Struct std::boxed::Box

impl<T> Box<T>

pub fn new(x: 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);

pub fn new_uninit() -> Box<MaybeUninit<T>>

🔬This is a nightly-only experimental API. (new_uninit #63291)

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)

pub fn new_zeroed() -> Box<MaybeUninit<T>>

🔬This is a nightly-only experimental API. (new_uninit #63291)

Constructs a new Box with uninitialized contents, with the memory being filled with 0 bytes.

See MaybeUninit::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)

1.33.0 · source

pub fn pin(x: T) -> Pin<Box<T>>

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 Box::into_pin(Box::new(x)). Consider using 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.

pub fn try_new(x: T) -> Result<Box<T>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api #32838)

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)?;

pub fn try_new_uninit() -> Result<Box<MaybeUninit<T>>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api #32838)

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);

pub fn try_new_zeroed() -> Result<Box<MaybeUninit<T>>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api #32838)

Constructs a new Box with uninitialized contents, with the memory being filled with 0 bytes on the heap

See MaybeUninit::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);

impl<T, A> Box<T, A>
where A: Allocator,

pub fn new_in(x: T, alloc: A) -> Box<T, A>
where A: Allocator,

🔬This is a nightly-only experimental API. (allocator_api #32838)

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);

pub fn try_new_in(x: T, alloc: A) -> Result<Box<T, A>, AllocError>
where A: Allocator,

🔬This is a nightly-only experimental API. (allocator_api #32838)

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)?;

pub fn new_uninit_in(alloc: A) -> Box<MaybeUninit<T>, A>
where A: Allocator,

🔬This is a nightly-only experimental API. (allocator_api #32838)

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)

pub fn try_new_uninit_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError>
where A: Allocator,

🔬This is a nightly-only experimental API. (allocator_api #32838)

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);

pub fn new_zeroed_in(alloc: A) -> Box<MaybeUninit<T>, A>
where A: Allocator,

🔬This is a nightly-only experimental API. (allocator_api #32838)

Constructs a new Box with uninitialized contents, with the memory being filled with 0 bytes in the provided allocator.

See MaybeUninit::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)

pub fn try_new_zeroed_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError>
where A: Allocator,

🔬This is a nightly-only experimental API. (allocator_api #32838)

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 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);

pub fn pin_in(x: T, alloc: A) -> Pin<Box<T, A>>
where A: 'static + Allocator,

🔬This is a nightly-only experimental API. (allocator_api #32838)

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 Box::into_pin(Box::new_in(x, alloc)). Consider using 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.

pub fn into_boxed_slice(boxed: Box<T, A>) -> Box<[T], A>

🔬This is a nightly-only experimental API. (box_into_boxed_slice #71582)

Converts a Box<T> into a Box<[T]>

This conversion does not allocate on the heap and happens in place.

pub fn into_inner(boxed: Box<T, A>) -> T

🔬This is a nightly-only experimental API. (box_into_inner #80437)

Consumes the Box, returning the wrapped value.

§Examples

#![feature(box_into_inner)]

let c = Box::new(5);

assert_eq!(Box::into_inner(c), 5);

impl<T> Box<[T]>

pub fn new_uninit_slice(len: usize) -> Box<[MaybeUninit<T>]>

🔬This is a nightly-only experimental API. (new_uninit #63291)

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])

pub fn new_zeroed_slice(len: usize) -> Box<[MaybeUninit<T>]>

🔬This is a nightly-only experimental API. (new_uninit #63291)

Constructs a new boxed slice with uninitialized contents, with the memory being filled with 0 bytes.

See MaybeUninit::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])

pub fn try_new_uninit_slice( len: usize ) -> Result<Box<[MaybeUninit<T>]>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api #32838)

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]);

pub fn try_new_zeroed_slice( len: usize ) -> Result<Box<[MaybeUninit<T>]>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api #32838)

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 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]);

impl<T, A> Box<[T], A>
where A: Allocator,

pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>

🔬This is a nightly-only experimental API. (allocator_api #32838)

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])

pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>

🔬This is a nightly-only experimental API. (allocator_api #32838)

Constructs a new boxed slice with uninitialized contents in the provided allocator, with the memory being filled with 0 bytes.

See MaybeUninit::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])

impl<T, A> Box<MaybeUninit<T>, A>
where A: Allocator,

pub unsafe fn assume_init(self) -> Box<T, A>

🔬This is a nightly-only experimental API. (new_uninit #63291)

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.

§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)

pub fn write(boxed: Box<MaybeUninit<T>, A>, value: T) -> Box<T, A>

🔬This is a nightly-only experimental API. (new_uninit #63291)

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);
}

impl<T, A> Box<[MaybeUninit<T>], A>
where A: Allocator,

pub unsafe fn assume_init(self) -> Box<[T], A>

🔬This is a nightly-only experimental API. (new_uninit #63291)

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.

§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])

impl<T> Box<T>
where T: ?Sized,

1.4.0 · source

pub unsafe fn from_raw(raw: *mut T) -> 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);
}

impl<T, A> Box<T, A>
where A: Allocator, T: ?Sized,

const: unstable · source

pub unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Box<T, A>

🔬This is a nightly-only experimental API. (allocator_api #32838)

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);
}

1.4.0 · source

pub fn into_raw(b: Box<T, A>) -> *mut T

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));
}

pub fn into_raw_with_allocator(b: Box<T, A>) -> (*mut T, A)

🔬This is a nightly-only experimental API. (allocator_api #32838)

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>());
}

const: unstable · source

pub fn allocator(b: &Box<T, A>) -> &A

🔬This is a nightly-only experimental API. (allocator_api #32838)

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.

1.26.0 · source

pub fn leak<'a>(b: Box<T, A>) -> &'a mut T
where A: 'a,

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]);

1.63.0 (const: unstable) · source

pub fn into_pin(boxed: Box<T, A>) -> 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 From.

Constructing and pinning a Box with Box::into_pin(Box::new(x)) can also be written more concisely using Box::pin(x). 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.

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);

impl<A> Box<dyn Any, A>
where A: Allocator,

pub fn downcast<T>(self) -> Result<Box<T, A>, Box<dyn Any, A>>
where T: Any,

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));

pub unsafe fn downcast_unchecked<T>(self) -> Box<T, A>
where T: Any,

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

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.

impl<A> Box<dyn Any + Send, A>
where A: Allocator,

pub fn downcast<T>(self) -> Result<Box<T, A>, Box<dyn Any + Send, A>>
where T: Any,

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));

pub unsafe fn downcast_unchecked<T>(self) -> Box<T, A>
where T: Any,

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

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.

impl<A> Box<dyn Any + Sync + Send, A>
where A: Allocator,

1.51.0 · source

pub fn downcast<T>(self) -> Result<Box<T, A>, Box<dyn Any + Sync + Send, A>>
where T: Any,

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));

pub unsafe fn downcast_unchecked<T>(self) -> Box<T, A>
where T: Any,

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

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.

Trait Implementations§

impl<T> ArrayLike for Box<[T; 0]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 1]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 128]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 16]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 192]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 2]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 3]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 32]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 4]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 64]>

type Item = T

Type of the elements being stored.

impl<T> ArrayLike for Box<[T; 8]>

type Item = T

Type of the elements being stored.

1.64.0 · source§

impl<T: AsFd + ?Sized> AsFd for Box<T>

fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor. Read more

1.71.0 · source§

impl<T: AsHandle + ?Sized> AsHandle for Box<T>

Available on Windows only.

fn as_handle(&self) -> BorrowedHandle<'_>

Borrows the handle. Read more

1.5.0 · source§

impl<T, A> AsMut<T> for Box<T, A>
where A: Allocator, T: ?Sized,

fn as_mut(&mut self) -> &mut T

Converts this type into a mutable reference of the (usually inferred) input type.

1.63.0 · source§

impl<T: AsRawFd> AsRawFd for Box<T>

fn as_raw_fd(&self) -> RawFd

Extracts the raw file descriptor. Read more

1.5.0 · source§

impl<T, A> AsRef<T> for Box<T, A>
where A: Allocator, T: ?Sized,

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

1.71.0 · source§

impl<T: AsSocket> AsSocket for Box<T>

Available on Windows only.

fn as_socket(&self) -> BorrowedSocket<'_>

Borrows the socket.

impl<Args, F, A> AsyncFn<Args> for Box<F, A>
where Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator,

type CallFuture<'a> = <F as AsyncFn<Args>>::CallFuture<'a> where Box<F, A>: 'a

🔬This is a nightly-only experimental API. (async_fn_traits)

Future returned by AsyncFn::async_call.

extern "rust-call" fn async_call( &self, args: Args ) -> <Box<F, A> as AsyncFn<Args>>::CallFuture<'_>

🔬This is a nightly-only experimental API. (async_fn_traits)

Call the AsyncFn, returning a future which may borrow from the called closure.

impl<Args, F, A> AsyncFnMut<Args> for Box<F, A>
where Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator,

type CallMutFuture<'a> = <F as AsyncFnMut<Args>>::CallMutFuture<'a> where Box<F, A>: 'a

🔬This is a nightly-only experimental API. (async_fn_traits)

Future returned by AsyncFnMut::async_call_mut.

extern "rust-call" fn async_call_mut( &mut self, args: Args ) -> <Box<F, A> as AsyncFnMut<Args>>::CallMutFuture<'_>

🔬This is a nightly-only experimental API. (async_fn_traits)

Call the AsyncFnMut, returning a future which may borrow from the called closure.

impl<Args, F, A> AsyncFnOnce<Args> for Box<F, A>
where Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator,

type Output = <F as AsyncFnOnce<Args>>::Output

🔬This is a nightly-only experimental API. (async_fn_traits)

Output type of the called closure’s future.

type CallOnceFuture = <F as AsyncFnOnce<Args>>::CallOnceFuture

🔬This is a nightly-only experimental API. (async_fn_traits)

Future returned by AsyncFnOnce::async_call_once.

extern "rust-call" fn async_call_once( self, args: Args ) -> <Box<F, A> as AsyncFnOnce<Args>>::CallOnceFuture

🔬This is a nightly-only experimental API. (async_fn_traits)

Call the AsyncFnOnce, returning a future which may move out of the called closure.

impl<S> AsyncIterator for Box<S>
where S: AsyncIterator + Unpin + ?Sized,

type Item = <S as AsyncIterator>::Item

🔬This is a nightly-only experimental API. (async_iterator #79024)

The type of items yielded by the async iterator.

fn poll_next( self: Pin<&mut Box<S>>, cx: &mut Context<'_> ) -> Poll<Option<<Box<S> as AsyncIterator>::Item>>

🔬This is a nightly-only experimental API. (async_iterator #79024)

Attempt to pull out the next value of this async iterator, registering the current task for wakeup if the value is not yet available, and returning None if the async iterator is exhausted. Read more

fn size_hint(&self) -> (usize, Option<usize>)

🔬This is a nightly-only experimental API. (async_iterator #79024)

Returns the bounds on the remaining length of the async iterator. Read more

1.1.0 · source§

impl<T, A> Borrow<T> for Box<T, A>
where A: Allocator, T: ?Sized,

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

1.1.0 · source§

impl<T, A> BorrowMut<T> for Box<T, A>
where A: Allocator, T: ?Sized,

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

impl<B: BufRead + ?Sized> BufRead for Box

fn fill_buf(&mut self) -> Result<&[u8]>

Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more

fn consume(&mut self, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read. Read more

fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>

Read all bytes into buf until the delimiter byte or EOF is reached. Read more

fn read_line(&mut self, buf: &mut String) -> Result<usize>

Read all bytes until a newline (the 0xA byte) is reached, and append them to the provided String buffer. Read more

fn has_data_left(&mut self) -> Result<bool>

🔬This is a nightly-only experimental API. (buf_read_has_data_left #86423)

Check if the underlying Read has any data left to be read. Read more

fn skip_until(&mut self, byte: u8) -> Result<usize>

🔬This is a nightly-only experimental API. (bufread_skip_until #111735)

Skip all bytes until the delimiter byte or EOF is reached. Read more

fn split(self, byte: u8) -> Split<Self> ⓘ
where Self: Sized,

Returns an iterator over the contents of this reader split on the byte byte. Read more

fn lines(self) -> Lines<Self> ⓘ
where Self: Sized,

Returns an iterator over the lines of this reader. Read more

1.3.0 · source§

impl<T, A> Clone for Box<[T], A>
where T: Clone, A: Allocator + Clone,

fn clone(&self) -> Box<[T], A>

Returns a copy of the value. Read more

fn clone_from(&mut self, other: &Box<[T], A>)

Performs copy-assignment from source. Read more

1.29.0 · source§

impl Clone for Box<CStr>

fn clone(&self) -> Box<CStr>

Returns a copy of the value. Read more

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more

1.29.0 · source§

impl Clone for Box<OsStr>

fn clone(&self) -> Self

Returns a copy of the value. Read more

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more

1.29.0 · source§

impl Clone for Box<Path>

fn clone(&self) -> Self

Returns a copy of the value. Read more

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more

impl<T, A> Clone for Box<T, A>
where T: Clone, A: Allocator + Clone,

fn clone(&self) -> 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);

fn clone_from(&mut self, source: &Box<T, A>)

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);

1.3.0 · source§

impl Clone for Box<str>

fn clone(&self) -> Box<str>

Returns a copy of the value. Read more

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more

impl<G, R, A> Coroutine<R> for Box<G, A>
where G: Coroutine<R> + Unpin + ?Sized, A: Allocator,

type Yield = <G as Coroutine<R>>::Yield

🔬This is a nightly-only experimental API. (coroutine_trait #43122)

The type of value this coroutine yields. Read more

type Return = <G as Coroutine<R>>::Return

🔬This is a nightly-only experimental API. (coroutine_trait #43122)

The type of value this coroutine returns. Read more

fn resume( self: Pin<&mut Box<G, A>>, arg: R ) -> CoroutineState<<Box<G, A> as Coroutine<R>>::Yield, <Box<G, A> as Coroutine<R>>::Return>

🔬This is a nightly-only experimental API. (coroutine_trait #43122)

Resumes the execution of this coroutine. Read more

impl<G, R, A> Coroutine<R> for Pin<Box<G, A>>
where G: Coroutine<R> + ?Sized, A: Allocator + 'static,

type Yield = <G as Coroutine<R>>::Yield

🔬This is a nightly-only experimental API. (coroutine_trait #43122)

The type of value this coroutine yields. Read more

type Return = <G as Coroutine<R>>::Return

🔬This is a nightly-only experimental API. (coroutine_trait #43122)

The type of value this coroutine returns. Read more

fn resume( self: Pin<&mut Pin<Box<G, A>>>, arg: R ) -> CoroutineState<<Pin<Box<G, A>> as Coroutine<R>>::Yield, <Pin<Box<G, A>> as Coroutine<R>>::Return>

🔬This is a nightly-only experimental API. (coroutine_trait #43122)

Resumes the execution of this coroutine. Read more

impl<T, A> Debug for Box<T, A>
where T: Debug + ?Sized, A: Allocator,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more

impl<T> Default for Box<[T]>

fn default() -> Box<[T]>

Returns the “default value” for a type. Read more

1.17.0 · source§

impl Default for Box<CStr>

fn default() -> Box<CStr>

Returns the “default value” for a type. Read more

1.17.0 · source§

impl Default for Box<OsStr>

fn default() -> Box<OsStr>

Returns the “default value” for a type. Read more

impl<T> Default for Box<T>
where T: Default,

fn default() -> Box<T>

Creates a Box<T>, with the Default value for T.

1.17.0 · source§

impl Default for Box<str>

fn default() -> Box<str>

Returns the “default value” for a type. Read more

impl<T, A> Deref for Box<T, A>
where A: Allocator, T: ?Sized,

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T, A> DerefMut for Box<T, A>
where A: Allocator, T: ?Sized,

fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<T, A> Display for Box<T, A>
where T: Display + ?Sized, A: Allocator,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more

impl<I, A> DoubleEndedIterator for Box<I, A>
where I: DoubleEndedIterator + ?Sized, A: Allocator,

fn next_back(&mut self) -> Option<::Item>

Removes and returns an element from the end of the iterator. Read more

fn nth_back(&mut self, n: usize) -> Option<::Item>

Returns the nth element from the end of the iterator. Read more

fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>>

🔬This is a nightly-only experimental API. (iter_advance_by #77404)

Advances the iterator from the back by n elements. Read more

1.27.0 · source§

fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
where Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Output = B>,

This is the reverse version of Iterator::try_fold(): it takes elements starting from the back of the iterator. Read more

1.27.0 · source§

fn rfold<B, F>(self, init: B, f: F) -> B
where Self: Sized, F: FnMut(B, Self::Item) -> B,

An iterator method that reduces the iterator’s elements to a single, final value, starting from the back. Read more

1.27.0 · source§

fn rfind(&mut self, predicate: P) -> Option<Self::Item>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Searches for an element of an iterator from the back that satisfies a predicate. Read more

impl<T, A> Drop for Box<T, A>
where A: Allocator, T: ?Sized,

fn drop(&mut self)

Executes the destructor for this type. Read more

1.8.0 · source§

impl<T> Error for Box<T>
where T: Error,

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

The lower-level source of this error, if any. Read more

fn provide<'b>(&'b self, request: &mut Request<'b>)

🔬This is a nightly-only experimental API. (error_generic_member_access #99301)

Provides type based access to context intended for error reports. Read more

impl<I, A> ExactSizeIterator for Box<I, A>
where I: ExactSizeIterator + ?Sized, A: Allocator,

fn len(&self) -> usize

Returns the exact remaining length of the iterator. Read more

fn is_empty(&self) -> bool

🔬This is a nightly-only experimental API. (exact_size_is_empty #35428)

Returns true if the iterator is empty. Read more

1.45.0 · source§

impl Extend<Box<str>> for String

fn extend(&mut self, iter: I)
where I: IntoIterator<Item = Box<str>>,

Extends a collection with the contents of an iterator. Read more

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one #72631)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one #72631)

Reserves capacity in a collection for the given number of additional elements. Read more

1.35.0 · source§

impl<Args, F, A> Fn<Args> for Box<F, A>
where Args: Tuple, F: Fn<Args> + ?Sized, A: Allocator,

extern "rust-call" fn call( &self, args: Args ) -> <Box<F, A> as FnOnce<Args>>::Output

🔬This is a nightly-only experimental API. (fn_traits #29625)

Performs the call operation.

1.35.0 · source§

impl<Args, F, A> FnMut<Args> for Box<F, A>
where Args: Tuple, F: FnMut<Args> + ?Sized, A: Allocator,

extern "rust-call" fn call_mut( &mut self, args: Args ) -> <Box<F, A> as FnOnce<Args>>::Output

🔬This is a nightly-only experimental API. (fn_traits #29625)

Performs the call operation.

1.35.0 · source§

impl<Args, F, A> FnOnce<Args> for Box<F, A>
where Args: Tuple, F: FnOnce<Args> + ?Sized, A: Allocator,

type Output = <F as FnOnce<Args>>::Output

The returned type after the call operator is used.

extern "rust-call" fn call_once( self, args: Args ) -> <Box<F, A> as FnOnce<Args>>::Output

🔬This is a nightly-only experimental API. (fn_traits #29625)

Performs the call operation.

1.17.0 · source§

impl<T> From<&[T]> for Box<[T]>
where T: Clone,

fn from(slice: &[T]) -> 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

// 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:?}");

1.17.0 · source§

impl From<&CStr> for Box<CStr>

fn from(s: &CStr) -> Box<CStr>

Converts a &CStr into a Box<CStr>, by copying the contents into a newly allocated Box.

1.17.0 · source§

impl From<&OsStr> for Box<OsStr>

fn from(s: &OsStr) -> Box<OsStr>

Copies the string into a newly allocated Box<OsStr>.

1.17.0 · source§

impl From<&Path> for Box<Path>

fn from(path: &Path) -> Box<Path>

Creates a boxed Path from a reference.

This will allocate and clone path to it.

1.6.0 · source§

impl<'a> From<&str> for Box<dyn Error + 'a>

fn from(err: &str) -> Box<dyn Error + 'a>

Converts a str into a box of dyn Error.

§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))

impl<'a> From<&str> for Box<dyn Error + Sync + Send + 'a>

fn from(err: &str) -> Box<dyn Error + Sync + Send + 'a>

Converts a str into a box of dyn Error + Send + Sync.

§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))

1.17.0 · source§

impl From<&str> for Box<str>

fn from(s: &str) -> Box<str>

Converts a &str into a Box<str>

This conversion allocates on the heap and performs a copy of s.

§Examples

let boxed: Box<str> = Box::from("hello");
println!("{boxed}");

1.45.0 · source§

impl<T, const N: usize> From<[T; N]> for Box<[T]>

fn from(array: [T; N]) -> Box<[T]>

Converts a [T; N] into a Box<[T]>

This conversion moves the array to newly heap-allocated memory.

§Examples

let boxed: Box<[u8]> = Box::from([4, 2]);
println!("{boxed:?}");

1.18.0 · source§

impl<T, A> From<Box<[T], A>> for Vec<T, A>
where A: Allocator,

fn from(s: Box<[T], A>) -> Vec<T, A>

Convert a boxed slice into a vector by transferring ownership of the existing heap allocation.

§Examples

let b: Box<[i32]> = vec![1, 2, 3].into_boxed_slice();
assert_eq!(Vec::from(b), vec![1, 2, 3]);

1.18.0 · source§

impl From<Box<CStr>> for CString

fn from(s: Box<CStr>) -> CString

Converts a Box<CStr> into a CString without copying or allocating.

1.18.0 · source§

impl From<Box<OsStr>> for OsString

fn from(boxed: Box<OsStr>) -> OsString

Converts a Box<OsStr> into an OsString without copying or allocating.

1.18.0 · source§

impl From<Box<Path>> for PathBuf

fn from(boxed: Box<Path>) -> PathBuf

Converts a Box<Path> into a PathBuf.

This conversion does not allocate or copy memory.

1.21.0 · source§

impl<T, A> From<Box<T, A>> for Arc<T, A>
where A: Allocator, T: ?Sized,

fn from(v: Box<T, A>) -> Arc<T, A>

Move a boxed object to a new, reference-counted allocation.

§Example

let unique: Box<str> = Box::from("eggplant");
let shared: Arc<str> = Arc::from(unique);
assert_eq!("eggplant", &shared[..]);

1.33.0 · source§

impl<T, A> From<Box<T, A>> for Pin<Box<T, A>>
where A: Allocator + 'static, T: ?Sized,

fn from(boxed: Box<T, A>) -> Pin<Box<T, A>>

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 <Pin<Box<T>>>::from(Box::new(x)) can also be written more concisely using Box::pin(x). 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.

1.21.0 · source§

impl<T, A> From<Box<T, A>> for Rc<T, A>
where A: Allocator, T: ?Sized,

fn from(v: Box<T, A>) -> Rc<T, A>

Move a boxed object to a new, reference counted, allocation.

§Example

let original: Box<i32> = Box::new(1);
let shared: Rc<i32> = Rc::from(original);
assert_eq!(1, *shared);

1.18.0 · source§

impl From<Box<str>> for String

fn from(s: Box<str>) -> String

Converts the given boxed str slice to a String. It is notable that the str slice is owned.

§Examples

let s1: String = String::from("hello world");
let s2: Box<str> = s1.into_boxed_str();
let s3: String = String::from(s2);

assert_eq!("hello world", s3)

1.19.0 · source§

impl<A> From<Box<str, A>> for Box<[u8], A>
where A: Allocator,

fn from(s: Box<str, A>) -> Box<[u8], A>

Converts a Box<str> into a Box<[u8]>

This conversion does not allocate on the heap and happens in place.

§Examples

// 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);

1.20.0 · source§

impl From<CString> for Box<CStr>

fn from(s: CString) -> Box<CStr>

Converts a CString into a Box<CStr> without copying or allocating.

1.45.0 · source§

impl<T> From<Cow<'_, [T]>> for Box<[T]>
where T: Clone,

fn from(cow: Cow<'_, [T]>) -> 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.

1.45.0 · source§

impl From<Cow<'_, CStr>> for Box<CStr>

fn from(cow: Cow<'_, CStr>) -> Box<CStr>

Converts a Cow<'a, CStr> into a Box<CStr>, by copying the contents if they are borrowed.

1.45.0 · source§

impl From<Cow<'_, OsStr>> for Box<OsStr>

fn from(cow: Cow<'_, OsStr>) -> Box<OsStr>

Converts a Cow<'a, OsStr> into a Box<OsStr>, by copying the contents if they are borrowed.

1.45.0 · source§

impl From<Cow<'_, Path>> for Box<Path>

fn from(cow: Cow<'_, Path>) -> Box<Path>

Creates a boxed Path from a clone-on-write pointer.

Converting from a Cow::Owned does not clone or allocate.

1.45.0 · source§

impl From<Cow<'_, str>> for Box<str>

fn from(cow: Cow<'_, str>) -> 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

use std::borrow::Cow;

let unboxed = Cow::Borrowed("hello");
let boxed: Box<str> = Box::from(unboxed);
println!("{boxed}");

let unboxed = Cow::Owned("hello".to_string());
let boxed: Box<str> = Box::from(unboxed);
println!("{boxed}");

1.22.0 · source§

impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + 'a>

fn from(err: Cow<'b, str>) -> Box<dyn Error + 'a>

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))

1.22.0 · source§

impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Sync + Send + 'a>

fn from(err: Cow<'b, str>) -> Box<dyn Error + Sync + Send + '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))

impl<'a, E> From<E> for Box<dyn Error + 'a>
where E: Error + 'a,

fn from(err: E) -> 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))

impl<'a, E> From<E> for Box<dyn Error + Sync + Send + 'a>
where E: Error + Send + Sync + 'a,

fn from(err: E) -> Box<dyn Error + Sync + Send + '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))

1.20.0 · source§

impl From<OsString> for Box<OsStr>

fn from(s: OsString) -> Box<OsStr>

Converts an OsString into a Box<OsStr> without copying or allocating.

1.20.0 · source§

impl From<PathBuf> for Box<Path>

fn from(p: PathBuf) -> Box<Path>

Converts a PathBuf into a Box<Path>.

This conversion currently should not allocate memory, but this behavior is not guaranteed on all platforms or in all future versions.

1.6.0 · source§

impl<'a> From<String> for Box<dyn Error + 'a>

fn from(str_err: String) -> Box<dyn Error + 'a>

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))

impl<'a> From<String> for Box<dyn Error + Sync + Send + 'a>

fn from(err: String) -> Box<dyn Error + Sync + Send + 'a>

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))

1.20.0 · source§

impl From<String> for Box<str>

fn from(s: String) -> Box<str>

Converts the given String to a boxed str slice that is owned.

§Examples

let s1: String = String::from("hello world");
let s2: Box<str> = Box::from(s1);
let s3: String = String::from(s2);

assert_eq!("hello world", s3)

1.6.0 · source§

impl<T> From<T> for Box<T>

fn from(t: T) -> Box<T>

Converts a T into a Box<T>

The conversion allocates on the heap and moves t from the stack into it.

§Examples

let x = 5;
let boxed = Box::new(5);

assert_eq!(Box::from(x), boxed);

1.20.0 · source§

impl<T, A> From<Vec<T, A>> for Box<[T], A>
where A: Allocator,

fn from(v: Vec<T, A>) -> Box<[T], A>

Convert a vector into a boxed slice.

Before doing the conversion, this method discards excess capacity like Vec::shrink_to_fit.

§Examples

assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice());

Any excess capacity is removed:

let mut vec = Vec::with_capacity(10);
vec.extend([1, 2, 3]);

assert_eq!(Box::from(vec), vec![1, 2, 3].into_boxed_slice());

1.45.0 · source§

impl FromIterator<Box<str>> for String

fn from_iter(iter: I) -> String
where I: IntoIterator<Item = Box<str>>,

Creates a value from an iterator. Read more

1.32.0 · source§

impl FromIterator for Box<[I]>

fn from_iter<T>(iter: T) -> Box<[I]>
where T: IntoIterator<Item = I>,

Creates a value from an iterator. Read more

1.36.0 · source§

impl<F, A> Future for Box<F, A>
where F: Future + Unpin + ?Sized, A: Allocator,

type Output = <F as Future>::Output

The type of value produced on completion.

fn poll( self: Pin<&mut Box<F, A>>, cx: &mut Context<'_> ) -> Poll<<Box<F, A> as Future>::Output>

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more

impl<T, A> Hash for Box<T, A>
where T: Hash + ?Sized, A: Allocator,

fn hash<H>(&self, state: &mut H)
where H: Hasher,

Feeds this value into the given Hasher. Read more

1.3.0 · source§

fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more

1.22.0 · source§

impl<T, A> Hasher for Box<T, A>
where T: Hasher + ?Sized, A: Allocator,

fn finish(&self) -> u64

Returns the hash value for the values written so far. Read more

fn write(&mut self, bytes: &[u8])

Writes some data into this Hasher. Read more

fn write_u8(&mut self, i: u8)

Writes a single u8 into this hasher.

fn write_u16(&mut self, i: u16)

Writes a single u16 into this hasher.

fn write_u32(&mut self, i: u32)

Writes a single u32 into this hasher.

fn write_u64(&mut self, i: u64)

Writes a single u64 into this hasher.

fn write_u128(&mut self, i: u128)

Writes a single u128 into this hasher.

fn write_usize(&mut self, i: usize)

Writes a single usize into this hasher.

fn write_i8(&mut self, i: i8)

Writes a single i8 into this hasher.

fn write_i16(&mut self, i: i16)

Writes a single i16 into this hasher.

fn write_i32(&mut self, i: i32)

Writes a single i32 into this hasher.

fn write_i64(&mut self, i: i64)

Writes a single i64 into this hasher.

fn write_i128(&mut self, i: i128)

Writes a single i128 into this hasher.

fn write_isize(&mut self, i: isize)

Writes a single isize into this hasher.

fn write_length_prefix(&mut self, len: usize)

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras #96762)

Writes a length prefix into this hasher, as part of being prefix-free. Read more

fn write_str(&mut self, s: &str)

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras #96762)

Writes a single str into this hasher. Read more

impl<I, A> Iterator for Box<I, A>
where I: Iterator + ?Sized, A: Allocator,

type Item = ::Item

The type of the elements being iterated over.

fn next(&mut self) -> Option<::Item>

Advances the iterator and returns the next value. Read more

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the iterator. Read more

fn nth(&mut self, n: usize) -> Option<::Item>

Returns the nth element of the iterator. Read more

fn last(self) -> Option<::Item>

Consumes the iterator, returning the last element. Read more

fn next_chunk<const N: usize>( &mut self ) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>
where Self: Sized,

🔬This is a nightly-only experimental API. (iter_next_chunk #98326)

Advances the iterator and returns an array containing the next N values. Read more

fn count(self) -> usize
where Self: Sized,

Consumes the iterator, counting the number of iterations and returning it. Read more

fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>

🔬This is a nightly-only experimental API. (iter_advance_by #77404)

Advances the iterator by n elements. Read more

1.28.0 · source§

fn step_by(self, step: usize) -> StepBy<Self> ⓘ
where Self: Sized,

Creates an iterator starting at the same point, but stepping by the given amount at each iteration. Read more

fn chain(self, other: U) -> Chain<Self, ::IntoIter> ⓘ
where Self: Sized, U: IntoIterator<Item = Self::Item>,

Takes two iterators and creates a new iterator over both in sequence. Read more

fn zip(self, other: U) -> Zip<Self, ::IntoIter> ⓘ
where Self: Sized, U: IntoIterator,

‘Zips up’ two iterators into a single iterator of pairs. Read more

fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> ⓘ
where Self: Sized, G: FnMut() -> Self::Item,

🔬This is a nightly-only experimental API. (iter_intersperse #79524)

Creates a new iterator which places an item generated by separator between adjacent items of the original iterator. Read more

fn map<B, F>(self, f: F) -> Map<Self, F> ⓘ
where Self: Sized, F: FnMut(Self::Item) -> B,

Takes a closure and creates an iterator which calls that closure on each element. Read more

1.21.0 · source§

fn for_each<F>(self, f: F)
where Self: Sized, F: FnMut(Self::Item),

Calls a closure on each element of an iterator. Read more

fn filter(self, predicate: P) -> Filter<Self, P> ⓘ
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator which uses a closure to determine if an element should be yielded. Read more

fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> ⓘ
where Self: Sized, F: FnMut(Self::Item) -> Option,

Creates an iterator that both filters and maps. Read more

fn enumerate(self) -> Enumerate<Self> ⓘ
where Self: Sized,

Creates an iterator which gives the current iteration count as well as the next value. Read more

fn peekable(self) -> Peekable<Self> ⓘ
where Self: Sized,

Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. See their documentation for more information. Read more

fn skip_while(self, predicate: P) -> SkipWhile<Self, P> ⓘ
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that skips elements based on a predicate. Read more

fn take_while(self, predicate: P) -> TakeWhile<Self, P> ⓘ
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that yields elements based on a predicate. Read more

1.57.0 · source§

fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> ⓘ
where Self: Sized, P: FnMut(Self::Item) -> Option,

Creates an iterator that both yields elements based on a predicate and maps. Read more

fn skip(self, n: usize) -> Skip<Self> ⓘ
where Self: Sized,

Creates an iterator that skips the first n elements. Read more

fn take(self, n: usize) -> Take<Self> ⓘ
where Self: Sized,

Creates an iterator that yields the first n elements, or fewer if the underlying iterator ends sooner. Read more

fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> ⓘ
where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option,

An iterator adapter which, like fold, holds internal state, but unlike fold, produces a new iterator. Read more

fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> ⓘ
where Self: Sized, U: IntoIterator, F: FnMut(Self::Item) -> U,

Creates an iterator that works like map, but flattens nested structure. Read more

fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N> ⓘ
where Self: Sized, F: FnMut(&[Self::Item; N]) -> R,

🔬This is a nightly-only experimental API. (iter_map_windows #87155)

Calls the given function f for each contiguous window of size N over self and returns an iterator over the outputs of f. Like slice::windows(), the windows during mapping overlap as well. Read more

fn fuse(self) -> Fuse<Self> ⓘ
where Self: Sized,

Creates an iterator which ends after the first None. Read more

fn inspect<F>(self, f: F) -> Inspect<Self, F> ⓘ
where Self: Sized, F: FnMut(&Self::Item),

Does something with each element of an iterator, passing the value on. Read more

fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Borrows an iterator, rather than consuming it. Read more

fn collect(self) -> B
where B: FromIterator<Self::Item>, Self: Sized,

Transforms an iterator into a collection. Read more

fn collect_into<E>(self, collection: &mut E) -> &mut E
where E: Extend<Self::Item>, Self: Sized,

🔬This is a nightly-only experimental API. (iter_collect_into #94780)

Collects all the items from an iterator into a collection. Read more

fn partition<B, F>(self, f: F) -> (B, B)
where Self: Sized, B: Default + Extend<Self::Item>, F: FnMut(&Self::Item) -> bool,

Consumes an iterator, creating two collections from it. Read more

fn is_partitioned(self, predicate: P) -> bool
where Self: Sized, P: FnMut(Self::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_is_partitioned #62544)

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return true precede all those that return false. Read more

1.27.0 · source§

fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
where Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Output = B>,

An iterator method that applies a function as long as it returns successfully, producing a single, final value. Read more

1.27.0 · source§

fn try_for_each<F, R>(&mut self, f: F) -> R
where Self: Sized, F: FnMut(Self::Item) -> R, R: Try<Output = ()>,

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error. Read more

fn fold<B, F>(self, init: B, f: F) -> B
where Self: Sized, F: FnMut(B, Self::Item) -> B,

Folds every element into an accumulator by applying an operation, returning the final result. Read more

1.51.0 · source§

fn reduce<F>(self, f: F) -> Option<Self::Item>
where Self: Sized, F: FnMut(Self::Item, Self::Item) -> Self::Item,

Reduces the elements to a single one, by repeatedly applying a reducing operation. Read more

fn try_reduce<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType
where Self: Sized, F: FnMut(Self::Item, Self::Item) -> R, R: Try<Output = Self::Item>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (iterator_try_reduce #87053)

Reduces the elements to a single one by repeatedly applying a reducing operation. If the closure returns a failure, the failure is propagated back to the caller immediately. Read more

fn all<F>(&mut self, f: F) -> bool
where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if every element of the iterator matches a predicate. Read more

fn any<F>(&mut self, f: F) -> bool
where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if any element of the iterator matches a predicate. Read more

fn find(&mut self, predicate: P) -> Option<Self::Item>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Searches for an element of an iterator that satisfies a predicate. Read more

1.30.0 · source§

fn find_map<B, F>(&mut self, f: F) -> Option
where Self: Sized, F: FnMut(Self::Item) -> Option,

Applies function to the elements of iterator and returns the first non-none result. Read more

fn try_find<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType
where Self: Sized, F: FnMut(&Self::Item) -> R, R: Try<Output = bool>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (try_find #63178)

Applies function to the elements of iterator and returns the first true result or the first error. Read more

fn position(&mut self, predicate: P) -> Option<usize>
where Self: Sized, P: FnMut(Self::Item) -> bool,

Searches for an element in an iterator, returning its index. Read more

1.6.0 · source§

fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>
where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the maximum value from the specified function. Read more

1.15.0 · source§

fn max_by<F>(self, compare: F) -> Option<Self::Item>
where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the maximum value with respect to the specified comparison function. Read more

1.6.0 · source§

fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>
where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the minimum value from the specified function. Read more

1.15.0 · source§

fn min_by<F>(self, compare: F) -> Option<Self::Item>
where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the minimum value with respect to the specified comparison function. Read more

fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
where FromA: Default + Extend<A>, FromB: Default + Extend, Self: Sized + Iterator<Item = (A, B)>,

Converts an iterator of pairs into a pair of containers. Read more

1.36.0 · source§

fn copied<'a, T>(self) -> Copied<Self> ⓘ
where T: 'a + Copy, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which copies all of its elements. Read more

fn cloned<'a, T>(self) -> Cloned<Self> ⓘ
where T: 'a + Clone, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which clones all of its elements. Read more

fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N> ⓘ
where Self: Sized,

🔬This is a nightly-only experimental API. (iter_array_chunks #100450)

Returns an iterator over N elements of the iterator at a time. Read more

1.11.0 · source§

fn sum<S>(self) -> S
where Self: Sized, S: Sum<Self::Item>,

Sums the elements of an iterator. Read more

1.11.0 · source§

fn product(self) -> P
where Self: Sized, P: Product<Self::Item>,

Iterates over the entire iterator, multiplying all the elements Read more

fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, ::Item) -> Ordering,

🔬This is a nightly-only experimental API. (iter_order_by #64295)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function. Read more

1.5.0 · source§

fn partial_cmp(self, other: I) -> Option<Ordering>
where I: IntoIterator, Self::Item: PartialOrd<::Item>, Self: Sized,

Lexicographically compares the PartialOrd elements of this Iterator with those of another. The comparison works like short-circuit evaluation, returning a result without comparing the remaining elements. As soon as an order can be determined, the evaluation stops and a result is returned. Read more

fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>
where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, ::Item) -> Option<Ordering>,

🔬This is a nightly-only experimental API. (iter_order_by #64295)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function. Read more

1.5.0 · source§

fn eq(self, other: I) -> bool
where I: IntoIterator, Self::Item: PartialEq<::Item>, Self: Sized,

Determines if the elements of this Iterator are equal to those of another. Read more

fn eq_by<I, F>(self, other: I, eq: F) -> bool
where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, ::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_order_by #64295)

Determines if the elements of this Iterator are equal to those of another with respect to the specified equality function. Read more

1.5.0 · source§

fn ne(self, other: I) -> bool
where I: IntoIterator, Self::Item: PartialEq<::Item>, Self: Sized,

Determines if the elements of this Iterator are not equal to those of another. Read more

1.5.0 · source§

fn lt(self, other: I) -> bool
where I: IntoIterator, Self::Item: PartialOrd<::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less than those of another. Read more

1.5.0 · source§

fn le(self, other: I) -> bool
where I: IntoIterator, Self::Item: PartialOrd<::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less or equal to those of another. Read more

1.5.0 · source§

fn gt(self, other: I) -> bool
where I: IntoIterator, Self::Item: PartialOrd<::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than those of another. Read more

1.5.0 · source§

fn ge(self, other: I) -> bool
where I: IntoIterator, Self::Item: PartialOrd<::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another. Read more

fn is_sorted_by<F>(self, compare: F) -> bool
where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> bool,

🔬This is a nightly-only experimental API. (is_sorted #53485)

Checks if the elements of this iterator are sorted using the given comparator function. Read more

fn is_sorted_by_key<F, K>(self, f: F) -> bool
where Self: Sized, F: FnMut(Self::Item) -> K, K: PartialOrd,

🔬This is a nightly-only experimental API. (is_sorted #53485)

Checks if the elements of this iterator are sorted using the given key extraction function. Read more

impl<T, A> Ord for Box<T, A>
where T: Ord + ?Sized, A: Allocator,

fn cmp(&self, other: &Box<T, A>) -> Ordering

This method returns an Ordering between self and other. Read more

1.21.0 · source§

fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more

1.21.0 · source§

fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more

1.50.0 · source§

fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more

impl<T, A> PartialEq for Box<T, A>
where T: PartialEq + ?Sized, A: Allocator,

fn eq(&self, other: &Box<T, A>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Box<T, A>) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, A> PartialOrd for Box<T, A>
where T: PartialOrd + ?Sized, A: Allocator,

fn partial_cmp(&self, other: &Box<T, A>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more

fn lt(&self, other: &Box<T, A>) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more

fn le(&self, other: &Box<T, A>) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

fn ge(&self, other: &Box<T, A>) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

fn gt(&self, other: &Box<T, A>) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more

impl<T, A> Pointer for Box<T, A>
where A: Allocator, T: ?Sized,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<R: Read + ?Sized> Read for Box<R>

fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

fn read_buf(&mut self, cursor: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (read_buf #78485)

Pull some bytes from this source into the specified buffer. Read more

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>

Like read, except that it reads into a slice of buffers. Read more

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector #69941)

Determines if this Reader has an efficient read_vectored implementation. Read more

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>

Read all bytes until EOF in this source, placing them into buf. Read more

fn read_to_string(&mut self, buf: &mut String) -> Result<usize>

Read all bytes until EOF in this source, appending them to buf. Read more

fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>

Read the exact number of bytes required to fill buf. Read more

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (read_buf #78485)

Read the exact number of bytes required to fill cursor. Read more

fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Creates a “by reference” adaptor for this instance of Read. Read more

fn bytes(self) -> Bytes<Self> ⓘ
where Self: Sized,

Transforms this Read instance to an Iterator over its bytes. Read more

fn chain<R: Read>(self, next: R) -> Chain<Self, R> ⓘ
where Self: Sized,

Creates an adapter which will chain this stream with another. Read more

fn take(self, limit: u64) -> Take<Self> ⓘ
where Self: Sized,

Creates an adapter which will read at most limit bytes from it. Read more

impl<S: Seek + ?Sized> Seek for Box<S>

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream. Read more

fn stream_position(&mut self) -> Result<u64>

Returns the current seek position from the start of the stream. Read more

1.55.0 · source§

fn rewind(&mut self) -> Result<()>

Rewind to the beginning of a stream. Read more

fn stream_len(&mut self) -> Result<u64>

🔬This is a nightly-only experimental API. (seek_stream_len #59359)

Returns the length of this stream (in bytes). Read more

fn seek_relative(&mut self, offset: i64) -> Result<()>

🔬This is a nightly-only experimental API. (seek_seek_relative #117374)

Seeks relative to the current position. Read more

1.43.0 · source§

impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]>

fn try_from( boxed_slice: Box<[T]> ) -> Result<Box<[T; N]>, <Box<[T; N]> as TryFrom<Box<[T]>>>::Error>

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.

type Error = Box<[T]>

The type returned in the event of a conversion error.

1.66.0 · source§

impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]>

fn try_from( vec: Vec<T> ) -> Result<Box<[T; N]>, <Box<[T; N]> as TryFrom<Vec<T>>>::Error>

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);

type Error = Vec<T>

The type returned in the event of a conversion error.

impl<W: Write + ?Sized> Write for Box<W>

fn write(&mut self, buf: &[u8]) -> Result<usize>

Write a buffer into this writer, returning how many bytes were written. Read more

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize>

Like write, except that it writes from a slice of buffers. Read more

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector #69941)

Determines if this Writer has an efficient write_vectored implementation. Read more

fn flush(&mut self) -> Result<()>

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

fn write_all(&mut self, buf: &[u8]) -> Result<()>

Attempts to write an entire buffer into this writer. Read more

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<()>

Writes a formatted string into this writer, returning any error encountered. Read more

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<()>

🔬This is a nightly-only experimental API. (write_all_vectored #70436)

Attempts to write multiple buffers into this writer. Read more

fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Creates a “by reference” adapter for this instance of Write. Read more

impl<T, U, A> CoerceUnsized<Box<U, A>> for Box<T, A>
where T: Unsize + ?Sized, A: Allocator, U: ?Sized,

impl<T, U> DispatchFromDyn<Box> for Box<T>
where T: Unsize + ?Sized, U: ?Sized,

impl<T, A> Eq for Box<T, A>
where T: Eq + ?Sized, A: Allocator,

1.26.0 · source§

impl<I, A> FusedIterator for Box<I, A>
where I: FusedIterator + ?Sized, A: Allocator,

1.33.0 · source§

impl<T, A> Unpin for Box<T, A>
where A: Allocator, T: ?Sized,

Auto Trait Implementations§

impl<T: ?Sized, A> Freeze for Box<T, A>
where A: Freeze,

impl<T: ?Sized, A> RefUnwindSafe for Box<T, A>
where A: RefUnwindSafe, T: RefUnwindSafe,

impl<T: ?Sized, A> Send for Box<T, A>
where A: Send, T: Send,

impl<T: ?Sized, A> Sync for Box<T, A>
where A: Sync, T: Sync,

impl<T: ?Sized, A> UnwindSafe for Box<T, A>
where A: UnwindSafe, T: UnwindSafe,

Blanket Implementations§

impl<T> Any for T
where T: 'static + ?Sized,

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more

impl<T> Borrow<T> for T
where T: ?Sized,

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

impl<T> BorrowMut<T> for T
where T: ?Sized,

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

impl<T> From<!> for T

fn from(t: !) -> T

Converts to this type from the input type.

impl<T> From<T> for T

fn from(t: T) -> T

Returns the argument unchanged.

impl<T, U> Into for T
where U: From<T>,

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

impl IntoAsyncIterator for I
where I: AsyncIterator,

type Item = ::Item

🔬This is a nightly-only experimental API. (async_iterator #79024)

The type of the item yielded by the iterator

type IntoAsyncIter = I

🔬This is a nightly-only experimental API. (async_iterator #79024)

The type of the resulting iterator

fn into_async_iter(self) -> ::IntoAsyncIter

🔬This is a nightly-only experimental API. (async_iterator #79024)

Converts self into an async iterator

impl<F> IntoFuture for F
where F: Future,

type Output = <F as Future>::Output

The output that the future will produce on completion.

type IntoFuture = F

Which kind of future are we turning this into?

fn into_future(self) -> <F as IntoFuture>::IntoFuture

Creates a future from a value. Read more

impl IntoIterator for I
where I: Iterator,

type Item = ::Item

The type of the elements being iterated over.

type IntoIter = I

Which kind of iterator are we turning this into?

const: unstable · source§

fn into_iter(self) -> I

Creates an iterator from a value. Read more

impl<'a, F> Pattern<'a> for F
where F: FnMut(char) -> bool,

type Searcher = CharPredicateSearcher<'a, F>

🔬This is a nightly-only experimental API. (pattern #27721)

Associated searcher for this pattern

fn into_searcher(self, haystack: &'a str) -> CharPredicateSearcher<'a, F>

🔬This is a nightly-only experimental API. (pattern #27721)

Constructs the associated searcher from self and the haystack to search in.

fn is_contained_in(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches anywhere in the haystack

fn is_prefix_of(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the front of the haystack

fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str>

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the front of haystack, if it matches.

fn is_suffix_of(self, haystack: &'a str) -> bool
where CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the back of the haystack

fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str>
where CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the back of haystack, if it matches.

impl<T> ToOwned for T
where T: Clone,

type Owned = T

The resulting type after obtaining ownership.

fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more

fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more

impl<T> ToString for T
where T: Display + ?Sized,

default fn to_string(&self) -> String

Converts the given value to a String. Read more

impl<T, U> TryFrom for T
where U: Into<T>,

type Error = Infallible

The type returned in the event of a conversion error.

fn try_from(value: U) -> Result<T, <T as TryFrom>::Error>

Performs the conversion.

impl<T, U> TryInto for T
where U: TryFrom<T>,

type Error = >::Error

The type returned in the event of a conversion error.