1// Copyright 2016 Google Inc.  All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package uuid
6
7import (
8	"encoding/binary"
9)
10
11// NewUUID returns a Version 1 UUID based on the current NodeID and clock
12// sequence, and the current time.  If the NodeID has not been set by SetNodeID
13// or SetNodeInterface then it will be set automatically.  If the NodeID cannot
14// be set NewUUID returns nil.  If clock sequence has not been set by
15// SetClockSequence then it will be set automatically.  If GetTime fails to
16// return the current NewUUID returns nil and an error.
17//
18// In most cases, New should be used.
19func NewUUID() (UUID, error) {
20	nodeMu.Lock()
21	if nodeID == zeroID {
22		setNodeInterface("")
23	}
24	nodeMu.Unlock()
25
26	var uuid UUID
27	now, seq, err := GetTime()
28	if err != nil {
29		return uuid, err
30	}
31
32	timeLow := uint32(now & 0xffffffff)
33	timeMid := uint16((now >> 32) & 0xffff)
34	timeHi := uint16((now >> 48) & 0x0fff)
35	timeHi |= 0x1000 // Version 1
36
37	binary.BigEndian.PutUint32(uuid[0:], timeLow)
38	binary.BigEndian.PutUint16(uuid[4:], timeMid)
39	binary.BigEndian.PutUint16(uuid[6:], timeHi)
40	binary.BigEndian.PutUint16(uuid[8:], seq)
41	copy(uuid[10:], nodeID[:])
42
43	return uuid, nil
44}
45