Struct Arena 

pub struct Arena { /* private fields */ }

A simple bump allocator for temporary allocations.

The arena pre-allocates a contiguous block of memory and hands out slices from it via bump pointer allocation. When the frame is complete, the arena is reset (O(1)) and the memory is reused.

Implementations

impl Arena

pub fn new(capacity: usize) -> Self

Create a new arena with the specified capacity.

pub fn with_default_size() -> Self

Create a new arena with the default size (64KB).

pub fn reset(&self)

Reset the arena for reuse.

This is an O(1) operation - it just resets the bump pointer. The memory contents are not cleared.

pub fn alloc_slice(&self, len: usize) -> Option<&mut [u8]>

Allocate a mutable slice of bytes.

Returns None if there’s not enough space in the arena. SAFETY: This returns a mutable reference from a shared reference, which is safe because we use interior mutability (Cell) to track the allocation position, ensuring each region is only handed out once.

pub fn alloc_slice_zeroed(&self, len: usize) -> Option<&mut [u8]>

Allocate a mutable slice of bytes, zeroed.

Returns None if there’s not enough space in the arena.

pub fn alloc_vec(&self, initial_capacity: usize) -> Option<ArenaVec<'_>>

Allocate a Vec-like buffer backed by the arena.

Returns an ArenaVec that can grow up to the remaining capacity.

pub fn usage(&self) -> usize

Get the current usage of the arena.

pub fn capacity(&self) -> usize

Get the total capacity of the arena.

pub fn remaining(&self) -> usize

Get the remaining capacity.

pub fn peak_usage(&self) -> usize

Get the peak usage (highest watermark since creation).

Trait Implementations

impl Debug for Arena

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

Formats the value using the given formatter.