--- /dev/null
+// 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
+}
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