/*

 * 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 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, write to the

 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,

 * Boston, MA 02111-1307, USA.

 */

#include <glib/gvariant-core.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;

};

/* 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

 */

#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;

  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);

  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;

  return value;

}

/* -- internal -- */

/* < internal >

 * 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: a new #GVariant with a floating reference

 */

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 >

 * 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 <literal>g_variant_new_</literal> 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_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