aboutsummaryrefslogtreecommitdiffstats
path: root/subversion/libsvn_fs_x/temp_serializer.c
blob: b1aaa2b2f9dfb88eaacf33fd7c6db4856cde3341 (plain) (blame)
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
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
/* temp_serializer.c: serialization functions for caching of FSX structures
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */

#include <apr_pools.h>

#include "svn_pools.h"
#include "svn_hash.h"
#include "svn_sorts.h"
#include "svn_fs.h"

#include "private/svn_fs_util.h"
#include "private/svn_sorts_private.h"
#include "private/svn_temp_serializer.h"
#include "private/svn_subr_private.h"

#include "id.h"
#include "temp_serializer.h"
#include "low_level.h"
#include "cached_data.h"

/* Utility to encode a signed NUMBER into a variable-length sequence of
 * 8-bit chars in KEY_BUFFER and return the last writen position.
 *
 * Numbers will be stored in 7 bits / byte and using byte values above
 * 32 (' ') to make them combinable with other string by simply separating
 * individual parts with spaces.
 */
static char*
encode_number(apr_int64_t number, char *key_buffer)
{
  /* encode the sign in the first byte */
  if (number < 0)
  {
    number = -number;
    *key_buffer = (char)((number & 63) + ' ' + 65);
  }
  else
    *key_buffer = (char)((number & 63) + ' ' + 1);
  number /= 64;

  /* write 7 bits / byte until no significant bits are left */
  while (number)
  {
    *++key_buffer = (char)((number & 127) + ' ' + 1);
    number /= 128;
  }

  /* return the last written position */
  return key_buffer;
}

const char*
svn_fs_x__combine_number_and_string(apr_int64_t number,
                                    const char *string,
                                    apr_pool_t *result_pool)
{
  apr_size_t len = strlen(string);

  /* number part requires max. 10x7 bits + 1 space.
   * Add another 1 for the terminal 0 */
  char *key_buffer = apr_palloc(result_pool, len + 12);
  const char *key = key_buffer;

  /* Prepend the number to the string and separate them by space. No other
   * number can result in the same prefix, no other string in the same
   * postfix nor can the boundary between them be ambiguous. */
  key_buffer = encode_number(number, key_buffer);
  *++key_buffer = ' ';
  memcpy(++key_buffer, string, len+1);

  /* return the start of the key */
  return key;
}

/* Utility function to serialize string S in the given serialization CONTEXT.
 */
static void
serialize_svn_string(svn_temp_serializer__context_t *context,
                     const svn_string_t * const *s)
{
  const svn_string_t *string = *s;

  /* Nothing to do for NULL string references. */
  if (string == NULL)
    return;

  svn_temp_serializer__push(context,
                            (const void * const *)s,
                            sizeof(*string));

  /* the "string" content may actually be arbitrary binary data.
   * Thus, we cannot use svn_temp_serializer__add_string. */
  svn_temp_serializer__add_leaf(context,
                                (const void * const *)&string->data,
                                string->len + 1);

  /* back to the caller's nesting level */
  svn_temp_serializer__pop(context);
}

/* Utility function to deserialize the STRING inside the BUFFER.
 */
static void
deserialize_svn_string(const void *buffer, svn_string_t **string)
{
  svn_temp_deserializer__resolve(buffer, (void **)string);
  if (*string == NULL)
    return;

  svn_temp_deserializer__resolve(*string, (void **)&(*string)->data);
}

/* Utility function to serialize the REPRESENTATION within the given
 * serialization CONTEXT.
 */
static void
serialize_representation(svn_temp_serializer__context_t *context,
                         svn_fs_x__representation_t * const *representation)
{
  const svn_fs_x__representation_t * rep = *representation;
  if (rep == NULL)
    return;

  /* serialize the representation struct itself */
  svn_temp_serializer__add_leaf(context,
                                (const void * const *)representation,
                                sizeof(*rep));
}

void
svn_fs_x__serialize_apr_array(svn_temp_serializer__context_t *context,
                              apr_array_header_t **a)
{
  const apr_array_header_t *array = *a;

  /* Nothing to do for NULL string references. */
  if (array == NULL)
    return;

  /* array header struct */
  svn_temp_serializer__push(context,
                            (const void * const *)a,
                            sizeof(*array));

  /* contents */
  svn_temp_serializer__add_leaf(context,
                                (const void * const *)&array->elts,
                                (apr_size_t)array->nelts * array->elt_size);

  /* back to the caller's nesting level */
  svn_temp_serializer__pop(context);
}

void
svn_fs_x__deserialize_apr_array(void *buffer,
                                apr_array_header_t **array,
                                apr_pool_t *result_pool)
{
  svn_temp_deserializer__resolve(buffer, (void **)array);
  if (*array == NULL)
    return;

  svn_temp_deserializer__resolve(*array, (void **)&(*array)->elts);
  (*array)->pool = result_pool;
}

/* auxilliary structure representing the content of a directory array */
typedef struct dir_data_t
{
  /* number of entries in the directory
   * (it's int because the directory is an APR array) */
  int count;

  /** Current length of the in-txn in-disk representation of the directory.
   * SVN_INVALID_FILESIZE if unknown (i.e. committed data). */
  svn_filesize_t txn_filesize;

  /* number of unused dir entry buckets in the index */
  apr_size_t over_provision;

  /* internal modifying operations counter
   * (used to repack data once in a while) */
  apr_size_t operations;

  /* size of the serialization buffer actually used.
   * (we will allocate more than we actually need such that we may
   * append more data in situ later) */
  apr_size_t len;

  /* reference to the entries */
  svn_fs_x__dirent_t **entries;

  /* size of the serialized entries and don't be too wasteful
   * (needed since the entries are no longer in sequence) */
  apr_uint32_t *lengths;
} dir_data_t;

/* Utility function to serialize the *ENTRY_P into a the given
 * serialization CONTEXT. Return the serialized size of the
 * dir entry in *LENGTH.
 */
static void
serialize_dir_entry(svn_temp_serializer__context_t *context,
                    svn_fs_x__dirent_t **entry_p,
                    apr_uint32_t *length)
{
  svn_fs_x__dirent_t *entry = *entry_p;
  apr_size_t initial_length = svn_temp_serializer__get_length(context);

  svn_temp_serializer__push(context,
                            (const void * const *)entry_p,
                            sizeof(**entry_p));

  svn_temp_serializer__add_string(context, &entry->name);

  *length = (apr_uint32_t)(  svn_temp_serializer__get_length(context)
                           - APR_ALIGN_DEFAULT(initial_length));

  svn_temp_serializer__pop(context);
}

/* Utility function to serialize the DIR into a new serialization
 * context to be returned.
 *
 * Temporary allocation will be made form SCRATCH_POOL.
 */
static svn_temp_serializer__context_t *
serialize_dir(svn_fs_x__dir_data_t *dir,
              apr_pool_t *scratch_pool)
{
  dir_data_t dir_data;
  int i = 0;
  svn_temp_serializer__context_t *context;
  apr_array_header_t *entries = dir->entries;

  /* calculate sizes */
  int count = entries->nelts;
  apr_size_t over_provision = 2 + count / 4;
  apr_size_t entries_len =   (count + over_provision)
                           * sizeof(svn_fs_x__dirent_t*);
  apr_size_t lengths_len = (count + over_provision) * sizeof(apr_uint32_t);

  /* Estimate the size of a directory entry + its name. */
  enum { ENTRY_SIZE = sizeof(svn_fs_x__dirent_t) + 32 };

  /* copy the hash entries to an auxiliary struct of known layout */
  dir_data.count = count;
  dir_data.txn_filesize = dir->txn_filesize;
  dir_data.over_provision = over_provision;
  dir_data.operations = 0;
  dir_data.entries = apr_palloc(scratch_pool, entries_len);
  dir_data.lengths = apr_palloc(scratch_pool, lengths_len);

  for (i = 0; i < count; ++i)
    dir_data.entries[i] = APR_ARRAY_IDX(entries, i, svn_fs_x__dirent_t *);

  /* Serialize that aux. structure into a new one. Also, provide a good
   * estimate for the size of the buffer that we will need. */
  context = svn_temp_serializer__init(&dir_data,
                                      sizeof(dir_data),
                                      50 + count * ENTRY_SIZE
                                         + entries_len + lengths_len,
                                      scratch_pool);

  /* serialize entries references */
  svn_temp_serializer__push(context,
                            (const void * const *)&dir_data.entries,
                            entries_len);

  /* serialize the individual entries and their sub-structures */
  for (i = 0; i < count; ++i)
    serialize_dir_entry(context,
                        &dir_data.entries[i],
                        &dir_data.lengths[i]);

  svn_temp_serializer__pop(context);

  /* serialize entries references */
  svn_temp_serializer__push(context,
                            (const void * const *)&dir_data.lengths,
                            lengths_len);

  return context;
}

/* Utility function to reconstruct a dir entries struct from serialized data
 * in BUFFER and DIR_DATA. Allocation will be made form RESULT_POOL.
 */
static svn_fs_x__dir_data_t *
deserialize_dir(void *buffer,
                dir_data_t *dir_data,
                apr_pool_t *result_pool)
{
  svn_fs_x__dir_data_t *result;
  apr_size_t i;
  apr_size_t count;
  svn_fs_x__dirent_t *entry;
  svn_fs_x__dirent_t **entries;

  /* Construct empty directory object. */
  result = apr_pcalloc(result_pool, sizeof(*result));
  result->entries
    = apr_array_make(result_pool, dir_data->count,
                     sizeof(svn_fs_x__dirent_t *));
  result->txn_filesize = dir_data->txn_filesize;

  /* resolve the reference to the entries array */
  svn_temp_deserializer__resolve(buffer, (void **)&dir_data->entries);
  entries = dir_data->entries;

  /* fixup the references within each entry and add it to the RESULT */
  for (i = 0, count = dir_data->count; i < count; ++i)
    {
      svn_temp_deserializer__resolve(entries, (void **)&entries[i]);
      entry = dir_data->entries[i];

      /* pointer fixup */
      svn_temp_deserializer__resolve(entry, (void **)&entry->name);

      /* add the entry to the hash */
      APR_ARRAY_PUSH(result->entries, svn_fs_x__dirent_t *) = entry;
    }

  /* return the now complete hash */
  return result;
}

/**
 * Serialize a NODEREV_P within the serialization CONTEXT.
 */
static void
noderev_serialize(svn_temp_serializer__context_t *context,
                  svn_fs_x__noderev_t * const *noderev_p)
{
  const svn_fs_x__noderev_t *noderev = *noderev_p;
  if (noderev == NULL)
    return;

  /* serialize the representation struct itself */
  svn_temp_serializer__push(context,
                            (const void * const *)noderev_p,
                            sizeof(*noderev));

  /* serialize sub-structures */
  serialize_representation(context, &noderev->prop_rep);
  serialize_representation(context, &noderev->data_rep);

  svn_temp_serializer__add_string(context, &noderev->copyfrom_path);
  svn_temp_serializer__add_string(context, &noderev->copyroot_path);
  svn_temp_serializer__add_string(context, &noderev->created_path);

  /* return to the caller's nesting level */
  svn_temp_serializer__pop(context);
}

/**
 * Deserialize a NODEREV_P within the BUFFER and associate it with.
 */
static void
noderev_deserialize(void *buffer,
                    svn_fs_x__noderev_t **noderev_p)
{
  svn_fs_x__noderev_t *noderev;

  /* fixup the reference to the representation itself,
   * if this is part of a parent structure. */
  if (buffer != *noderev_p)
    svn_temp_deserializer__resolve(buffer, (void **)noderev_p);

  noderev = *noderev_p;
  if (noderev == NULL)
    return;

  /* fixup of sub-structures */
  svn_temp_deserializer__resolve(noderev, (void **)&noderev->prop_rep);
  svn_temp_deserializer__resolve(noderev, (void **)&noderev->data_rep);

  svn_temp_deserializer__resolve(noderev, (void **)&noderev->copyfrom_path);
  svn_temp_deserializer__resolve(noderev, (void **)&noderev->copyroot_path);
  svn_temp_deserializer__resolve(noderev, (void **)&noderev->created_path);
}


/* Utility function to serialize COUNT svn_txdelta_op_t objects
 * at OPS in the given serialization CONTEXT.
 */
static void
serialize_txdelta_ops(svn_temp_serializer__context_t *context,
                      const svn_txdelta_op_t * const * ops,
                      apr_size_t count)
{
  if (*ops == NULL)
    return;

  /* the ops form a contiguous chunk of memory with no further references */
  svn_temp_serializer__add_leaf(context,
                                (const void * const *)ops,
                                count * sizeof(svn_txdelta_op_t));
}

/* Utility function to serialize W in the given serialization CONTEXT.
 */
static void
serialize_txdeltawindow(svn_temp_serializer__context_t *context,
                        svn_txdelta_window_t * const * w)
{
  svn_txdelta_window_t *window = *w;

  /* serialize the window struct itself */
  svn_temp_serializer__push(context,
                            (const void * const *)w,
                            sizeof(svn_txdelta_window_t));

  /* serialize its sub-structures */
  serialize_txdelta_ops(context, &window->ops, window->num_ops);
  serialize_svn_string(context, &window->new_data);

  svn_temp_serializer__pop(context);
}

svn_error_t *
svn_fs_x__serialize_txdelta_window(void **buffer,
                                   apr_size_t *buffer_size,
                                   void *item,
                                   apr_pool_t *pool)
{
  svn_fs_x__txdelta_cached_window_t *window_info = item;
  svn_stringbuf_t *serialized;

  /* initialize the serialization process and allocate a buffer large
   * enough to do without the need of re-allocations in most cases. */
  apr_size_t text_len = window_info->window->new_data
                      ? window_info->window->new_data->len
                      : 0;
  svn_temp_serializer__context_t *context =
      svn_temp_serializer__init(window_info,
                                sizeof(*window_info),
                                500 + text_len,
                                pool);

  /* serialize the sub-structure(s) */
  serialize_txdeltawindow(context, &window_info->window);

  /* return the serialized result */
  serialized = svn_temp_serializer__get(context);

  *buffer = serialized->data;
  *buffer_size = serialized->len;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__deserialize_txdelta_window(void **item,
                                     void *buffer,
                                     apr_size_t buffer_size,
                                     apr_pool_t *result_pool)
{
  svn_txdelta_window_t *window;

  /* Copy the _full_ buffer as it also contains the sub-structures. */
  svn_fs_x__txdelta_cached_window_t *window_info =
      (svn_fs_x__txdelta_cached_window_t *)buffer;

  /* pointer reference fixup */
  svn_temp_deserializer__resolve(window_info,
                                 (void **)&window_info->window);
  window = window_info->window;

  svn_temp_deserializer__resolve(window, (void **)&window->ops);

  deserialize_svn_string(window, (svn_string_t**)&window->new_data);

  /* done */
  *item = window_info;

  return SVN_NO_ERROR;
}

/* Auxiliary structure representing the content of a properties hash.
   This structure is much easier to (de-)serialize than an apr_hash.
 */
typedef struct properties_data_t
{
  /* number of entries in the hash */
  apr_size_t count;

  /* reference to the keys */
  const char **keys;

  /* reference to the values */
  const svn_string_t **values;
} properties_data_t;

/* Serialize COUNT C-style strings from *STRINGS into CONTEXT. */
static void
serialize_cstring_array(svn_temp_serializer__context_t *context,
                        const char ***strings,
                        apr_size_t count)
{
  apr_size_t i;
  const char **entries = *strings;

  /* serialize COUNT entries pointers (the array) */
  svn_temp_serializer__push(context,
                            (const void * const *)strings,
                            count * sizeof(const char*));

  /* serialize array elements */
  for (i = 0; i < count; ++i)
    svn_temp_serializer__add_string(context, &entries[i]);

  svn_temp_serializer__pop(context);
}

/* Serialize COUNT svn_string_t* items from *STRINGS into CONTEXT. */
static void
serialize_svn_string_array(svn_temp_serializer__context_t *context,
                           const svn_string_t ***strings,
                           apr_size_t count)
{
  apr_size_t i;
  const svn_string_t **entries = *strings;

  /* serialize COUNT entries pointers (the array) */
  svn_temp_serializer__push(context,
                            (const void * const *)strings,
                            count * sizeof(const char*));

  /* serialize array elements */
  for (i = 0; i < count; ++i)
    serialize_svn_string(context, &entries[i]);

  svn_temp_serializer__pop(context);
}

svn_error_t *
svn_fs_x__serialize_properties(void **data,
                               apr_size_t *data_len,
                               void *in,
                               apr_pool_t *pool)
{
  apr_hash_t *hash = in;
  properties_data_t properties;
  svn_temp_serializer__context_t *context;
  apr_hash_index_t *hi;
  svn_stringbuf_t *serialized;
  apr_size_t i;

  /* create our auxiliary data structure */
  properties.count = apr_hash_count(hash);
  properties.keys = apr_palloc(pool, sizeof(const char*) * (properties.count + 1));
  properties.values = apr_palloc(pool, sizeof(const svn_string_t *) * properties.count);

  /* populate it with the hash entries */
  for (hi = apr_hash_first(pool, hash), i=0; hi; hi = apr_hash_next(hi), ++i)
    {
      properties.keys[i] = apr_hash_this_key(hi);
      properties.values[i] = apr_hash_this_val(hi);
    }

  /* serialize it */
  context = svn_temp_serializer__init(&properties,
                                      sizeof(properties),
                                      properties.count * 100,
                                      pool);

  properties.keys[i] = "";
  serialize_cstring_array(context, &properties.keys, properties.count + 1);
  serialize_svn_string_array(context, &properties.values, properties.count);

  /* return the serialized result */
  serialized = svn_temp_serializer__get(context);

  *data = serialized->data;
  *data_len = serialized->len;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__deserialize_properties(void **out,
                                 void *data,
                                 apr_size_t data_len,
                                 apr_pool_t *result_pool)
{
  apr_hash_t *hash = svn_hash__make(result_pool);
  properties_data_t *properties = (properties_data_t *)data;
  size_t i;

  /* de-serialize our auxiliary data structure */
  svn_temp_deserializer__resolve(properties, (void**)&properties->keys);
  svn_temp_deserializer__resolve(properties, (void**)&properties->values);

  /* de-serialize each entry and put it into the hash */
  for (i = 0; i < properties->count; ++i)
    {
      apr_size_t len = properties->keys[i+1] - properties->keys[i] - 1;
      svn_temp_deserializer__resolve(properties->keys,
                                     (void**)&properties->keys[i]);

      deserialize_svn_string(properties->values,
                             (svn_string_t **)&properties->values[i]);

      apr_hash_set(hash,
                   properties->keys[i], len,
                   properties->values[i]);
    }

  /* done */
  *out = hash;

  return SVN_NO_ERROR;
}

/** Caching svn_fs_x__noderev_t objects. **/

svn_error_t *
svn_fs_x__serialize_node_revision(void **buffer,
                                  apr_size_t *buffer_size,
                                  void *item,
                                  apr_pool_t *pool)
{
  svn_stringbuf_t *serialized;
  svn_fs_x__noderev_t *noderev = item;

  /* create an (empty) serialization context with plenty of (initial)
   * buffer space. */
  svn_temp_serializer__context_t *context =
      svn_temp_serializer__init(NULL, 0,
                                1024 - SVN_TEMP_SERIALIZER__OVERHEAD,
                                pool);

  /* serialize the noderev */
  noderev_serialize(context, &noderev);

  /* return serialized data */
  serialized = svn_temp_serializer__get(context);
  *buffer = serialized->data;
  *buffer_size = serialized->len;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__deserialize_node_revision(void **item,
                                    void *buffer,
                                    apr_size_t buffer_size,
                                    apr_pool_t *result_pool)
{
  /* Copy the _full_ buffer as it also contains the sub-structures. */
  svn_fs_x__noderev_t *noderev = (svn_fs_x__noderev_t *)buffer;

  /* fixup of all pointers etc. */
  noderev_deserialize(noderev, &noderev);

  /* done */
  *item = noderev;
  return SVN_NO_ERROR;
}

/* Utility function that returns the directory serialized inside CONTEXT
 * to DATA and DATA_LEN.  If OVERPROVISION is set, allocate some extra
 * room for future in-place changes by svn_fs_x__replace_dir_entry. */
static svn_error_t *
return_serialized_dir_context(svn_temp_serializer__context_t *context,
                              void **data,
                              apr_size_t *data_len,
                              svn_boolean_t overprovision)
{
  svn_stringbuf_t *serialized = svn_temp_serializer__get(context);

  *data = serialized->data;
  *data_len = overprovision ? serialized->blocksize : serialized->len;
  ((dir_data_t *)serialized->data)->len = serialized->len;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__serialize_dir_entries(void **data,
                                apr_size_t *data_len,
                                void *in,
                                apr_pool_t *pool)
{
  svn_fs_x__dir_data_t *dir = in;

  /* serialize the dir content into a new serialization context
   * and return the serialized data */
  return return_serialized_dir_context(serialize_dir(dir, pool),
                                       data,
                                       data_len,
                                       FALSE);
}

svn_error_t *
svn_fs_x__deserialize_dir_entries(void **out,
                                  void *data,
                                  apr_size_t data_len,
                                  apr_pool_t *result_pool)
{
  /* Copy the _full_ buffer as it also contains the sub-structures. */
  dir_data_t *dir_data = (dir_data_t *)data;

  /* reconstruct the hash from the serialized data */
  *out = deserialize_dir(dir_data, dir_data, result_pool);

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__get_sharded_offset(void **out,
                             const void *data,
                             apr_size_t data_len,
                             void *baton,
                             apr_pool_t *pool)
{
  const apr_off_t *manifest = data;
  apr_int64_t shard_pos = *(apr_int64_t *)baton;

  *(apr_off_t *)out = manifest[shard_pos];

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__extract_dir_filesize(void **out,
                               const void *data,
                               apr_size_t data_len,
                               void *baton,
                               apr_pool_t *pool)
{
  const dir_data_t *dir_data = data;

  *(svn_filesize_t *)out = dir_data->txn_filesize;

  return SVN_NO_ERROR;
}

/* Utility function that returns the lowest index of the first entry in
 * *ENTRIES that points to a dir entry with a name equal or larger than NAME.
 * If an exact match has been found, *FOUND will be set to TRUE. COUNT is
 * the number of valid entries in ENTRIES.
 */
static apr_size_t
find_entry(svn_fs_x__dirent_t **entries,
           const char *name,
           apr_size_t count,
           svn_boolean_t *found)
{
  /* binary search for the desired entry by name */
  apr_size_t lower = 0;
  apr_size_t upper = count;
  apr_size_t middle;

  for (middle = upper / 2; lower < upper; middle = (upper + lower) / 2)
    {
      const svn_fs_x__dirent_t *entry =
          svn_temp_deserializer__ptr(entries, (const void *const *)&entries[middle]);
      const char* entry_name =
          svn_temp_deserializer__ptr(entry, (const void *const *)&entry->name);

      int diff = strcmp(entry_name, name);
      if (diff < 0)
        lower = middle + 1;
      else
        upper = middle;
    }

  /* check whether we actually found a match */
  *found = FALSE;
  if (lower < count)
    {
      const svn_fs_x__dirent_t *entry =
          svn_temp_deserializer__ptr(entries, (const void *const *)&entries[lower]);
      const char* entry_name =
          svn_temp_deserializer__ptr(entry, (const void *const *)&entry->name);

      if (strcmp(entry_name, name) == 0)
        *found = TRUE;
    }

  return lower;
}

/* Utility function that returns TRUE if entry number IDX in ENTRIES has the
 * name NAME.
 */
static svn_boolean_t
found_entry(const svn_fs_x__dirent_t * const *entries,
            const char *name,
            apr_size_t idx)
{
  /* check whether we actually found a match */
  const svn_fs_x__dirent_t *entry =
    svn_temp_deserializer__ptr(entries, (const void *const *)&entries[idx]);
  const char* entry_name =
    svn_temp_deserializer__ptr(entry, (const void *const *)&entry->name);

  return strcmp(entry_name, name) == 0;
}

svn_error_t *
svn_fs_x__extract_dir_entry(void **out,
                            const void *data,
                            apr_size_t data_len,
                            void *baton,
                            apr_pool_t *pool)
{
  const dir_data_t *dir_data = data;
  svn_fs_x__ede_baton_t *b = baton;
  svn_boolean_t found;
  apr_size_t pos;

  /* resolve the reference to the entries array */
  const svn_fs_x__dirent_t * const *entries =
    svn_temp_deserializer__ptr(data, (const void *const *)&dir_data->entries);

  /* resolve the reference to the lengths array */
  const apr_uint32_t *lengths =
    svn_temp_deserializer__ptr(data, (const void *const *)&dir_data->lengths);

  /* Before we return, make sure we tell the caller this data is even still
     relevant. */
  b->out_of_date = dir_data->txn_filesize != b->txn_filesize;

  /* Special case: Early out for empty directories.
     That simplifies tests further down the road. */
  *out = NULL;
  if (dir_data->count == 0)
    return SVN_NO_ERROR;

  /* HINT _might_ be the position we hit last time.
     If within valid range, check whether HINT+1 is a hit. */
  if (   b->hint < dir_data->count - 1
      && found_entry(entries, b->name, b->hint + 1))
    {
      /* Got lucky. */
      pos = b->hint + 1;
      found = TRUE;
    }
  else
    {
      /* Binary search for the desired entry by name. */
      pos = find_entry((svn_fs_x__dirent_t **)entries, b->name,
                       dir_data->count, &found);
    }

  /* Remember the hit index - if we FOUND the entry. */
  if (found)
    b->hint = pos;

  /* de-serialize that entry or return NULL, if no match has been found.
   * Be sure to check that the directory contents is still up-to-date. */
  if (found && !b->out_of_date)
    {
      const svn_fs_x__dirent_t *source =
          svn_temp_deserializer__ptr(entries, (const void *const *)&entries[pos]);

      /* Entries have been serialized one-by-one, each time including all
       * nested structures and strings. Therefore, they occupy a single
       * block of memory whose end-offset is either the beginning of the
       * next entry or the end of the buffer
       */
      apr_size_t size = lengths[pos];

      /* copy & deserialize the entry */
      svn_fs_x__dirent_t *new_entry = apr_pmemdup(pool, source, size);

      svn_temp_deserializer__resolve(new_entry, (void **)&new_entry->name);
      *(svn_fs_x__dirent_t **)out = new_entry;
    }

  return SVN_NO_ERROR;
}

/* Utility function for svn_fs_x__replace_dir_entry that implements the
 * modification as a simply deserialize / modify / serialize sequence.
 */
static svn_error_t *
slowly_replace_dir_entry(void **data,
                         apr_size_t *data_len,
                         void *baton,
                         apr_pool_t *pool)
{
  replace_baton_t *replace_baton = (replace_baton_t *)baton;
  dir_data_t *dir_data = (dir_data_t *)*data;
  svn_fs_x__dir_data_t *dir;
  int idx = -1;
  svn_fs_x__dirent_t *entry;
  apr_array_header_t *entries;

  SVN_ERR(svn_fs_x__deserialize_dir_entries((void **)&dir,
                                            *data,
                                            dir_data->len,
                                            pool));

  entries = dir->entries;
  entry = svn_fs_x__find_dir_entry(entries, replace_baton->name, &idx);

  /* Replacement or removal? */
  if (replace_baton->new_entry)
    {
      /* Replace ENTRY with / insert the NEW_ENTRY */
      if (entry)
        APR_ARRAY_IDX(entries, idx, svn_fs_x__dirent_t *)
          = replace_baton->new_entry;
      else
        SVN_ERR(svn_sort__array_insert2(entries, &replace_baton->new_entry, idx));
    }
  else
    {
      /* Remove the old ENTRY. */
      if (entry)
        SVN_ERR(svn_sort__array_delete2(entries, idx, 1));
    }

  return svn_fs_x__serialize_dir_entries(data, data_len, dir, pool);
}

svn_error_t *
svn_fs_x__replace_dir_entry(void **data,
                            apr_size_t *data_len,
                            void *baton,
                            apr_pool_t *pool)
{
  replace_baton_t *replace_baton = (replace_baton_t *)baton;
  dir_data_t *dir_data = (dir_data_t *)*data;
  svn_boolean_t found;
  svn_fs_x__dirent_t **entries;
  apr_uint32_t *lengths;
  apr_uint32_t length;
  apr_size_t pos;

  svn_temp_serializer__context_t *context;

  /* update the cached file length info.
   * Because we are writing to the cache, it is fair to assume that the
   * caller made sure that the current contents is consistent with the
   * previous state of the directory file. */
  dir_data->txn_filesize = replace_baton->txn_filesize;

  /* after quite a number of operations, let's re-pack everything.
   * This is to limit the number of wasted space as we cannot overwrite
   * existing data but must always append. */
  if (dir_data->operations > 2 + dir_data->count / 4)
    return slowly_replace_dir_entry(data, data_len, baton, pool);

  /* resolve the reference to the entries array */
  entries = (svn_fs_x__dirent_t **)
    svn_temp_deserializer__ptr((const char *)dir_data,
                               (const void *const *)&dir_data->entries);

  /* resolve the reference to the lengths array */
  lengths = (apr_uint32_t *)
    svn_temp_deserializer__ptr((const char *)dir_data,
                               (const void *const *)&dir_data->lengths);

  /* binary search for the desired entry by name */
  pos = find_entry(entries, replace_baton->name, dir_data->count, &found);

  /* handle entry removal (if found at all) */
  if (replace_baton->new_entry == NULL)
    {
      if (found)
        {
          /* remove reference to the entry from the index */
          memmove(&entries[pos],
                  &entries[pos + 1],
                  sizeof(entries[pos]) * (dir_data->count - pos));
          memmove(&lengths[pos],
                  &lengths[pos + 1],
                  sizeof(lengths[pos]) * (dir_data->count - pos));

          dir_data->count--;
          dir_data->over_provision++;
          dir_data->operations++;
        }

      return SVN_NO_ERROR;
    }

  /* if not found, prepare to insert the new entry */
  if (!found)
    {
      /* fallback to slow operation if there is no place left to insert an
       * new entry to index. That will automatically give add some spare
       * entries ("overprovision"). */
      if (dir_data->over_provision == 0)
        return slowly_replace_dir_entry(data, data_len, baton, pool);

      /* make entries[index] available for pointing to the new entry */
      memmove(&entries[pos + 1],
              &entries[pos],
              sizeof(entries[pos]) * (dir_data->count - pos));
      memmove(&lengths[pos + 1],
              &lengths[pos],
              sizeof(lengths[pos]) * (dir_data->count - pos));

      dir_data->count++;
      dir_data->over_provision--;
      dir_data->operations++;
    }

  /* de-serialize the new entry */
  entries[pos] = replace_baton->new_entry;
  context = svn_temp_serializer__init_append(dir_data,
                                             entries,
                                             dir_data->len,
                                             *data_len,
                                             pool);
  serialize_dir_entry(context, &entries[pos], &length);

  /* return the updated serialized data */
  SVN_ERR(return_serialized_dir_context(context, data, data_len, TRUE));

  /* since the previous call may have re-allocated the buffer, the lengths
   * pointer may no longer point to the entry in that buffer. Therefore,
   * re-map it again and store the length value after that. */

  dir_data = (dir_data_t *)*data;
  lengths = (apr_uint32_t *)
    svn_temp_deserializer__ptr((const char *)dir_data,
                               (const void *const *)&dir_data->lengths);
  lengths[pos] = length;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__reset_txn_filesize(void **data,
                             apr_size_t *data_len,
                             void *baton,
                             apr_pool_t *pool)
{
  dir_data_t *dir_data = (dir_data_t *)*data;
  dir_data->txn_filesize = SVN_INVALID_FILESIZE;

  return SVN_NO_ERROR;
}

svn_error_t  *
svn_fs_x__serialize_rep_header(void **data,
                               apr_size_t *data_len,
                               void *in,
                               apr_pool_t *pool)
{
  *data_len = sizeof(svn_fs_x__rep_header_t);
  *data = in;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__deserialize_rep_header(void **out,
                                 void *data,
                                 apr_size_t data_len,
                                 apr_pool_t *result_pool)
{
  *out = data;

  return SVN_NO_ERROR;
}

/* Utility function to serialize change CHANGE_P in the given serialization
 * CONTEXT.
 */
static void
serialize_change(svn_temp_serializer__context_t *context,
                 svn_fs_x__change_t * const *change_p)
{
  const svn_fs_x__change_t * change = *change_p;
  if (change == NULL)
    return;

  /* serialize the change struct itself */
  svn_temp_serializer__push(context,
                            (const void * const *)change_p,
                            sizeof(*change));

  /* serialize sub-structures */
  svn_temp_serializer__add_string(context, &change->path.data);
  svn_temp_serializer__add_string(context, &change->copyfrom_path);

  /* return to the caller's nesting level */
  svn_temp_serializer__pop(context);
}

/* Utility function to serialize the CHANGE_P within the given
 * serialization CONTEXT.
 */
static void
deserialize_change(void *buffer,
                   svn_fs_x__change_t **change_p)
{
  svn_fs_x__change_t * change;

  /* fix-up of the pointer to the struct in question */
  svn_temp_deserializer__resolve(buffer, (void **)change_p);

  change = *change_p;
  if (change == NULL)
    return;

  /* fix-up of sub-structures */
  svn_temp_deserializer__resolve(change, (void **)&change->path.data);
  svn_temp_deserializer__resolve(change, (void **)&change->copyfrom_path);
}

svn_error_t *
svn_fs_x__serialize_changes(void **data,
                            apr_size_t *data_len,
                            void *in,
                            apr_pool_t *pool)
{
  svn_fs_x__changes_list_t *changes = in;
  svn_temp_serializer__context_t *context;
  svn_stringbuf_t *serialized;
  int i;

  /* serialize it and all its elements */
  context = svn_temp_serializer__init(changes,
                                      sizeof(*changes),
                                      changes->count * 250,
                                      pool);

  svn_temp_serializer__push(context,
                            (const void * const *)&changes->changes,
                            changes->count * sizeof(*changes->changes));

  for (i = 0; i < changes->count; ++i)
    serialize_change(context, &changes->changes[i]);

  svn_temp_serializer__pop(context);

  /* return the serialized result */
  serialized = svn_temp_serializer__get(context);

  *data = serialized->data;
  *data_len = serialized->len;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_fs_x__deserialize_changes(void **out,
                              void *data,
                              apr_size_t data_len,
                              apr_pool_t *result_pool)
{
  int i;
  svn_fs_x__changes_list_t *changes = (svn_fs_x__changes_list_t *)data;

  /* de-serialize our auxiliary data structure */
  svn_temp_deserializer__resolve(changes, (void**)&changes->changes);

  /* de-serialize each entry and add it to the array */
  for (i = 0; i < changes->count; ++i)
    deserialize_change(changes->changes,
                       (svn_fs_x__change_t **)&changes->changes[i]);

  /* done */
  *out = changes;

  return SVN_NO_ERROR;
}