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use extended_primitives::Buffer;
use fasthash::murmur3;
#[derive(Debug, Clone, PartialEq)]
pub struct BloomFilter {
pub filter: Buffer,
pub n: u32,
pub tweak: u32,
}
const OFFSET: u32 = 0xfba4c795;
impl BloomFilter {
fn hash(&self, value: &[u8], n: u32) -> u32 {
let seed = n.overflowing_mul(OFFSET).0.overflowing_add(self.tweak).0;
murmur3::hash32_with_seed(value, seed)
}
pub fn new(n: u32, tweak: u32) -> Self {
BloomFilter {
filter: Buffer::new(),
n,
tweak,
}
}
pub fn new_with_filter(filter: Vec<u8>, n: u32, tweak: u32) -> Self {
BloomFilter {
filter: Buffer::from(filter),
n,
tweak,
}
}
pub fn add(&mut self, value: &[u8]) {
for i in 0..self.n {
let index = self.hash(value, i);
self.filter[(index >> 3) as usize] |= 1 << (7 & index);
}
}
pub fn test(&self, value: &[u8]) -> bool {
for i in 0..self.n {
let index = self.hash(value, i);
if self.filter[(index >> 3) as usize] & (1 << (7 & index)) == 0 {
return false;
}
}
true
}
}