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hash function

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charlie
2023-11-03 16:27:14 +08:00
parent 249d3b4682
commit 5428b530b2
1 changed files with 6 additions and 3 deletions
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9
bloom/bloom.go
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@ -12,7 +12,7 @@ import (
const DEFAULT_SIZE = 2 << 24 const DEFAULT_SIZE = 2 << 24
var seeds = []uint{7, 11, 13, 31, 37, 61} var seeds = []uint{7, 11, 13, 31, 37, 61, 79, 97}
type bitStore interface { type bitStore interface {
Clear() Clear()
@ -51,6 +51,9 @@ func New(expectedInsertions uint, fpp float64, opts ...option) *BloomFilter {
bits := optimalNumOfBits(expectedInsertions, fpp) bits := optimalNumOfBits(expectedInsertions, fpp)
k := optimalNumOfHashFunctions(bits, expectedInsertions) k := optimalNumOfHashFunctions(bits, expectedInsertions)
if k > uint(len(seeds)) {
k = uint(len(seeds))
}
bf := &BloomFilter{ bf := &BloomFilter{
bits: bits, bits: bits,
@ -74,7 +77,7 @@ func (bf *BloomFilter) ExistString(data string) (bool, error) {
} }
func (bf *BloomFilter) Exists(data []byte) (bool, error) { func (bf *BloomFilter) Exists(data []byte) (bool, error) {
if data == nil || len(data) == 0 { if len(data) == 0 {
return false, nil return false, nil
} }
@ -90,7 +93,7 @@ func (bf *BloomFilter) Exists(data []byte) (bool, error) {
func (bf *BloomFilter) geOffsets(data []byte) []uint { func (bf *BloomFilter) geOffsets(data []byte) []uint {
offsets := make([]uint, bf.funcs) offsets := make([]uint, bf.funcs)
for i := uint(0); i < bf.funcs; i++ { for i := uint(0); i < bf.funcs; i++ {
offsets[i] = uint(hash.Murmur3(append(data, byte(i))) % uint64(bf.bits)) offsets[i] = uint(hash.Murmur3(append(data, byte(seeds[i]))) % uint64(bf.bits))
} }
return offsets return offsets