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 5 package uuid
6 7 import (
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.
19 func NewUUID() (UUID, error) {
20 var uuid UUID
21 now, seq, err := GetTime()
22 if err != nil {
23 return uuid, err
24 }
25 26 timeLow := uint32(now & 0xffffffff)
27 timeMid := uint16((now >> 32) & 0xffff)
28 timeHi := uint16((now >> 48) & 0x0fff)
29 timeHi |= 0x1000 // Version 1
30 31 binary.BigEndian.PutUint32(uuid[0:], timeLow)
32 binary.BigEndian.PutUint16(uuid[4:], timeMid)
33 binary.BigEndian.PutUint16(uuid[6:], timeHi)
34 binary.BigEndian.PutUint16(uuid[8:], seq)
35 36 nodeMu.Lock()
37 if nodeID == zeroID {
38 setNodeInterface("")
39 }
40 copy(uuid[10:], nodeID[:])
41 nodeMu.Unlock()
42 43 return uuid, nil
44 }
45