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// Copyright 2023 Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package uuid
import "encoding/binary"
// UUID version 6 is a field-compatible version of UUIDv1, reordered for improved DB locality.
// It is expected that UUIDv6 will primarily be used in contexts where there are existing v1 UUIDs.
// Systems that do not involve legacy UUIDv1 SHOULD consider using UUIDv7 instead.
//
// see https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-03#uuidv6
//
// NewV6 returns a Version 6 UUID based on the current NodeID and clock
// sequence, and the current time. If the NodeID has not been set by SetNodeID
// or SetNodeInterface then it will be set automatically. If the NodeID cannot
// be set NewV6 set NodeID is random bits automatically . If clock sequence has not been set by
// SetClockSequence then it will be set automatically. If GetTime fails to
// return the current NewV6 returns Nil and an error.
func NewV6() (UUID, error) {
var uuid UUID
now, seq, err := GetTime()
if err != nil {
return uuid, err
}
/*
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| time_high |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| time_mid | time_low_and_version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|clk_seq_hi_res | clk_seq_low | node (0-1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| node (2-5) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
binary.BigEndian.PutUint64(uuid[0:], uint64(now))
binary.BigEndian.PutUint16(uuid[8:], seq)
uuid[6] = 0x60 | (uuid[6] & 0x0F)
uuid[8] = 0x80 | (uuid[8] & 0x3F)
nodeMu.Lock()
if nodeID == zeroID {
setNodeInterface("")
}
copy(uuid[10:], nodeID[:])
nodeMu.Unlock()
return uuid, nil
}
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