uuid4.go

// Package uuid4 provides functions for generating and parsing uuids
// compliant with RFC 4122
package uuid4

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"strings"
)

// UUID4 is a container for an RFC 4122 compliant uuid
type UUID4 struct {
	bytes []byte
}

// New generates a new RFC 4122 compliant uuid
func New() UUID4 {
	bytes := make([]byte, 16)
	rand.Read(bytes)

	bytes[6] = byte(0x40 | (int(bytes[6]) & 0xf))
	bytes[8] = byte(0x80 | (int(bytes[8]) & 0x3f))

	return UUID4{bytes: bytes}
}

// String provides the uuid in a format compliant with RFC 4122
func (uuid UUID4) String() string {
	str := hex.EncodeToString(uuid.bytes)

	return str[:8] + "-" + str[8:12] + "-" + str[12:16] + "-" + str[16:20] + "-" + str[20:]
}

// Bytes provides the bytes of the uuid
func (uuid UUID4) Bytes() []byte {
	val := make([]byte, 16)
	copy(val, uuid.bytes)
	return val
}

// ParseString parses a RFC 4122 compliant string representation of a uuid into a UUID4
func ParseString(str string) (uuid UUID4, err error) {
	noDash := strings.Replace(str, "-", "", -1)
	noDash = strings.ToLower(noDash)

	if len(noDash) != 32 {
		return UUID4{}, errors.New(str + " is not a valid UUID4. The unhyphenated string representation should be 32 characters in length")
	}

	if noDash[12] != '4' {
		return UUID4{}, errors.New(str + " is not a valid UUID4. character 13 should be '4'.")
	}

	if noDash[16] != '8' && noDash[16] != '9' && noDash[16] != 'a' && noDash[16] != 'b' {
		return UUID4{}, errors.New(str + " is not a valid UUID4. character 17 should be '8', '9', 'a', or 'b'")
	}

	bytes := make([]byte, 18)
	bytes, err = hex.DecodeString(noDash)

	if err != nil {
		return UUID4{}, err
	}

	return UUID4{bytes: bytes}, nil
}