Struct Watermark 

pub struct Watermark<I, H> { /* private fields */ }

Watermark wrapper.

Tracks live bytes in an AtomicUsize. Fires the handler on rising crossings of warn_pct and critical_pct, and on OOM. Falling edges (allocations released) do NOT reset the crossing flags — once a region reaches warn, it stays armed until manual reset (see rearm()).

Atomic variant only; non-atomic variant for single-core no_std targets will land later. Gated by cfg(target_has_atomic = "ptr").

Implementations

impl<I: Allocator, H: WatermarkHandler> Watermark<I, H>

pub fn new(inner: I, handler: H) -> Self

Wrap with default thresholds (75% / 90%).

pub fn with_thresholds( inner: I, handler: H, thresholds: WatermarkThresholds, ) -> Self

Wrap with explicit thresholds.

pub fn allocated_bytes(&self) -> usize

Bytes currently in use.

pub fn inner(&self) -> &I

Borrow the inner allocator.

pub fn handler(&self) -> &H

Borrow the handler.

pub fn rearm(&self)

Re-arm threshold firing (clears warn/critical fired flags). Call after addressing a high-water condition if you want the next crossing to fire again.

Trait Implementations

impl<I: Allocator, H: WatermarkHandler> Allocator for Watermark<I, H>

Available on target_has_atomic=ptr only.

fn allocate(&self, layout: NonZeroLayout) -> Result<NonNull<[u8]>, AllocError>

Allocate a block satisfying layout. The returned slice’s length is at least layout.size() but may be larger.

unsafe fn usable_size( &self, ptr: NonNull<u8>, layout: NonZeroLayout, ) -> Option<usize>

Usable size of an existing allocation, if the allocator can report it. Defaults to None — implementors that track usable size override.

fn capacity_bytes(&self) -> Option<usize>

Total bytes this allocator can issue, if bounded. None for unbounded allocators like System. Used by Watermark to compute thresholds.

fn corruption_events(&self) -> u64

Detected freelist / metadata corruption events observed by this allocator since construction.

fn allocate_zeroed( &self, layout: NonZeroLayout, ) -> Result<NonNull<[u8]>, AllocError>

Allocate a zero-initialized block.

unsafe fn grow( &self, ptr: NonNull<u8>, old: NonZeroLayout, new: NonZeroLayout, ) -> Result<NonNull<[u8]>, AllocError>

Grow an allocation in place if possible, otherwise allocate-copy-free.

unsafe fn shrink( &self, ptr: NonNull<u8>, old: NonZeroLayout, new: NonZeroLayout, ) -> Result<NonNull<[u8]>, AllocError>

Shrink an allocation in place if possible, otherwise allocate-copy-free.

fn reset(&mut self) -> Result<(), AllocError>

Reclaim everything previously allocated. Default impl returns AllocError — only arena-style allocators implement a meaningful reset.

impl<I: Allocator, H: WatermarkHandler> Deallocator for Watermark<I, H>

Available on target_has_atomic=ptr only.

unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: NonZeroLayout)

Release a previously allocated block.

impl<I: FixedRange, H: WatermarkHandler> FixedRange for Watermark<I, H>

Available on target_has_atomic=ptr only.

fn commit(&self, offset: usize, len: usize) -> Result<(), AllocError>

Pass-through forward so a commit-aware consumer reaches the inner backing when this wrapper sits over a lazy_commit MmapBacked.

fn base(&self) -> NonNull<u8>

First byte of the owned address range.

fn size(&self) -> usize

Length in bytes of the owned address range.

fn contains(&self, ptr: NonNull<u8>) -> bool

Whether ptr lies within [base, base + size).