Struct Box

1.36.0 · Source

pub struct Box<T, A = Global>(/* private fields */)
where
    A: Allocator,
    T: ?Sized;

Expand description

A pointer type that uniquely owns a heap allocation of type T.

See the module-level documentation for more.

Implementations§

Source §

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

1.0.0 · Source

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

Attempts 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));

Source

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

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

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.

Source §

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

1.0.0 · Source

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

Attempts 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));

Source

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

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

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.

Source §

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,

Attempts 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));

Source

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

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

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.

Source §

impl<T> Box<T>

1.0.0 · Source

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. See the memory layout section for more details.

§Examples

let five = Box::new(5);

1.82.0 (const: unstable) · Source

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

Constructs a new box with uninitialized contents.

§Examples

let mut five = Box::<u32>::new_uninit();
// Deferred initialization:
five.write(5);
let five = unsafe { five.assume_init() };

assert_eq!(*five, 5)

1.92.0 · Source

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

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

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.

Source

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

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

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. See the memory layout section for more details.

§Examples

#![feature(allocator_ext)]

let five = Box::try_new(5)?;

Source

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

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

Constructs a new box with uninitialized contents on the heap, returning an error if the allocation fails

§Examples

#![feature(allocator_ext)]

let mut five = Box::<u32>::try_new_uninit()?;
// Deferred initialization:
five.write(5);
let five = unsafe { five.assume_init() };

assert_eq!(*five, 5);

Source

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

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

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_ext)]

let zero = Box::<u32>::try_new_zeroed()?;
let zero = unsafe { zero.assume_init() };

assert_eq!(*zero, 0);

Source §

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

1.100.0 · Source

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

Allocates memory in the given allocator then places x into it.

This doesn’t actually allocate if T is zero-sized. See the memory layout section for more details.

§Examples

use std::alloc::System;

let five = Box::new_in(5, System);

Source

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

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

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. See the memory layout section for more details.

§Examples

#![feature(allocator_ext)]

use std::alloc::System;

let five = Box::try_new_in(5, System)?;

Source

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

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

Constructs a new box with uninitialized contents in the provided allocator.

§Examples

#![feature(allocator_ext)]

use std::alloc::System;

let mut five = Box::<u32, _>::new_uninit_in(System);
// Deferred initialization:
five.write(5);
let five = unsafe { five.assume_init() };

assert_eq!(*five, 5)

Source

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

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

Constructs a new box with uninitialized contents in the provided allocator, returning an error if the allocation fails

§Examples

#![feature(allocator_ext)]

use std::alloc::System;

let mut five = Box::<u32, _>::try_new_uninit_in(System)?;
// Deferred initialization:
five.write(5);
let five = unsafe { five.assume_init() };

assert_eq!(*five, 5);

Source

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

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

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_ext)]

use std::alloc::System;

let zero = Box::<u32, _>::new_zeroed_in(System);
let zero = unsafe { zero.assume_init() };

assert_eq!(*zero, 0)

Source

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

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

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_ext)]

use std::alloc::System;

let zero = Box::<u32, _>::try_new_zeroed_in(System)?;
let zero = unsafe { zero.assume_init() };

assert_eq!(*zero, 0);

Source

pub fn pin_in(x: T, alloc: A) -> Pin<Box<T, A>>
where A: StaticAllocator,

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

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.

§Examples

#![feature(allocator_ext)]
use std::alloc::System;

let x = Box::pin_in(1, System);

Source

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

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

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

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

Source

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

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

Consumes the Box, returning the wrapped value.

§Examples

#![feature(box_into_inner)]

let c = Box::new(5);

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

1.100.0 · Source

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

Consumes the Box without consuming its allocation, returning the wrapped value and a Box to the uninitialized memory where the wrapped value used to live.

This can be used together with write to reuse the allocation for multiple boxed values.

§Examples

let c = Box::new(5);

// take the value out of the box
let (value, uninit) = Box::take(c);
assert_eq!(value, 5);

// reuse the box for a second value
let c = Box::write(uninit, 6);
assert_eq!(*c, 6);

1.100.0 · Source

pub fn map(this: Box<T, A>, f: impl FnOnce(T) -> U) -> Box<U, A>

Maps the value in a box, reusing the allocation if possible.

f is called on the value in the box, and the result is returned, also boxed.

Note: this is an associated function, which means that you have to call it as Box::map(b, f) instead of b.map(f). This is so that there is no conflict with a method on the inner type.

§Examples

let b = Box::new(7);
let new = Box::map(b, |i| i + 7);
assert_eq!(*new, 14);

Source

pub fn try_map<R>( this: Box<T, A>, f: impl FnOnce(T) -> R, ) -> <<R as Try>::Residual as Residual<Box<<R as Try>::Output, A>>>::TryType
where R: Try, <R as Try>::Residual: Residual<Box<<R as Try>::Output, A>>,

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

Attempts to map the value in a box, reusing the allocation if possible.

f is called on the value in the box, and if the operation succeeds, the result is returned, also boxed.

Note: this is an associated function, which means that you have to call it as Box::try_map(b, f) instead of b.try_map(f). This is so that there is no conflict with a method on the inner type.

§Examples

#![feature(smart_pointer_try_map)]

let b = Box::new(7);
let new = Box::try_map(b, u32::try_from).unwrap();
assert_eq!(*new, 7);

Source §

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

Source

pub fn clone_from_ref(src: &T) -> Box<T>

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

Allocates memory on the heap then clones src into it.

This doesn’t actually allocate if src is zero-sized. See the memory layout section for more details.

§Examples

#![feature(clone_from_ref)]

let hello: Box<str> = Box::clone_from_ref("hello");

Source

pub fn try_clone_from_ref(src: &T) -> Result<Box<T>, AllocError>

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

Allocates memory on the heap then clones src into it, returning an error if allocation fails.

This doesn’t actually allocate if src is zero-sized. See the memory layout section for more details.

§Examples

#![feature(clone_from_ref)]

let hello: Box<str> = Box::try_clone_from_ref("hello")?;

Source §

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

Source

pub fn clone_from_ref_in(src: &T, alloc: A) -> Box<T, A>

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

Allocates memory in the given allocator then clones src into it.

This doesn’t actually allocate if src is zero-sized. See the memory layout section for more details.

§Examples

#![feature(clone_from_ref)]

use std::alloc::System;

let hello: Box<str, System> = Box::clone_from_ref_in("hello", System);

Source

pub fn try_clone_from_ref_in(src: &T, alloc: A) -> Result<Box<T, A>, AllocError>

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

Allocates memory in the given allocator then clones src into it, returning an error if allocation fails.

This doesn’t actually allocate if src is zero-sized. See the memory layout section for more details.

§Examples

#![feature(clone_from_ref)]

use std::alloc::System;

let hello: Box<str, System> = Box::try_clone_from_ref_in("hello", System)?;

Source §

impl<T> Box<[T]>

1.82.0 · Source

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

Constructs a new boxed slice with uninitialized contents.

§Examples

let mut values = Box::<[u32]>::new_uninit_slice(3);
// Deferred initialization:
values[0].write(1);
values[1].write(2);
values[2].write(3);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [1, 2, 3])

1.92.0 · Source

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

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

let values = Box::<[u32]>::new_zeroed_slice(3);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [0, 0, 0])

Source

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

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

Constructs a new boxed slice with uninitialized contents. Returns an error if the allocation fails.

§Examples

#![feature(allocator_ext)]

let mut values = Box::<[u32]>::try_new_uninit_slice(3)?;
// Deferred initialization:
values[0].write(1);
values[1].write(2);
values[2].write(3);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [1, 2, 3]);

Source

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

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

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_ext)]

let values = Box::<[u32]>::try_new_zeroed_slice(3)?;
let values = unsafe { values.assume_init() };

assert_eq!(*values, [0, 0, 0]);

Source §

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

Source

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

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

Constructs a new boxed slice with uninitialized contents in the provided allocator.

§Examples

#![feature(allocator_ext)]

use std::alloc::System;

let mut values = Box::<[u32], _>::new_uninit_slice_in(3, System);
// Deferred initialization:
values[0].write(1);
values[1].write(2);
values[2].write(3);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [1, 2, 3])

Source

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

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

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_ext)]

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])

Source

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

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

Constructs a new boxed slice with uninitialized contents in the provided allocator. Returns an error if the allocation fails.

§Examples

#![feature(allocator_ext)]

use std::alloc::System;

let mut values = Box::<[u32], _>::try_new_uninit_slice_in(3, System)?;
// Deferred initialization:
values[0].write(1);
values[1].write(2);
values[2].write(3);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [1, 2, 3]);

Source

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

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

Constructs a new boxed slice with uninitialized contents in the provided allocator, 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_ext)]

use std::alloc::System;

let values = Box::<[u32], _>::try_new_zeroed_slice_in(3, System)?;
let values = unsafe { values.assume_init() };

assert_eq!(*values, [0, 0, 0]);

Source

pub fn into_array<const N: usize>(self) -> Result<Box<[T; N], A>, Box<[T], A>>

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

Converts the boxed slice into a boxed array.

This operation does not reallocate; the underlying array of the slice is simply reinterpreted as an array type.

§Errors

Returns the original Box<[T]> in the Err variant if self.len() does not equal N.

§Examples

#![feature(alloc_slice_into_array)]
let box_slice: Box<[i32]> = Box::new([1, 2, 3]);

let box_array: Box<[i32; 3]> = box_slice.into_array().unwrap();

Source §

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

1.82.0 (const: unstable) · Source

pub unsafe fn assume_init(self) -> Box<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.

§Examples

let mut five = Box::<u32>::new_uninit();
// Deferred initialization:
five.write(5);
let five: Box<u32> = unsafe { five.assume_init() };

assert_eq!(*five, 5)

1.87.0 · Source

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

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

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);
}

Source §

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

1.82.0 · Source

pub unsafe fn assume_init(self) -> Box<[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.

§Examples

let mut values = Box::<[u32]>::new_uninit_slice(3);
// Deferred initialization:
values[0].write(1);
values[1].write(2);
values[2].write(3);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [1, 2, 3])

Source §

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 exact safety requirements are described in the memory layout section, together with recommendations about how to handle the special case of zero-sized allocations correctly.

In particular, if the size of the pointee, as reported by size_of_val, is nonzero, then the raw pointer must point to a block of memory allocated by Global. If the size of the pointee is zero, then the raw pointer can be any sufficiently aligned non-null pointer, e.g. ptr::dangling.

Note that the considerations for unsafe code apply to all Box<T> values.

§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);
}

1.99.0 · Source

pub unsafe fn from_non_null(ptr: NonNull<T>) -> Box<T>

Constructs a box from a NonNull pointer.

After calling this function, the NonNull 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 NonNull pointer.

The exact safety requirements are described in the memory layout section, together with recommendations about how to handle the special case of zero-sized allocations correctly.

In particular, if the size of the pointee, as reported by size_of_val, is nonzero, then the raw pointer must point to a block of memory allocated by Global. If the size of the pointee is zero, then the raw pointer can be any sufficiently aligned pointer, e.g. NonNull::dangling.

Note that the considerations for unsafe code apply to all Box<T> values.

§Examples

Recreate a Box which was previously converted to a NonNull pointer using Box::into_non_null:

let x = Box::new(5);
let non_null = Box::into_non_null(x);
let x = unsafe { Box::from_non_null(non_null) };

Manually create a Box from scratch by using the global allocator:

use std::alloc::{alloc, Layout};
use std::ptr::NonNull;

unsafe {
    let non_null = NonNull::new(alloc(Layout::new::<i32>()).cast::<i32>())
        .expect("alloc should have successfully allocated memory");
    // In general .write is required to avoid attempting to destruct
    // the (uninitialized) previous contents of `non_null`.
    non_null.write(5);
    let x = Box::from_non_null(non_null);
}

1.4.0 · Source

pub fn into_raw(b: Box<T>) -> *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.

While manually deallocating the pointer through deallocate is possible, you must only do this if the pointee’s size, as reported by size_of_val, is non-zero (the Box may be a dangling pointer otherwise). See the memory layout section for more details.

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));
}

1.99.0 · Source

pub fn into_non_null(b: Box<T>) -> NonNull<T>

Consumes the Box, returning a wrapped NonNull pointer.

The pointer will be properly aligned.

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 NonNull pointer back into a Box with the Box::from_non_null function, allowing the Box destructor to perform the cleanup.

While manually deallocating the pointer through deallocate is possible, you must only do this if the pointee’s size, as reported by size_of_val, is non-zero (the Box may be a dangling pointer otherwise). See the memory layout section for more details.

Note: this is an associated function, which means that you have to call it as Box::into_non_null(b) instead of b.into_non_null(). This is so that there is no conflict with a method on the inner type.

§Examples

Converting the NonNull pointer back into a Box with Box::from_non_null for automatic cleanup:

let x = Box::new(String::from("Hello"));
let non_null = Box::into_non_null(x);
let x = unsafe { Box::from_non_null(non_null) };

Manual cleanup by explicitly running the destructor and deallocating the memory:

use std::alloc::{dealloc, Layout};

let x = Box::new(String::from("Hello"));
let non_null = Box::into_non_null(x);
unsafe {
    non_null.drop_in_place();
    dealloc(non_null.as_ptr().cast::<u8>(), Layout::new::<String>());
}

Note: This is equivalent to the following:

let x = Box::new(String::from("Hello"));
let non_null = Box::into_non_null(x);
unsafe {
    drop(Box::from_non_null(non_null));
}

Source §

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

1.100.0 · Source

pub unsafe fn from_raw_in(raw: *mut T, alloc: A) -> 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, except in the cases described in the memory layout section.

§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 exact safety requirements are described in the memory layout section, together with recommendations about how to handle the special case of zero-sized allocations correctly.

In particular, if the size of the pointee, as reported by size_of_val, is nonzero, then the raw pointer must point to a block of memory allocated by alloc. If the size of the pointee is zero, then the raw pointer can be any sufficiently aligned non-null pointer, e.g. ptr::dangling.

Note that the considerations for unsafe code apply to all Box<T, A> values.

§Examples

Recreate a Box which was previously converted to a raw pointer using Box::into_raw_with_allocator:

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(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);
}

1.100.0 · Source

pub unsafe fn from_non_null_in(raw: NonNull<T>, alloc: A) -> Box<T, A>

Constructs a box from a NonNull pointer in the given allocator.

After calling this function, the NonNull pointer is owned by the resulting Box. Specifically, the Box destructor will call the destructor of T and free the allocated memory, except in the cases described in the memory layout section.

§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 exact safety requirements are described in the memory layout section, together with recommendations about how to handle the special case of zero-sized allocations correctly.

In particular, if the size of the pointee, as reported by size_of_val, is nonzero, then the raw pointer must point to a block of memory allocated by alloc. If the size of the pointee is zero, then the raw pointer can be any sufficiently aligned pointer, e.g. NonNull::dangling.

Note that the considerations for unsafe code apply to all Box<T, A> values.

§Examples

Recreate a Box which was previously converted to a NonNull pointer using Box::into_non_null_with_allocator:

use std::alloc::System;

let x = Box::new_in(5, System);
let (non_null, alloc) = Box::into_non_null_with_allocator(x);
let x = unsafe { Box::from_non_null_in(non_null, alloc) };

Manually create a Box from scratch by using the system allocator:

use std::alloc::{Allocator, Layout, System};

unsafe {
    let non_null = System.allocate(Layout::new::<i32>())?.cast::<i32>();
    // In general .write is required to avoid attempting to destruct
    // the (uninitialized) previous contents of `non_null`.
    non_null.write(5);
    let x = Box::from_non_null_in(non_null, System);
}

1.100.0 (const: unstable) · Source

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

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.

While manually deallocating the pointer through deallocate is possible, you must only do this if the pointee’s size, as reported by size_of_val, is non-zero (the Box may be a dangling pointer otherwise). See the memory layout section for more details.

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:

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:

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>());
}

1.100.0 · Source

pub fn into_non_null_with_allocator(b: Box<T, A>) -> (NonNull<T>, A)

Consumes the Box, returning a wrapped NonNull pointer and the allocator.

The pointer will be properly aligned.

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 NonNull pointer back into a Box with the Box::from_non_null_in function, allowing the Box destructor to perform the cleanup.

While manually deallocating the pointer through deallocate is possible, you must only do this if the pointee’s size, as reported by size_of_val, is non-zero (the Box may be a dangling pointer otherwise). See the memory layout section for more details.

Note: this is an associated function, which means that you have to call it as Box::into_non_null_with_allocator(b) instead of b.into_non_null_with_allocator(). This is so that there is no conflict with a method on the inner type.

§Examples

Converting the NonNull pointer back into a Box with Box::from_non_null_in for automatic cleanup:

use std::alloc::System;

let x = Box::new_in(String::from("Hello"), System);
let (non_null, alloc) = Box::into_non_null_with_allocator(x);
let x = unsafe { Box::from_non_null_in(non_null, alloc) };

Manual cleanup by explicitly running the destructor and deallocating the memory:

use std::alloc::{Allocator, Layout, System};

let x = Box::new_in(String::from("Hello"), System);
let (non_null, alloc) = Box::into_non_null_with_allocator(x);
unsafe {
    non_null.drop_in_place();
    alloc.deallocate(non_null.cast::<u8>(), Layout::new::<String>());
}

1.98.0 · Source

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

Returns a raw mutable pointer to the Box’s contents.

The caller must ensure that the Box outlives the pointer this function returns, or else it will end up dangling.

This method guarantees that for the purpose of the aliasing model, this method does not materialize a reference to the underlying memory, and thus the returned pointer will remain valid when mixed with other calls to as_ptr, as_mut_ptr, and as_non_null. Note that calling other methods that materialize references to the memory may still invalidate this pointer. See the example below for how this guarantee can be used.

§Examples

Due to the aliasing guarantee, the following code is legal:

unsafe {
    let mut b = Box::new(0);
    let ptr1 = Box::as_mut_ptr(&mut b);
    ptr1.write(1);
    let ptr2 = Box::as_mut_ptr(&mut b);
    ptr2.write(2);
    // Notably, the write to `ptr2` did *not* invalidate `ptr1`:
    ptr1.write(3);
}

1.98.0 · Source

pub fn as_ptr(b: &Box<T, A>) -> *const T

Returns a raw pointer to the Box’s contents.

The caller must ensure that the Box outlives the pointer this function returns, or else it will end up dangling.

The caller must also ensure that the memory the pointer (non-transitively) points to is never written to (except inside an UnsafeCell) using this pointer or any pointer derived from it. If you need to mutate the contents of the Box, use as_mut_ptr.

This method guarantees that for the purpose of the aliasing model, this method does not materialize a reference to the underlying memory, and thus the returned pointer will remain valid when mixed with other calls to as_ptr, as_mut_ptr, and as_non_null. Note that calling other methods that materialize mutable references to the memory, as well as writing to this memory, may still invalidate this pointer. See the example below for how this guarantee can be used.

§Examples

Due to the aliasing guarantee, the following code is legal:

unsafe {
    let mut v = Box::new(0);
    let ptr1 = Box::as_ptr(&v);
    let ptr2 = Box::as_mut_ptr(&mut v);
    let _val = ptr2.read();
    // No write to this memory has happened yet, so `ptr1` is still valid.
    let _val = ptr1.read();
    // However, once we do a write...
    ptr2.write(1);
    // ... `ptr1` is no longer valid.
    // This would be UB: let _val = ptr1.read();
}

Source

pub fn as_non_null(b: &mut Box<T, A>) -> NonNull<T>

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

Returns a NonNull pointer to the Box’s contents.

The caller must ensure that the Box outlives the pointer this function returns, or else it will end up dangling.

This method guarantees that for the purpose of the aliasing model, this method does not materialize a reference to the underlying memory, and thus the returned pointer will remain valid when mixed with other calls to as_ptr, as_mut_ptr, and as_non_null. Note that calling other methods that materialize references to the memory may still invalidate this pointer. See the example below for how this guarantee can be used.

§Examples

Due to the aliasing guarantee, the following code is legal:

#![feature(box_as_non_null)]

unsafe {
    let mut b = Box::new(0);
    let ptr1 = Box::as_non_null(&mut b);
    ptr1.write(1);
    let ptr2 = Box::as_non_null(&mut b);
    ptr2.write(2);
    // Notably, the write to `ptr2` did *not* invalidate `ptr1`:
    ptr1.write(3);
}

1.100.0 · Source

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

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, i.e., memory that is meant to leak. If the memory should eventually be freed, prefer to use Box::into_raw or Box::into_non_null instead. Reconstructing (“unleaking”) a Box from the mutable reference returned here (e.g. via Box::from_raw) is only possible if the allocator is Global, and even then it is a grey area (meaning it is possible under specific circumstances but many seemingly harmless ways of doing it are undefined behavior) and should be avoided.

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 · Source

pub fn into_pin(boxed: Box<T, A>) -> Pin<Box<T, A>>
where A: StaticAllocator,

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);

This implementation is required to make sure that the &mut Box<[I; N]>: IntoIterator implementation doesn’t overlap with IntoIterator for T where T: Iterator blanket.

1.100.0 · Source§

Attempts to shrink the memory block. Read more

Source §

Source §

type Parameters = StringParam

The type of parameters that arbitrary_with accepts for configuration of the generated Strategy. Parameters must implement Default.

Source §

type Strategy = MapInto<<String as Arbitrary>::Strategy, Box<str>>

The type of Strategy used to generate values of type Self.

Source §

fn arbitrary_with( a: <Box<str> as Arbitrary>::Parameters, ) -> <Box<str> as Arbitrary>::Strategy

Generates a Strategy for producing arbitrary values of type the implementing type (Self). The strategy is passed the arguments given in args. Read more

Source §

fn arbitrary() -> Self::Strategy

Generates a Strategy for producing arbitrary values of type the implementing type (Self). Read more

Source §

impl<A> ArbitraryF1<A> for Box<A>
where A: Debug + 'static,

Source §

type Parameters = ()

The type of parameters that lift1_with accepts for configuration of the lifted and generated Strategy. Parameters must implement Default.

Source §

fn lift1_with<S>( base: S, _args: <Box<A> as ArbitraryF1<A>>::Parameters, ) -> BoxedStrategy<Box<A>>
where S: Strategy<Value = A> + 'static,

Lifts a given Strategy to a new Strategy for the (presumably) bigger type. This is useful for lifting a Strategy for SomeType to a container such as Vec of SomeType. The composite strategy is passed the arguments given in args. Read more

Source §

fn lift1<AS>(base: AS) -> BoxedStrategy<Self>
where AS: Strategy<Value = A> + 'static,

Lifts a given Strategy to a new Strategy for the (presumably) bigger type. This is useful for lifting a Strategy for SomeType to a container such as Vec<SomeType>. Read more

impl<T> AsyncBufRead for Box<T>
where T: AsyncBufRead + Unpin + ?Sized,

Source §

fn poll_fill_buf( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, ) -> Poll<Result<&[u8], Error>>

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

Source §

fn consume(self: Pin<&mut Box<T>>, amt: usize)

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

Attempt to read from the AsyncRead into buf. Read more

Waits for a seek operation to complete. Read more

Source §

impl<T> AsyncWrite for Box<T>
where T: AsyncWrite + Unpin + ?Sized,

Source §

fn poll_write( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize, Error>>

Attempt to write bytes from buf into the object. Read more

Source §

fn poll_write_vectored( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

Attempt to write bytes from bufs into the object using vectored IO operations. Read more

Source §

fn poll_flush( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

Attempt to flush the object, ensuring that any buffered data reach their destination. Read more

Source §

fn poll_close( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

Attempt to close the object. Read more

Source §

Source §

type Data = <T as Body>::Data

Values yielded by the Body.

Source §

type Error = <T as Body>::Error

The error type this Body might generate.

Source §

fn poll_frame( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, ) -> Poll<Option<Result<Frame<<Box<T> as Body>::Data>, <Box<T> as Body>::Error>>>

Attempt to pull out the next frame of this stream. Read more

Source §

fn is_end_stream(&self) -> bool

A hint that may return true when the end of stream has been reached. Read more

1.0.0 · Source§

impl<B, A> BufRead for Box<B, A>
where B: BufRead + ?Sized, A: Allocator,

Source §

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

Returns the contents of the internal buffer, filling it with more data, via Read methods, if empty. Read more

Source §

fn consume(&mut self, amt: usize)

Marks the given amount of additional bytes from the internal buffer as having been read. Subsequent calls to read only return bytes that have not been marked as read. Read more

Source §

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

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

Available on non-no_global_oom_handling only.

Source §

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);

Source §

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

Available on non-no_global_oom_handling only.

Source §

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

Copies source’s contents into self without creating a new allocation, so long as the two are of the same length.

§Examples

let x = Box::new([5, 6, 7]);
let mut y = Box::new([8, 9, 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);

Source §

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

Returns a duplicate of the value. Read more

1.3.0 · Source§

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

fn clone(&self) -> Box<dyn ProgressTracker>

Returns a duplicate of the value. Read more

1.0.0 (const: unstable) · Source§

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

Performs copy-assignment from source. Read more

Source §

Source §

fn clone(&self) -> Box<Path<T>>

Returns a duplicate of the value. Read more

1.0.0 (const: unstable) · Source§

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

impl<C> Completer for Box<C>
where C: Completer + ?Sized,

Source §

type Candidate = <C as Completer>::Candidate

Specific completion candidate.

Source §

fn complete( &self, line: &str, pos: usize, ctx: &Context<'_>, ) -> Result<(usize, Vec<<Box<C> as Completer>::Candidate>), ReadlineError>

Takes the currently edited line with the cursor position and returns the start position and the completion candidates for the partial word to be completed. Read more

Source §

fn update( &self, line: &mut LineBuffer, start: usize, elected: &str, cl: &mut Changeset, )

Updates the edited line with the elected candidate.

Available on crate feature alloc only.

Source §

fn default() -> Box<BStr>

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

1.0.0 · Source§

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

Source §

type Target = T

The resulting type after dereferencing.

Deserialize this value from the given Serde deserializer. Read more

Source §

impl<'de> Deserialize<'de> for Box<RawValue>

Source §

fn deserialize<D>( deserializer: D, ) -> Result<Box<RawValue>, <D as Deserializer<'de>>::Error>
where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer. Read more

Source §

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

1.0.0 · Source§

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

Source §

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

Formats the value using the given formatter. Read more

1.0.0 · Source§

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

Source §

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

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

Source §

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

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

Source §

fn next_chunk_back<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)

Advances from the back of the iterator and returns an array containing the next N values in sequence. Read more

Source §

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

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

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

1.27.0 (const: unstable) · 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 (const: unstable) · 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 (const: unstable) · 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

1.0.0 · Source§

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

Source §

fn drop(&mut self)

Executes the destructor for this type. Read more

Source §

fn pin_drop(self: Pin<&mut Self>)

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

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned. Read more

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

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

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

1.0.0 · Source§

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

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

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

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

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

Performs the call operation.

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)

Converts to this type from the input type.

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impl<T> From<&Slice<T>> for Box<Slice<T>>
where T: Copy,

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fn from(slice: &Slice<T>) -> Box<Slice<T>>

Converts to this type from the input type.

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impl<T> From<&Utf8Path<T>> for Box<Utf8Path<T>>
where T: Utf8Encoding,

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fn from(path: &Utf8Path<T>) -> Box<Utf8Path<T>>

Creates a boxed Utf8Path from a reference.

This will allocate and clone path to it.

1.17.0 · Source§

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

Available on non-no_global_oom_handling only.

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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:?}");

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

1.0.0 · Source§

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

Available on non-no_global_oom_handling only.

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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;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error);
assert!(
    size_of::<Box<dyn Error + Send + Sync>>() == size_of_val(&a_boxed_error))

1.6.0 · Source§

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

Available on non-no_global_oom_handling only.

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

Converts a str into a box of dyn Error.

§Examples

use std::error::Error;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error>::from(a_str_error);
assert!(size_of::<Box<dyn Error>>() == size_of_val(&a_boxed_error))

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impl From<Box<BStr>> for Box<[u8]>

Available on crate feature alloc only.

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

Available on non-no_global_oom_handling only.

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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);

1.21.0 · Source§

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

Available on non-no_global_oom_handling only.

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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 + StaticAllocator, T: ?Sized,

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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.

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

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fn from(b: Box<T>) -> Atomic<T>

Converts to this type from the input type.

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

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Converts 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]);

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impl<T> From<Box<[T]>> for MaybeStaticSlice<T>
where T: 'static,

Available on crate feature alloc only.

Available on crate feature alloc only.

// 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);

1.18.0 · Source§

impl From<Box<str>> for String

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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)

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impl<const ARRAY_CAPACITY_MAX: usize> From<Box<str>> for SmallStr<ARRAY_CAPACITY_MAX>

Available on crate feature alloc only.

Return a SmallStr that is guaranteed to live on the heap.

Available on non-no_global_oom_handling only.

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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<'_, str>> for Box<str>

Available on non-no_global_oom_handling only.

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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 + Sync + Send + 'a>

Available on non-no_global_oom_handling only.

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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::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!(
    size_of::<Box<dyn Error + Send + Sync>>() == size_of_val(&a_boxed_error))

1.22.0 · Source§

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

Available on non-no_global_oom_handling only.

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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::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!(size_of::<Box<dyn Error>>() == size_of_val(&a_boxed_error))

1.0.0 · Source§

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

Available on non-no_global_oom_handling only.

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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;

#[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 == size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error>::from(an_error);
assert!(size_of::<Box<dyn Error>>() == size_of_val(&a_boxed_error))

1.0.0 · Source§

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

Available on non-no_global_oom_handling only.

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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;

#[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 == size_of_val(&an_error));
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error);
assert!(
    size_of::<Box<dyn Error + Send + Sync>>() == size_of_val(&a_boxed_error))

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;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error);
assert!(
    size_of::<Box<dyn Error + Send + Sync>>() == size_of_val(&a_boxed_error))

1.6.0 · Source§

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

Available on non-no_global_oom_handling only.

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

Converts a String into a box of dyn Error.

§Examples

use std::error::Error;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error>::from(a_string_error);
assert!(size_of::<Box<dyn Error>>() == size_of_val(&a_boxed_error))

1.20.0 · Source§

impl From<String> for Box<str>

Available on non-no_global_oom_handling only.

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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>

Available on non-no_global_oom_handling only.

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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);

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impl<T> From<Utf8PathBuf<T>> for Box<Utf8Path<T>>
where T: Utf8Encoding,

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fn from(p: Utf8PathBuf<T>) -> Box<Utf8Path<T>>

Converts a Utf8PathBuf into a Box<Utf8Path>.

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

1.20.0 · Source§

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

Available on non-no_global_oom_handling only.

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

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

Available on non-no_global_oom_handling only.

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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:?}");

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Creates an instance of the collection from the parallel iterator par_iter. Read more

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impl<F> FusedFuture for Box<F>
where F: FusedFuture + Unpin + ?Sized,

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fn is_terminated(&self) -> bool

Returns true if the underlying future should no longer be polled.

1.26.0 · Source§

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

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Advances the iterator and returns the next value. Read more

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

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

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

1.0.0 (const: unstable) · Source§

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

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fn intersperse(self, separator: Self::Item) -> Intersperse<Self> ⓘ
where Self: Sized, Self::Item: Clone,

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

Creates a new iterator which places a copy of separator between items of the original iterator. Read more

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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)

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

1.0.0 (const: unstable) · Source§

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 (const: unstable) · 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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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 (const: unstable) · 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

1.0.0 (const: unstable) · Source§

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

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

1.29.0 (const: unstable) · Source§

fn flatten(self) -> Flatten<Self> ⓘ
where Self: Sized, Self::Item: IntoIterator,

Creates an iterator that flattens nested structure. Read more

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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)

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

1.0.0 (const: unstable) · Source§

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

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

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

1.0.0 (const: unstable) · Source§

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

Transforms an iterator into a collection. Read more

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fn try_collect( &mut self, ) -> <<Self::Item as Try>::Residual as Residual>::TryType
where Self: Sized, Self::Item: Try, <Self::Item as Try>::Residual: Residual, B: FromIterator<<Self::Item as Try>::Output>,

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

Fallibly transforms an iterator into a collection, short circuiting if a failure is encountered. Read more

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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)

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

1.0.0 (const: unstable) · Source§

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

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fn partition_in_place<'a, T, P>(self, predicate: P) -> usize
where T: 'a, Self: Sized + DoubleEndedIterator<Item = &'a mut T>, P: FnMut(&T) -> bool,

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

Reorders the elements of this iterator in-place according to the given predicate, such that all those that return true precede all those that return false. Returns the number of true elements found. Read more

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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)

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 (const: unstable) · 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 (const: unstable) · 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

1.0.0 (const: unstable) · Source§

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 (const: unstable) · 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

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

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

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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 (const: unstable) · 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

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

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

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

1.0.0 (const: unstable) · Source§

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

1.0.0 (const: unstable) · Source§

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

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

1.0.0 (const: unstable) · Source§

fn max(self) -> Option<Self::Item>
where Self: Sized, Self::Item: Ord,

Returns the maximum element of an iterator. Read more

1.0.0 (const: unstable) · Source§

fn min(self) -> Option<Self::Item>
where Self: Sized, Self::Item: Ord,

Returns the minimum element of an iterator. Read more

1.6.0 (const: unstable) · 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 (const: unstable) · 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 (const: unstable) · 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 (const: unstable) · 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

1.0.0 (const: unstable) · Source§

fn rev(self) -> Rev<Self> ⓘ
where Self: Sized + DoubleEndedIterator,

Reverses an iterator’s direction. Read more

1.0.0 (const: unstable) · Source§

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 (const: unstable) · Source§

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

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

1.0.0 (const: unstable) · 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

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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)

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 (const: unstable) · 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 (const: unstable) · 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 (const: unstable) · 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 (const: unstable) · 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 (const: unstable) · 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

1.82.0 (const: unstable) · Source§

fn is_sorted(self) -> bool
where Self: Sized, Self::Item: PartialOrd,

Checks if the elements of this iterator are sorted. Read more

1.82.0 (const: unstable) · Source§

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

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

1.82.0 (const: unstable) · Source§

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

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

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Flushes any buffered records. Read more

1.0.0 · Source§

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

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

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

1.21.0 (const: unstable) · Source§

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

Compares and returns the maximum of two values. Read more

1.21.0 (const: unstable) · Source§

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

Compares and returns the minimum of two values. Read more

1.50.0 (const: unstable) · Source§

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

Restrict a value to a certain interval. Read more

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fn clamp_to<R>(self, range: R) -> Self
where Self: Sized, R: ClampBounds<Self>,

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

Restrict a value to a certain range. Read more

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impl ParallelExtend<Box<str>> for String

Extends a string with boxed strings from a parallel iterator.

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fn par_extend(&mut self, par_iter: I)
where I: IntoParallelIterator<Item = Box<str>>,

Extends an instance of the collection with the elements drawn from the parallel iterator par_iter. Read more

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

Equality operator ==. Read more

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

Inequality operator !=. Read more

1.0.0 · Source§

1.0.0 · Source§

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

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

Formats the value using the given formatter. Read more

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impl<B, E, P> Policy<B, E> for Box
where P: Policy<B, E> + ?Sized,

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fn redirect(&mut self, attempt: &Attempt<'_>) -> Result<Action, E>

Invoked when the service received a response with a redirection status code (3xx). Read more

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fn on_request(&mut self, request: &mut Request)

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

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

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fn read_buf_exact( &mut self, cursor: BorrowedCursor<'_, u8>, ) -> Result<(), Error>

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

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

1.0.0 · Source§

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

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

1.0.0 · Source§

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

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

1.0.0 · Source§

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

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

1.0.0 · Source§

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fn poll_read( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, buf: ReadBufCursor<'_>, ) -> Poll<Result<(), Error>>

Attempts to read bytes into the buf. Read more

fn next_f64(&mut self) -> f64

Generate a random f64 between [0, 1).

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fn next_range(&mut self, range: Range<u64>) -> u64

Randomly pick a value within the range. Read more

1.0.0 · Source§

impl<S, A> Seek for Box<S, A>
where S: Seek + ?Sized, A: Allocator,

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

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

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

Rewind to the beginning of a stream. Read more

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

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

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

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

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

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

Seeks relative to the current position. Read more

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impl<T> Serialize for Box<T>
where T: Serialize + ?Sized,

Available on crate features alloc or std only.

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fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>
where S: Serializer,

Serialize this value into the given Serde serializer. Read more

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type Response = <S as Service<Request>>::Response

Responses given by the service.

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type Error = <S as Service<Request>>::Error

Errors produced by the service. Read more

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type Future = <S as Service<Request>>::Future

The future response value.

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fn call(&self, req: Request) -> <Box<S> as Service<Request>>::Future

Process the request and return the response asynchronously. call takes &self instead of mut &self because: Read more

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fn register( &mut self, registry: &Registry, token: Token, interests: Interest, ) -> Result<(), Error>

Register self with the given Registry instance. Read more

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fn reregister( &mut self, registry: &Registry, token: Token, interests: Interest, ) -> Result<(), Error>

Re-register self with the given Registry instance. Read more

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fn deregister(&mut self, registry: &Registry) -> Result<(), Error>

Deregister self from the given Registry instance. Read more

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impl<Sp> Spawn for Box<Sp>
where Sp: Spawn + ?Sized,

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fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError>

Spawns a future that will be run to completion. Read more

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fn status(&self) -> Result<(), SpawnError>

Determines whether the executor is able to spawn new tasks. Read more

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type Item = <S as Stream>::Item

Values yielded by the stream.

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

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

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

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

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

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fn augment_subcommands(cmd: Command) -> Command

Append to Command so it can instantiate Self via FromArgMatches::from_arg_matches_mut Read more

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fn augment_subcommands_for_update(cmd: Command) -> Command

Append to Command so it can instantiate self via FromArgMatches::update_from_arg_matches_mut Read more

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fn has_subcommand(name: &str) -> bool

Test whether Self can parse a specific subcommand

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Notifies the subscriber that a span ID has been dropped, and returns true if there are now 0 IDs that refer to that span. Read more

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fn drop_span(&self, id: Id)

👎Deprecated since 0.1.2:

use Subscriber::try_close instead

This method is deprecated. Read more

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fn current_span(&self) -> Current

Returns a type representing this subscriber’s view of the current span. Read more

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unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()>

If self is the same type as the provided TypeId, returns an untyped *const pointer to that type. Otherwise, returns None. Read more

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fn on_register_dispatch(&self, subscriber: &Dispatch)

Invoked when this subscriber becomes a Dispatch. Read more

fn to_token_stream(&self) -> TokenStream

Convert self directly into a TokenStream object. Read more

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fn into_token_stream(self) -> TokenStream
where Self: Sized,

Convert self directly into a TokenStream object. Read more

1.43.0 · Source§

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);

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type Error = Vec<T, A>

The type returned in the event of a conversion error.

1.33.0 · Source§

Returns the current value.

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fn simplify(&mut self) -> bool

Attempts to simplify the current value. Notionally, this sets the “high” value to the current value, and the current value to a “halfway point” between high and low, rounding towards low. Read more

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fn complicate(&mut self) -> bool

Attempts to partially undo the last simplification. Notionally, this sets the “low” value to one plus the current value, and the current value to a “halfway point” between high and the new low, rounding towards low. Read more

Blanket Implementations§

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

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more

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impl<F, T, U, R, E> AsyncPredicate<T> for F
where F: FnMut(T) -> U, U: Future<Output = Result<R, E>>, E: Into<Box<dyn Error + Sync + Send>>,

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type Future = ErrInto<U, Box<dyn Error + Sync + Send>>

The future returned by check.

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type Request = R

The type of requests returned by check. Read more

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fn check(&mut self, request: T) -> <F as AsyncPredicate<T>>::Future

Check whether the given request should be forwarded. Read more

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Creates an AsyncRead adapter which will read at most limit bytes from the underlying reader. Read more

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fn seek(&mut self, pos: SeekFrom) -> Seek<'_, Self> ⓘ
where Self: Unpin,

Creates a future which will seek an IO object, and then yield the new position in the object and the object itself. Read more

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fn stream_position(&mut self) -> Seek<'_, Self> ⓘ
where Self: Unpin,

Creates a future which will return the current seek position from the start of the stream. Read more

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impl<S> AsyncSeekExt for S
where S: AsyncSeek + ?Sized,

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fn seek(&mut self, pos: SeekFrom) -> Seek<'_, Self>
where Self: Unpin,

Creates a future which will seek an IO object, and then yield the new position in the object and the object itself. Read more

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fn rewind(&mut self) -> Seek<'_, Self>
where Self: Unpin,

Creates a future which will rewind to the beginning of the stream. Read more

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fn stream_position(&mut self) -> Seek<'_, Self>
where Self: Unpin,

Creates a future which will return the current seek position from the start of the stream. Read more

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Allow using an AsyncWrite as a Sink<Item: AsRef<[u8]>>. Read more

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Returns an iterator over byte-terminated records of this reader, where each record is represented as a byte string. Read more

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fn for_byte_line<F>(&mut self, for_each_line: F) -> Result<(), Error>
where Self: Sized, F: FnMut(&[u8]) -> Result<bool, Error>,

Executes the given closure on each line in the underlying reader. Read more

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fn for_byte_record<F>( &mut self, terminator: u8, for_each_record: F, ) -> Result<(), Error>
where Self: Sized, F: FnMut(&[u8]) -> Result<bool, Error>,

Executes the given closure on each byte-terminated record in the underlying reader. Read more

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fn for_byte_line_with_terminator<F>( &mut self, for_each_line: F, ) -> Result<(), Error>
where Self: Sized, F: FnMut(&[u8]) -> Result<bool, Error>,

Executes the given closure on each line in the underlying reader. Read more

Text to insert in line.

Compare self to key and return their ordering.

impl<R> CryptoRng for R
where R: TryCryptoRng<Error = !> + ?Sized,

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impl<T> CryptoRng for T
where T: DerefMut, <T as Deref>::Target: CryptoRng,

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impl<T> DeserializeOwned for T
where T: for<'de> Deserialize<'de>,

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impl<K, S, E, D> Discover for D
where D: TryStream<Ok = Change<K, S>, Error = E> + ?Sized, K: Eq,

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type Key = K

A unique identifier for each active service. Read more

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type Service = S

The type of Service yielded by this Discover.

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type Error = E

Error produced during discovery

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fn report_error(&mut self, error: ParseError)

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impl<F> EventHandler for F
where F: FnMut(Result<Event, Error>) + Send + 'static,

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fn handle_event(&mut self, event: Result<Event, Error>)

Handles an event.

Returns if entering the inline table is allowed

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fn inline_table_close(&mut self, span: Span, _error: &mut dyn ErrorSink)

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fn array_open(&mut self, span: Span, _error: &mut dyn ErrorSink) -> bool

Returns if entering the array is allowed

The filter function type definition

Whether the current function’s output should be treated as safe, defaults to false Only needs to be defined if the filter returns a string

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type Future = <T as Service<Request<B1>>>::Future

The Future returned by this Service.

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fn call(&mut self, req: Request<B1>) -> <T as HttpService<B1>>::Future

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self> ⓘ

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more

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fn in_current_span(self) -> Instrumented<Self> ⓘ

Instruments this type with the current Span, returning an Instrumented wrapper. Read more

Uniformly sample one element (stable) Read more

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fn sample_fill<R>(self, rng: &mut R, buf: &mut [Self::Item]) -> usize
where R: Rng + ?Sized,

Uniformly sample amount distinct elements into a buffer Read more

Uniformly sample one element (stable) Read more

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fn choose_multiple_fill<R>(self, rng: &mut R, buf: &mut [Self::Item]) -> usize
where R: Rng + ?Sized,

Uniformly sample amount distinct elements into a buffer Read more

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fn choose_multiple<R>(self, rng: &mut R, amount: usize) -> Vec<Self::Item>
where R: Rng + ?Sized,

Uniformly sample amount distinct elements into a Vec Read more

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👎Deprecated since 0.13.0:

Use .chunk_by() instead

👎Deprecated since 0.15.0:

Use .array_combinations() instead

👎Deprecated since 0.10.2:

Use Iterator::reduce instead

Accumulator of the elements in the iterator. Read more

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

Accumulate the elements in the iterator in a tree-like manner. Read more

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fn tree_fold1<F>(self, f: F) -> Option<Self::Item>
where F: FnMut(Self::Item, Self::Item) -> Self::Item, Self: Sized,

👎Deprecated since 0.13.0:

Use .tree_reduce() instead

Removes a prefix from the iterator using eq to compare items. Read more

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Fold Option values from an iterator. Read more

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fn fold1<F>(self, f: F) -> Option<Self::Item>
where F: FnMut(Self::Item, Self::Item) -> Self::Item, Self: Sized,

👎Deprecated since 0.10.2:

Use Iterator::reduce instead

Accumulator of the elements in the iterator. Read more

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

Accumulate the elements in the iterator in a tree-like manner. Read more

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fn tree_fold1<F>(self, f: F) -> Option<Self::Item>
where F: FnMut(Self::Item, Self::Item) -> Self::Item, Self: Sized,

👎Deprecated since 0.13.0:

Use .tree_reduce() instead

Use .chunk_by() instead

👎Deprecated since 0.10.2:

Use Iterator::reduce instead

Accumulator of the elements in the iterator. Read more

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

Accumulate the elements in the iterator in a tree-like manner. Read more

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fn tree_fold1<F>(self, f: F) -> Option<Self::Item>
where F: FnMut(Self::Item, Self::Item) -> Self::Item, Self: Sized,

👎Deprecated since 0.13.0:

Use .tree_reduce() instead

Returns the length of the iterator if one exists. Otherwise return self.size_hint(). Read more

fn spawn_local_with_handle<Fut>( &self, future: Fut, ) -> Result<RemoteHandle<<Fut as Future>::Output>, SpawnError>
where Fut: Future + 'static,

Spawns a task that polls the given future to completion and returns a future that resolves to the spawned future’s output. Read more

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Call the callback.

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impl<T> ParallelBridge for T
where T: Iterator + Send, <T as Iterator>::Item: Send,

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fn par_bridge(self) -> IterBridge<T>

Creates a bridge from this type to a ParallelIterator.

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impl<F, T> Parser for F
where F: FnOnce(&ParseBuffer<'_>) -> Result<T, Error>,

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type Output = T

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fn parse2(self, tokens: TokenStream) -> Result<T, Error>

automatically converts the parser’s output and error values to another type, as long as they implement the From trait

Drops the object pointed to by the given pointer. Read more

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

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fn and<P, B, E>(self, other: P) -> And<T, P>
where T: Sized + Policy<B, E>, P: Policy<B, E>,

Create a new Policy that returns Action::Follow only if self and other return Action::Follow. Read more

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fn or<P, B, E>(self, other: P) -> Or<T, P>
where T: Sized + Policy<B, E>, P: Policy<B, E>,

Create a new Policy that returns Action::Follow if either self or other returns Action::Follow. Read more

fn check( &mut self, request: T, ) -> Result<<F as Predicate<T>>::Request, Box<dyn Error + Sync + Send>>

Check whether the given request should be forwarded. Read more

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fn clone_box(&self) -> Box<dyn ProgressTracker>

Creates a new instance of the progress tracker

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fn tick(&mut self, _: &ProgressState, _: Instant)

Notifies the progress tracker of a tick event

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fn reset(&mut self, _: &ProgressState, _: Instant)

Notifies the progress tracker of a reset event

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fn write(&self, state: &ProgressState, w: &mut dyn Write)

Provides access to the progress bar display buffer for custom messages

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impl<T> Read<Exclusive, BecauseExclusive> for T
where T: ?Sized,

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Reads a IEEE754 double-precision (8 bytes) floating point number from the underlying reader. Read more

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