Struct Arena 

pub struct Arena { /* private fields */ }

A bump allocator over one fixed reservation, reset as a whole.

Implementations

impl Arena

pub fn with_capacity(bytes: usize) -> Arena

Reserve bytes up front. The buffer is taken from the global allocator once and held until the arena drops; nothing here allocates again.

pub fn tagged(bytes: usize, tag: MemTag) -> Arena

As with_capacity, reporting the reservation under tag in host memory for as long as the arena lives. An arena’s whole cost is its reservation, so it can account for itself rather than making its owner do it.

pub fn capacity(&self) -> usize

The reservation size in bytes.

pub fn used(&self) -> usize

Bytes handed out since the last reset.

pub fn remaining(&self) -> usize

Bytes still available before the next request is declined.

pub fn peak(&self) -> usize

The most this arena has held between resets: what to size it from.

pub fn overflows(&self) -> u32

Requests declined since the last clear_overflows. Non-zero means callers fell back to the heap and the reserve wants raising.

pub fn clear_overflows(&self)

Reset the overflow counter.

pub fn reset(&mut self)

Give back everything handed out. Taking &mut self is the safety argument: no allocation from this arena can still be borrowed.

Deliberately leaves peak and overflows alone: both describe the worst frame so far, which is what sizes the reserve, and a per-frame reset would erase exactly the evidence they exist to carry.

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

where T: Copy,

Move value into the arena. None when the arena is full, which is the caller’s cue to fall back to the heap rather than a failure.

pub fn vec<T>(&self, capacity: usize) -> Option<ArenaVec<'_, T>>

where T: Copy,

An empty vector holding capacity elements’ worth of arena. Pushing past that capacity does not grow – the caller reserves the bound it knows.

Trait Implementations

impl Drop for Arena

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

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

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl Send for Arena