布隆过滤器

bloom/bloom.go

@@ -0,0 +1,51 @@
+package bloom
+
+import "github.com/bits-and-blooms/bitset"
+
+const DEFAULT_SIZE = 2 << 24
+
+var seeds = []uint{7, 11, 13, 31, 37, 61}
+
+type simplehash struct {
+	cap  uint
+	seed uint
+}
+
+type BloomFilter struct {
+	set   *bitset.BitSet
+	funcs [6]simplehash
+}
+
+func NewBloomFilter() *BloomFilter {
+	bf := new(BloomFilter)
+	for i := 0; i < len(bf.funcs); i++ {
+		bf.funcs[i] = simplehash{DEFAULT_SIZE, seeds[i]}
+	}
+	bf.set = bitset.New(DEFAULT_SIZE)
+	return bf
+}
+
+func (bf *BloomFilter) Add(value string) {
+	for _, f := range bf.funcs {
+		bf.set.Set(f.hash(value))
+	}
+}
+
+func (bf *BloomFilter) Contains(value string) bool {
+	if value == "" {
+		return false
+	}
+	ret := true
+	for _, f := range bf.funcs {
+		ret = ret && bf.set.Test(f.hash(value))
+	}
+	return ret
+}
+
+func (s simplehash) hash(value string) uint {
+	var result uint = 0
+	for i := 0; i < len(value); i++ {
+		result = result*s.seed + uint(value[i])
+	}
+	return (s.cap - 1) & result
+}