2029 lines
64 KiB
Rust
2029 lines
64 KiB
Rust
// SPDX-License-Identifier: Apache-2.0 OR MIT
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//! A pointer type for heap allocation.
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//!
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//! [`Box<T>`], casually referred to as a 'box', provides the simplest form of
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//! heap allocation in Rust. Boxes provide ownership for this allocation, and
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//! drop their contents when they go out of scope. Boxes also ensure that they
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//! never allocate more than `isize::MAX` bytes.
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//!
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//! # Examples
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//!
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//! Move a value from the stack to the heap by creating a [`Box`]:
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//!
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//! ```
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//! let val: u8 = 5;
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//! let boxed: Box<u8> = Box::new(val);
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//! ```
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//!
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//! Move a value from a [`Box`] back to the stack by [dereferencing]:
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//!
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//! ```
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//! let boxed: Box<u8> = Box::new(5);
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//! let val: u8 = *boxed;
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//! ```
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//!
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//! Creating a recursive data structure:
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//!
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//! ```
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//! #[derive(Debug)]
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//! enum List<T> {
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//! Cons(T, Box<List<T>>),
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//! Nil,
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//! }
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//!
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//! let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))));
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//! println!("{list:?}");
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//! ```
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//!
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//! This will print `Cons(1, Cons(2, Nil))`.
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//!
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//! Recursive structures must be boxed, because if the definition of `Cons`
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//! looked like this:
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//!
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//! ```compile_fail,E0072
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//! # enum List<T> {
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//! Cons(T, List<T>),
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//! # }
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//! ```
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//!
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//! It wouldn't work. This is because the size of a `List` depends on how many
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//! elements are in the list, and so we don't know how much memory to allocate
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//! for a `Cons`. By introducing a [`Box<T>`], which has a defined size, we know how
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//! big `Cons` needs to be.
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//!
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//! # Memory layout
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//!
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//! For non-zero-sized values, a [`Box`] will use the [`Global`] allocator for
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//! its allocation. It is valid to convert both ways between a [`Box`] and a
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//! raw pointer allocated with the [`Global`] allocator, given that the
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//! [`Layout`] used with the allocator is correct for the type. More precisely,
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//! a `value: *mut T` that has been allocated with the [`Global`] allocator
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//! with `Layout::for_value(&*value)` may be converted into a box using
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//! [`Box::<T>::from_raw(value)`]. Conversely, the memory backing a `value: *mut
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//! T` obtained from [`Box::<T>::into_raw`] may be deallocated using the
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//! [`Global`] allocator with [`Layout::for_value(&*value)`].
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//!
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//! For zero-sized values, the `Box` pointer still has to be [valid] for reads
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//! and writes and sufficiently aligned. In particular, casting any aligned
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//! non-zero integer literal to a raw pointer produces a valid pointer, but a
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//! pointer pointing into previously allocated memory that since got freed is
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//! not valid. The recommended way to build a Box to a ZST if `Box::new` cannot
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//! be used is to use [`ptr::NonNull::dangling`].
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//!
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//! So long as `T: Sized`, a `Box<T>` is guaranteed to be represented
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//! as a single pointer and is also ABI-compatible with C pointers
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//! (i.e. the C type `T*`). This means that if you have extern "C"
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//! Rust functions that will be called from C, you can define those
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//! Rust functions using `Box<T>` types, and use `T*` as corresponding
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//! type on the C side. As an example, consider this C header which
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//! declares functions that create and destroy some kind of `Foo`
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//! value:
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//!
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//! ```c
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//! /* C header */
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//!
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//! /* Returns ownership to the caller */
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//! struct Foo* foo_new(void);
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//!
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//! /* Takes ownership from the caller; no-op when invoked with null */
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//! void foo_delete(struct Foo*);
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//! ```
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//!
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//! These two functions might be implemented in Rust as follows. Here, the
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//! `struct Foo*` type from C is translated to `Box<Foo>`, which captures
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//! the ownership constraints. Note also that the nullable argument to
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//! `foo_delete` is represented in Rust as `Option<Box<Foo>>`, since `Box<Foo>`
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//! cannot be null.
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//!
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//! ```
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//! #[repr(C)]
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//! pub struct Foo;
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//!
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//! #[no_mangle]
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//! pub extern "C" fn foo_new() -> Box<Foo> {
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//! Box::new(Foo)
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//! }
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//!
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//! #[no_mangle]
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//! pub extern "C" fn foo_delete(_: Option<Box<Foo>>) {}
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//! ```
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//!
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//! Even though `Box<T>` has the same representation and C ABI as a C pointer,
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//! this does not mean that you can convert an arbitrary `T*` into a `Box<T>`
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//! and expect things to work. `Box<T>` values will always be fully aligned,
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//! non-null pointers. Moreover, the destructor for `Box<T>` will attempt to
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//! free the value with the global allocator. In general, the best practice
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//! is to only use `Box<T>` for pointers that originated from the global
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//! allocator.
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//!
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//! **Important.** At least at present, you should avoid using
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//! `Box<T>` types for functions that are defined in C but invoked
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//! from Rust. In those cases, you should directly mirror the C types
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//! as closely as possible. Using types like `Box<T>` where the C
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//! definition is just using `T*` can lead to undefined behavior, as
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//! described in [rust-lang/unsafe-code-guidelines#198][ucg#198].
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//!
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//! [ucg#198]: https://github.com/rust-lang/unsafe-code-guidelines/issues/198
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//! [dereferencing]: core::ops::Deref
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//! [`Box::<T>::from_raw(value)`]: Box::from_raw
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//! [`Global`]: crate::alloc::Global
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//! [`Layout`]: crate::alloc::Layout
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//! [`Layout::for_value(&*value)`]: crate::alloc::Layout::for_value
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//! [valid]: ptr#safety
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#![stable(feature = "rust1", since = "1.0.0")]
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use core::any::Any;
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use core::async_iter::AsyncIterator;
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use core::borrow;
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use core::cmp::Ordering;
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use core::convert::{From, TryFrom};
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use core::fmt;
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use core::future::Future;
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use core::hash::{Hash, Hasher};
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#[cfg(not(no_global_oom_handling))]
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use core::iter::FromIterator;
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use core::iter::{FusedIterator, Iterator};
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use core::marker::{Destruct, Unpin, Unsize};
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use core::mem;
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use core::ops::{
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CoerceUnsized, Deref, DerefMut, DispatchFromDyn, Generator, GeneratorState, Receiver,
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};
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use core::pin::Pin;
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use core::ptr::{self, Unique};
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use core::task::{Context, Poll};
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#[cfg(not(no_global_oom_handling))]
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use crate::alloc::{handle_alloc_error, WriteCloneIntoRaw};
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use crate::alloc::{AllocError, Allocator, Global, Layout};
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#[cfg(not(no_global_oom_handling))]
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use crate::borrow::Cow;
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use crate::raw_vec::RawVec;
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#[cfg(not(no_global_oom_handling))]
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use crate::str::from_boxed_utf8_unchecked;
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#[cfg(not(no_global_oom_handling))]
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use crate::vec::Vec;
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#[cfg(not(no_thin))]
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#[unstable(feature = "thin_box", issue = "92791")]
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pub use thin::ThinBox;
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#[cfg(not(no_thin))]
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mod thin;
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/// A pointer type for heap allocation.
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///
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/// See the [module-level documentation](../../std/boxed/index.html) for more.
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#[lang = "owned_box"]
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#[fundamental]
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#[stable(feature = "rust1", since = "1.0.0")]
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// The declaration of the `Box` struct must be kept in sync with the
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// `alloc::alloc::box_free` function or ICEs will happen. See the comment
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// on `box_free` for more details.
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pub struct Box<
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T: ?Sized,
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#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
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>(Unique<T>, A);
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impl<T> Box<T> {
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/// Allocates memory on the heap and then places `x` into it.
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///
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/// This doesn't actually allocate if `T` is zero-sized.
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///
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/// # Examples
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///
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/// ```
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/// let five = Box::new(5);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[inline(always)]
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#[stable(feature = "rust1", since = "1.0.0")]
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#[must_use]
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pub fn new(x: T) -> Self {
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box x
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}
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/// Constructs a new box with uninitialized contents.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(new_uninit)]
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///
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/// let mut five = Box::<u32>::new_uninit();
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///
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/// let five = unsafe {
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/// // Deferred initialization:
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/// five.as_mut_ptr().write(5);
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///
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/// five.assume_init()
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/// };
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///
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/// assert_eq!(*five, 5)
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[unstable(feature = "new_uninit", issue = "63291")]
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#[must_use]
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#[inline]
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pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
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Self::new_uninit_in(Global)
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}
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/// Constructs a new `Box` with uninitialized contents, with the memory
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/// being filled with `0` bytes.
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///
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/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
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/// of this method.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(new_uninit)]
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///
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/// let zero = Box::<u32>::new_zeroed();
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/// let zero = unsafe { zero.assume_init() };
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///
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/// assert_eq!(*zero, 0)
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/// ```
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///
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/// [zeroed]: mem::MaybeUninit::zeroed
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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#[unstable(feature = "new_uninit", issue = "63291")]
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#[must_use]
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pub fn new_zeroed() -> Box<mem::MaybeUninit<T>> {
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Self::new_zeroed_in(Global)
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}
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/// Constructs a new `Pin<Box<T>>`. If `T` does not implement `Unpin`, then
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/// `x` will be pinned in memory and unable to be moved.
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "pin", since = "1.33.0")]
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#[must_use]
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#[inline(always)]
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pub fn pin(x: T) -> Pin<Box<T>> {
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(box x).into()
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}
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/// Allocates memory on the heap then places `x` into it,
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/// returning an error if the allocation fails
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///
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/// This doesn't actually allocate if `T` is zero-sized.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(allocator_api)]
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///
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/// let five = Box::try_new(5)?;
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/// # Ok::<(), std::alloc::AllocError>(())
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/// ```
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[inline]
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pub fn try_new(x: T) -> Result<Self, AllocError> {
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Self::try_new_in(x, Global)
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}
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/// Constructs a new box with uninitialized contents on the heap,
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/// returning an error if the allocation fails
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///
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/// # Examples
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///
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/// ```
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/// #![feature(allocator_api, new_uninit)]
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///
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/// let mut five = Box::<u32>::try_new_uninit()?;
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///
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/// let five = unsafe {
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/// // Deferred initialization:
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/// five.as_mut_ptr().write(5);
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///
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/// five.assume_init()
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/// };
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///
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/// assert_eq!(*five, 5);
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/// # Ok::<(), std::alloc::AllocError>(())
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/// ```
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#[unstable(feature = "allocator_api", issue = "32838")]
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// #[unstable(feature = "new_uninit", issue = "63291")]
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#[inline]
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pub fn try_new_uninit() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
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Box::try_new_uninit_in(Global)
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}
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/// Constructs a new `Box` with uninitialized contents, with the memory
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/// being filled with `0` bytes on the heap
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///
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/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
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/// of this method.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(allocator_api, new_uninit)]
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///
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/// let zero = Box::<u32>::try_new_zeroed()?;
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/// let zero = unsafe { zero.assume_init() };
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///
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/// assert_eq!(*zero, 0);
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/// # Ok::<(), std::alloc::AllocError>(())
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/// ```
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///
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/// [zeroed]: mem::MaybeUninit::zeroed
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#[unstable(feature = "allocator_api", issue = "32838")]
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// #[unstable(feature = "new_uninit", issue = "63291")]
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#[inline]
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pub fn try_new_zeroed() -> Result<Box<mem::MaybeUninit<T>>, AllocError> {
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Box::try_new_zeroed_in(Global)
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}
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}
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impl<T, A: Allocator> Box<T, A> {
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/// Allocates memory in the given allocator then places `x` into it.
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///
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/// This doesn't actually allocate if `T` is zero-sized.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(allocator_api)]
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///
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/// use std::alloc::System;
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///
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/// let five = Box::new_in(5, System);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[rustc_const_unstable(feature = "const_box", issue = "92521")]
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#[must_use]
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#[inline]
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pub const fn new_in(x: T, alloc: A) -> Self
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where
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A: ~const Allocator + ~const Destruct,
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{
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let mut boxed = Self::new_uninit_in(alloc);
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unsafe {
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boxed.as_mut_ptr().write(x);
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boxed.assume_init()
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}
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}
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/// Allocates memory in the given allocator then places `x` into it,
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/// returning an error if the allocation fails
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///
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/// This doesn't actually allocate if `T` is zero-sized.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(allocator_api)]
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///
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/// use std::alloc::System;
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///
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/// let five = Box::try_new_in(5, System)?;
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/// # Ok::<(), std::alloc::AllocError>(())
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/// ```
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[rustc_const_unstable(feature = "const_box", issue = "92521")]
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#[inline]
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pub const fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError>
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where
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T: ~const Destruct,
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A: ~const Allocator + ~const Destruct,
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{
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let mut boxed = Self::try_new_uninit_in(alloc)?;
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unsafe {
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boxed.as_mut_ptr().write(x);
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Ok(boxed.assume_init())
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}
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}
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/// Constructs a new box with uninitialized contents in the provided allocator.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(allocator_api, new_uninit)]
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///
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/// use std::alloc::System;
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///
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/// let mut five = Box::<u32, _>::new_uninit_in(System);
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///
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/// let five = unsafe {
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/// // Deferred initialization:
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/// five.as_mut_ptr().write(5);
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///
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/// five.assume_init()
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/// };
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///
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/// assert_eq!(*five, 5)
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/// ```
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[rustc_const_unstable(feature = "const_box", issue = "92521")]
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#[cfg(not(no_global_oom_handling))]
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#[must_use]
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// #[unstable(feature = "new_uninit", issue = "63291")]
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pub const fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
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where
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A: ~const Allocator + ~const Destruct,
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{
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let layout = Layout::new::<mem::MaybeUninit<T>>();
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// NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
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// That would make code size bigger.
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match Box::try_new_uninit_in(alloc) {
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Ok(m) => m,
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Err(_) => handle_alloc_error(layout),
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}
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}
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/// Constructs a new box with uninitialized contents in the provided allocator,
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/// returning an error if the allocation fails
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///
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/// # Examples
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///
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/// ```
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/// #![feature(allocator_api, new_uninit)]
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///
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/// use std::alloc::System;
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///
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/// let mut five = Box::<u32, _>::try_new_uninit_in(System)?;
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///
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/// let five = unsafe {
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/// // Deferred initialization:
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/// five.as_mut_ptr().write(5);
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///
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/// five.assume_init()
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/// };
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///
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/// assert_eq!(*five, 5);
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/// # Ok::<(), std::alloc::AllocError>(())
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/// ```
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#[unstable(feature = "allocator_api", issue = "32838")]
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// #[unstable(feature = "new_uninit", issue = "63291")]
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#[rustc_const_unstable(feature = "const_box", issue = "92521")]
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pub const fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
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where
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A: ~const Allocator + ~const Destruct,
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{
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let layout = Layout::new::<mem::MaybeUninit<T>>();
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let ptr = alloc.allocate(layout)?.cast();
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unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
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}
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/// Constructs a new `Box` with uninitialized contents, with the memory
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/// being filled with `0` bytes in the provided allocator.
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///
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/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
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/// of this method.
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///
|
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/// # Examples
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///
|
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/// ```
|
|
/// #![feature(allocator_api, new_uninit)]
|
|
///
|
|
/// use std::alloc::System;
|
|
///
|
|
/// let zero = Box::<u32, _>::new_zeroed_in(System);
|
|
/// let zero = unsafe { zero.assume_init() };
|
|
///
|
|
/// assert_eq!(*zero, 0)
|
|
/// ```
|
|
///
|
|
/// [zeroed]: mem::MaybeUninit::zeroed
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[cfg(not(no_global_oom_handling))]
|
|
// #[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[must_use]
|
|
pub const fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
|
|
where
|
|
A: ~const Allocator + ~const Destruct,
|
|
{
|
|
let layout = Layout::new::<mem::MaybeUninit<T>>();
|
|
// NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
|
|
// That would make code size bigger.
|
|
match Box::try_new_zeroed_in(alloc) {
|
|
Ok(m) => m,
|
|
Err(_) => handle_alloc_error(layout),
|
|
}
|
|
}
|
|
|
|
/// Constructs a new `Box` with uninitialized contents, with the memory
|
|
/// being filled with `0` bytes in the provided allocator,
|
|
/// returning an error if the allocation fails,
|
|
///
|
|
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
|
/// of this method.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(allocator_api, new_uninit)]
|
|
///
|
|
/// use std::alloc::System;
|
|
///
|
|
/// let zero = Box::<u32, _>::try_new_zeroed_in(System)?;
|
|
/// let zero = unsafe { zero.assume_init() };
|
|
///
|
|
/// assert_eq!(*zero, 0);
|
|
/// # Ok::<(), std::alloc::AllocError>(())
|
|
/// ```
|
|
///
|
|
/// [zeroed]: mem::MaybeUninit::zeroed
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
// #[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
pub const fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
|
|
where
|
|
A: ~const Allocator + ~const Destruct,
|
|
{
|
|
let layout = Layout::new::<mem::MaybeUninit<T>>();
|
|
let ptr = alloc.allocate_zeroed(layout)?.cast();
|
|
unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
|
|
}
|
|
|
|
/// Constructs a new `Pin<Box<T, A>>`. If `T` does not implement `Unpin`, then
|
|
/// `x` will be pinned in memory and unable to be moved.
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[must_use]
|
|
#[inline(always)]
|
|
pub const fn pin_in(x: T, alloc: A) -> Pin<Self>
|
|
where
|
|
A: 'static + ~const Allocator + ~const Destruct,
|
|
{
|
|
Self::into_pin(Self::new_in(x, alloc))
|
|
}
|
|
|
|
/// Converts a `Box<T>` into a `Box<[T]>`
|
|
///
|
|
/// This conversion does not allocate on the heap and happens in place.
|
|
#[unstable(feature = "box_into_boxed_slice", issue = "71582")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
pub const fn into_boxed_slice(boxed: Self) -> Box<[T], A> {
|
|
let (raw, alloc) = Box::into_raw_with_allocator(boxed);
|
|
unsafe { Box::from_raw_in(raw as *mut [T; 1], alloc) }
|
|
}
|
|
|
|
/// Consumes the `Box`, returning the wrapped value.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(box_into_inner)]
|
|
///
|
|
/// let c = Box::new(5);
|
|
///
|
|
/// assert_eq!(Box::into_inner(c), 5);
|
|
/// ```
|
|
#[unstable(feature = "box_into_inner", issue = "80437")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
pub const fn into_inner(boxed: Self) -> T
|
|
where
|
|
Self: ~const Destruct,
|
|
{
|
|
*boxed
|
|
}
|
|
}
|
|
|
|
impl<T> Box<[T]> {
|
|
/// Constructs a new boxed slice with uninitialized contents.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(new_uninit)]
|
|
///
|
|
/// let mut values = Box::<[u32]>::new_uninit_slice(3);
|
|
///
|
|
/// let values = unsafe {
|
|
/// // Deferred initialization:
|
|
/// values[0].as_mut_ptr().write(1);
|
|
/// values[1].as_mut_ptr().write(2);
|
|
/// values[2].as_mut_ptr().write(3);
|
|
///
|
|
/// values.assume_init()
|
|
/// };
|
|
///
|
|
/// assert_eq!(*values, [1, 2, 3])
|
|
/// ```
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[must_use]
|
|
pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
|
|
unsafe { RawVec::with_capacity(len).into_box(len) }
|
|
}
|
|
|
|
/// Constructs a new boxed slice with uninitialized contents, with the memory
|
|
/// being filled with `0` bytes.
|
|
///
|
|
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
|
/// of this method.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(new_uninit)]
|
|
///
|
|
/// let values = Box::<[u32]>::new_zeroed_slice(3);
|
|
/// let values = unsafe { values.assume_init() };
|
|
///
|
|
/// assert_eq!(*values, [0, 0, 0])
|
|
/// ```
|
|
///
|
|
/// [zeroed]: mem::MaybeUninit::zeroed
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[must_use]
|
|
pub fn new_zeroed_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
|
|
unsafe { RawVec::with_capacity_zeroed(len).into_box(len) }
|
|
}
|
|
|
|
/// Constructs a new boxed slice with uninitialized contents. Returns an error if
|
|
/// the allocation fails
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(allocator_api, new_uninit)]
|
|
///
|
|
/// let mut values = Box::<[u32]>::try_new_uninit_slice(3)?;
|
|
/// let values = unsafe {
|
|
/// // Deferred initialization:
|
|
/// values[0].as_mut_ptr().write(1);
|
|
/// values[1].as_mut_ptr().write(2);
|
|
/// values[2].as_mut_ptr().write(3);
|
|
/// values.assume_init()
|
|
/// };
|
|
///
|
|
/// assert_eq!(*values, [1, 2, 3]);
|
|
/// # Ok::<(), std::alloc::AllocError>(())
|
|
/// ```
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[inline]
|
|
pub fn try_new_uninit_slice(len: usize) -> Result<Box<[mem::MaybeUninit<T>]>, AllocError> {
|
|
unsafe {
|
|
let layout = match Layout::array::<mem::MaybeUninit<T>>(len) {
|
|
Ok(l) => l,
|
|
Err(_) => return Err(AllocError),
|
|
};
|
|
let ptr = Global.allocate(layout)?;
|
|
Ok(RawVec::from_raw_parts_in(ptr.as_mut_ptr() as *mut _, len, Global).into_box(len))
|
|
}
|
|
}
|
|
|
|
/// Constructs a new boxed slice with uninitialized contents, with the memory
|
|
/// being filled with `0` bytes. Returns an error if the allocation fails
|
|
///
|
|
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
|
/// of this method.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(allocator_api, new_uninit)]
|
|
///
|
|
/// let values = Box::<[u32]>::try_new_zeroed_slice(3)?;
|
|
/// let values = unsafe { values.assume_init() };
|
|
///
|
|
/// assert_eq!(*values, [0, 0, 0]);
|
|
/// # Ok::<(), std::alloc::AllocError>(())
|
|
/// ```
|
|
///
|
|
/// [zeroed]: mem::MaybeUninit::zeroed
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[inline]
|
|
pub fn try_new_zeroed_slice(len: usize) -> Result<Box<[mem::MaybeUninit<T>]>, AllocError> {
|
|
unsafe {
|
|
let layout = match Layout::array::<mem::MaybeUninit<T>>(len) {
|
|
Ok(l) => l,
|
|
Err(_) => return Err(AllocError),
|
|
};
|
|
let ptr = Global.allocate_zeroed(layout)?;
|
|
Ok(RawVec::from_raw_parts_in(ptr.as_mut_ptr() as *mut _, len, Global).into_box(len))
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T, A: Allocator> Box<[T], A> {
|
|
/// Constructs a new boxed slice with uninitialized contents in the provided allocator.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(allocator_api, new_uninit)]
|
|
///
|
|
/// use std::alloc::System;
|
|
///
|
|
/// let mut values = Box::<[u32], _>::new_uninit_slice_in(3, System);
|
|
///
|
|
/// let values = unsafe {
|
|
/// // Deferred initialization:
|
|
/// values[0].as_mut_ptr().write(1);
|
|
/// values[1].as_mut_ptr().write(2);
|
|
/// values[2].as_mut_ptr().write(3);
|
|
///
|
|
/// values.assume_init()
|
|
/// };
|
|
///
|
|
/// assert_eq!(*values, [1, 2, 3])
|
|
/// ```
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
// #[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[must_use]
|
|
pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
|
|
unsafe { RawVec::with_capacity_in(len, alloc).into_box(len) }
|
|
}
|
|
|
|
/// Constructs a new boxed slice with uninitialized contents in the provided allocator,
|
|
/// with the memory being filled with `0` bytes.
|
|
///
|
|
/// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
|
|
/// of this method.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(allocator_api, new_uninit)]
|
|
///
|
|
/// use std::alloc::System;
|
|
///
|
|
/// let values = Box::<[u32], _>::new_zeroed_slice_in(3, System);
|
|
/// let values = unsafe { values.assume_init() };
|
|
///
|
|
/// assert_eq!(*values, [0, 0, 0])
|
|
/// ```
|
|
///
|
|
/// [zeroed]: mem::MaybeUninit::zeroed
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
// #[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[must_use]
|
|
pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
|
|
unsafe { RawVec::with_capacity_zeroed_in(len, alloc).into_box(len) }
|
|
}
|
|
}
|
|
|
|
impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
|
|
/// Converts to `Box<T, A>`.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// As with [`MaybeUninit::assume_init`],
|
|
/// it is up to the caller to guarantee that the value
|
|
/// really is in an initialized state.
|
|
/// Calling this when the content is not yet fully initialized
|
|
/// causes immediate undefined behavior.
|
|
///
|
|
/// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(new_uninit)]
|
|
///
|
|
/// let mut five = Box::<u32>::new_uninit();
|
|
///
|
|
/// let five: Box<u32> = unsafe {
|
|
/// // Deferred initialization:
|
|
/// five.as_mut_ptr().write(5);
|
|
///
|
|
/// five.assume_init()
|
|
/// };
|
|
///
|
|
/// assert_eq!(*five, 5)
|
|
/// ```
|
|
#[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
pub const unsafe fn assume_init(self) -> Box<T, A> {
|
|
let (raw, alloc) = Box::into_raw_with_allocator(self);
|
|
unsafe { Box::from_raw_in(raw as *mut T, alloc) }
|
|
}
|
|
|
|
/// Writes the value and converts to `Box<T, A>`.
|
|
///
|
|
/// This method converts the box similarly to [`Box::assume_init`] but
|
|
/// writes `value` into it before conversion thus guaranteeing safety.
|
|
/// In some scenarios use of this method may improve performance because
|
|
/// the compiler may be able to optimize copying from stack.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(new_uninit)]
|
|
///
|
|
/// let big_box = Box::<[usize; 1024]>::new_uninit();
|
|
///
|
|
/// let mut array = [0; 1024];
|
|
/// for (i, place) in array.iter_mut().enumerate() {
|
|
/// *place = i;
|
|
/// }
|
|
///
|
|
/// // The optimizer may be able to elide this copy, so previous code writes
|
|
/// // to heap directly.
|
|
/// let big_box = Box::write(big_box, array);
|
|
///
|
|
/// for (i, x) in big_box.iter().enumerate() {
|
|
/// assert_eq!(*x, i);
|
|
/// }
|
|
/// ```
|
|
#[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
pub const fn write(mut boxed: Self, value: T) -> Box<T, A> {
|
|
unsafe {
|
|
(*boxed).write(value);
|
|
boxed.assume_init()
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T, A: Allocator> Box<[mem::MaybeUninit<T>], A> {
|
|
/// Converts to `Box<[T], A>`.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// As with [`MaybeUninit::assume_init`],
|
|
/// it is up to the caller to guarantee that the values
|
|
/// really are in an initialized state.
|
|
/// Calling this when the content is not yet fully initialized
|
|
/// causes immediate undefined behavior.
|
|
///
|
|
/// [`MaybeUninit::assume_init`]: mem::MaybeUninit::assume_init
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(new_uninit)]
|
|
///
|
|
/// let mut values = Box::<[u32]>::new_uninit_slice(3);
|
|
///
|
|
/// let values = unsafe {
|
|
/// // Deferred initialization:
|
|
/// values[0].as_mut_ptr().write(1);
|
|
/// values[1].as_mut_ptr().write(2);
|
|
/// values[2].as_mut_ptr().write(3);
|
|
///
|
|
/// values.assume_init()
|
|
/// };
|
|
///
|
|
/// assert_eq!(*values, [1, 2, 3])
|
|
/// ```
|
|
#[unstable(feature = "new_uninit", issue = "63291")]
|
|
#[inline]
|
|
pub unsafe fn assume_init(self) -> Box<[T], A> {
|
|
let (raw, alloc) = Box::into_raw_with_allocator(self);
|
|
unsafe { Box::from_raw_in(raw as *mut [T], alloc) }
|
|
}
|
|
}
|
|
|
|
impl<T: ?Sized> Box<T> {
|
|
/// Constructs a box from a raw pointer.
|
|
///
|
|
/// After calling this function, the raw pointer is owned by the
|
|
/// resulting `Box`. Specifically, the `Box` destructor will call
|
|
/// the destructor of `T` and free the allocated memory. For this
|
|
/// to be safe, the memory must have been allocated in accordance
|
|
/// with the [memory layout] used by `Box` .
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// This function is unsafe because improper use may lead to
|
|
/// memory problems. For example, a double-free may occur if the
|
|
/// function is called twice on the same raw pointer.
|
|
///
|
|
/// The safety conditions are described in the [memory layout] section.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Recreate a `Box` which was previously converted to a raw pointer
|
|
/// using [`Box::into_raw`]:
|
|
/// ```
|
|
/// let x = Box::new(5);
|
|
/// let ptr = Box::into_raw(x);
|
|
/// let x = unsafe { Box::from_raw(ptr) };
|
|
/// ```
|
|
/// Manually create a `Box` from scratch by using the global allocator:
|
|
/// ```
|
|
/// use std::alloc::{alloc, Layout};
|
|
///
|
|
/// unsafe {
|
|
/// let ptr = alloc(Layout::new::<i32>()) as *mut i32;
|
|
/// // In general .write is required to avoid attempting to destruct
|
|
/// // the (uninitialized) previous contents of `ptr`, though for this
|
|
/// // simple example `*ptr = 5` would have worked as well.
|
|
/// ptr.write(5);
|
|
/// let x = Box::from_raw(ptr);
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// [memory layout]: self#memory-layout
|
|
/// [`Layout`]: crate::Layout
|
|
#[stable(feature = "box_raw", since = "1.4.0")]
|
|
#[inline]
|
|
pub unsafe fn from_raw(raw: *mut T) -> Self {
|
|
unsafe { Self::from_raw_in(raw, Global) }
|
|
}
|
|
}
|
|
|
|
impl<T: ?Sized, A: Allocator> Box<T, A> {
|
|
/// Constructs a box from a raw pointer in the given allocator.
|
|
///
|
|
/// After calling this function, the raw pointer is owned by the
|
|
/// resulting `Box`. Specifically, the `Box` destructor will call
|
|
/// the destructor of `T` and free the allocated memory. For this
|
|
/// to be safe, the memory must have been allocated in accordance
|
|
/// with the [memory layout] used by `Box` .
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// This function is unsafe because improper use may lead to
|
|
/// memory problems. For example, a double-free may occur if the
|
|
/// function is called twice on the same raw pointer.
|
|
///
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Recreate a `Box` which was previously converted to a raw pointer
|
|
/// using [`Box::into_raw_with_allocator`]:
|
|
/// ```
|
|
/// #![feature(allocator_api)]
|
|
///
|
|
/// use std::alloc::System;
|
|
///
|
|
/// let x = Box::new_in(5, System);
|
|
/// let (ptr, alloc) = Box::into_raw_with_allocator(x);
|
|
/// let x = unsafe { Box::from_raw_in(ptr, alloc) };
|
|
/// ```
|
|
/// Manually create a `Box` from scratch by using the system allocator:
|
|
/// ```
|
|
/// #![feature(allocator_api, slice_ptr_get)]
|
|
///
|
|
/// use std::alloc::{Allocator, Layout, System};
|
|
///
|
|
/// unsafe {
|
|
/// let ptr = System.allocate(Layout::new::<i32>())?.as_mut_ptr() as *mut i32;
|
|
/// // In general .write is required to avoid attempting to destruct
|
|
/// // the (uninitialized) previous contents of `ptr`, though for this
|
|
/// // simple example `*ptr = 5` would have worked as well.
|
|
/// ptr.write(5);
|
|
/// let x = Box::from_raw_in(ptr, System);
|
|
/// }
|
|
/// # Ok::<(), std::alloc::AllocError>(())
|
|
/// ```
|
|
///
|
|
/// [memory layout]: self#memory-layout
|
|
/// [`Layout`]: crate::Layout
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
pub const unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self {
|
|
Box(unsafe { Unique::new_unchecked(raw) }, alloc)
|
|
}
|
|
|
|
/// Consumes the `Box`, returning a wrapped raw pointer.
|
|
///
|
|
/// The pointer will be properly aligned and non-null.
|
|
///
|
|
/// After calling this function, the caller is responsible for the
|
|
/// memory previously managed by the `Box`. In particular, the
|
|
/// caller should properly destroy `T` and release the memory, taking
|
|
/// into account the [memory layout] used by `Box`. The easiest way to
|
|
/// do this is to convert the raw pointer back into a `Box` with the
|
|
/// [`Box::from_raw`] function, allowing the `Box` destructor to perform
|
|
/// the cleanup.
|
|
///
|
|
/// Note: this is an associated function, which means that you have
|
|
/// to call it as `Box::into_raw(b)` instead of `b.into_raw()`. This
|
|
/// is so that there is no conflict with a method on the inner type.
|
|
///
|
|
/// # Examples
|
|
/// Converting the raw pointer back into a `Box` with [`Box::from_raw`]
|
|
/// for automatic cleanup:
|
|
/// ```
|
|
/// let x = Box::new(String::from("Hello"));
|
|
/// let ptr = Box::into_raw(x);
|
|
/// let x = unsafe { Box::from_raw(ptr) };
|
|
/// ```
|
|
/// Manual cleanup by explicitly running the destructor and deallocating
|
|
/// the memory:
|
|
/// ```
|
|
/// use std::alloc::{dealloc, Layout};
|
|
/// use std::ptr;
|
|
///
|
|
/// let x = Box::new(String::from("Hello"));
|
|
/// let p = Box::into_raw(x);
|
|
/// unsafe {
|
|
/// ptr::drop_in_place(p);
|
|
/// dealloc(p as *mut u8, Layout::new::<String>());
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// [memory layout]: self#memory-layout
|
|
#[stable(feature = "box_raw", since = "1.4.0")]
|
|
#[inline]
|
|
pub fn into_raw(b: Self) -> *mut T {
|
|
Self::into_raw_with_allocator(b).0
|
|
}
|
|
|
|
/// Consumes the `Box`, returning a wrapped raw pointer and the allocator.
|
|
///
|
|
/// The pointer will be properly aligned and non-null.
|
|
///
|
|
/// After calling this function, the caller is responsible for the
|
|
/// memory previously managed by the `Box`. In particular, the
|
|
/// caller should properly destroy `T` and release the memory, taking
|
|
/// into account the [memory layout] used by `Box`. The easiest way to
|
|
/// do this is to convert the raw pointer back into a `Box` with the
|
|
/// [`Box::from_raw_in`] function, allowing the `Box` destructor to perform
|
|
/// the cleanup.
|
|
///
|
|
/// Note: this is an associated function, which means that you have
|
|
/// to call it as `Box::into_raw_with_allocator(b)` instead of `b.into_raw_with_allocator()`. This
|
|
/// is so that there is no conflict with a method on the inner type.
|
|
///
|
|
/// # Examples
|
|
/// Converting the raw pointer back into a `Box` with [`Box::from_raw_in`]
|
|
/// for automatic cleanup:
|
|
/// ```
|
|
/// #![feature(allocator_api)]
|
|
///
|
|
/// use std::alloc::System;
|
|
///
|
|
/// let x = Box::new_in(String::from("Hello"), System);
|
|
/// let (ptr, alloc) = Box::into_raw_with_allocator(x);
|
|
/// let x = unsafe { Box::from_raw_in(ptr, alloc) };
|
|
/// ```
|
|
/// Manual cleanup by explicitly running the destructor and deallocating
|
|
/// the memory:
|
|
/// ```
|
|
/// #![feature(allocator_api)]
|
|
///
|
|
/// use std::alloc::{Allocator, Layout, System};
|
|
/// use std::ptr::{self, NonNull};
|
|
///
|
|
/// let x = Box::new_in(String::from("Hello"), System);
|
|
/// let (ptr, alloc) = Box::into_raw_with_allocator(x);
|
|
/// unsafe {
|
|
/// ptr::drop_in_place(ptr);
|
|
/// let non_null = NonNull::new_unchecked(ptr);
|
|
/// alloc.deallocate(non_null.cast(), Layout::new::<String>());
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// [memory layout]: self#memory-layout
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
pub const fn into_raw_with_allocator(b: Self) -> (*mut T, A) {
|
|
let (leaked, alloc) = Box::into_unique(b);
|
|
(leaked.as_ptr(), alloc)
|
|
}
|
|
|
|
#[unstable(
|
|
feature = "ptr_internals",
|
|
issue = "none",
|
|
reason = "use `Box::leak(b).into()` or `Unique::from(Box::leak(b))` instead"
|
|
)]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
#[doc(hidden)]
|
|
pub const fn into_unique(b: Self) -> (Unique<T>, A) {
|
|
// Box is recognized as a "unique pointer" by Stacked Borrows, but internally it is a
|
|
// raw pointer for the type system. Turning it directly into a raw pointer would not be
|
|
// recognized as "releasing" the unique pointer to permit aliased raw accesses,
|
|
// so all raw pointer methods have to go through `Box::leak`. Turning *that* to a raw pointer
|
|
// behaves correctly.
|
|
let alloc = unsafe { ptr::read(&b.1) };
|
|
(Unique::from(Box::leak(b)), alloc)
|
|
}
|
|
|
|
/// Returns a reference to the underlying allocator.
|
|
///
|
|
/// Note: this is an associated function, which means that you have
|
|
/// to call it as `Box::allocator(&b)` instead of `b.allocator()`. This
|
|
/// is so that there is no conflict with a method on the inner type.
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
pub const fn allocator(b: &Self) -> &A {
|
|
&b.1
|
|
}
|
|
|
|
/// Consumes and leaks the `Box`, returning a mutable reference,
|
|
/// `&'a mut T`. Note that the type `T` must outlive the chosen lifetime
|
|
/// `'a`. If the type has only static references, or none at all, then this
|
|
/// may be chosen to be `'static`.
|
|
///
|
|
/// This function is mainly useful for data that lives for the remainder of
|
|
/// the program's life. Dropping the returned reference will cause a memory
|
|
/// leak. If this is not acceptable, the reference should first be wrapped
|
|
/// with the [`Box::from_raw`] function producing a `Box`. This `Box` can
|
|
/// then be dropped which will properly destroy `T` and release the
|
|
/// allocated memory.
|
|
///
|
|
/// Note: this is an associated function, which means that you have
|
|
/// to call it as `Box::leak(b)` instead of `b.leak()`. This
|
|
/// is so that there is no conflict with a method on the inner type.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Simple usage:
|
|
///
|
|
/// ```
|
|
/// let x = Box::new(41);
|
|
/// let static_ref: &'static mut usize = Box::leak(x);
|
|
/// *static_ref += 1;
|
|
/// assert_eq!(*static_ref, 42);
|
|
/// ```
|
|
///
|
|
/// Unsized data:
|
|
///
|
|
/// ```
|
|
/// let x = vec![1, 2, 3].into_boxed_slice();
|
|
/// let static_ref = Box::leak(x);
|
|
/// static_ref[0] = 4;
|
|
/// assert_eq!(*static_ref, [4, 2, 3]);
|
|
/// ```
|
|
#[stable(feature = "box_leak", since = "1.26.0")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
#[inline]
|
|
pub const fn leak<'a>(b: Self) -> &'a mut T
|
|
where
|
|
A: 'a,
|
|
{
|
|
unsafe { &mut *mem::ManuallyDrop::new(b).0.as_ptr() }
|
|
}
|
|
|
|
/// Converts a `Box<T>` into a `Pin<Box<T>>`
|
|
///
|
|
/// This conversion does not allocate on the heap and happens in place.
|
|
///
|
|
/// This is also available via [`From`].
|
|
#[unstable(feature = "box_into_pin", issue = "62370")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
pub const fn into_pin(boxed: Self) -> Pin<Self>
|
|
where
|
|
A: 'static,
|
|
{
|
|
// It's not possible to move or replace the insides of a `Pin<Box<T>>`
|
|
// when `T: !Unpin`, so it's safe to pin it directly without any
|
|
// additional requirements.
|
|
unsafe { Pin::new_unchecked(boxed) }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Box<T, A> {
|
|
fn drop(&mut self) {
|
|
// FIXME: Do nothing, drop is currently performed by compiler.
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: Default> Default for Box<T> {
|
|
/// Creates a `Box<T>`, with the `Default` value for T.
|
|
fn default() -> Self {
|
|
box T::default()
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
|
|
impl<T> const Default for Box<[T]> {
|
|
fn default() -> Self {
|
|
let ptr: Unique<[T]> = Unique::<[T; 0]>::dangling();
|
|
Box(ptr, Global)
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "default_box_extra", since = "1.17.0")]
|
|
#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
|
|
impl const Default for Box<str> {
|
|
fn default() -> Self {
|
|
// SAFETY: This is the same as `Unique::cast<U>` but with an unsized `U = str`.
|
|
let ptr: Unique<str> = unsafe {
|
|
let bytes: Unique<[u8]> = Unique::<[u8; 0]>::dangling();
|
|
Unique::new_unchecked(bytes.as_ptr() as *mut str)
|
|
};
|
|
Box(ptr, Global)
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A> {
|
|
/// Returns a new box with a `clone()` of this box's contents.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let x = Box::new(5);
|
|
/// let y = x.clone();
|
|
///
|
|
/// // The value is the same
|
|
/// assert_eq!(x, y);
|
|
///
|
|
/// // But they are unique objects
|
|
/// assert_ne!(&*x as *const i32, &*y as *const i32);
|
|
/// ```
|
|
#[inline]
|
|
fn clone(&self) -> Self {
|
|
// Pre-allocate memory to allow writing the cloned value directly.
|
|
let mut boxed = Self::new_uninit_in(self.1.clone());
|
|
unsafe {
|
|
(**self).write_clone_into_raw(boxed.as_mut_ptr());
|
|
boxed.assume_init()
|
|
}
|
|
}
|
|
|
|
/// Copies `source`'s contents into `self` without creating a new allocation.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// let x = Box::new(5);
|
|
/// let mut y = Box::new(10);
|
|
/// let yp: *const i32 = &*y;
|
|
///
|
|
/// y.clone_from(&x);
|
|
///
|
|
/// // The value is the same
|
|
/// assert_eq!(x, y);
|
|
///
|
|
/// // And no allocation occurred
|
|
/// assert_eq!(yp, &*y);
|
|
/// ```
|
|
#[inline]
|
|
fn clone_from(&mut self, source: &Self) {
|
|
(**self).clone_from(&(**source));
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "box_slice_clone", since = "1.3.0")]
|
|
impl Clone for Box<str> {
|
|
fn clone(&self) -> Self {
|
|
// this makes a copy of the data
|
|
let buf: Box<[u8]> = self.as_bytes().into();
|
|
unsafe { from_boxed_utf8_unchecked(buf) }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: ?Sized + PartialEq, A: Allocator> PartialEq for Box<T, A> {
|
|
#[inline]
|
|
fn eq(&self, other: &Self) -> bool {
|
|
PartialEq::eq(&**self, &**other)
|
|
}
|
|
#[inline]
|
|
fn ne(&self, other: &Self) -> bool {
|
|
PartialEq::ne(&**self, &**other)
|
|
}
|
|
}
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd for Box<T, A> {
|
|
#[inline]
|
|
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
|
|
PartialOrd::partial_cmp(&**self, &**other)
|
|
}
|
|
#[inline]
|
|
fn lt(&self, other: &Self) -> bool {
|
|
PartialOrd::lt(&**self, &**other)
|
|
}
|
|
#[inline]
|
|
fn le(&self, other: &Self) -> bool {
|
|
PartialOrd::le(&**self, &**other)
|
|
}
|
|
#[inline]
|
|
fn ge(&self, other: &Self) -> bool {
|
|
PartialOrd::ge(&**self, &**other)
|
|
}
|
|
#[inline]
|
|
fn gt(&self, other: &Self) -> bool {
|
|
PartialOrd::gt(&**self, &**other)
|
|
}
|
|
}
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A> {
|
|
#[inline]
|
|
fn cmp(&self, other: &Self) -> Ordering {
|
|
Ord::cmp(&**self, &**other)
|
|
}
|
|
}
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: ?Sized + Eq, A: Allocator> Eq for Box<T, A> {}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: ?Sized + Hash, A: Allocator> Hash for Box<T, A> {
|
|
fn hash<H: Hasher>(&self, state: &mut H) {
|
|
(**self).hash(state);
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "indirect_hasher_impl", since = "1.22.0")]
|
|
impl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A> {
|
|
fn finish(&self) -> u64 {
|
|
(**self).finish()
|
|
}
|
|
fn write(&mut self, bytes: &[u8]) {
|
|
(**self).write(bytes)
|
|
}
|
|
fn write_u8(&mut self, i: u8) {
|
|
(**self).write_u8(i)
|
|
}
|
|
fn write_u16(&mut self, i: u16) {
|
|
(**self).write_u16(i)
|
|
}
|
|
fn write_u32(&mut self, i: u32) {
|
|
(**self).write_u32(i)
|
|
}
|
|
fn write_u64(&mut self, i: u64) {
|
|
(**self).write_u64(i)
|
|
}
|
|
fn write_u128(&mut self, i: u128) {
|
|
(**self).write_u128(i)
|
|
}
|
|
fn write_usize(&mut self, i: usize) {
|
|
(**self).write_usize(i)
|
|
}
|
|
fn write_i8(&mut self, i: i8) {
|
|
(**self).write_i8(i)
|
|
}
|
|
fn write_i16(&mut self, i: i16) {
|
|
(**self).write_i16(i)
|
|
}
|
|
fn write_i32(&mut self, i: i32) {
|
|
(**self).write_i32(i)
|
|
}
|
|
fn write_i64(&mut self, i: i64) {
|
|
(**self).write_i64(i)
|
|
}
|
|
fn write_i128(&mut self, i: i128) {
|
|
(**self).write_i128(i)
|
|
}
|
|
fn write_isize(&mut self, i: isize) {
|
|
(**self).write_isize(i)
|
|
}
|
|
fn write_length_prefix(&mut self, len: usize) {
|
|
(**self).write_length_prefix(len)
|
|
}
|
|
fn write_str(&mut self, s: &str) {
|
|
(**self).write_str(s)
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "from_for_ptrs", since = "1.6.0")]
|
|
impl<T> From<T> for Box<T> {
|
|
/// Converts a `T` into a `Box<T>`
|
|
///
|
|
/// The conversion allocates on the heap and moves `t`
|
|
/// from the stack into it.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// let x = 5;
|
|
/// let boxed = Box::new(5);
|
|
///
|
|
/// assert_eq!(Box::from(x), boxed);
|
|
/// ```
|
|
fn from(t: T) -> Self {
|
|
Box::new(t)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "pin", since = "1.33.0")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
impl<T: ?Sized, A: Allocator> const From<Box<T, A>> for Pin<Box<T, A>>
|
|
where
|
|
A: 'static,
|
|
{
|
|
/// Converts a `Box<T>` into a `Pin<Box<T>>`
|
|
///
|
|
/// This conversion does not allocate on the heap and happens in place.
|
|
fn from(boxed: Box<T, A>) -> Self {
|
|
Box::into_pin(boxed)
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "box_from_slice", since = "1.17.0")]
|
|
impl<T: Copy> From<&[T]> for Box<[T]> {
|
|
/// Converts a `&[T]` into a `Box<[T]>`
|
|
///
|
|
/// This conversion allocates on the heap
|
|
/// and performs a copy of `slice`.
|
|
///
|
|
/// # Examples
|
|
/// ```rust
|
|
/// // create a &[u8] which will be used to create a Box<[u8]>
|
|
/// let slice: &[u8] = &[104, 101, 108, 108, 111];
|
|
/// let boxed_slice: Box<[u8]> = Box::from(slice);
|
|
///
|
|
/// println!("{boxed_slice:?}");
|
|
/// ```
|
|
fn from(slice: &[T]) -> Box<[T]> {
|
|
let len = slice.len();
|
|
let buf = RawVec::with_capacity(len);
|
|
unsafe {
|
|
ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
|
|
buf.into_box(slice.len()).assume_init()
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "box_from_cow", since = "1.45.0")]
|
|
impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
|
|
/// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
|
|
///
|
|
/// When `cow` is the `Cow::Borrowed` variant, this
|
|
/// conversion allocates on the heap and copies the
|
|
/// underlying slice. Otherwise, it will try to reuse the owned
|
|
/// `Vec`'s allocation.
|
|
#[inline]
|
|
fn from(cow: Cow<'_, [T]>) -> Box<[T]> {
|
|
match cow {
|
|
Cow::Borrowed(slice) => Box::from(slice),
|
|
Cow::Owned(slice) => Box::from(slice),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "box_from_slice", since = "1.17.0")]
|
|
impl From<&str> for Box<str> {
|
|
/// Converts a `&str` into a `Box<str>`
|
|
///
|
|
/// This conversion allocates on the heap
|
|
/// and performs a copy of `s`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// let boxed: Box<str> = Box::from("hello");
|
|
/// println!("{boxed}");
|
|
/// ```
|
|
#[inline]
|
|
fn from(s: &str) -> Box<str> {
|
|
unsafe { from_boxed_utf8_unchecked(Box::from(s.as_bytes())) }
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "box_from_cow", since = "1.45.0")]
|
|
impl From<Cow<'_, str>> for Box<str> {
|
|
/// Converts a `Cow<'_, str>` into a `Box<str>`
|
|
///
|
|
/// When `cow` is the `Cow::Borrowed` variant, this
|
|
/// conversion allocates on the heap and copies the
|
|
/// underlying `str`. Otherwise, it will try to reuse the owned
|
|
/// `String`'s allocation.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::borrow::Cow;
|
|
///
|
|
/// let unboxed = Cow::Borrowed("hello");
|
|
/// let boxed: Box<str> = Box::from(unboxed);
|
|
/// println!("{boxed}");
|
|
/// ```
|
|
///
|
|
/// ```rust
|
|
/// # use std::borrow::Cow;
|
|
/// let unboxed = Cow::Owned("hello".to_string());
|
|
/// let boxed: Box<str> = Box::from(unboxed);
|
|
/// println!("{boxed}");
|
|
/// ```
|
|
#[inline]
|
|
fn from(cow: Cow<'_, str>) -> Box<str> {
|
|
match cow {
|
|
Cow::Borrowed(s) => Box::from(s),
|
|
Cow::Owned(s) => Box::from(s),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "boxed_str_conv", since = "1.19.0")]
|
|
impl<A: Allocator> From<Box<str, A>> for Box<[u8], A> {
|
|
/// Converts a `Box<str>` into a `Box<[u8]>`
|
|
///
|
|
/// This conversion does not allocate on the heap and happens in place.
|
|
///
|
|
/// # Examples
|
|
/// ```rust
|
|
/// // create a Box<str> which will be used to create a Box<[u8]>
|
|
/// let boxed: Box<str> = Box::from("hello");
|
|
/// let boxed_str: Box<[u8]> = Box::from(boxed);
|
|
///
|
|
/// // create a &[u8] which will be used to create a Box<[u8]>
|
|
/// let slice: &[u8] = &[104, 101, 108, 108, 111];
|
|
/// let boxed_slice = Box::from(slice);
|
|
///
|
|
/// assert_eq!(boxed_slice, boxed_str);
|
|
/// ```
|
|
#[inline]
|
|
fn from(s: Box<str, A>) -> Self {
|
|
let (raw, alloc) = Box::into_raw_with_allocator(s);
|
|
unsafe { Box::from_raw_in(raw as *mut [u8], alloc) }
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "box_from_array", since = "1.45.0")]
|
|
impl<T, const N: usize> From<[T; N]> for Box<[T]> {
|
|
/// Converts a `[T; N]` into a `Box<[T]>`
|
|
///
|
|
/// This conversion moves the array to newly heap-allocated memory.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// let boxed: Box<[u8]> = Box::from([4, 2]);
|
|
/// println!("{boxed:?}");
|
|
/// ```
|
|
fn from(array: [T; N]) -> Box<[T]> {
|
|
box array
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
|
|
impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]> {
|
|
type Error = Box<[T]>;
|
|
|
|
/// Attempts to convert a `Box<[T]>` into a `Box<[T; N]>`.
|
|
///
|
|
/// The conversion occurs in-place and does not require a
|
|
/// new memory allocation.
|
|
///
|
|
/// # Errors
|
|
///
|
|
/// Returns the old `Box<[T]>` in the `Err` variant if
|
|
/// `boxed_slice.len()` does not equal `N`.
|
|
fn try_from(boxed_slice: Box<[T]>) -> Result<Self, Self::Error> {
|
|
if boxed_slice.len() == N {
|
|
Ok(unsafe { Box::from_raw(Box::into_raw(boxed_slice) as *mut [T; N]) })
|
|
} else {
|
|
Err(boxed_slice)
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<A: Allocator> Box<dyn Any, A> {
|
|
/// Attempt to downcast the box to a concrete type.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::any::Any;
|
|
///
|
|
/// fn print_if_string(value: Box<dyn Any>) {
|
|
/// if let Ok(string) = value.downcast::<String>() {
|
|
/// println!("String ({}): {}", string.len(), string);
|
|
/// }
|
|
/// }
|
|
///
|
|
/// let my_string = "Hello World".to_string();
|
|
/// print_if_string(Box::new(my_string));
|
|
/// print_if_string(Box::new(0i8));
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
|
|
if self.is::<T>() { unsafe { Ok(self.downcast_unchecked::<T>()) } } else { Err(self) }
|
|
}
|
|
|
|
/// Downcasts the box to a concrete type.
|
|
///
|
|
/// For a safe alternative see [`downcast`].
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(downcast_unchecked)]
|
|
///
|
|
/// use std::any::Any;
|
|
///
|
|
/// let x: Box<dyn Any> = Box::new(1_usize);
|
|
///
|
|
/// unsafe {
|
|
/// assert_eq!(*x.downcast_unchecked::<usize>(), 1);
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// The contained value must be of type `T`. Calling this method
|
|
/// with the incorrect type is *undefined behavior*.
|
|
///
|
|
/// [`downcast`]: Self::downcast
|
|
#[inline]
|
|
#[unstable(feature = "downcast_unchecked", issue = "90850")]
|
|
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A> {
|
|
debug_assert!(self.is::<T>());
|
|
unsafe {
|
|
let (raw, alloc): (*mut dyn Any, _) = Box::into_raw_with_allocator(self);
|
|
Box::from_raw_in(raw as *mut T, alloc)
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<A: Allocator> Box<dyn Any + Send, A> {
|
|
/// Attempt to downcast the box to a concrete type.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::any::Any;
|
|
///
|
|
/// fn print_if_string(value: Box<dyn Any + Send>) {
|
|
/// if let Ok(string) = value.downcast::<String>() {
|
|
/// println!("String ({}): {}", string.len(), string);
|
|
/// }
|
|
/// }
|
|
///
|
|
/// let my_string = "Hello World".to_string();
|
|
/// print_if_string(Box::new(my_string));
|
|
/// print_if_string(Box::new(0i8));
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
|
|
if self.is::<T>() { unsafe { Ok(self.downcast_unchecked::<T>()) } } else { Err(self) }
|
|
}
|
|
|
|
/// Downcasts the box to a concrete type.
|
|
///
|
|
/// For a safe alternative see [`downcast`].
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(downcast_unchecked)]
|
|
///
|
|
/// use std::any::Any;
|
|
///
|
|
/// let x: Box<dyn Any + Send> = Box::new(1_usize);
|
|
///
|
|
/// unsafe {
|
|
/// assert_eq!(*x.downcast_unchecked::<usize>(), 1);
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// The contained value must be of type `T`. Calling this method
|
|
/// with the incorrect type is *undefined behavior*.
|
|
///
|
|
/// [`downcast`]: Self::downcast
|
|
#[inline]
|
|
#[unstable(feature = "downcast_unchecked", issue = "90850")]
|
|
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A> {
|
|
debug_assert!(self.is::<T>());
|
|
unsafe {
|
|
let (raw, alloc): (*mut (dyn Any + Send), _) = Box::into_raw_with_allocator(self);
|
|
Box::from_raw_in(raw as *mut T, alloc)
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<A: Allocator> Box<dyn Any + Send + Sync, A> {
|
|
/// Attempt to downcast the box to a concrete type.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::any::Any;
|
|
///
|
|
/// fn print_if_string(value: Box<dyn Any + Send + Sync>) {
|
|
/// if let Ok(string) = value.downcast::<String>() {
|
|
/// println!("String ({}): {}", string.len(), string);
|
|
/// }
|
|
/// }
|
|
///
|
|
/// let my_string = "Hello World".to_string();
|
|
/// print_if_string(Box::new(my_string));
|
|
/// print_if_string(Box::new(0i8));
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "box_send_sync_any_downcast", since = "1.51.0")]
|
|
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
|
|
if self.is::<T>() { unsafe { Ok(self.downcast_unchecked::<T>()) } } else { Err(self) }
|
|
}
|
|
|
|
/// Downcasts the box to a concrete type.
|
|
///
|
|
/// For a safe alternative see [`downcast`].
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(downcast_unchecked)]
|
|
///
|
|
/// use std::any::Any;
|
|
///
|
|
/// let x: Box<dyn Any + Send + Sync> = Box::new(1_usize);
|
|
///
|
|
/// unsafe {
|
|
/// assert_eq!(*x.downcast_unchecked::<usize>(), 1);
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// The contained value must be of type `T`. Calling this method
|
|
/// with the incorrect type is *undefined behavior*.
|
|
///
|
|
/// [`downcast`]: Self::downcast
|
|
#[inline]
|
|
#[unstable(feature = "downcast_unchecked", issue = "90850")]
|
|
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A> {
|
|
debug_assert!(self.is::<T>());
|
|
unsafe {
|
|
let (raw, alloc): (*mut (dyn Any + Send + Sync), _) =
|
|
Box::into_raw_with_allocator(self);
|
|
Box::from_raw_in(raw as *mut T, alloc)
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: fmt::Display + ?Sized, A: Allocator> fmt::Display for Box<T, A> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
fmt::Display::fmt(&**self, f)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: fmt::Debug + ?Sized, A: Allocator> fmt::Debug for Box<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: ?Sized, A: Allocator> fmt::Pointer for Box<T, A> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
// It's not possible to extract the inner Uniq directly from the Box,
|
|
// instead we cast it to a *const which aliases the Unique
|
|
let ptr: *const T = &**self;
|
|
fmt::Pointer::fmt(&ptr, f)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> {
|
|
type Target = T;
|
|
|
|
fn deref(&self) -> &T {
|
|
&**self
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
impl<T: ?Sized, A: Allocator> const DerefMut for Box<T, A> {
|
|
fn deref_mut(&mut self) -> &mut T {
|
|
&mut **self
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "receiver_trait", issue = "none")]
|
|
impl<T: ?Sized, A: Allocator> Receiver for Box<T, A> {}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> {
|
|
type Item = I::Item;
|
|
fn next(&mut self) -> Option<I::Item> {
|
|
(**self).next()
|
|
}
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
(**self).size_hint()
|
|
}
|
|
fn nth(&mut self, n: usize) -> Option<I::Item> {
|
|
(**self).nth(n)
|
|
}
|
|
fn last(self) -> Option<I::Item> {
|
|
BoxIter::last(self)
|
|
}
|
|
}
|
|
|
|
trait BoxIter {
|
|
type Item;
|
|
fn last(self) -> Option<Self::Item>;
|
|
}
|
|
|
|
impl<I: Iterator + ?Sized, A: Allocator> BoxIter for Box<I, A> {
|
|
type Item = I::Item;
|
|
default fn last(self) -> Option<I::Item> {
|
|
#[inline]
|
|
fn some<T>(_: Option<T>, x: T) -> Option<T> {
|
|
Some(x)
|
|
}
|
|
|
|
self.fold(None, some)
|
|
}
|
|
}
|
|
|
|
/// Specialization for sized `I`s that uses `I`s implementation of `last()`
|
|
/// instead of the default.
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<I: Iterator, A: Allocator> BoxIter for Box<I, A> {
|
|
fn last(self) -> Option<I::Item> {
|
|
(*self).last()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A> {
|
|
fn next_back(&mut self) -> Option<I::Item> {
|
|
(**self).next_back()
|
|
}
|
|
fn nth_back(&mut self, n: usize) -> Option<I::Item> {
|
|
(**self).nth_back(n)
|
|
}
|
|
}
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A> {
|
|
fn len(&self) -> usize {
|
|
(**self).len()
|
|
}
|
|
fn is_empty(&self) -> bool {
|
|
(**self).is_empty()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "fused", since = "1.26.0")]
|
|
impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A> {}
|
|
|
|
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
|
|
impl<Args, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> {
|
|
type Output = <F as FnOnce<Args>>::Output;
|
|
|
|
extern "rust-call" fn call_once(self, args: Args) -> Self::Output {
|
|
<F as FnOnce<Args>>::call_once(*self, args)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
|
|
impl<Args, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> {
|
|
extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output {
|
|
<F as FnMut<Args>>::call_mut(self, args)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
|
|
impl<Args, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
|
|
extern "rust-call" fn call(&self, args: Args) -> Self::Output {
|
|
<F as Fn<Args>>::call(self, args)
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "coerce_unsized", issue = "27732")]
|
|
impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {}
|
|
|
|
#[unstable(feature = "dispatch_from_dyn", issue = "none")]
|
|
impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U>> for Box<T, Global> {}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "boxed_slice_from_iter", since = "1.32.0")]
|
|
impl<I> FromIterator<I> for Box<[I]> {
|
|
fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {
|
|
iter.into_iter().collect::<Vec<_>>().into_boxed_slice()
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "box_slice_clone", since = "1.3.0")]
|
|
impl<T: Clone, A: Allocator + Clone> Clone for Box<[T], A> {
|
|
fn clone(&self) -> Self {
|
|
let alloc = Box::allocator(self).clone();
|
|
self.to_vec_in(alloc).into_boxed_slice()
|
|
}
|
|
|
|
fn clone_from(&mut self, other: &Self) {
|
|
if self.len() == other.len() {
|
|
self.clone_from_slice(&other);
|
|
} else {
|
|
*self = other.clone();
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "box_borrow", since = "1.1.0")]
|
|
impl<T: ?Sized, A: Allocator> borrow::Borrow<T> for Box<T, A> {
|
|
fn borrow(&self) -> &T {
|
|
&**self
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "box_borrow", since = "1.1.0")]
|
|
impl<T: ?Sized, A: Allocator> borrow::BorrowMut<T> for Box<T, A> {
|
|
fn borrow_mut(&mut self) -> &mut T {
|
|
&mut **self
|
|
}
|
|
}
|
|
|
|
#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
|
|
impl<T: ?Sized, A: Allocator> AsRef<T> for Box<T, A> {
|
|
fn as_ref(&self) -> &T {
|
|
&**self
|
|
}
|
|
}
|
|
|
|
#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
|
|
impl<T: ?Sized, A: Allocator> AsMut<T> for Box<T, A> {
|
|
fn as_mut(&mut self) -> &mut T {
|
|
&mut **self
|
|
}
|
|
}
|
|
|
|
/* Nota bene
|
|
*
|
|
* We could have chosen not to add this impl, and instead have written a
|
|
* function of Pin<Box<T>> to Pin<T>. Such a function would not be sound,
|
|
* because Box<T> implements Unpin even when T does not, as a result of
|
|
* this impl.
|
|
*
|
|
* We chose this API instead of the alternative for a few reasons:
|
|
* - Logically, it is helpful to understand pinning in regard to the
|
|
* memory region being pointed to. For this reason none of the
|
|
* standard library pointer types support projecting through a pin
|
|
* (Box<T> is the only pointer type in std for which this would be
|
|
* safe.)
|
|
* - It is in practice very useful to have Box<T> be unconditionally
|
|
* Unpin because of trait objects, for which the structural auto
|
|
* trait functionality does not apply (e.g., Box<dyn Foo> would
|
|
* otherwise not be Unpin).
|
|
*
|
|
* Another type with the same semantics as Box but only a conditional
|
|
* implementation of `Unpin` (where `T: Unpin`) would be valid/safe, and
|
|
* could have a method to project a Pin<T> from it.
|
|
*/
|
|
#[stable(feature = "pin", since = "1.33.0")]
|
|
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
|
|
impl<T: ?Sized, A: Allocator> const Unpin for Box<T, A> where A: 'static {}
|
|
|
|
#[unstable(feature = "generator_trait", issue = "43122")]
|
|
impl<G: ?Sized + Generator<R> + Unpin, R, A: Allocator> Generator<R> for Box<G, A>
|
|
where
|
|
A: 'static,
|
|
{
|
|
type Yield = G::Yield;
|
|
type Return = G::Return;
|
|
|
|
fn resume(mut self: Pin<&mut Self>, arg: R) -> GeneratorState<Self::Yield, Self::Return> {
|
|
G::resume(Pin::new(&mut *self), arg)
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "generator_trait", issue = "43122")]
|
|
impl<G: ?Sized + Generator<R>, R, A: Allocator> Generator<R> for Pin<Box<G, A>>
|
|
where
|
|
A: 'static,
|
|
{
|
|
type Yield = G::Yield;
|
|
type Return = G::Return;
|
|
|
|
fn resume(mut self: Pin<&mut Self>, arg: R) -> GeneratorState<Self::Yield, Self::Return> {
|
|
G::resume((*self).as_mut(), arg)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "futures_api", since = "1.36.0")]
|
|
impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A>
|
|
where
|
|
A: 'static,
|
|
{
|
|
type Output = F::Output;
|
|
|
|
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
|
|
F::poll(Pin::new(&mut *self), cx)
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "async_iterator", issue = "79024")]
|
|
impl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S> {
|
|
type Item = S::Item;
|
|
|
|
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
|
|
Pin::new(&mut **self).poll_next(cx)
|
|
}
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
(**self).size_hint()
|
|
}
|
|
}
|