower, _) = iterator.size_hint(); - let mut vector = Vec::with_capacity(lower.saturating_add(1)); - unsafe { - ptr::write(vector.as_mut_ptr(), element); - vector.set_len(1); - } - vector - } - }; - <Vec<T> as SpecExtend<T, I>>::spec_extend(&mut vector, iterator); - vector - } - - default fn spec_extend(&mut self, iter: I) { - self.extend_desugared(iter) - } -} - -impl<T, I> SpecExtend<T, I> for Vec<T> -where - I: TrustedLen<Item = T>, -{ - default fn from_iter(iterator: I) -> Self { - let mut vector = Vec::new(); - vector.spec_extend(iterator); - vector - } - - default fn spec_extend(&mut self, iterator: I) { - // This is the case for a TrustedLen iterator. - let (low, high) = iterator.size_hint(); - if let Some(high_value) = high { - debug_assert_eq!( - low, - high_value, - "TrustedLen iterator's size hint is not exact: {:?}", - (low, high) - ); - } - if let Some(additional) = high { - self.reserve(additional); - unsafe { - let mut ptr = self.as_mut_ptr().add(self.len()); - let mut local_len = SetLenOnDrop::new(&mut self.len); - iterator.for_each(move |element| { - ptr::write(ptr, element); - ptr = ptr.offset(1); - // NB can't overflow since we would have had to alloc the address space - local_len.increment_len(1); - }); - } - } else { - self.extend_desugared(iterator) - } - } -} - -impl<T> SpecExtend<T, IntoIter<T>> for Vec<T> { - fn from_iter(iterator: IntoIter<T>) -> Self { - // A common case is passing a vector into a function which immediately - // re-collects into a vector. We can short circuit this if the IntoIter - // has not been advanced at all. - if iterator.buf.as_ptr() as *const _ == iterator.ptr { - unsafe { - let it = ManuallyDrop::new(iterator); - Vec::from_raw_parts(it.buf.as_ptr(), it.len(), it.cap) - } - } else { - let mut vector = Vec::new(); - vector.spec_extend(iterator); - vector - } - } - - fn spec_extend(&mut self, mut iterator: IntoIter<T>) { - unsafe { - self.append_elements(iterator.as_slice() as _); - } - iterator.ptr = iterator.end; - } -} - -impl<'a, T: 'a, I> SpecExtend<&'a T, I> for Vec<T> -where - I: Iterator<Item = &'a T>, - T: Clone, -{ - default fn from_iter(iterator: I) -> Self { - SpecExtend::from_iter(iterator.cloned()) - } - - default fn spec_extend(&mut self, iterator: I) { - self.spec_extend(iterator.cloned()) - } -} - -impl<'a, T: 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T> -where - T: Copy, -{ - fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) { - let slice = iterator.as_slice(); - self.reserve(slice.len()); - unsafe { - let len = self.len(); - let dst_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(len), slice.len()); - dst_slice.copy_from_slice(slice); - self.set_len(len + slice.len()); - } - } -} - -impl<T> Vec<T> { - fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) { - // This is the case for a general iterator. - // - // This function should be the moral equivalent of: - // - // for item in iterator { - // self.push(item); - // } - while let Some(element) = iterator.next() { - let len = self.len(); - if len == self.capacity() { - let (lower, _) = iterator.size_hint(); - self.reserve(lower.saturating_add(1)); - } - unsafe { - ptr::write(self.as_mut_ptr().add(len), element); - // NB can't overflow since we would have had to alloc the address space - self.set_len(len + 1); - } - } - } - - /// Creates a splicing iterator that replaces the specified range in the vector - /// with the given `replace_with` iterator and yields the removed items. - /// `replace_with` does not need to be the same length as `range`. - /// - /// The element range is removed even if the iterator is not consumed until the end. - /// - /// It is unspecified how many elements are removed from the vector - /// if the `Splice` value is leaked. - /// - /// The input iterator `replace_with` is only consumed when the `Splice` value is dropped. - /// - /// This is optimal if: - /// - /// * The tail (elements in the vector after `range`) is empty, - /// * or `replace_with` yields fewer elements than `range`’s length - /// * or the lower bound of its `size_hint()` is exact. - /// - /// Otherwise, a temporary vector is allocated and the tail is moved twice. - /// - /// # Panics - /// - /// Panics if the starting point is greater than the end point or if - /// the end point is greater than the length of the vector. - /// - /// # Examples - /// - /// ``` - /// let mut v = vec![1, 2, 3]; - /// let new = [7, 8]; - /// let u: Vec<_> = v.splice(..2, new.iter().cloned()).collect(); - /// assert_eq!(v, &[7, 8, 3]); - /// assert_eq!(u, &[1, 2]); - /// ``` - #[inline] - #[stable(feature = "vec_splice", since = "1.21.0")] - pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter> - where - R: RangeBounds<usize>, - I: IntoIterator<Item = T>, - { - Splice { drain: self.drain(range), replace_with: replace_with.into_iter() } - } - - /// Creates an iterator which uses a closure to determine if an element should be removed. - /// - /// If the closure returns true, then the element is removed and yielded. - /// If the closure returns false, the element will remain in the vector and will not be yielded - /// by the iterator. - /// - /// Using this method is equivalent to the following code: - /// - /// ``` - /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 }; - /// # let mut vec = vec![1, 2, 3, 4, 5, 6]; - /// let mut i = 0; - /// while i != vec.len() { - /// if some_predicate(&mut vec[i]) { - /// let val = vec.remove(i); - /// // your code here - /// } else { - /// i += 1; - /// } - /// } - /// - /// # assert_eq!(vec, vec![1, 4, 5]); - /// ``` - /// - /// But `drain_filter` is easier to use. `drain_filter` is also more efficient, - /// because it can backshift the elements of the array in bulk. - /// - /// Note that `drain_filter` also lets you mutate every element in the filter closure, - /// regardless of whether you choose to keep or remove it. - /// - /// - /// # Examples - /// - /// Splitting an array into evens and odds, reusing the original allocation: - /// - /// ``` - /// #![feature(drain_filter)] - /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15]; - /// - /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>(); - /// let odds = numbers; - /// - /// assert_eq!(evens, vec![2, 4, 6, 8, 14]); - /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]); - /// ``` - #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] - pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F> - where - F: FnMut(&mut T) -> bool, - { - let old_len = self.len(); - - // Guard against us getting leaked (leak amplification) - unsafe { - self.set_len(0); - } - - DrainFilter { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false } - } -} - -/// Extend implementation that copies elements out of references before pushing them onto the Vec. -/// -/// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to -/// append the entire slice at once. -/// -/// [`copy_from_slice`]: ../../std/primitive.slice.html#method.copy_from_slice -#[stable(feature = "extend_ref", since = "1.2.0")] -impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> { - fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { - self.spec_extend(iter.into_iter()) - } - - #[inline] - fn extend_one(&mut self, &item: &'a T) { - self.push(item); - } - - #[inline] - fn extend_reserve(&mut self, additional: usize) { - self.reserve(additional); - } -} - -macro_rules! __impl_slice_eq1 { - ([$($vars:tt)*] $lhs:ty, $rhs:ty $(where $ty:ty: $bound:ident)?, #[$stability:meta]) => { - #[$stability] - impl<A, B, $($vars)*> PartialEq<$rhs> for $lhs - where - A: PartialEq<B>, - $($ty: $bound)? - { - #[inline] - fn eq(&self, other: &$rhs) -> bool { self[..] == other[..] } - #[inline] - fn ne(&self, other: &$rhs) -> bool { self[..] != other[..] } - } - } -} - -__impl_slice_eq1! { [] Vec<A>, Vec<B>, #[stable(feature = "rust1", since = "1.0.0")] } -__impl_slice_eq1! { [] Vec<A>, &[B], #[stable(feature = "rust1", since = "1.0.0")] } -__impl_slice_eq1! { [] Vec<A>, &mut [B], #[stable(feature = "rust1", since = "1.0.0")] } -__impl_slice_eq1! { [] &[A], Vec<B>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] } -__impl_slice_eq1! { [] &mut [A], Vec<B>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] } -__impl_slice_eq1! { [] Cow<'_, [A]>, Vec<B> where A: Clone, #[stable(feature = "rust1", since = "1.0.0")] } -__impl_slice_eq1! { [] Cow<'_, [A]>, &[B] where A: Clone, #[stable(feature = "rust1", since = "1.0.0")] } -__impl_slice_eq1! { [] Cow<'_, [A]>, &mut [B] where A: Clone, #[stable(feature = "rust1", since = "1.0.0")] } -__impl_slice_eq1! { [const N: usize] Vec<A>, [B; N], #[stable(feature = "rust1", since = "1.0.0")] } -__impl_slice_eq1! { [const N: usize] Vec<A>, &[B; N], #[stable(feature = "rust1", since = "1.0.0")] } - -// NOTE: some less important impls are omitted to reduce code bloat -// FIXME(Centril): Reconsider this? -//__impl_slice_eq1! { [const N: usize] Vec<A>, &mut [B; N], } -//__impl_slice_eq1! { [const N: usize] [A; N], Vec<B>, } -//__impl_slice_eq1! { [const N: usize] &[A; N], Vec<B>, } -//__impl_slice_eq1! { [const N: usize] &mut [A; N], Vec<B>, } -//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, [B; N], } -//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &[B; N], } -//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &mut [B; N], } - -/// Implements comparison of vectors, lexicographically. -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: PartialOrd> PartialOrd for Vec<T> { - #[inline] - fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> { - PartialOrd::partial_cmp(&**self, &**other) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: Eq> Eq for Vec<T> {} - -/// Implements ordering of vectors, lexicographically. -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: Ord> Ord for Vec<T> { - #[inline] - fn cmp(&self, other: &Vec<T>) -> Ordering { - Ord::cmp(&**self, &**other) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -unsafe impl<#[may_dangle] T> Drop for Vec<T> { - fn drop(&mut self) { - unsafe { - // use drop for [T] - // use a raw slice to refer to the elements of the vector as weakest necessary type; - // could avoid questions of validity in certain cases - ptr::drop_in_place(ptr::slice_from_raw_parts_mut(self.as_mut_ptr(), self.len)) - } - // RawVec handles deallocation - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> Default for Vec<T> { - /// Creates an empty `Vec<T>`. - fn default() -> Vec<T> { - Vec::new() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: fmt::Debug> fmt::Debug for Vec<T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&**self, f) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> AsRef<Vec<T>> for Vec<T> { - fn as_ref(&self) -> &Vec<T> { - self - } -} - -#[stable(feature = "vec_as_mut", since = "1.5.0")] -impl<T> AsMut<Vec<T>> for Vec<T> { - fn as_mut(&mut self) -> &mut Vec<T> { - self - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> AsRef<[T]> for Vec<T> { - fn as_ref(&self) -> &[T] { - self - } -} - -#[stable(feature = "vec_as_mut", since = "1.5.0")] -impl<T> AsMut<[T]> for Vec<T> { - fn as_mut(&mut self) -> &mut [T] { - self - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: Clone> From<&[T]> for Vec<T> { - #[cfg(not(test))] - fn from(s: &[T]) -> Vec<T> { - s.to_vec() - } - #[cfg(test)] - fn from(s: &[T]) -> Vec<T> { - crate::slice::to_vec(s) - } -} - -#[stable(feature = "vec_from_mut", since = "1.19.0")] -impl<T: Clone> From<&mut [T]> for Vec<T> { - #[cfg(not(test))] - fn from(s: &mut [T]) -> Vec<T> { - s.to_vec() - } - #[cfg(test)] - fn from(s: &mut [T]) -> Vec<T> { - crate::slice::to_vec(s) - } -} - -#[stable(feature = "vec_from_array", since = "1.44.0")] -impl<T, const N: usize> From<[T; N]> for Vec<T> { - #[cfg(not(test))] - fn from(s: [T; N]) -> Vec<T> { - <[T]>::into_vec(box s) - } - #[cfg(test)] - fn from(s: [T; N]) -> Vec<T> { - crate::slice::into_vec(box s) - } -} - -#[stable(feature = "vec_from_cow_slice", since = "1.14.0")] -impl<'a, T> From<Cow<'a, [T]>> for Vec<T> -where - [T]: ToOwned<Owned = Vec<T>>, -{ - fn from(s: Cow<'a, [T]>) -> Vec<T> { - s.into_owned() - } -} - -// note: test pulls in libstd, which causes errors here -#[cfg(not(test))] -#[stable(feature = "vec_from_box", since = "1.18.0")] -impl<T> From<Box<[T]>> for Vec<T> { - fn from(s: Box<[T]>) -> Vec<T> { - s.into_vec() - } -} - -// note: test pulls in libstd, which causes errors here -#[cfg(not(test))] -#[stable(feature = "box_from_vec", since = "1.20.0")] -impl<T> From<Vec<T>> for Box<[T]> { - fn from(v: Vec<T>) -> Box<[T]> { - v.into_boxed_slice() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl From<&str> for Vec<u8> { - fn from(s: &str) -> Vec<u8> { - From::from(s.as_bytes()) - } -} - -//////////////////////////////////////////////////////////////////////////////// -// Clone-on-write -//////////////////////////////////////////////////////////////////////////////// - -#[stable(feature = "cow_from_vec", since = "1.8.0")] -impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> { - fn from(s: &'a [T]) -> Cow<'a, [T]> { - Cow::Borrowed(s) - } -} - -#[stable(feature = "cow_from_vec", since = "1.8.0")] -impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> { - fn from(v: Vec<T>) -> Cow<'a, [T]> { - Cow::Owned(v) - } -} - -#[stable(feature = "cow_from_vec_ref", since = "1.28.0")] -impl<'a, T: Clone> From<&'a Vec<T>> for Cow<'a, [T]> { - fn from(v: &'a Vec<T>) -> Cow<'a, [T]> { - Cow::Borrowed(v.as_slice()) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> FromIterator<T> for Cow<'a, [T]> -where - T: Clone, -{ - fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> { - Cow::Owned(FromIterator::from_iter(it)) - } -} - -//////////////////////////////////////////////////////////////////////////////// -// Iterators -//////////////////////////////////////////////////////////////////////////////// - -/// An iterator that moves out of a vector. -/// -/// This `struct` is created by the `into_iter` method on [`Vec`] (provided -/// by the [`IntoIterator`] trait). -/// -/// [`Vec`]: struct.Vec.html -/// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html -#[stable(feature = "rust1", since = "1.0.0")] -pub struct IntoIter<T> { - buf: NonNull<T>, - phantom: PhantomData<T>, - cap: usize, - ptr: *const T, - end: *const T, -} - -#[stable(feature = "vec_intoiter_debug", since = "1.13.0")] -impl<T: fmt::Debug> fmt::Debug for IntoIter<T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_tuple("IntoIter").field(&self.as_slice()).finish() - } -} - -impl<T> IntoIter<T> { - /// Returns the remaining items of this iterator as a slice. - /// - /// # Examples - /// - /// ``` - /// let vec = vec!['a', 'b', 'c']; - /// let mut into_iter = vec.into_iter(); - /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']); - /// let _ = into_iter.next().unwrap(); - /// assert_eq!(into_iter.as_slice(), &['b', 'c']); - /// ``` - #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")] - pub fn as_slice(&self) -> &[T] { - unsafe { slice::from_raw_parts(self.ptr, self.len()) } - } - - /// Returns the remaining items of this iterator as a mutable slice. - /// - /// # Examples - /// - /// ``` - /// let vec = vec!['a', 'b', 'c']; - /// let mut into_iter = vec.into_iter(); - /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']); - /// into_iter.as_mut_slice()[2] = 'z'; - /// assert_eq!(into_iter.next().unwrap(), 'a'); - /// assert_eq!(into_iter.next().unwrap(), 'b'); - /// assert_eq!(into_iter.next().unwrap(), 'z'); - /// ``` - #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")] - pub fn as_mut_slice(&mut self) -> &mut [T] { - unsafe { &mut *self.as_raw_mut_slice() } - } - - fn as_raw_mut_slice(&mut self) -> *mut [T] { - ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len()) - } -} - -#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")] -impl<T> AsRef<[T]> for IntoIter<T> { - fn as_ref(&self) -> &[T] { - self.as_slice() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -unsafe impl<T: Send> Send for IntoIter<T> {} -#[stable(feature = "rust1", since = "1.0.0")] -unsafe impl<T: Sync> Sync for IntoIter<T> {} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> Iterator for IntoIter<T> { - type Item = T; - - #[inline] - fn next(&mut self) -> Option<T> { - unsafe { - if self.ptr as *const _ == self.end { - None - } else { - if mem::size_of::<T>() == 0 { - // purposefully don't use 'ptr.offset' because for - // vectors with 0-size elements this would return the - // same pointer. - self.ptr = arith_offset(self.ptr as *const i8, 1) as *mut T; - - // Make up a value of this ZST. - Some(mem::zeroed()) - } else { - let old = self.ptr; - self.ptr = self.ptr.offset(1); - - Some(ptr::read(old)) - } - } - } - } - - #[inline] - fn size_hint(&self) -> (usize, Option<usize>) { - let exact = if mem::size_of::<T>() == 0 { - (self.end as usize).wrapping_sub(self.ptr as usize) - } else { - unsafe { self.end.offset_from(self.ptr) as usize } - }; - (exact, Some(exact)) - } - - #[inline] - fn count(self) -> usize { - self.len() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> DoubleEndedIterator for IntoIter<T> { - #[inline] - fn next_back(&mut self) -> Option<T> { - unsafe { - if self.end == self.ptr { - None - } else { - if mem::size_of::<T>() == 0 { - // See above for why 'ptr.offset' isn't used - self.end = arith_offset(self.end as *const i8, -1) as *mut T; - - // Make up a value of this ZST. - Some(mem::zeroed()) - } else { - self.end = self.end.offset(-1); - - Some(ptr::read(self.end)) - } - } - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> ExactSizeIterator for IntoIter<T> { - fn is_empty(&self) -> bool { - self.ptr == self.end - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl<T> FusedIterator for IntoIter<T> {} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl<T> TrustedLen for IntoIter<T> {} - -#[stable(feature = "vec_into_iter_clone", since = "1.8.0")] -impl<T: Clone> Clone for IntoIter<T> { - fn clone(&self) -> IntoIter<T> { - self.as_slice().to_owned().into_iter() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -unsafe impl<#[may_dangle] T> Drop for IntoIter<T> { - fn drop(&mut self) { - struct DropGuard<'a, T>(&'a mut IntoIter<T>); - - impl<T> Drop for DropGuard<'_, T> { - fn drop(&mut self) { - // RawVec handles deallocation - let _ = unsafe { RawVec::from_raw_parts(self.0.buf.as_ptr(), self.0.cap) }; - } - } - - let guard = DropGuard(self); - // destroy the remaining elements - unsafe { - ptr::drop_in_place(guard.0.as_raw_mut_slice()); - } - // now `guard` will be dropped and do the rest - } -} - -/// A draining iterator for `Vec<T>`. -/// -/// This `struct` is created by the [`drain`] method on [`Vec`]. -/// -/// [`drain`]: struct.Vec.html#method.drain -/// [`Vec`]: struct.Vec.html -#[stable(feature = "drain", since = "1.6.0")] -pub struct Drain<'a, T: 'a> { - /// Index of tail to preserve - tail_start: usize, - /// Length of tail - tail_len: usize, - /// Current remaining range to remove - iter: slice::Iter<'a, T>, - vec: NonNull<Vec<T>>, -} - -#[stable(feature = "collection_debug", since = "1.17.0")] -impl<T: fmt::Debug> fmt::Debug for Drain<'_, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_tuple("Drain").field(&self.iter.as_slice()).finish() - } -} - -impl<'a, T> Drain<'a, T> { - /// Returns the remaining items of this iterator as a slice. - /// - /// # Examples - /// - /// ``` - /// let mut vec = vec!['a', 'b', 'c']; - /// let mut drain = vec.drain(..); - /// assert_eq!(drain.as_slice(), &['a', 'b', 'c']); - /// let _ = drain.next().unwrap(); - /// assert_eq!(drain.as_slice(), &['b', 'c']); - /// ``` - #[stable(feature = "vec_drain_as_slice", since = "1.46.0")] - pub fn as_slice(&self) -> &[T] { - self.iter.as_slice() - } -} - -#[stable(feature = "vec_drain_as_slice", since = "1.46.0")] -impl<'a, T> AsRef<[T]> for Drain<'a, T> { - fn as_ref(&self) -> &[T] { - self.as_slice() - } -} - -#[stable(feature = "drain", since = "1.6.0")] -unsafe impl<T: Sync> Sync for Drain<'_, T> {} -#[stable(feature = "drain", since = "1.6.0")] -unsafe impl<T: Send> Send for Drain<'_, T> {} - -#[stable(feature = "drain", since = "1.6.0")] -impl<T> Iterator for Drain<'_, T> { - type Item = T; - - #[inline] - fn next(&mut self) -> Option<T> { - self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) }) - } - - fn size_hint(&self) -> (usize, Option<usize>) { - self.iter.size_hint() - } -} - -#[stable(feature = "drain", since = "1.6.0")] -impl<T> DoubleEndedIterator for Drain<'_, T> { - #[inline] - fn next_back(&mut self) -> Option<T> { - self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) }) - } -} - -#[stable(feature = "drain", since = "1.6.0")] -impl<T> Drop for Drain<'_, T> { - fn drop(&mut self) { - /// Continues dropping the remaining elements in the `Drain`, then moves back the - /// un-`Drain`ed elements to restore the original `Vec`. - struct DropGuard<'r, 'a, T>(&'r mut Drain<'a, T>); - - impl<'r, 'a, T> Drop for DropGuard<'r, 'a, T> { - fn drop(&mut self) { - // Continue the same loop we have below. If the loop already finished, this does - // nothing. - self.0.for_each(drop); - - if self.0.tail_len > 0 { - unsafe { - let source_vec = self.0.vec.as_mut(); - // memmove back untouched tail, update to new length - let start = source_vec.len(); - let tail = self.0.tail_start; - if tail != start { - let src = source_vec.as_ptr().add(tail); - let dst = source_vec.as_mut_ptr().add(start); - ptr::copy(src, dst, self.0.tail_len); - } - source_vec.set_len(start + self.0.tail_len); - } - } - } - } - - // exhaust self first - while let Some(item) = self.next() { - let guard = DropGuard(self); - drop(item); - mem::forget(guard); - } - - // Drop a `DropGuard` to move back the non-drained tail of `self`. - DropGuard(self); - } -} - -#[stable(feature = "drain", since = "1.6.0")] -impl<T> ExactSizeIterator for Drain<'_, T> { - fn is_empty(&self) -> bool { - self.iter.is_empty() - } -} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl<T> TrustedLen for Drain<'_, T> {} - -#[stable(feature = "fused", since = "1.26.0")] -impl<T> FusedIterator for Drain<'_, T> {} - -/// A splicing iterator for `Vec`. -/// -/// This struct is created by the [`splice()`] method on [`Vec`]. See its -/// documentation for more. -/// -/// [`splice()`]: struct.Vec.html#method.splice -/// [`Vec`]: struct.Vec.html -#[derive(Debug)] -#[stable(feature = "vec_splice", since = "1.21.0")] -pub struct Splice<'a, I: Iterator + 'a> { - drain: Drain<'a, I::Item>, - replace_with: I, -} - -#[stable(feature = "vec_splice", since = "1.21.0")] -impl<I: Iterator> Iterator for Splice<'_, I> { - type Item = I::Item; - - fn next(&mut self) -> Option<Self::Item> { - self.drain.next() - } - - fn size_hint(&self) -> (usize, Option<usize>) { - self.drain.size_hint() - } -} - -#[stable(feature = "vec_splice", since = "1.21.0")] -impl<I: Iterator> DoubleEndedIterator for Splice<'_, I> { - fn next_back(&mut self) -> Option<Self::Item> { - self.drain.next_back() - } -} - -#[stable(feature = "vec_splice", since = "1.21.0")] -impl<I: Iterator> ExactSizeIterator for Splice<'_, I> {} - -#[stable(feature = "vec_splice", since = "1.21.0")] -impl<I: Iterator> Drop for Splice<'_, I> { - fn drop(&mut self) { - self.drain.by_ref().for_each(drop); - - unsafe { - if self.drain.tail_len == 0 { - self.drain.vec.as_mut().extend(self.replace_with.by_ref()); - return; - } - - // First fill the range left by drain(). - if !self.drain.fill(&mut self.replace_with) { - return; - } - - // There may be more elements. Use the lower bound as an estimate. - // FIXME: Is the upper bound a better guess? Or something else? - let (lower_bound, _upper_bound) = self.replace_with.size_hint(); - if lower_bound > 0 { - self.drain.move_tail(lower_bound); - if !self.drain.fill(&mut self.replace_with) { - return; - } - } - - // Collect any remaining elements. - // This is a zero-length vector which does not allocate if `lower_bound` was exact. - let mut collected = self.replace_with.by_ref().collect::<Vec<I::Item>>().into_iter(); - // Now we have an exact count. - if collected.len() > 0 { - self.drain.move_tail(collected.len()); - let filled = self.drain.fill(&mut collected); - debug_assert!(filled); - debug_assert_eq!(collected.len(), 0); - } - } - // Let `Drain::drop` move the tail back if necessary and restore `vec.len`. - } -} - -/// Private helper methods for `Splice::drop` -impl<T> Drain<'_, T> { - /// The range from `self.vec.len` to `self.tail_start` contains elements - /// that have been moved out. - /// Fill that range as much as possible with new elements from the `replace_with` iterator. - /// Returns `true` if we filled the entire range. (`replace_with.next()` didn’t return `None`.) - unsafe fn fill<I: Iterator<Item = T>>(&mut self, replace_with: &mut I) -> bool { - let vec = unsafe { self.vec.as_mut() }; - let range_start = vec.len; - let range_end = self.tail_start; - let range_slice = unsafe { - slice::from_raw_parts_mut(vec.as_mut_ptr().add(range_start), range_end - range_start) - }; - - for place in range_slice { - if let Some(new_item) = replace_with.next() { - unsafe { ptr::write(place, new_item) }; - vec.len += 1; - } else { - return false; - } - } - true - } - - /// Makes room for inserting more elements before the tail. - unsafe fn move_tail(&mut self, additional: usize) { - let vec = unsafe { self.vec.as_mut() }; - let len = self.tail_start + self.tail_len; - vec.buf.reserve(len, additional); - - let new_tail_start = self.tail_start + additional; - unsafe { - let src = vec.as_ptr().add(self.tail_start); - let dst = vec.as_mut_ptr().add(new_tail_start); - ptr::copy(src, dst, self.tail_len); - } - self.tail_start = new_tail_start; - } -} - -/// An iterator produced by calling `drain_filter` on Vec. -#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] -#[derive(Debug)] -pub struct DrainFilter<'a, T, F> -where - F: FnMut(&mut T) -> bool, -{ - vec: &'a mut Vec<T>, - /// The index of the item that will be inspected by the next call to `next`. - idx: usize, - /// The number of items that have been drained (removed) thus far. - del: usize, - /// The original length of `vec` prior to draining. - old_len: usize, - /// The filter test predicate. - pred: F, - /// A flag that indicates a panic has occurred in the filter test prodicate. - /// This is used as a hint in the drop implementation to prevent consumption - /// of the remainder of the `DrainFilter`. Any unprocessed items will be - /// backshifted in the `vec`, but no further items will be dropped or - /// tested by the filter predicate. - panic_flag: bool, -} - -#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] -impl<T, F> Iterator for DrainFilter<'_, T, F> -where - F: FnMut(&mut T) -> bool, -{ - type Item = T; - - fn next(&mut self) -> Option<T> { - unsafe { - while self.idx < self.old_len { - let i = self.idx; - let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len); - self.panic_flag = true; - let drained = (self.pred)(&mut v[i]); - self.panic_flag = false; - // Update the index *after* the predicate is called. If the index - // is updated prior and the predicate panics, the element at this - // index would be leaked. - self.idx += 1; - if drained { - self.del += 1; - return Some(ptr::read(&v[i])); - } else if self.del > 0 { - let del = self.del; - let src: *const T = &v[i]; - let dst: *mut T = &mut v[i - del]; - ptr::copy_nonoverlapping(src, dst, 1); - } - } - None - } - } - - fn size_hint(&self) -> (usize, Option<usize>) { - (0, Some(self.old_len - self.idx)) - } -} - -#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] -impl<T, F> Drop for DrainFilter<'_, T, F> -where - F: FnMut(&mut T) -> bool, -{ - fn drop(&mut self) { - struct BackshiftOnDrop<'a, 'b, T, F> - where - F: FnMut(&mut T) -> bool, - { - drain: &'b mut DrainFilter<'a, T, F>, - } - - impl<'a, 'b, T, F> Drop for BackshiftOnDrop<'a, 'b, T, F> - where - F: FnMut(&mut T) -> bool, - { - fn drop(&mut self) { - unsafe { - if self.drain.idx < self.drain.old_len && self.drain.del > 0 { - // This is a pretty messed up state, and there isn't really an - // obviously right thing to do. We don't want to keep trying - // to execute `pred`, so we just backshift all the unprocessed - // elements and tell the vec that they still exist. The backshift - // is required to prevent a double-drop of the last successfully - // drained item prior to a panic in the predicate. - let ptr = self.drain.vec.as_mut_ptr(); - let src = ptr.add(self.drain.idx); - let dst = src.sub(self.drain.del); - let tail_len = self.drain.old_len - self.drain.idx; - src.copy_to(dst, tail_len); - } - self.drain.vec.set_len(self.drain.old_len - self.drain.del); - } - } - } - - let backshift = BackshiftOnDrop { drain: self }; - - // Attempt to consume any remaining elements if the filter predicate - // has not yet panicked. We'll backshift any remaining elements - // whether we've already panicked or if the consumption here panics. - if !backshift.drain.panic_flag { - backshift.drain.for_each(drop); - } - } -} |