1 // Copyright 2023 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 "encoding/binary"
8 9 // UUID version 6 is a field-compatible version of UUIDv1, reordered for improved DB locality.
10 // It is expected that UUIDv6 will primarily be used in contexts where there are existing v1 UUIDs.
11 // Systems that do not involve legacy UUIDv1 SHOULD consider using UUIDv7 instead.
12 //
13 // see https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-03#uuidv6
14 //
15 // NewV6 returns a Version 6 UUID based on the current NodeID and clock
16 // sequence, and the current time. If the NodeID has not been set by SetNodeID
17 // or SetNodeInterface then it will be set automatically. If the NodeID cannot
18 // be set NewV6 set NodeID is random bits automatically . If clock sequence has not been set by
19 // SetClockSequence then it will be set automatically. If GetTime fails to
20 // return the current NewV6 returns Nil and an error.
21 func NewV6() (UUID, error) {
22 var uuid UUID
23 now, seq, err := GetTime()
24 if err != nil {
25 return uuid, err
26 }
27 28 /*
29 0 1 2 3
30 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
31 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | time_high |
33 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
34 | time_mid | time_low_and_version |
35 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
36 |clk_seq_hi_res | clk_seq_low | node (0-1) |
37 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
38 | node (2-5) |
39 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 */
41 42 binary.BigEndian.PutUint64(uuid[0:], uint64(now))
43 binary.BigEndian.PutUint16(uuid[8:], seq)
44 45 uuid[6] = 0x60 | (uuid[6] & 0x0F)
46 uuid[8] = 0x80 | (uuid[8] & 0x3F)
47 48 nodeMu.Lock()
49 if nodeID == zeroID {
50 setNodeInterface("")
51 }
52 copy(uuid[10:], nodeID[:])
53 nodeMu.Unlock()
54 55 return uuid, nil
56 }
57