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 uuid 6 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 int64 16 17const ( 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) 24 25var ( 26 timeMu sync.Mutex 27 lasttime uint64 // last time we returned 28 clockSeq uint16 // clock sequence for this run 29 30 timeNow = time.Now // for testing 31) 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) { 36 sec = int64(t - g1582ns100) 37 nsec = (sec % 10000000) * 100 38 sec /= 10000000 39 return sec, nsec 40} 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) { 46 defer timeMu.Unlock() 47 timeMu.Lock() 48 return getTime() 49} 50 51func getTime() (Time, uint16, error) { 52 t := timeNow() 53 54 // If we don't have a clock sequence already, set one. 55 if clockSeq == 0 { 56 setClockSequence(-1) 57 } 58 now := uint64(t.UnixNano()/100) + g1582ns100 59 60 // If time has gone backwards with this clock sequence then we 61 // increment the clock sequence 62 if now <= lasttime { 63 clockSeq = ((clockSeq + 1) & 0x3fff) | 0x8000 64 } 65 lasttime = now 66 return Time(now), clockSeq, nil 67} 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 { 77 defer timeMu.Unlock() 78 timeMu.Lock() 79 return clockSequence() 80} 81 82func clockSequence() int { 83 if clockSeq == 0 { 84 setClockSequence(-1) 85 } 86 return 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) { 92 defer timeMu.Unlock() 93 timeMu.Lock() 94 setClockSequence(seq) 95} 96 97func setClockSequence(seq int) { 98 if seq == -1 { 99 var b [2]byte 100 randomBits(b[:]) // clock sequence 101 seq = int(b[0])<<8 | int(b[1]) 102 } 103 oldSeq := clockSeq 104 clockSeq = uint16(seq&0x3fff) | 0x8000 // Set our variant 105 if oldSeq != clockSeq { 106 lasttime = 0 107 } 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 { 113 time := int64(binary.BigEndian.Uint32(uuid[0:4])) 114 time |= int64(binary.BigEndian.Uint16(uuid[4:6])) << 32 115 time |= int64(binary.BigEndian.Uint16(uuid[6:8])&0xfff) << 48 116 return 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 { 122 return int(binary.BigEndian.Uint16(uuid[8:10])) & 0x3fff 123} 124