1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
extern crate bigint;
extern crate bit_vec;
extern crate fasthash;
use bigint::uint::U512;
use bit_vec::BitVec;
use fasthash::murmur3::hash128;
use std::ops::Add;
pub struct BloomFilter {
capacity: usize,
bitvec: BitVec,
error_rate: f64,
num_of_hashfuncs: usize,
num_of_elements: usize,
}
#[inline]
fn nbits(n: usize, p: f64) -> usize {
let numerator = n as f64 * p.ln();
let denominator = (1.0_f64 / 2.0_f64.powf(2.0_f64.ln())).ln();
(numerator / denominator).ceil() as usize
}
#[inline]
fn iterations(m: usize, n: usize) -> usize {
((m as f64 / n as f64) * 2.0_f64.ln()).round() as usize
}
impl BloomFilter {
pub fn from_elem(capacity: usize, error_rate: f64) -> BloomFilter {
if capacity == 0 {
panic!("capacity must be a greater than zero");
}
if error_rate <= 0.0 {
panic!("error_rate must be greater than zero");
}
let num_of_bits = nbits(capacity, error_rate);
let num_of_hashfuncs = iterations(num_of_bits, capacity);
BloomFilter {
bitvec: BitVec::from_elem(num_of_bits, false),
capacity,
error_rate,
num_of_hashfuncs,
num_of_elements: 0,
}
}
pub fn bitvec_len(&self) -> usize {
self.bitvec.len()
}
pub fn capacity(&self) -> usize {
self.capacity
}
pub fn len(&self) -> usize {
self.num_of_elements
}
pub fn error_rate(&self) -> f64 {
self.error_rate
}
pub fn is_empty(&self) -> bool {
self.len() == 0
}
pub fn add(&mut self, data: &[u8]) -> Result<bool, &'static str> {
if self.num_of_elements == self.capacity {
return Err("You are adding to the bloom filter that is full");
}
let hash = hash128(data);
let hash64_first = (hash & (2_u128.pow(64) - 1)) as u64;
let hash64_second = (hash >> 64) as u64;
let mut result_hash: U512 = hash64_first.into();
for value in 0..self.num_of_hashfuncs {
let temp: U512 = U512::from(value) * U512::from(hash64_second);
result_hash = result_hash.add(temp);
let index = result_hash % U512::from(self.bitvec_len());
self.bitvec.set(index.as_u64() as usize, true);
}
self.num_of_elements += 1;
Ok(true)
}
pub fn contains(&self, data: &[u8]) -> bool {
let hash = hash128(data);
let hash64_first = (hash & (2_u128.pow(64) - 1)) as u64;
let hash64_second = (hash >> 64) as u64;
let mut result_hash: U512 = hash64_first.into();
for value in 0..self.num_of_hashfuncs {
let temp: U512 = U512::from(value) * U512::from(hash64_second);
result_hash = result_hash.add(temp);
let index = result_hash % U512::from(self.bitvec_len());
if self.bitvec.get(index.as_u64() as usize) == Some(false) {
return false;
}
}
true
}
}
#[cfg(test)]
mod tests {
use crate::BloomFilter;
#[test]
fn test_single_element() {
let mut b = BloomFilter::from_elem(20000, 0.01);
assert!(b.add("Test".as_ref()).unwrap(), true);
assert!(b.contains("Test".as_ref()));
}
#[test]
#[should_panic]
fn test_empty_bloom_zero_capacity_filter() {
let _b = BloomFilter::from_elem(0, 0.01);
}
#[test]
#[should_panic]
fn test_empty_bloom_zero_error_rate_filter() {
let _b = BloomFilter::from_elem(10, 0.000);
}
#[test]
#[should_panic]
fn test_empty_bloom_negative_error_rate_filter() {
let _b = BloomFilter::from_elem(10, -0.010);
}
#[test]
fn test_full_bloom_filter() {
let mut b = BloomFilter::from_elem(10, 0.01);
let elements = vec![
"Srinivas",
"Reddy",
"Gundrapally",
"Nekkonda",
"Warangal",
"Telangana",
"506122",
"Srinivas1",
"Reddy1",
"Gundrapally1",
"Telangana1",
];
for element in &elements[..9] {
assert!(b.add(element.as_ref()).unwrap(), true);
}
assert!(
b.add((&elements[10]).as_ref()).unwrap(),
"You are adding to the bloom filter that is full"
);
}
#[test]
fn test_multiple_elements() {
let mut b = BloomFilter::from_elem(20000, 0.01);
let elements = vec![
"Srinivas",
"Reddy",
"Gundrapally",
"Nekkonda",
"Warangal",
"Telangana",
"506122",
];
for element in &elements {
b.add(element.as_ref()).unwrap();
}
for element in &elements {
assert!(b.contains(element.as_ref()));
}
assert_eq!(b.contains("rajaa".as_ref()), false);
assert_eq!(elements.len(), b.len())
}
}