ducky/devices
2015-11-15
Parent:b6494e1a499e
ducky/devices/vendor/code.google.com/p/go-uuid/uuid/time.go
Add ToMap and ToSlice helpers. Add helper functions that convert a map of ID-keyed Devices into a slice, and back. We'll use these a lot (especially with GetMany) as shorthand helper functions.
1 // Copyright 2014 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.
5 package uuid
7 import (
8 "encoding/binary"
9 "sync"
10 "time"
11 )
13 // A Time represents a time as the number of 100's of nanoseconds since 15 Oct
14 // 1582.
15 type Time int64
17 const (
18 lillian = 2299160 // Julian day of 15 Oct 1582
19 unix = 2440587 // Julian day of 1 Jan 1970
20 epoch = unix - lillian // Days between epochs
21 g1582 = epoch * 86400 // seconds between epochs
22 g1582ns100 = g1582 * 10000000 // 100s of a nanoseconds between epochs
23 )
25 var (
26 mu sync.Mutex
27 lasttime uint64 // last time we returned
28 clock_seq uint16 // clock sequence for this run
30 timeNow = time.Now // for testing
31 )
33 // UnixTime converts t the number of seconds and nanoseconds using the Unix
34 // epoch of 1 Jan 1970.
35 func (t Time) UnixTime() (sec, nsec int64) {
36 sec = int64(t - g1582ns100)
37 nsec = (sec % 10000000) * 100
38 sec /= 10000000
39 return sec, nsec
40 }
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.
45 func GetTime() (Time, uint16, error) {
46 defer mu.Unlock()
47 mu.Lock()
48 return getTime()
49 }
51 func getTime() (Time, uint16, error) {
52 t := timeNow()
54 // If we don't have a clock sequence already, set one.
55 if clock_seq == 0 {
56 setClockSequence(-1)
57 }
58 now := uint64(t.UnixNano()/100) + g1582ns100
60 // If time has gone backwards with this clock sequence then we
61 // increment the clock sequence
62 if now <= lasttime {
63 clock_seq = ((clock_seq + 1) & 0x3fff) | 0x8000
64 }
65 lasttime = now
66 return Time(now), clock_seq, nil
67 }
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 a new random
74 // clock sequence is generated the first time a clock sequence is requested by
75 // ClockSequence, GetTime, or NewUUID. (section 4.2.1.1) sequence is generated
76 // for
77 func ClockSequence() int {
78 defer mu.Unlock()
79 mu.Lock()
80 return clockSequence()
81 }
83 func clockSequence() int {
84 if clock_seq == 0 {
85 setClockSequence(-1)
86 }
87 return int(clock_seq & 0x3fff)
88 }
90 // SetClockSeq sets the clock sequence to the lower 14 bits of seq. Setting to
91 // -1 causes a new sequence to be generated.
92 func SetClockSequence(seq int) {
93 defer mu.Unlock()
94 mu.Lock()
95 setClockSequence(seq)
96 }
98 func setClockSequence(seq int) {
99 if seq == -1 {
100 var b [2]byte
101 randomBits(b[:]) // clock sequence
102 seq = int(b[0])<<8 | int(b[1])
103 }
104 old_seq := clock_seq
105 clock_seq = uint16(seq&0x3fff) | 0x8000 // Set our variant
106 if old_seq != clock_seq {
107 lasttime = 0
108 }
109 }
111 // Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in
112 // uuid. It returns false if uuid is not valid. The time is only well defined
113 // for version 1 and 2 UUIDs.
114 func (uuid UUID) Time() (Time, bool) {
115 if len(uuid) != 16 {
116 return 0, false
117 }
118 time := int64(binary.BigEndian.Uint32(uuid[0:4]))
119 time |= int64(binary.BigEndian.Uint16(uuid[4:6])) << 32
120 time |= int64(binary.BigEndian.Uint16(uuid[6:8])&0xfff) << 48
121 return Time(time), true
122 }
124 // ClockSequence returns the clock sequence encoded in uuid. It returns false
125 // if uuid is not valid. The clock sequence is only well defined for version 1
126 // and 2 UUIDs.
127 func (uuid UUID) ClockSequence() (int, bool) {
128 if len(uuid) != 16 {
129 return 0, false
130 }
131 return int(binary.BigEndian.Uint16(uuid[8:10])) & 0x3fff, true
132 }