summaryrefslogtreecommitdiffstats
path: root/vendor/github.com/pborman/uuid/time.go
blob: eedf242194b2cfd1b8e3e9c5e43e09d4eb2cd0a7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
// Copyright 2014 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"
	"sync"
	"time"
)

// A Time represents a time as the number of 100's of nanoseconds since 15 Oct
// 1582.
type Time int64

const (
	lillian    = 2299160          // Julian day of 15 Oct 1582
	unix       = 2440587          // Julian day of 1 Jan 1970
	epoch      = unix - lillian   // Days between epochs
	g1582      = epoch * 86400    // seconds between epochs
	g1582ns100 = g1582 * 10000000 // 100s of a nanoseconds between epochs
)

var (
	timeMu    sync.Mutex
	lasttime  uint64 // last time we returned
	clock_seq uint16 // clock sequence for this run

	timeNow = time.Now // for testing
)

// UnixTime converts t the number of seconds and nanoseconds using the Unix
// epoch of 1 Jan 1970.
func (t Time) UnixTime() (sec, nsec int64) {
	sec = int64(t - g1582ns100)
	nsec = (sec % 10000000) * 100
	sec /= 10000000
	return sec, nsec
}

// GetTime returns the current Time (100s of nanoseconds since 15 Oct 1582) and
// clock sequence as well as adjusting the clock sequence as needed.  An error
// is returned if the current time cannot be determined.
func GetTime() (Time, uint16, error) {
	defer timeMu.Unlock()
	timeMu.Lock()
	return getTime()
}

func getTime() (Time, uint16, error) {
	t := timeNow()

	// If we don't have a clock sequence already, set one.
	if clock_seq == 0 {
		setClockSequence(-1)
	}
	now := uint64(t.UnixNano()/100) + g1582ns100

	// If time has gone backwards with this clock sequence then we
	// increment the clock sequence
	if now <= lasttime {
		clock_seq = ((clock_seq + 1) & 0x3fff) | 0x8000
	}
	lasttime = now
	return Time(now), clock_seq, nil
}

// ClockSequence returns the current clock sequence, generating one if not
// already set.  The clock sequence is only used for Version 1 UUIDs.
//
// The uuid package does not use global static storage for the clock sequence or
// the last time a UUID was generated.  Unless SetClockSequence a new random
// clock sequence is generated the first time a clock sequence is requested by
// ClockSequence, GetTime, or NewUUID.  (section 4.2.1.1) sequence is generated
// for
func ClockSequence() int {
	defer timeMu.Unlock()
	timeMu.Lock()
	return clockSequence()
}

func clockSequence() int {
	if clock_seq == 0 {
		setClockSequence(-1)
	}
	return int(clock_seq & 0x3fff)
}

// SetClockSeq sets the clock sequence to the lower 14 bits of seq.  Setting to
// -1 causes a new sequence to be generated.
func SetClockSequence(seq int) {
	defer timeMu.Unlock()
	timeMu.Lock()
	setClockSequence(seq)
}

func setClockSequence(seq int) {
	if seq == -1 {
		var b [2]byte
		randomBits(b[:]) // clock sequence
		seq = int(b[0])<<8 | int(b[1])
	}
	old_seq := clock_seq
	clock_seq = uint16(seq&0x3fff) | 0x8000 // Set our variant
	if old_seq != clock_seq {
		lasttime = 0
	}
}

// Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in
// uuid.  It returns false if uuid is not valid.  The time is only well defined
// for version 1 and 2 UUIDs.
func (uuid UUID) Time() (Time, bool) {
	if len(uuid) != 16 {
		return 0, false
	}
	time := int64(binary.BigEndian.Uint32(uuid[0:4]))
	time |= int64(binary.BigEndian.Uint16(uuid[4:6])) << 32
	time |= int64(binary.BigEndian.Uint16(uuid[6:8])&0xfff) << 48
	return Time(time), true
}

// ClockSequence returns the clock sequence encoded in uuid.  It returns false
// if uuid is not valid.  The clock sequence is only well defined for version 1
// and 2 UUIDs.
func (uuid UUID) ClockSequence() (int, bool) {
	if len(uuid) != 16 {
		return 0, false
	}
	return int(binary.BigEndian.Uint16(uuid[8:10])) & 0x3fff, true
}