import (

    "crypto/md5"

    "encoding/hex"

    "encoding/json"

    "fmt"

    "hash/crc32"

    "hash/fnv"

    "strconv"

)

//string to hash

//字符串转化为hash值   使用的是 IEEE 

func MakeHash(s string) string {

    const IEEE = 0xedb88320

    var IEEETable = crc32.MakeTable(IEEE) //创建IEEE table

    hash := fmt.Sprintf("%x", crc32.Checksum([]byte(s), IEEETable))

    return hash

}

//字符串转化为hash值

func HashString(encode string) uint64 {

    hash := fnv.New64()

    hash.Write([]byte(encode))

    return hash.Sum64()

}

// 制作特征值方法一

func MakeUnique(obj interface{}) string {

    baseString, _ := json.Marshal(obj)

    return strconv.FormatUint(HashString(string(baseString)), 10)

}

// 制作特征值方法二

func MakeMd5(obj interface{}, length int) string {

    if length > 32 {

        length = 32

    }

    h := md5.New()

    baseString, _ := json.Marshal(obj)

    h.Write([]byte(baseString))

    s := hex.EncodeToString(h.Sum(nil))//转化为16进制字符串

    return s[:length]

}