2 * Copyright © 2007, 2008 Ryan Lortie
3 * Copyright © 2010 Codethink Limited
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
21 #include <glib/gvariant-core.h>
22 #include "glib-private.h"
24 #include <glib/gvariant-serialiser.h>
25 #include <glib/gtestutils.h>
26 #include <glib/gbitlock.h>
27 #include <glib/gatomic.h>
28 #include <glib/gbytes.h>
29 #include <glib/gslice.h>
30 #include <glib/gmem.h>
35 * This file includes the structure definition for GVariant and a small
36 * set of functions that are allowed to access the structure directly.
38 * This minimises the amount of code that can possibly touch a GVariant
39 * structure directly to a few simple fundamental operations. These few
40 * operations are written to be completely threadsafe with respect to
41 * all possible outside access. This means that we only need to be
42 * concerned about thread safety issues in this one small file.
44 * Most GVariant API functions are in gvariant.c.
50 * #GVariant is an opaque data structure and can only be accessed
51 * using the following functions.
56 /* see below for field member documentation */
58 GVariantTypeInfo *type_info;
82 * There are two primary forms of GVariant instances: "serialised form"
85 * "serialised form": A serialised GVariant instance stores its value in
86 * the GVariant serialisation format. All
87 * basic-typed instances (ie: non-containers) are in
88 * serialised format, as are some containers.
90 * "tree form": Some containers are in "tree form". In this case,
91 * instead of containing the serialised data for the
92 * container, the instance contains an array of pointers to
93 * the child values of the container (thus forming a tree).
95 * It is possible for an instance to transition from tree form to
96 * serialised form. This happens, implicitly, if the serialised data is
97 * requested (eg: via g_variant_get_data()). Serialised form instances
98 * never transition into tree form.
101 * The fields of the structure are documented here:
103 * type_info: this is a reference to a GVariantTypeInfo describing the
104 * type of the instance. When the instance is freed, this
105 * reference must be released with g_variant_type_info_unref().
107 * The type_info field never changes during the life of the
108 * instance, so it can be accessed without a lock.
110 * size: this is the size of the serialised form for the instance. It
111 * is known for serialised instances and also tree-form instances
112 * (for which it is calculated at construction time, from the
113 * known sizes of the children used). After construction, it
114 * never changes and therefore can be accessed without a lock.
116 * contents: a union containing either the information associated with
117 * holding a value in serialised form or holding a value in
120 * .serialised: Only valid when the instance is in serialised form.
122 * Since an instance can never transition away from
123 * serialised form, once these fields are set, they will
124 * never be changed. It is therefore valid to access
125 * them without holding a lock.
127 * .bytes: the #GBytes that contains the memory pointed to by
128 * .data, or %NULL if .data is %NULL. In the event that
129 * the instance was deserialised from another instance,
130 * then the bytes will be shared by both of them. When
131 * the instance is freed, this reference must be released
132 * with g_bytes_unref().
134 * .data: the serialised data (of size 'size') of the instance.
135 * This pointer should not be freed or modified in any way.
136 * #GBytes is responsible for memory management.
138 * This pointer may be %NULL in two cases:
140 * - if the serialised size of the instance is 0
142 * - if the instance is of a fixed-sized type and was
143 * deserialised out of a corrupted container such that
144 * the container contains too few bytes to point to the
145 * entire proper fixed-size of this instance. In this
146 * case, 'size' will still be equal to the proper fixed
147 * size, but this pointer will be %NULL. This is exactly
148 * the reason that g_variant_get_data() sometimes returns
149 * %NULL. For all other calls, the effect should be as
150 * if .data pointed to the appropriate number of nul
153 * .tree: Only valid when the instance is in tree form.
155 * Note that accesses from other threads could result in
156 * conversion of the instance from tree form to serialised form
157 * at any time. For this reason, the instance lock must always
158 * be held while performing any operations on 'contents.tree'.
160 * .children: the array of the child instances of this instance.
161 * When the instance is freed (or converted to serialised
162 * form) then each child must have g_variant_unref()
163 * called on it and the array must be freed using
166 * .n_children: the number of items in the .children array.
168 * state: a bitfield describing the state of the instance. It is a
169 * bitwise-or of the following STATE_* constants:
171 * STATE_LOCKED: the instance lock is held. This is the bit used by
174 * STATE_SERIALISED: the instance is in serialised form. If this
175 * flag is not set then the instance is in tree
178 * STATE_TRUSTED: for serialised form instances, this means that the
179 * serialised data is known to be in normal form (ie:
182 * For tree form instances, this means that all of the
183 * child instances in the contents.tree.children array
184 * are trusted. This means that if the container is
185 * serialised then the resulting data will be in
188 * If this flag is unset it does not imply that the
189 * data is corrupted. It merely means that we're not
190 * sure that it's valid. See g_variant_is_trusted().
192 * STATE_FLOATING: if this flag is set then the object has a floating
193 * reference. See g_variant_ref_sink().
195 * ref_count: the reference count of the instance
197 #define STATE_LOCKED 1
198 #define STATE_SERIALISED 2
199 #define STATE_TRUSTED 4
200 #define STATE_FLOATING 8
205 * @value: a #GVariant
207 * Locks @value for performing sensitive operations.
210 g_variant_lock (GVariant *value)
212 g_bit_lock (&value->state, 0);
217 * @value: a #GVariant
219 * Unlocks @value after performing sensitive operations.
222 g_variant_unlock (GVariant *value)
224 g_bit_unlock (&value->state, 0);
228 * g_variant_release_children:
229 * @value: a #GVariant
231 * Releases the reference held on each child in the 'children' array of
232 * @value and frees the array itself. @value must be in tree form.
234 * This is done when freeing a tree-form instance or converting it to
237 * The current thread must hold the lock on @value.
240 g_variant_release_children (GVariant *value)
244 g_assert (value->state & STATE_LOCKED);
245 g_assert (~value->state & STATE_SERIALISED);
247 for (i = 0; i < value->contents.tree.n_children; i++)
248 g_variant_unref (value->contents.tree.children[i]);
250 g_free (value->contents.tree.children);
254 * g_variant_lock_in_tree_form:
255 * @value: a #GVariant
257 * Locks @value if it is in tree form.
259 * Returns: %TRUE if @value is now in tree form with the lock acquired
262 g_variant_lock_in_tree_form (GVariant *value)
264 if (g_atomic_int_get (&value->state) & STATE_SERIALISED)
267 g_variant_lock (value);
269 if (value->state & STATE_SERIALISED)
271 g_variant_unlock (value);
278 /* This begins the main body of the recursive serialiser.
280 * There are 3 functions here that work as a team with the serialiser to
281 * get things done. g_variant_store() has a trivial role, but as a
282 * public API function, it has its definition elsewhere.
284 * Note that "serialisation" of an instance does not mean that the
285 * instance is converted to serialised form -- it means that the
286 * serialised form of an instance is written to an external buffer.
287 * g_variant_ensure_serialised() (which is not part of this set of
288 * functions) is the function that is responsible for converting an
289 * instance to serialised form.
291 * We are only concerned here with container types since non-container
292 * instances are always in serialised form. For these instances,
293 * storing their serialised form merely involves a memcpy().
295 * Converting to serialised form:
297 * The first step in the process of converting a GVariant to
298 * serialised form is to allocate a buffer. The size of the buffer is
299 * always known because we computed at construction time of the
302 * After the buffer has been allocated, g_variant_serialise() is
303 * called on the container. This invokes the serialiser code to write
304 * the bytes to the container. The serialiser is passed
305 * g_variant_fill_gvs() as a callback.
307 * At the time that g_variant_fill_gvs() is called for each child, the
308 * child is given a pointer to a sub-region of the allocated buffer
309 * where it should write its data. This is done by calling
310 * g_variant_store(). In the event that the instance is in serialised
311 * form this means a memcpy() of the serialised data into the
312 * allocated buffer. In the event that the instance is in tree form
313 * this means a recursive call back into g_variant_serialise().
316 * The forward declaration here allows corecursion via callback:
318 static void g_variant_fill_gvs (GVariantSerialised *, gpointer);
321 * g_variant_serialise:
322 * @value: a #GVariant
323 * @data: an appropriately-sized buffer
325 * Serialises @value into @data. @value must be in tree form.
327 * No change is made to @value.
329 * The current thread must hold the lock on @value.
332 g_variant_serialise (GVariant *value,
335 GVariantSerialised serialised = { 0, };
339 g_assert (~value->state & STATE_SERIALISED);
340 g_assert (value->state & STATE_LOCKED);
342 serialised.type_info = value->type_info;
343 serialised.size = value->size;
344 serialised.data = data;
346 children = (gpointer *) value->contents.tree.children;
347 n_children = value->contents.tree.n_children;
349 g_variant_serialiser_serialise (serialised, g_variant_fill_gvs,
350 children, n_children);
354 * g_variant_fill_gvs:
355 * @serialised: a pointer to a #GVariantSerialised
356 * @data: a #GVariant instance
358 * This is the callback that is passed by a tree-form container instance
359 * to the serialiser. This callback gets called on each child of the
360 * container. Each child is responsible for performing the following
363 * - reporting its type
365 * - reporting its serialised size
367 * - possibly storing its serialised form into the provided buffer
369 * This callback is also used during g_variant_new_from_children() in
370 * order to discover the size and type of each child.
373 g_variant_fill_gvs (GVariantSerialised *serialised,
376 GVariant *value = data;
378 if (serialised->type_info == NULL)
379 serialised->type_info = value->type_info;
380 g_assert (serialised->type_info == value->type_info);
382 if (serialised->size == 0)
383 serialised->size = value->size;
384 g_assert (serialised->size == value->size);
386 if (serialised->data)
387 /* g_variant_store() is a public API, so it
388 * it will reacquire the lock if it needs to.
390 g_variant_store (value, serialised->data);
393 /* this ends the main body of the recursive serialiser */
396 * g_variant_ensure_serialised:
397 * @value: a #GVariant
399 * Ensures that @value is in serialised form.
401 * If @value is in tree form then this function allocates a buffer of
402 * that size and serialises the instance into the buffer. The
403 * 'children' array is then released and the instance is set to
404 * serialised form based on the contents of the buffer.
407 g_variant_ensure_serialised (GVariant *value)
409 if (g_variant_lock_in_tree_form (value))
414 data = g_malloc (value->size);
415 g_variant_serialise (value, data);
417 g_variant_release_children (value);
419 bytes = g_bytes_new_take (data, value->size);
420 value->contents.serialised.data = g_bytes_get_data (bytes, NULL);
421 value->contents.serialised.bytes = bytes;
422 value->state |= STATE_SERIALISED;
424 g_variant_unlock (value);
428 /* Now we have the code to recursively serialise a GVariant into a
429 * GVariantVectors structure.
431 * We want to do this in cases where the GVariant contains large chunks
432 * of serialised data in order to avoid having to copy this data.
434 * This generally works the same as normal serialising (co-recursion
435 * with the serialiser) but instead of using a callback we just hard-code
436 * the callback with the name g_variant_callback_write_to_vectors().
438 * This is a private API that will be used by GDBus.
441 g_variant_callback_write_to_vectors (GVariantVectors *vectors,
443 GVariantTypeInfo **type_info)
445 GVariant *value = data;
447 if (g_variant_lock_in_tree_form (value))
449 g_variant_serialiser_write_to_vectors (vectors, value->type_info, value->size,
450 (gpointer *) value->contents.tree.children,
451 value->contents.tree.n_children);
453 g_variant_unlock (value);
456 g_variant_vectors_append_gbytes (vectors, value->contents.serialised.bytes,
457 value->contents.serialised.data, value->size);
460 *type_info = value->type_info;
466 * g_variant_serialise_to_vectors:
467 * @value: a #GVariant
468 * @vectors: (out): the result
470 * Serialises @value into @vectors.
472 * The caller must free @vectors.
475 g_variant_to_vectors (GVariant *value,
476 GVariantVectors *vectors)
478 g_variant_vectors_init (vectors);
480 g_variant_callback_write_to_vectors (vectors, value, NULL);
485 * @type_info: (transfer full) the type info of the new instance
486 * @serialised: if the instance will be in serialised form
487 * @trusted: if the instance will be trusted
489 * Allocates a #GVariant instance and does some common work (such as
490 * looking up and filling in the type info), setting the state field,
491 * and setting the ref_count to 1.
493 * Returns: a new #GVariant with a floating reference
496 g_variant_alloc (GVariantTypeInfo *type_info,
502 value = g_slice_new (GVariant);
503 value->type_info = type_info;
504 value->state = (serialised ? STATE_SERIALISED : 0) |
505 (trusted ? STATE_TRUSTED : 0) |
507 value->ref_count = 1;
515 * g_variant_new_from_children:
516 * @type_info: (transfer full) a #GVariantTypeInfo
517 * @children: an array of #GVariant pointers. Consumed.
518 * @n_children: the length of @children
519 * @trusted: %TRUE if every child in @children in trusted
521 * Constructs a new tree-mode #GVariant instance. This is the inner
522 * interface for creation of new tree-mode values that gets called from
523 * various functions in gvariant.c.
525 * @children is consumed by this function. g_free() will be called on
526 * it some time later.
528 * Returns: a new #GVariant with a floating reference
531 g_variant_new_from_children (GVariantTypeInfo *type_info,
538 value = g_variant_alloc (type_info, FALSE, trusted);
539 value->contents.tree.children = children;
540 value->contents.tree.n_children = n_children;
541 value->size = g_variant_serialiser_needed_size (value->type_info, g_variant_fill_gvs,
542 (gpointer *) children, n_children);
548 * g_variant_new_serialised:
549 * @type_info: (transfer full): a #GVariantTypeInfo
550 * @bytes: (transfer full): the #GBytes holding @data
551 * @data: a pointer to the serialised data
552 * @size: the size of @data, in bytes
553 * @trusted: %TRUE if @data is trusted
555 * Constructs a new serialised #GVariant instance. This is the inner
556 * interface for creation of new serialised values that gets called from
557 * various functions in gvariant.c.
559 * @bytes is consumed by this function. g_bytes_unref() will be called
560 * on it some time later.
562 * Returns: a new #GVariant with a floating reference
565 g_variant_new_serialised (GVariantTypeInfo *type_info,
574 value = g_variant_alloc (type_info, TRUE, trusted);
575 value->contents.serialised.bytes = bytes;
576 value->contents.serialised.data = data;
579 g_variant_type_info_query (value->type_info, NULL, &fixed_size);
580 if G_UNLIKELY (fixed_size && size != fixed_size)
582 /* Creating a fixed-sized GVariant with a bytes of the wrong
585 * We should do the equivalent of pulling a fixed-sized child out
586 * of a broken container (ie: data is NULL size is equal to the correct
589 * This really ought not to happen if the data is trusted...
592 g_error ("Attempting to create a trusted GVariant instance out of invalid data");
594 /* We hang on to the GBytes (even though we don't use it anymore)
595 * because every GVariant must have a GBytes.
597 value->contents.serialised.data = NULL;
598 value->size = fixed_size;
605 * g_variant_get_type_info:
606 * @value: a #GVariant
608 * Returns the #GVariantTypeInfo corresponding to the type of @value. A
609 * reference is not added, so the return value is only good for the
610 * duration of the life of @value.
612 * Returns: the #GVariantTypeInfo for @value
615 g_variant_get_type_info (GVariant *value)
617 return value->type_info;
621 * g_variant_is_trusted:
622 * @value: a #GVariant
624 * Determines if @value is trusted by #GVariant to contain only
625 * fully-valid data. All values constructed solely via #GVariant APIs
626 * are trusted, but values containing data read in from other sources
627 * are usually not trusted.
629 * The main advantage of trusted data is that certain checks can be
630 * skipped. For example, we don't need to check that a string is
631 * properly nul-terminated or that an object path is actually a
632 * properly-formatted object path.
634 * Returns: if @value is trusted
637 g_variant_is_trusted (GVariant *value)
639 return (value->state & STATE_TRUSTED) != 0;
643 * g_variant_get_serialised:
644 * @value: a #GVariant
645 * @bytes: (out) (transfer none): a location to store the #GBytes
646 * @size: (out): a location to store the size of the returned data
648 * Ensures that @value is in serialised form and returns information
649 * about it. This is called from various APIs in gvariant.c
651 * Returns: data, of length @size
654 g_variant_get_serialised (GVariant *value,
658 g_variant_ensure_serialised (value);
661 *bytes = value->contents.serialised.bytes;
665 return value->contents.serialised.data;
672 * @value: a #GVariant
674 * Decreases the reference count of @value. When its reference count
675 * drops to 0, the memory used by the variant is freed.
680 g_variant_unref (GVariant *value)
682 g_return_if_fail (value != NULL);
683 g_return_if_fail (value->ref_count > 0);
685 if (g_atomic_int_dec_and_test (&value->ref_count))
687 if G_UNLIKELY (value->state & STATE_LOCKED)
688 g_critical ("attempting to free a locked GVariant instance. "
689 "This should never happen.");
691 value->state |= STATE_LOCKED;
693 g_variant_type_info_unref (value->type_info);
695 if (value->state & STATE_SERIALISED)
696 g_bytes_unref (value->contents.serialised.bytes);
698 g_variant_release_children (value);
700 memset (value, 0, sizeof (GVariant));
701 g_slice_free (GVariant, value);
707 * @value: a #GVariant
709 * Increases the reference count of @value.
711 * Returns: the same @value
716 g_variant_ref (GVariant *value)
718 g_return_val_if_fail (value != NULL, NULL);
719 g_return_val_if_fail (value->ref_count > 0, NULL);
721 g_atomic_int_inc (&value->ref_count);
727 * g_variant_ref_sink:
728 * @value: a #GVariant
730 * #GVariant uses a floating reference count system. All functions with
731 * names starting with `g_variant_new_` return floating
734 * Calling g_variant_ref_sink() on a #GVariant with a floating reference
735 * will convert the floating reference into a full reference. Calling
736 * g_variant_ref_sink() on a non-floating #GVariant results in an
737 * additional normal reference being added.
739 * In other words, if the @value is floating, then this call "assumes
740 * ownership" of the floating reference, converting it to a normal
741 * reference. If the @value is not floating, then this call adds a
742 * new normal reference increasing the reference count by one.
744 * All calls that result in a #GVariant instance being inserted into a
745 * container will call g_variant_ref_sink() on the instance. This means
746 * that if the value was just created (and has only its floating
747 * reference) then the container will assume sole ownership of the value
748 * at that point and the caller will not need to unreference it. This
749 * makes certain common styles of programming much easier while still
750 * maintaining normal refcounting semantics in situations where values
753 * Returns: the same @value
758 g_variant_ref_sink (GVariant *value)
760 g_return_val_if_fail (value != NULL, NULL);
761 g_return_val_if_fail (value->ref_count > 0, NULL);
763 g_variant_lock (value);
765 if (~value->state & STATE_FLOATING)
766 g_variant_ref (value);
768 value->state &= ~STATE_FLOATING;
770 g_variant_unlock (value);
776 * g_variant_take_ref:
777 * @value: a #GVariant
779 * If @value is floating, sink it. Otherwise, do nothing.
781 * Typically you want to use g_variant_ref_sink() in order to
782 * automatically do the correct thing with respect to floating or
783 * non-floating references, but there is one specific scenario where
784 * this function is helpful.
786 * The situation where this function is helpful is when creating an API
787 * that allows the user to provide a callback function that returns a
788 * #GVariant. We certainly want to allow the user the flexibility to
789 * return a non-floating reference from this callback (for the case
790 * where the value that is being returned already exists).
792 * At the same time, the style of the #GVariant API makes it likely that
793 * for newly-created #GVariant instances, the user can be saved some
794 * typing if they are allowed to return a #GVariant with a floating
797 * Using this function on the return value of the user's callback allows
798 * the user to do whichever is more convenient for them. The caller
799 * will alway receives exactly one full reference to the value: either
800 * the one that was returned in the first place, or a floating reference
801 * that has been converted to a full reference.
803 * This function has an odd interaction when combined with
804 * g_variant_ref_sink() running at the same time in another thread on
805 * the same #GVariant instance. If g_variant_ref_sink() runs first then
806 * the result will be that the floating reference is converted to a hard
807 * reference. If g_variant_take_ref() runs first then the result will
808 * be that the floating reference is converted to a hard reference and
809 * an additional reference on top of that one is added. It is best to
810 * avoid this situation.
812 * Returns: the same @value
815 g_variant_take_ref (GVariant *value)
817 g_return_val_if_fail (value != NULL, NULL);
818 g_return_val_if_fail (value->ref_count > 0, NULL);
820 g_atomic_int_and (&value->state, ~STATE_FLOATING);
826 * g_variant_is_floating:
827 * @value: a #GVariant
829 * Checks whether @value has a floating reference count.
831 * This function should only ever be used to assert that a given variant
832 * is or is not floating, or for debug purposes. To acquire a reference
833 * to a variant that might be floating, always use g_variant_ref_sink()
834 * or g_variant_take_ref().
836 * See g_variant_ref_sink() for more information about floating reference
839 * Returns: whether @value is floating
844 g_variant_is_floating (GVariant *value)
846 g_return_val_if_fail (value != NULL, FALSE);
848 return (value->state & STATE_FLOATING) != 0;
852 * g_variant_get_size:
853 * @value: a #GVariant instance
855 * Determines the number of bytes that would be required to store @value
856 * with g_variant_store().
858 * If @value has a fixed-sized type then this function always returned
861 * In the case that @value is already in serialised form or the size has
862 * already been calculated (ie: this function has been called before)
863 * then this function is O(1). Otherwise, the size is calculated, an
864 * operation which is approximately O(n) in the number of values
867 * Returns: the serialised size of @value
872 g_variant_get_size (GVariant *value)
878 * g_variant_get_data:
879 * @value: a #GVariant instance
881 * Returns a pointer to the serialised form of a #GVariant instance.
882 * The returned data may not be in fully-normalised form if read from an
883 * untrusted source. The returned data must not be freed; it remains
884 * valid for as long as @value exists.
886 * If @value is a fixed-sized value that was deserialised from a
887 * corrupted serialised container then %NULL may be returned. In this
888 * case, the proper thing to do is typically to use the appropriate
889 * number of nul bytes in place of @value. If @value is not fixed-sized
890 * then %NULL is never returned.
892 * In the case that @value is already in serialised form, this function
893 * is O(1). If the value is not already in serialised form,
894 * serialisation occurs implicitly and is approximately O(n) in the size
897 * To deserialise the data returned by this function, in addition to the
898 * serialised data, you must know the type of the #GVariant, and (if the
899 * machine might be different) the endianness of the machine that stored
900 * it. As a result, file formats or network messages that incorporate
901 * serialised #GVariants must include this information either
902 * implicitly (for instance "the file always contains a
903 * %G_VARIANT_TYPE_VARIANT and it is always in little-endian order") or
904 * explicitly (by storing the type and/or endianness in addition to the
907 * Returns: (transfer none): the serialised form of @value, or %NULL
912 g_variant_get_data (GVariant *value)
914 g_variant_ensure_serialised (value);
916 return value->contents.serialised.data;
921 * g_variant_n_children:
922 * @value: a container #GVariant
924 * Determines the number of children in a container #GVariant instance.
925 * This includes variants, maybes, arrays, tuples and dictionary
926 * entries. It is an error to call this function on any other type of
929 * For variants, the return value is always 1. For values with maybe
930 * types, it is always zero or one. For arrays, it is the length of the
931 * array. For tuples it is the number of tuple items (which depends
932 * only on the type). For dictionary entries, it is always 2
934 * This function is O(1).
936 * Returns: the number of children in the container
941 g_variant_n_children (GVariant *value)
945 if (g_variant_lock_in_tree_form (value))
947 n_children = value->contents.tree.n_children;
948 g_variant_unlock (value);
952 GVariantSerialised serialised = {
954 (gpointer) value->contents.serialised.data,
958 n_children = g_variant_serialised_n_children (serialised);
965 * g_variant_get_child_value:
966 * @value: a container #GVariant
967 * @index_: the index of the child to fetch
969 * Reads a child item out of a container #GVariant instance. This
970 * includes variants, maybes, arrays, tuples and dictionary
971 * entries. It is an error to call this function on any other type of
974 * It is an error if @index_ is greater than the number of child items
975 * in the container. See g_variant_n_children().
977 * The returned value is never floating. You should free it with
978 * g_variant_unref() when you're done with it.
980 * This function is O(1).
982 * Returns: (transfer full): the child at the specified index
987 g_variant_get_child_value (GVariant *value,
992 g_return_val_if_fail (index_ < g_variant_n_children (value), NULL);
994 if (g_variant_lock_in_tree_form (value))
997 child = g_variant_ref (value->contents.tree.children[index_]);
998 g_variant_unlock (value);
1002 GVariantSerialised serialised = {
1004 (gpointer) value->contents.serialised.data,
1007 GVariantSerialised s_child;
1009 /* get the serialiser to extract the serialised data for the child
1010 * from the serialised data for the container
1012 s_child = g_variant_serialised_get_child (serialised, index_);
1014 /* create a new serialised instance out of it */
1015 child = g_variant_new_serialised (s_child.type_info,
1016 g_bytes_ref (value->contents.serialised.bytes),
1017 s_child.data, s_child.size,
1018 value->state & STATE_TRUSTED);
1026 * @value: the #GVariant to store
1027 * @data: the location to store the serialised data at
1029 * Stores the serialised form of @value at @data. @data should be
1030 * large enough. See g_variant_get_size().
1032 * The stored data is in machine native byte order but may not be in
1033 * fully-normalised form if read from an untrusted source. See
1034 * g_variant_get_normal_form() for a solution.
1036 * As with g_variant_get_data(), to be able to deserialise the
1037 * serialised variant successfully, its type and (if the destination
1038 * machine might be different) its endianness must also be available.
1040 * This function is approximately O(n) in the size of @data.
1045 g_variant_store (GVariant *value,
1048 if (g_variant_lock_in_tree_form (value))
1050 g_variant_serialise (value, data);
1051 g_variant_unlock (value);
1055 if (value->contents.serialised.data != NULL)
1056 memcpy (data, value->contents.serialised.data, value->size);
1058 memset (data, 0, value->size);
1063 * g_variant_is_normal_form:
1064 * @value: a #GVariant instance
1066 * Checks if @value is in normal form.
1068 * The main reason to do this is to detect if a given chunk of
1069 * serialised data is in normal form: load the data into a #GVariant
1070 * using g_variant_new_from_data() and then use this function to
1073 * If @value is found to be in normal form then it will be marked as
1074 * being trusted. If the value was already marked as being trusted then
1075 * this function will immediately return %TRUE.
1077 * Returns: %TRUE if @value is in normal form
1082 g_variant_is_normal_form (GVariant *value)
1084 if (g_atomic_int_get (&value->state) & STATE_TRUSTED)
1087 /* We always take the lock here because we expect to find that the
1088 * value is in normal form and in that case, we need to update the
1089 * state, which requires holding the lock.
1091 g_variant_lock (value);
1093 if (value->state & STATE_SERIALISED)
1095 GVariantSerialised serialised = {
1097 (gpointer) value->contents.serialised.data,
1101 if (g_variant_serialised_is_normal (serialised))
1102 value->state |= STATE_TRUSTED;
1106 gboolean normal = TRUE;
1109 for (i = 0; i < value->contents.tree.n_children; i++)
1110 normal &= g_variant_is_normal_form (value->contents.tree.children[i]);
1113 value->state |= STATE_TRUSTED;
1116 g_variant_unlock (value);
1118 return (value->state & STATE_TRUSTED) != 0;