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extern crate bit_vec;
use bit_vec::BitVec;
use std::hash::{Hash, SipHasher, Hasher};
use std::fmt;
pub struct BloomFilter {
size: usize,
hash_count: usize,
bloom: BitVec,
bits_full: usize,
hashers: [SipHasher; 2]
}
impl fmt::Debug for BloomFilter {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "BloomFilter: size: {:?}, hash_count: {:?}, bits_full: {:?}, fill ratio: {:?}", self.size, self.hash_count, self.bits_full, self.bits_full as f32/self.size as f32)
}
}
impl BloomFilter {
pub fn new(size: usize, hash_count: usize) -> BloomFilter {
BloomFilter {
size: size,
hash_count: hash_count,
bloom: BitVec::from_elem(size, false),
bits_full: 0,
hashers: [SipHasher::new(), SipHasher::new()]
}
}
pub fn new_with_params(n: usize, p: f32) -> BloomFilter {
let m = ((-(n as f32 * (p.ln()))).ceil() / ((2.0f32).ln().powi(2))) as usize;
let k = (((2.0f32).ln() * (m as f32/ n as f32)).round()) as usize;
BloomFilter {
size: m,
hash_count: k,
bloom: BitVec::from_elem(m, false),
bits_full: 0,
hashers: [SipHasher::new(), SipHasher::new()]
}
}
pub fn add<T: Hash>(&mut self, val: T) {
for n in 0..self.hash_count {
let seed = n as u64;
let hashed = self.bloom_hash(seed, &val);
if !self.bloom.get(hashed).unwrap() {
self.bits_full += 1;
}
self.bloom.set(hashed, true);
}
}
pub fn query<T: Hash>(&self, query_val: T) -> bool{
for n in 0..self.hash_count {
let seed = n as u64;
let hashed = self.bloom_hash(seed, &query_val);
if !self.bloom.get(hashed).unwrap() {
return false;
}
}
true
}
fn bloom_hash<T: Hash>(&self, seed: u64, val: &T) -> usize {
let mut sip1 = self.hashers[0].clone();
let mut sip2 = self.hashers[1].clone();
val.hash(&mut sip1);
val.hash(&mut sip2);
let fin1 = sip1.finish();
let fin2 = sip2.finish();
(fin1.wrapping_mul(fin2.wrapping_add(seed)) % (self.size as u64)) as usize
}
pub fn get_bits_set(&self) -> usize {
self.bloom.iter().filter(|x| *x).count()
}
pub fn clear(&mut self) {
self.bloom.clear();
self.bits_full = 0;
}
}
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
}
}