Struct VersionedCounts 

pub struct VersionedCounts { /* private fields */ }

A reusable counter keyed by usize with O(1) “clear” between sessions.

Storage is positional — bucket[idx] holds the count for source index idx. Each session bumps a version stamp; slots are considered live only when their stamp matches the current version, so a session “clear” is a single increment instead of a vec-wide write.

Designed for hot paths that previously allocated a fresh HashMap<usize, u32> per call. After the first begin(capacity) warms the buffer, subsequent sessions allocate nothing.

Implementations

impl VersionedCounts

pub fn new() -> Self

pub fn with_capacity(capacity: usize) -> Self

pub fn unique_count(&self) -> usize

pub fn begin(&mut self, capacity: usize)

Start a new session. Resizes if needed and bumps the version so all previously-touched slots read as stale on the first bump.

pub fn bump(&mut self, idx: usize) -> u32

Increment the count at idx, returning the new count for this session. Stale slots are reset to 1 before counting.

pub fn get(&self, idx: usize) -> u32

Read the count at idx for the current session. Returns 0 if the slot is out of bounds or stale.

pub fn iter_live(&self) -> impl Iterator<Item = (usize, u32)> + '_

Live (idx, count) pairs in ascending idx order.

pub fn iter_live_rev(&self) -> impl Iterator<Item = (usize, u32)> + '_

Live (idx, count) pairs in descending idx order — convenient for callers that need to mutate an indexed collection without invalidating not-yet-processed indices (e.g. Vec::swap_remove).

pub fn iter_pair_live_rev<'a>( &'a self, other: &'a Self, ) -> impl Iterator<Item = (usize, u32, u32)> + 'a

Walk both buffers in parallel in descending idx order, yielding (idx, count_self, count_other) for any idx where at least one side is live this session. Slots stale or out-of-bounds on either side contribute 0 for that side. Stops at max(self.len, other.len).

Trait Implementations

impl Clone for VersionedCounts

fn clone(&self) -> VersionedCounts

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for VersionedCounts

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

Formats the value using the given formatter.

impl Default for VersionedCounts

fn default() -> Self

Returns the “default value” for a type.