Struct TinyLfuWidthCache 

pub struct TinyLfuWidthCache { /* private fields */ }

Width cache using W-TinyLFU admission policy.

Architecture:

• Window cache (small LRU, ~1% of capacity): captures recent items.
• Main cache (larger LRU, ~99% of capacity): for frequently accessed items.
• Count-Min Sketch + Doorkeeper: frequency estimation for admission decisions.
• Fingerprint guard: secondary hash per entry to detect hash collisions.

On every access:

1. Check main cache → hit? Return value (verify fingerprint).
2. Check window cache → hit? Return value (verify fingerprint).
3. Miss: compute width, insert into window cache.

On window cache eviction:

1. The evicted item becomes a candidate.
2. The LRU victim of the main cache is identified.
3. If freq(candidate) > freq(victim), candidate enters main cache (victim is evicted). Otherwise, candidate is discarded.

Frequency tracking uses Doorkeeper → CMS pipeline:

• First access: doorkeeper records.
• Second+ access: CMS is incremented.

Implementations

impl TinyLfuWidthCache

pub fn new(total_capacity: usize) -> Self

Create a new TinyLFU cache with the given total capacity.

The window gets ~1% of capacity (minimum 1), main gets the rest.

pub fn get_or_compute(&mut self, text: &str) -> usize

Get cached width or compute and cache it.

pub fn get_or_compute_with<F>(&mut self, text: &str, compute: F) -> usize

where F: FnOnce(&str) -> usize,

Get cached width or compute using a custom function.

pub fn contains(&self, text: &str) -> bool

Check if a key is in the cache (window or main).

pub fn stats(&self) -> CacheStats

Get cache statistics.

pub fn clear(&mut self)

Clear all caches and reset sketch/doorkeeper.

pub fn reset_stats(&mut self)

Reset statistics.

pub fn len(&self) -> usize

Current number of cached entries.

pub fn is_empty(&self) -> bool

Check if cache is empty.

pub fn capacity(&self) -> usize

Total capacity (window + main).

pub fn main_len(&self) -> usize

Number of entries in the main cache.

pub fn window_len(&self) -> usize

Number of entries in the window cache.

Trait Implementations

impl Debug for TinyLfuWidthCache

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

Formats the value using the given formatter.