summaryrefslogtreecommitdiff
path: root/src/util/time.c
blob: c1ad5e6185af6d579fb1b779df4809160be664aa (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
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
/*
     This file is part of GNUnet.
     Copyright (C) 2001-2013, 2018 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet 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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file util/time.c
 * @author Christian Grothoff
 * @brief functions for handling time and time arithmetic
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#if __STDC_NO_ATOMICS__
#define ATOMIC
#else
#ifdef HAVE_STDATOMIC_H
#include <stdatomic.h>
#define ATOMIC _Atomic
#else
#define __STDC_NO_ATOMICS__ 1
#define ATOMIC
#endif
#endif

#define LOG(kind, ...) GNUNET_log_from (kind, "util-time", __VA_ARGS__)

/**
 * Variable used to simulate clock skew.  Used for testing, never in production.
 */
static long long timestamp_offset;

/**
 * Set the timestamp offset for this instance.
 *
 * @param offset the offset to skew the locale time by
 */
void
GNUNET_TIME_set_offset (long long offset)
{
  timestamp_offset = offset;
}


/**
 * Get the timestamp offset for this instance.
 *
 * @return the offset we currently skew the locale time by
 */
long long
GNUNET_TIME_get_offset ()
{
  return timestamp_offset;
}


/**
 * Round a time value so that it is suitable for transmission
 * via JSON encodings.
 *
 * @param at time to round
 * @return #GNUNET_OK if time was already rounded, #GNUNET_NO if
 *         it was just now rounded
 */
int
GNUNET_TIME_round_abs (struct GNUNET_TIME_Absolute *at)
{
  if (at->abs_value_us == GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us)
    return GNUNET_OK;
  if (0 == at->abs_value_us % 1000000)
    return GNUNET_OK;
  at->abs_value_us -= at->abs_value_us % 1000000;
  return GNUNET_NO;
}


/**
 * Round a time value so that it is suitable for transmission
 * via JSON encodings.
 *
 * @param rt time to round
 * @return #GNUNET_OK if time was already rounded, #GNUNET_NO if
 *         it was just now rounded
 */
int
GNUNET_TIME_round_rel (struct GNUNET_TIME_Relative *rt)
{
  if (rt->rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_OK;
  if (0 == rt->rel_value_us % 1000000)
    return GNUNET_OK;
  rt->rel_value_us -= rt->rel_value_us % 1000000;
  return GNUNET_NO;
}


/**
 * Get the current time (works just as "time", just that we use the
 * unit of time that the cron-jobs use (and is 64 bit)).
 *
 * @return the current time
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get ()
{
  struct GNUNET_TIME_Absolute ret;
  struct timeval tv;

  gettimeofday (&tv, NULL);
  ret.abs_value_us = (uint64_t) (((uint64_t) tv.tv_sec * 1000LL * 1000LL)
                                 + ((uint64_t) tv.tv_usec))
                     + timestamp_offset;
  return ret;
}


/**
 * Return relative time of 0ms.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_zero_ ()
{
  static struct GNUNET_TIME_Relative zero;

  return zero;
}


/**
 * Return absolute time of 0ms.
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_zero_ ()
{
  static struct GNUNET_TIME_Absolute zero;

  return zero;
}


/**
 * Return relative time of 1us.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_unit_ ()
{
  static struct GNUNET_TIME_Relative one = { 1 };

  return one;
}


/**
 * Return relative time of 1ms.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_millisecond_ ()
{
  static struct GNUNET_TIME_Relative one = { 1000 };

  return one;
}


/**
 * Return relative time of 1s.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_second_ ()
{
  static struct GNUNET_TIME_Relative one = { 1000 * 1000LL };

  return one;
}


/**
 * Return relative time of 1 minute.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_minute_ ()
{
  static struct GNUNET_TIME_Relative one = { 60 * 1000 * 1000LL };

  return one;
}


/**
 * Return relative time of 1 hour.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_hour_ ()
{
  static struct GNUNET_TIME_Relative one = { 60 * 60 * 1000 * 1000LL };

  return one;
}


/**
 * Return "forever".
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_forever_ ()
{
  static struct GNUNET_TIME_Relative forever = { UINT64_MAX };

  return forever;
}


/**
 * Return "forever".
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_forever_ ()
{
  static struct GNUNET_TIME_Absolute forever = { UINT64_MAX };

  return forever;
}


/**
 * Convert relative time to an absolute time in the
 * future.
 *
 * @return timestamp that is "rel" in the future, or FOREVER if rel==FOREVER (or if we would overflow)
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_relative_to_absolute (struct GNUNET_TIME_Relative rel)
{
  struct GNUNET_TIME_Absolute ret;

  if (rel.rel_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  struct GNUNET_TIME_Absolute now = GNUNET_TIME_absolute_get ();

  if (rel.rel_value_us + now.abs_value_us < rel.rel_value_us)
  {
    GNUNET_break (0);  /* overflow... */
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  }
  ret.abs_value_us = rel.rel_value_us + now.abs_value_us;
  return ret;
}


/**
 * Return the minimum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is smaller
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_min (struct GNUNET_TIME_Relative t1,
                          struct GNUNET_TIME_Relative t2)
{
  return (t1.rel_value_us < t2.rel_value_us) ? t1 : t2;
}


/**
 * Return the maximum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is larger
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_max (struct GNUNET_TIME_Relative t1,
                          struct GNUNET_TIME_Relative t2)
{
  return (t1.rel_value_us > t2.rel_value_us) ? t1 : t2;
}


/**
 * Return the minimum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is smaller
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_min (struct GNUNET_TIME_Absolute t1,
                          struct GNUNET_TIME_Absolute t2)
{
  return (t1.abs_value_us < t2.abs_value_us) ? t1 : t2;
}


/**
 * Return the maximum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is bigger
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_max (struct GNUNET_TIME_Absolute t1,
                          struct GNUNET_TIME_Absolute t2)
{
  return (t1.abs_value_us > t2.abs_value_us) ? t1 : t2;
}


/**
 * Given a timestamp in the future, how much time
 * remains until then?
 *
 * @return future - now, or 0 if now >= future, or FOREVER if future==FOREVER.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_remaining (struct GNUNET_TIME_Absolute future)
{
  struct GNUNET_TIME_Relative ret;

  if (future.abs_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  struct GNUNET_TIME_Absolute now = GNUNET_TIME_absolute_get ();

  if (now.abs_value_us > future.abs_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  ret.rel_value_us = future.abs_value_us - now.abs_value_us;
  return ret;
}


/**
 * Compute the time difference between the given start and end times.
 * Use this function instead of actual subtraction to ensure that
 * "FOREVER" and overflows are handled correctly.
 *
 * @return 0 if start >= end; FOREVER if end==FOREVER; otherwise end - start
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_difference (struct GNUNET_TIME_Absolute start,
                                     struct GNUNET_TIME_Absolute end)
{
  struct GNUNET_TIME_Relative ret;

  if (end.abs_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  if (end.abs_value_us < start.abs_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  ret.rel_value_us = end.abs_value_us - start.abs_value_us;
  return ret;
}


/**
 * Get the duration of an operation as the
 * difference of the current time and the given start time "whence".
 *
 * @return 0 if whence > now, otherwise now-whence.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_duration (struct GNUNET_TIME_Absolute whence)
{
  struct GNUNET_TIME_Absolute now;
  struct GNUNET_TIME_Relative ret;

  now = GNUNET_TIME_absolute_get ();
  if (whence.abs_value_us > now.abs_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  ret.rel_value_us = now.abs_value_us - whence.abs_value_us;
  return ret;
}


/**
 * Add a given relative duration to the
 * given start time.
 *
 * @return FOREVER if either argument is FOREVER or on overflow; start+duration otherwise
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_add (struct GNUNET_TIME_Absolute start,
                          struct GNUNET_TIME_Relative duration)
{
  struct GNUNET_TIME_Absolute ret;

  if ((start.abs_value_us == UINT64_MAX) ||
      (duration.rel_value_us == UINT64_MAX))
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  if (start.abs_value_us + duration.rel_value_us < start.abs_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  }
  ret.abs_value_us = start.abs_value_us + duration.rel_value_us;
  return ret;
}


/**
 * Subtract a given relative duration from the
 * given start time.
 *
 * @param start some absolute time
 * @param duration some relative time to subtract
 * @return ZERO if start <= duration, or FOREVER if start time is FOREVER; start-duration otherwise
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_subtract (struct GNUNET_TIME_Absolute start,
                               struct GNUNET_TIME_Relative duration)
{
  struct GNUNET_TIME_Absolute ret;

  if (start.abs_value_us <= duration.rel_value_us)
    return GNUNET_TIME_UNIT_ZERO_ABS;
  if (start.abs_value_us == GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us)
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  ret.abs_value_us = start.abs_value_us - duration.rel_value_us;
  return ret;
}


/**
 * Multiply relative time by a given factor.
 *
 * @return FOREVER if rel=FOREVER or on overflow; otherwise rel*factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_multiply (struct GNUNET_TIME_Relative rel,
                               unsigned long long factor)
{
  struct GNUNET_TIME_Relative ret;

  if (0 == factor)
    return GNUNET_TIME_UNIT_ZERO;
  if (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = rel.rel_value_us * factor;
  if (ret.rel_value_us / factor != rel.rel_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }
  return ret;
}


/**
 * Multiply relative time by a given floating-point factor.  The factor must be
 * positive.
 *
 * @return FOREVER if rel=FOREVER or on overflow; otherwise rel*factor
 */
struct GNUNET_TIME_Relative
relative_multiply_double (struct GNUNET_TIME_Relative rel, double factor)
{
  struct GNUNET_TIME_Relative out;
  double m;

  GNUNET_assert (0 <= factor);

  if (0 == factor)
    return GNUNET_TIME_UNIT_ZERO;
  if (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_TIME_UNIT_FOREVER_REL;

  m = ((double) rel.rel_value_us) * factor;

  if (m >= (double) (GNUNET_TIME_UNIT_FOREVER_REL).rel_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }

  out.rel_value_us = (uint64_t) m;
  return out;
}


/**
 * Saturating multiply relative time by a given factor.
 *
 * @param rel some duration
 * @param factor integer to multiply with
 * @return FOREVER if rel=FOREVER or on overflow; otherwise rel*factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_saturating_multiply (struct GNUNET_TIME_Relative rel,
                                          unsigned long long factor)
{
  struct GNUNET_TIME_Relative ret;

  if (0 == factor)
    return GNUNET_TIME_UNIT_ZERO;
  if (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = rel.rel_value_us * factor;
  if (ret.rel_value_us / factor != rel.rel_value_us)
  {
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }
  return ret;
}


/**
 * Divide relative time by a given factor.
 *
 * @param rel some duration
 * @param factor integer to divide by
 * @return FOREVER if rel=FOREVER or factor==0; otherwise rel/factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_divide (struct GNUNET_TIME_Relative rel,
                             unsigned long long factor)
{
  struct GNUNET_TIME_Relative ret;

  if ((0 == factor) ||
      (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us))
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = rel.rel_value_us / factor;
  return ret;
}


/**
 * Calculate the estimate time of arrival/completion
 * for an operation.
 *
 * @param start when did the operation start?
 * @param finished how much has been done?
 * @param total how much must be done overall (same unit as for "finished")
 * @return remaining duration for the operation,
 *        assuming it continues at the same speed
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_calculate_eta (struct GNUNET_TIME_Absolute start,
                           uint64_t finished,
                           uint64_t total)
{
  struct GNUNET_TIME_Relative due;
  double exp;
  struct GNUNET_TIME_Relative ret;

  GNUNET_break (finished <= total);
  if (finished >= total)
    return GNUNET_TIME_UNIT_ZERO;
  if (0 == finished)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  due = GNUNET_TIME_absolute_get_duration (start);
  exp = ((double) due.rel_value_us) * ((double) total) / ((double) finished);
  ret.rel_value_us = ((uint64_t) exp) - due.rel_value_us;
  return ret;
}


/**
 * Add relative times together.
 *
 * @param a1 first timestamp
 * @param a2 second timestamp
 * @return FOREVER if either argument is FOREVER or on overflow; a1+a2 otherwise
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_add (struct GNUNET_TIME_Relative a1,
                          struct GNUNET_TIME_Relative a2)
{
  struct GNUNET_TIME_Relative ret;

  if ((a1.rel_value_us == UINT64_MAX) || (a2.rel_value_us == UINT64_MAX))
    return GNUNET_TIME_UNIT_FOREVER_REL;
  if (a1.rel_value_us + a2.rel_value_us < a1.rel_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }
  ret.rel_value_us = a1.rel_value_us + a2.rel_value_us;
  return ret;
}


/**
 * Subtract relative timestamp from the other.
 *
 * @param a1 first timestamp
 * @param a2 second timestamp
 * @return ZERO if a2>=a1 (including both FOREVER), FOREVER if a1 is FOREVER, a1-a2 otherwise
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_subtract (struct GNUNET_TIME_Relative a1,
                               struct GNUNET_TIME_Relative a2)
{
  struct GNUNET_TIME_Relative ret;

  if (a2.rel_value_us >= a1.rel_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  if (a1.rel_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = a1.rel_value_us - a2.rel_value_us;
  return ret;
}


/**
 * Convert relative time to network byte order.
 *
 * @param a time to convert
 * @return time in network byte order
 */
struct GNUNET_TIME_RelativeNBO
GNUNET_TIME_relative_hton (struct GNUNET_TIME_Relative a)
{
  struct GNUNET_TIME_RelativeNBO ret;

  ret.rel_value_us__ = GNUNET_htonll (a.rel_value_us);
  return ret;
}


/**
 * Convert relative time from network byte order.
 *
 * @param a time to convert
 * @return time in host byte order
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_ntoh (struct GNUNET_TIME_RelativeNBO a)
{
  struct GNUNET_TIME_Relative ret;

  ret.rel_value_us = GNUNET_ntohll (a.rel_value_us__);
  return ret;
}


/**
 * Convert absolute time to network byte order.
 *
 * @param a time to convert
 * @return time in network byte order
 */
struct GNUNET_TIME_AbsoluteNBO
GNUNET_TIME_absolute_hton (struct GNUNET_TIME_Absolute a)
{
  struct GNUNET_TIME_AbsoluteNBO ret;

  ret.abs_value_us__ = GNUNET_htonll (a.abs_value_us);
  return ret;
}


/**
 * Convert absolute time from network byte order.
 *
 * @param a time to convert
 * @return time in host byte order
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_ntoh (struct GNUNET_TIME_AbsoluteNBO a)
{
  struct GNUNET_TIME_Absolute ret;

  ret.abs_value_us = GNUNET_ntohll (a.abs_value_us__);
  return ret;
}


/**
 * Return the current year (i.e. '2011').
 */
unsigned int
GNUNET_TIME_get_current_year ()
{
  time_t tp;
  struct tm *t;

  tp = time (NULL);
  t = gmtime (&tp);
  if (t == NULL)
    return 0;
  return t->tm_year + 1900;
}


/**
 * Convert an expiration time to the respective year (rounds)
 *
 * @param at absolute time
 * @return year a year (after 1970), 0 on error
 */
unsigned int
GNUNET_TIME_time_to_year (struct GNUNET_TIME_Absolute at)
{
  struct tm *t;
  time_t tp;

  tp = at.abs_value_us / 1000LL / 1000LL; /* microseconds to seconds */
  t = gmtime (&tp);
  if (t == NULL)
    return 0;
  return t->tm_year + 1900;
}


#ifndef HAVE_TIMEGM
/**
 * As suggested in the timegm() man page.
 */
static time_t
my_timegm (struct tm *tm)
{
  time_t ret;
  char *tz;

  tz = getenv ("TZ");
  setenv ("TZ", "", 1);
  tzset ();
  ret = mktime (tm);
  if (tz)
    setenv ("TZ", tz, 1);
  else
    unsetenv ("TZ");
  tzset ();
  return ret;
}


#endif


/**
 * Convert a year to an expiration time of January 1st of that year.
 *
 * @param year a year (after 1970, please ;-)).
 * @return absolute time for January 1st of that year.
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_year_to_time (unsigned int year)
{
  struct GNUNET_TIME_Absolute ret;
  time_t tp;
  struct tm t;

  memset (&t, 0, sizeof(t));
  if (year < 1900)
  {
    GNUNET_break (0);
    return GNUNET_TIME_absolute_get ();  /* now */
  }
  t.tm_year = year - 1900;
  t.tm_mday = 1;
  t.tm_mon = 0;
  t.tm_wday = 1;
  t.tm_yday = 1;
#ifndef HAVE_TIMEGM
  tp = my_timegm (&t);
#else
  tp = timegm (&t);
#endif
  GNUNET_break (tp != (time_t) -1);
  ret.abs_value_us = tp * 1000LL * 1000LL; /* seconds to microseconds */
  return ret;
}


/**
 * Randomized exponential back-off, starting at 1 ms
 * and going up by a factor of 2+r, where 0 <= r < 0.5, up
 * to a maximum of the given threshold.
 *
 * @param r current backoff time, initially zero
 * @param threshold maximum value for backoff
 * @return the next backoff time
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_randomized_backoff (struct GNUNET_TIME_Relative rt,
                                struct GNUNET_TIME_Relative threshold)
{
  double r = (rand () % 500) / 1000.0;
  struct GNUNET_TIME_Relative t;

  t = relative_multiply_double (
    GNUNET_TIME_relative_max (GNUNET_TIME_UNIT_MILLISECONDS, rt),
    2 + r);
  return GNUNET_TIME_relative_min (threshold, t);
}


/**
 * Return a random time value between 0.5*r and 1.5*r.
 *
 * @param r input time for scaling
 * @return randomized time
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_randomize (struct GNUNET_TIME_Relative r)
{
  double d = ((rand () % 1001) + 500) / 1000.0;

  return relative_multiply_double (r, d);
}


/**
 * Obtain the current time and make sure it is monotonically
 * increasing.  Guards against systems without an RTC or
 * clocks running backwards and other nasty surprises. Does
 * not guarantee that the returned time is near the current
 * time returned by #GNUNET_TIME_absolute_get().  Two
 * subsequent calls (within a short time period) may return the
 * same value. Persists the last returned time on disk to
 * ensure that time never goes backwards. As a result, the
 * resulting value can be used to check if a message is the
 * "most recent" value and replays of older messages (from
 * the same origin) would be discarded.
 *
 * @param cfg configuration, used to determine where to
 *   store the time; user can also insist RTC is working
 *   nicely and disable the feature
 * @return monotonically increasing time
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_monotonic (
  const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  static const struct GNUNET_CONFIGURATION_Handle *last_cfg;
  static struct GNUNET_TIME_Absolute last_time;
  static struct GNUNET_DISK_MapHandle *map_handle;
  static ATOMIC volatile uint64_t *map;
  struct GNUNET_TIME_Absolute now;

  now = GNUNET_TIME_absolute_get ();
  if (last_cfg != cfg)
  {
    char *filename;

    if (NULL != map_handle)
    {
      GNUNET_DISK_file_unmap (map_handle);
      map_handle = NULL;
    }
    map = NULL;

    last_cfg = cfg;
    if ((NULL != cfg) &&
        (GNUNET_OK ==
         GNUNET_CONFIGURATION_get_value_filename (cfg,
                                                  "util",
                                                  "MONOTONIC_TIME_FILENAME",
                                                  &filename)))
    {
      struct GNUNET_DISK_FileHandle *fh;

      fh = GNUNET_DISK_file_open (filename,
                                  GNUNET_DISK_OPEN_READWRITE
                                  | GNUNET_DISK_OPEN_CREATE,
                                  GNUNET_DISK_PERM_USER_WRITE
                                  | GNUNET_DISK_PERM_GROUP_WRITE
                                  | GNUNET_DISK_PERM_USER_READ
                                  | GNUNET_DISK_PERM_GROUP_READ);
      if (NULL == fh)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    _ ("Failed to map `%s', cannot assure monotonic time!\n"),
                    filename);
      }
      else
      {
        off_t size;

        size = 0;
        GNUNET_break (GNUNET_OK == GNUNET_DISK_file_handle_size (fh, &size));
        if (size < (off_t) sizeof(*map))
        {
          struct GNUNET_TIME_AbsoluteNBO o;

          o = GNUNET_TIME_absolute_hton (now);
          if (sizeof(o) != GNUNET_DISK_file_write (fh, &o, sizeof(o)))
            size = 0;
          else
            size = sizeof(o);
        }
        if (size == sizeof(*map))
        {
          map = GNUNET_DISK_file_map (fh,
                                      &map_handle,
                                      GNUNET_DISK_MAP_TYPE_READWRITE,
                                      sizeof(*map));
          if (NULL == map)
            GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                        _ (
                          "Failed to map `%s', cannot assure monotonic time!\n"),
                        filename);
        }
        else
        {
          GNUNET_log (
            GNUNET_ERROR_TYPE_WARNING,
            _ (
              "Failed to setup monotonic time file `%s', cannot assure monotonic time!\n"),
            filename);
        }
      }
      GNUNET_DISK_file_close (fh);
      GNUNET_free (filename);
    }
  }
  if (NULL != map)
  {
    struct GNUNET_TIME_AbsoluteNBO mt;

#if __STDC_NO_ATOMICS__
#if __GNUC__
    mt.abs_value_us__ = __sync_fetch_and_or (map, 0);
#else
    mt.abs_value_us__ = *map;   /* godspeed, pray this is atomic */
#endif
#else
    mt.abs_value_us__ = atomic_load (map);
#endif
    last_time =
      GNUNET_TIME_absolute_max (GNUNET_TIME_absolute_ntoh (mt), last_time);
  }
  if (now.abs_value_us <= last_time.abs_value_us)
    now.abs_value_us = last_time.abs_value_us + 1;
  last_time = now;
  if (NULL != map)
  {
    uint64_t val = GNUNET_TIME_absolute_hton (now).abs_value_us__;
#if __STDC_NO_ATOMICS__
#if __GNUC__
    (void) __sync_lock_test_and_set (map, val);
#else
    *map = val;   /* godspeed, pray this is atomic */
#endif
#else
    atomic_store (map, val);
#endif
  }
  return now;
}


/**
 * Destructor
 */
void __attribute__ ((destructor))
GNUNET_util_time_fini ()
{
  (void) GNUNET_TIME_absolute_get_monotonic (NULL);
}


/* end of time.c */