Struct Arena 

pub struct Arena { /* private fields */ }

AST arena allocator.

Implementations

impl Arena

pub fn new() -> Arena

Creates a new AST arena.

pub fn bump(&self) -> &Bump

Returns a reference to the arena’s bump allocator.

pub fn bump_mut(&mut self) -> &mut Bump

Returns a mutable reference to the arena’s bump allocator.

pub fn allocated_bytes(&self) -> usize

Calculates the number of bytes currently allocated in the entire arena.

pub fn used_bytes(&self) -> usize

Returns the number of bytes currently in use.

Methods from Deref<Target = Bump>

pub fn min_align(&self) -> usize

Get this bump arena’s minimum alignment.

All objects allocated in this arena get aligned to this value.

Example

let bump2 = bumpalo::Bump::<2>::with_min_align();
assert_eq!(bump2.min_align(), 2);

let bump4 = bumpalo::Bump::<4>::with_min_align();
assert_eq!(bump4.min_align(), 4);

pub fn allocation_limit(&self) -> Option<usize>

The allocation limit for this arena in bytes.

Example

let bump = bumpalo::Bump::with_capacity(0);

assert_eq!(bump.allocation_limit(), None);

bump.set_allocation_limit(Some(6));

assert_eq!(bump.allocation_limit(), Some(6));

bump.set_allocation_limit(None);

assert_eq!(bump.allocation_limit(), None);

pub fn set_allocation_limit(&self, limit: Option<usize>)

Set the allocation limit in bytes for this arena.

The allocation limit is only enforced when allocating new backing chunks for a Bump. Updating the allocation limit will not affect existing allocations or any future allocations within the Bump’s current chunk.

Example

let bump = bumpalo::Bump::with_capacity(0);

bump.set_allocation_limit(Some(0));

assert!(bump.try_alloc(5).is_err());

pub fn alloc<T>(&self, val: T) -> &mut T

Allocate an object in this Bump and return an exclusive reference to it.

Panics

Panics if reserving space for T fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.alloc("hello");
assert_eq!(*x, "hello");

pub fn try_alloc<T>(&self, val: T) -> Result<&mut T, AllocErr>

Try to allocate an object in this Bump and return an exclusive reference to it.

Errors

Errors if reserving space for T fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.try_alloc("hello");
assert_eq!(x, Ok(&mut "hello"));

pub fn alloc_with<F, T>(&self, f: F) -> &mut T

where F: FnOnce() -> T,

Pre-allocate space for an object in this Bump, initializes it using the closure, then returns an exclusive reference to it.

See The _with Method Suffix for a discussion on the differences between the _with suffixed methods and those methods without it, their performance characteristics, and when you might or might not choose a _with suffixed method.

Panics

Panics if reserving space for T fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.alloc_with(|| "hello");
assert_eq!(*x, "hello");

pub fn try_alloc_with<F, T>(&self, f: F) -> Result<&mut T, AllocErr>

where F: FnOnce() -> T,

Tries to pre-allocate space for an object in this Bump, initializes it using the closure, then returns an exclusive reference to it.

See The _with Method Suffix for a discussion on the differences between the _with suffixed methods and those methods without it, their performance characteristics, and when you might or might not choose a _with suffixed method.

Errors

Errors if reserving space for T fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.try_alloc_with(|| "hello");
assert_eq!(x, Ok(&mut "hello"));

pub fn alloc_try_with<F, T, E>(&self, f: F) -> Result<&mut T, E>

where F: FnOnce() -> Result<T, E>,

Pre-allocates space for a Result in this Bump, initializes it using the closure, then returns an exclusive reference to its T if Ok.

Iff the allocation fails, the closure is not run.

Iff Err, an allocator rewind is attempted and the E instance is moved out of the allocator to be consumed or dropped as normal.

See The _with Method Suffix for a discussion on the differences between the _with suffixed methods and those methods without it, their performance characteristics, and when you might or might not choose a _with suffixed method.

For caveats specific to fallible initialization, see The _try_with Method Suffix.

Errors

Iff the allocation succeeds but f fails, that error is forwarded by value.

Panics

Panics if reserving space for Result<T, E> fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.alloc_try_with(|| Ok("hello"))?;
assert_eq!(*x, "hello");

pub fn try_alloc_try_with<F, T, E>( &self, f: F, ) -> Result<&mut T, AllocOrInitError<E>>

where F: FnOnce() -> Result<T, E>,

Tries to pre-allocates space for a Result in this Bump, initializes it using the closure, then returns an exclusive reference to its T if all Ok.

Iff the allocation fails, the closure is not run.

Iff the closure returns Err, an allocator rewind is attempted and the E instance is moved out of the allocator to be consumed or dropped as normal.

See The _with Method Suffix for a discussion on the differences between the _with suffixed methods and those methods without it, their performance characteristics, and when you might or might not choose a _with suffixed method.

For caveats specific to fallible initialization, see The _try_with Method Suffix.

Errors

Errors with the Alloc variant iff reserving space for Result<T, E> fails.

Iff the allocation succeeds but f fails, that error is forwarded by value inside the Init variant.

Example

let bump = bumpalo::Bump::new();
let x = bump.try_alloc_try_with(|| Ok("hello"))?;
assert_eq!(*x, "hello");

pub fn alloc_slice_copy<T>(&self, src: &[T]) -> &mut [T]

where T: Copy,

Copy a slice into this Bump and return an exclusive reference to the copy.

Panics

Panics if reserving space for the slice fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.alloc_slice_copy(&[1, 2, 3]);
assert_eq!(x, &[1, 2, 3]);

pub fn try_alloc_slice_copy<T>(&self, src: &[T]) -> Result<&mut [T], AllocErr>

where T: Copy,

Like alloc_slice_copy, but does not panic in case of allocation failure.

Example

let bump = bumpalo::Bump::new();
let x = bump.try_alloc_slice_copy(&[1, 2, 3]);
assert_eq!(x, Ok(&mut[1, 2, 3] as &mut [_]));


let bump = bumpalo::Bump::new();
bump.set_allocation_limit(Some(4));
let x = bump.try_alloc_slice_copy(&[1, 2, 3, 4, 5, 6]);
assert_eq!(x, Err(bumpalo::AllocErr)); // too big

pub fn alloc_slice_clone<T>(&self, src: &[T]) -> &mut [T]

where T: Clone,

Clone a slice into this Bump and return an exclusive reference to the clone. Prefer alloc_slice_copy if T is Copy.

Panics

Panics if reserving space for the slice fails.

Example

#[derive(Clone, Debug, Eq, PartialEq)]
struct Sheep {
    name: String,
}

let originals = [
    Sheep { name: "Alice".into() },
    Sheep { name: "Bob".into() },
    Sheep { name: "Cathy".into() },
];

let bump = bumpalo::Bump::new();
let clones = bump.alloc_slice_clone(&originals);
assert_eq!(originals, clones);

pub fn try_alloc_slice_clone<T>(&self, src: &[T]) -> Result<&mut [T], AllocErr>

where T: Clone,

Like alloc_slice_clone but does not panic on failure.

pub fn alloc_str(&self, src: &str) -> &mut str

Copy a string slice into this Bump and return an exclusive reference to it.

Panics

Panics if reserving space for the string fails.

Example

let bump = bumpalo::Bump::new();
let hello = bump.alloc_str("hello world");
assert_eq!("hello world", hello);

pub fn try_alloc_str(&self, src: &str) -> Result<&mut str, AllocErr>

Same as alloc_str but does not panic on failure.

Example

let bump = bumpalo::Bump::new();
let hello = bump.try_alloc_str("hello world").unwrap();
assert_eq!("hello world", hello);


let bump = bumpalo::Bump::new();
bump.set_allocation_limit(Some(5));
let hello = bump.try_alloc_str("hello world");
assert_eq!(Err(bumpalo::AllocErr), hello);

pub fn alloc_slice_fill_with<T, F>(&self, len: usize, f: F) -> &mut [T]

where F: FnMut(usize) -> T,

Allocates a new slice of size len into this Bump and returns an exclusive reference to the copy.

The elements of the slice are initialized using the supplied closure. The closure argument is the position in the slice.

Panics

Panics if reserving space for the slice fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.alloc_slice_fill_with(5, |i| 5 * (i + 1));
assert_eq!(x, &[5, 10, 15, 20, 25]);

pub fn alloc_slice_try_fill_with<T, F, E>( &self, len: usize, f: F, ) -> Result<&mut [T], E>

where F: FnMut(usize) -> Result<T, E>,

Allocates a new slice of size len into this Bump and returns an exclusive reference to the copy, failing if the closure return an Err.

The elements of the slice are initialized using the supplied closure. The closure argument is the position in the slice.

Panics

Panics if reserving space for the slice fails.

Example

let bump = bumpalo::Bump::new();
let x: Result<&mut [usize], ()> = bump.alloc_slice_try_fill_with(5, |i| Ok(5 * i));
assert_eq!(x, Ok(bump.alloc_slice_copy(&[0, 5, 10, 15, 20])));

let bump = bumpalo::Bump::new();
let x: Result<&mut [usize], ()> = bump.alloc_slice_try_fill_with(
   5,
   |n| if n == 2 { Err(()) } else { Ok(n) }
);
assert_eq!(x, Err(()));

pub fn try_alloc_slice_fill_with<T, F>( &self, len: usize, f: F, ) -> Result<&mut [T], AllocErr>

where F: FnMut(usize) -> T,

Allocates a new slice of size len into this Bump and returns an exclusive reference to the copy.

The elements of the slice are initialized using the supplied closure. The closure argument is the position in the slice.

Example

let bump = bumpalo::Bump::new();
let x = bump.try_alloc_slice_fill_with(5, |i| 5 * (i + 1));
assert_eq!(x, Ok(&mut[5usize, 10, 15, 20, 25] as &mut [_]));


let bump = bumpalo::Bump::new();
bump.set_allocation_limit(Some(4));
let x = bump.try_alloc_slice_fill_with(10, |i| 5 * (i + 1));
assert_eq!(x, Err(bumpalo::AllocErr));

pub fn alloc_slice_fill_copy<T>(&self, len: usize, value: T) -> &mut [T]

where T: Copy,

Allocates a new slice of size len into this Bump and returns an exclusive reference to the copy.

All elements of the slice are initialized to value.

Panics

Panics if reserving space for the slice fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.alloc_slice_fill_copy(5, 42);
assert_eq!(x, &[42, 42, 42, 42, 42]);

pub fn try_alloc_slice_fill_copy<T>( &self, len: usize, value: T, ) -> Result<&mut [T], AllocErr>

where T: Copy,

Same as alloc_slice_fill_copy but does not panic on failure.

pub fn alloc_slice_fill_clone<T>(&self, len: usize, value: &T) -> &mut [T]

where T: Clone,

Allocates a new slice of size len slice into this Bump and return an exclusive reference to the copy.

All elements of the slice are initialized to value.clone().

Panics

Panics if reserving space for the slice fails.

Example

let bump = bumpalo::Bump::new();
let s: String = "Hello Bump!".to_string();
let x: &[String] = bump.alloc_slice_fill_clone(2, &s);
assert_eq!(x.len(), 2);
assert_eq!(&x[0], &s);
assert_eq!(&x[1], &s);

pub fn try_alloc_slice_fill_clone<T>( &self, len: usize, value: &T, ) -> Result<&mut [T], AllocErr>

where T: Clone,

Like alloc_slice_fill_clone but does not panic on failure.

pub fn alloc_slice_fill_iter<T, I>(&self, iter: I) -> &mut [T]

where I: IntoIterator<Item = T>, <I as IntoIterator>::IntoIter: ExactSizeIterator,

Allocates a new slice of size len slice into this Bump and return an exclusive reference to the copy.

The elements are initialized using the supplied iterator.

Panics

Panics if reserving space for the slice fails, or if the supplied iterator returns fewer elements than it promised.

Example

let bump = bumpalo::Bump::new();
let x: &[i32] = bump.alloc_slice_fill_iter([2, 3, 5].iter().cloned().map(|i| i * i));
assert_eq!(x, [4, 9, 25]);

pub fn alloc_slice_try_fill_iter<T, I, E>(&self, iter: I) -> Result<&mut [T], E>

where I: IntoIterator<Item = Result<T, E>>, <I as IntoIterator>::IntoIter: ExactSizeIterator,

Allocates a new slice of size len slice into this Bump and return an exclusive reference to the copy, failing if the iterator returns an Err.

The elements are initialized using the supplied iterator.

Panics

Panics if reserving space for the slice fails, or if the supplied iterator returns fewer elements than it promised.

Examples

let bump = bumpalo::Bump::new();
let x: Result<&mut [i32], ()> = bump.alloc_slice_try_fill_iter(
   [2, 3, 5].iter().cloned().map(|i| Ok(i * i))
);
assert_eq!(x, Ok(bump.alloc_slice_copy(&[4, 9, 25])));

let bump = bumpalo::Bump::new();
let x: Result<&mut [i32], ()> = bump.alloc_slice_try_fill_iter(
   [Ok(2), Err(()), Ok(5)].iter().cloned()
);
assert_eq!(x, Err(()));

pub fn try_alloc_slice_fill_iter<T, I>( &self, iter: I, ) -> Result<&mut [T], AllocErr>

where I: IntoIterator<Item = T>, <I as IntoIterator>::IntoIter: ExactSizeIterator,

Allocates a new slice of size iter.len() slice into this Bump and return an exclusive reference to the copy. Does not panic on failure.

The elements are initialized using the supplied iterator.

Example

let bump = bumpalo::Bump::new();
let x: &[i32] = bump.try_alloc_slice_fill_iter([2, 3, 5]
    .iter().cloned().map(|i| i * i)).unwrap();
assert_eq!(x, [4, 9, 25]);

pub fn alloc_slice_fill_default<T>(&self, len: usize) -> &mut [T]

where T: Default,

Allocates a new slice of size len slice into this Bump and return an exclusive reference to the copy.

All elements of the slice are initialized to T::default().

Panics

Panics if reserving space for the slice fails.

Example

let bump = bumpalo::Bump::new();
let x = bump.alloc_slice_fill_default::<u32>(5);
assert_eq!(x, &[0, 0, 0, 0, 0]);

pub fn try_alloc_slice_fill_default<T>( &self, len: usize, ) -> Result<&mut [T], AllocErr>

where T: Default,

Like alloc_slice_fill_default but does not panic on failure.

pub fn alloc_layout(&self, layout: Layout) -> NonNull<u8>

Allocate space for an object with the given Layout.

The returned pointer points at uninitialized memory, and should be initialized with std::ptr::write.

Panics

Panics if reserving space matching layout fails.

pub fn try_alloc_layout(&self, layout: Layout) -> Result<NonNull<u8>, AllocErr>

Attempts to allocate space for an object with the given Layout or else returns an Err.

The returned pointer points at uninitialized memory, and should be initialized with std::ptr::write.

Errors

Errors if reserving space matching layout fails.

pub fn chunk_capacity(&self) -> usize

Gets the remaining capacity in the current chunk (in bytes).

Example

use bumpalo::Bump;

let bump = Bump::with_capacity(100);

let capacity = bump.chunk_capacity();
assert!(capacity >= 100);

pub unsafe fn iter_allocated_chunks_raw(&self) -> ChunkRawIter<'_, MIN_ALIGN>

Returns an iterator over raw pointers to chunks of allocated memory that this arena has bump allocated into.

This is an unsafe version of iter_allocated_chunks(), with the caller responsible for safe usage of the returned pointers as well as ensuring that the iterator is not invalidated by new allocations.

Safety

Allocations from this arena must not be performed while the returned iterator is alive. If reading the chunk data (or casting to a reference) the caller must ensure that there exist no mutable references to previously allocated data.

In addition, all of the caveats when reading the chunk data from iter_allocated_chunks() still apply.

pub fn allocated_bytes(&self) -> usize

Calculates the number of bytes currently allocated across all chunks in this bump arena.

If you allocate types of different alignments or types with larger-than-typical alignment in the same arena, some padding bytes might get allocated in the bump arena. Note that those padding bytes will add to this method’s resulting sum, so you cannot rely on it only counting the sum of the sizes of the things you’ve allocated in the arena.

The allocated bytes do not include the size of bumpalo’s metadata, so the amount of memory requested from the Rust allocator is higher than the returned value.

Example

let bump = bumpalo::Bump::new();
let _x = bump.alloc_slice_fill_default::<u32>(5);
let bytes = bump.allocated_bytes();
assert!(bytes >= core::mem::size_of::<u32>() * 5);

pub fn allocated_bytes_including_metadata(&self) -> usize

Calculates the number of bytes requested from the Rust allocator for this Bump.

This number is equal to the allocated_bytes() plus the size of the bump metadata.

Trait Implementations

impl Default for Arena

fn default() -> Arena

Returns the “default value” for a type.

impl Deref for Arena

type Target = Bump

The resulting type after dereferencing.

fn deref(&self) -> &<Arena as Deref>::Target

Dereferences the value.