summaryrefslogtreecommitdiff
path: root/mysys/my_uuid.c
blob: f167ebe1d6e98572ad00a3af47841854f358d73d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
/* Copyright (C) 2007 MySQL AB, Sergei Golubchik & Michael Widenius

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */

/*
  implements Universal Unique Identifiers (UUIDs), as in
    DCE 1.1: Remote Procedure Call,
    Open Group Technical Standard Document Number C706, October 1997,
    (supersedes C309 DCE: Remote Procedure Call 8/1994,
    which was basis for ISO/IEC 11578:1996 specification)

  A UUID has the following structure:

  Field                     NDR Data Type  Octet #          Note
 time_low                   unsigned long    0-3     The low field of the
                                                     timestamp.
 time_mid                   unsigned short   4-5     The middle field of
                                                     the timestamp.
 time_hi_and_version        unsigned short   6-7     The high field of the
                                                     timestamp multiplexed
                                                     with the version number.
 clock_seq_hi_and_reserved  unsigned small   8       The high field of the
                                                     clock sequence multi-
                                                     plexed with the variant.
 clock_seq_low              unsigned small   9       The low field of the
                                                     clock sequence.
 node                       character        10-15   The spatially unique node
                                                     identifier.
*/

#include "mysys_priv.h"
#include <my_rnd.h>
#include <m_string.h>
#include <myisampack.h> /* mi_int2store, mi_int4store */

static my_bool my_uuid_inited= 0;
static struct my_rnd_struct uuid_rand;
static uint nanoseq;
static ulonglong uuid_time= 0;
static longlong interval_timer_offset;
static uchar uuid_suffix[2+6]; /* clock_seq and node */

static mysql_mutex_t LOCK_uuid_generator;

/*
  Number of 100-nanosecond intervals between
  1582-10-15 00:00:00.00 and 1970-01-01 00:00:00.00
*/

#define UUID_TIME_OFFSET ((ulonglong) 141427 * 24 * 60 * 60 * \
                          1000 * 1000 * 10)
#define UUID_VERSION      0x1000
#define UUID_VARIANT      0x8000


/* Helper function */

static void set_clock_seq()
{
  uint16 clock_seq= ((uint)(my_rnd(&uuid_rand)*16383)) | UUID_VARIANT;
  mi_int2store(uuid_suffix, clock_seq);
  interval_timer_offset= (my_hrtime().val * 10 - my_interval_timer()/100 + 
                          UUID_TIME_OFFSET);
}


/**
  Init structures needed for my_uuid

  @func my_uuid_init()
  @param seed1		Seed for random generator
  @param seed2		Seed for random generator

  @note
    Seed1 & seed2 should NOT depend on clock. This is to be able to
    generate a random mac address according to UUID specs.
*/

void my_uuid_init(ulong seed1, ulong seed2)
{
  uchar *mac= uuid_suffix+2;
  ulonglong now;

  if (my_uuid_inited)
    return;
  my_uuid_inited= 1;
  now= my_interval_timer()/100 + interval_timer_offset;
  nanoseq= 0;

  if (my_gethwaddr(mac))
  {
    uint i;
    /*
      Generating random "hardware addr"

      Specs explicitly specify that node identifier should NOT
      correlate with a clock_seq value, so we use a separate
      randominit() here.
    */
    /* purecov: begin inspected */
    my_rnd_init(&uuid_rand, (ulong) (seed2+ now/2), (ulong) (now+rand()));
    for (i=0; i < array_elements(uuid_suffix) -2 ; i++)
      mac[i]= (uchar)(my_rnd(&uuid_rand)*255);
    /* purecov: end */
  }
  my_rnd_init(&uuid_rand, (ulong) (seed1 + now), (ulong) (now/2+ getpid()));
  set_clock_seq();
  mysql_mutex_init(key_LOCK_uuid_generator, &LOCK_uuid_generator, MY_MUTEX_INIT_FAST);
}


/**
   Create a global unique identifier (uuid)

   @func  my_uuid()
   @param to   Store uuid here. Must be of size MY_UUID_SIZE (16)
*/

void my_uuid(uchar *to)
{
  ulonglong tv;
  uint32 time_low;
  uint16 time_mid, time_hi_and_version;

  DBUG_ASSERT(my_uuid_inited);

  mysql_mutex_lock(&LOCK_uuid_generator);
  tv= my_interval_timer()/100 + interval_timer_offset + nanoseq;

  if (likely(tv > uuid_time))
  {
    /*
      Current time is ahead of last timestamp, as it should be.
      If we "borrowed time", give it back, just as long as we
      stay ahead of the previous timestamp.
    */
    if (nanoseq)
    {
      ulong delta;
      DBUG_ASSERT((tv > uuid_time) && (nanoseq > 0));
      /*
        -1 so we won't make tv= uuid_time for nanoseq >= (tv - uuid_time)
      */
      delta= MY_MIN(nanoseq, (ulong)(tv - uuid_time -1));
      tv-= delta;
      nanoseq-= delta;
    }
  }
  else
  {
    if (unlikely(tv == uuid_time))
    {
      /*
        For low-res system clocks. If several requests for UUIDs
        end up on the same tick, we add a nano-second to make them
        different.
        ( current_timestamp + nanoseq * calls_in_this_period )
        may end up > next_timestamp; this is OK. Nonetheless, we'll
        try to unwind nanoseq when we get a chance to.
        If nanoseq overflows, we'll start over with a new numberspace
        (so the if() below is needed so we can avoid the ++tv and thus
        match the follow-up if() if nanoseq overflows!).
      */
      if (likely(++nanoseq))
        ++tv;
    }

    if (unlikely(tv <= uuid_time))
    {
      /*
        If the admin changes the system clock (or due to Daylight
        Saving Time), the system clock may be turned *back* so we
        go through a period once more for which we already gave out
        UUIDs.  To avoid duplicate UUIDs despite potentially identical
        times, we make a new random component.
        We also come here if the nanoseq "borrowing" overflows.
        In either case, we throw away any nanoseq borrowing since it's
        irrelevant in the new numberspace.
      */
      set_clock_seq();
      tv= my_interval_timer()/100 + interval_timer_offset;
      nanoseq= 0;
      DBUG_PRINT("uuid",("making new numberspace"));
    }
  }

  uuid_time=tv;
  mysql_mutex_unlock(&LOCK_uuid_generator);

  time_low=            (uint32) (tv & 0xFFFFFFFF);
  time_mid=            (uint16) ((tv >> 32) & 0xFFFF);
  time_hi_and_version= (uint16) ((tv >> 48) | UUID_VERSION);

  /*
    Note, that the standard does NOT specify byte ordering in
    multi-byte fields. it's implementation defined (but must be
    the same for all fields).
    We use big-endian, so we can use memcmp() to compare UUIDs
    and for straightforward UUID to string conversion.
  */
  mi_int4store(to, time_low);
  mi_int2store(to+4, time_mid);
  mi_int2store(to+6, time_hi_and_version);
  bmove(to+8, uuid_suffix, sizeof(uuid_suffix));
}


/**
   Convert uuid to string representation

   @func  my_uuid2str()
   @param guid uuid
   @param s    Output buffer.Must be at least MY_UUID_STRING_LENGTH+1 large.
*/
void my_uuid2str(const uchar *guid, char *s)
{
  int i;
  for (i=0; i < MY_UUID_SIZE; i++)
  {
    *s++= _dig_vec_lower[guid[i] >>4];
    *s++= _dig_vec_lower[guid[i] & 15];
    /* Set '-' at intervals 3, 5, 7 and 9 */
    if ((1 << i) & ((1 << 3) | (1 << 5) | (1 << 7) | (1 << 9)))
      *s++= '-';
  }
}

void my_uuid_end()
{
  if (my_uuid_inited)
  {
    my_uuid_inited= 0;
    mysql_mutex_destroy(&LOCK_uuid_generator);
  }
}