diff options
Diffstat (limited to 'rust/alloc/boxed.rs')
| -rw-r--r-- | rust/alloc/boxed.rs | 2463 |
1 files changed, 0 insertions, 2463 deletions
diff --git a/rust/alloc/boxed.rs b/rust/alloc/boxed.rs deleted file mode 100644 index c93a22a5c9..0000000000 --- a/rust/alloc/boxed.rs +++ /dev/null @@ -1,2463 +0,0 @@ -// SPDX-License-Identifier: Apache-2.0 OR MIT - -//! The `Box<T>` type for heap allocation. -//! -//! [`Box<T>`], casually referred to as a 'box', provides the simplest form of -//! heap allocation in Rust. Boxes provide ownership for this allocation, and -//! drop their contents when they go out of scope. Boxes also ensure that they -//! never allocate more than `isize::MAX` bytes. -//! -//! # Examples -//! -//! Move a value from the stack to the heap by creating a [`Box`]: -//! -//! ``` -//! let val: u8 = 5; -//! let boxed: Box<u8> = Box::new(val); -//! ``` -//! -//! Move a value from a [`Box`] back to the stack by [dereferencing]: -//! -//! ``` -//! let boxed: Box<u8> = Box::new(5); -//! let val: u8 = *boxed; -//! ``` -//! -//! Creating a recursive data structure: -//! -//! ``` -//! #[derive(Debug)] -//! enum List<T> { -//! Cons(T, Box<List<T>>), -//! Nil, -//! } -//! -//! let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil)))); -//! println!("{list:?}"); -//! ``` -//! -//! This will print `Cons(1, Cons(2, Nil))`. -//! -//! Recursive structures must be boxed, because if the definition of `Cons` -//! looked like this: -//! -//! ```compile_fail,E0072 -//! # enum List<T> { -//! Cons(T, List<T>), -//! # } -//! ``` -//! -//! It wouldn't work. This is because the size of a `List` depends on how many -//! elements are in the list, and so we don't know how much memory to allocate -//! for a `Cons`. By introducing a [`Box<T>`], which has a defined size, we know how -//! big `Cons` needs to be. -//! -//! # Memory layout -//! -//! For non-zero-sized values, a [`Box`] will use the [`Global`] allocator for -//! its allocation. It is valid to convert both ways between a [`Box`] and a -//! raw pointer allocated with the [`Global`] allocator, given that the -//! [`Layout`] used with the allocator is correct for the type. More precisely, -//! a `value: *mut T` that has been allocated with the [`Global`] allocator -//! with `Layout::for_value(&*value)` may be converted into a box using -//! [`Box::<T>::from_raw(value)`]. Conversely, the memory backing a `value: *mut -//! T` obtained from [`Box::<T>::into_raw`] may be deallocated using the -//! [`Global`] allocator with [`Layout::for_value(&*value)`]. -//! -//! For zero-sized values, the `Box` pointer still has to be [valid] for reads -//! and writes and sufficiently aligned. In particular, casting any aligned -//! non-zero integer literal to a raw pointer produces a valid pointer, but a -//! pointer pointing into previously allocated memory that since got freed is -//! not valid. The recommended way to build a Box to a ZST if `Box::new` cannot -//! be used is to use [`ptr::NonNull::dangling`]. -//! -//! So long as `T: Sized`, a `Box<T>` is guaranteed to be represented -//! as a single pointer and is also ABI-compatible with C pointers -//! (i.e. the C type `T*`). This means that if you have extern "C" -//! Rust functions that will be called from C, you can define those -//! Rust functions using `Box<T>` types, and use `T*` as corresponding -//! type on the C side. As an example, consider this C header which -//! declares functions that create and destroy some kind of `Foo` -//! value: -//! -//! ```c -//! /* C header */ -//! -//! /* Returns ownership to the caller */ -//! struct Foo* foo_new(void); -//! -//! /* Takes ownership from the caller; no-op when invoked with null */ -//! void foo_delete(struct Foo*); -//! ``` -//! -//! These two functions might be implemented in Rust as follows. Here, the -//! `struct Foo*` type from C is translated to `Box<Foo>`, which captures -//! the ownership constraints. Note also that the nullable argument to -//! `foo_delete` is represented in Rust as `Option<Box<Foo>>`, since `Box<Foo>` -//! cannot be null. -//! -//! ``` -//! #[repr(C)] -//! pub struct Foo; -//! -//! #[no_mangle] -//! pub extern "C" fn foo_new() -> Box<Foo> { -//! Box::new(Foo) -//! } -//! -//! #[no_mangle] -//! pub extern "C" fn foo_delete(_: Option<Box<Foo>>) {} -//! ``` -//! -//! Even though `Box<T>` has the same representation and C ABI as a C pointer, -//! this does not mean that you can convert an arbitrary `T*` into a `Box<T>` -//! and expect things to work. `Box<T>` values will always be fully aligned, -//! non-null pointers. Moreover, the destructor for `Box<T>` will attempt to -//! free the value with the global allocator. In general, the best practice -//! is to only use `Box<T>` for pointers that originated from the global -//! allocator. -//! -//! **Important.** At least at present, you should avoid using -//! `Box<T>` types for functions that are defined in C but invoked -//! from Rust. In those cases, you should directly mirror the C types -//! as closely as possible. Using types like `Box<T>` where the C -//! definition is just using `T*` can lead to undefined behavior, as -//! described in [rust-lang/unsafe-code-guidelines#198][ucg#198]. -//! -//! # Considerations for unsafe code -//! -//! **Warning: This section is not normative and is subject to change, possibly -//! being relaxed in the future! It is a simplified summary of the rules -//! currently implemented in the compiler.** -//! -//! The aliasing rules for `Box<T>` are the same as for `&mut T`. `Box<T>` -//! asserts uniqueness over its content. Using raw pointers derived from a box -//! after that box has been mutated through, moved or borrowed as `&mut T` -//! is not allowed. For more guidance on working with box from unsafe code, see -//! [rust-lang/unsafe-code-guidelines#326][ucg#326]. -//! -//! -//! [ucg#198]: https://github.com/rust-lang/unsafe-code-guidelines/issues/198 -//! [ucg#326]: https://github.com/rust-lang/unsafe-code-guidelines/issues/326 -//! [dereferencing]: core::ops::Deref -//! [`Box::<T>::from_raw(value)`]: Box::from_raw -//! [`Global`]: crate::alloc::Global -//! [`Layout`]: crate::alloc::Layout -//! [`Layout::for_value(&*value)`]: crate::alloc::Layout::for_value -//! [valid]: ptr#safety - -#![stable(feature = "rust1", since = "1.0.0")] - -use core::any::Any; -use core::async_iter::AsyncIterator; -use core::borrow; -use core::cmp::Ordering; -use core::error::Error; -use core::fmt; -use core::future::Future; -use core::hash::{Hash, Hasher}; -use core::iter::FusedIterator; -use core::marker::Tuple; -use core::marker::Unsize; -use core::mem::{self, SizedTypeProperties}; -use core::ops::{ - CoerceUnsized, Coroutine, CoroutineState, Deref, DerefMut, DispatchFromDyn, Receiver, -}; -use core::pin::Pin; -use core::ptr::{self, NonNull, Unique}; -use core::task::{Context, Poll}; - -#[cfg(not(no_global_oom_handling))] -use crate::alloc::{handle_alloc_error, WriteCloneIntoRaw}; -use crate::alloc::{AllocError, Allocator, Global, Layout}; -#[cfg(not(no_global_oom_handling))] -use crate::borrow::Cow; -use crate::raw_vec::RawVec; -#[cfg(not(no_global_oom_handling))] -use crate::str::from_boxed_utf8_unchecked; -#[cfg(not(no_global_oom_handling))] -use crate::string::String; -#[cfg(not(no_global_oom_handling))] -use crate::vec::Vec; - -#[cfg(not(no_thin))] -#[unstable(feature = "thin_box", issue = "92791")] -pub use thin::ThinBox; - -#[cfg(not(no_thin))] -mod thin; - -/// A pointer type that uniquely owns a heap allocation of type `T`. -/// -/// See the [module-level documentation](../../std/boxed/index.html) for more. -#[lang = "owned_box"] -#[fundamental] -#[stable(feature = "rust1", since = "1.0.0")] -// The declaration of the `Box` struct must be kept in sync with the -// `alloc::alloc::box_free` function or ICEs will happen. See the comment -// on `box_free` for more details. -pub struct Box< - T: ?Sized, - #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, ->(Unique<T>, A); - -impl<T> Box<T> { - /// Allocates memory on the heap and then places `x` into it. - /// - /// This doesn't actually allocate if `T` is zero-sized. - /// - /// # Examples - /// - /// ``` - /// let five = Box::new(5); - /// ``` - #[cfg(not(no_global_oom_handling))] - #[inline(always)] - #[stable(feature = "rust1", since = "1.0.0")] - #[must_use] - #[rustc_diagnostic_item = "box_new"] - pub fn new(x: T) -> Self { - #[rustc_box] - Box::new(x) - } - - /// Constructs a new box with uninitialized contents. - /// - /// # Examples - /// - /// ``` - /// #![feature(new_uninit)] - /// - /// let mut five = Box::<u32>::new_uninit(); - /// - /// let five = unsafe { - /// // Deferred initialization: - /// five.as_mut_ptr().write(5); - /// - /// five.assume_init() - /// }; - /// - /// assert_eq!(*five, 5) - /// ``` - #[cfg(not(no_global_oom_handling))] - #[unstable(feature = "new_uninit", issue = "63291")] - #[must_use] - #[inline] - pub fn new_uninit() -> Box<mem::MaybeUninit<T>> { - Self::new_uninit_in(Global) - } - - /// Constructs a new `Box` 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 zero = Box::<u32>::new_zeroed(); - /// let zero = unsafe { zero.assume_init() }; - /// - /// assert_eq!(*zero, 0) - /// ``` - /// - /// [zeroed]: mem::MaybeUninit::zeroed - #[cfg(not(no_global_oom_handling))] - #[inline] - #[unstable(feature = "new_uninit", issue = "63291")] - #[must_use] - pub fn new_zeroed() -> Box<mem::MaybeUninit<T>> { - Self::new_zeroed_in(Global) - } - - /// Constructs a new `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then - /// `x` will be pinned in memory and unable to be moved. - /// - /// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin(x)` - /// does the same as <code>[Box::into_pin]\([Box::new]\(x))</code>. Consider using - /// [`into_pin`](Box::into_pin) if you already have a `Box<T>`, or if you want to - /// construct a (pinned) `Box` in a different way than with [`Box::new`]. - #[cfg(not(no_global_oom_handling))] - #[stable(feature = "pin", since = "1.33.0")] - #[must_use] - #[inline(always)] - pub fn pin(x: T) -> Pin<Box<T>> { - Box::new(x).into() - } - - /// Allocates memory on the heap then places `x` into it, - /// returning an error if the allocation fails - /// - /// This doesn't actually allocate if `T` is zero-sized. - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api)] - /// - /// let five = Box::try_new(5)?; - /// # Ok::<(), std::alloc::AllocError>(()) - /// ``` - #[unstable(feature = "allocator_api", issue = "32838")] - #[inline] - pub fn try_new(x: T) -> Result<Self, AllocError> { - Self::try_new_in(x, Global) - } - - /// Constructs a new box with uninitialized contents on the heap, - /// returning an error if the allocation fails - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api, new_uninit)] - /// - /// let mut five = Box::<u32>::try_new_uninit()?; - /// - /// let five = unsafe { - /// // Deferred initialization: - /// five.as_mut_ptr().write(5); - /// - /// five.assume_init() - /// }; - /// - /// assert_eq!(*five, 5); - /// # Ok::<(), std::alloc::AllocError>(()) - /// ``` - #[unstable(feature = "allocator_api", issue = "32838")] - // #[unstable(feature = "new_uninit", issue = "63291")] - #[inline] - pub fn try_new_uninit() -> Result<Box<mem::MaybeUninit<T>>, AllocError> { - Box::try_new_uninit_in(Global) - } - - /// Constructs a new `Box` with uninitialized contents, with the memory - /// being filled with `0` bytes on the heap - /// - /// See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage - /// of this method. - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api, new_uninit)] - /// - /// let zero = Box::<u32>::try_new_zeroed()?; - /// 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")] - #[inline] - pub fn try_new_zeroed() -> Result<Box<mem::MaybeUninit<T>>, AllocError> { - Box::try_new_zeroed_in(Global) - } -} - -impl<T, A: Allocator> Box<T, A> { - /// Allocates memory in the given allocator then places `x` into it. - /// - /// This doesn't actually allocate if `T` is zero-sized. - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api)] - /// - /// use std::alloc::System; - /// - /// let five = Box::new_in(5, System); - /// ``` - #[cfg(not(no_global_oom_handling))] - #[unstable(feature = "allocator_api", issue = "32838")] - #[must_use] - #[inline] - pub fn new_in(x: T, alloc: A) -> Self - where - A: Allocator, - { - let mut boxed = Self::new_uninit_in(alloc); - unsafe { - boxed.as_mut_ptr().write(x); - boxed.assume_init() - } - } - - /// Allocates memory in the given allocator then places `x` into it, - /// returning an error if the allocation fails - /// - /// This doesn't actually allocate if `T` is zero-sized. - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api)] - /// - /// use std::alloc::System; - /// - /// let five = Box::try_new_in(5, System)?; - /// # Ok::<(), std::alloc::AllocError>(()) - /// ``` - #[unstable(feature = "allocator_api", issue = "32838")] - #[inline] - pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError> - where - A: Allocator, - { - let mut boxed = Self::try_new_uninit_in(alloc)?; - unsafe { - boxed.as_mut_ptr().write(x); - Ok(boxed.assume_init()) - } - } - - /// Constructs a new box with uninitialized contents in the provided allocator. - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api, new_uninit)] - /// - /// use std::alloc::System; - /// - /// let mut five = Box::<u32, _>::new_uninit_in(System); - /// - /// let five = unsafe { - /// // Deferred initialization: - /// five.as_mut_ptr().write(5); - /// - /// five.assume_init() - /// }; - /// - /// assert_eq!(*five, 5) - /// ``` - #[unstable(feature = "allocator_api", issue = "32838")] - #[cfg(not(no_global_oom_handling))] - #[must_use] - // #[unstable(feature = "new_uninit", issue = "63291")] - pub fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> - where - A: Allocator, - { - 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_uninit_in(alloc) { - Ok(m) => m, - Err(_) => handle_alloc_error(layout), - } - } - - /// Constructs a new box with uninitialized contents in the provided allocator, - /// returning an error if the allocation fails - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api, new_uninit)] - /// - /// use std::alloc::System; - /// - /// let mut five = Box::<u32, _>::try_new_uninit_in(System)?; - /// - /// let five = unsafe { - /// // Deferred initialization: - /// five.as_mut_ptr().write(5); - /// - /// five.assume_init() - /// }; - /// - /// assert_eq!(*five, 5); - /// # Ok::<(), std::alloc::AllocError>(()) - /// ``` - #[unstable(feature = "allocator_api", issue = "32838")] - // #[unstable(feature = "new_uninit", issue = "63291")] - pub fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> - where - A: Allocator, - { - let ptr = if T::IS_ZST { - NonNull::dangling() - } else { - let layout = Layout::new::<mem::MaybeUninit<T>>(); - alloc.allocate(layout)?.cast() - }; - unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) } - } - - /// Constructs a new `Box` with uninitialized contents, with the memory - /// being filled with `0` bytes in the provided allocator. - /// - /// 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, _>::new_zeroed_in(System); - /// let zero = unsafe { zero.assume_init() }; - /// - /// assert_eq!(*zero, 0) - /// ``` - /// - /// [zeroed]: mem::MaybeUninit::zeroed - #[unstable(feature = "allocator_api", issue = "32838")] - #[cfg(not(no_global_oom_handling))] - // #[unstable(feature = "new_uninit", issue = "63291")] - #[must_use] - pub fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> - where - A: Allocator, - { - 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")] - pub fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError> - where - A: Allocator, - { - let ptr = if T::IS_ZST { - NonNull::dangling() - } else { - let layout = Layout::new::<mem::MaybeUninit<T>>(); - 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. - /// - /// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin_in(x, alloc)` - /// does the same as <code>[Box::into_pin]\([Box::new_in]\(x, alloc))</code>. Consider using - /// [`into_pin`](Box::into_pin) if you already have a `Box<T, A>`, or if you want to - /// construct a (pinned) `Box` in a different way than with [`Box::new_in`]. - #[cfg(not(no_global_oom_handling))] - #[unstable(feature = "allocator_api", issue = "32838")] - #[must_use] - #[inline(always)] - pub fn pin_in(x: T, alloc: A) -> Pin<Self> - where - A: 'static + Allocator, - { - 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")] - pub 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")] - #[inline] - pub fn into_inner(boxed: Self) -> T { - *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> { - let ptr = if T::IS_ZST || len == 0 { - NonNull::dangling() - } else { - let layout = match Layout::array::<mem::MaybeUninit<T>>(len) { - Ok(l) => l, - Err(_) => return Err(AllocError), - }; - Global.allocate(layout)?.cast() - }; - unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), 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> { - let ptr = if T::IS_ZST || len == 0 { - NonNull::dangling() - } else { - let layout = match Layout::array::<mem::MaybeUninit<T>>(len) { - Ok(l) => l, - Err(_) => return Err(AllocError), - }; - Global.allocate_zeroed(layout)?.cast() - }; - unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), 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")] - #[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) } - } - - /// 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")] - #[inline] - pub 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] - #[must_use = "call `drop(Box::from_raw(ptr))` if you intend to drop the `Box`"] - 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 ptr = Box::into_raw(x); - /// unsafe { - /// ptr::drop_in_place(ptr); - /// dealloc(ptr as *mut u8, Layout::new::<String>()); - /// } - /// ``` - /// Note: This is equivalent to the following: - /// ``` - /// let x = Box::new(String::from("Hello")); - /// let ptr = Box::into_raw(x); - /// unsafe { - /// drop(Box::from_raw(ptr)); - /// } - /// ``` - /// - /// [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")] - #[inline] - pub 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" - )] - #[inline] - #[doc(hidden)] - pub 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")] - #[inline] - pub 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>>`. If `T` does not implement [`Unpin`], then - /// `*boxed` will be pinned in memory and unable to be moved. - /// - /// This conversion does not allocate on the heap and happens in place. - /// - /// This is also available via [`From`]. - /// - /// Constructing and pinning a `Box` with <code>Box::into_pin([Box::new]\(x))</code> - /// can also be written more concisely using <code>[Box::pin]\(x)</code>. - /// This `into_pin` method is useful if you already have a `Box<T>`, or you are - /// constructing a (pinned) `Box` in a different way than with [`Box::new`]. - /// - /// # Notes - /// - /// It's not recommended that crates add an impl like `From<Box<T>> for Pin<T>`, - /// as it'll introduce an ambiguity when calling `Pin::from`. - /// A demonstration of such a poor impl is shown below. - /// - /// ```compile_fail - /// # use std::pin::Pin; - /// struct Foo; // A type defined in this crate. - /// impl From<Box<()>> for Pin<Foo> { - /// fn from(_: Box<()>) -> Pin<Foo> { - /// Pin::new(Foo) - /// } - /// } - /// - /// let foo = Box::new(()); - /// let bar = Pin::from(foo); - /// ``` - #[stable(feature = "box_into_pin", since = "1.63.0")] - #[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> { - #[inline] - fn drop(&mut self) { - // the T in the Box is dropped by the compiler before the destructor is run - - let ptr = self.0; - - unsafe { - let layout = Layout::for_value_raw(ptr.as_ptr()); - if layout.size() != 0 { - self.1.deallocate(From::from(ptr.cast()), layout); - } - } - } -} - -#[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. - #[inline] - fn default() -> Self { - Box::new(T::default()) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> Default for Box<[T]> { - #[inline] - 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")] -impl Default for Box<str> { - #[inline] - 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")] -impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>> -where - A: 'static, -{ - /// Converts a `Box<T>` into a `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then - /// `*boxed` will be pinned in memory and unable to be moved. - /// - /// This conversion does not allocate on the heap and happens in place. - /// - /// This is also available via [`Box::into_pin`]. - /// - /// Constructing and pinning a `Box` with <code><Pin<Box\<T>>>::from([Box::new]\(x))</code> - /// can also be written more concisely using <code>[Box::pin]\(x)</code>. - /// This `From` implementation is useful if you already have a `Box<T>`, or you are - /// constructing a (pinned) `Box` in a different way than with [`Box::new`]. - fn from(boxed: Box<T, A>) -> Self { - Box::into_pin(boxed) - } -} - -/// Specialization trait used for `From<&[T]>`. -#[cfg(not(no_global_oom_handling))] -trait BoxFromSlice<T> { - fn from_slice(slice: &[T]) -> Self; -} - -#[cfg(not(no_global_oom_handling))] -impl<T: Clone> BoxFromSlice<T> for Box<[T]> { - #[inline] - default fn from_slice(slice: &[T]) -> Self { - slice.to_vec().into_boxed_slice() - } -} - -#[cfg(not(no_global_oom_handling))] -impl<T: Copy> BoxFromSlice<T> for Box<[T]> { - #[inline] - fn from_slice(slice: &[T]) -> Self { - 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_slice", since = "1.17.0")] -impl<T: Clone> From<&[T]> for Box<[T]> { - /// Converts a `&[T]` into a `Box<[T]>` - /// - /// This conversion allocates on the heap - /// and performs a copy of `slice` and its contents. - /// - /// # 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:?}"); - /// ``` - #[inline] - fn from(slice: &[T]) -> Box<[T]> { - <Self as BoxFromSlice<T>>::from_slice(slice) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "box_from_cow", since = "1.45.0")] -impl<T: Clone> 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::new(array) - } -} - -/// Casts a boxed slice to a boxed array. -/// -/// # Safety -/// -/// `boxed_slice.len()` must be exactly `N`. -unsafe fn boxed_slice_as_array_unchecked<T, A: Allocator, const N: usize>( - boxed_slice: Box<[T], A>, -) -> Box<[T; N], A> { - debug_assert_eq!(boxed_slice.len(), N); - - let (ptr, alloc) = Box::into_raw_with_allocator(boxed_slice); - // SAFETY: Pointer and allocator came from an existing box, - // and our safety condition requires that the length is exactly `N` - unsafe { Box::from_raw_in(ptr as *mut [T; N], alloc) } -} - -#[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 { boxed_slice_as_array_unchecked(boxed_slice) }) - } else { - Err(boxed_slice) - } - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "boxed_array_try_from_vec", since = "1.66.0")] -impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]> { - type Error = Vec<T>; - - /// Attempts to convert a `Vec<T>` into a `Box<[T; N]>`. - /// - /// Like [`Vec::into_boxed_slice`], this is in-place if `vec.capacity() == N`, - /// but will require a reallocation otherwise. - /// - /// # Errors - /// - /// Returns the original `Vec<T>` in the `Err` variant if - /// `boxed_slice.len()` does not equal `N`. - /// - /// # Examples - /// - /// This can be used with [`vec!`] to create an array on the heap: - /// - /// ``` - /// let state: Box<[f32; 100]> = vec![1.0; 100].try_into().unwrap(); - /// assert_eq!(state.len(), 100); - /// ``` - fn try_from(vec: Vec<T>) -> Result<Self, Self::Error> { - if vec.len() == N { - let boxed_slice = vec.into_boxed_slice(); - Ok(unsafe { boxed_slice_as_array_unchecked(boxed_slice) }) - } else { - Err(vec) - } - } -} - -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")] -impl<T: ?Sized, A: Allocator> Deref for Box<T, A> { - type Target = T; - - fn deref(&self) -> &T { - &**self - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: ?Sized, A: Allocator> 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: Tuple, 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: Tuple, 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: Tuple, 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 = "18598")] -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")] -impl<T: ?Sized, A: Allocator> Unpin for Box<T, A> where A: 'static {} - -#[unstable(feature = "coroutine_trait", issue = "43122")] -impl<G: ?Sized + Coroutine<R> + Unpin, R, A: Allocator> Coroutine<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) -> CoroutineState<Self::Yield, Self::Return> { - G::resume(Pin::new(&mut *self), arg) - } -} - -#[unstable(feature = "coroutine_trait", issue = "43122")] -impl<G: ?Sized + Coroutine<R>, R, A: Allocator> Coroutine<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) -> CoroutineState<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() - } -} - -impl dyn Error { - #[inline] - #[stable(feature = "error_downcast", since = "1.3.0")] - #[rustc_allow_incoherent_impl] - /// Attempts to downcast the box to a concrete type. - pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error>> { - if self.is::<T>() { - unsafe { - let raw: *mut dyn Error = Box::into_raw(self); - Ok(Box::from_raw(raw as *mut T)) - } - } else { - Err(self) - } - } -} - -impl dyn Error + Send { - #[inline] - #[stable(feature = "error_downcast", since = "1.3.0")] - #[rustc_allow_incoherent_impl] - /// Attempts to downcast the box to a concrete type. - pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error + Send>> { - let err: Box<dyn Error> = self; - <dyn Error>::downcast(err).map_err(|s| unsafe { - // Reapply the `Send` marker. - Box::from_raw(Box::into_raw(s) as *mut (dyn Error + Send)) - }) - } -} - -impl dyn Error + Send + Sync { - #[inline] - #[stable(feature = "error_downcast", since = "1.3.0")] - #[rustc_allow_incoherent_impl] - /// Attempts to downcast the box to a concrete type. - pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Self>> { - let err: Box<dyn Error> = self; - <dyn Error>::downcast(err).map_err(|s| unsafe { - // Reapply the `Send + Sync` marker. - Box::from_raw(Box::into_raw(s) as *mut (dyn Error + Send + Sync)) - }) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> { - /// Converts a type of [`Error`] into a box of dyn [`Error`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::fmt; - /// use std::mem; - /// - /// #[derive(Debug)] - /// struct AnError; - /// - /// impl fmt::Display for AnError { - /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - /// write!(f, "An error") - /// } - /// } - /// - /// impl Error for AnError {} - /// - /// let an_error = AnError; - /// assert!(0 == mem::size_of_val(&an_error)); - /// let a_boxed_error = Box::<dyn Error>::from(an_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: E) -> Box<dyn Error + 'a> { - Box::new(err) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> { - /// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of - /// dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::fmt; - /// use std::mem; - /// - /// #[derive(Debug)] - /// struct AnError; - /// - /// impl fmt::Display for AnError { - /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - /// write!(f, "An error") - /// } - /// } - /// - /// impl Error for AnError {} - /// - /// unsafe impl Send for AnError {} - /// - /// unsafe impl Sync for AnError {} - /// - /// let an_error = AnError; - /// assert!(0 == mem::size_of_val(&an_error)); - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> { - Box::new(err) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "rust1", since = "1.0.0")] -impl From<String> for Box<dyn Error + Send + Sync> { - /// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_string_error = "a string error".to_string(); - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - #[inline] - fn from(err: String) -> Box<dyn Error + Send + Sync> { - struct StringError(String); - - impl Error for StringError { - #[allow(deprecated)] - fn description(&self) -> &str { - &self.0 - } - } - - impl fmt::Display for StringError { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Display::fmt(&self.0, f) - } - } - - // Purposefully skip printing "StringError(..)" - impl fmt::Debug for StringError { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&self.0, f) - } - } - - Box::new(StringError(err)) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "string_box_error", since = "1.6.0")] -impl From<String> for Box<dyn Error> { - /// Converts a [`String`] into a box of dyn [`Error`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_string_error = "a string error".to_string(); - /// let a_boxed_error = Box::<dyn Error>::from(a_string_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(str_err: String) -> Box<dyn Error> { - let err1: Box<dyn Error + Send + Sync> = From::from(str_err); - let err2: Box<dyn Error> = err1; - err2 - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> { - /// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// [`str`]: prim@str - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_str_error = "a str error"; - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - #[inline] - fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a> { - From::from(String::from(err)) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "string_box_error", since = "1.6.0")] -impl From<&str> for Box<dyn Error> { - /// Converts a [`str`] into a box of dyn [`Error`]. - /// - /// [`str`]: prim@str - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_str_error = "a str error"; - /// let a_boxed_error = Box::<dyn Error>::from(a_str_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: &str) -> Box<dyn Error> { - From::from(String::from(err)) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "cow_box_error", since = "1.22.0")] -impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> { - /// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// use std::borrow::Cow; - /// - /// let a_cow_str_error = Cow::from("a str error"); - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> { - From::from(String::from(err)) - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "cow_box_error", since = "1.22.0")] -impl<'a> From<Cow<'a, str>> for Box<dyn Error> { - /// Converts a [`Cow`] into a box of dyn [`Error`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// use std::borrow::Cow; - /// - /// let a_cow_str_error = Cow::from("a str error"); - /// let a_boxed_error = Box::<dyn Error>::from(a_cow_str_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: Cow<'a, str>) -> Box<dyn Error> { - From::from(String::from(err)) - } -} - -#[stable(feature = "box_error", since = "1.8.0")] -impl<T: core::error::Error> core::error::Error for Box<T> { - #[allow(deprecated, deprecated_in_future)] - fn description(&self) -> &str { - core::error::Error::description(&**self) - } - - #[allow(deprecated)] - fn cause(&self) -> Option<&dyn core::error::Error> { - core::error::Error::cause(&**self) - } - - fn source(&self) -> Option<&(dyn core::error::Error + 'static)> { - core::error::Error::source(&**self) - } - - fn provide<'b>(&'b self, request: &mut core::error::Request<'b>) { - core::error::Error::provide(&**self, request); - } -} |