summaryrefslogtreecommitdiff
path: root/src/util/container_multishortmap.c
blob: 77e5ca139d61db7eb43474afe5ba54ca7a24a945 (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
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
/*
     This file is part of GNUnet.
     Copyright (C) 2008, 2012 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/container_multishortmap.c
 * @brief hash map where the same key may be present multiple times
 * @author Christian Grothoff
 */

#include "platform.h"
#include "gnunet_util_lib.h"

#define LOG(kind, ...) \
  GNUNET_log_from (kind, "util-container-multishortmap", __VA_ARGS__)

/**
 * Maximum recursion depth for callbacks of
 * #GNUNET_CONTAINER_multihashmap_get_multiple() themselves s
 * again calling #GNUNET_CONTAINER_multihashmap_get_multiple().
 * Should be totally excessive, but if violated we die.
 */
#define NEXT_CACHE_SIZE 16


/**
 * An entry in the hash map with the full key.
 */
struct BigMapEntry
{
  /**
   * Value of the entry.
   */
  void *value;

  /**
   * If there is a hash collision, we create a linked list.
   */
  struct BigMapEntry *next;

  /**
   * Key for the entry.
   */
  struct GNUNET_ShortHashCode key;
};


/**
 * An entry in the hash map with just a pointer to the key.
 */
struct SmallMapEntry
{
  /**
   * Value of the entry.
   */
  void *value;

  /**
   * If there is a hash collision, we create a linked list.
   */
  struct SmallMapEntry *next;

  /**
   * Key for the entry.
   */
  const struct GNUNET_ShortHashCode *key;
};


/**
 * Entry in the map.
 */
union MapEntry
{
  /**
   * Variant used if map entries only contain a pointer to the key.
   */
  struct SmallMapEntry *sme;

  /**
   * Variant used if map entries contain the full key.
   */
  struct BigMapEntry *bme;
};


/**
 * Internal representation of the hash map.
 */
struct GNUNET_CONTAINER_MultiShortmap
{
  /**
   * All of our buckets.
   */
  union MapEntry *map;

  /**
   * Number of entries in the map.
   */
  unsigned int size;

  /**
   * Length of the "map" array.
   */
  unsigned int map_length;

  /**
   * #GNUNET_NO if the map entries are of type 'struct BigMapEntry',
   * #GNUNET_YES if the map entries are of type 'struct SmallMapEntry'.
   */
  int use_small_entries;

  /**
   * Counts the destructive modifications (grow, remove)
   * to the map, so that iterators can check if they are still valid.
   */
  unsigned int modification_counter;

  /**
   * Map entries indicating iteration positions currently
   * in use by #GNUNET_CONTAINER_multihashmap_get_multiple().
   * Only used up to @e next_cache_off.
   */
  union MapEntry next_cache[NEXT_CACHE_SIZE];

  /**
   * Offset of @e next_cache entries in use, must be smaller
   * than #NEXT_CACHE_SIZE.
   */
  unsigned int next_cache_off;
};


/**
 * Cursor into a multishortmap.
 * Allows to enumerate elements asynchronously.
 */
struct GNUNET_CONTAINER_MultiShortmapIterator
{
  /**
   * Position in the bucket 'idx'
   */
  union MapEntry me;

  /**
   * Current bucket index.
   */
  unsigned int idx;

  /**
   * Modification counter as observed on the map when the iterator
   * was created.
   */
  unsigned int modification_counter;

  /**
   * Map that we are iterating over.
   */
  const struct GNUNET_CONTAINER_MultiShortmap *map;
};


/**
 * Create a multi hash map.
 *
 * @param len initial size (map will grow as needed)
 * @param do_not_copy_keys #GNUNET_NO is always safe and should be used by default;
 *                         #GNUNET_YES means that on 'put', the 'key' does not have
 *                         to be copied as the destination of the pointer is
 *                         guaranteed to be life as long as the value is stored in
 *                         the hashmap.  This can significantly reduce memory
 *                         consumption, but of course is also a recipe for
 *                         heap corruption if the assumption is not true.  Only
 *                         use this if (1) memory use is important in this case and
 *                         (2) you have triple-checked that the invariant holds
 * @return NULL on error
 */
struct GNUNET_CONTAINER_MultiShortmap *
GNUNET_CONTAINER_multishortmap_create (unsigned int len, int do_not_copy_keys)
{
  struct GNUNET_CONTAINER_MultiShortmap *map;

  GNUNET_assert (len > 0);
  map = GNUNET_new (struct GNUNET_CONTAINER_MultiShortmap);
  map->map = GNUNET_malloc_large (len * sizeof(union MapEntry));
  if (NULL == map->map)
  {
    GNUNET_free (map);
    return NULL;
  }
  map->map_length = len;
  map->use_small_entries = do_not_copy_keys;
  return map;
}


/**
 * Destroy a hash map.  Will not free any values
 * stored in the hash map!
 *
 * @param map the map
 */
void
GNUNET_CONTAINER_multishortmap_destroy (
  struct GNUNET_CONTAINER_MultiShortmap *map)
{
  GNUNET_assert (0 == map->next_cache_off);
  for (unsigned int i = 0; i < map->map_length; i++)
  {
    union MapEntry me;

    me = map->map[i];
    if (map->use_small_entries)
    {
      struct SmallMapEntry *sme;
      struct SmallMapEntry *nxt;

      nxt = me.sme;
      while (NULL != (sme = nxt))
      {
        nxt = sme->next;
        GNUNET_free (sme);
      }
      me.sme = NULL;
    }
    else
    {
      struct BigMapEntry *bme;
      struct BigMapEntry *nxt;

      nxt = me.bme;
      while (NULL != (bme = nxt))
      {
        nxt = bme->next;
        GNUNET_free (bme);
      }
      me.bme = NULL;
    }
  }
  GNUNET_free (map->map);
  GNUNET_free (map);
}


/**
 * Compute the index of the bucket for the given key.
 *
 * @param map hash map for which to compute the index
 * @param key what key should the index be computed for
 * @return offset into the "map" array of "map"
 */
static unsigned int
idx_of (const struct GNUNET_CONTAINER_MultiShortmap *map,
        const struct GNUNET_ShortHashCode *key)
{
  unsigned int kx;

  GNUNET_assert (NULL != map);
  GNUNET_memcpy (&kx, key, sizeof(kx));
  return kx % map->map_length;
}


/**
 * Get the number of key-value pairs in the map.
 *
 * @param map the map
 * @return the number of key value pairs
 */
unsigned int
GNUNET_CONTAINER_multishortmap_size (
  const struct GNUNET_CONTAINER_MultiShortmap *map)
{
  return map->size;
}


/**
 * Given a key find a value in the map matching the key.
 *
 * @param map the map
 * @param key what to look for
 * @return NULL if no value was found; note that
 *   this is indistinguishable from values that just
 *   happen to be NULL; use "contains" to test for
 *   key-value pairs with value NULL
 */
void *
GNUNET_CONTAINER_multishortmap_get (
  const struct GNUNET_CONTAINER_MultiShortmap *map,
  const struct GNUNET_ShortHashCode *key)
{
  union MapEntry me;

  me = map->map[idx_of (map, key)];
  if (map->use_small_entries)
  {
    for (struct SmallMapEntry *sme = me.sme; NULL != sme; sme = sme->next)
      if (0 == GNUNET_memcmp (key, sme->key))
        return sme->value;
  }
  else
  {
    for (struct BigMapEntry *bme = me.bme; NULL != bme; bme = bme->next)
      if (0 == GNUNET_memcmp (key, &bme->key))
        return bme->value;
  }
  return NULL;
}


/**
 * Iterate over all entries in the map.
 *
 * @param map the map
 * @param it function to call on each entry
 * @param it_cls extra argument to @a it
 * @return the number of key value pairs processed,
 *         #GNUNET_SYSERR if it aborted iteration
 */
int
GNUNET_CONTAINER_multishortmap_iterate (
  struct GNUNET_CONTAINER_MultiShortmap *map,
  GNUNET_CONTAINER_ShortmapIterator it,
  void *it_cls)
{
  int count;
  union MapEntry me;
  union MapEntry *ce;
  struct GNUNET_ShortHashCode kc;

  count = 0;
  GNUNET_assert (NULL != map);
  ce = &map->next_cache[map->next_cache_off];
  GNUNET_assert (++map->next_cache_off < NEXT_CACHE_SIZE);
  for (unsigned int i = 0; i < map->map_length; i++)
  {
    me = map->map[i];
    if (map->use_small_entries)
    {
      struct SmallMapEntry *sme;

      ce->sme = me.sme;
      while (NULL != (sme = ce->sme))
      {
        ce->sme = sme->next;
        if ((NULL != it) && (GNUNET_OK != it (it_cls, sme->key, sme->value)))
        {
          GNUNET_assert (--map->next_cache_off < NEXT_CACHE_SIZE);
          return GNUNET_SYSERR;
        }
        count++;
      }
    }
    else
    {
      struct BigMapEntry *bme;

      ce->bme = me.bme;
      while (NULL != (bme = ce->bme))
      {
        ce->bme = bme->next;
        if (NULL != it)
        {
          kc = bme->key;
          if (GNUNET_OK != it (it_cls, &kc, bme->value))
          {
            GNUNET_assert (--map->next_cache_off < NEXT_CACHE_SIZE);
            return GNUNET_SYSERR;
          }
        }
        count++;
      }
    }
  }
  GNUNET_assert (--map->next_cache_off < NEXT_CACHE_SIZE);
  return count;
}


/**
 * We are about to free() the @a bme, make sure it is not in
 * the list of next values for any iterator in the @a map's next_cache.
 *
 * @param map the map to check
 * @param bme the entry that is about to be free'd
 */
static void
update_next_cache_bme (struct GNUNET_CONTAINER_MultiShortmap *map,
                       const struct BigMapEntry *bme)
{
  for (unsigned int i = 0; i < map->next_cache_off; i++)
    if (map->next_cache[i].bme == bme)
      map->next_cache[i].bme = bme->next;
}


/**
 * We are about to free() the @a sme, make sure it is not in
 * the list of next values for any iterator in the @a map's next_cache.
 *
 * @param map the map to check
 * @param sme the entry that is about to be free'd
 */
static void
update_next_cache_sme (struct GNUNET_CONTAINER_MultiShortmap *map,
                       const struct SmallMapEntry *sme)
{
  for (unsigned int i = 0; i < map->next_cache_off; i++)
    if (map->next_cache[i].sme == sme)
      map->next_cache[i].sme = sme->next;
}


/**
 * Remove the given key-value pair from the map.  Note that if the
 * key-value pair is in the map multiple times, only one of the pairs
 * will be removed.
 *
 * @param map the map
 * @param key key of the key-value pair
 * @param value value of the key-value pair
 * @return #GNUNET_YES on success, #GNUNET_NO if the key-value pair
 *  is not in the map
 */
int
GNUNET_CONTAINER_multishortmap_remove (
  struct GNUNET_CONTAINER_MultiShortmap *map,
  const struct GNUNET_ShortHashCode *key,
  const void *value)
{
  union MapEntry me;
  unsigned int i;

  map->modification_counter++;
  i = idx_of (map, key);
  me = map->map[i];
  if (map->use_small_entries)
  {
    struct SmallMapEntry *p = NULL;

    for (struct SmallMapEntry *sme = me.sme; NULL != sme; sme = sme->next)
    {
      if ((0 == GNUNET_memcmp (key, sme->key)) && (value == sme->value))
      {
        if (NULL == p)
          map->map[i].sme = sme->next;
        else
          p->next = sme->next;
        update_next_cache_sme (map, sme);
        GNUNET_free (sme);
        map->size--;
        return GNUNET_YES;
      }
      p = sme;
    }
  }
  else
  {
    struct BigMapEntry *p = NULL;

    for (struct BigMapEntry *bme = me.bme; NULL != bme; bme = bme->next)
    {
      if ((0 == GNUNET_memcmp (key, &bme->key)) && (value == bme->value))
      {
        if (NULL == p)
          map->map[i].bme = bme->next;
        else
          p->next = bme->next;
        update_next_cache_bme (map, bme);
        GNUNET_free (bme);
        map->size--;
        return GNUNET_YES;
      }
      p = bme;
    }
  }
  return GNUNET_NO;
}


/**
 * Remove all entries for the given key from the map.
 * Note that the values would not be "freed".
 *
 * @param map the map
 * @param key identifies values to be removed
 * @return number of values removed
 */
int
GNUNET_CONTAINER_multishortmap_remove_all (
  struct GNUNET_CONTAINER_MultiShortmap *map,
  const struct GNUNET_ShortHashCode *key)
{
  union MapEntry me;
  unsigned int i;
  int ret;

  map->modification_counter++;

  ret = 0;
  i = idx_of (map, key);
  me = map->map[i];
  if (map->use_small_entries)
  {
    struct SmallMapEntry *sme;
    struct SmallMapEntry *p;

    p = NULL;
    sme = me.sme;
    while (NULL != sme)
    {
      if (0 == GNUNET_memcmp (key, sme->key))
      {
        if (NULL == p)
          map->map[i].sme = sme->next;
        else
          p->next = sme->next;
        update_next_cache_sme (map, sme);
        GNUNET_free (sme);
        map->size--;
        if (NULL == p)
          sme = map->map[i].sme;
        else
          sme = p->next;
        ret++;
      }
      else
      {
        p = sme;
        sme = sme->next;
      }
    }
  }
  else
  {
    struct BigMapEntry *bme;
    struct BigMapEntry *p;

    p = NULL;
    bme = me.bme;
    while (NULL != bme)
    {
      if (0 == GNUNET_memcmp (key, &bme->key))
      {
        if (NULL == p)
          map->map[i].bme = bme->next;
        else
          p->next = bme->next;
        update_next_cache_bme (map, bme);
        GNUNET_free (bme);
        map->size--;
        if (NULL == p)
          bme = map->map[i].bme;
        else
          bme = p->next;
        ret++;
      }
      else
      {
        p = bme;
        bme = bme->next;
      }
    }
  }
  return ret;
}


/**
 * Check if the map contains any value under the given
 * key (including values that are NULL).
 *
 * @param map the map
 * @param key the key to test if a value exists for it
 * @return #GNUNET_YES if such a value exists,
 *         #GNUNET_NO if not
 */
int
GNUNET_CONTAINER_multishortmap_contains (
  const struct GNUNET_CONTAINER_MultiShortmap *map,
  const struct GNUNET_ShortHashCode *key)
{
  union MapEntry me;

  me = map->map[idx_of (map, key)];
  if (map->use_small_entries)
  {
    for (struct SmallMapEntry *sme = me.sme; NULL != sme; sme = sme->next)
      if (0 == GNUNET_memcmp (key, sme->key))
        return GNUNET_YES;
  }
  else
  {
    for (struct BigMapEntry *bme = me.bme; NULL != bme; bme = bme->next)
      if (0 == GNUNET_memcmp (key, &bme->key))
        return GNUNET_YES;
  }
  return GNUNET_NO;
}


/**
 * Check if the map contains the given value under the given
 * key.
 *
 * @param map the map
 * @param key the key to test if a value exists for it
 * @param value value to test for
 * @return #GNUNET_YES if such a value exists,
 *         #GNUNET_NO if not
 */
int
GNUNET_CONTAINER_multishortmap_contains_value (
  const struct GNUNET_CONTAINER_MultiShortmap *map,
  const struct GNUNET_ShortHashCode *key,
  const void *value)
{
  union MapEntry me;

  me = map->map[idx_of (map, key)];
  if (map->use_small_entries)
  {
    for (struct SmallMapEntry *sme = me.sme; NULL != sme; sme = sme->next)
      if ((0 == GNUNET_memcmp (key, sme->key)) && (sme->value == value))
        return GNUNET_YES;
  }
  else
  {
    for (struct BigMapEntry *bme = me.bme; NULL != bme; bme = bme->next)
      if ((0 == GNUNET_memcmp (key, &bme->key)) && (bme->value == value))
        return GNUNET_YES;
  }
  return GNUNET_NO;
}


/**
 * Grow the given map to a more appropriate size.
 *
 * @param map the hash map to grow
 */
static void
grow (struct GNUNET_CONTAINER_MultiShortmap *map)
{
  union MapEntry *old_map;
  union MapEntry *new_map;
  unsigned int old_len;
  unsigned int new_len;
  unsigned int idx;

  old_map = map->map;
  old_len = map->map_length;
  new_len = old_len * 2;
  if (0 == new_len) /* 2^31 * 2 == 0 */
    new_len = old_len; /* never use 0 */
  if (new_len == old_len)
    return; /* nothing changed */
  new_map = GNUNET_malloc_large (new_len * sizeof(union MapEntry));
  if (NULL == new_map)
    return; /* grow not possible */
  map->modification_counter++;
  map->map_length = new_len;
  map->map = new_map;
  for (unsigned int i = 0; i < old_len; i++)
  {
    if (map->use_small_entries)
    {
      struct SmallMapEntry *sme;

      while (NULL != (sme = old_map[i].sme))
      {
        old_map[i].sme = sme->next;
        idx = idx_of (map, sme->key);
        sme->next = new_map[idx].sme;
        new_map[idx].sme = sme;
      }
    }
    else
    {
      struct BigMapEntry *bme;

      while (NULL != (bme = old_map[i].bme))
      {
        old_map[i].bme = bme->next;
        idx = idx_of (map, &bme->key);
        bme->next = new_map[idx].bme;
        new_map[idx].bme = bme;
      }
    }
  }
  GNUNET_free (old_map);
}


/**
 * Store a key-value pair in the map.
 *
 * @param map the map
 * @param key key to use
 * @param value value to use
 * @param opt options for put
 * @return #GNUNET_OK on success,
 *         #GNUNET_NO if a value was replaced (with REPLACE)
 *         #GNUNET_SYSERR if #GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY was the option and the
 *                       value already exists
 */
int
GNUNET_CONTAINER_multishortmap_put (
  struct GNUNET_CONTAINER_MultiShortmap *map,
  const struct GNUNET_ShortHashCode *key,
  void *value,
  enum GNUNET_CONTAINER_MultiHashMapOption opt)
{
  union MapEntry me;
  unsigned int i;

  i = idx_of (map, key);
  if ((opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE) &&
      (opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST))
  {
    me = map->map[i];
    if (map->use_small_entries)
    {
      for (struct SmallMapEntry *sme = me.sme; NULL != sme; sme = sme->next)
        if (0 == GNUNET_memcmp (key, sme->key))
        {
          if (opt == GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY)
            return GNUNET_SYSERR;
          sme->value = value;
          return GNUNET_NO;
        }
    }
    else
    {
      for (struct BigMapEntry *bme = me.bme; NULL != bme; bme = bme->next)
        if (0 == GNUNET_memcmp (key, &bme->key))
        {
          if (opt == GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY)
            return GNUNET_SYSERR;
          bme->value = value;
          return GNUNET_NO;
        }
    }
  }
  if (map->size / 3 >= map->map_length / 4)
  {
    grow (map);
    i = idx_of (map, key);
  }
  if (map->use_small_entries)
  {
    struct SmallMapEntry *sme;

    sme = GNUNET_new (struct SmallMapEntry);
    sme->key = key;
    sme->value = value;
    sme->next = map->map[i].sme;
    map->map[i].sme = sme;
  }
  else
  {
    struct BigMapEntry *bme;

    bme = GNUNET_new (struct BigMapEntry);
    bme->key = *key;
    bme->value = value;
    bme->next = map->map[i].bme;
    map->map[i].bme = bme;
  }
  map->size++;
  return GNUNET_OK;
}


/**
 * Iterate over all entries in the map that match a particular key.
 *
 * @param map the map
 * @param key key that the entries must correspond to
 * @param it function to call on each entry
 * @param it_cls extra argument to @a it
 * @return the number of key value pairs processed,
 *         #GNUNET_SYSERR if it aborted iteration
 */
int
GNUNET_CONTAINER_multishortmap_get_multiple (
  struct GNUNET_CONTAINER_MultiShortmap *map,
  const struct GNUNET_ShortHashCode *key,
  GNUNET_CONTAINER_ShortmapIterator it,
  void *it_cls)
{
  int count;
  union MapEntry me;
  union MapEntry *ce;

  ce = &map->next_cache[map->next_cache_off];
  GNUNET_assert (++map->next_cache_off < NEXT_CACHE_SIZE);
  count = 0;
  me = map->map[idx_of (map, key)];
  if (map->use_small_entries)
  {
    struct SmallMapEntry *sme;

    ce->sme = me.sme;
    while (NULL != (sme = ce->sme))
    {
      ce->sme = sme->next;
      if (0 != GNUNET_memcmp (key, sme->key))
        continue;
      if ((NULL != it) && (GNUNET_OK != it (it_cls, key, sme->value)))
      {
        GNUNET_assert (--map->next_cache_off < NEXT_CACHE_SIZE);
        return GNUNET_SYSERR;
      }
      count++;
    }
  }
  else
  {
    struct BigMapEntry *bme;

    ce->bme = me.bme;
    while (NULL != (bme = ce->bme))
    {
      ce->bme = bme->next;
      if (0 != GNUNET_memcmp (key, &bme->key))
        continue;
      if ((NULL != it) && (GNUNET_OK != it (it_cls, key, bme->value)))
      {
        GNUNET_assert (--map->next_cache_off < NEXT_CACHE_SIZE);
        return GNUNET_SYSERR;
      }
      count++;
    }
  }
  GNUNET_assert (--map->next_cache_off < NEXT_CACHE_SIZE);
  return count;
}


/**
 * @ingroup hashmap
 * Call @a it on a random value from the map, or not at all
 * if the map is empty.  Note that this function has linear
 * complexity (in the size of the map).
 *
 * @param map the map
 * @param it function to call on a random entry
 * @param it_cls extra argument to @a it
 * @return the number of key value pairs processed, zero or one.
 */
unsigned int
GNUNET_CONTAINER_multishortmap_get_random (
  const struct GNUNET_CONTAINER_MultiShortmap *map,
  GNUNET_CONTAINER_ShortmapIterator it,
  void *it_cls)
{
  unsigned int off;
  union MapEntry me;

  if (0 == map->size)
    return 0;
  if (NULL == it)
    return 1;
  off = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE, map->size);
  for (unsigned int idx = 0; idx < map->map_length; idx++)
  {
    me = map->map[idx];
    if (map->use_small_entries)
    {
      for (struct SmallMapEntry *sme = me.sme; NULL != sme; sme = sme->next)
      {
        if (0 == off)
        {
          if (GNUNET_OK != it (it_cls, sme->key, sme->value))
            return GNUNET_SYSERR;
          return 1;
        }
        off--;
      }
    }
    else
    {
      for (struct BigMapEntry *bme = me.bme; NULL != bme; bme = bme->next)
      {
        if (0 == off)
        {
          if (GNUNET_OK != it (it_cls, &bme->key, bme->value))
            return GNUNET_SYSERR;
          return 1;
        }
        off--;
      }
    }
  }
  GNUNET_break (0);
  return GNUNET_SYSERR;
}


/**
 * Create an iterator for a multishortmap.
 * The iterator can be used to retrieve all the elements in the multishortmap
 * one by one, without having to handle all elements at once (in contrast to
 * #GNUNET_CONTAINER_multishortmap_iterate).  Note that the iterator can not be
 * used anymore if elements have been removed from 'map' after the creation of
 * the iterator, or 'map' has been destroyed.  Adding elements to 'map' may
 * result in skipped or repeated elements.
 *
 * @param map the map to create an iterator for
 * @return an iterator over the given multishortmap 'map'
 */
struct GNUNET_CONTAINER_MultiShortmapIterator *
GNUNET_CONTAINER_multishortmap_iterator_create (
  const struct GNUNET_CONTAINER_MultiShortmap *map)
{
  struct GNUNET_CONTAINER_MultiShortmapIterator *iter;

  iter = GNUNET_new (struct GNUNET_CONTAINER_MultiShortmapIterator);
  iter->map = map;
  iter->modification_counter = map->modification_counter;
  iter->me = map->map[0];
  return iter;
}


/**
 * Retrieve the next element from the hash map at the iterator's position.
 * If there are no elements left, GNUNET_NO is returned, and 'key' and 'value'
 * are not modified.
 * This operation is only allowed if no elements have been removed from the
 * multishortmap since the creation of 'iter', and the map has not been destroyed.
 * Adding elements may result in repeating or skipping elements.
 *
 * @param iter the iterator to get the next element from
 * @param key pointer to store the key in, can be NULL
 * @param value pointer to store the value in, can be NULL
 * @return #GNUNET_YES we returned an element,
 *         #GNUNET_NO if we are out of elements
 */
int
GNUNET_CONTAINER_multishortmap_iterator_next (
  struct GNUNET_CONTAINER_MultiShortmapIterator *iter,
  struct GNUNET_ShortHashCode *key,
  const void **value)
{
  /* make sure the map has not been modified */
  GNUNET_assert (iter->modification_counter == iter->map->modification_counter);

  /* look for the next entry, skipping empty buckets */
  while (1)
  {
    if (iter->idx >= iter->map->map_length)
      return GNUNET_NO;
    if (GNUNET_YES == iter->map->use_small_entries)
    {
      if (NULL != iter->me.sme)
      {
        if (NULL != key)
          *key = *iter->me.sme->key;
        if (NULL != value)
          *value = iter->me.sme->value;
        iter->me.sme = iter->me.sme->next;
        return GNUNET_YES;
      }
    }
    else
    {
      if (NULL != iter->me.bme)
      {
        if (NULL != key)
          *key = iter->me.bme->key;
        if (NULL != value)
          *value = iter->me.bme->value;
        iter->me.bme = iter->me.bme->next;
        return GNUNET_YES;
      }
    }
    iter->idx += 1;
    if (iter->idx < iter->map->map_length)
      iter->me = iter->map->map[iter->idx];
  }
}


/**
 * Destroy a multishortmap iterator.
 *
 * @param iter the iterator to destroy
 */
void
GNUNET_CONTAINER_multishortmap_iterator_destroy (
  struct GNUNET_CONTAINER_MultiShortmapIterator *iter)
{
  GNUNET_free (iter);
}


/* end of container_multishortmap.c */