Added Base58 encoder/decoder

snowflake.go

@@ -19,6 +19,25 @@ const (
 	nodeShift uint8 = stepBits
 )
 
+const encodeBase58Map = "123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ"
+
+var decodeBase58Map [256]byte
+
+// Create a map for decoding Base58.  This speeds up the process tremendously.
+func init() {
+
+	for i := 0; i < len(encodeBase58Map); i++ {
+		decodeBase58Map[i] = 0xFF
+	}
+
+	for i := 0; i < len(encodeBase58Map); i++ {
+		decodeBase58Map[encodeBase58Map[i]] = byte(i)
+	}
+}
+
+// ErrInvalidBase58 is returned by ParseBase58 when given an invalid []byte
+var ErrInvalidBase58 = errors.New("invalid base58")
+
 // Epoch is set to the twitter snowflake epoch of 2006-03-21:20:50:14 GMT
 // You may customize this to set a different epoch for your application.
 var Epoch int64 = 1288834974657
@@ -101,6 +120,42 @@ func (f ID) Base36() string {
 	return strconv.FormatInt(int64(f), 36)
 }
 
+// Base58 returns a base58 string of the snowflake ID
+func (f ID) Base58() string {
+
+	if f < 58 {
+		return string(encodeBase58Map[f])
+	}
+
+	b := make([]byte, 0, 11)
+	for f >= 58 {
+		b = append(b, encodeBase58Map[f%58])
+		f /= 58
+	}
+	b = append(b, encodeBase58Map[f])
+
+	for x, y := 0, len(b)-1; x < y; x, y = x+1, y-1 {
+		b[x], b[y] = b[y], b[x]
+	}
+
+	return string(b)
+}
+
+// ParseBase58 parses a base58 []byte into a snowflake ID
+func ParseBase58(b []byte) (ID, error) {
+
+	var id int64
+
+	for i := range b {
+		if decodeBase58Map[b[i]] == 0xFF {
+			return -1, ErrInvalidBase58
+		}
+		id = id*58 + int64(decodeBase58Map[b[i]])
+	}
+
+	return ID(id), nil
+}
+
 // Base64 returns a base64 string of the snowflake ID
 func (f ID) Base64() string {
 	return base64.StdEncoding.EncodeToString(f.Bytes())