Struct xorf::Xor32 [−][src]
Expand description
Xor filter using 32-bit fingerprints.
An Xor32
filter uses <40 bits per entry of the set is it constructed from, and has a false
positive rate of effectively zero (1/2^32 =~ 1/4 billion). As with other probabilistic filters,
a higher number of entries decreases the bits per entry but increases the false positive rate.
An Xor32
is constructed from a set of 64-bit unsigned integers and is immutable.
use xorf::{Filter, Xor32}; const SAMPLE_SIZE: usize = 1_000_000; let keys: Vec<u64> = (0..SAMPLE_SIZE).map(|_| rng.gen()).collect(); let filter = Xor32::from(&keys); // no false negatives for key in keys { assert!(filter.contains(&key)); } // bits per entry let bpe = (filter.len() as f64) * 32.0 / (SAMPLE_SIZE as f64); assert!(bpe < 40., "Bits per entry is {}", bpe); // false positive rate let false_positives: usize = (0..SAMPLE_SIZE) .map(|_| rng.gen()) .filter(|n| filter.contains(n)) .count(); let fp_rate: f64 = (false_positives * 100) as f64 / SAMPLE_SIZE as f64; assert!(fp_rate < 0.0000000000000001, "False positive rate is {}", fp_rate);
Serializing and deserializing Xor32
filters can be enabled with the serde
feature.
Fields
seed: u64
The seed for the filter
block_length: usize
The number of blocks in the filter
fingerprints: Box<[u32]>
The fingerprints for the filter
Trait Implementations
Auto Trait Implementations
impl RefUnwindSafe for Xor32
impl UnwindSafe for Xor32