/
scrape.go
71 lines (61 loc) · 1.29 KB
/
scrape.go
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package dht
import (
"crypto/sha1"
"encoding/binary"
"github.com/bits-and-blooms/bloom/v3"
"math"
"math/bits"
"net"
)
const (
m = 256 * 8
k = 2
)
type ScrapeBloomFilter [256]byte
// Note that if you intend for an IP to be in the IPv4 space, you might want to trim it to 4 bytes
// with IP.To4.
func (me *ScrapeBloomFilter) AddIp(ip net.IP) {
h := sha1.New()
h.Write(ip)
var sum [20]byte
h.Sum(sum[:0])
me.addK(int(sum[0]) | int(sum[1])<<8)
me.addK(int(sum[2]) | int(sum[3])<<8)
}
func (me *ScrapeBloomFilter) addK(index int) {
index %= m
me[index/8] |= 1 << (index % 8)
}
func (me ScrapeBloomFilter) countZeroes() (ret int) {
for _, i := range me {
ret += 8 - bits.OnesCount8(i)
}
return
}
func (me *ScrapeBloomFilter) EstimateCount() float64 {
if me == nil {
return 0
}
c := float64(me.countZeroes())
if c > m-1 {
c = m - 1
}
return math.Log(c/m) / (k * math.Log(1.-1./m))
}
const (
size = 32
byteSize = size * 8
M = byteSize * 8
K = 2
)
func (me *ScrapeBloomFilter) ToBloomFilter() *bloom.BloomFilter {
return bloom.FromWithM(convertBytes(*me), M, K)
}
func convertBytes(b [byteSize]byte) []uint64 {
ret := make([]uint64, size)
for i := 0; i < size; i++ {
startPos := i * 8
ret[i] = binary.BigEndian.Uint64(b[startPos : startPos+8])
}
return ret
}