// md5值
func Md5Str(s string) string {
	hash := md5.Sum([]byte(s))
	return hex.EncodeToString(hash[:])
}

// 散列值
func Sha1Str(s string) string {
	r := sha1.Sum([]byte(s))
	return hex.EncodeToString(r[:])
}

// String hashes a string to a unique hashcode.
// https://github.com/hashicorp/terraform/blob/master/helper/hashcode/hashcode.go
// crc32 returns a uint32, but for our use we need
// and non negative integer. Here we cast to an integer
// and invert it if the result is negative.
func HashCode(s string) int {
	v := int(crc32.ChecksumIEEE([]byte(s)))
	if v >= 0 {
		return v
	}
	if -v >= 0 {
		return -v
	}
	// v == MinInt
	return 0
}

// Strings hashes a list of strings to a unique hashcode.
func HashCodes(strings []string) string {
	var buf bytes.Buffer

	for _, s := range strings {
		buf.WriteString(fmt.Sprintf("%s-", s))
	}

	return fmt.Sprintf("%d", HashCode(buf.String()))
}

func main() {
	// 2713056744
	// 1f8689c0dd07ce42757ac01b1ea714f9
	// 9addcbc6fee9c06f43d7110b657f3c61ff707032
	txt := "https://github.com/hashicorp/terraform/blob/master/helper/hashcode/hashcode.go"
	fmt.Println(HashCode(txt))
	fmt.Println(Md5Str(txt))
	fmt.Println(Sha1Str(txt))
}

const (
	Txt = "https://github.com/hashicorp/terraform/blob/master/helper/hashcode/hashcode.go"
)

// go test -test.bench=. -test.benchmem
func BenchmarkMd5Str(b *testing.B) {
	for i := 0; i < b.N; i++ {
		Md5Str(Txt)
	}
}
func BenchmarkHashCode(b *testing.B) {
	for i := 0; i < b.N; i++ {
		HashCode(Txt)
	}
}
func BenchmarkSha1Str(b *testing.B) {
	for i := 0; i < b.N; i++ {
		Sha1Str(Txt)
	}
}

// BenchmarkMd5Str-8    2148428        518 ns/op       144 B/op     3 allocs/op
// BenchmarkHashCode-8   8105571        160 ns/op       80 B/op     1 allocs/op
// BenchmarkSha1Str-8    1836854        700 ns/op       176 B/op     3 allocs/op

// 得出效率: hash_code > md5 > sha1