3610 lines
124 KiB
Rust
3610 lines
124 KiB
Rust
// SPDX-License-Identifier: Apache-2.0 OR MIT
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//! A contiguous growable array type with heap-allocated contents, written
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//! `Vec<T>`.
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//!
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//! Vectors have *O*(1) indexing, amortized *O*(1) push (to the end) and
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//! *O*(1) pop (from the end).
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//!
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//! Vectors ensure they never allocate more than `isize::MAX` bytes.
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//!
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//! # Examples
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//!
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//! You can explicitly create a [`Vec`] with [`Vec::new`]:
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//!
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//! ```
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//! let v: Vec<i32> = Vec::new();
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//! ```
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//!
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//! ...or by using the [`vec!`] macro:
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//!
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//! ```
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//! let v: Vec<i32> = vec![];
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//!
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//! let v = vec![1, 2, 3, 4, 5];
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//!
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//! let v = vec![0; 10]; // ten zeroes
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//! ```
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//!
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//! You can [`push`] values onto the end of a vector (which will grow the vector
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//! as needed):
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//!
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//! ```
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//! let mut v = vec![1, 2];
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//!
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//! v.push(3);
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//! ```
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//!
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//! Popping values works in much the same way:
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//!
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//! ```
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//! let mut v = vec![1, 2];
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//!
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//! let two = v.pop();
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//! ```
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//!
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//! Vectors also support indexing (through the [`Index`] and [`IndexMut`] traits):
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//!
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//! ```
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//! let mut v = vec![1, 2, 3];
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//! let three = v[2];
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//! v[1] = v[1] + 5;
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//! ```
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//!
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//! [`push`]: Vec::push
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#![stable(feature = "rust1", since = "1.0.0")]
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#[cfg(not(no_global_oom_handling))]
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use core::cmp;
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use core::cmp::Ordering;
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use core::convert::TryFrom;
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use core::fmt;
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use core::hash::{Hash, Hasher};
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use core::intrinsics::assume;
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use core::iter;
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#[cfg(not(no_global_oom_handling))]
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use core::iter::FromIterator;
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use core::marker::PhantomData;
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use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
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use core::ops::{self, Index, IndexMut, Range, RangeBounds};
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use core::ptr::{self, NonNull};
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use core::slice::{self, SliceIndex};
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use crate::alloc::{Allocator, Global};
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#[cfg(not(no_borrow))]
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use crate::borrow::{Cow, ToOwned};
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use crate::boxed::Box;
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use crate::collections::{TryReserveError, TryReserveErrorKind};
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use crate::raw_vec::RawVec;
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#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
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pub use self::drain_filter::DrainFilter;
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mod drain_filter;
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_splice", since = "1.21.0")]
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pub use self::splice::Splice;
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#[cfg(not(no_global_oom_handling))]
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mod splice;
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#[stable(feature = "drain", since = "1.6.0")]
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pub use self::drain::Drain;
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mod drain;
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#[cfg(not(no_borrow))]
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#[cfg(not(no_global_oom_handling))]
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mod cow;
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#[cfg(not(no_global_oom_handling))]
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pub(crate) use self::in_place_collect::AsVecIntoIter;
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use self::into_iter::IntoIter;
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mod into_iter;
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#[cfg(not(no_global_oom_handling))]
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use self::is_zero::IsZero;
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mod is_zero;
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#[cfg(not(no_global_oom_handling))]
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mod in_place_collect;
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mod partial_eq;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_from_elem::SpecFromElem;
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#[cfg(not(no_global_oom_handling))]
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mod spec_from_elem;
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use self::set_len_on_drop::SetLenOnDrop;
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mod set_len_on_drop;
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#[cfg(not(no_global_oom_handling))]
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use self::in_place_drop::{InPlaceDrop, InPlaceDstBufDrop};
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#[cfg(not(no_global_oom_handling))]
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mod in_place_drop;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_from_iter_nested::SpecFromIterNested;
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#[cfg(not(no_global_oom_handling))]
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mod spec_from_iter_nested;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_from_iter::SpecFromIter;
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#[cfg(not(no_global_oom_handling))]
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mod spec_from_iter;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_extend::SpecExtend;
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use self::spec_extend::TrySpecExtend;
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mod spec_extend;
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/// A contiguous growable array type, written as `Vec<T>`, short for 'vector'.
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///
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/// # Examples
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///
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/// ```
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/// let mut vec = Vec::new();
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/// vec.push(1);
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/// vec.push(2);
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///
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/// assert_eq!(vec.len(), 2);
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/// assert_eq!(vec[0], 1);
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///
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/// assert_eq!(vec.pop(), Some(2));
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/// assert_eq!(vec.len(), 1);
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///
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/// vec[0] = 7;
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/// assert_eq!(vec[0], 7);
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///
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/// vec.extend([1, 2, 3]);
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///
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/// for x in &vec {
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/// println!("{x}");
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/// }
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/// assert_eq!(vec, [7, 1, 2, 3]);
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/// ```
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///
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/// The [`vec!`] macro is provided for convenient initialization:
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///
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/// ```
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/// let mut vec1 = vec![1, 2, 3];
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/// vec1.push(4);
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/// let vec2 = Vec::from([1, 2, 3, 4]);
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/// assert_eq!(vec1, vec2);
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/// ```
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///
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/// It can also initialize each element of a `Vec<T>` with a given value.
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/// This may be more efficient than performing allocation and initialization
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/// in separate steps, especially when initializing a vector of zeros:
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///
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/// ```
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/// let vec = vec![0; 5];
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/// assert_eq!(vec, [0, 0, 0, 0, 0]);
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///
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/// // The following is equivalent, but potentially slower:
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/// let mut vec = Vec::with_capacity(5);
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/// vec.resize(5, 0);
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/// assert_eq!(vec, [0, 0, 0, 0, 0]);
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/// ```
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///
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/// For more information, see
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/// [Capacity and Reallocation](#capacity-and-reallocation).
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///
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/// Use a `Vec<T>` as an efficient stack:
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///
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/// ```
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/// let mut stack = Vec::new();
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///
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/// stack.push(1);
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/// stack.push(2);
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/// stack.push(3);
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///
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/// while let Some(top) = stack.pop() {
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/// // Prints 3, 2, 1
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/// println!("{top}");
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/// }
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/// ```
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///
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/// # Indexing
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///
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/// The `Vec` type allows to access values by index, because it implements the
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/// [`Index`] trait. An example will be more explicit:
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///
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/// ```
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/// let v = vec![0, 2, 4, 6];
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/// println!("{}", v[1]); // it will display '2'
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/// ```
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///
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/// However be careful: if you try to access an index which isn't in the `Vec`,
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/// your software will panic! You cannot do this:
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///
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/// ```should_panic
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/// let v = vec![0, 2, 4, 6];
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/// println!("{}", v[6]); // it will panic!
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/// ```
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///
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/// Use [`get`] and [`get_mut`] if you want to check whether the index is in
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/// the `Vec`.
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///
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/// # Slicing
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///
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/// A `Vec` can be mutable. On the other hand, slices are read-only objects.
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/// To get a [slice][prim@slice], use [`&`]. Example:
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///
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/// ```
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/// fn read_slice(slice: &[usize]) {
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/// // ...
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/// }
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///
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/// let v = vec![0, 1];
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/// read_slice(&v);
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///
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/// // ... and that's all!
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/// // you can also do it like this:
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/// let u: &[usize] = &v;
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/// // or like this:
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/// let u: &[_] = &v;
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/// ```
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///
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/// In Rust, it's more common to pass slices as arguments rather than vectors
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/// when you just want to provide read access. The same goes for [`String`] and
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/// [`&str`].
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///
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/// # Capacity and reallocation
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///
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/// The capacity of a vector is the amount of space allocated for any future
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/// elements that will be added onto the vector. This is not to be confused with
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/// the *length* of a vector, which specifies the number of actual elements
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/// within the vector. If a vector's length exceeds its capacity, its capacity
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/// will automatically be increased, but its elements will have to be
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/// reallocated.
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///
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/// For example, a vector with capacity 10 and length 0 would be an empty vector
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/// with space for 10 more elements. Pushing 10 or fewer elements onto the
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/// vector will not change its capacity or cause reallocation to occur. However,
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/// if the vector's length is increased to 11, it will have to reallocate, which
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/// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`]
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/// whenever possible to specify how big the vector is expected to get.
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///
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/// # Guarantees
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///
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/// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees
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/// about its design. This ensures that it's as low-overhead as possible in
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/// the general case, and can be correctly manipulated in primitive ways
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/// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`.
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/// If additional type parameters are added (e.g., to support custom allocators),
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/// overriding their defaults may change the behavior.
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///
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/// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length)
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/// triplet. No more, no less. The order of these fields is completely
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/// unspecified, and you should use the appropriate methods to modify these.
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/// The pointer will never be null, so this type is null-pointer-optimized.
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///
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/// However, the pointer might not actually point to allocated memory. In particular,
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/// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`],
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/// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`]
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/// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized
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/// types inside a `Vec`, it will not allocate space for them. *Note that in this case
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/// the `Vec` might not report a [`capacity`] of 0*. `Vec` will allocate if and only
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/// if <code>[mem::size_of::\<T>]\() * [capacity]\() > 0</code>. In general, `Vec`'s allocation
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/// details are very subtle --- if you intend to allocate memory using a `Vec`
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/// and use it for something else (either to pass to unsafe code, or to build your
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/// own memory-backed collection), be sure to deallocate this memory by using
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/// `from_raw_parts` to recover the `Vec` and then dropping it.
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///
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/// If a `Vec` *has* allocated memory, then the memory it points to is on the heap
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/// (as defined by the allocator Rust is configured to use by default), and its
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/// pointer points to [`len`] initialized, contiguous elements in order (what
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/// you would see if you coerced it to a slice), followed by <code>[capacity] - [len]</code>
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/// logically uninitialized, contiguous elements.
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///
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/// A vector containing the elements `'a'` and `'b'` with capacity 4 can be
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/// visualized as below. The top part is the `Vec` struct, it contains a
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/// pointer to the head of the allocation in the heap, length and capacity.
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/// The bottom part is the allocation on the heap, a contiguous memory block.
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///
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/// ```text
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/// ptr len capacity
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/// +--------+--------+--------+
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/// | 0x0123 | 2 | 4 |
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/// +--------+--------+--------+
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/// |
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/// v
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/// Heap +--------+--------+--------+--------+
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/// | 'a' | 'b' | uninit | uninit |
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/// +--------+--------+--------+--------+
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/// ```
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///
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/// - **uninit** represents memory that is not initialized, see [`MaybeUninit`].
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/// - Note: the ABI is not stable and `Vec` makes no guarantees about its memory
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/// layout (including the order of fields).
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///
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/// `Vec` will never perform a "small optimization" where elements are actually
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/// stored on the stack for two reasons:
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///
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/// * It would make it more difficult for unsafe code to correctly manipulate
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/// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were
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/// only moved, and it would be more difficult to determine if a `Vec` had
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/// actually allocated memory.
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///
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/// * It would penalize the general case, incurring an additional branch
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/// on every access.
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///
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/// `Vec` will never automatically shrink itself, even if completely empty. This
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/// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec`
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/// and then filling it back up to the same [`len`] should incur no calls to
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/// the allocator. If you wish to free up unused memory, use
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/// [`shrink_to_fit`] or [`shrink_to`].
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///
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/// [`push`] and [`insert`] will never (re)allocate if the reported capacity is
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/// sufficient. [`push`] and [`insert`] *will* (re)allocate if
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/// <code>[len] == [capacity]</code>. That is, the reported capacity is completely
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/// accurate, and can be relied on. It can even be used to manually free the memory
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/// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even
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/// when not necessary.
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///
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/// `Vec` does not guarantee any particular growth strategy when reallocating
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/// when full, nor when [`reserve`] is called. The current strategy is basic
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/// and it may prove desirable to use a non-constant growth factor. Whatever
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/// strategy is used will of course guarantee *O*(1) amortized [`push`].
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///
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/// `vec![x; n]`, `vec![a, b, c, d]`, and
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/// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
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/// with exactly the requested capacity. If <code>[len] == [capacity]</code>,
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/// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
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/// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
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///
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/// `Vec` will not specifically overwrite any data that is removed from it,
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/// but also won't specifically preserve it. Its uninitialized memory is
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/// scratch space that it may use however it wants. It will generally just do
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/// whatever is most efficient or otherwise easy to implement. Do not rely on
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/// removed data to be erased for security purposes. Even if you drop a `Vec`, its
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/// buffer may simply be reused by another allocation. Even if you zero a `Vec`'s memory
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/// first, that might not actually happen because the optimizer does not consider
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/// this a side-effect that must be preserved. There is one case which we will
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/// not break, however: using `unsafe` code to write to the excess capacity,
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/// and then increasing the length to match, is always valid.
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///
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/// Currently, `Vec` does not guarantee the order in which elements are dropped.
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/// The order has changed in the past and may change again.
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///
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/// [`get`]: ../../std/vec/struct.Vec.html#method.get
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/// [`get_mut`]: ../../std/vec/struct.Vec.html#method.get_mut
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/// [`String`]: crate::string::String
|
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/// [`&str`]: type@str
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/// [`shrink_to_fit`]: Vec::shrink_to_fit
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/// [`shrink_to`]: Vec::shrink_to
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/// [capacity]: Vec::capacity
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/// [`capacity`]: Vec::capacity
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/// [mem::size_of::\<T>]: core::mem::size_of
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/// [len]: Vec::len
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/// [`len`]: Vec::len
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/// [`push`]: Vec::push
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/// [`insert`]: Vec::insert
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/// [`reserve`]: Vec::reserve
|
||
/// [`MaybeUninit`]: core::mem::MaybeUninit
|
||
/// [owned slice]: Box
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[cfg_attr(not(test), rustc_diagnostic_item = "Vec")]
|
||
#[rustc_insignificant_dtor]
|
||
pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global> {
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buf: RawVec<T, A>,
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len: usize,
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}
|
||
|
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////////////////////////////////////////////////////////////////////////////////
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// Inherent methods
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////////////////////////////////////////////////////////////////////////////////
|
||
|
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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")]
|
||
#[must_use]
|
||
pub const fn new() -> Self {
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||
Vec { buf: RawVec::NEW, len: 0 }
|
||
}
|
||
|
||
/// Constructs a new, empty `Vec<T>` with at least the specified capacity.
|
||
///
|
||
/// The vector will be able to hold at least `capacity` elements without
|
||
/// reallocating. This method is allowed to allocate for more elements than
|
||
/// `capacity`. If `capacity` is 0, the vector will not allocate.
|
||
///
|
||
/// It is important to note that although the returned vector has the
|
||
/// minimum *capacity* specified, the vector will have a zero *length*. For
|
||
/// an explanation of the difference between length and capacity, see
|
||
/// *[Capacity and reallocation]*.
|
||
///
|
||
/// If it is important to know the exact allocated capacity of a `Vec`,
|
||
/// always use the [`capacity`] method after construction.
|
||
///
|
||
/// For `Vec<T>` where `T` is a zero-sized type, there will be no allocation
|
||
/// and the capacity will always be `usize::MAX`.
|
||
///
|
||
/// [Capacity and reallocation]: #capacity-and-reallocation
|
||
/// [`capacity`]: Vec::capacity
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the new capacity exceeds `isize::MAX` bytes.
|
||
///
|
||
/// # 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!(vec.capacity() >= 10);
|
||
///
|
||
/// // These are all done without reallocating...
|
||
/// for i in 0..10 {
|
||
/// vec.push(i);
|
||
/// }
|
||
/// assert_eq!(vec.len(), 10);
|
||
/// assert!(vec.capacity() >= 10);
|
||
///
|
||
/// // ...but this may make the vector reallocate
|
||
/// vec.push(11);
|
||
/// assert_eq!(vec.len(), 11);
|
||
/// assert!(vec.capacity() >= 11);
|
||
///
|
||
/// // A vector of a zero-sized type will always over-allocate, since no
|
||
/// // allocation is necessary
|
||
/// let vec_units = Vec::<()>::with_capacity(10);
|
||
/// assert_eq!(vec_units.capacity(), usize::MAX);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[must_use]
|
||
pub fn with_capacity(capacity: usize) -> Self {
|
||
Self::with_capacity_in(capacity, Global)
|
||
}
|
||
|
||
/// Tries to construct a new, empty `Vec<T>` with at least the specified capacity.
|
||
///
|
||
/// The vector will be able to hold at least `capacity` elements without
|
||
/// reallocating. This method is allowed to allocate for more elements than
|
||
/// `capacity`. If `capacity` is 0, the vector will not allocate.
|
||
///
|
||
/// It is important to note that although the returned vector has the
|
||
/// minimum *capacity* specified, the vector will have a zero *length*. For
|
||
/// an explanation of the difference between length and capacity, see
|
||
/// *[Capacity and reallocation]*.
|
||
///
|
||
/// If it is important to know the exact allocated capacity of a `Vec`,
|
||
/// always use the [`capacity`] method after construction.
|
||
///
|
||
/// For `Vec<T>` where `T` is a zero-sized type, there will be no allocation
|
||
/// and the capacity will always be `usize::MAX`.
|
||
///
|
||
/// [Capacity and reallocation]: #capacity-and-reallocation
|
||
/// [`capacity`]: Vec::capacity
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut vec = Vec::try_with_capacity(10).unwrap();
|
||
///
|
||
/// // The vector contains no items, even though it has capacity for more
|
||
/// assert_eq!(vec.len(), 0);
|
||
/// assert!(vec.capacity() >= 10);
|
||
///
|
||
/// // These are all done without reallocating...
|
||
/// for i in 0..10 {
|
||
/// vec.push(i);
|
||
/// }
|
||
/// assert_eq!(vec.len(), 10);
|
||
/// assert!(vec.capacity() >= 10);
|
||
///
|
||
/// // ...but this may make the vector reallocate
|
||
/// vec.push(11);
|
||
/// assert_eq!(vec.len(), 11);
|
||
/// assert!(vec.capacity() >= 11);
|
||
///
|
||
/// let mut result = Vec::try_with_capacity(usize::MAX);
|
||
/// assert!(result.is_err());
|
||
///
|
||
/// // A vector of a zero-sized type will always over-allocate, since no
|
||
/// // allocation is necessary
|
||
/// let vec_units = Vec::<()>::try_with_capacity(10).unwrap();
|
||
/// assert_eq!(vec_units.capacity(), usize::MAX);
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "kernel", since = "1.0.0")]
|
||
pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
|
||
Self::try_with_capacity_in(capacity, Global)
|
||
}
|
||
|
||
/// Creates a `Vec<T>` directly from a pointer, a capacity, and a length.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This is highly unsafe, due to the number of invariants that aren't
|
||
/// checked:
|
||
///
|
||
/// * `ptr` must have been allocated using the global allocator, such as via
|
||
/// the [`alloc::alloc`] function.
|
||
/// * `T` needs to have the same alignment as what `ptr` was allocated with.
|
||
/// (`T` having a less strict alignment is not sufficient, the alignment really
|
||
/// needs to be equal to satisfy the [`dealloc`] requirement that memory must be
|
||
/// allocated and deallocated with the same layout.)
|
||
/// * The size of `T` times the `capacity` (ie. the allocated size in bytes) needs
|
||
/// to be the same size as the pointer was allocated with. (Because similar to
|
||
/// alignment, [`dealloc`] must be called with the same layout `size`.)
|
||
/// * `length` needs to be less than or equal to `capacity`.
|
||
/// * The first `length` values must be properly initialized values of type `T`.
|
||
/// * `capacity` needs to be the capacity that the pointer was allocated with.
|
||
/// * The allocated size in bytes must be no larger than `isize::MAX`.
|
||
/// See the safety documentation of [`pointer::offset`].
|
||
///
|
||
/// These requirements are always upheld by any `ptr` that has been allocated
|
||
/// via `Vec<T>`. Other allocation sources are allowed if the invariants are
|
||
/// upheld.
|
||
///
|
||
/// Violating these may cause problems like corrupting the allocator's
|
||
/// internal data structures. For example it is normally **not** safe
|
||
/// to build a `Vec<u8>` from a pointer to a C `char` array with length
|
||
/// `size_t`, doing so is only safe if the array was initially allocated by
|
||
/// a `Vec` or `String`.
|
||
/// 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. To avoid
|
||
/// these issues, it is often preferable to do casting/transmuting using
|
||
/// [`slice::from_raw_parts`] instead.
|
||
///
|
||
/// 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`]: crate::string::String
|
||
/// [`alloc::alloc`]: crate::alloc::alloc
|
||
/// [`dealloc`]: crate::alloc::GlobalAlloc::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 {
|
||
/// ptr::write(p.add(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]);
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// Using memory that was allocated elsewhere:
|
||
///
|
||
/// ```rust
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::{AllocError, Allocator, Global, Layout};
|
||
///
|
||
/// fn main() {
|
||
/// let layout = Layout::array::<u32>(16).expect("overflow cannot happen");
|
||
///
|
||
/// let vec = unsafe {
|
||
/// let mem = match Global.allocate(layout) {
|
||
/// Ok(mem) => mem.cast::<u32>().as_ptr(),
|
||
/// Err(AllocError) => return,
|
||
/// };
|
||
///
|
||
/// mem.write(1_000_000);
|
||
///
|
||
/// Vec::from_raw_parts_in(mem, 1, 16, Global)
|
||
/// };
|
||
///
|
||
/// assert_eq!(vec, &[1_000_000]);
|
||
/// assert_eq!(vec.capacity(), 16);
|
||
/// }
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Self {
|
||
unsafe { Self::from_raw_parts_in(ptr, length, capacity, Global) }
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator> Vec<T, A> {
|
||
/// Constructs a new, empty `Vec<T, A>`.
|
||
///
|
||
/// The vector will not allocate until elements are pushed onto it.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// # #[allow(unused_mut)]
|
||
/// let mut vec: Vec<i32, _> = Vec::new_in(System);
|
||
/// ```
|
||
#[inline]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
pub const fn new_in(alloc: A) -> Self {
|
||
Vec { buf: RawVec::new_in(alloc), len: 0 }
|
||
}
|
||
|
||
/// Constructs a new, empty `Vec<T, A>` with at least the specified capacity
|
||
/// with the provided allocator.
|
||
///
|
||
/// The vector will be able to hold at least `capacity` elements without
|
||
/// reallocating. This method is allowed to allocate for more elements than
|
||
/// `capacity`. If `capacity` is 0, the vector will not allocate.
|
||
///
|
||
/// It is important to note that although the returned vector has the
|
||
/// minimum *capacity* specified, the vector will have a zero *length*. For
|
||
/// an explanation of the difference between length and capacity, see
|
||
/// *[Capacity and reallocation]*.
|
||
///
|
||
/// If it is important to know the exact allocated capacity of a `Vec`,
|
||
/// always use the [`capacity`] method after construction.
|
||
///
|
||
/// For `Vec<T, A>` where `T` is a zero-sized type, there will be no allocation
|
||
/// and the capacity will always be `usize::MAX`.
|
||
///
|
||
/// [Capacity and reallocation]: #capacity-and-reallocation
|
||
/// [`capacity`]: Vec::capacity
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the new capacity exceeds `isize::MAX` bytes.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let mut vec = Vec::with_capacity_in(10, System);
|
||
///
|
||
/// // 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);
|
||
///
|
||
/// // A vector of a zero-sized type will always over-allocate, since no
|
||
/// // allocation is necessary
|
||
/// let vec_units = Vec::<(), System>::with_capacity_in(10, System);
|
||
/// assert_eq!(vec_units.capacity(), usize::MAX);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
|
||
Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 }
|
||
}
|
||
|
||
/// Tries to construct a new, empty `Vec<T, A>` with at least the specified capacity
|
||
/// with the provided allocator.
|
||
///
|
||
/// The vector will be able to hold at least `capacity` elements without
|
||
/// reallocating. This method is allowed to allocate for more elements than
|
||
/// `capacity`. If `capacity` is 0, the vector will not allocate.
|
||
///
|
||
/// It is important to note that although the returned vector has the
|
||
/// minimum *capacity* specified, the vector will have a zero *length*. For
|
||
/// an explanation of the difference between length and capacity, see
|
||
/// *[Capacity and reallocation]*.
|
||
///
|
||
/// If it is important to know the exact allocated capacity of a `Vec`,
|
||
/// always use the [`capacity`] method after construction.
|
||
///
|
||
/// For `Vec<T, A>` where `T` is a zero-sized type, there will be no allocation
|
||
/// and the capacity will always be `usize::MAX`.
|
||
///
|
||
/// [Capacity and reallocation]: #capacity-and-reallocation
|
||
/// [`capacity`]: Vec::capacity
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let mut vec = Vec::try_with_capacity_in(10, System).unwrap();
|
||
///
|
||
/// // 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);
|
||
///
|
||
/// let mut result = Vec::try_with_capacity_in(usize::MAX, System);
|
||
/// assert!(result.is_err());
|
||
///
|
||
/// // A vector of a zero-sized type will always over-allocate, since no
|
||
/// // allocation is necessary
|
||
/// let vec_units = Vec::<(), System>::try_with_capacity_in(10, System).unwrap();
|
||
/// assert_eq!(vec_units.capacity(), usize::MAX);
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "kernel", since = "1.0.0")]
|
||
pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
|
||
Ok(Vec { buf: RawVec::try_with_capacity_in(capacity, alloc)?, len: 0 })
|
||
}
|
||
|
||
/// Creates a `Vec<T, A>` directly from a pointer, a capacity, a length,
|
||
/// and an allocator.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// This is highly unsafe, due to the number of invariants that aren't
|
||
/// checked:
|
||
///
|
||
/// * `ptr` must be [*currently allocated*] via the given allocator `alloc`.
|
||
/// * `T` needs to have the same alignment as what `ptr` was allocated with.
|
||
/// (`T` having a less strict alignment is not sufficient, the alignment really
|
||
/// needs to be equal to satisfy the [`dealloc`] requirement that memory must be
|
||
/// allocated and deallocated with the same layout.)
|
||
/// * The size of `T` times the `capacity` (ie. the allocated size in bytes) needs
|
||
/// to be the same size as the pointer was allocated with. (Because similar to
|
||
/// alignment, [`dealloc`] must be called with the same layout `size`.)
|
||
/// * `length` needs to be less than or equal to `capacity`.
|
||
/// * The first `length` values must be properly initialized values of type `T`.
|
||
/// * `capacity` needs to [*fit*] the layout size that the pointer was allocated with.
|
||
/// * The allocated size in bytes must be no larger than `isize::MAX`.
|
||
/// See the safety documentation of [`pointer::offset`].
|
||
///
|
||
/// These requirements are always upheld by any `ptr` that has been allocated
|
||
/// via `Vec<T, A>`. Other allocation sources are allowed if the invariants are
|
||
/// upheld.
|
||
///
|
||
/// 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`]: crate::string::String
|
||
/// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc
|
||
/// [*currently allocated*]: crate::alloc::Allocator#currently-allocated-memory
|
||
/// [*fit*]: crate::alloc::Allocator#memory-fitting
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// use std::ptr;
|
||
/// use std::mem;
|
||
///
|
||
/// let mut v = Vec::with_capacity_in(3, System);
|
||
/// v.push(1);
|
||
/// v.push(2);
|
||
/// v.push(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();
|
||
/// let alloc = v.allocator();
|
||
///
|
||
/// unsafe {
|
||
/// // Overwrite memory with 4, 5, 6
|
||
/// for i in 0..len {
|
||
/// ptr::write(p.add(i), 4 + i);
|
||
/// }
|
||
///
|
||
/// // Put everything back together into a Vec
|
||
/// let rebuilt = Vec::from_raw_parts_in(p, len, cap, alloc.clone());
|
||
/// assert_eq!(rebuilt, [4, 5, 6]);
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// Using memory that was allocated elsewhere:
|
||
///
|
||
/// ```rust
|
||
/// use std::alloc::{alloc, Layout};
|
||
///
|
||
/// fn main() {
|
||
/// let layout = Layout::array::<u32>(16).expect("overflow cannot happen");
|
||
/// let vec = unsafe {
|
||
/// let mem = alloc(layout).cast::<u32>();
|
||
/// if mem.is_null() {
|
||
/// return;
|
||
/// }
|
||
///
|
||
/// mem.write(1_000_000);
|
||
///
|
||
/// Vec::from_raw_parts(mem, 1, 16)
|
||
/// };
|
||
///
|
||
/// assert_eq!(vec, &[1_000_000]);
|
||
/// assert_eq!(vec.capacity(), 16);
|
||
/// }
|
||
/// ```
|
||
#[inline]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
pub unsafe fn from_raw_parts_in(ptr: *mut T, length: usize, capacity: usize, alloc: A) -> Self {
|
||
unsafe { Vec { buf: RawVec::from_raw_parts_in(ptr, capacity, alloc), len: length } }
|
||
}
|
||
|
||
/// 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`]: Vec::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())
|
||
}
|
||
|
||
/// Decomposes a `Vec<T>` into its raw components.
|
||
///
|
||
/// Returns the raw pointer to the underlying data, the length of the vector (in elements),
|
||
/// the allocated capacity of the data (in elements), and the allocator. These are the same
|
||
/// arguments in the same order as the arguments to [`from_raw_parts_in`].
|
||
///
|
||
/// 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_in`] function, allowing
|
||
/// the destructor to perform the cleanup.
|
||
///
|
||
/// [`from_raw_parts_in`]: Vec::from_raw_parts_in
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(allocator_api, vec_into_raw_parts)]
|
||
///
|
||
/// use std::alloc::System;
|
||
///
|
||
/// let mut v: Vec<i32, System> = Vec::new_in(System);
|
||
/// v.push(-1);
|
||
/// v.push(0);
|
||
/// v.push(1);
|
||
///
|
||
/// let (ptr, len, cap, alloc) = v.into_raw_parts_with_alloc();
|
||
///
|
||
/// 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_in(ptr, len, cap, alloc)
|
||
/// };
|
||
/// assert_eq!(rebuilt, [4294967295, 0, 1]);
|
||
/// ```
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
// #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")]
|
||
pub fn into_raw_parts_with_alloc(self) -> (*mut T, usize, usize, A) {
|
||
let mut me = ManuallyDrop::new(self);
|
||
let len = me.len();
|
||
let capacity = me.capacity();
|
||
let ptr = me.as_mut_ptr();
|
||
let alloc = unsafe { ptr::read(me.allocator()) };
|
||
(ptr, len, capacity, alloc)
|
||
}
|
||
|
||
/// Returns the total number of elements the vector can hold without
|
||
/// reallocating.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut vec: Vec<i32> = Vec::with_capacity(10);
|
||
/// vec.push(42);
|
||
/// 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
|
||
/// speculatively 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);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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 at least `additional` more elements to
|
||
/// be inserted in the given `Vec<T>`. Unlike [`reserve`], this will not
|
||
/// deliberately over-allocate to speculatively avoid frequent allocations.
|
||
/// 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.
|
||
///
|
||
/// [`reserve`]: Vec::reserve
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the new capacity exceeds `isize::MAX` bytes.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut vec = vec![1];
|
||
/// vec.reserve_exact(10);
|
||
/// assert!(vec.capacity() >= 11);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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 speculatively avoid
|
||
/// frequent reallocations. After calling `try_reserve`, capacity will be
|
||
/// greater than or equal to `self.len() + additional` if it returns
|
||
/// `Ok(())`. Does nothing if capacity is already sufficient. This method
|
||
/// preserves the contents even if an error occurs.
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If the capacity overflows, or the allocator reports a failure, then an error
|
||
/// is returned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// 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?");
|
||
/// ```
|
||
#[stable(feature = "try_reserve", since = "1.57.0")]
|
||
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
|
||
self.buf.try_reserve(self.len, additional)
|
||
}
|
||
|
||
/// Tries to reserve the minimum capacity for at least `additional`
|
||
/// elements to be inserted in the given `Vec<T>`. Unlike [`try_reserve`],
|
||
/// this will not deliberately over-allocate to speculatively avoid frequent
|
||
/// allocations. After calling `try_reserve_exact`, capacity will be greater
|
||
/// than or equal to `self.len() + additional` if it returns `Ok(())`.
|
||
/// 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 [`try_reserve`] if future insertions are expected.
|
||
///
|
||
/// [`try_reserve`]: Vec::try_reserve
|
||
///
|
||
/// # Errors
|
||
///
|
||
/// If the capacity overflows, or the allocator reports a failure, then an error
|
||
/// is returned.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// 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_exact(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?");
|
||
/// ```
|
||
#[stable(feature = "try_reserve", since = "1.57.0")]
|
||
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]);
|
||
/// assert_eq!(vec.capacity(), 10);
|
||
/// vec.shrink_to_fit();
|
||
/// assert!(vec.capacity() >= 3);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn shrink_to_fit(&mut self) {
|
||
// The capacity is never less than the length, and there's nothing to do when
|
||
// they are equal, so we can avoid the panic case in `RawVec::shrink_to_fit`
|
||
// by only calling it with a greater capacity.
|
||
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.
|
||
///
|
||
/// If the current capacity is less than the lower limit, this is a no-op.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut vec = Vec::with_capacity(10);
|
||
/// vec.extend([1, 2, 3]);
|
||
/// assert_eq!(vec.capacity(), 10);
|
||
/// vec.shrink_to(4);
|
||
/// assert!(vec.capacity() >= 4);
|
||
/// vec.shrink_to(0);
|
||
/// assert!(vec.capacity() >= 3);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "shrink_to", since = "1.56.0")]
|
||
pub fn shrink_to(&mut self, min_capacity: usize) {
|
||
if self.capacity() > min_capacity {
|
||
self.buf.shrink_to_fit(cmp::max(self.len, min_capacity));
|
||
}
|
||
}
|
||
|
||
/// Converts the vector into [`Box<[T]>`][owned slice].
|
||
///
|
||
/// If the vector has excess capacity, its items will be moved into a
|
||
/// newly-allocated buffer with exactly the right capacity.
|
||
///
|
||
/// [owned slice]: Box
|
||
///
|
||
/// # 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]);
|
||
///
|
||
/// assert_eq!(vec.capacity(), 10);
|
||
/// let slice = vec.into_boxed_slice();
|
||
/// assert_eq!(slice.into_vec().capacity(), 3);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn into_boxed_slice(mut self) -> Box<[T], A> {
|
||
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`]: Vec::clear
|
||
/// [`drain`]: Vec::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 {
|
||
// Note: It's intentional that this is `>` and not `>=`.
|
||
// Changing it to `>=` has negative performance
|
||
// implications in some cases. See #78884 for more.
|
||
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, or a dangling raw pointer
|
||
/// valid for zero sized reads if the vector didn't allocate.
|
||
///
|
||
/// 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`]: Vec::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, or a dangling
|
||
/// raw pointer valid for zero sized reads if the vector didn't allocate.
|
||
///
|
||
/// 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
|
||
}
|
||
|
||
/// Returns a reference to the underlying allocator.
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[inline]
|
||
pub fn allocator(&self) -> &A {
|
||
self.buf.allocator()
|
||
}
|
||
|
||
/// 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`]: Vec::truncate
|
||
/// [`resize`]: Vec::resize
|
||
/// [`extend`]: Extend::extend
|
||
/// [`clear`]: Vec::clear
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// - `new_len` must be less than or equal to [`capacity()`].
|
||
/// - The elements at `old_len..new_len` must be initialized.
|
||
///
|
||
/// [`capacity()`]: Vec::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).
|
||
/// If you need to preserve the element order, use [`remove`] instead.
|
||
///
|
||
/// [`remove`]: Vec::remove
|
||
///
|
||
/// # 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 {index}) should be < len (is {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 value = ptr::read(self.as_ptr().add(index));
|
||
let base_ptr = self.as_mut_ptr();
|
||
ptr::copy(base_ptr.add(len - 1), base_ptr.add(index), 1);
|
||
self.set_len(len - 1);
|
||
value
|
||
}
|
||
}
|
||
|
||
/// 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]);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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 {index}) should be <= len (is {len})");
|
||
}
|
||
|
||
let len = self.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);
|
||
if index < len {
|
||
// Shift everything over to make space. (Duplicating the
|
||
// `index`th element into two consecutive places.)
|
||
ptr::copy(p, p.add(1), len - index);
|
||
} else if index == len {
|
||
// No elements need shifting.
|
||
} else {
|
||
assert_failed(index, len);
|
||
}
|
||
// 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.
|
||
///
|
||
/// Note: Because this shifts over the remaining elements, it has a
|
||
/// worst-case performance of *O*(*n*). If you don't need the order of elements
|
||
/// to be preserved, use [`swap_remove`] instead. If you'd like to remove
|
||
/// elements from the beginning of the `Vec`, consider using
|
||
/// [`VecDeque::pop_front`] instead.
|
||
///
|
||
/// [`swap_remove`]: Vec::swap_remove
|
||
/// [`VecDeque::pop_front`]: crate::collections::VecDeque::pop_front
|
||
///
|
||
/// # 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")]
|
||
#[track_caller]
|
||
pub fn remove(&mut self, index: usize) -> T {
|
||
#[cold]
|
||
#[inline(never)]
|
||
#[track_caller]
|
||
fn assert_failed(index: usize, len: usize) -> ! {
|
||
panic!("removal index (is {index}) should be < len (is {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.add(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` for which `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]);
|
||
/// ```
|
||
///
|
||
/// Because the elements are visited exactly once in the original order,
|
||
/// external state may be used to decide which elements to keep.
|
||
///
|
||
/// ```
|
||
/// let mut vec = vec![1, 2, 3, 4, 5];
|
||
/// let keep = [false, true, true, false, true];
|
||
/// let mut iter = keep.iter();
|
||
/// vec.retain(|_| *iter.next().unwrap());
|
||
/// 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,
|
||
{
|
||
self.retain_mut(|elem| f(elem));
|
||
}
|
||
|
||
/// Retains only the elements specified by the predicate, passing a mutable reference to it.
|
||
///
|
||
/// In other words, remove all elements `e` such that `f(&mut 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_mut(|x| if *x <= 3 {
|
||
/// *x += 1;
|
||
/// true
|
||
/// } else {
|
||
/// false
|
||
/// });
|
||
/// assert_eq!(vec, [2, 3, 4]);
|
||
/// ```
|
||
#[stable(feature = "vec_retain_mut", since = "1.61.0")]
|
||
pub fn retain_mut<F>(&mut self, mut f: F)
|
||
where
|
||
F: FnMut(&mut T) -> bool,
|
||
{
|
||
let original_len = self.len();
|
||
// Avoid double drop if the drop guard is not executed,
|
||
// since we may make some holes during the process.
|
||
unsafe { self.set_len(0) };
|
||
|
||
// Vec: [Kept, Kept, Hole, Hole, Hole, Hole, Unchecked, Unchecked]
|
||
// |<- processed len ->| ^- next to check
|
||
// |<- deleted cnt ->|
|
||
// |<- original_len ->|
|
||
// Kept: Elements which predicate returns true on.
|
||
// Hole: Moved or dropped element slot.
|
||
// Unchecked: Unchecked valid elements.
|
||
//
|
||
// This drop guard will be invoked when predicate or `drop` of element panicked.
|
||
// It shifts unchecked elements to cover holes and `set_len` to the correct length.
|
||
// In cases when predicate and `drop` never panick, it will be optimized out.
|
||
struct BackshiftOnDrop<'a, T, A: Allocator> {
|
||
v: &'a mut Vec<T, A>,
|
||
processed_len: usize,
|
||
deleted_cnt: usize,
|
||
original_len: usize,
|
||
}
|
||
|
||
impl<T, A: Allocator> Drop for BackshiftOnDrop<'_, T, A> {
|
||
fn drop(&mut self) {
|
||
if self.deleted_cnt > 0 {
|
||
// SAFETY: Trailing unchecked items must be valid since we never touch them.
|
||
unsafe {
|
||
ptr::copy(
|
||
self.v.as_ptr().add(self.processed_len),
|
||
self.v.as_mut_ptr().add(self.processed_len - self.deleted_cnt),
|
||
self.original_len - self.processed_len,
|
||
);
|
||
}
|
||
}
|
||
// SAFETY: After filling holes, all items are in contiguous memory.
|
||
unsafe {
|
||
self.v.set_len(self.original_len - self.deleted_cnt);
|
||
}
|
||
}
|
||
}
|
||
|
||
let mut g = BackshiftOnDrop { v: self, processed_len: 0, deleted_cnt: 0, original_len };
|
||
|
||
fn process_loop<F, T, A: Allocator, const DELETED: bool>(
|
||
original_len: usize,
|
||
f: &mut F,
|
||
g: &mut BackshiftOnDrop<'_, T, A>,
|
||
) where
|
||
F: FnMut(&mut T) -> bool,
|
||
{
|
||
while g.processed_len != original_len {
|
||
// SAFETY: Unchecked element must be valid.
|
||
let cur = unsafe { &mut *g.v.as_mut_ptr().add(g.processed_len) };
|
||
if !f(cur) {
|
||
// Advance early to avoid double drop if `drop_in_place` panicked.
|
||
g.processed_len += 1;
|
||
g.deleted_cnt += 1;
|
||
// SAFETY: We never touch this element again after dropped.
|
||
unsafe { ptr::drop_in_place(cur) };
|
||
// We already advanced the counter.
|
||
if DELETED {
|
||
continue;
|
||
} else {
|
||
break;
|
||
}
|
||
}
|
||
if DELETED {
|
||
// SAFETY: `deleted_cnt` > 0, so the hole slot must not overlap with current element.
|
||
// We use copy for move, and never touch this element again.
|
||
unsafe {
|
||
let hole_slot = g.v.as_mut_ptr().add(g.processed_len - g.deleted_cnt);
|
||
ptr::copy_nonoverlapping(cur, hole_slot, 1);
|
||
}
|
||
}
|
||
g.processed_len += 1;
|
||
}
|
||
}
|
||
|
||
// Stage 1: Nothing was deleted.
|
||
process_loop::<F, T, A, false>(original_len, &mut f, &mut g);
|
||
|
||
// Stage 2: Some elements were deleted.
|
||
process_loop::<F, T, A, true>(original_len, &mut f, &mut g);
|
||
|
||
// All item are processed. This can be optimized to `set_len` by LLVM.
|
||
drop(g);
|
||
}
|
||
|
||
/// 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, mut same_bucket: F)
|
||
where
|
||
F: FnMut(&mut T, &mut T) -> bool,
|
||
{
|
||
let len = self.len();
|
||
if len <= 1 {
|
||
return;
|
||
}
|
||
|
||
/* INVARIANT: vec.len() > read >= write > write-1 >= 0 */
|
||
struct FillGapOnDrop<'a, T, A: core::alloc::Allocator> {
|
||
/* Offset of the element we want to check if it is duplicate */
|
||
read: usize,
|
||
|
||
/* Offset of the place where we want to place the non-duplicate
|
||
* when we find it. */
|
||
write: usize,
|
||
|
||
/* The Vec that would need correction if `same_bucket` panicked */
|
||
vec: &'a mut Vec<T, A>,
|
||
}
|
||
|
||
impl<'a, T, A: core::alloc::Allocator> Drop for FillGapOnDrop<'a, T, A> {
|
||
fn drop(&mut self) {
|
||
/* This code gets executed when `same_bucket` panics */
|
||
|
||
/* SAFETY: invariant guarantees that `read - write`
|
||
* and `len - read` never overflow and that the copy is always
|
||
* in-bounds. */
|
||
unsafe {
|
||
let ptr = self.vec.as_mut_ptr();
|
||
let len = self.vec.len();
|
||
|
||
/* How many items were left when `same_bucket` panicked.
|
||
* Basically vec[read..].len() */
|
||
let items_left = len.wrapping_sub(self.read);
|
||
|
||
/* Pointer to first item in vec[write..write+items_left] slice */
|
||
let dropped_ptr = ptr.add(self.write);
|
||
/* Pointer to first item in vec[read..] slice */
|
||
let valid_ptr = ptr.add(self.read);
|
||
|
||
/* Copy `vec[read..]` to `vec[write..write+items_left]`.
|
||
* The slices can overlap, so `copy_nonoverlapping` cannot be used */
|
||
ptr::copy(valid_ptr, dropped_ptr, items_left);
|
||
|
||
/* How many items have been already dropped
|
||
* Basically vec[read..write].len() */
|
||
let dropped = self.read.wrapping_sub(self.write);
|
||
|
||
self.vec.set_len(len - dropped);
|
||
}
|
||
}
|
||
}
|
||
|
||
let mut gap = FillGapOnDrop { read: 1, write: 1, vec: self };
|
||
let ptr = gap.vec.as_mut_ptr();
|
||
|
||
/* Drop items while going through Vec, it should be more efficient than
|
||
* doing slice partition_dedup + truncate */
|
||
|
||
/* SAFETY: Because of the invariant, read_ptr, prev_ptr and write_ptr
|
||
* are always in-bounds and read_ptr never aliases prev_ptr */
|
||
unsafe {
|
||
while gap.read < len {
|
||
let read_ptr = ptr.add(gap.read);
|
||
let prev_ptr = ptr.add(gap.write.wrapping_sub(1));
|
||
|
||
if same_bucket(&mut *read_ptr, &mut *prev_ptr) {
|
||
// Increase `gap.read` now since the drop may panic.
|
||
gap.read += 1;
|
||
/* We have found duplicate, drop it in-place */
|
||
ptr::drop_in_place(read_ptr);
|
||
} else {
|
||
let write_ptr = ptr.add(gap.write);
|
||
|
||
/* Because `read_ptr` can be equal to `write_ptr`, we either
|
||
* have to use `copy` or conditional `copy_nonoverlapping`.
|
||
* Looks like the first option is faster. */
|
||
ptr::copy(read_ptr, write_ptr, 1);
|
||
|
||
/* We have filled that place, so go further */
|
||
gap.write += 1;
|
||
gap.read += 1;
|
||
}
|
||
}
|
||
|
||
/* Technically we could let `gap` clean up with its Drop, but
|
||
* when `same_bucket` is guaranteed to not panic, this bloats a little
|
||
* the codegen, so we just do it manually */
|
||
gap.vec.set_len(gap.write);
|
||
mem::forget(gap);
|
||
}
|
||
}
|
||
|
||
/// 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]);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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.buf.reserve_for_push(self.len);
|
||
}
|
||
unsafe {
|
||
let end = self.as_mut_ptr().add(self.len);
|
||
ptr::write(end, value);
|
||
self.len += 1;
|
||
}
|
||
}
|
||
|
||
/// Tries to append an element to the back of a collection.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut vec = vec![1, 2];
|
||
/// vec.try_push(3).unwrap();
|
||
/// assert_eq!(vec, [1, 2, 3]);
|
||
/// ```
|
||
#[inline]
|
||
#[stable(feature = "kernel", since = "1.0.0")]
|
||
pub fn try_push(&mut self, value: T) -> Result<(), TryReserveError> {
|
||
if self.len == self.buf.capacity() {
|
||
self.buf.try_reserve_for_push(self.len)?;
|
||
}
|
||
unsafe {
|
||
let end = self.as_mut_ptr().add(self.len);
|
||
ptr::write(end, value);
|
||
self.len += 1;
|
||
}
|
||
Ok(())
|
||
}
|
||
|
||
/// Appends an element if there is sufficient spare capacity, otherwise an error is returned
|
||
/// with the element.
|
||
///
|
||
/// Unlike [`push`] this method will not reallocate when there's insufficient capacity.
|
||
/// The caller should use [`reserve`] or [`try_reserve`] to ensure that there is enough capacity.
|
||
///
|
||
/// [`push`]: Vec::push
|
||
/// [`reserve`]: Vec::reserve
|
||
/// [`try_reserve`]: Vec::try_reserve
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// A manual, panic-free alternative to [`FromIterator`]:
|
||
///
|
||
/// ```
|
||
/// #![feature(vec_push_within_capacity)]
|
||
///
|
||
/// use std::collections::TryReserveError;
|
||
/// fn from_iter_fallible<T>(iter: impl Iterator<Item=T>) -> Result<Vec<T>, TryReserveError> {
|
||
/// let mut vec = Vec::new();
|
||
/// for value in iter {
|
||
/// if let Err(value) = vec.push_within_capacity(value) {
|
||
/// vec.try_reserve(1)?;
|
||
/// // this cannot fail, the previous line either returned or added at least 1 free slot
|
||
/// let _ = vec.push_within_capacity(value);
|
||
/// }
|
||
/// }
|
||
/// Ok(vec)
|
||
/// }
|
||
/// assert_eq!(from_iter_fallible(0..100), Ok(Vec::from_iter(0..100)));
|
||
/// ```
|
||
#[inline]
|
||
#[unstable(feature = "vec_push_within_capacity", issue = "100486")]
|
||
pub fn push_within_capacity(&mut self, value: T) -> Result<(), T> {
|
||
if self.len == self.buf.capacity() {
|
||
return Err(value);
|
||
}
|
||
unsafe {
|
||
let end = self.as_mut_ptr().add(self.len);
|
||
ptr::write(end, value);
|
||
self.len += 1;
|
||
}
|
||
Ok(())
|
||
}
|
||
|
||
/// Removes the last element from a vector and returns it, or [`None`] if it
|
||
/// is empty.
|
||
///
|
||
/// If you'd like to pop the first element, consider using
|
||
/// [`VecDeque::pop_front`] instead.
|
||
///
|
||
/// [`VecDeque::pop_front`]: crate::collections::VecDeque::pop_front
|
||
///
|
||
/// # 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 new capacity exceeds `isize::MAX` bytes.
|
||
///
|
||
/// # 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, []);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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.
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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;
|
||
}
|
||
|
||
/// Tries to append elements to `self` from other buffer.
|
||
#[inline]
|
||
unsafe fn try_append_elements(&mut self, other: *const [T]) -> Result<(), TryReserveError> {
|
||
let count = unsafe { (*other).len() };
|
||
self.try_reserve(count)?;
|
||
let len = self.len();
|
||
unsafe { ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count) };
|
||
self.len += count;
|
||
Ok(())
|
||
}
|
||
|
||
/// Removes the specified range from the vector in bulk, returning all
|
||
/// removed elements as an iterator. If the iterator is dropped before
|
||
/// being fully consumed, it drops the remaining removed elements.
|
||
///
|
||
/// The returned iterator keeps a mutable borrow on the vector to optimize
|
||
/// its implementation.
|
||
///
|
||
/// # 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.
|
||
///
|
||
/// # Leaking
|
||
///
|
||
/// If the returned iterator goes out of scope without being dropped (due to
|
||
/// [`mem::forget`], for example), the vector may have lost and leaked
|
||
/// elements arbitrarily, including elements outside the range.
|
||
///
|
||
/// # 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, like `clear()` does
|
||
/// v.drain(..);
|
||
/// assert_eq!(v, &[]);
|
||
/// ```
|
||
#[stable(feature = "drain", since = "1.6.0")]
|
||
pub fn drain<R>(&mut self, range: R) -> Drain<'_, T, A>
|
||
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 Range { start, end } = slice::range(range, ..len);
|
||
|
||
unsafe {
|
||
// set self.vec length's to start, to be safe in case Drain is leaked
|
||
self.set_len(start);
|
||
let range_slice = slice::from_raw_parts(self.as_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) {
|
||
let elems: *mut [T] = self.as_mut_slice();
|
||
|
||
// SAFETY:
|
||
// - `elems` comes directly from `as_mut_slice` and is therefore valid.
|
||
// - Setting `self.len` before calling `drop_in_place` means that,
|
||
// if an element's `Drop` impl panics, the vector's `Drop` impl will
|
||
// do nothing (leaking the rest of the elements) instead of dropping
|
||
// some twice.
|
||
unsafe {
|
||
self.len = 0;
|
||
ptr::drop_in_place(elems);
|
||
}
|
||
}
|
||
|
||
/// 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]);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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
|
||
where
|
||
A: Clone,
|
||
{
|
||
#[cold]
|
||
#[inline(never)]
|
||
fn assert_failed(at: usize, len: usize) -> ! {
|
||
panic!("`at` split index (is {at}) should be <= len (is {len})");
|
||
}
|
||
|
||
if at > self.len() {
|
||
assert_failed(at, self.len());
|
||
}
|
||
|
||
if at == 0 {
|
||
// the new vector can take over the original buffer and avoid the copy
|
||
return mem::replace(
|
||
self,
|
||
Vec::with_capacity_in(self.capacity(), self.allocator().clone()),
|
||
);
|
||
}
|
||
|
||
let other_len = self.len - at;
|
||
let mut other = Vec::with_capacity_in(other_len, self.allocator().clone());
|
||
|
||
// 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 [`Vec::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]);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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_trusted(iter::repeat_with(f).take(new_len - len));
|
||
} 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`.
|
||
///
|
||
/// As of Rust 1.57, this method does not reallocate or shrink the `Vec`,
|
||
/// so the leaked allocation may include unused capacity that is not part
|
||
/// of the returned slice.
|
||
///
|
||
/// 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:
|
||
///
|
||
/// ```
|
||
/// let x = vec![1, 2, 3];
|
||
/// let static_ref: &'static mut [usize] = x.leak();
|
||
/// static_ref[0] += 1;
|
||
/// assert_eq!(static_ref, &[2, 2, 3]);
|
||
/// ```
|
||
#[stable(feature = "vec_leak", since = "1.47.0")]
|
||
#[inline]
|
||
pub fn leak<'a>(self) -> &'a mut [T]
|
||
where
|
||
A: 'a,
|
||
{
|
||
let mut me = ManuallyDrop::new(self);
|
||
unsafe { slice::from_raw_parts_mut(me.as_mut_ptr(), me.len) }
|
||
}
|
||
|
||
/// Returns the remaining spare capacity of the vector as a slice of
|
||
/// `MaybeUninit<T>`.
|
||
///
|
||
/// The returned slice can be used to fill the vector with data (e.g. by
|
||
/// reading from a file) before marking the data as initialized using the
|
||
/// [`set_len`] method.
|
||
///
|
||
/// [`set_len`]: Vec::set_len
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// // Allocate vector big enough for 10 elements.
|
||
/// let mut v = Vec::with_capacity(10);
|
||
///
|
||
/// // Fill in the first 3 elements.
|
||
/// let uninit = v.spare_capacity_mut();
|
||
/// uninit[0].write(0);
|
||
/// uninit[1].write(1);
|
||
/// uninit[2].write(2);
|
||
///
|
||
/// // Mark the first 3 elements of the vector as being initialized.
|
||
/// unsafe {
|
||
/// v.set_len(3);
|
||
/// }
|
||
///
|
||
/// assert_eq!(&v, &[0, 1, 2]);
|
||
/// ```
|
||
#[stable(feature = "vec_spare_capacity", since = "1.60.0")]
|
||
#[inline]
|
||
pub fn spare_capacity_mut(&mut self) -> &mut [MaybeUninit<T>] {
|
||
// Note:
|
||
// This method is not implemented in terms of `split_at_spare_mut`,
|
||
// to prevent invalidation of pointers to the buffer.
|
||
unsafe {
|
||
slice::from_raw_parts_mut(
|
||
self.as_mut_ptr().add(self.len) as *mut MaybeUninit<T>,
|
||
self.buf.capacity() - self.len,
|
||
)
|
||
}
|
||
}
|
||
|
||
/// Returns vector content as a slice of `T`, along with the remaining spare
|
||
/// capacity of the vector as a slice of `MaybeUninit<T>`.
|
||
///
|
||
/// The returned spare capacity slice can be used to fill the vector with data
|
||
/// (e.g. by reading from a file) before marking the data as initialized using
|
||
/// the [`set_len`] method.
|
||
///
|
||
/// [`set_len`]: Vec::set_len
|
||
///
|
||
/// Note that this is a low-level API, which should be used with care for
|
||
/// optimization purposes. If you need to append data to a `Vec`
|
||
/// you can use [`push`], [`extend`], [`extend_from_slice`],
|
||
/// [`extend_from_within`], [`insert`], [`append`], [`resize`] or
|
||
/// [`resize_with`], depending on your exact needs.
|
||
///
|
||
/// [`push`]: Vec::push
|
||
/// [`extend`]: Vec::extend
|
||
/// [`extend_from_slice`]: Vec::extend_from_slice
|
||
/// [`extend_from_within`]: Vec::extend_from_within
|
||
/// [`insert`]: Vec::insert
|
||
/// [`append`]: Vec::append
|
||
/// [`resize`]: Vec::resize
|
||
/// [`resize_with`]: Vec::resize_with
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(vec_split_at_spare)]
|
||
///
|
||
/// let mut v = vec![1, 1, 2];
|
||
///
|
||
/// // Reserve additional space big enough for 10 elements.
|
||
/// v.reserve(10);
|
||
///
|
||
/// let (init, uninit) = v.split_at_spare_mut();
|
||
/// let sum = init.iter().copied().sum::<u32>();
|
||
///
|
||
/// // Fill in the next 4 elements.
|
||
/// uninit[0].write(sum);
|
||
/// uninit[1].write(sum * 2);
|
||
/// uninit[2].write(sum * 3);
|
||
/// uninit[3].write(sum * 4);
|
||
///
|
||
/// // Mark the 4 elements of the vector as being initialized.
|
||
/// unsafe {
|
||
/// let len = v.len();
|
||
/// v.set_len(len + 4);
|
||
/// }
|
||
///
|
||
/// assert_eq!(&v, &[1, 1, 2, 4, 8, 12, 16]);
|
||
/// ```
|
||
#[unstable(feature = "vec_split_at_spare", issue = "81944")]
|
||
#[inline]
|
||
pub fn split_at_spare_mut(&mut self) -> (&mut [T], &mut [MaybeUninit<T>]) {
|
||
// SAFETY:
|
||
// - len is ignored and so never changed
|
||
let (init, spare, _) = unsafe { self.split_at_spare_mut_with_len() };
|
||
(init, spare)
|
||
}
|
||
|
||
/// Safety: changing returned .2 (&mut usize) is considered the same as calling `.set_len(_)`.
|
||
///
|
||
/// This method provides unique access to all vec parts at once in `extend_from_within`.
|
||
unsafe fn split_at_spare_mut_with_len(
|
||
&mut self,
|
||
) -> (&mut [T], &mut [MaybeUninit<T>], &mut usize) {
|
||
let ptr = self.as_mut_ptr();
|
||
// SAFETY:
|
||
// - `ptr` is guaranteed to be valid for `self.len` elements
|
||
// - but the allocation extends out to `self.buf.capacity()` elements, possibly
|
||
// uninitialized
|
||
let spare_ptr = unsafe { ptr.add(self.len) };
|
||
let spare_ptr = spare_ptr.cast::<MaybeUninit<T>>();
|
||
let spare_len = self.buf.capacity() - self.len;
|
||
|
||
// SAFETY:
|
||
// - `ptr` is guaranteed to be valid for `self.len` elements
|
||
// - `spare_ptr` is pointing one element past the buffer, so it doesn't overlap with `initialized`
|
||
unsafe {
|
||
let initialized = slice::from_raw_parts_mut(ptr, self.len);
|
||
let spare = slice::from_raw_parts_mut(spare_ptr, spare_len);
|
||
|
||
(initialized, spare, &mut self.len)
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T: Clone, A: Allocator> Vec<T, A> {
|
||
/// 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 [`Vec::resize_with`].
|
||
/// If you only need to resize to a smaller size, use [`Vec::truncate`].
|
||
///
|
||
/// # 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]);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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);
|
||
}
|
||
}
|
||
|
||
/// Tries to resize 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 [`Vec::resize_with`].
|
||
/// If you only need to resize to a smaller size, use [`Vec::truncate`].
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let mut vec = vec!["hello"];
|
||
/// vec.try_resize(3, "world").unwrap();
|
||
/// assert_eq!(vec, ["hello", "world", "world"]);
|
||
///
|
||
/// let mut vec = vec![1, 2, 3, 4];
|
||
/// vec.try_resize(2, 0).unwrap();
|
||
/// assert_eq!(vec, [1, 2]);
|
||
///
|
||
/// let mut vec = vec![42];
|
||
/// let result = vec.try_resize(usize::MAX, 0);
|
||
/// assert!(result.is_err());
|
||
/// ```
|
||
#[stable(feature = "kernel", since = "1.0.0")]
|
||
pub fn try_resize(&mut self, new_len: usize, value: T) -> Result<(), TryReserveError> {
|
||
let len = self.len();
|
||
|
||
if new_len > len {
|
||
self.try_extend_with(new_len - len, ExtendElement(value))
|
||
} else {
|
||
self.truncate(new_len);
|
||
Ok(())
|
||
}
|
||
}
|
||
|
||
/// 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` slice 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`]: Vec::extend
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
|
||
pub fn extend_from_slice(&mut self, other: &[T]) {
|
||
self.spec_extend(other.iter())
|
||
}
|
||
|
||
/// Tries to clone and append 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` slice 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.try_extend_from_slice(&[2, 3, 4]).unwrap();
|
||
/// assert_eq!(vec, [1, 2, 3, 4]);
|
||
/// ```
|
||
///
|
||
/// [`extend`]: Vec::extend
|
||
#[stable(feature = "kernel", since = "1.0.0")]
|
||
pub fn try_extend_from_slice(&mut self, other: &[T]) -> Result<(), TryReserveError> {
|
||
self.try_spec_extend(other.iter())
|
||
}
|
||
|
||
/// Copies elements from `src` range to the end of the vector.
|
||
///
|
||
/// # 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 vec = vec![0, 1, 2, 3, 4];
|
||
///
|
||
/// vec.extend_from_within(2..);
|
||
/// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4]);
|
||
///
|
||
/// vec.extend_from_within(..2);
|
||
/// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1]);
|
||
///
|
||
/// vec.extend_from_within(4..8);
|
||
/// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1, 4, 2, 3, 4]);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "vec_extend_from_within", since = "1.53.0")]
|
||
pub fn extend_from_within<R>(&mut self, src: R)
|
||
where
|
||
R: RangeBounds<usize>,
|
||
{
|
||
let range = slice::range(src, ..self.len());
|
||
self.reserve(range.len());
|
||
|
||
// SAFETY:
|
||
// - `slice::range` guarantees that the given range is valid for indexing self
|
||
unsafe {
|
||
self.spec_extend_from_within(range);
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator, const N: usize> Vec<[T; N], A> {
|
||
/// Takes a `Vec<[T; N]>` and flattens it into a `Vec<T>`.
|
||
///
|
||
/// # Panics
|
||
///
|
||
/// Panics if the length of the resulting vector would overflow a `usize`.
|
||
///
|
||
/// This is only possible when flattening a vector of arrays of zero-sized
|
||
/// types, and thus tends to be irrelevant in practice. If
|
||
/// `size_of::<T>() > 0`, this will never panic.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// #![feature(slice_flatten)]
|
||
///
|
||
/// let mut vec = vec![[1, 2, 3], [4, 5, 6], [7, 8, 9]];
|
||
/// assert_eq!(vec.pop(), Some([7, 8, 9]));
|
||
///
|
||
/// let mut flattened = vec.into_flattened();
|
||
/// assert_eq!(flattened.pop(), Some(6));
|
||
/// ```
|
||
#[unstable(feature = "slice_flatten", issue = "95629")]
|
||
pub fn into_flattened(self) -> Vec<T, A> {
|
||
let (ptr, len, cap, alloc) = self.into_raw_parts_with_alloc();
|
||
let (new_len, new_cap) = if T::IS_ZST {
|
||
(len.checked_mul(N).expect("vec len overflow"), usize::MAX)
|
||
} else {
|
||
// SAFETY:
|
||
// - `cap * N` cannot overflow because the allocation is already in
|
||
// the address space.
|
||
// - Each `[T; N]` has `N` valid elements, so there are `len * N`
|
||
// valid elements in the allocation.
|
||
unsafe { (len.unchecked_mul(N), cap.unchecked_mul(N)) }
|
||
};
|
||
// SAFETY:
|
||
// - `ptr` was allocated by `self`
|
||
// - `ptr` is well-aligned because `[T; N]` has the same alignment as `T`.
|
||
// - `new_cap` refers to the same sized allocation as `cap` because
|
||
// `new_cap * size_of::<T>()` == `cap * size_of::<[T; N]>()`
|
||
// - `len` <= `cap`, so `len * N` <= `cap * N`.
|
||
unsafe { Vec::<T, A>::from_raw_parts_in(ptr.cast(), new_len, new_cap, alloc) }
|
||
}
|
||
}
|
||
|
||
// 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
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator> Vec<T, A> {
|
||
#[cfg(not(no_global_oom_handling))]
|
||
/// 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
|
||
// might 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.add(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
|
||
}
|
||
}
|
||
|
||
/// Try to extend the vector by `n` values, using the given generator.
|
||
fn try_extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) -> Result<(), TryReserveError> {
|
||
self.try_reserve(n)?;
|
||
|
||
unsafe {
|
||
let mut ptr = self.as_mut_ptr().add(self.len());
|
||
// Use SetLenOnDrop to work around bug where compiler
|
||
// might 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.add(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
|
||
Ok(())
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T: PartialEq, A: Allocator> Vec<T, A> {
|
||
/// 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)
|
||
}
|
||
}
|
||
|
||
////////////////////////////////////////////////////////////////////////////////
|
||
// Internal methods and functions
|
||
////////////////////////////////////////////////////////////////////////////////
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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, Global)
|
||
}
|
||
|
||
#[doc(hidden)]
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
pub fn from_elem_in<T: Clone, A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> {
|
||
<T as SpecFromElem>::from_elem(elem, n, alloc)
|
||
}
|
||
|
||
trait ExtendFromWithinSpec {
|
||
/// # Safety
|
||
///
|
||
/// - `src` needs to be valid index
|
||
/// - `self.capacity() - self.len()` must be `>= src.len()`
|
||
unsafe fn spec_extend_from_within(&mut self, src: Range<usize>);
|
||
}
|
||
|
||
impl<T: Clone, A: Allocator> ExtendFromWithinSpec for Vec<T, A> {
|
||
default unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) {
|
||
// SAFETY:
|
||
// - len is increased only after initializing elements
|
||
let (this, spare, len) = unsafe { self.split_at_spare_mut_with_len() };
|
||
|
||
// SAFETY:
|
||
// - caller guarantees that src is a valid index
|
||
let to_clone = unsafe { this.get_unchecked(src) };
|
||
|
||
iter::zip(to_clone, spare)
|
||
.map(|(src, dst)| dst.write(src.clone()))
|
||
// Note:
|
||
// - Element was just initialized with `MaybeUninit::write`, so it's ok to increase len
|
||
// - len is increased after each element to prevent leaks (see issue #82533)
|
||
.for_each(|_| *len += 1);
|
||
}
|
||
}
|
||
|
||
impl<T: Copy, A: Allocator> ExtendFromWithinSpec for Vec<T, A> {
|
||
unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) {
|
||
let count = src.len();
|
||
{
|
||
let (init, spare) = self.split_at_spare_mut();
|
||
|
||
// SAFETY:
|
||
// - caller guarantees that `src` is a valid index
|
||
let source = unsafe { init.get_unchecked(src) };
|
||
|
||
// SAFETY:
|
||
// - Both pointers are created from unique slice references (`&mut [_]`)
|
||
// so they are valid and do not overlap.
|
||
// - Elements are :Copy so it's OK to copy them, without doing
|
||
// anything with the original values
|
||
// - `count` is equal to the len of `source`, so source is valid for
|
||
// `count` reads
|
||
// - `.reserve(count)` guarantees that `spare.len() >= count` so spare
|
||
// is valid for `count` writes
|
||
unsafe { ptr::copy_nonoverlapping(source.as_ptr(), spare.as_mut_ptr() as _, count) };
|
||
}
|
||
|
||
// SAFETY:
|
||
// - The elements were just initialized by `copy_nonoverlapping`
|
||
self.len += count;
|
||
}
|
||
}
|
||
|
||
////////////////////////////////////////////////////////////////////////////////
|
||
// Common trait implementations for Vec
|
||
////////////////////////////////////////////////////////////////////////////////
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T, A: Allocator> ops::Deref for Vec<T, A> {
|
||
type Target = [T];
|
||
|
||
#[inline]
|
||
fn deref(&self) -> &[T] {
|
||
unsafe { slice::from_raw_parts(self.as_ptr(), self.len) }
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T, A: Allocator> ops::DerefMut for Vec<T, A> {
|
||
#[inline]
|
||
fn deref_mut(&mut self) -> &mut [T] {
|
||
unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) }
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
trait SpecCloneFrom {
|
||
fn clone_from(this: &mut Self, other: &Self);
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl<T: Clone, A: Allocator> SpecCloneFrom for Vec<T, A> {
|
||
default fn clone_from(this: &mut Self, other: &Self) {
|
||
// drop anything that will not be overwritten
|
||
this.truncate(other.len());
|
||
|
||
// self.len <= other.len due to the truncate above, so the
|
||
// slices here are always in-bounds.
|
||
let (init, tail) = other.split_at(this.len());
|
||
|
||
// reuse the contained values' allocations/resources.
|
||
this.clone_from_slice(init);
|
||
this.extend_from_slice(tail);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
impl<T: Copy, A: Allocator> SpecCloneFrom for Vec<T, A> {
|
||
fn clone_from(this: &mut Self, other: &Self) {
|
||
this.clear();
|
||
this.extend_from_slice(other);
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
|
||
#[cfg(not(test))]
|
||
fn clone(&self) -> Self {
|
||
let alloc = self.allocator().clone();
|
||
<[T]>::to_vec_in(&**self, alloc)
|
||
}
|
||
|
||
// 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) -> Self {
|
||
let alloc = self.allocator().clone();
|
||
crate::slice::to_vec(&**self, alloc)
|
||
}
|
||
|
||
fn clone_from(&mut self, other: &Self) {
|
||
SpecCloneFrom::clone_from(self, other)
|
||
}
|
||
}
|
||
|
||
/// The hash of a vector is the same as that of the corresponding slice,
|
||
/// as required by the `core::borrow::Borrow` implementation.
|
||
///
|
||
/// ```
|
||
/// #![feature(build_hasher_simple_hash_one)]
|
||
/// use std::hash::BuildHasher;
|
||
///
|
||
/// let b = std::collections::hash_map::RandomState::new();
|
||
/// let v: Vec<u8> = vec![0xa8, 0x3c, 0x09];
|
||
/// let s: &[u8] = &[0xa8, 0x3c, 0x09];
|
||
/// assert_eq!(b.hash_one(v), b.hash_one(s));
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Hash, A: Allocator> Hash for Vec<T, A> {
|
||
#[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]>, A: Allocator> Index<I> for Vec<T, A> {
|
||
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]>, A: Allocator> IndexMut<I> for Vec<T, A> {
|
||
#[inline]
|
||
fn index_mut(&mut self, index: I) -> &mut Self::Output {
|
||
IndexMut::index_mut(&mut **self, index)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[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 SpecFromIter<T, I::IntoIter>>::from_iter(iter.into_iter())
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T, A: Allocator> IntoIterator for Vec<T, A> {
|
||
type Item = T;
|
||
type IntoIter = IntoIter<T, A>;
|
||
|
||
/// 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()];
|
||
/// let mut v_iter = v.into_iter();
|
||
///
|
||
/// let first_element: Option<String> = v_iter.next();
|
||
///
|
||
/// assert_eq!(first_element, Some("a".to_string()));
|
||
/// assert_eq!(v_iter.next(), Some("b".to_string()));
|
||
/// assert_eq!(v_iter.next(), None);
|
||
/// ```
|
||
#[inline]
|
||
fn into_iter(self) -> Self::IntoIter {
|
||
unsafe {
|
||
let mut me = ManuallyDrop::new(self);
|
||
let alloc = ManuallyDrop::new(ptr::read(me.allocator()));
|
||
let begin = me.as_mut_ptr();
|
||
let end = if T::IS_ZST {
|
||
begin.wrapping_byte_add(me.len())
|
||
} else {
|
||
begin.add(me.len()) as *const T
|
||
};
|
||
let cap = me.buf.capacity();
|
||
IntoIter {
|
||
buf: NonNull::new_unchecked(begin),
|
||
phantom: PhantomData,
|
||
cap,
|
||
alloc,
|
||
ptr: begin,
|
||
end,
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a, T, A: Allocator> IntoIterator for &'a Vec<T, A> {
|
||
type Item = &'a T;
|
||
type IntoIter = slice::Iter<'a, T>;
|
||
|
||
fn into_iter(self) -> Self::IntoIter {
|
||
self.iter()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<'a, T, A: Allocator> IntoIterator for &'a mut Vec<T, A> {
|
||
type Item = &'a mut T;
|
||
type IntoIter = slice::IterMut<'a, T>;
|
||
|
||
fn into_iter(self) -> Self::IntoIter {
|
||
self.iter_mut()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T, A: Allocator> Extend<T> for Vec<T, A> {
|
||
#[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);
|
||
}
|
||
}
|
||
|
||
impl<T, A: Allocator> Vec<T, A> {
|
||
// leaf method to which various SpecFrom/SpecExtend implementations delegate when
|
||
// they have no further optimizations to apply
|
||
#[cfg(not(no_global_oom_handling))]
|
||
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);
|
||
// Since next() executes user code which can panic we have to bump the length
|
||
// after each step.
|
||
// NB can't overflow since we would have had to alloc the address space
|
||
self.set_len(len + 1);
|
||
}
|
||
}
|
||
}
|
||
|
||
// leaf method to which various SpecFrom/SpecExtend implementations delegate when
|
||
// they have no further optimizations to apply
|
||
fn try_extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) -> Result<(), TryReserveError> {
|
||
// 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.try_reserve(lower.saturating_add(1))?;
|
||
}
|
||
unsafe {
|
||
ptr::write(self.as_mut_ptr().add(len), element);
|
||
// Since next() executes user code which can panic we have to bump the length
|
||
// after each step.
|
||
// NB can't overflow since we would have had to alloc the address space
|
||
self.set_len(len + 1);
|
||
}
|
||
}
|
||
|
||
Ok(())
|
||
}
|
||
|
||
// specific extend for `TrustedLen` iterators, called both by the specializations
|
||
// and internal places where resolving specialization makes compilation slower
|
||
#[cfg(not(no_global_oom_handling))]
|
||
fn extend_trusted(&mut self, iterator: impl iter::TrustedLen<Item = T>) {
|
||
let (low, high) = iterator.size_hint();
|
||
if let Some(additional) = high {
|
||
debug_assert_eq!(
|
||
low,
|
||
additional,
|
||
"TrustedLen iterator's size hint is not exact: {:?}",
|
||
(low, high)
|
||
);
|
||
self.reserve(additional);
|
||
unsafe {
|
||
let ptr = self.as_mut_ptr();
|
||
let mut local_len = SetLenOnDrop::new(&mut self.len);
|
||
iterator.for_each(move |element| {
|
||
ptr::write(ptr.add(local_len.current_len()), element);
|
||
// Since the loop executes user code which can panic we have to update
|
||
// the length every step to correctly drop what we've written.
|
||
// NB can't overflow since we would have had to alloc the address space
|
||
local_len.increment_len(1);
|
||
});
|
||
}
|
||
} else {
|
||
// Per TrustedLen contract a `None` upper bound means that the iterator length
|
||
// truly exceeds usize::MAX, which would eventually lead to a capacity overflow anyway.
|
||
// Since the other branch already panics eagerly (via `reserve()`) we do the same here.
|
||
// This avoids additional codegen for a fallback code path which would eventually
|
||
// panic anyway.
|
||
panic!("capacity overflow");
|
||
}
|
||
}
|
||
|
||
// specific extend for `TrustedLen` iterators, called both by the specializations
|
||
// and internal places where resolving specialization makes compilation slower
|
||
fn try_extend_trusted(&mut self, iterator: impl iter::TrustedLen<Item = T>) -> Result<(), TryReserveError> {
|
||
let (low, high) = iterator.size_hint();
|
||
if let Some(additional) = high {
|
||
debug_assert_eq!(
|
||
low,
|
||
additional,
|
||
"TrustedLen iterator's size hint is not exact: {:?}",
|
||
(low, high)
|
||
);
|
||
self.try_reserve(additional)?;
|
||
unsafe {
|
||
let ptr = self.as_mut_ptr();
|
||
let mut local_len = SetLenOnDrop::new(&mut self.len);
|
||
iterator.for_each(move |element| {
|
||
ptr::write(ptr.add(local_len.current_len()), element);
|
||
// Since the loop executes user code which can panic we have to update
|
||
// the length every step to correctly drop what we've written.
|
||
// NB can't overflow since we would have had to alloc the address space
|
||
local_len.increment_len(1);
|
||
});
|
||
}
|
||
Ok(())
|
||
} else {
|
||
Err(TryReserveErrorKind::CapacityOverflow.into())
|
||
}
|
||
}
|
||
|
||
/// 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`.
|
||
///
|
||
/// `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 or equal 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, 4];
|
||
/// let new = [7, 8, 9];
|
||
/// let u: Vec<_> = v.splice(1..3, new).collect();
|
||
/// assert_eq!(v, &[1, 7, 8, 9, 4]);
|
||
/// assert_eq!(u, &[2, 3]);
|
||
/// ```
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[inline]
|
||
#[stable(feature = "vec_splice", since = "1.21.0")]
|
||
pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter, A>
|
||
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, A>
|
||
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`]: slice::copy_from_slice
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "extend_ref", since = "1.2.0")]
|
||
impl<'a, T: Copy + 'a, A: Allocator + 'a> Extend<&'a T> for Vec<T, A> {
|
||
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);
|
||
}
|
||
}
|
||
|
||
/// Implements comparison of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison).
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: PartialOrd, A: Allocator> PartialOrd for Vec<T, A> {
|
||
#[inline]
|
||
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
|
||
PartialOrd::partial_cmp(&**self, &**other)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Eq, A: Allocator> Eq for Vec<T, A> {}
|
||
|
||
/// Implements ordering of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison).
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Ord, A: Allocator> Ord for Vec<T, A> {
|
||
#[inline]
|
||
fn cmp(&self, other: &Self) -> Ordering {
|
||
Ord::cmp(&**self, &**other)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
unsafe impl<#[may_dangle] T, A: Allocator> Drop for Vec<T, A> {
|
||
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")]
|
||
#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
|
||
impl<T> const Default for Vec<T> {
|
||
/// Creates an empty `Vec<T>`.
|
||
///
|
||
/// The vector will not allocate until elements are pushed onto it.
|
||
fn default() -> Vec<T> {
|
||
Vec::new()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: fmt::Debug, A: Allocator> fmt::Debug for Vec<T, A> {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
fmt::Debug::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T, A: Allocator> AsRef<Vec<T, A>> for Vec<T, A> {
|
||
fn as_ref(&self) -> &Vec<T, A> {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "vec_as_mut", since = "1.5.0")]
|
||
impl<T, A: Allocator> AsMut<Vec<T, A>> for Vec<T, A> {
|
||
fn as_mut(&mut self) -> &mut Vec<T, A> {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T, A: Allocator> AsRef<[T]> for Vec<T, A> {
|
||
fn as_ref(&self) -> &[T] {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "vec_as_mut", since = "1.5.0")]
|
||
impl<T, A: Allocator> AsMut<[T]> for Vec<T, A> {
|
||
fn as_mut(&mut self) -> &mut [T] {
|
||
self
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Clone> From<&[T]> for Vec<T> {
|
||
/// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(Vec::from(&[1, 2, 3][..]), vec![1, 2, 3]);
|
||
/// ```
|
||
#[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, Global)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "vec_from_mut", since = "1.19.0")]
|
||
impl<T: Clone> From<&mut [T]> for Vec<T> {
|
||
/// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(Vec::from(&mut [1, 2, 3][..]), vec![1, 2, 3]);
|
||
/// ```
|
||
#[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, Global)
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "vec_from_array", since = "1.44.0")]
|
||
impl<T, const N: usize> From<[T; N]> for Vec<T> {
|
||
/// Allocate a `Vec<T>` and move `s`'s items into it.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(Vec::from([1, 2, 3]), vec![1, 2, 3]);
|
||
/// ```
|
||
#[cfg(not(test))]
|
||
fn from(s: [T; N]) -> Vec<T> {
|
||
<[T]>::into_vec(
|
||
#[rustc_box]
|
||
Box::new(s),
|
||
)
|
||
}
|
||
|
||
#[cfg(test)]
|
||
fn from(s: [T; N]) -> Vec<T> {
|
||
crate::slice::into_vec(Box::new(s))
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_borrow))]
|
||
#[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>>,
|
||
{
|
||
/// Convert a clone-on-write slice into a vector.
|
||
///
|
||
/// If `s` already owns a `Vec<T>`, it will be returned directly.
|
||
/// If `s` is borrowing a slice, a new `Vec<T>` will be allocated and
|
||
/// filled by cloning `s`'s items into it.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// # use std::borrow::Cow;
|
||
/// let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]);
|
||
/// let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]);
|
||
/// assert_eq!(Vec::from(o), Vec::from(b));
|
||
/// ```
|
||
fn from(s: Cow<'a, [T]>) -> Vec<T> {
|
||
s.into_owned()
|
||
}
|
||
}
|
||
|
||
// note: test pulls in std, which causes errors here
|
||
#[cfg(not(test))]
|
||
#[stable(feature = "vec_from_box", since = "1.18.0")]
|
||
impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A> {
|
||
/// Convert a boxed slice into a vector by transferring ownership of
|
||
/// the existing heap allocation.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// let b: Box<[i32]> = vec![1, 2, 3].into_boxed_slice();
|
||
/// assert_eq!(Vec::from(b), vec![1, 2, 3]);
|
||
/// ```
|
||
fn from(s: Box<[T], A>) -> Self {
|
||
s.into_vec()
|
||
}
|
||
}
|
||
|
||
// note: test pulls in std, which causes errors here
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[cfg(not(test))]
|
||
#[stable(feature = "box_from_vec", since = "1.20.0")]
|
||
impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> {
|
||
/// Convert a vector into a boxed slice.
|
||
///
|
||
/// If `v` has excess capacity, its items will be moved into a
|
||
/// newly-allocated buffer with exactly the right capacity.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice());
|
||
/// ```
|
||
///
|
||
/// Any excess capacity is removed:
|
||
/// ```
|
||
/// let mut vec = Vec::with_capacity(10);
|
||
/// vec.extend([1, 2, 3]);
|
||
///
|
||
/// assert_eq!(Box::from(vec), vec![1, 2, 3].into_boxed_slice());
|
||
/// ```
|
||
fn from(v: Vec<T, A>) -> Self {
|
||
v.into_boxed_slice()
|
||
}
|
||
}
|
||
|
||
#[cfg(not(no_global_oom_handling))]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl From<&str> for Vec<u8> {
|
||
/// Allocate a `Vec<u8>` and fill it with a UTF-8 string.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(Vec::from("123"), vec![b'1', b'2', b'3']);
|
||
/// ```
|
||
fn from(s: &str) -> Vec<u8> {
|
||
From::from(s.as_bytes())
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "array_try_from_vec", since = "1.48.0")]
|
||
impl<T, A: Allocator, const N: usize> TryFrom<Vec<T, A>> for [T; N] {
|
||
type Error = Vec<T, A>;
|
||
|
||
/// Gets the entire contents of the `Vec<T>` as an array,
|
||
/// if its size exactly matches that of the requested array.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// assert_eq!(vec![1, 2, 3].try_into(), Ok([1, 2, 3]));
|
||
/// assert_eq!(<Vec<i32>>::new().try_into(), Ok([]));
|
||
/// ```
|
||
///
|
||
/// If the length doesn't match, the input comes back in `Err`:
|
||
/// ```
|
||
/// let r: Result<[i32; 4], _> = (0..10).collect::<Vec<_>>().try_into();
|
||
/// assert_eq!(r, Err(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9]));
|
||
/// ```
|
||
///
|
||
/// If you're fine with just getting a prefix of the `Vec<T>`,
|
||
/// you can call [`.truncate(N)`](Vec::truncate) first.
|
||
/// ```
|
||
/// let mut v = String::from("hello world").into_bytes();
|
||
/// v.sort();
|
||
/// v.truncate(2);
|
||
/// let [a, b]: [_; 2] = v.try_into().unwrap();
|
||
/// assert_eq!(a, b' ');
|
||
/// assert_eq!(b, b'd');
|
||
/// ```
|
||
fn try_from(mut vec: Vec<T, A>) -> Result<[T; N], Vec<T, A>> {
|
||
if vec.len() != N {
|
||
return Err(vec);
|
||
}
|
||
|
||
// SAFETY: `.set_len(0)` is always sound.
|
||
unsafe { vec.set_len(0) };
|
||
|
||
// SAFETY: A `Vec`'s pointer is always aligned properly, and
|
||
// the alignment the array needs is the same as the items.
|
||
// We checked earlier that we have sufficient items.
|
||
// The items will not double-drop as the `set_len`
|
||
// tells the `Vec` not to also drop them.
|
||
let array = unsafe { ptr::read(vec.as_ptr() as *const [T; N]) };
|
||
Ok(array)
|
||
}
|
||
}
|