Expand description
A pointer type for heap allocation.
See the module-level documentation for more.
Implementations
sourceimpl<T> Box<T>
impl<T> Box<T>
sourcepub fn new_uninit() -> Box<MaybeUninit<T>>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn new_uninit() -> Box<MaybeUninit<T>>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
sourcepub fn new_zeroed() -> Box<MaybeUninit<T>>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn new_zeroed() -> Box<MaybeUninit<T>>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(new_uninit)]
let zero = Box::<u32>::new_zeroed();
let zero = unsafe { zero.assume_init() };
assert_eq!(*zero, 0)
Run1.33.0 · sourcepub fn pin(x: T) -> Pin<Box<T>>
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
.
sourcepub fn try_new(x: T) -> Result<Self, AllocError>
pub fn try_new(x: T) -> Result<Self, AllocError>
sourcepub fn try_new_uninit() -> Result<Box<MaybeUninit<T>>, AllocError>
pub fn try_new_uninit() -> Result<Box<MaybeUninit<T>>, AllocError>
Constructs a new box with uninitialized contents on the heap, returning an error if the allocation fails
Examples
#![feature(allocator_api, new_uninit)]
let mut five = Box::<u32>::try_new_uninit()?;
let five = unsafe {
// Deferred initialization:
five.as_mut_ptr().write(5);
five.assume_init()
};
assert_eq!(*five, 5);
Runsourcepub fn try_new_zeroed() -> Result<Box<MaybeUninit<T>>, AllocError>
pub fn try_new_zeroed() -> Result<Box<MaybeUninit<T>>, AllocError>
Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes on the heap
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(allocator_api, new_uninit)]
let zero = Box::<u32>::try_new_zeroed()?;
let zero = unsafe { zero.assume_init() };
assert_eq!(*zero, 0);
Runsourceimpl<T, A: Allocator> Box<T, A>
impl<T, A: Allocator> Box<T, A>
const: unstable · sourcepub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError> where
A: Allocator,
pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError> where
A: Allocator,
const: unstable · sourcepub fn new_uninit_in(alloc: A) -> Box<MaybeUninit<T>, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
where
A: Allocator,
pub fn new_uninit_in(alloc: A) -> Box<MaybeUninit<T>, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
where
A: Allocator,
A: 'static, type Output = F::Output;
Constructs a new box with uninitialized contents in the provided allocator.
Examples
#![feature(allocator_api, new_uninit)]
use std::alloc::System;
let mut five = Box::<u32, _>::new_uninit_in(System);
let five = unsafe {
// Deferred initialization:
five.as_mut_ptr().write(5);
five.assume_init()
};
assert_eq!(*five, 5)
Runconst: unstable · sourcepub fn try_new_uninit_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError> where
A: Allocator,
pub fn try_new_uninit_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError> where
A: Allocator,
Constructs a new box with uninitialized contents in the provided allocator, returning an error if the allocation fails
Examples
#![feature(allocator_api, new_uninit)]
use std::alloc::System;
let mut five = Box::<u32, _>::try_new_uninit_in(System)?;
let five = unsafe {
// Deferred initialization:
five.as_mut_ptr().write(5);
five.assume_init()
};
assert_eq!(*five, 5);
Runconst: unstable · sourcepub fn new_zeroed_in(alloc: A) -> Box<MaybeUninit<T>, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
where
A: Allocator,
pub fn new_zeroed_in(alloc: A) -> Box<MaybeUninit<T>, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
where
A: Allocator,
A: 'static, type Output = F::Output;
Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes in the provided allocator.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(allocator_api, new_uninit)]
use std::alloc::System;
let zero = Box::<u32, _>::new_zeroed_in(System);
let zero = unsafe { zero.assume_init() };
assert_eq!(*zero, 0)
Runconst: unstable · sourcepub fn try_new_zeroed_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError> where
A: Allocator,
pub fn try_new_zeroed_in(alloc: A) -> Result<Box<MaybeUninit<T>, A>, AllocError> where
A: Allocator,
Constructs a new Box
with uninitialized contents, with the memory
being filled with 0
bytes in the provided allocator,
returning an error if the allocation fails,
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(allocator_api, new_uninit)]
use std::alloc::System;
let zero = Box::<u32, _>::try_new_zeroed_in(System)?;
let zero = unsafe { zero.assume_init() };
assert_eq!(*zero, 0);
Runconst: unstable · sourcepub fn pin_in(x: T, alloc: A) -> Pin<Self> where
A: 'static + Allocator,
pub fn pin_in(x: T, alloc: A) -> Pin<Self> where
A: 'static + Allocator,
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
.
const: unstable · sourcepub fn into_boxed_slice(boxed: Self) -> Box<[T], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn into_boxed_slice(boxed: Self) -> Box<[T], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Converts a Box<T>
into a Box<[T]>
This conversion does not allocate on the heap and happens in place.
sourceimpl<T> Box<[T]>
impl<T> Box<[T]>
sourcepub fn new_uninit_slice(len: usize) -> Box<[MaybeUninit<T>]>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn new_uninit_slice(len: usize) -> Box<[MaybeUninit<T>]>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Constructs a new boxed slice with uninitialized contents.
Examples
#![feature(new_uninit)]
let mut values = Box::<[u32]>::new_uninit_slice(3);
let values = unsafe {
// Deferred initialization:
values[0].as_mut_ptr().write(1);
values[1].as_mut_ptr().write(2);
values[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3])
Runsourcepub fn new_zeroed_slice(len: usize) -> Box<[MaybeUninit<T>]>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn new_zeroed_slice(len: usize) -> Box<[MaybeUninit<T>]>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Constructs a new boxed slice with uninitialized contents, with the memory
being filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(new_uninit)]
let values = Box::<[u32]>::new_zeroed_slice(3);
let values = unsafe { values.assume_init() };
assert_eq!(*values, [0, 0, 0])
Runsourcepub fn try_new_uninit_slice(
len: usize
) -> Result<Box<[MaybeUninit<T>]>, AllocError>
pub fn try_new_uninit_slice(
len: usize
) -> Result<Box<[MaybeUninit<T>]>, AllocError>
Constructs a new boxed slice with uninitialized contents. Returns an error if the allocation fails
Examples
#![feature(allocator_api, new_uninit)]
let mut values = Box::<[u32]>::try_new_uninit_slice(3)?;
let values = unsafe {
// Deferred initialization:
values[0].as_mut_ptr().write(1);
values[1].as_mut_ptr().write(2);
values[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3]);
Runsourcepub fn try_new_zeroed_slice(
len: usize
) -> Result<Box<[MaybeUninit<T>]>, AllocError>
pub fn try_new_zeroed_slice(
len: usize
) -> Result<Box<[MaybeUninit<T>]>, AllocError>
Constructs a new boxed slice with uninitialized contents, with the memory
being filled with 0
bytes. Returns an error if the allocation fails
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(allocator_api, new_uninit)]
let values = Box::<[u32]>::try_new_zeroed_slice(3)?;
let values = unsafe { values.assume_init() };
assert_eq!(*values, [0, 0, 0]);
Runsourceimpl<T, A: Allocator> Box<[T], A>
impl<T, A: Allocator> Box<[T], A>
sourcepub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Constructs a new boxed slice with uninitialized contents in the provided allocator.
Examples
#![feature(allocator_api, new_uninit)]
use std::alloc::System;
let mut values = Box::<[u32], _>::new_uninit_slice_in(3, System);
let values = unsafe {
// Deferred initialization:
values[0].as_mut_ptr().write(1);
values[1].as_mut_ptr().write(2);
values[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3])
Runsourcepub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[MaybeUninit<T>], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Constructs a new boxed slice with uninitialized contents in the provided allocator,
with the memory being filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(allocator_api, new_uninit)]
use std::alloc::System;
let values = Box::<[u32], _>::new_zeroed_slice_in(3, System);
let values = unsafe { values.assume_init() };
assert_eq!(*values, [0, 0, 0])
Runsourceimpl<T, A: Allocator> Box<MaybeUninit<T>, A>
impl<T, A: Allocator> Box<MaybeUninit<T>, A>
const: unstable · sourcepub unsafe fn assume_init(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub unsafe fn assume_init(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Converts to Box<T, A>
.
Safety
As with MaybeUninit::assume_init
,
it is up to the caller to guarantee that the value
really is in an initialized state.
Calling this when the content is not yet fully initialized
causes immediate undefined behavior.
Examples
#![feature(new_uninit)]
let mut five = Box::<u32>::new_uninit();
let five: Box<u32> = unsafe {
// Deferred initialization:
five.as_mut_ptr().write(5);
five.assume_init()
};
assert_eq!(*five, 5)
Runconst: unstable · sourcepub fn write(boxed: Self, value: T) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub fn write(boxed: Self, value: T) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Writes the value and converts to Box<T, A>
.
This method converts the box similarly to Box::assume_init
but
writes value
into it before conversion thus guaranteeing safety.
In some scenarios use of this method may improve performance because
the compiler may be able to optimize copying from stack.
Examples
#![feature(new_uninit)]
let big_box = Box::<[usize; 1024]>::new_uninit();
let mut array = [0; 1024];
for (i, place) in array.iter_mut().enumerate() {
*place = i;
}
// The optimizer may be able to elide this copy, so previous code writes
// to heap directly.
let big_box = Box::write(big_box, array);
for (i, x) in big_box.iter().enumerate() {
assert_eq!(*x, i);
}
Runsourceimpl<T, A: Allocator> Box<[MaybeUninit<T>], A>
impl<T, A: Allocator> Box<[MaybeUninit<T>], A>
sourcepub unsafe fn assume_init(self) -> Box<[T], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub unsafe fn assume_init(self) -> Box<[T], A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Converts to Box<[T], A>
.
Safety
As with MaybeUninit::assume_init
,
it is up to the caller to guarantee that the values
really are in an initialized state.
Calling this when the content is not yet fully initialized
causes immediate undefined behavior.
Examples
#![feature(new_uninit)]
let mut values = Box::<[u32]>::new_uninit_slice(3);
let values = unsafe {
// Deferred initialization:
values[0].as_mut_ptr().write(1);
values[1].as_mut_ptr().write(2);
values[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3])
Runsourceimpl<T: ?Sized> Box<T>
impl<T: ?Sized> Box<T>
1.4.0 · sourcepub unsafe fn from_raw(raw: *mut T) -> Self
pub unsafe fn from_raw(raw: *mut T) -> Self
Constructs a box from a raw pointer.
After calling this function, the raw pointer is owned by the
resulting Box
. Specifically, the Box
destructor will call
the destructor of T
and free the allocated memory. For this
to be safe, the memory must have been allocated in accordance
with the memory layout used by Box
.
Safety
This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.
The safety conditions are described in the memory layout section.
Examples
Recreate a Box
which was previously converted to a raw pointer
using Box::into_raw
:
let x = Box::new(5);
let ptr = Box::into_raw(x);
let x = unsafe { Box::from_raw(ptr) };
RunManually 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);
}
Runsourceimpl<T: ?Sized, A: Allocator> Box<T, A>
impl<T: ?Sized, A: Allocator> Box<T, A>
const: unstable · sourcepub unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self
pub unsafe fn from_raw_in(raw: *mut T, alloc: A) -> Self
Constructs a box from a raw pointer in the given allocator.
After calling this function, the raw pointer is owned by the
resulting Box
. Specifically, the Box
destructor will call
the destructor of T
and free the allocated memory. For this
to be safe, the memory must have been allocated in accordance
with the memory layout used by Box
.
Safety
This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.
Examples
Recreate a Box
which was previously converted to a raw pointer
using Box::into_raw_with_allocator
:
#![feature(allocator_api)]
use std::alloc::System;
let x = Box::new_in(5, System);
let (ptr, alloc) = Box::into_raw_with_allocator(x);
let x = unsafe { Box::from_raw_in(ptr, alloc) };
RunManually create a Box
from scratch by using the system allocator:
#![feature(allocator_api, slice_ptr_get)]
use std::alloc::{Allocator, Layout, System};
unsafe {
let ptr = System.allocate(Layout::new::<i32>())?.as_mut_ptr() as *mut i32;
// In general .write is required to avoid attempting to destruct
// the (uninitialized) previous contents of `ptr`, though for this
// simple example `*ptr = 5` would have worked as well.
ptr.write(5);
let x = Box::from_raw_in(ptr, System);
}
Run1.4.0 · sourcepub fn into_raw(b: Self) -> *mut T
pub fn into_raw(b: Self) -> *mut T
Consumes the Box
, returning a wrapped raw pointer.
The pointer will be properly aligned and non-null.
After calling this function, the caller is responsible for the
memory previously managed by the Box
. In particular, the
caller should properly destroy T
and release the memory, taking
into account the memory layout used by Box
. The easiest way to
do this is to convert the raw pointer back into a Box
with the
Box::from_raw
function, allowing the Box
destructor to perform
the cleanup.
Note: this is an associated function, which means that you have
to call it as Box::into_raw(b)
instead of b.into_raw()
. This
is so that there is no conflict with a method on the inner type.
Examples
Converting the raw pointer back into a Box
with Box::from_raw
for automatic cleanup:
let x = Box::new(String::from("Hello"));
let ptr = Box::into_raw(x);
let x = unsafe { Box::from_raw(ptr) };
RunManual cleanup by explicitly running the destructor and deallocating the memory:
use std::alloc::{dealloc, Layout};
use std::ptr;
let x = Box::new(String::from("Hello"));
let p = Box::into_raw(x);
unsafe {
ptr::drop_in_place(p);
dealloc(p as *mut u8, Layout::new::<String>());
}
Runconst: unstable · sourcepub fn into_raw_with_allocator(b: Self) -> (*mut T, A)
pub fn into_raw_with_allocator(b: Self) -> (*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.
Note: this is an associated function, which means that you have
to call it as Box::into_raw_with_allocator(b)
instead of b.into_raw_with_allocator()
. This
is so that there is no conflict with a method on the inner type.
Examples
Converting the raw pointer back into a Box
with Box::from_raw_in
for automatic cleanup:
#![feature(allocator_api)]
use std::alloc::System;
let x = Box::new_in(String::from("Hello"), System);
let (ptr, alloc) = Box::into_raw_with_allocator(x);
let x = unsafe { Box::from_raw_in(ptr, alloc) };
RunManual cleanup by explicitly running the destructor and deallocating the memory:
#![feature(allocator_api)]
use std::alloc::{Allocator, Layout, System};
use std::ptr::{self, NonNull};
let x = Box::new_in(String::from("Hello"), System);
let (ptr, alloc) = Box::into_raw_with_allocator(x);
unsafe {
ptr::drop_in_place(ptr);
let non_null = NonNull::new_unchecked(ptr);
alloc.deallocate(non_null.cast(), Layout::new::<String>());
}
Runconst: unstable · sourcepub fn allocator(b: &Self) -> &A
pub fn allocator(b: &Self) -> &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 (const: unstable) · sourcepub fn leak<'a>(b: Self) -> &'a mut T where
A: 'a,
pub fn leak<'a>(b: Self) -> &'a mut T where
A: 'a,
Consumes and leaks the Box
, returning a mutable reference,
&'a mut T
. Note that the type T
must outlive the chosen lifetime
'a
. If the type has only static references, or none at all, then this
may be chosen to be 'static
.
This function is mainly useful for data that lives for the remainder of
the program’s life. Dropping the returned reference will cause a memory
leak. If this is not acceptable, the reference should first be wrapped
with the Box::from_raw
function producing a Box
. This Box
can
then be dropped which will properly destroy T
and release the
allocated memory.
Note: this is an associated function, which means that you have
to call it as Box::leak(b)
instead of b.leak()
. This
is so that there is no conflict with a method on the inner type.
Examples
Simple usage:
let x = Box::new(41);
let static_ref: &'static mut usize = Box::leak(x);
*static_ref += 1;
assert_eq!(*static_ref, 42);
RunUnsized 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]);
Run1.63.0 (const: unstable) · sourcepub fn into_pin(boxed: Self) -> Pin<Self> where
A: 'static,
pub fn into_pin(boxed: Self) -> Pin<Self> where
A: 'static,
Converts a Box<T>
into a Pin<Box<T>>
. If T
does not implement Unpin
, then
*boxed
will be pinned in memory and unable to be moved.
This conversion does not allocate on the heap and happens in place.
This is also available via From
.
Constructing and pinning a Box
with Box::into_pin(Box::new(x))
can also be written more concisely using Box::pin(x)
.
This into_pin
method is useful if you already have a Box<T>
, or you are
constructing a (pinned) Box
in a different way than with Box::new
.
Notes
It’s not recommended that crates add an impl like From<Box<T>> for Pin<T>
,
as it’ll introduce an ambiguity when calling Pin::from
.
A demonstration of such a poor impl is shown below.
struct Foo; // A type defined in this crate.
impl From<Box<()>> for Pin<Foo> {
fn from(_: Box<()>) -> Pin<Foo> {
Pin::new(Foo)
}
}
let foo = Box::new(());
let bar = Pin::from(foo);
Runsourceimpl<A: Allocator> Box<dyn Any, A>
impl<A: Allocator> Box<dyn Any, A>
sourcepub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
Attempt to downcast the box to a concrete type.
Examples
use std::any::Any;
fn print_if_string(value: Box<dyn Any>) {
if let Ok(string) = value.downcast::<String>() {
println!("String ({}): {}", string.len(), string);
}
}
let my_string = "Hello World".to_string();
print_if_string(Box::new(my_string));
print_if_string(Box::new(0i8));
Runsourcepub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
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);
}
RunSafety
The contained value must be of type T
. Calling this method
with the incorrect type is undefined behavior.
sourceimpl<A: Allocator> Box<dyn Any + Send, A>
impl<A: Allocator> Box<dyn Any + Send, A>
sourcepub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
Attempt to downcast the box to a concrete type.
Examples
use std::any::Any;
fn print_if_string(value: Box<dyn Any + Send>) {
if let Ok(string) = value.downcast::<String>() {
println!("String ({}): {}", string.len(), string);
}
}
let my_string = "Hello World".to_string();
print_if_string(Box::new(my_string));
print_if_string(Box::new(0i8));
Runsourcepub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
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);
}
RunSafety
The contained value must be of type T
. Calling this method
with the incorrect type is undefined behavior.
sourceimpl<A: Allocator> Box<dyn Any + Send + Sync, A>
impl<A: Allocator> Box<dyn Any + Send + Sync, A>
1.51.0 · sourcepub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self>
Attempt to downcast the box to a concrete type.
Examples
use std::any::Any;
fn print_if_string(value: Box<dyn Any + Send + Sync>) {
if let Ok(string) = value.downcast::<String>() {
println!("String ({}): {}", string.len(), string);
}
}
let my_string = "Hello World".to_string();
print_if_string(Box::new(my_string));
print_if_string(Box::new(0i8));
Runsourcepub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
pub unsafe fn downcast_unchecked<T: Any>(self) -> Box<T, A>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
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);
}
RunSafety
The contained value must be of type T
. Calling this method
with the incorrect type is undefined behavior.
Trait Implementations
sourceimpl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S>
impl<S: ?Sized + AsyncIterator + Unpin> AsyncIterator for Box<S>
1.1.0 · sourceimpl<T: ?Sized, A: Allocator> BorrowMut<T> for Box<T, A>
impl<T: ?Sized, A: Allocator> BorrowMut<T> for Box<T, A>
sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T: Clone, A: Allocator + Clone> Clone for Box<T, A>
impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A>
sourcefn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
1.17.0 · sourceimpl Default for Box<CStr>
impl Default for Box<CStr>
sourcefn default() -> Box<CStr>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
fn default() -> Box<CStr>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Returns the “default value” for a type. Read more
sourceimpl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A>
impl<I: DoubleEndedIterator + ?Sized, A: Allocator> DoubleEndedIterator for Box<I, A>
sourcefn next_back(&mut self) -> Option<I::Item>
fn next_back(&mut self) -> Option<I::Item>
Removes and returns an element from the end of the iterator. Read more
sourcefn nth_back(&mut self, n: usize) -> Option<I::Item>
fn nth_back(&mut self, n: usize) -> Option<I::Item>
Returns the n
th element from the end of the iterator. Read more
sourcefn advance_back_by(&mut self, n: usize) -> Result<(), usize>
fn advance_back_by(&mut self, n: usize) -> Result<(), usize>
Advances the iterator from the back by n
elements. Read more
1.27.0 · sourcefn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R where
F: FnMut(B, Self::Item) -> R,
R: Try<Output = B>,
fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R where
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
sourceimpl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A>
impl<I: ExactSizeIterator + ?Sized, A: Allocator> ExactSizeIterator for Box<I, A>
1.45.0 · sourceimpl Extend<Box<str, Global>> for String
impl Extend<Box<str, Global>> for String
sourcefn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I)
fn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I)
Extends a collection with the contents of an iterator. Read more
sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
Reserves capacity in a collection for the given number of additional elements. Read more
1.17.0 · sourceimpl<T: Copy> From<&'_ [T]> for Box<[T]>
impl<T: Copy> From<&'_ [T]> for Box<[T]>
1.17.0 · sourceimpl From<&'_ CStr> for Box<CStr>
impl From<&'_ CStr> for Box<CStr>
sourcefn from(s: &CStr) -> Box<CStr>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
fn from(s: &CStr) -> Box<CStr>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Converts a &CStr
into a Box<CStr>
,
by copying the contents into a newly allocated Box
.
1.17.0 · sourceimpl From<&'_ str> for Box<str>
impl From<&'_ str> for Box<str>
1.45.0 · sourceimpl<T, const N: usize> From<[T; N]> for Box<[T]>
impl<T, const N: usize> From<[T; N]> for Box<[T]>
1.33.0 (const: unstable) · sourceimpl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>> where
A: 'static,
impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>> where
A: 'static,
const: unstable · sourcefn from(boxed: Box<T, A>) -> Self
fn from(boxed: Box<T, A>) -> Self
Converts a Box<T>
into a Pin<Box<T>>
. If T
does not implement Unpin
, then
*boxed
will be pinned in memory and unable to be moved.
This conversion does not allocate on the heap and happens in place.
This is also available via Box::into_pin
.
Constructing and pinning a Box
with <Pin<Box<T>>>::from(Box::new(x))
can also be written more concisely using Box::pin(x)
.
This From
implementation is useful if you already have a Box<T>
, or you are
constructing a (pinned) Box
in a different way than with Box::new
.
1.19.0 · sourceimpl<A: Allocator> From<Box<str, A>> for Box<[u8], A>
impl<A: Allocator> From<Box<str, A>> for Box<[u8], A>
sourcefn from(s: Box<str, A>) -> Self
fn from(s: Box<str, A>) -> Self
Converts a Box<str>
into a Box<[u8]>
This conversion does not allocate on the heap and happens in place.
Examples
// create a Box<str> which will be used to create a Box<[u8]>
let boxed: Box<str> = Box::from("hello");
let boxed_str: Box<[u8]> = Box::from(boxed);
// create a &[u8] which will be used to create a Box<[u8]>
let slice: &[u8] = &[104, 101, 108, 108, 111];
let boxed_slice = Box::from(slice);
assert_eq!(boxed_slice, boxed_str);
Run1.20.0 · sourceimpl From<CString> for Box<CStr>
impl From<CString> for Box<CStr>
1.45.0 · sourceimpl<T: Copy> From<Cow<'_, [T]>> for Box<[T]>
impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]>
sourcefn from(cow: Cow<'_, [T]>) -> Box<[T]>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
fn from(cow: Cow<'_, [T]>) -> Box<[T]>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
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 · sourceimpl From<Cow<'_, CStr>> for Box<CStr>
impl From<Cow<'_, CStr>> for Box<CStr>
sourcefn from(cow: Cow<'_, CStr>) -> Box<CStr>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
fn from(cow: Cow<'_, CStr>) -> Box<CStr>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
Converts a Cow<'a, CStr>
into a Box<CStr>
,
by copying the contents if they are borrowed.
1.45.0 · sourceimpl From<Cow<'_, str>> for Box<str>
impl From<Cow<'_, str>> for Box<str>
sourcefn from(cow: Cow<'_, str>) -> Box<str>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
fn from(cow: Cow<'_, str>) -> Box<str>ⓘNotable traits for Box<I, A>impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A> type Item = I::Item;impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static, type Output = F::Output;
A: 'static, type Output = F::Output;
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}");
Runlet unboxed = Cow::Owned("hello".to_string());
let boxed: Box<str> = Box::from(unboxed);
println!("{boxed}");
Run1.20.0 · sourceimpl From<String> for Box<str>
impl From<String> for Box<str>
1.32.0 · sourceimpl<I> FromIterator<I> for Box<[I]>
impl<I> FromIterator<I> for Box<[I]>
sourcefn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self
fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self
Creates a value from an iterator. Read more
1.36.0 · sourceimpl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static,
impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> where
A: 'static,
sourceimpl<G: ?Sized + Generator<R> + Unpin, R, A: Allocator> Generator<R> for Box<G, A> where
A: 'static,
impl<G: ?Sized + Generator<R> + Unpin, R, A: Allocator> Generator<R> for Box<G, A> where
A: 'static,
sourceimpl<G: ?Sized + Generator<R>, R, A: Allocator> Generator<R> for Pin<Box<G, A>> where
A: 'static,
impl<G: ?Sized + Generator<R>, R, A: Allocator> Generator<R> for Pin<Box<G, A>> where
A: 'static,
1.22.0 · sourceimpl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A>
impl<T: ?Sized + Hasher, A: Allocator> Hasher for Box<T, A>
sourcefn write_u128(&mut self, i: u128)
fn write_u128(&mut self, i: u128)
Writes a single u128
into this hasher.
sourcefn write_usize(&mut self, i: usize)
fn write_usize(&mut self, i: usize)
Writes a single usize
into this hasher.
sourcefn write_i128(&mut self, i: i128)
fn write_i128(&mut self, i: i128)
Writes a single i128
into this hasher.
sourcefn write_isize(&mut self, i: isize)
fn write_isize(&mut self, i: isize)
Writes a single isize
into this hasher.
sourcefn write_length_prefix(&mut self, len: usize)
fn write_length_prefix(&mut self, len: usize)
Writes a length prefix into this hasher, as part of being prefix-free. Read more
sourceimpl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A>
impl<I: Iterator + ?Sized, A: Allocator> Iterator for Box<I, A>
sourcefn next(&mut self) -> Option<I::Item>
fn next(&mut self) -> Option<I::Item>
Advances the iterator and returns the next value. Read more
sourcefn size_hint(&self) -> (usize, Option<usize>)
fn size_hint(&self) -> (usize, Option<usize>)
Returns the bounds on the remaining length of the iterator. Read more
sourcefn nth(&mut self, n: usize) -> Option<I::Item>
fn nth(&mut self, n: usize) -> Option<I::Item>
Returns the n
th element of the iterator. Read more
sourcefn count(self) -> usize
fn count(self) -> usize
Consumes the iterator, counting the number of iterations and returning it. Read more
sourcefn advance_by(&mut self, n: usize) -> Result<(), usize>
fn advance_by(&mut self, n: usize) -> Result<(), usize>
Advances the iterator by n
elements. Read more
1.28.0 · sourcefn step_by(self, step: usize) -> StepBy<Self>
fn step_by(self, step: usize) -> StepBy<Self>
Creates an iterator starting at the same point, but stepping by the given amount at each iteration. Read more
sourcefn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator<Item = Self::Item>,
fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator<Item = Self::Item>,
Takes two iterators and creates a new iterator over both in sequence. Read more
sourcefn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator,
fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator,
‘Zips up’ two iterators into a single iterator of pairs. Read more
sourcefn intersperse(self, separator: Self::Item) -> Intersperse<Self> where
Self::Item: Clone,
fn intersperse(self, separator: Self::Item) -> Intersperse<Self> where
Self::Item: Clone,
Creates a new iterator which places a copy of separator
between adjacent
items of the original iterator. Read more
sourcefn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> where
G: FnMut() -> Self::Item,
fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> where
G: FnMut() -> Self::Item,
Creates a new iterator which places an item generated by separator
between adjacent items of the original iterator. Read more
sourcefn map<B, F>(self, f: F) -> Map<Self, F> where
F: FnMut(Self::Item) -> B,
fn map<B, F>(self, f: F) -> Map<Self, F> where
F: FnMut(Self::Item) -> B,
Takes a closure and creates an iterator which calls that closure on each element. Read more
1.21.0 · sourcefn for_each<F>(self, f: F) where
F: FnMut(Self::Item),
fn for_each<F>(self, f: F) where
F: FnMut(Self::Item),
Calls a closure on each element of an iterator. Read more
sourcefn filter<P>(self, predicate: P) -> Filter<Self, P> where
P: FnMut(&Self::Item) -> bool,
fn filter<P>(self, predicate: P) -> Filter<Self, P> where
P: FnMut(&Self::Item) -> bool,
Creates an iterator which uses a closure to determine if an element should be yielded. Read more
sourcefn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
F: FnMut(Self::Item) -> Option<B>,
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
F: FnMut(Self::Item) -> Option<B>,
Creates an iterator that both filters and maps. Read more
sourcefn enumerate(self) -> Enumerate<Self>
fn enumerate(self) -> Enumerate<Self>
Creates an iterator which gives the current iteration count as well as the next value. Read more
sourcefn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,
sourcefn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,
Creates an iterator that yields elements based on a predicate. Read more
1.57.0 · sourcefn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> where
P: FnMut(Self::Item) -> Option<B>,
fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> where
P: FnMut(Self::Item) -> Option<B>,
Creates an iterator that both yields elements based on a predicate and maps. Read more
sourcefn skip(self, n: usize) -> Skip<Self>
fn skip(self, n: usize) -> Skip<Self>
Creates an iterator that skips the first n
elements. Read more
sourcefn take(self, n: usize) -> Take<Self>
fn take(self, n: usize) -> Take<Self>
Creates an iterator that yields the first n
elements, or fewer
if the underlying iterator ends sooner. Read more
sourcefn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
F: FnMut(&mut St, Self::Item) -> Option<B>,
fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
F: FnMut(&mut St, Self::Item) -> Option<B>,
sourcefn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
U: IntoIterator,
F: FnMut(Self::Item) -> U,
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
U: IntoIterator,
F: FnMut(Self::Item) -> U,
Creates an iterator that works like map, but flattens nested structure. Read more
1.29.0 · sourcefn flatten(self) -> Flatten<Self> where
Self::Item: IntoIterator,
fn flatten(self) -> Flatten<Self> where
Self::Item: IntoIterator,
Creates an iterator that flattens nested structure. Read more
sourcefn inspect<F>(self, f: F) -> Inspect<Self, F> where
F: FnMut(&Self::Item),
fn inspect<F>(self, f: F) -> Inspect<Self, F> where
F: FnMut(&Self::Item),
Does something with each element of an iterator, passing the value on. Read more
sourcefn collect<B>(self) -> B where
B: FromIterator<Self::Item>,
fn collect<B>(self) -> B where
B: FromIterator<Self::Item>,
Transforms an iterator into a collection. Read more
sourcefn try_collect<B>(
&mut self
) -> <<Self::Item as Try>::Residual as Residual<B>>::TryType where
B: FromIterator<<Self::Item as Try>::Output>,
Self::Item: Try,
<Self::Item as Try>::Residual: Residual<B>,
fn try_collect<B>(
&mut self
) -> <<Self::Item as Try>::Residual as Residual<B>>::TryType where
B: FromIterator<<Self::Item as Try>::Output>,
Self::Item: Try,
<Self::Item as Try>::Residual: Residual<B>,
Fallibly transforms an iterator into a collection, short circuiting if a failure is encountered. Read more
sourcefn collect_into<E>(self, collection: &mut E) -> &mut E where
E: Extend<Self::Item>,
fn collect_into<E>(self, collection: &mut E) -> &mut E where
E: Extend<Self::Item>,
Collects all the items from an iterator into a collection. Read more
sourcefn partition<B, F>(self, f: F) -> (B, B) where
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool,
fn partition<B, F>(self, f: F) -> (B, B) where
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool,
Consumes an iterator, creating two collections from it. Read more
sourcefn partition_in_place<'a, T, P>(self, predicate: P) -> usize where
T: 'a,
Self: DoubleEndedIterator<Item = &'a mut T>,
P: FnMut(&T) -> bool,
fn partition_in_place<'a, T, P>(self, predicate: P) -> usize where
T: 'a,
Self: DoubleEndedIterator<Item = &'a mut T>,
P: FnMut(&T) -> bool,
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
sourcefn is_partitioned<P>(self, predicate: P) -> bool where
P: FnMut(Self::Item) -> bool,
fn is_partitioned<P>(self, predicate: P) -> bool where
P: FnMut(Self::Item) -> bool,
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 · sourcefn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
F: FnMut(B, Self::Item) -> R,
R: Try<Output = B>,
fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
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 · sourcefn try_for_each<F, R>(&mut self, f: F) -> R where
F: FnMut(Self::Item) -> R,
R: Try<Output = ()>,
fn try_for_each<F, R>(&mut self, f: F) -> R where
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
sourcefn fold<B, F>(self, init: B, f: F) -> B where
F: FnMut(B, Self::Item) -> B,
fn fold<B, F>(self, init: B, f: F) -> B where
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 · sourcefn reduce<F>(self, f: F) -> Option<Self::Item> where
F: FnMut(Self::Item, Self::Item) -> Self::Item,
fn reduce<F>(self, f: F) -> Option<Self::Item> where
F: FnMut(Self::Item, Self::Item) -> Self::Item,
Reduces the elements to a single one, by repeatedly applying a reducing operation. Read more
sourcefn try_reduce<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType where
F: FnMut(Self::Item, Self::Item) -> R,
R: Try<Output = Self::Item>,
<R as Try>::Residual: Residual<Option<Self::Item>>,
fn try_reduce<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType where
F: FnMut(Self::Item, Self::Item) -> R,
R: Try<Output = Self::Item>,
<R as Try>::Residual: Residual<Option<Self::Item>>,
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
sourcefn all<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
fn all<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
Tests if every element of the iterator matches a predicate. Read more
sourcefn any<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
fn any<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
Tests if any element of the iterator matches a predicate. Read more
sourcefn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
P: FnMut(&Self::Item) -> bool,
fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
P: FnMut(&Self::Item) -> bool,
Searches for an element of an iterator that satisfies a predicate. Read more
1.30.0 · sourcefn find_map<B, F>(&mut self, f: F) -> Option<B> where
F: FnMut(Self::Item) -> Option<B>,
fn find_map<B, F>(&mut self, f: F) -> Option<B> where
F: FnMut(Self::Item) -> Option<B>,
Applies function to the elements of iterator and returns the first non-none result. Read more
sourcefn try_find<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType where
F: FnMut(&Self::Item) -> R,
R: Try<Output = bool>,
<R as Try>::Residual: Residual<Option<Self::Item>>,
fn try_find<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType where
F: FnMut(&Self::Item) -> R,
R: Try<Output = bool>,
<R as Try>::Residual: Residual<Option<Self::Item>>,
Applies function to the elements of iterator and returns the first true result or the first error. Read more
sourcefn position<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
fn position<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
Searches for an element in an iterator, returning its index. Read more
sourcefn rposition<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
Self: ExactSizeIterator + DoubleEndedIterator,
fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
Self: ExactSizeIterator + DoubleEndedIterator,
Searches for an element in an iterator from the right, returning its index. Read more
sourcefn max(self) -> Option<Self::Item> where
Self::Item: Ord,
fn max(self) -> Option<Self::Item> where
Self::Item: Ord,
Returns the maximum element of an iterator. Read more
sourcefn min(self) -> Option<Self::Item> where
Self::Item: Ord,
fn min(self) -> Option<Self::Item> where
Self::Item: Ord,
Returns the minimum element of an iterator. Read more
1.6.0 · sourcefn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,
fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,
Returns the element that gives the maximum value from the specified function. Read more
1.15.0 · sourcefn max_by<F>(self, compare: F) -> Option<Self::Item> where
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
fn max_by<F>(self, compare: F) -> Option<Self::Item> where
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 · sourcefn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,
fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,
Returns the element that gives the minimum value from the specified function. Read more
1.15.0 · sourcefn min_by<F>(self, compare: F) -> Option<Self::Item> where
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
fn min_by<F>(self, compare: F) -> Option<Self::Item> where
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
Returns the element that gives the minimum value with respect to the specified comparison function. Read more
sourcefn rev(self) -> Rev<Self> where
Self: DoubleEndedIterator,
fn rev(self) -> Rev<Self> where
Self: DoubleEndedIterator,
Reverses an iterator’s direction. Read more
sourcefn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Iterator<Item = (A, B)>,
fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Iterator<Item = (A, B)>,
Converts an iterator of pairs into a pair of containers. Read more
1.36.0 · sourcefn copied<'a, T>(self) -> Copied<Self> where
T: 'a + Copy,
Self: Iterator<Item = &'a T>,
fn copied<'a, T>(self) -> Copied<Self> where
T: 'a + Copy,
Self: Iterator<Item = &'a T>,
Creates an iterator which copies all of its elements. Read more
1.11.0 · sourcefn sum<S>(self) -> S where
S: Sum<Self::Item>,
fn sum<S>(self) -> S where
S: Sum<Self::Item>,
Sums the elements of an iterator. Read more
1.11.0 · sourcefn product<P>(self) -> P where
P: Product<Self::Item>,
fn product<P>(self) -> P where
P: Product<Self::Item>,
Iterates over the entire iterator, multiplying all the elements Read more
1.5.0 · sourcefn cmp<I>(self, other: I) -> Ordering where
I: IntoIterator<Item = Self::Item>,
Self::Item: Ord,
fn cmp<I>(self, other: I) -> Ordering where
I: IntoIterator<Item = Self::Item>,
Self::Item: Ord,
Lexicographically compares the elements of this Iterator
with those
of another. Read more
sourcefn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
Lexicographically compares the elements of this Iterator
with those
of another with respect to the specified comparison function. Read more
1.5.0 · sourcefn partial_cmp<I>(self, other: I) -> Option<Ordering> where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
Lexicographically compares the elements of this Iterator
with those
of another. Read more
sourcefn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering> where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering> where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
Lexicographically compares the elements of this Iterator
with those
of another with respect to the specified comparison function. Read more
1.5.0 · sourcefn eq<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
fn eq<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
sourcefn eq_by<I, F>(self, other: I, eq: F) -> bool where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
fn eq_by<I, F>(self, other: I, eq: F) -> bool where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
1.5.0 · sourcefn ne<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
fn ne<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
1.5.0 · sourcefn lt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn lt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
Determines if the elements of this Iterator
are lexicographically
less than those of another. Read more
1.5.0 · sourcefn le<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn le<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
Determines if the elements of this Iterator
are lexicographically
less or equal to those of another. Read more
1.5.0 · sourcefn gt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn gt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
Determines if the elements of this Iterator
are lexicographically
greater than those of another. Read more
1.5.0 · sourcefn ge<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn ge<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
Determines if the elements of this Iterator
are lexicographically
greater than or equal to those of another. Read more
sourcefn is_sorted(self) -> bool where
Self::Item: PartialOrd<Self::Item>,
fn is_sorted(self) -> bool where
Self::Item: PartialOrd<Self::Item>,
Checks if the elements of this iterator are sorted. Read more
sourcefn is_sorted_by<F>(self, compare: F) -> bool where
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
fn is_sorted_by<F>(self, compare: F) -> bool where
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
Checks if the elements of this iterator are sorted using the given comparator function. Read more
sourcefn is_sorted_by_key<F, K>(self, f: F) -> bool where
F: FnMut(Self::Item) -> K,
K: PartialOrd<K>,
fn is_sorted_by_key<F, K>(self, f: F) -> bool where
F: FnMut(Self::Item) -> K,
K: PartialOrd<K>,
Checks if the elements of this iterator are sorted using the given key extraction function. Read more
sourceimpl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A>
impl<T: ?Sized + Ord, A: Allocator> Ord for Box<T, A>
sourceimpl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd<Box<T, A>> for Box<T, A>
impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd<Box<T, A>> for Box<T, A>
sourcefn partial_cmp(&self, other: &Self) -> Option<Ordering>
fn partial_cmp(&self, other: &Self) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Self) -> bool
fn lt(&self, other: &Self) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Self) -> bool
fn le(&self, other: &Self) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
1.43.0 · sourceimpl<T, const N: usize> TryFrom<Box<[T], Global>> for Box<[T; N]>
impl<T, const N: usize> TryFrom<Box<[T], Global>> for Box<[T; N]>
impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A>
impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U, Global>> for Box<T, Global>
impl<T: ?Sized + Eq, A: Allocator> Eq for Box<T, A>
impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A>
impl<T: ?Sized, A: Allocator> Unpin for Box<T, A> where
A: 'static,
Auto Trait Implementations
impl<T: ?Sized, A> RefUnwindSafe for Box<T, A> where
A: RefUnwindSafe,
T: RefUnwindSafe,
impl<T: ?Sized, A> Send for Box<T, A> where
A: Send,
T: Send,
impl<T: ?Sized, A> Sync for Box<T, A> where
A: Sync,
T: Sync,
impl<T: ?Sized, A> UnwindSafe for Box<T, A> where
A: UnwindSafe,
T: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<F> IntoFuture for F where
F: Future,
impl<F> IntoFuture for F where
F: Future,
sourceimpl<I> IntoIterator for I where
I: Iterator,
impl<I> IntoIterator for I where
I: Iterator,
sourceimpl<'a, F> Pattern<'a> for F where
F: FnMut(char) -> bool,
impl<'a, F> Pattern<'a> for F where
F: FnMut(char) -> bool,
sourcefn into_searcher(self, haystack: &'a str) -> CharPredicateSearcher<'a, F>
fn into_searcher(self, haystack: &'a str) -> CharPredicateSearcher<'a, F>
Constructs the associated searcher from
self
and the haystack
to search in. Read more
sourcefn is_contained_in(self, haystack: &'a str) -> bool
fn is_contained_in(self, haystack: &'a str) -> bool
Checks whether the pattern matches anywhere in the haystack
sourcefn is_prefix_of(self, haystack: &'a str) -> bool
fn is_prefix_of(self, haystack: &'a str) -> bool
Checks whether the pattern matches at the front of the haystack
sourcefn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str>
fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str>
Removes the pattern from the front of haystack, if it matches.
sourcefn is_suffix_of(self, haystack: &'a str) -> bool where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
fn is_suffix_of(self, haystack: &'a str) -> bool where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
Checks whether the pattern matches at the back of the haystack
sourcefn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> where
CharPredicateSearcher<'a, F>: ReverseSearcher<'a>,
Removes the pattern from the back of haystack, if it matches.