Struct ScalableBloomFilter 

pub struct ScalableBloomFilter { /* private fields */ }

Auto-growing Bloom filter that adds new layers when the estimated false-positive rate of the current layer exceeds a threshold.

Each layer is an independent BloomFilter with geometrically increasing capacity. A contains query checks all layers; an insert goes into the active (most recent) layer. When the active layer’s estimated FPR exceeds max_fpr_per_layer, a new layer is allocated with capacity scaled by growth_factor.

The overall false-positive rate is bounded by the geometric series p₀ + p₁ + p₂ + … where each pᵢ = max_fpr_per_layer * tightening_ratioⁱ. With a tightening ratio < 1 (default 0.8) the series converges.

Implementations

impl ScalableBloomFilter

pub fn new(initial_capacity: usize, target_fpr: f64, growth_factor: f64) -> Self

Create a new ScalableBloomFilter.

Parameters

• initial_capacity — expected items for the first layer (must be > 0).
• target_fpr — target false-positive rate per layer in (0, 1).
• growth_factor — how much each successive layer grows (>1.0, e.g. 2.0).

pub fn insert(&mut self, item: &[u8])

Insert item into the active (most recent) layer.

If the active layer’s estimated FPR exceeds max_fpr_per_layer after insertion, a new layer is allocated.

pub fn contains(&self, item: &[u8]) -> bool

Return true if item may be in any layer; false means it definitely was never inserted.

pub fn estimate_false_positive_rate(&self) -> f64

Estimate the aggregate false-positive rate across all layers.

The overall FPR is 1 - Π(1 - fprᵢ) (probability of at least one layer reporting a false positive).

pub fn total_item_count(&self) -> u64

Return the total number of items inserted across all layers.

pub fn layer_count(&self) -> usize

Return the number of layers currently allocated.

pub fn set_tightening_ratio(&mut self, ratio: f64)

Set the tightening ratio (must be in (0, 1)).

Each successive layer uses fpr * tightening_ratio^i to keep the aggregate FPR bounded. A lower ratio means tighter per-layer FPR targets (more bits per layer).

pub fn tightening_ratio(&self) -> f64

Return the tightening ratio.

pub fn growth_factor(&self) -> f64

Return the growth factor.

pub fn layer_stats(&self) -> Vec<(u64, usize, f64)>

Return per-layer statistics: (item_count, num_bits, estimated_fpr).

pub fn estimated_capacity_remaining(&self) -> usize

Return the estimated remaining capacity of the active (most recent) layer before it triggers a new layer allocation.

This is approximate: it counts how many more items can be inserted before the active layer’s estimated FPR exceeds max_fpr_per_layer. Returns 0 if the active layer has already exceeded its FPR target.

pub fn clear(&mut self)

Clear all layers and reset to a single fresh layer.

pub fn total_bits(&self) -> usize

Return the total number of bits across all layers.

Trait Implementations

impl Clone for ScalableBloomFilter

fn clone(&self) -> ScalableBloomFilter

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ScalableBloomFilter

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

Formats the value using the given formatter.