File: gvariant-core.c

package info (click to toggle)
glib2.0 2.58.3-2+deb10u2
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, buster-backports, sid
  • size: 48,956 kB
  • sloc: ansic: 452,656; xml: 16,781; python: 6,149; makefile: 3,776; sh: 1,499; perl: 1,140; cpp: 9
file content (1155 lines) | stat: -rw-r--r-- 36,980 bytes parent folder | download
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
/*
 * Copyright © 2007, 2008 Ryan Lortie
 * Copyright © 2010 Codethink Limited
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include <glib/gvariant-core.h>

#include <glib/gvariant-internal.h>
#include <glib/gvariant-serialiser.h>
#include <glib/gtestutils.h>
#include <glib/gbitlock.h>
#include <glib/gatomic.h>
#include <glib/gbytes.h>
#include <glib/gslice.h>
#include <glib/gmem.h>
#include <string.h>


/*
 * This file includes the structure definition for GVariant and a small
 * set of functions that are allowed to access the structure directly.
 *
 * This minimises the amount of code that can possibly touch a GVariant
 * structure directly to a few simple fundamental operations.  These few
 * operations are written to be completely threadsafe with respect to
 * all possible outside access.  This means that we only need to be
 * concerned about thread safety issues in this one small file.
 *
 * Most GVariant API functions are in gvariant.c.
 */

/**
 * GVariant:
 *
 * #GVariant is an opaque data structure and can only be accessed
 * using the following functions.
 *
 * Since: 2.24
 **/
struct _GVariant
/* see below for field member documentation */
{
  GVariantTypeInfo *type_info;
  gsize size;

  union
  {
    struct
    {
      GBytes *bytes;
      gconstpointer data;
    } serialised;

    struct
    {
      GVariant **children;
      gsize n_children;
    } tree;
  } contents;

  gint state;
  gint ref_count;
  gsize depth;
};

/* struct GVariant:
 *
 * There are two primary forms of GVariant instances: "serialised form"
 * and "tree form".
 *
 * "serialised form": A serialised GVariant instance stores its value in
 *                    the GVariant serialisation format.  All
 *                    basic-typed instances (ie: non-containers) are in
 *                    serialised format, as are some containers.
 *
 * "tree form": Some containers are in "tree form".  In this case,
 *              instead of containing the serialised data for the
 *              container, the instance contains an array of pointers to
 *              the child values of the container (thus forming a tree).
 *
 * It is possible for an instance to transition from tree form to
 * serialised form.  This happens, implicitly, if the serialised data is
 * requested (eg: via g_variant_get_data()).  Serialised form instances
 * never transition into tree form.
 *
 *
 * The fields of the structure are documented here:
 *
 * type_info: this is a reference to a GVariantTypeInfo describing the
 *            type of the instance.  When the instance is freed, this
 *            reference must be released with g_variant_type_info_unref().
 *
 *            The type_info field never changes during the life of the
 *            instance, so it can be accessed without a lock.
 *
 * size: this is the size of the serialised form for the instance, if it
 *       is known.  If the instance is in serialised form then it is, by
 *       definition, known.  If the instance is in tree form then it may
 *       be unknown (in which case it is -1).  It is possible for the
 *       size to be known when in tree form if, for example, the user
 *       has called g_variant_get_size() without calling
 *       g_variant_get_data().  Additionally, even when the user calls
 *       g_variant_get_data() the size of the data must first be
 *       determined so that a large enough buffer can be allocated for
 *       the data.
 *
 *       Once the size is known, it can never become unknown again.
 *       g_variant_ensure_size() is used to ensure that the size is in
 *       the known state -- it calculates the size if needed.  After
 *       that, the size field can be accessed without a lock.
 *
 * contents: a union containing either the information associated with
 *           holding a value in serialised form or holding a value in
 *           tree form.
 *
 *   .serialised: Only valid when the instance is in serialised form.
 *
 *                Since an instance can never transition away from
 *                serialised form, once these fields are set, they will
 *                never be changed.  It is therefore valid to access
 *                them without holding a lock.
 *
 *     .bytes:  the #GBytes that contains the memory pointed to by
 *              .data, or %NULL if .data is %NULL.  In the event that
 *              the instance was deserialised from another instance,
 *              then the bytes will be shared by both of them.  When
 *              the instance is freed, this reference must be released
 *              with g_bytes_unref().
 *
 *     .data: the serialised data (of size 'size') of the instance.
 *            This pointer should not be freed or modified in any way.
 *            #GBytes is responsible for memory management.
 *
 *            This pointer may be %NULL in two cases:
 *
 *              - if the serialised size of the instance is 0
 *
 *              - if the instance is of a fixed-sized type and was
 *                deserialised out of a corrupted container such that
 *                the container contains too few bytes to point to the
 *                entire proper fixed-size of this instance.  In this
 *                case, 'size' will still be equal to the proper fixed
 *                size, but this pointer will be %NULL.  This is exactly
 *                the reason that g_variant_get_data() sometimes returns
 *                %NULL.  For all other calls, the effect should be as
 *                if .data pointed to the appropriate number of nul
 *                bytes.
 *
 *   .tree: Only valid when the instance is in tree form.
 *
 *          Note that accesses from other threads could result in
 *          conversion of the instance from tree form to serialised form
 *          at any time.  For this reason, the instance lock must always
 *          be held while performing any operations on 'contents.tree'.
 *
 *     .children: the array of the child instances of this instance.
 *                When the instance is freed (or converted to serialised
 *                form) then each child must have g_variant_unref()
 *                called on it and the array must be freed using
 *                g_free().
 *
 *     .n_children: the number of items in the .children array.
 *
 * state: a bitfield describing the state of the instance.  It is a
 *        bitwise-or of the following STATE_* constants:
 *
 *    STATE_LOCKED: the instance lock is held.  This is the bit used by
 *                  g_bit_lock().
 *
 *    STATE_SERIALISED: the instance is in serialised form.  If this
 *                      flag is not set then the instance is in tree
 *                      form.
 *
 *    STATE_TRUSTED: for serialised form instances, this means that the
 *                   serialised data is known to be in normal form (ie:
 *                   not corrupted).
 *
 *                   For tree form instances, this means that all of the
 *                   child instances in the contents.tree.children array
 *                   are trusted.  This means that if the container is
 *                   serialised then the resulting data will be in
 *                   normal form.
 *
 *                   If this flag is unset it does not imply that the
 *                   data is corrupted.  It merely means that we're not
 *                   sure that it's valid.  See g_variant_is_trusted().
 *
 *    STATE_FLOATING: if this flag is set then the object has a floating
 *                    reference.  See g_variant_ref_sink().
 *
 * ref_count: the reference count of the instance
 *
 * depth: the depth of the GVariant in a hierarchy of nested containers,
 *        increasing with the level of nesting. The top-most GVariant has depth
 *        zero.  This is used to avoid recursing too deeply and overflowing the
 *        stack when handling deeply nested untrusted serialised GVariants.
 */
#define STATE_LOCKED     1
#define STATE_SERIALISED 2
#define STATE_TRUSTED    4
#define STATE_FLOATING   8

/* -- private -- */
/* < private >
 * g_variant_lock:
 * @value: a #GVariant
 *
 * Locks @value for performing sensitive operations.
 */
static void
g_variant_lock (GVariant *value)
{
  g_bit_lock (&value->state, 0);
}

/* < private >
 * g_variant_unlock:
 * @value: a #GVariant
 *
 * Unlocks @value after performing sensitive operations.
 */
static void
g_variant_unlock (GVariant *value)
{
  g_bit_unlock (&value->state, 0);
}

/* < private >
 * g_variant_release_children:
 * @value: a #GVariant
 *
 * Releases the reference held on each child in the 'children' array of
 * @value and frees the array itself.  @value must be in tree form.
 *
 * This is done when freeing a tree-form instance or converting it to
 * serialised form.
 *
 * The current thread must hold the lock on @value.
 */
static void
g_variant_release_children (GVariant *value)
{
  gsize i;

  g_assert (value->state & STATE_LOCKED);
  g_assert (~value->state & STATE_SERIALISED);

  for (i = 0; i < value->contents.tree.n_children; i++)
    g_variant_unref (value->contents.tree.children[i]);

  g_free (value->contents.tree.children);
}

/* This begins the main body of the recursive serialiser.
 *
 * There are 3 functions here that work as a team with the serialiser to
 * get things done.  g_variant_store() has a trivial role, but as a
 * public API function, it has its definition elsewhere.
 *
 * Note that "serialisation" of an instance does not mean that the
 * instance is converted to serialised form -- it means that the
 * serialised form of an instance is written to an external buffer.
 * g_variant_ensure_serialised() (which is not part of this set of
 * functions) is the function that is responsible for converting an
 * instance to serialised form.
 *
 * We are only concerned here with container types since non-container
 * instances are always in serialised form.  For these instances,
 * storing their serialised form merely involves a memcpy().
 *
 * Serialisation is a two-step process.  First, the size of the
 * serialised data must be calculated so that an appropriately-sized
 * buffer can be allocated.  Second, the data is written into the
 * buffer.
 *
 * Determining the size:
 *   The process of determining the size is triggered by a call to
 *   g_variant_ensure_size() on a container.  This invokes the
 *   serialiser code to determine the size.  The serialiser is passed
 *   g_variant_fill_gvs() as a callback.
 *
 *   g_variant_fill_gvs() is called by the serialiser on each child of
 *   the container which, in turn, calls g_variant_ensure_size() on
 *   itself and fills in the result of its own size calculation.
 *
 *   The serialiser uses the size information from the children to
 *   calculate the size needed for the entire container.
 *
 * Writing the data:
 *   After the buffer has been allocated, g_variant_serialise() is
 *   called on the container.  This invokes the serialiser code to write
 *   the bytes to the container.  The serialiser is, again, passed
 *   g_variant_fill_gvs() as a callback.
 *
 *   This time, when g_variant_fill_gvs() is called for each child, the
 *   child is given a pointer to a sub-region of the allocated buffer
 *   where it should write its data.  This is done by calling
 *   g_variant_store().  In the event that the instance is in serialised
 *   form this means a memcpy() of the serialised data into the
 *   allocated buffer.  In the event that the instance is in tree form
 *   this means a recursive call back into g_variant_serialise().
 *
 *
 * The forward declaration here allows corecursion via callback:
 */
static void g_variant_fill_gvs (GVariantSerialised *, gpointer);

/* < private >
 * g_variant_ensure_size:
 * @value: a #GVariant
 *
 * Ensures that the ->size field of @value is filled in properly.  This
 * must be done as a precursor to any serialisation of the value in
 * order to know how large of a buffer is needed to store the data.
 *
 * The current thread must hold the lock on @value.
 */
static void
g_variant_ensure_size (GVariant *value)
{
  g_assert (value->state & STATE_LOCKED);

  if (value->size == (gssize) -1)
    {
      gpointer *children;
      gsize n_children;

      children = (gpointer *) value->contents.tree.children;
      n_children = value->contents.tree.n_children;
      value->size = g_variant_serialiser_needed_size (value->type_info,
                                                      g_variant_fill_gvs,
                                                      children, n_children);
    }
}

/* < private >
 * g_variant_serialise:
 * @value: a #GVariant
 * @data: an appropriately-sized buffer
 *
 * Serialises @value into @data.  @value must be in tree form.
 *
 * No change is made to @value.
 *
 * The current thread must hold the lock on @value.
 */
static void
g_variant_serialise (GVariant *value,
                     gpointer  data)
{
  GVariantSerialised serialised = { 0, };
  gpointer *children;
  gsize n_children;

  g_assert (~value->state & STATE_SERIALISED);
  g_assert (value->state & STATE_LOCKED);

  serialised.type_info = value->type_info;
  serialised.size = value->size;
  serialised.data = data;
  serialised.depth = value->depth;

  children = (gpointer *) value->contents.tree.children;
  n_children = value->contents.tree.n_children;

  g_variant_serialiser_serialise (serialised, g_variant_fill_gvs,
                                  children, n_children);
}

/* < private >
 * g_variant_fill_gvs:
 * @serialised: a pointer to a #GVariantSerialised
 * @data: a #GVariant instance
 *
 * This is the callback that is passed by a tree-form container instance
 * to the serialiser.  This callback gets called on each child of the
 * container.  Each child is responsible for performing the following
 * actions:
 *
 *  - reporting its type
 *
 *  - reporting its serialised size (requires knowing the size first)
 *
 *  - possibly storing its serialised form into the provided buffer
 */
static void
g_variant_fill_gvs (GVariantSerialised *serialised,
                    gpointer            data)
{
  GVariant *value = data;

  g_variant_lock (value);
  g_variant_ensure_size (value);
  g_variant_unlock (value);

  if (serialised->type_info == NULL)
    serialised->type_info = value->type_info;
  g_assert (serialised->type_info == value->type_info);

  if (serialised->size == 0)
    serialised->size = value->size;
  g_assert (serialised->size == value->size);
  serialised->depth = value->depth;

  if (serialised->data)
    /* g_variant_store() is a public API, so it
     * it will reacquire the lock if it needs to.
     */
    g_variant_store (value, serialised->data);
}

/* this ends the main body of the recursive serialiser */

/* < private >
 * g_variant_ensure_serialised:
 * @value: a #GVariant
 *
 * Ensures that @value is in serialised form.
 *
 * If @value is in tree form then this function ensures that the
 * serialised size is known and then allocates a buffer of that size and
 * serialises the instance into the buffer.  The 'children' array is
 * then released and the instance is set to serialised form based on the
 * contents of the buffer.
 *
 * The current thread must hold the lock on @value.
 */
static void
g_variant_ensure_serialised (GVariant *value)
{
  g_assert (value->state & STATE_LOCKED);

  if (~value->state & STATE_SERIALISED)
    {
      GBytes *bytes;
      gpointer data;

      g_variant_ensure_size (value);
      data = g_malloc (value->size);
      g_variant_serialise (value, data);

      g_variant_release_children (value);

      bytes = g_bytes_new_take (data, value->size);
      value->contents.serialised.data = g_bytes_get_data (bytes, NULL);
      value->contents.serialised.bytes = bytes;
      value->state |= STATE_SERIALISED;
    }
}

/* < private >
 * g_variant_alloc:
 * @type: the type of the new instance
 * @serialised: if the instance will be in serialised form
 * @trusted: if the instance will be trusted
 *
 * Allocates a #GVariant instance and does some common work (such as
 * looking up and filling in the type info), setting the state field,
 * and setting the ref_count to 1.
 *
 * Returns: a new #GVariant with a floating reference
 */
static GVariant *
g_variant_alloc (const GVariantType *type,
                 gboolean            serialised,
                 gboolean            trusted)
{
  GVariant *value;

  value = g_slice_new (GVariant);
  value->type_info = g_variant_type_info_get (type);
  value->state = (serialised ? STATE_SERIALISED : 0) |
                 (trusted ? STATE_TRUSTED : 0) |
                 STATE_FLOATING;
  value->size = (gssize) -1;
  value->ref_count = 1;
  value->depth = 0;

  return value;
}

/**
 * g_variant_new_from_bytes:
 * @type: a #GVariantType
 * @bytes: a #GBytes
 * @trusted: if the contents of @bytes are trusted
 *
 * Constructs a new serialised-mode #GVariant instance.  This is the
 * inner interface for creation of new serialised values that gets
 * called from various functions in gvariant.c.
 *
 * A reference is taken on @bytes.
 *
 * Returns: (transfer none): a new #GVariant with a floating reference
 *
 * Since: 2.36
 */
GVariant *
g_variant_new_from_bytes (const GVariantType *type,
                          GBytes             *bytes,
                          gboolean            trusted)
{
  GVariant *value;
  guint alignment;
  gsize size;

  value = g_variant_alloc (type, TRUE, trusted);

  value->contents.serialised.bytes = g_bytes_ref (bytes);

  g_variant_type_info_query (value->type_info,
                             &alignment, &size);

  if (size && g_bytes_get_size (bytes) != size)
    {
      /* Creating a fixed-sized GVariant with a bytes of the wrong
       * size.
       *
       * We should do the equivalent of pulling a fixed-sized child out
       * of a brozen container (ie: data is NULL size is equal to the correct
       * fixed size).
       */
      value->contents.serialised.data = NULL;
      value->size = size;
    }
  else
    {
      value->contents.serialised.data = g_bytes_get_data (bytes, &value->size);
    }

  return value;
}

/* -- internal -- */

/* < internal >
 * g_variant_new_from_children:
 * @type: a #GVariantType
 * @children: an array of #GVariant pointers.  Consumed.
 * @n_children: the length of @children
 * @trusted: %TRUE if every child in @children in trusted
 *
 * Constructs a new tree-mode #GVariant instance.  This is the inner
 * interface for creation of new serialised values that gets called from
 * various functions in gvariant.c.
 *
 * @children is consumed by this function.  g_free() will be called on
 * it some time later.
 *
 * Returns: a new #GVariant with a floating reference
 */
GVariant *
g_variant_new_from_children (const GVariantType  *type,
                             GVariant           **children,
                             gsize                n_children,
                             gboolean             trusted)
{
  GVariant *value;

  value = g_variant_alloc (type, FALSE, trusted);
  value->contents.tree.children = children;
  value->contents.tree.n_children = n_children;

  return value;
}

/* < internal >
 * g_variant_get_type_info:
 * @value: a #GVariant
 *
 * Returns the #GVariantTypeInfo corresponding to the type of @value.  A
 * reference is not added, so the return value is only good for the
 * duration of the life of @value.
 *
 * Returns: the #GVariantTypeInfo for @value
 */
GVariantTypeInfo *
g_variant_get_type_info (GVariant *value)
{
  return value->type_info;
}

/* < internal >
 * g_variant_is_trusted:
 * @value: a #GVariant
 *
 * Determines if @value is trusted by #GVariant to contain only
 * fully-valid data.  All values constructed solely via #GVariant APIs
 * are trusted, but values containing data read in from other sources
 * are usually not trusted.
 *
 * The main advantage of trusted data is that certain checks can be
 * skipped.  For example, we don't need to check that a string is
 * properly nul-terminated or that an object path is actually a
 * properly-formatted object path.
 *
 * Returns: if @value is trusted
 */
gboolean
g_variant_is_trusted (GVariant *value)
{
  return (value->state & STATE_TRUSTED) != 0;
}

/* -- public -- */

/**
 * g_variant_unref:
 * @value: a #GVariant
 *
 * Decreases the reference count of @value.  When its reference count
 * drops to 0, the memory used by the variant is freed.
 *
 * Since: 2.24
 **/
void
g_variant_unref (GVariant *value)
{
  g_return_if_fail (value != NULL);
  g_return_if_fail (value->ref_count > 0);

  if (g_atomic_int_dec_and_test (&value->ref_count))
    {
      if G_UNLIKELY (value->state & STATE_LOCKED)
        g_critical ("attempting to free a locked GVariant instance.  "
                    "This should never happen.");

      value->state |= STATE_LOCKED;

      g_variant_type_info_unref (value->type_info);

      if (value->state & STATE_SERIALISED)
        g_bytes_unref (value->contents.serialised.bytes);
      else
        g_variant_release_children (value);

      memset (value, 0, sizeof (GVariant));
      g_slice_free (GVariant, value);
    }
}

/**
 * g_variant_ref:
 * @value: a #GVariant
 *
 * Increases the reference count of @value.
 *
 * Returns: the same @value
 *
 * Since: 2.24
 **/
GVariant *
g_variant_ref (GVariant *value)
{
  g_return_val_if_fail (value != NULL, NULL);
  g_return_val_if_fail (value->ref_count > 0, NULL);

  g_atomic_int_inc (&value->ref_count);

  return value;
}

/**
 * g_variant_ref_sink:
 * @value: a #GVariant
 *
 * #GVariant uses a floating reference count system.  All functions with
 * names starting with `g_variant_new_` return floating
 * references.
 *
 * Calling g_variant_ref_sink() on a #GVariant with a floating reference
 * will convert the floating reference into a full reference.  Calling
 * g_variant_ref_sink() on a non-floating #GVariant results in an
 * additional normal reference being added.
 *
 * In other words, if the @value is floating, then this call "assumes
 * ownership" of the floating reference, converting it to a normal
 * reference.  If the @value is not floating, then this call adds a
 * new normal reference increasing the reference count by one.
 *
 * All calls that result in a #GVariant instance being inserted into a
 * container will call g_variant_ref_sink() on the instance.  This means
 * that if the value was just created (and has only its floating
 * reference) then the container will assume sole ownership of the value
 * at that point and the caller will not need to unreference it.  This
 * makes certain common styles of programming much easier while still
 * maintaining normal refcounting semantics in situations where values
 * are not floating.
 *
 * Returns: the same @value
 *
 * Since: 2.24
 **/
GVariant *
g_variant_ref_sink (GVariant *value)
{
  g_return_val_if_fail (value != NULL, NULL);
  g_return_val_if_fail (value->ref_count > 0, NULL);

  g_variant_lock (value);

  if (~value->state & STATE_FLOATING)
    g_variant_ref (value);
  else
    value->state &= ~STATE_FLOATING;

  g_variant_unlock (value);

  return value;
}

/**
 * g_variant_take_ref:
 * @value: a #GVariant
 *
 * If @value is floating, sink it.  Otherwise, do nothing.
 *
 * Typically you want to use g_variant_ref_sink() in order to
 * automatically do the correct thing with respect to floating or
 * non-floating references, but there is one specific scenario where
 * this function is helpful.
 *
 * The situation where this function is helpful is when creating an API
 * that allows the user to provide a callback function that returns a
 * #GVariant.  We certainly want to allow the user the flexibility to
 * return a non-floating reference from this callback (for the case
 * where the value that is being returned already exists).
 *
 * At the same time, the style of the #GVariant API makes it likely that
 * for newly-created #GVariant instances, the user can be saved some
 * typing if they are allowed to return a #GVariant with a floating
 * reference.
 *
 * Using this function on the return value of the user's callback allows
 * the user to do whichever is more convenient for them.  The caller
 * will alway receives exactly one full reference to the value: either
 * the one that was returned in the first place, or a floating reference
 * that has been converted to a full reference.
 *
 * This function has an odd interaction when combined with
 * g_variant_ref_sink() running at the same time in another thread on
 * the same #GVariant instance.  If g_variant_ref_sink() runs first then
 * the result will be that the floating reference is converted to a hard
 * reference.  If g_variant_take_ref() runs first then the result will
 * be that the floating reference is converted to a hard reference and
 * an additional reference on top of that one is added.  It is best to
 * avoid this situation.
 *
 * Returns: the same @value
 **/
GVariant *
g_variant_take_ref (GVariant *value)
{
  g_return_val_if_fail (value != NULL, NULL);
  g_return_val_if_fail (value->ref_count > 0, NULL);

  g_atomic_int_and (&value->state, ~STATE_FLOATING);

  return value;
}

/**
 * g_variant_is_floating:
 * @value: a #GVariant
 *
 * Checks whether @value has a floating reference count.
 *
 * This function should only ever be used to assert that a given variant
 * is or is not floating, or for debug purposes. To acquire a reference
 * to a variant that might be floating, always use g_variant_ref_sink()
 * or g_variant_take_ref().
 *
 * See g_variant_ref_sink() for more information about floating reference
 * counts.
 *
 * Returns: whether @value is floating
 *
 * Since: 2.26
 **/
gboolean
g_variant_is_floating (GVariant *value)
{
  g_return_val_if_fail (value != NULL, FALSE);

  return (value->state & STATE_FLOATING) != 0;
}

/**
 * g_variant_get_size:
 * @value: a #GVariant instance
 *
 * Determines the number of bytes that would be required to store @value
 * with g_variant_store().
 *
 * If @value has a fixed-sized type then this function always returned
 * that fixed size.
 *
 * In the case that @value is already in serialised form or the size has
 * already been calculated (ie: this function has been called before)
 * then this function is O(1).  Otherwise, the size is calculated, an
 * operation which is approximately O(n) in the number of values
 * involved.
 *
 * Returns: the serialised size of @value
 *
 * Since: 2.24
 **/
gsize
g_variant_get_size (GVariant *value)
{
  g_variant_lock (value);
  g_variant_ensure_size (value);
  g_variant_unlock (value);

  return value->size;
}

/**
 * g_variant_get_data:
 * @value: a #GVariant instance
 *
 * Returns a pointer to the serialised form of a #GVariant instance.
 * The returned data may not be in fully-normalised form if read from an
 * untrusted source.  The returned data must not be freed; it remains
 * valid for as long as @value exists.
 *
 * If @value is a fixed-sized value that was deserialised from a
 * corrupted serialised container then %NULL may be returned.  In this
 * case, the proper thing to do is typically to use the appropriate
 * number of nul bytes in place of @value.  If @value is not fixed-sized
 * then %NULL is never returned.
 *
 * In the case that @value is already in serialised form, this function
 * is O(1).  If the value is not already in serialised form,
 * serialisation occurs implicitly and is approximately O(n) in the size
 * of the result.
 *
 * To deserialise the data returned by this function, in addition to the
 * serialised data, you must know the type of the #GVariant, and (if the
 * machine might be different) the endianness of the machine that stored
 * it. As a result, file formats or network messages that incorporate
 * serialised #GVariants must include this information either
 * implicitly (for instance "the file always contains a
 * %G_VARIANT_TYPE_VARIANT and it is always in little-endian order") or
 * explicitly (by storing the type and/or endianness in addition to the
 * serialised data).
 *
 * Returns: (transfer none): the serialised form of @value, or %NULL
 *
 * Since: 2.24
 **/
gconstpointer
g_variant_get_data (GVariant *value)
{
  g_variant_lock (value);
  g_variant_ensure_serialised (value);
  g_variant_unlock (value);

  return value->contents.serialised.data;
}

/**
 * g_variant_get_data_as_bytes:
 * @value: a #GVariant
 *
 * Returns a pointer to the serialised form of a #GVariant instance.
 * The semantics of this function are exactly the same as
 * g_variant_get_data(), except that the returned #GBytes holds
 * a reference to the variant data.
 *
 * Returns: (transfer full): A new #GBytes representing the variant data
 *
 * Since: 2.36
 */ 
GBytes *
g_variant_get_data_as_bytes (GVariant *value)
{
  const gchar *bytes_data;
  const gchar *data;
  gsize bytes_size;
  gsize size;

  g_variant_lock (value);
  g_variant_ensure_serialised (value);
  g_variant_unlock (value);

  bytes_data = g_bytes_get_data (value->contents.serialised.bytes, &bytes_size);
  data = value->contents.serialised.data;
  size = value->size;

  if (data == bytes_data && size == bytes_size)
    return g_bytes_ref (value->contents.serialised.bytes);
  else
    return g_bytes_new_from_bytes (value->contents.serialised.bytes,
                                   data - bytes_data, size);
}


/**
 * g_variant_n_children:
 * @value: a container #GVariant
 *
 * Determines the number of children in a container #GVariant instance.
 * This includes variants, maybes, arrays, tuples and dictionary
 * entries.  It is an error to call this function on any other type of
 * #GVariant.
 *
 * For variants, the return value is always 1.  For values with maybe
 * types, it is always zero or one.  For arrays, it is the length of the
 * array.  For tuples it is the number of tuple items (which depends
 * only on the type).  For dictionary entries, it is always 2
 *
 * This function is O(1).
 *
 * Returns: the number of children in the container
 *
 * Since: 2.24
 **/
gsize
g_variant_n_children (GVariant *value)
{
  gsize n_children;

  g_variant_lock (value);

  if (value->state & STATE_SERIALISED)
    {
      GVariantSerialised serialised = {
        value->type_info,
        (gpointer) value->contents.serialised.data,
        value->size,
        value->depth,
      };

      n_children = g_variant_serialised_n_children (serialised);
    }
  else
    n_children = value->contents.tree.n_children;

  g_variant_unlock (value);

  return n_children;
}

/**
 * g_variant_get_child_value:
 * @value: a container #GVariant
 * @index_: the index of the child to fetch
 *
 * Reads a child item out of a container #GVariant instance.  This
 * includes variants, maybes, arrays, tuples and dictionary
 * entries.  It is an error to call this function on any other type of
 * #GVariant.
 *
 * It is an error if @index_ is greater than the number of child items
 * in the container.  See g_variant_n_children().
 *
 * The returned value is never floating.  You should free it with
 * g_variant_unref() when you're done with it.
 *
 * There may be implementation specific restrictions on deeply nested values,
 * which would result in the unit tuple being returned as the child value,
 * instead of further nested children. #GVariant is guaranteed to handle
 * nesting up to at least 64 levels.
 *
 * This function is O(1).
 *
 * Returns: (transfer full): the child at the specified index
 *
 * Since: 2.24
 **/
GVariant *
g_variant_get_child_value (GVariant *value,
                           gsize     index_)
{
  g_return_val_if_fail (index_ < g_variant_n_children (value), NULL);
  g_return_val_if_fail (value->depth < G_MAXSIZE, NULL);

  if (~g_atomic_int_get (&value->state) & STATE_SERIALISED)
    {
      g_variant_lock (value);

      if (~value->state & STATE_SERIALISED)
        {
          GVariant *child;

          child = g_variant_ref (value->contents.tree.children[index_]);
          g_variant_unlock (value);

          return child;
        }

      g_variant_unlock (value);
    }

  {
    GVariantSerialised serialised = {
      value->type_info,
      (gpointer) value->contents.serialised.data,
      value->size,
      value->depth,
    };
    GVariantSerialised s_child;
    GVariant *child;

    /* get the serialiser to extract the serialised data for the child
     * from the serialised data for the container
     */
    s_child = g_variant_serialised_get_child (serialised, index_);

    /* Check whether this would cause nesting too deep. If so, return a fake
     * child. The only situation we expect this to happen in is with a variant,
     * as all other deeply-nested types have a static type, and hence should
     * have been rejected earlier. In the case of a variant whose nesting plus
     * the depth of its child is too great, return a unit variant () instead of
     * the real child. */
    if (!(value->state & STATE_TRUSTED) &&
        g_variant_type_info_query_depth (s_child.type_info) >=
        G_VARIANT_MAX_RECURSION_DEPTH - value->depth)
      {
        g_assert (g_variant_is_of_type (value, G_VARIANT_TYPE_VARIANT));
        return g_variant_new_tuple (NULL, 0);
      }

    /* create a new serialised instance out of it */
    child = g_slice_new (GVariant);
    child->type_info = s_child.type_info;
    child->state = (value->state & STATE_TRUSTED) |
                   STATE_SERIALISED;
    child->size = s_child.size;
    child->ref_count = 1;
    child->depth = value->depth + 1;
    child->contents.serialised.bytes =
      g_bytes_ref (value->contents.serialised.bytes);
    child->contents.serialised.data = s_child.data;

    return child;
  }
}

/**
 * g_variant_store:
 * @value: the #GVariant to store
 * @data: (not nullable): the location to store the serialised data at
 *
 * Stores the serialised form of @value at @data.  @data should be
 * large enough.  See g_variant_get_size().
 *
 * The stored data is in machine native byte order but may not be in
 * fully-normalised form if read from an untrusted source.  See
 * g_variant_get_normal_form() for a solution.
 *
 * As with g_variant_get_data(), to be able to deserialise the
 * serialised variant successfully, its type and (if the destination
 * machine might be different) its endianness must also be available.
 *
 * This function is approximately O(n) in the size of @data.
 *
 * Since: 2.24
 **/
void
g_variant_store (GVariant *value,
                 gpointer  data)
{
  g_variant_lock (value);

  if (value->state & STATE_SERIALISED)
    {
      if (value->contents.serialised.data != NULL)
        memcpy (data, value->contents.serialised.data, value->size);
      else
        memset (data, 0, value->size);
    }
  else
    g_variant_serialise (value, data);

  g_variant_unlock (value);
}

/**
 * g_variant_is_normal_form:
 * @value: a #GVariant instance
 *
 * Checks if @value is in normal form.
 *
 * The main reason to do this is to detect if a given chunk of
 * serialised data is in normal form: load the data into a #GVariant
 * using g_variant_new_from_data() and then use this function to
 * check.
 *
 * If @value is found to be in normal form then it will be marked as
 * being trusted.  If the value was already marked as being trusted then
 * this function will immediately return %TRUE.
 *
 * There may be implementation specific restrictions on deeply nested values.
 * GVariant is guaranteed to handle nesting up to at least 64 levels.
 *
 * Returns: %TRUE if @value is in normal form
 *
 * Since: 2.24
 **/
gboolean
g_variant_is_normal_form (GVariant *value)
{
  if (value->state & STATE_TRUSTED)
    return TRUE;

  g_variant_lock (value);

  if (value->depth >= G_VARIANT_MAX_RECURSION_DEPTH)
    return FALSE;

  if (value->state & STATE_SERIALISED)
    {
      GVariantSerialised serialised = {
        value->type_info,
        (gpointer) value->contents.serialised.data,
        value->size,
        value->depth
      };

      if (g_variant_serialised_is_normal (serialised))
        value->state |= STATE_TRUSTED;
    }
  else
    {
      gboolean normal = TRUE;
      gsize i;

      for (i = 0; i < value->contents.tree.n_children; i++)
        normal &= g_variant_is_normal_form (value->contents.tree.children[i]);

      if (normal)
        value->state |= STATE_TRUSTED;
    }

  g_variant_unlock (value);

  return (value->state & STATE_TRUSTED) != 0;
}