ducky/devices
2015-11-12
ducky/devices/vendor/code.google.com/p/go-uuid/uuid/time.go
Initial attempt. Create the basic types (Device, DeviceType, DeviceChange) that we'll be using in the service. Also, create our Storer interface, and the helper methods to store, retrieve, and update information in the datastore. Also, we're using Godep, so check in our Godeps folder and the vendor folder. Note that this only works on Go 1.5 and later, with the GO15VENDOREXPERIMENT environment variable set to 1.
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 }