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

extern crate rand;
extern crate seahash;

use rand::Rng;

const LN2: f32 = std::f32::consts::LN_2;
const LN2_SQUARED: f32 = LN2 * LN2;

mod test;

pub struct Seabloom
{
    seeds: Vec<u64>,
    bitcount: u64,
    bitfield: Vec<u32>,
}

impl Seabloom
{
    pub fn new(bitcount: u64, seeds: Vec<u64>) -> Seabloom
    {
        let buf: Vec<u32> = vec![0; (bitcount as f32 / 32.0_f32).ceil() as usize];

        Seabloom
        {
            seeds: seeds,
            bitcount: bitcount,
            bitfield: buf,
        }
    }

    pub fn create_random_seeds(bitcount: u64, hashcount: u32) -> Seabloom
    {
        let mut seeds: Vec<u64> = Vec::new();
        let mut rng = rand::thread_rng();
        for _ in 0..hashcount * 4
        {
            seeds.push(rng.gen::<u64>());
        }

        Seabloom::new(bitcount as u64, seeds)
    }

    pub fn create_optimal(item_count: u32, error_rate: f32) -> Seabloom
    {
        let bitcount = (-1.0_f32 * (item_count as f32) * error_rate.ln() / LN2_SQUARED)
            .round();
        let hashcount = (bitcount / (item_count as f32) * LN2)
            .round() as u32;

        Seabloom::create_random_seeds(bitcount as u64, hashcount)
    }

    pub fn create(item_count: u32) -> Seabloom
    {
        Seabloom::create_optimal(item_count, 0.005_f32)
    }

    pub fn clear(&mut self)
    {
        let buf: Vec<u32> = vec![0; (self.bitcount as f32 / 8.0_f32).ceil() as usize];
        self.bitfield = buf;
    }

    fn setbit(&mut self, bit: u64)
    {
        let mut pos: usize = 0;
        let mut shift = bit;
    	while shift > 31
    	{
    		pos += 1;
    		shift -= 32;
    	}

        let mut chunk = self.bitfield[pos];
        chunk |= 0x1 << shift;
        self.bitfield[pos] = chunk;
    }

    fn getbit(&self, bit: u64) -> bool
    {
        let mut pos: usize = 0;
        let mut shift = bit;
    	while shift > 31
    	{
            pos += 1;
    		shift -= 32;
    	}

        let chunk = self.bitfield[pos];
    	(chunk & (0x1 << shift)) != 0
    }

    pub fn add_bytes(&mut self, bytes: &[u8])
    {
        let mut i: usize = 0;
        loop
        {
            let hash = seahash::hash_seeded(bytes, self.seeds[i], self.seeds[i+1], self.seeds[i+2], self.seeds[i+3]);
            let bit = hash % self.bitcount;
            self.setbit(bit);
            i += 4;
            if i >= self.seeds.len() { break; }
        }
    }

    pub fn add(&mut self, item: &str)
    {
        self.add_bytes(item.as_bytes());
    }

    pub fn add_list(&mut self, items: Vec<&str>)
    {
        for item in items.iter() { self.add(item); }
    }

    pub fn has_bytes(&self, bytes: &[u8]) -> bool
    {
        let mut i: usize = 0;
        loop
        {
            let hash = seahash::hash_seeded(bytes, self.seeds[i], self.seeds[i+1], self.seeds[i+2], self.seeds[i+3]);
            let bit = hash % self.bitcount;
            if !self.getbit(bit) { return false; }

            i += 4;
            if i >= self.seeds.len() { break; }
        }

        true
    }

    pub fn has(&self, item: &str) -> bool
    {
        self.has_bytes(item.as_bytes())
    }

}