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#![crate_name = "bloomfilter"]
#![crate_type = "rlib"]
#![warn(non_camel_case_types, non_upper_case_globals, unused_qualifications)]
#![allow(clippy::unreadable_literal, clippy::bool_comparison)]
extern crate bit_vec;
extern crate rand;
extern crate siphasher;
use bit_vec::BitVec;
use rand::prelude::*;
use siphasher::sip::SipHasher13;
use std::cmp;
use std::f64;
use std::hash::{Hash, Hasher};
use std::marker::PhantomData;
#[cfg(test)]
use rand::Rng;
pub struct Bloom<T: ?Sized> {
bitmap: BitVec,
bitmap_bits: u64,
k_num: u32,
sips: [SipHasher13; 2],
_phantom: PhantomData<T>,
}
impl<T: ?Sized> Bloom<T> {
pub fn new(bitmap_size: usize, items_count: usize) -> Self {
assert!(bitmap_size > 0 && items_count > 0);
let bitmap_bits = (bitmap_size as u64) * 8u64;
let k_num = Self::optimal_k_num(bitmap_bits, items_count);
let bitmap = BitVec::from_elem(bitmap_bits as usize, false);
let sips = [Self::sip_new(), Self::sip_new()];
Self {
bitmap,
bitmap_bits,
k_num,
sips,
_phantom: PhantomData,
}
}
pub fn new_for_fp_rate(items_count: usize, fp_p: f64) -> Self {
let bitmap_size = Self::compute_bitmap_size(items_count, fp_p);
Bloom::new(bitmap_size, items_count)
}
pub fn from_existing(
bitmap: &[u8],
bitmap_bits: u64,
k_num: u32,
sip_keys: [(u64, u64); 2],
) -> Self {
let sips = [
SipHasher13::new_with_keys(sip_keys[0].0, sip_keys[0].1),
SipHasher13::new_with_keys(sip_keys[1].0, sip_keys[1].1),
];
Self {
bitmap: BitVec::from_bytes(bitmap),
bitmap_bits,
k_num,
sips,
_phantom: PhantomData,
}
}
pub fn compute_bitmap_size(items_count: usize, fp_p: f64) -> usize {
assert!(items_count > 0);
assert!(fp_p > 0.0 && fp_p < 1.0);
let log2 = f64::consts::LN_2;
let log2_2 = log2 * log2;
((items_count as f64) * f64::ln(fp_p) / (-8.0 * log2_2)).ceil() as usize
}
pub fn set(&mut self, item: &T)
where
T: Hash,
{
let mut hashes = [0u64, 0u64];
for k_i in 0..self.k_num {
let bit_offset = (self.bloom_hash(&mut hashes, &item, k_i) % self.bitmap_bits) as usize;
self.bitmap.set(bit_offset, true);
}
}
pub fn check(&self, item: &T) -> bool
where
T: Hash,
{
let mut hashes = [0u64, 0u64];
for k_i in 0..self.k_num {
let bit_offset = (self.bloom_hash(&mut hashes, &item, k_i) % self.bitmap_bits) as usize;
if self.bitmap.get(bit_offset).unwrap() == false {
return false;
}
}
true
}
pub fn check_and_set(&mut self, item: &T) -> bool
where
T: Hash,
{
let mut hashes = [0u64, 0u64];
let mut found = true;
for k_i in 0..self.k_num {
let bit_offset = (self.bloom_hash(&mut hashes, &item, k_i) % self.bitmap_bits) as usize;
if self.bitmap.get(bit_offset).unwrap() == false {
found = false;
self.bitmap.set(bit_offset, true);
}
}
found
}
pub fn bitmap(&self) -> Vec<u8> {
self.bitmap.to_bytes()
}
pub fn number_of_bits(&self) -> u64 {
self.bitmap_bits
}
pub fn number_of_hash_functions(&self) -> u32 {
self.k_num
}
pub fn sip_keys(&self) -> [(u64, u64); 2] {
[self.sips[0].keys(), self.sips[1].keys()]
}
fn optimal_k_num(bitmap_bits: u64, items_count: usize) -> u32 {
let m = bitmap_bits as f64;
let n = items_count as f64;
let k_num = (m / n * f64::ln(2.0f64)).ceil() as u32;
cmp::max(k_num, 1)
}
fn bloom_hash(&self, hashes: &mut [u64; 2], item: &T, k_i: u32) -> u64
where
T: Hash,
{
if k_i < 2 {
let sip = &mut self.sips[k_i as usize].clone();
item.hash(sip);
let hash = sip.finish();
hashes[k_i as usize] = hash;
hash
} else {
hashes[0].wrapping_add((k_i as u64).wrapping_mul(hashes[1]) % 0xffffffffffffffc5)
}
}
pub fn clear(&mut self) {
self.bitmap.clear()
}
fn sip_new() -> SipHasher13 {
let mut rng = thread_rng();
SipHasher13::new_with_keys(rng.gen(), rng.gen())
}
}
#[test]
fn bloom_test_set() {
let mut rng = thread_rng();
let mut bloom = Bloom::new(10, 80);
let mut key = vec![0u8, 16];
rng.fill_bytes(&mut key);
assert!(bloom.check(&key) == false);
bloom.set(&key);
assert!(bloom.check(&key) == true);
}
#[test]
fn bloom_test_check_and_set() {
let mut rng = thread_rng();
let mut bloom = Bloom::new(10, 80);
let mut key = vec![0u8, 16];
rng.fill_bytes(&mut key);
assert!(bloom.check_and_set(&key) == false);
assert!(bloom.check_and_set(&key) == true);
}
#[test]
fn bloom_test_clear() {
let mut rng = thread_rng();
let mut bloom = Bloom::new(10, 80);
let mut key = vec![0u8, 16];
rng.fill_bytes(&mut key);
bloom.set(&key);
assert!(bloom.check(&key) == true);
bloom.clear();
assert!(bloom.check(&key) == false);
}
#[test]
fn bloom_test_load() {
let mut rng = thread_rng();
let mut original = Bloom::new(10, 80);
let mut key = vec![0u8, 16];
rng.fill_bytes(&mut key);
original.set(&key);
assert!(original.check(&key) == true);
let cloned = Bloom::from_existing(
&original.bitmap(),
original.number_of_bits(),
original.number_of_hash_functions(),
original.sip_keys(),
);
assert!(cloned.check(&key) == true);
}