github.com/inflatablewoman/deis@v1.0.1-0.20141111034523-a4511c46a6ce/deisctl/Godeps/_workspace/src/code.google.com/p/go-uuid/uuid/time.go (about)

     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.
     4  
     5  package uuid
     6  
     7  import (
     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.
    15  type Time int64
    16  
    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  )
    24  
    25  var (
    26  	mu        sync.Mutex
    27  	lasttime  uint64 // last time we returned
    28  	clock_seq 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.
    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  }
    41  
    42  // GetTime returns the current Time (100s of nanoseconds since 15 Oct 1582) and
    43  // adjusts the clock sequence as needed.  An error is returned if the current
    44  // time cannot be determined.
    45  func GetTime() (Time, error) {
    46  	defer mu.Unlock()
    47  	mu.Lock()
    48  	return getTime()
    49  }
    50  
    51  func getTime() (Time, error) {
    52  	t := timeNow()
    53  
    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
    59  
    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), 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 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  }
    82  
    83  func clockSequence() int {
    84  	if clock_seq == 0 {
    85  		setClockSequence(-1)
    86  	}
    87  	return int(clock_seq & 0x3fff)
    88  }
    89  
    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  }
    97  
    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  }
   110  
   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  }
   123  
   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  }