A BloomFilter implementation

bloomfilter.go

package main

import (
	"bufio"
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"math/big"
	"os"
)

type HashFunc func(e string) int
type BloomFilter struct {
	filter    []bool
	hashFuncs []HashFunc
}

func (b *BloomFilter) build(m, k int) {
	b.filter = make([]bool, m)
	for i := 0; i < k; i++ {
		b.hashFuncs = append(b.hashFuncs, genHashFunc(m, i))
	}

}

func (b *BloomFilter) regist(e string) {
	k := len(b.hashFuncs)
	for i := 0; i < k; i++ {
		idx := b.hashFuncs[i](e)
		b.filter[idx] = true
	}
}

func (b *BloomFilter) check(e string) bool {
	k := len(b.hashFuncs)
	var result = true
	for i := 0; i < k; i++ {
		idx := b.hashFuncs[i](e)
		if !b.filter[idx] {
			result = false
		}
	}
	return result
}

func genHashFunc(m, i int) HashFunc {
	return func(e string) int {
		bi := big.NewInt(0)
		h := md5.New()
		h.Write([]byte(fmt.Sprintf("%d%s", i, e)))
		hexstr := hex.EncodeToString(h.Sum(nil))
		bi.SetString(hexstr, 16)
		mo := bi.Mod(bi, big.NewInt(int64(m)))
		return int(mo.Int64())
	}
}

func main() {
	M := 256
	K := 16
	bf := BloomFilter{}
	bf.build(M, K)

	sc := bufio.NewScanner(os.Stdin)
	for {
		fmt.Printf("(Enter exit to finish registration)\n")
		fmt.Printf("add > ")
		sc.Scan()
		in := sc.Text()
		if in == "exit" {
			break
		}
		bf.regist(in)
	}
	for {
		fmt.Printf("(Enter exit to exit)\n")
		fmt.Printf("check > ")
		sc.Scan()
		in := sc.Text()
		if in == "exit" {
			break
		}
		if bf.check(in) {
			fmt.Println("Hit")
		} else {
			fmt.Println("Miss")
		}
	}
}