podman
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 uuid6
7import (8"encoding/binary"9"sync"10"time"11)
12
13// A Time represents a time as the number of 100's of nanoseconds since 15 Oct
14// 1582.
15type Time int6416
17const (18lillian = 2299160 // Julian day of 15 Oct 158219unix = 2440587 // Julian day of 1 Jan 197020epoch = unix - lillian // Days between epochs21g1582 = epoch * 86400 // seconds between epochs22g1582ns100 = g1582 * 10000000 // 100s of a nanoseconds between epochs23)
24
25var (26timeMu sync.Mutex27lasttime uint64 // last time we returned28clockSeq uint16 // clock sequence for this run29
30timeNow = time.Now // for testing31)
32
33// UnixTime converts t the number of seconds and nanoseconds using the Unix
34// epoch of 1 Jan 1970.
35func (t Time) UnixTime() (sec, nsec int64) {36sec = int64(t - g1582ns100)37nsec = (sec % 10000000) * 10038sec /= 1000000039return sec, nsec40}
41
42// GetTime returns the current Time (100s of nanoseconds since 15 Oct 1582) and
43// clock sequence as well as adjusting the clock sequence as needed. An error
44// is returned if the current time cannot be determined.
45func GetTime() (Time, uint16, error) {46defer timeMu.Unlock()47timeMu.Lock()48return getTime()49}
50
51func getTime() (Time, uint16, error) {52t := timeNow()53
54// If we don't have a clock sequence already, set one.55if clockSeq == 0 {56setClockSequence(-1)57}58now := uint64(t.UnixNano()/100) + g1582ns10059
60// If time has gone backwards with this clock sequence then we61// increment the clock sequence62if now <= lasttime {63clockSeq = ((clockSeq + 1) & 0x3fff) | 0x800064}65lasttime = now66return Time(now), clockSeq, nil67}
68
69// ClockSequence returns the current clock sequence, generating one if not
70// already set. The clock sequence is only used for Version 1 UUIDs.
71//
72// The uuid package does not use global static storage for the clock sequence or
73// the last time a UUID was generated. Unless SetClockSequence is used, a new
74// random clock sequence is generated the first time a clock sequence is
75// requested by ClockSequence, GetTime, or NewUUID. (section 4.2.1.1)
76func ClockSequence() int {77defer timeMu.Unlock()78timeMu.Lock()79return clockSequence()80}
81
82func clockSequence() int {83if clockSeq == 0 {84setClockSequence(-1)85}86return int(clockSeq & 0x3fff)87}
88
89// SetClockSequence sets the clock sequence to the lower 14 bits of seq. Setting to
90// -1 causes a new sequence to be generated.
91func SetClockSequence(seq int) {92defer timeMu.Unlock()93timeMu.Lock()94setClockSequence(seq)95}
96
97func setClockSequence(seq int) {98if seq == -1 {99var b [2]byte100randomBits(b[:]) // clock sequence101seq = int(b[0])<<8 | int(b[1])102}103oldSeq := clockSeq104clockSeq = uint16(seq&0x3fff) | 0x8000 // Set our variant105if oldSeq != clockSeq {106lasttime = 0107}108}
109
110// Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in
111// uuid. The time is only defined for version 1 and 2 UUIDs.
112func (uuid UUID) Time() Time {113time := int64(binary.BigEndian.Uint32(uuid[0:4]))114time |= int64(binary.BigEndian.Uint16(uuid[4:6])) << 32115time |= int64(binary.BigEndian.Uint16(uuid[6:8])&0xfff) << 48116return Time(time)117}
118
119// ClockSequence returns the clock sequence encoded in uuid.
120// The clock sequence is only well defined for version 1 and 2 UUIDs.
121func (uuid UUID) ClockSequence() int {122return int(binary.BigEndian.Uint16(uuid[8:10])) & 0x3fff123}
124