uuid.go

// Written by Dmitry Chestnykh. Public domain.
// Package uuid provides Universally unique identifiers.
package uuid

import (
	"crypto/rand"
	"fmt"
	"io"
)

type UUID string

// Bytes returns a bytes representation of UUID or nil if UUID has bad format.
func (u UUID) Bytes() []byte {
	var b [16]byte
	n, err := fmt.Sscanf(string(u),
		"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
		&b[0], &b[1], &b[2], &b[3], &b[4], &b[5], &b[6], &b[7], &b[8],
		&b[9], &b[10], &b[11], &b[12], &b[13], &b[14], &b[15])
	if n != 16 || err != nil {
		return nil
	}
	return b[:]
}

// FromBytes returns UUID from bytes representation.
func FromBytes(b []byte) UUID {
	return UUID(fmt.Sprintf("%08x-%04x-%04x-%04x-%012x", b[:4], b[4:6], b[6:8], b[8:10], b[10:]))
}

// New returns a new random UUID v4.
func New() UUID {
	var b [16]byte
	if _, err := io.ReadFull(rand.Reader, b[:]); err != nil {
		panic("error reading random numbers: " + err.Error())
	}
	b[6] = (b[6] & 0x0f) | (4 << 4)
	b[8] = (b[8] & 0xbf) | 0x80
	return FromBytes(b[:])
}

uuid_test.go

package uuid

import (
	"bytes"
	"testing"
)

const id = UUID("5154e02d-57cd-4da9-9194-d199946681a6")

func TestBytes(t *testing.T) {
	good := []byte{0x51, 0x54, 0xe0, 0x2d, 0x57, 0xcd, 0x4d, 0xa9, 0x91, 0x94, 0xd1, 0x99, 0x94, 0x66, 0x81, 0xa6}
	b := id.Bytes()
	if b == nil {
		t.Fatalf("returned nil")
	}
	if !bytes.Equal(good, b) {
		t.Fatalf("wrong result: expected %x, got %x", good, b)
	}
}

func TestBadBytes(t *testing.T) {
	bad := "ZZCAFA12-F257-11E3-B24E-B7BCECBA0006"
	b := UUID(bad).Bytes()
	if b != nil {
		t.Fatalf("converted bad uuid (%s): %x", bad, b)
	}
}

func TestFromBytes(t *testing.T) {
	b := id.Bytes()
	s := FromBytes(b)
	if id != s {
		t.Fatalf("wrong result: expected %s, got %s", id, s)
	}
}

func TestNew(t *testing.T) {
	m := make(map[UUID]interface{})
	var yes interface{}
	for i := 0; i < 10000; i++ {
		v := New()
		if _, ok := m[v]; ok {
			t.Errorf("uuid: collision on %d: %s", i, v)
		}
		m[v] = yes
	}
}