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 new Pin<Box<T>>. If T does not implement Unpin, then x will be pinned in memory and unable to be moved.

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

Performs the conversion.

Performs the conversion.

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Formats the value using the given formatter. Read more

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

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

The resulting type after dereferencing.

Dereferences the value.

Mutably dereferences the value.

Formats the value using the given formatter. Read more

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

Returns the nth 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

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

Executes the destructor for this type. Read more

Returns the exact length of the iterator. Read more

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

Returns true if the iterator is empty. Read more

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

This impl replaces unsize coercion.

Performs the conversion.

Converts a Box<T> into a Pin<Box<T>>

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

Performs the conversion.

The type of value produced on completion.

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

Feeds this value into the given Hasher. Read more

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

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

Writes some data into this Hasher. Read more

Writes a single u8 into this hasher.

Writes a single u16 into this hasher.

Writes a single u32 into this hasher.

Writes a single u64 into this hasher.

Writes a single u128 into this hasher.

Writes a single usize into this hasher.

Writes a single i8 into this hasher.

Writes a single i16 into this hasher.

Writes a single i32 into this hasher.

Writes a single i64 into this hasher.

Writes a single i128 into this hasher.

Writes a single isize into this hasher.

The type of the elements being iterated over.

Advances the iterator and returns the next value. Read more

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

Returns the nth element of the iterator. Read more

Consumes the iterator, returning the last element. 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

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

‘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

🔬 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 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

Creates an iterator that skips elements based on a predicate. 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

An iterator adapter similar to fold that holds internal state and produces a new iterator. Read more

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

Creates an iterator that flattens nested structure. Read more

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

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

Borrows an iterator, rather than consuming it. Read more

Transforms an iterator into a collection. Read more

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

🔬 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

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

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

Repeats an iterator endlessly. 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

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

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

Lexicographically compares the elements of this Iterator with those of another. Read more

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

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

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

🔬 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

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

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

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

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

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

🔬 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. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

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

This method tests for !=.

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

Formats the value using the given formatter.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

This impl replaces unsize coercion.

The type returned in the event of a conversion error.

Performs the conversion.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

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

The output that the future will produce on completion.

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

Which kind of future are we turning this into?

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

Creates a future from a value.

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

Converts the given value to a String. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.