imgsrv/hash/hash.go

package hash

import (
	"crypto/md5"
	"crypto/sha256"
	"fmt"
	"io"
	"math/rand"
	"strings"
	"time"
)

func init() {
	rand.Seed(time.Now().UnixNano())
}

// Rand64 is an int64 random number
func Rand64() int64 {
	return rand.Int63()
}

// GetMd5FromString is a convinience method for getting md5 sum of a string
func GetMd5FromString(blob string) (sum []byte) {
	h := md5.New()
	defer h.Reset()
	io.WriteString(h, blob)
	return h.Sum(nil)
}

// GetMd5FromBytes is a convinience method for getting md5 sum of some bytes
func GetMd5FromBytes(blob []byte) (sum []byte) {
	h := md5.New()
	defer h.Reset()
	h.Write(blob)
	return h.Sum(nil)
}

// GetSmallHash get a small, decently unique hash
func GetSmallHash(num uint) string {
	h := sha256.New()
	io.WriteString(h, fmt.Sprintf("%d%d", Rand64(), Rand64()))
	return strings.ToLower(fmt.Sprintf("%X", h.Sum(nil)[0:num]))
}