Struct bumpalo::boxed::Box [−][src]
#[repr(transparent)]pub struct Box<'a, T: ?Sized>(_);
Expand description
An owned pointer to a bump-allocated T
value, that runs Drop
implementations.
See the module-level documentation for more details.
Implementations
Allocates memory on the heap and then places x
into it.
This doesn’t actually allocate if T
is zero-sized.
Examples
use bumpalo::{Bump, boxed::Box};
let b = Bump::new();
let five = Box::new_in(5, &b);
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.
Examples
Recreate a Box
which was previously converted to a raw pointer
using Box::into_raw
:
use bumpalo::{Bump, boxed::Box};
let b = Bump::new();
let x = Box::new_in(5, &b);
let ptr = Box::into_raw(x);
let x = unsafe { Box::from_raw(ptr) }; // Note that new `x`'s lifetime is unbound. It must be bound to the `b` immutable borrow before `b` is reset.
Manually create a Box
from scratch by using the bump allocator:
use std::alloc::{alloc, Layout};
use bumpalo::{Bump, boxed::Box};
let b = Bump::new();
unsafe {
let ptr = b.alloc_layout(Layout::new::<i32>()).as_ptr() as *mut i32;
*ptr = 5;
let x = Box::from_raw(ptr); // Note that `x`'s lifetime is unbound. It must be bound to the `b` immutable borrow before `b` is reset.
}
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
value previously managed by the Box
. In particular, the
caller should properly destroy T
. 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:
use bumpalo::{Bump, boxed::Box};
let b = Bump::new();
let x = Box::new_in(String::from("Hello"), &b);
let ptr = Box::into_raw(x);
let x = unsafe { Box::from_raw(ptr) }; // Note that new `x`'s lifetime is unbound. It must be bound to the `b` immutable borrow before `b` is reset.
Manual cleanup by explicitly running the destructor:
use std::ptr;
use bumpalo::{Bump, boxed::Box};
let b = Bump::new();
let mut x = Box::new_in(String::from("Hello"), &b);
let p = Box::into_raw(x);
unsafe {
ptr::drop_in_place(p);
}
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:
use bumpalo::{Bump, boxed::Box};
let b = Bump::new();
let x = Box::new_in(41, &b);
let reference: &mut usize = Box::leak(x);
*reference += 1;
assert_eq!(*reference, 42);
use bumpalo::{Bump, boxed::Box, vec};
let b = Bump::new();
let x = vec![in &b; 1, 2, 3].into_boxed_slice();
let reference = Box::leak(x);
reference[0] = 4;
assert_eq!(*reference, [4, 2, 3]);
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));
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));
Creates a value from an iterator.
This method is adapted version of FromIterator::from_iter
.
It cannot be made as that trait implementation given different signature.
Examples
Basic usage:
use bumpalo::{Bump, boxed::Box, vec};
let b = Bump::new();
let five_fives = std::iter::repeat(5).take(5);
let slice = Box::from_iter_in(five_fives, &b);
assert_eq!(vec![in &b; 5, 5, 5, 5, 5], &*slice);
Trait Implementations
Mutably borrows from an owned value. Read more
Removes and returns an element from the end of the iterator. Read more
Returns the n
th element from the end of the iterator. Read more
🔬 This is a nightly-only experimental API. (iter_advance_by
)
recently added
Advances the iterator from the back by n
elements. Read more
This is the reverse version of Iterator::try_fold()
: it takes
elements starting from the back of the iterator. Read more
An iterator method that reduces the iterator’s elements to a single, final value, starting from the back. Read more
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
Writes a single u128
into this hasher.
Writes a single usize
into this hasher.
Writes a single i128
into this hasher.
Writes a single isize
into this hasher.
Advances the iterator and returns the next value. Read more
Returns the bounds on the remaining length of the iterator. Read more
Returns the n
th element of the iterator. Read more
Consumes the iterator, counting the number of iterations and returning it. Read more
🔬 This is a nightly-only experimental API. (iter_advance_by
)
recently added
Advances the iterator by n
elements. Read more
Creates an iterator starting at the same point, but stepping by the given amount at each iteration. Read more
1.0.0[src]fn 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
1.0.0[src]fn 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
🔬 This is a nightly-only experimental API. (iter_intersperse
)
recently added
Creates a new iterator which places a copy of separator
between adjacent
items of the original iterator. Read more
fn 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,
🔬 This is a nightly-only experimental API. (iter_intersperse
)
recently added
Creates a new iterator which places an item generated by separator
between adjacent items of the original iterator. Read more
Takes a closure and creates an iterator which calls that closure on each element. Read more
Calls a closure on each element of an iterator. Read more
Creates an iterator which uses a closure to determine if an element should be yielded. Read more
Creates an iterator that both filters and maps. Read more
Creates an iterator which gives the current iteration count as well as the next value. Read more
Creates an iterator that yields elements based on a predicate. Read more
Creates an iterator that both yields elements based on a predicate and maps. Read more
Creates an iterator that skips the first n
elements. Read more
Creates an iterator that yields the first n
elements, or fewer
if the underlying iterator ends sooner. Read more
Creates an iterator that works like map, but flattens nested structure. Read more
Creates an iterator that flattens nested structure. Read more
Does something with each element of an iterator, passing the value on. Read more
Transforms an iterator into a collection. Read more
Consumes an iterator, creating two collections from it. Read more
fn 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,
🔬 This is a nightly-only experimental API. (iter_partition_in_place
)
new API
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
🔬 This is a nightly-only experimental API. (iter_is_partitioned
)
new API
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
An iterator method that applies a function as long as it returns successfully, producing a single, final value. Read more
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
Folds every element into an accumulator by applying an operation, returning the final result. Read more
Reduces the elements to a single one, by repeatedly applying a reducing operation. Read more
Tests if every element of the iterator matches a predicate. Read more
Tests if any element of the iterator matches a predicate. Read more
Searches for an element of an iterator that satisfies a predicate. Read more
Applies function to the elements of iterator and returns the first non-none result. Read more
🔬 This is a nightly-only experimental API. (try_find
)
new API
Applies function to the elements of iterator and returns the first true result or the first error. Read more
Searches for an element in an iterator, returning its index. Read more
1.0.0[src]fn 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
Returns the maximum element of an iterator. Read more
Returns the minimum element of an iterator. Read more
Returns the element that gives the maximum value from the specified function. Read more
Returns the element that gives the maximum value with respect to the specified comparison function. Read more
Returns the element that gives the minimum value from the specified function. Read more
Returns the element that gives the minimum value with respect to the specified comparison function. Read more
Reverses an iterator’s direction. Read more
Converts an iterator of pairs into a pair of containers. Read more
Creates an iterator which copies all of its elements. Read more
Sums the elements of an iterator. Read more
Iterates over the entire iterator, multiplying all the elements Read more
Lexicographically compares the elements of this Iterator
with those
of another. Read more
fn 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,
iter_order_by
)Lexicographically compares the elements of this Iterator
with those
of another with respect to the specified comparison function. Read more
1.5.0[src]fn 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
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>,
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>,
iter_order_by
)Lexicographically compares the elements of this Iterator
with those
of another with respect to the specified comparison function. Read more
1.5.0[src]fn 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>,
fn 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,
iter_order_by
)1.5.0[src]fn 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[src]fn 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[src]fn 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[src]fn 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[src]fn 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
🔬 This is a nightly-only experimental API. (is_sorted
)
new API
Checks if the elements of this iterator are sorted. Read more
🔬 This is a nightly-only experimental API. (is_sorted
)
new API
Checks if the elements of this iterator are sorted using the given comparator function. Read more
fn is_sorted_by_key<F, K>(self, f: F) -> bool where
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>,
🔬 This is a nightly-only experimental API. (is_sorted
)
new API
Checks if the elements of this iterator are sorted using the given key extraction function. Read more
This method returns an ordering between self
and other
values if one exists. Read more
This method tests less than (for self
and other
) and is used by the <
operator. Read more
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
This impl replaces unsize coercion.
Auto Trait Implementations
impl<'a, T: ?Sized> RefUnwindSafe for Box<'a, T> where
T: RefUnwindSafe,
impl<'a, T> !UnwindSafe for Box<'a, T>
Blanket Implementations
Mutably borrows from an owned value. Read more
into_future
)The output that the future will produce on completion.
type Future = F
type Future = F
into_future
)Which kind of future are we turning this into?
into_future
)Creates a future from a value.