gstreamer/gst/gstobject.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *                    2005 Wim Taymans <wim@fluendo.com>
 *
 * gstobject.c: Fundamental class used for all of GStreamer
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library 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 "gst_private.h"

#include "gstobject.h"
#include "gstmarshal.h"
#include "gstinfo.h"
#include "gstutils.h"

#ifndef GST_DISABLE_TRACE
#include "gsttrace.h"
#endif

#define DEBUG_REFCOUNT
#define REFCOUNT_HACK

/* Refcount hack: since glib is not threadsafe, the glib refcounter can be
 * screwed up and the object can be freed unexpectedly. We use an evil hack
 * to work around this problem. We set the glib refcount to a high value so
 * that glib will never unref the object under realistic circumstances. Then
 * we use our own atomic refcounting to do proper MT safe refcounting.
 *
 * A proper fix is of course to make the glib refcounting threadsafe which is
 * planned. Update: atomic refcounting is now in glib >= 2.7.3
 */
#ifdef REFCOUNT_HACK
#define PATCH_REFCOUNT(obj)    ((GObject*)(obj))->ref_count = 100000;
#define PATCH_REFCOUNT1(obj)    ((GObject*)(obj))->ref_count = 1;
#else
#define PATCH_REFCOUNT(obj)
#define PATCH_REFCOUNT1(obj)
#endif

/* Object signals and args */
enum
{
  PARENT_SET,
  PARENT_UNSET,
#ifndef GST_DISABLE_LOADSAVE_REGISTRY
  OBJECT_SAVED,
#endif
  DEEP_NOTIFY,
  LAST_SIGNAL
};

enum
{
  ARG_0,
  ARG_NAME
      /* FILL ME */
};

enum
{
  SO_OBJECT_LOADED,
  SO_LAST_SIGNAL
};

GType _gst_object_type = 0;
static GHashTable *object_name_counts = NULL;

G_LOCK_DEFINE_STATIC (object_name_mutex);

typedef struct _GstSignalObject GstSignalObject;
typedef struct _GstSignalObjectClass GstSignalObjectClass;

static GType gst_signal_object_get_type (void);
static void gst_signal_object_class_init (GstSignalObjectClass * klass);
static void gst_signal_object_init (GstSignalObject * object);

#ifndef GST_DISABLE_LOADSAVE_REGISTRY
static guint gst_signal_object_signals[SO_LAST_SIGNAL] = { 0 };
#endif

static void gst_object_class_init (GstObjectClass * klass);
static void gst_object_init (GTypeInstance * instance, gpointer g_class);

#ifndef GST_DISABLE_TRACE
static GObject *gst_object_constructor (GType type,
    guint n_construct_properties, GObjectConstructParam * construct_params);
#endif

static void gst_object_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_object_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);
static void gst_object_dispatch_properties_changed (GObject * object,
    guint n_pspecs, GParamSpec ** pspecs);

static void gst_object_dispose (GObject * object);
static void gst_object_finalize (GObject * object);

static gboolean gst_object_set_name_default (GstObject * object,
    const gchar * type_name);

#ifndef GST_DISABLE_LOADSAVE_REGISTRY
static void gst_object_real_restore_thyself (GstObject * object,
    xmlNodePtr self);
#endif

static GObjectClass *parent_class = NULL;
static guint gst_object_signals[LAST_SIGNAL] = { 0 };

GType
gst_object_get_type (void)
{
  if (!_gst_object_type) {
    static const GTypeInfo object_info = {
      sizeof (GstObjectClass),
      NULL,
      NULL,
      (GClassInitFunc) gst_object_class_init,
      NULL,
      NULL,
      sizeof (GstObject),
      0,
      gst_object_init,
      NULL
    };

    _gst_object_type =
        g_type_register_static (G_TYPE_OBJECT, "GstObject", &object_info,
        G_TYPE_FLAG_ABSTRACT);
  }
  return _gst_object_type;
}

static void
gst_object_class_init (GstObjectClass * klass)
{
  GObjectClass *gobject_class;

  gobject_class = (GObjectClass *) klass;

  parent_class = g_type_class_ref (G_TYPE_OBJECT);

  gobject_class->set_property = GST_DEBUG_FUNCPTR (gst_object_set_property);
  gobject_class->get_property = GST_DEBUG_FUNCPTR (gst_object_get_property);

  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_NAME,
      g_param_spec_string ("name", "Name", "The name of the object",
          NULL, G_PARAM_READWRITE | G_PARAM_CONSTRUCT));

  gst_object_signals[PARENT_SET] =
      g_signal_new ("parent-set", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
      G_STRUCT_OFFSET (GstObjectClass, parent_set), NULL, NULL,
      g_cclosure_marshal_VOID__OBJECT, G_TYPE_NONE, 1, G_TYPE_OBJECT);
  gst_object_signals[PARENT_UNSET] =
      g_signal_new ("parent-unset", G_TYPE_FROM_CLASS (klass),
      G_SIGNAL_RUN_LAST, G_STRUCT_OFFSET (GstObjectClass, parent_unset), NULL,
      NULL, g_cclosure_marshal_VOID__OBJECT, G_TYPE_NONE, 1, G_TYPE_OBJECT);
#ifndef GST_DISABLE_LOADSAVE_REGISTRY
  /* FIXME This should be the GType of xmlNodePtr instead of G_TYPE_POINTER */
  gst_object_signals[OBJECT_SAVED] =
      g_signal_new ("object-saved", G_TYPE_FROM_CLASS (klass),
      G_SIGNAL_RUN_LAST, G_STRUCT_OFFSET (GstObjectClass, object_saved), NULL,
      NULL, g_cclosure_marshal_VOID__POINTER, G_TYPE_NONE, 1, G_TYPE_POINTER);

  klass->restore_thyself = gst_object_real_restore_thyself;
#endif
  gst_object_signals[DEEP_NOTIFY] =
      g_signal_new ("deep-notify", G_TYPE_FROM_CLASS (klass),
      G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE | G_SIGNAL_DETAILED |
      G_SIGNAL_NO_HOOKS, G_STRUCT_OFFSET (GstObjectClass, deep_notify), NULL,
      NULL, gst_marshal_VOID__OBJECT_PARAM, G_TYPE_NONE, 2, G_TYPE_OBJECT,
      G_TYPE_PARAM);

  klass->path_string_separator = "/";
  klass->lock = g_new0 (GStaticRecMutex, 1);
  g_static_rec_mutex_init (klass->lock);

  klass->signal_object = g_object_new (gst_signal_object_get_type (), NULL);

  /* see the comments at gst_object_dispatch_properties_changed */
  gobject_class->dispatch_properties_changed
      = GST_DEBUG_FUNCPTR (gst_object_dispatch_properties_changed);

  gobject_class->dispose = gst_object_dispose;
  gobject_class->finalize = gst_object_finalize;
#ifndef GST_DISABLE_TRACE
  gobject_class->constructor = gst_object_constructor;
#endif
}

static void
gst_object_init (GTypeInstance * instance, gpointer g_class)
{
  GstObject *object = GST_OBJECT (instance);

  object->lock = g_mutex_new ();
  object->parent = NULL;
  object->name = NULL;
  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "%p new", object);
  gst_atomic_int_set (&object->refcount, 1);
  PATCH_REFCOUNT (object);

  object->flags = 0;
  GST_FLAG_SET (object, GST_OBJECT_FLOATING);
}

#ifndef GST_DISABLE_TRACE
static GObject *
gst_object_constructor (GType type, guint n_construct_properties,
    GObjectConstructParam * construct_params)
{
  const gchar *name;
  GstAllocTrace *trace;
  GObject *obj =
      G_OBJECT_CLASS (parent_class)->constructor (type, n_construct_properties,
      construct_params);

  name = g_type_name (type);

  trace = gst_alloc_trace_get (name);
  if (!trace) {
    trace = gst_alloc_trace_register (name);
  }
  gst_alloc_trace_new (trace, obj);

  return obj;
}
#endif
/**
 * gst_object_ref:
 * @object: GstObject to reference
 *
 * Increments the refence count on the object. This function
 * does not take the lock on the object because it relies on
 * atomic refcounting.
 *
 * This object returns the input parameter to ease writing
 * constructs like :
 *  result = gst_object_ref (object->parent);
 *
 * Returns: A pointer to the object
 */
gpointer
gst_object_ref (gpointer object)
{
  g_return_val_if_fail (GST_IS_OBJECT (object), NULL);

#ifdef DEBUG_REFCOUNT
#ifdef REFCOUNT_HACK
  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "%p ref %d->%d",
      object,
      GST_OBJECT_REFCOUNT_VALUE (object),
      GST_OBJECT_REFCOUNT_VALUE (object) + 1);
#else
  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "%p ref %d->%d",
      object,
      ((GObject *) object)->ref_count, ((GObject *) object)->ref_count + 1);
#endif
#endif

#ifdef REFCOUNT_HACK
  g_atomic_int_inc (&((GstObject *) object)->refcount);
  PATCH_REFCOUNT (object);
#else
  /* FIXME, not MT safe because glib is not MT safe */
  g_object_ref (object);
#endif

  return object;
}

/**
 * gst_object_unref:
 * @object: GstObject to unreference
 *
 * Decrements the refence count on the object.  If reference count hits
 * zero, destroy the object. This function does not take the lock
 * on the object as it relies on atomic refcounting.
 *
 * The unref method should never be called with the LOCK held since
 * this might deadlock the dispose function.
 */
void
gst_object_unref (gpointer object)
{
  g_return_if_fail (GST_IS_OBJECT (object));

#ifdef REFCOUNT_HACK
  g_return_if_fail (GST_OBJECT_REFCOUNT_VALUE (object) > 0);
#else
  g_return_if_fail (((GObject *) object)->ref_count > 0);
#endif

#ifdef DEBUG_REFCOUNT
#ifdef REFCOUNT_HACK
  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "%p unref %d->%d",
      object,
      GST_OBJECT_REFCOUNT_VALUE (object),
      GST_OBJECT_REFCOUNT_VALUE (object) - 1);
#else
  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "%p unref %d->%d",
      object,
      ((GObject *) object)->ref_count, ((GObject *) object)->ref_count - 1);
#endif
#endif

#ifdef REFCOUNT_HACK
  if (G_UNLIKELY (g_atomic_int_dec_and_test (&((GstObject *) object)->
              refcount))) {
    PATCH_REFCOUNT1 (object);
    g_object_unref (object);
  } else {
    PATCH_REFCOUNT (object);
  }
#else
  /* FIXME, not MT safe because glib is not MT safe */
  g_object_unref (object);
#endif
}

/**
 * gst_object_sink:
 * @object: GstObject to sink
 *
 * Removes floating reference on an object.  Any newly created object has
 * a refcount of 1 and is FLOATING.  This function should be used when
 * creating a new object to symbolically 'take ownership' of the object.
 * Use #gst_object_set_parent to have this done for you.
 *
 * MT safe. This function grabs and releases the object lock.
 */
void
gst_object_sink (gpointer object)
{
  g_return_if_fail (GST_IS_OBJECT (object));

  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "sink");

  GST_LOCK (object);
  if (G_LIKELY (GST_OBJECT_IS_FLOATING (object))) {
    GST_FLAG_UNSET (object, GST_OBJECT_FLOATING);
    GST_UNLOCK (object);
    gst_object_unref (object);
  } else {
    GST_UNLOCK (object);
  }
}

/**
 * gst_object_replace:
 * @oldobj: pointer to place of old GstObject
 * @newobj: new GstObject
 *
 * Unrefs the object pointer to by oldobj, refs the newobj and
 * puts the newobj in *oldobj. Be carefull when calling this
 * function, it does not take any locks. You might want to lock
 * the object owning the oldobj pointer before calling this
 * function.
 *
 * Make sure not to LOCK the oldobj because it might be unreffed
 * which could cause a deadlock when it is disposed.
 */
void
gst_object_replace (GstObject ** oldobj, GstObject * newobj)
{
  g_return_if_fail (oldobj != NULL);
  g_return_if_fail (*oldobj == NULL || GST_IS_OBJECT (*oldobj));
  g_return_if_fail (newobj == NULL || GST_IS_OBJECT (newobj));

#ifdef DEBUG_REFCOUNT
#ifdef REFCOUNT_HACK
  GST_CAT_LOG (GST_CAT_REFCOUNTING, "replace %s (%d) with %s (%d)",
      *oldobj ? GST_STR_NULL (GST_OBJECT_NAME (*oldobj)) : "(NONE)",
      *oldobj ? GST_OBJECT_REFCOUNT_VALUE (*oldobj) : 0,
      newobj ? GST_STR_NULL (GST_OBJECT_NAME (newobj)) : "(NONE)",
      newobj ? GST_OBJECT_REFCOUNT_VALUE (newobj) : 0);
#else
  GST_CAT_LOG (GST_CAT_REFCOUNTING, "replace %s (%d) with %s (%d)",
      *oldobj ? GST_STR_NULL (GST_OBJECT_NAME (*oldobj)) : "(NONE)",
      *oldobj ? G_OBJECT (*oldobj)->ref_count : 0,
      newobj ? GST_STR_NULL (GST_OBJECT_NAME (newobj)) : "(NONE)",
      newobj ? G_OBJECT (newobj)->ref_count : 0);
#endif
#endif

  if (G_LIKELY (*oldobj != newobj)) {
    if (newobj)
      gst_object_ref (newobj);
    if (*oldobj)
      gst_object_unref (*oldobj);

    *oldobj = newobj;
  }
}

/* dispose is called when the object has to release all links
 * to other objects */
static void
gst_object_dispose (GObject * object)
{
  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "dispose");

  GST_LOCK (object);
  GST_FLAG_SET (GST_OBJECT (object), GST_OBJECT_DESTROYED);
  GST_OBJECT_PARENT (object) = NULL;
  GST_UNLOCK (object);

  /* need to patch refcount so it is finalized */
  PATCH_REFCOUNT1 (object);

  parent_class->dispose (object);
}

/* finalize is called when the object has to free its resources */
static void
gst_object_finalize (GObject * object)
{
  GstObject *gstobject = GST_OBJECT (object);

  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "finalize");

  g_signal_handlers_destroy (object);

  g_free (gstobject->name);
  g_mutex_free (gstobject->lock);

#ifndef GST_DISABLE_TRACE
  {
    const gchar *name;
    GstAllocTrace *trace;

    name = g_type_name (G_OBJECT_TYPE (object));
    trace = gst_alloc_trace_get (name);
    g_assert (trace);
    gst_alloc_trace_free (trace, object);
  }
#endif

  parent_class->finalize (object);
}

/* Changing a GObject property of a GstObject will result in "deep_notify"
 * signals being emitted by the object itself, as well as in each parent
 * object. This is so that an application can connect a listener to the
 * top-level bin to catch property-change notifications for all contained
 * elements. 
 *
 * This function is not MT safe in glib so we need to lock it with a 
 * classwide mutex.
 *
 * MT safe.
 */
static void
gst_object_dispatch_properties_changed (GObject * object,
    guint n_pspecs, GParamSpec ** pspecs)
{
  GstObject *gst_object, *parent, *old_parent;
  guint i;
  gchar *name, *debug_name;
  GstObjectClass *klass;

  /* we fail when this is not a GstObject */
  g_return_if_fail (GST_IS_OBJECT (object));

  klass = GST_OBJECT_GET_CLASS (object);

  GST_CLASS_LOCK (klass);
  /* do the standard dispatching */
  PATCH_REFCOUNT (object);
  G_OBJECT_CLASS (parent_class)->dispatch_properties_changed (object, n_pspecs,
      pspecs);
  PATCH_REFCOUNT (object);

  gst_object = GST_OBJECT_CAST (object);
  name = gst_object_get_name (gst_object);
  debug_name = GST_STR_NULL (name);

  /* now let the parent dispatch those, too */
  parent = gst_object_get_parent (gst_object);
  while (parent) {
    /* for debugging ... */
    gchar *parent_name = gst_object_get_name (parent);

#ifndef GST_DISABLE_GST_DEBUG
    gchar *debug_parent_name = GST_STR_NULL (parent_name);
#endif

    /* need own category? */
    for (i = 0; i < n_pspecs; i++) {
      GST_CAT_LOG (GST_CAT_EVENT, "deep notification from %s to %s (%s)",
          debug_name, debug_parent_name, pspecs[i]->name);

      /* not MT safe because of glib, fixed by taking class lock higher up */
      PATCH_REFCOUNT (parent);
      PATCH_REFCOUNT (object);
      g_signal_emit (parent, gst_object_signals[DEEP_NOTIFY],
          g_quark_from_string (pspecs[i]->name), GST_OBJECT_CAST (object),
          pspecs[i]);
      PATCH_REFCOUNT (parent);
      PATCH_REFCOUNT (object);
    }
    g_free (parent_name);

    old_parent = parent;
    parent = gst_object_get_parent (old_parent);
    gst_object_unref (old_parent);
  }
  g_free (name);
  GST_CLASS_UNLOCK (klass);
}

/** 
 * gst_object_default_deep_notify:
 * @object: the #GObject that signalled the notify.
 * @orig: a #GstObject that initiated the notify.
 * @pspec: a #GParamSpec of the property.
 * @excluded_props: a set of user-specified properties to exclude or
 *  NULL to show all changes.
 *
 * A default deep_notify signal callback for an element. The user data 
 * should contain a pointer to an array of strings that should be excluded 
 * from the notify. The default handler will print the new value of the property 
 * using g_print.
 *
 * MT safe. This function grabs and releases the object's LOCK or getting the
 *          path string of the object.
 */
void
gst_object_default_deep_notify (GObject * object, GstObject * orig,
    GParamSpec * pspec, gchar ** excluded_props)
{
  GValue value = { 0, };        /* the important thing is that value.type = 0 */
  gchar *str = NULL;
  gchar *name = NULL;

  if (pspec->flags & G_PARAM_READABLE) {
    /* let's not print these out for excluded properties... */
    while (excluded_props != NULL && *excluded_props != NULL) {
      if (strcmp (pspec->name, *excluded_props) == 0)
        return;
      excluded_props++;
    }
    g_value_init (&value, G_PARAM_SPEC_VALUE_TYPE (pspec));
    g_object_get_property (G_OBJECT (orig), pspec->name, &value);

    if (G_IS_PARAM_SPEC_ENUM (pspec)) {
      GEnumValue *enum_value;

      enum_value =
          g_enum_get_value (G_ENUM_CLASS (g_type_class_ref (pspec->value_type)),
          g_value_get_enum (&value));

      str = g_strdup_printf ("%s (%d)", enum_value->value_nick,
          enum_value->value);
    } else {
      str = g_strdup_value_contents (&value);
    }
    name = gst_object_get_path_string (orig);
    g_print ("%s: %s = %s\n", name, pspec->name, str);
    g_free (name);
    g_free (str);
    g_value_unset (&value);
  } else {
    name = gst_object_get_path_string (orig);
    g_warning ("Parameter %s not readable in %s.", pspec->name, name);
    g_free (name);
  }
}

static gboolean
gst_object_set_name_default (GstObject * object, const gchar * type_name)
{
  gint count;
  gchar *name, *tmp;
  gboolean result;

  /* to ensure guaranteed uniqueness across threads, only one thread
   * may ever assign a name */
  G_LOCK (object_name_mutex);

  if (!object_name_counts) {
    object_name_counts = g_hash_table_new_full (g_str_hash, g_str_equal,
        g_free, NULL);
  }

  count = GPOINTER_TO_INT (g_hash_table_lookup (object_name_counts, type_name));
  g_hash_table_insert (object_name_counts, g_strdup (type_name),
      GINT_TO_POINTER (count + 1));

  G_UNLOCK (object_name_mutex);

  /* GstFooSink -> foosinkN */
  if (strncmp (type_name, "Gst", 3) == 0)
    type_name += 3;
  tmp = g_strdup_printf ("%s%d", type_name, count);
  name = g_ascii_strdown (tmp, strlen (tmp));
  g_free (tmp);

  result = gst_object_set_name (object, name);
  g_free (name);

  return result;
}

/**
 * gst_object_set_name:
 * @object: a #GstObject to set the name of
 * @name:   new name of object
 *
 * Sets the name of the object, or gives the object a guaranteed unique
 * name (if @name is NULL).
 * This function makes a copy of the provided name, so the caller
 * retains ownership of the name it sent.
 *
 * Returns: TRUE if the name could be set. Objects that have
 * a parent cannot be renamed.
 *
 * MT safe.  This function grabs and releases the object's LOCK.
 */
gboolean
gst_object_set_name (GstObject * object, const gchar * name)
{
  gboolean result;

  g_return_val_if_fail (GST_IS_OBJECT (object), FALSE);

  GST_LOCK (object);

  /* parented objects cannot be renamed */
  if (G_UNLIKELY (object->parent != NULL))
    goto had_parent;

  if (name != NULL) {
    g_free (object->name);
    object->name = g_strdup (name);
    GST_UNLOCK (object);
    result = TRUE;
  } else {
    GST_UNLOCK (object);
    result = gst_object_set_name_default (object, G_OBJECT_TYPE_NAME (object));
  }
  return result;

  /* error */
had_parent:
  {
    GST_UNLOCK (object);
    return FALSE;
  }
}

/**
 * gst_object_get_name:
 * @object: a #GstObject to get the name of
 *
 * Returns a copy of the name of the object.
 * Caller should g_free() the return value after usage.
 * For a nameless object, this returns NULL, which you can safely g_free()
 * as well.
 *
 * Returns: the name of the object. g_free() after usage.
 *
 * MT safe. This function grabs and releases the object's LOCK.
 */
gchar *
gst_object_get_name (GstObject * object)
{
  gchar *result = NULL;

  g_return_val_if_fail (GST_IS_OBJECT (object), NULL);

  GST_LOCK (object);
  result = g_strdup (object->name);
  GST_UNLOCK (object);

  return result;
}

/**
 * gst_object_set_name_prefix:
 * @object:      a #GstObject to set the name prefix of
 * @name_prefix: new name prefix of object
 *
 * Sets the name prefix of the object.
 * This function makes a copy of the provided name prefix, so the caller
 * retains ownership of the name prefix it sent.
 *
 * MT safe.  This function grabs and releases the object's LOCK.
 */
void
gst_object_set_name_prefix (GstObject * object, const gchar * name_prefix)
{
  g_return_if_fail (GST_IS_OBJECT (object));

  GST_LOCK (object);
  g_free (object->name_prefix);
  object->name_prefix = g_strdup (name_prefix); /* NULL gives NULL */
  GST_UNLOCK (object);
}

/**
 * gst_object_get_name_prefix:
 * @object: a #GstObject to get the name prefix of
 *
 * Returns a copy of the name prefix of the object.
 * Caller should g_free() the return value after usage.
 * For a prefixless object, this returns NULL, which you can safely g_free()
 * as well.
 *
 * Returns: the name prefix of the object. g_free() after usage.
 *
 * MT safe. This function grabs and releases the object's LOCK.
 */
gchar *
gst_object_get_name_prefix (GstObject * object)
{
  gchar *result = NULL;

  g_return_val_if_fail (GST_IS_OBJECT (object), NULL);

  GST_LOCK (object);
  result = g_strdup (object->name_prefix);
  GST_UNLOCK (object);

  return result;
}

/**
 * gst_object_set_parent:
 * @object: GstObject to set parent of
 * @parent: new parent of object
 *
 * Sets the parent of @object. The object's reference count will be incremented,
 * and any floating reference will be removed (see gst_object_sink()).
 *
 * Causes the parent-set signal to be emitted.
 *
 * Returns: TRUE if the parent could be set or FALSE when the object
 * already had a parent, the object and parent are the same or wrong
 * parameters were provided.
 *
 * MT safe. Grabs and releases the object's LOCK.
 */
gboolean
gst_object_set_parent (GstObject * object, GstObject * parent)
{
  g_return_val_if_fail (GST_IS_OBJECT (object), FALSE);
  g_return_val_if_fail (GST_IS_OBJECT (parent), FALSE);
  g_return_val_if_fail (object != parent, FALSE);

  GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "set parent (ref and sink)");

  GST_LOCK (object);
  if (G_UNLIKELY (object->parent != NULL))
    goto had_parent;

  /* sink object, we don't call our own function because we don't
   * need to release/acquire the lock needlessly or touch the refcount
   * in the floating case. */
  object->parent = parent;
  if (G_LIKELY (GST_OBJECT_IS_FLOATING (object))) {
    GST_FLAG_UNSET (object, GST_OBJECT_FLOATING);
    GST_UNLOCK (object);
  } else {
    GST_UNLOCK (object);
    gst_object_ref (object);
  }

  g_signal_emit (G_OBJECT (object), gst_object_signals[PARENT_SET], 0, parent);

  return TRUE;

  /* ERROR handling */
had_parent:
  {
    GST_UNLOCK (object);
    return FALSE;
  }
}

/**
 * gst_object_get_parent:
 * @object: GstObject to get parent of
 *
 * Returns the parent of @object. This function increases the refcount
 * of the parent object so you should gst_object_unref() it after usage.
 *
 * Returns: parent of the object, this can be NULL if the object has no
 *   parent. unref after usage.
 *
 * MT safe. Grabs and releases the object's LOCK.
 */
GstObject *
gst_object_get_parent (GstObject * object)
{
  GstObject *result = NULL;

  g_return_val_if_fail (GST_IS_OBJECT (object), NULL);

  GST_LOCK (object);
  result = object->parent;
  if (G_LIKELY (result))
    gst_object_ref (result);
  GST_UNLOCK (object);

  return result;
}

/**
 * gst_object_unparent:
 * @object: GstObject to unparent
 *
 * Clear the parent of @object, removing the associated reference.
 * This function decreases the refcount of the object so the object
 * might not point to valid memory anymore after calling this function.
 *
 * MT safe. Grabs and releases the object's lock.
 */
void
gst_object_unparent (GstObject * object)
{
  GstObject *parent;

  g_return_if_fail (GST_IS_OBJECT (object));

  GST_LOCK (object);
  parent = object->parent;

  if (G_LIKELY (parent != NULL)) {
    GST_CAT_LOG_OBJECT (GST_CAT_REFCOUNTING, object, "unparent");
    object->parent = NULL;
    GST_UNLOCK (object);

    g_signal_emit (G_OBJECT (object), gst_object_signals[PARENT_UNSET], 0,
        parent);

    gst_object_unref (object);
  } else {
    GST_UNLOCK (object);
  }
}

/**
 * gst_object_check_uniqueness:
 * @list: a list of #GstObject to check through
 * @name: the name to search for
 *
 * Checks to see if there is any object named @name in @list. This function
 * does not do any locking of any kind. You might want to protect the
 * provided list with the lock of the owner of the list. This function
 * will lock each GstObject in the list to compare the name, so be
 * carefull when passing a list with a locked object.
 *
 * Returns: TRUE if the name does not appear in the list, FALSE if it does.
 *
 * MT safe. Grabs and releases the LOCK of each object in the list.
 */
gboolean
gst_object_check_uniqueness (GList * list, const gchar * name)
{
  gboolean result = TRUE;

  g_return_val_if_fail (name != NULL, FALSE);

  for (; list; list = g_list_next (list)) {
    GstObject *child;
    gboolean eq;

    child = GST_OBJECT (list->data);

    GST_LOCK (child);
    eq = strcmp (GST_OBJECT_NAME (child), name) == 0;
    GST_UNLOCK (child);

    if (G_UNLIKELY (eq)) {
      result = FALSE;
      break;
    }
  }
  return result;
}


#ifndef GST_DISABLE_LOADSAVE_REGISTRY
/**
 * gst_object_save_thyself:
 * @object: GstObject to save
 * @parent: The parent XML node to save the object into
 *
 * Saves the given object into the parent XML node.
 *
 * Returns: the new xmlNodePtr with the saved object
 */
xmlNodePtr
gst_object_save_thyself (GstObject * object, xmlNodePtr parent)
{
  GstObjectClass *oclass;

  g_return_val_if_fail (GST_IS_OBJECT (object), parent);
  g_return_val_if_fail (parent != NULL, parent);

  oclass = GST_OBJECT_GET_CLASS (object);

  if (oclass->save_thyself)
    oclass->save_thyself (object, parent);

  g_signal_emit (G_OBJECT (object), gst_object_signals[OBJECT_SAVED], 0,
      parent);

  return parent;
}

/**
 * gst_object_restore_thyself:
 * @object: GstObject to load into
 * @self: The XML node to load the object from
 *
 * Restores the given object with the data from the parent XML node.
 */
void
gst_object_restore_thyself (GstObject * object, xmlNodePtr self)
{
  GstObjectClass *oclass;

  g_return_if_fail (GST_IS_OBJECT (object));
  g_return_if_fail (self != NULL);

  oclass = GST_OBJECT_GET_CLASS (object);

  if (oclass->restore_thyself)
    oclass->restore_thyself (object, self);
}

static void
gst_object_real_restore_thyself (GstObject * object, xmlNodePtr self)
{
  g_return_if_fail (GST_IS_OBJECT (object));
  g_return_if_fail (self != NULL);

  gst_class_signal_emit_by_name (object, "object_loaded", self);
}
#endif /* GST_DISABLE_LOADSAVE_REGISTRY */

static void
gst_object_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstObject *gstobject;

  gstobject = GST_OBJECT (object);

  switch (prop_id) {
    case ARG_NAME:
      gst_object_set_name (gstobject, g_value_get_string (value));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_object_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstObject *gstobject;

  gstobject = GST_OBJECT (object);

  switch (prop_id) {
    case ARG_NAME:
      g_value_take_string (value, gst_object_get_name (gstobject));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

/**
 * gst_object_get_path_string:
 * @object: GstObject to get the path from
 *
 * Generates a string describing the path of the object in
 * the object hierarchy. Only useful (or used) for debugging.
 *
 * Returns: a string describing the path of the object. You must
 *          g_free() the string after usage. 
 *
 * MT safe. Grabs and releases the object's LOCK for all objects
 *          in the hierarchy.
 */
gchar *
gst_object_get_path_string (GstObject * object)
{
  GSList *parentage;
  GSList *parents;
  void *parent;
  gchar *prevpath, *path;
  gchar *component;
  gchar *separator;

  /* ref object before adding to list */
  gst_object_ref (object);
  parentage = g_slist_prepend (NULL, object);

  path = g_strdup ("");

  /* first walk the object hierarchy to build a list of the parents,
   * be carefull here with refcounting. */
  do {
    if (GST_IS_OBJECT (object)) {
      parent = gst_object_get_parent (object);
      /* add parents to list, refcount remains increased while
       * we handle the object */
      if (parent)
        parentage = g_slist_prepend (parentage, parent);
    } else {
      break;
    }
    object = parent;
  } while (object != NULL);

  /* then walk the parent list and print them out. we need to
   * decrease the refcounting on each element after we handled
   * it. */
  for (parents = parentage; parents; parents = g_slist_next (parents)) {
    if (GST_IS_OBJECT (parents->data)) {
      GstObject *item = GST_OBJECT_CAST (parents->data);
      GstObjectClass *oclass = GST_OBJECT_GET_CLASS (item);

      component = gst_object_get_name (item);
      separator = oclass->path_string_separator;
      /* and unref now */
      gst_object_unref (item);
    } else {
      component = g_strdup_printf ("%p", parents->data);
      separator = "/";
    }

    prevpath = path;
    path = g_strjoin (separator, prevpath, component, NULL);
    g_free (prevpath);
    g_free (component);
  }

  g_slist_free (parentage);

  return path;
}

struct _GstSignalObject
{
  GObject object;
};

struct _GstSignalObjectClass
{
  GObjectClass parent_class;

  /* signals */
#ifndef GST_DISABLE_LOADSAVE_REGISTRY
  void (*object_loaded) (GstSignalObject * object, GstObject * new,
      xmlNodePtr self);
#endif                          /* GST_DISABLE_LOADSAVE_REGISTRY */
};

static GType
gst_signal_object_get_type (void)
{
  static GType signal_object_type = 0;

  if (!signal_object_type) {
    static const GTypeInfo signal_object_info = {
      sizeof (GstSignalObjectClass),
      NULL,
      NULL,
      (GClassInitFunc) gst_signal_object_class_init,
      NULL,
      NULL,
      sizeof (GstSignalObject),
      0,
      (GInstanceInitFunc) gst_signal_object_init,
      NULL
    };

    signal_object_type =
        g_type_register_static (G_TYPE_OBJECT, "GstSignalObject",
        &signal_object_info, 0);
  }
  return signal_object_type;
}

static void
gst_signal_object_class_init (GstSignalObjectClass * klass)
{
  GObjectClass *gobject_class;

  gobject_class = (GObjectClass *) klass;

  parent_class = g_type_class_ref (G_TYPE_OBJECT);

#ifndef GST_DISABLE_LOADSAVE_REGISTRY
  gst_signal_object_signals[SO_OBJECT_LOADED] =
      g_signal_new ("object-loaded", G_TYPE_FROM_CLASS (klass),
      G_SIGNAL_RUN_LAST, G_STRUCT_OFFSET (GstSignalObjectClass, object_loaded),
      NULL, NULL, gst_marshal_VOID__OBJECT_POINTER, G_TYPE_NONE, 2,
      G_TYPE_OBJECT, G_TYPE_POINTER);
#endif
}

static void
gst_signal_object_init (GstSignalObject * object)
{
}

/**
 * gst_class_signal_connect
 * @klass: the GstObjectClass to attach the signal to
 * @name: the name of the signal to attach to
 * @func: the signal function
 * @func_data: a pointer to user data
 *
 * Connect to a class signal.
 *
 * Returns: the signal id.
 */
guint
gst_class_signal_connect (GstObjectClass * klass,
    const gchar * name, gpointer func, gpointer func_data)
{
  return g_signal_connect (klass->signal_object, name, func, func_data);
}

#ifndef GST_DISABLE_LOADSAVE_REGISTRY
/**
 * gst_class_signal_emit_by_name:
 * @object: the object that sends the signal
 * @name: the name of the signal to emit
 * @self: data for the signal
 *
 * emits the named class signal.
 */
void
gst_class_signal_emit_by_name (GstObject * object,
    const gchar * name, xmlNodePtr self)
{
  GstObjectClass *oclass;

  oclass = GST_OBJECT_GET_CLASS (object);

  g_signal_emit_by_name (oclass->signal_object, name, object, self);
}

#endif /* GST_DISABLE_LOADSAVE_REGISTRY */