gstreamer/gst/gstelement.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gstelement.c: The base element, all elements derive from this
 *
 * 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.
 */

/* #define GST_DEBUG_ENABLED */
#include <glib.h>
#include <stdarg.h>
#include "gst_private.h"

#include "gstelement.h"
#include "gstextratypes.h"
#include "gstbin.h"
#include "gstscheduler.h"
#include "gstevent.h"
#include "gstutils.h"

/* Element signals and args */
enum {
  STATE_CHANGE,
  NEW_PAD,
  PAD_REMOVED,
  ERROR,
  EOS,
  DEEP_NOTIFY,
  LAST_SIGNAL
};

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

#define CLASS(element)	GST_ELEMENT_CLASS (G_OBJECT_GET_CLASS (element))

static void			gst_element_class_init		(GstElementClass *klass);
static void			gst_element_init		(GstElement *element);
static void			gst_element_base_class_init	(GstElementClass *klass);

static void			gst_element_set_property	(GObject *object, guint prop_id, 
								 const GValue *value, GParamSpec *pspec);
static void			gst_element_get_property	(GObject *object, guint prop_id, GValue *value, 
								 GParamSpec *pspec);
static void			gst_element_dispatch_properties_changed (GObject * object, guint n_pspecs, GParamSpec **pspecs);

static void 			gst_element_dispose 		(GObject *object);

static GstElementStateReturn	gst_element_change_state	(GstElement *element);
static void			gst_element_error_func		(GstElement* element, GstElement *source, gchar *errormsg);

#ifndef GST_DISABLE_LOADSAVE
static xmlNodePtr		gst_element_save_thyself	(GstObject *object, xmlNodePtr parent);
static void			gst_element_restore_thyself 	(GstObject *parent, xmlNodePtr self);
#endif

GType _gst_element_type = 0;

static GstObjectClass *parent_class = NULL;
static guint gst_element_signals[LAST_SIGNAL] = { 0 };

GType gst_element_get_type (void) 
{
  if (!_gst_element_type) {
    static const GTypeInfo element_info = {
      sizeof(GstElementClass),
      (GBaseInitFunc)gst_element_base_class_init,
      NULL,
      (GClassInitFunc)gst_element_class_init,
      NULL,
      NULL,
      sizeof(GstElement),
      0,
      (GInstanceInitFunc)gst_element_init,
      NULL
    };
    _gst_element_type = g_type_register_static(GST_TYPE_OBJECT, "GstElement", 
		          &element_info, G_TYPE_FLAG_ABSTRACT);
  }
  return _gst_element_type;
}

static void
gst_element_class_init (GstElementClass *klass)
{
  GObjectClass *gobject_class;
  GstObjectClass *gstobject_class;

  gobject_class = (GObjectClass*) klass;
  gstobject_class = (GstObjectClass*) klass;

  parent_class = g_type_class_ref(GST_TYPE_OBJECT);

  gst_element_signals[STATE_CHANGE] =
    g_signal_new ("state_change", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, state_change), NULL, NULL,
		  gst_marshal_VOID__INT_INT, G_TYPE_NONE, 2,
                  G_TYPE_INT, G_TYPE_INT);
  gst_element_signals[NEW_PAD] =
    g_signal_new ("new_pad", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, new_pad), NULL, NULL,
                  gst_marshal_VOID__OBJECT, G_TYPE_NONE, 1,
                  G_TYPE_OBJECT);
  gst_element_signals[PAD_REMOVED] =
    g_signal_new ("pad_removed", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, pad_removed), NULL, NULL,
                  gst_marshal_VOID__OBJECT, G_TYPE_NONE, 1,
                  G_TYPE_OBJECT);
  gst_element_signals[ERROR] =
    g_signal_new ("error", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, error), NULL, NULL,
                  gst_marshal_VOID__OBJECT_STRING, G_TYPE_NONE, 2,
                  G_TYPE_OBJECT, G_TYPE_STRING);
  gst_element_signals[EOS] =
    g_signal_new ("eos", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass,eos), NULL, NULL,
                  gst_marshal_VOID__VOID, G_TYPE_NONE, 0);
  gst_element_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 (GstElementClass, deep_notify), NULL, NULL,
		  gst_marshal_VOID__OBJECT_PARAM, G_TYPE_NONE,
		  2, G_TYPE_OBJECT, G_TYPE_PARAM);


  gobject_class->set_property 		= GST_DEBUG_FUNCPTR (gst_element_set_property);
  gobject_class->get_property 		= GST_DEBUG_FUNCPTR (gst_element_get_property);

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

  gobject_class->dispose 		= GST_DEBUG_FUNCPTR (gst_element_dispose);

#ifndef GST_DISABLE_LOADSAVE
  gstobject_class->save_thyself 	= GST_DEBUG_FUNCPTR (gst_element_save_thyself);
  gstobject_class->restore_thyself 	= GST_DEBUG_FUNCPTR (gst_element_restore_thyself);
#endif

  klass->change_state 			= GST_DEBUG_FUNCPTR (gst_element_change_state);
  klass->error	 			= GST_DEBUG_FUNCPTR (gst_element_error_func);
  klass->elementfactory 		= NULL;
  klass->padtemplates 			= NULL;
  klass->numpadtemplates 		= 0;
}

static void
gst_element_base_class_init (GstElementClass *klass)
{
  GObjectClass *gobject_class;

  gobject_class = (GObjectClass*) klass;

  gobject_class->set_property =		GST_DEBUG_FUNCPTR(gst_element_set_property);
  gobject_class->get_property =		GST_DEBUG_FUNCPTR(gst_element_get_property);
}

static void
gst_element_init (GstElement *element)
{
  element->current_state = GST_STATE_NULL;
  element->pending_state = GST_STATE_VOID_PENDING;
  element->numpads = 0;
  element->numsrcpads = 0;
  element->numsinkpads = 0;
  element->pads = NULL;
  element->loopfunc = NULL;
  element->sched = NULL;
  element->sched_private = NULL;
  element->state_mutex = g_mutex_new ();
  element->state_cond = g_cond_new ();
}

static void
gst_element_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
{
  GstElementClass *oclass = CLASS (object);

  if (oclass->set_property)
    (oclass->set_property) (object, prop_id, value, pspec);
}

static void
gst_element_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
{
  GstElementClass *oclass = CLASS (object);

  if (oclass->get_property)
    (oclass->get_property) (object, prop_id, value, pspec);
}

/* Changing a GObject property of an element will result in "deep_notify"
 * signals being emitted by the element itself, as well as in each parent
 * element. This is so that an application can connect a listener to the
 * top-level bin to catch property-change notifications for all contained
 * elements. */
static void
gst_element_dispatch_properties_changed (GObject     *object,
                                         guint        n_pspecs,
                                         GParamSpec **pspecs)
{
  GstObject *gst_object;
  guint i;

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

  /* now let the parent dispatch those, too */
  gst_object = GST_OBJECT (object);
  while (gst_object)
  {
    /* need own category? */
    for (i = 0; i < n_pspecs; i++) {
      GST_DEBUG (GST_CAT_EVENT, "deep notification from %s to %s (%s)", GST_OBJECT_NAME (object), 
		    GST_OBJECT_NAME (gst_object), pspecs[i]->name);
      g_signal_emit (gst_object, gst_element_signals[DEEP_NOTIFY], g_quark_from_string (pspecs[i]->name), 
		     (GstObject *) object, pspecs[i]);
    }

    gst_object = GST_OBJECT_PARENT (gst_object);
  }
}

static GstPad*
gst_element_request_pad (GstElement *element, GstPadTemplate *templ, const gchar* name)
{
  GstPad *newpad = NULL;
  GstElementClass *oclass;

  oclass = CLASS (element);
  if (oclass->request_new_pad)
    newpad = (oclass->request_new_pad)(element, templ, name);

  return newpad;
}

void
gst_element_release_request_pad (GstElement *element, GstPad *pad)
{
  GstElementClass *oclass;

  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (GST_IS_PAD (pad));

  oclass = CLASS (element);
  if (oclass->release_pad)
    (oclass->release_pad) (element, pad);
}


/**
 * gst_element_set_name:
 * @element: a #GstElement to set name of
 * @name: new name of element
 *
 * Sets the name of the element, getting rid of the old name if there was
 * one.
 */
void
gst_element_set_name (GstElement *element, const gchar *name)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));

  gst_object_set_name (GST_OBJECT (element), name);
}

/**
 * gst_element_get_name:
 * @element: a #GstElement to get name of
 *
 * Gets the name of the element.
 *
 * Returns: name of the element
 */
const gchar*
gst_element_get_name (GstElement *element)
{
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  return GST_OBJECT_NAME (element);
}

/**
 * gst_element_set_parent:
 * @element: a #GstElement to set parent of
 * @parent: new parent of the object
 *
 * Sets the parent of the element.
 */
void
gst_element_set_parent (GstElement *element, GstObject *parent)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (GST_OBJECT_PARENT (element) == NULL);
  g_return_if_fail (parent != NULL);
  g_return_if_fail (GST_IS_OBJECT (parent));
  g_return_if_fail ((gpointer)element != (gpointer)parent);

  gst_object_set_parent (GST_OBJECT (element), parent);
}

/**
 * gst_element_get_parent:
 * @element: a #GstElement to get the parent of
 *
 * Gets the parent of the element.
 *
 * Returns: the #GstElement parent of the element
 */
GstObject*
gst_element_get_parent (GstElement *element)
{
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  return GST_OBJECT_PARENT (element);
}

/**
 * gst_element_set_clock:
 * @element: a #GstElement to set the clock for
 * @clock: the #GstClock to set for the element
 *
 * Sets the clock for the element.
 */
void
gst_element_set_clock (GstElement *element, GstClock *clock)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));

  if (element->setclockfunc)
    element->setclockfunc (element, clock);
}

/**
 * gst_element_get_clock:
 * @element: a #GstElement to get the clock of
 *
 * Gets the clock of the element.
 *
 * Returns: the #GstClock of the element.
 */
GstClock*
gst_element_get_clock (GstElement *element)
{
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  
  if (element->getclockfunc)
    return element->getclockfunc (element);

  return NULL;
}

/**
 * gst_element_clock_wait:
 * @element: a #GstElement
 * @clock: the #GstClock to use
 * @time: the #GstClockTime to wait for on the clock
 *
 * Waits for a specific time on the clock.
 *
 * Returns: the #GstClockReturn result of the wait operation
 */
GstClockReturn
gst_element_clock_wait (GstElement *element, GstClock *clock, GstClockTime time)
{
  g_return_val_if_fail (element != NULL, GST_CLOCK_ERROR);
  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_CLOCK_ERROR);

  if (GST_ELEMENT_SCHED (element)) {
    return gst_scheduler_clock_wait (GST_ELEMENT_SCHED (element), element, clock, time);
  }
  else 
    return GST_CLOCK_TIMEOUT;
}

/**
 * gst_element_add_pad:
 * @element: element to add pad to
 * @pad: pad to add
 *
 * Add a pad (connection point) to the element, setting the parent of the
 * pad to the element (and thus adding a reference).
 */
void
gst_element_add_pad (GstElement *element, GstPad *pad)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_PAD (pad));

  /* first check to make sure the pad's parent is already set */
  g_return_if_fail (GST_PAD_PARENT (pad) == NULL);

  /* then check to see if there's already a pad by that name here */
  g_return_if_fail (gst_object_check_uniqueness (element->pads, GST_PAD_NAME(pad)) == TRUE);

  /* set the pad's parent */
  GST_DEBUG (GST_CAT_ELEMENT_PADS,"setting parent of pad '%s' to '%s'",
        GST_PAD_NAME (pad), GST_ELEMENT_NAME (element));
  gst_object_set_parent (GST_OBJECT (pad), GST_OBJECT (element));

  /* add it to the list */
  element->pads = g_list_append (element->pads, pad);
  element->numpads++;
  if (gst_pad_get_direction (pad) == GST_PAD_SRC)
    element->numsrcpads++;
  else
    element->numsinkpads++;

  /* emit the NEW_PAD signal */
  g_signal_emit (G_OBJECT (element), gst_element_signals[NEW_PAD], 0, pad);
}

/**
 * gst_element_remove_pad:
 * @element: element to remove pad from
 * @pad: pad to remove
 *
 * Remove a pad (connection point) from the element, 
 */
void
gst_element_remove_pad (GstElement *element, GstPad *pad)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_PAD (pad));

  g_return_if_fail (GST_PAD_PARENT (pad) == element);

  /* check to see if the pad is still connected */
  /* FIXME: what if someone calls _remove_pad instead of 
    _remove_ghost_pad? */
  if (GST_IS_REAL_PAD (pad)) {
    g_return_if_fail (GST_RPAD_PEER (pad) == NULL);
  }
  
  /* remove it from the list */
  element->pads = g_list_remove (element->pads, pad);
  element->numpads--;
  if (gst_pad_get_direction (pad) == GST_PAD_SRC)
    element->numsrcpads--;
  else
    element->numsinkpads--;

  g_signal_emit (G_OBJECT (element), gst_element_signals[PAD_REMOVED], 0, pad);

  gst_object_unparent (GST_OBJECT (pad));
}

/**
 * gst_element_add_ghost_pad:
 * @element: element to add ghost pad to
 * @pad: pad from which the new ghost pad will be created
 * @name: name of the new ghost pad
 *
 * Create a ghost pad from the given pad, and add it to the list of pads
 * for this element.
 * 
 * Returns: the added ghost pad or NULL, if no ghost pad was created.
 */
GstPad *
gst_element_add_ghost_pad (GstElement *element, GstPad *pad, gchar *name)
{
  GstPad *ghostpad;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  /* then check to see if there's already a pad by that name here */
  g_return_val_if_fail (gst_object_check_uniqueness (element->pads, name) == TRUE, NULL);

  GST_DEBUG(GST_CAT_ELEMENT_PADS,"creating new ghost pad called %s, from pad %s:%s",
            name,GST_DEBUG_PAD_NAME(pad));
  ghostpad = gst_ghost_pad_new (name, pad);

  /* add it to the list */
  GST_DEBUG(GST_CAT_ELEMENT_PADS,"adding ghost pad %s to element %s",
            name, GST_ELEMENT_NAME (element));
  element->pads = g_list_append (element->pads, ghostpad);
  element->numpads++;
  /* set the parent of the ghostpad */
  gst_object_set_parent (GST_OBJECT (ghostpad), GST_OBJECT (element));

  GST_DEBUG(GST_CAT_ELEMENT_PADS,"added ghostpad %s:%s",GST_DEBUG_PAD_NAME(ghostpad));

  /* emit the NEW_GHOST_PAD signal */
  g_signal_emit (G_OBJECT (element), gst_element_signals[NEW_PAD], 0, ghostpad);
	
  return ghostpad;
}

/**
 * gst_element_remove_ghost_pad:
 * @element: element to remove the ghost pad from
 * @pad: ghost pad to remove
 *
 * removes a ghost pad from an element
 */
void
gst_element_remove_ghost_pad (GstElement *element, GstPad *pad)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_GHOST_PAD (pad));

  /* FIXME this is redundant?
   * wingo 10-july-2001: I don't think so, you have to actually remove the pad
   * from the element. gst_pad_remove_ghost_pad just removes the ghostpad from
   * the real pad's ghost pad list
   */
  gst_pad_remove_ghost_pad (GST_PAD (GST_PAD_REALIZE (pad)), pad);
  gst_element_remove_pad (element, pad);
}


/**
 * gst_element_get_pad:
 * @element: element to find pad of
 * @name: name of pad to retrieve
 *
 * Retrieve a pad from the element by name.
 *
 * Returns: requested pad if found, otherwise NULL.
 */
GstPad*
gst_element_get_pad (GstElement *element, const gchar *name)
{
  GstPad *pad;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  if ((pad = gst_element_get_static_pad (element, name)))
    return pad;
  
  pad = gst_element_get_request_pad (element, name);
  
  return pad;
}

/**
 * gst_element_get_static_pad:
 * @element: element to find pad of
 * @name: name of pad to retrieve
 *
 * Retrieve a pad from the element by name. This version only retrieves
 * already-existing (i.e. 'static') pads.
 *
 * Returns: requested pad if found, otherwise NULL.
 */
GstPad *
gst_element_get_static_pad (GstElement *element, const gchar *name)
{
  GList *walk;
  
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  walk = element->pads;
  while (walk) {
    GstPad *pad;
    
    pad = GST_PAD(walk->data);
    if (strcmp (GST_PAD_NAME(pad), name) == 0) {
      GST_INFO (GST_CAT_ELEMENT_PADS, "found pad %s:%s", GST_DEBUG_PAD_NAME (pad));
      return pad;
    }
    walk = g_list_next (walk);
  }

  GST_INFO (GST_CAT_ELEMENT_PADS, "no such pad '%s' in element \"%s\"", name, GST_OBJECT_NAME (element));
  return NULL;
}

/**
 * gst_element_get_request_pad:
 * @element: element to find pad of
 * @name: name of pad to retrieve
 *
 * Retrieve a pad from the element by name. This version only retrieves
 * request pads.
 *
 * Returns: requested pad if found, otherwise NULL.
 */
GstPad*
gst_element_get_request_pad (GstElement *element, const gchar *name)
{
  GstPadTemplate *templ = NULL;
  GstPad *pad;
  const gchar *req_name = NULL;
  gboolean templ_found = FALSE;
  GList *list;
  gint n;
  const gchar *data;
  gchar *str, *endptr = NULL;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  if (strstr (name, "%")) {
    templ = gst_element_get_pad_template (element, name);
    req_name = NULL;
    if (templ)
      templ_found = TRUE;
  } else {
    list = gst_element_get_pad_template_list(element);
    while (!templ_found && list) {
      templ = (GstPadTemplate*) list->data;
      if (templ->presence == GST_PAD_REQUEST) {
        /* we know that %s and %d are the only possibilities because of sanity
           checks in gst_pad_template_new */
        GST_DEBUG (GST_CAT_PADS, "comparing %s to %s", name, templ->name_template);
        if ((str = strchr (templ->name_template, '%')) &&
            strncmp (templ->name_template, name, str - templ->name_template) == 0 &&
            strlen (name) > str - templ->name_template) {
          data = name + (str - templ->name_template);
          if (*(str+1) == 'd') {
            /* it's an int */
            n = (gint) strtol (data, &endptr, 10);
            if (endptr && *endptr == '\0') {
              templ_found = TRUE;
              req_name = name;
              break;
            }
          } else {
            /* it's a string */
            templ_found = TRUE;
            req_name = name;
            break;
          }
        }
      }
      list = list->next;
    }
  }
  
  if (!templ_found)
      return NULL;
  
  pad = gst_element_request_pad (element, templ, req_name);
  
  return pad;
}

/**
 * gst_element_get_pad_list:
 * @element: element to get pads of
 *
 * Retrieve a list of the pads associated with the element.
 *
 * Returns: GList of pads
 */
GList*
gst_element_get_pad_list (GstElement *element)
{
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  /* return the list of pads */
  return element->pads;
}

/**
 * gst_element_class_add_pad_template:
 * @klass: element class to add padtemplate to
 * @templ: padtemplate to add
 *
 * Add a padtemplate to an element class. This is useful if you have derived a custom
 * bin and wish to provide an on-request pad at runtime. Plugin writers should use
 * gst_element_factory_add_pad_template instead.
 */
void
gst_element_class_add_pad_template (GstElementClass *klass, GstPadTemplate *templ)
{
  g_return_if_fail (klass != NULL);
  g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
  g_return_if_fail (templ != NULL);
  g_return_if_fail (GST_IS_PAD_TEMPLATE (templ));
  
  klass->padtemplates = g_list_append (klass->padtemplates, templ);
  klass->numpadtemplates++;
}

/**
 * gst_element_get_pad_template_list:
 * @element: element to get padtemplates of
 *
 * Retrieve a list of the padtemplates associated with the element.
 *
 * Returns: GList of padtemplates
 */
GList*
gst_element_get_pad_template_list (GstElement *element)
{
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  return CLASS (element)->padtemplates;
}

/**
 * gst_element_get_pad_template:
 * @element: element to get padtemplate of
 * @name: the name of the padtemplate to get.
 *
 * Retrieve a padtemplate from this element with the
 * given name.
 *
 * Returns: the padtemplate with the given name. No unreferencing is necessary.
 */
GstPadTemplate*
gst_element_get_pad_template (GstElement *element, const guchar *name)
{
  GList *padlist;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  padlist = gst_element_get_pad_template_list (element);

  while (padlist) {
    GstPadTemplate *padtempl = (GstPadTemplate*) padlist->data;

    if (!strcmp (padtempl->name_template, name))
      return padtempl;

    padlist = g_list_next (padlist);
  }

  return NULL;
}

/**
 * gst_element_get_compatible_pad_template:
 * @element: element to get padtemplate of
 * @templ: a template to find a compatible template for
 *
 * Generate a padtemplate for this element compatible with the given
 * template, ie able to link to it.
 *
 * Returns: the padtemplate. No unreferencing is necessary.
 */
GstPadTemplate*
gst_element_get_compatible_pad_template (GstElement *element, GstPadTemplate *compattempl)
{
  GstPadTemplate *newtempl = NULL;
  GList *padlist;

  GST_DEBUG(GST_CAT_ELEMENT_PADS,"gst_element_get_pad_template_by_compatible()");

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (compattempl != NULL, NULL);

  padlist = gst_element_get_pad_template_list (element);

  while (padlist) {
    GstPadTemplate *padtempl = (GstPadTemplate*) padlist->data;
    gboolean compat = FALSE;

    /* Ignore name
     * Ignore presence
     * Check direction (must be opposite)
     * Check caps
     */
    GST_DEBUG(GST_CAT_CAPS,"checking direction and caps");
    if (padtempl->direction == GST_PAD_SRC &&
      compattempl->direction == GST_PAD_SINK) {
      GST_DEBUG(GST_CAT_CAPS,"compatible direction: found src pad template");
      compat = gst_caps_check_compatibility(GST_PAD_TEMPLATE_CAPS (padtempl),
					    GST_PAD_TEMPLATE_CAPS (compattempl));
      GST_DEBUG(GST_CAT_CAPS,"caps are %scompatible", (compat?"":"not "));
    } else if (padtempl->direction == GST_PAD_SINK &&
	       compattempl->direction == GST_PAD_SRC) {
      GST_DEBUG(GST_CAT_CAPS,"compatible direction: found sink pad template");
      compat = gst_caps_check_compatibility(GST_PAD_TEMPLATE_CAPS (compattempl),
					    GST_PAD_TEMPLATE_CAPS (padtempl));
      GST_DEBUG(GST_CAT_CAPS,"caps are %scompatible", (compat?"":"not "));
    }

    if (compat) {
      newtempl = padtempl;
      break;
    }

    padlist = g_list_next (padlist);
  }

  return newtempl;
}

/**
 * gst_element_request_compatible_pad:
 * @element: element to request a new pad from
 * @templ: a pad template to which the new pad should be able to connect
 *
 * Request a new pad from the element. The template will
 * be used to decide what type of pad to create. This function
 * is typically used for elements with a padtemplate with presence
 * GST_PAD_REQUEST.
 *
 * Returns: the new pad that was created.
 */
GstPad*
gst_element_request_compatible_pad (GstElement *element, GstPadTemplate *templ)
{
  GstPadTemplate *templ_new;
  GstPad *pad = NULL;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (templ != NULL, NULL);

  templ_new = gst_element_get_compatible_pad_template (element, templ);
  if (templ_new != NULL)
      pad = gst_element_request_pad (element, templ_new, NULL);

  return pad;
}


/**
 * gst_element_get_compatible_pad_filtered:
 * @element: the element in which the pad should be found
 * @pad: the pad to find a compatible one for
 * @filtercaps: the caps to use as a filter
 *
 * Looks for an unconnected pad to which the given pad can connect to.
 * It is not guaranteed that connecting the pads will work, though
 * it should work in most cases.
 *
 * Returns: the pad to which a connection can be made
 */
GstPad*			
gst_element_get_compatible_pad_filtered (GstElement *element, GstPad *pad, GstCaps *filtercaps)
{
  GList *pads;
  GstPadTemplate *templ;
  GstCaps *templcaps;
  GstPad *foundpad = NULL;
  
  /* checks */
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  
  /* let's use the real pad */
  pad = (GstPad *) GST_PAD_REALIZE (pad);
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_RPAD_PEER (pad) == NULL, NULL);
  
  /* try to get an existing unconnected pad */
  pads = gst_element_get_pad_list (element);
  while (pads) {
    GstPad *current = GST_PAD (pads->data);
    if ((GST_PAD_PEER (GST_PAD_REALIZE (current)) == NULL) &&
        gst_pad_can_connect_filtered (pad, current, filtercaps)) {
      return current;
    }
    pads = g_list_next (pads);
  }
  
  /* try to create a new one */
  /* requesting is a little crazy, we need a template. Let's create one */
  if (filtercaps != NULL) {
    templcaps = gst_caps_intersect (filtercaps, (GstCaps *) GST_RPAD_CAPS (pad));
    if (templcaps == NULL)
      return NULL;
  } else {
    templcaps = gst_caps_copy (gst_pad_get_caps (pad));
  }
  
  templ = gst_pad_template_new ((gchar *) GST_PAD_NAME (pad), GST_RPAD_DIRECTION (pad),
                               GST_PAD_ALWAYS, templcaps, NULL);
  foundpad = gst_element_request_compatible_pad (element, templ);
  gst_object_unref (GST_OBJECT (templ)); /* this will take care of the caps too */
  
  /* FIXME: this is broken, but it's in here so autoplugging elements that don't
     have caps on their source padtemplates (spider) can connect... */
  if (!foundpad && !filtercaps) {
    templ = gst_pad_template_new ((gchar *) GST_PAD_NAME (pad), GST_RPAD_DIRECTION (pad),
                                 GST_PAD_ALWAYS, NULL, NULL);
    foundpad = gst_element_request_compatible_pad (element, templ);
    gst_object_unref (GST_OBJECT (templ));
  }
  
  return foundpad;
}

/**
 * gst_element_get_compatible_pad:
 * @element: the element in which the pad should be found
 * @pad: the pad to find a compatible one for
 *
 * Looks for an unconnected pad to which the given pad can connect to.
 * It is not guaranteed that connecting the pads will work, though
 * it should work in most cases.
 *
 * Returns: the pad to which a connection can be made
 */
GstPad*			
gst_element_get_compatible_pad (GstElement *element, GstPad *pad)
{
  return gst_element_get_compatible_pad_filtered (element, pad, NULL);
}

/**
 * gst_element_connect_filtered:
 * @src: the element containing source pad
 * @dest: the element containing destination pad
 * @filtercaps: the caps to use as filter
 *
 * Connect the source to the destination element using the filtercaps.
 * The connection must be from source to destination, the other
 * direction will not be tried.
 * The functions looks for existing pads that aren't connected yet. 
 + It will use request pads if possible. But both pads will not be requested.
 * If multiple connections are possible, only one is established.
 *
 * Returns: TRUE if the elements could be connected.
 */
gboolean
gst_element_connect_filtered (GstElement *src, GstElement *dest, 
			               GstCaps *filtercaps)
{
  GList *srcpads, *destpads, *srctempls, *desttempls, *l;
  GstPad *srcpad, *destpad;
  GstPadTemplate *srctempl, *desttempl;

  /* checks */
  g_return_val_if_fail (src != NULL, FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT(src), FALSE);
  g_return_val_if_fail (dest != NULL, FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT(dest), FALSE);

  GST_DEBUG (GST_CAT_ELEMENT_PADS, "attempting to connect element %s to element %s", GST_ELEMENT_NAME (src), GST_ELEMENT_NAME (dest));
   
  /* loop through the existing pads in the source */
  srcpads = gst_element_get_pad_list (src);
  destpads = gst_element_get_pad_list (dest);

  if (srcpads || destpads) {
    while (srcpads) {
      srcpad = (GstPad *) GST_PAD_REALIZE (srcpads->data);
      if ((GST_RPAD_DIRECTION (srcpad) == GST_PAD_SRC) &&
          (GST_PAD_PEER (srcpad) == NULL)) {
        destpad = gst_element_get_compatible_pad_filtered (dest, srcpad, filtercaps);
        if (destpad && gst_pad_connect_filtered (srcpad, destpad, filtercaps)) {
          GST_DEBUG (GST_CAT_ELEMENT_PADS, "connected pad %s:%s to pad %s:%s", GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (destpad));
          return TRUE;
        }
      }
      srcpads = g_list_next (srcpads);
    }
    
    /* loop through the existing pads in the destination */
    while (destpads) {
      destpad = (GstPad *) GST_PAD_REALIZE (destpads->data);
      if ((GST_RPAD_DIRECTION (destpad) == GST_PAD_SINK) &&
          (GST_PAD_PEER (destpad) == NULL)) {
        srcpad = gst_element_get_compatible_pad_filtered (src, destpad, filtercaps);
        if (srcpad && gst_pad_connect_filtered (srcpad, destpad, filtercaps)) {
          GST_DEBUG (GST_CAT_ELEMENT_PADS, "connected pad %s:%s to pad %s:%s", GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (destpad));
          return TRUE;
        }
      }
      destpads = g_list_next (destpads);
    }
  }

  GST_DEBUG (GST_CAT_ELEMENT_PADS, "we might have request pads on both sides, checking...");
  srctempls = gst_element_get_pad_template_list (src);
  desttempls = gst_element_get_pad_template_list (dest);
  
  if (srctempls && desttempls) {
    while (srctempls) {
      srctempl = (GstPadTemplate*) srctempls->data;
      if (srctempl->presence == GST_PAD_REQUEST) {
        for (l=desttempls; l; l=l->next) {
          desttempl = (GstPadTemplate*) desttempls->data;
          if (desttempl->presence == GST_PAD_REQUEST && desttempl->direction != srctempl->direction) {
            if (gst_caps_check_compatibility (gst_pad_template_get_caps (srctempl),
                                              gst_pad_template_get_caps (desttempl))) {
              srcpad = gst_element_get_request_pad (src, srctempl->name_template);
              destpad = gst_element_get_request_pad (dest, desttempl->name_template);
              if (gst_pad_connect_filtered (srcpad, destpad, filtercaps)) {
                GST_DEBUG (GST_CAT_ELEMENT_PADS, "connected pad %s:%s to pad %s:%s",
                           GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (destpad));
                return TRUE;
              }
              /* FIXME: we have extraneous request pads lying around */
            }
          }
        }
      }
      srctempls = srctempls->next;
    }
  }
  
  GST_DEBUG (GST_CAT_ELEMENT_PADS, "no connection possible from %s to %s", GST_ELEMENT_NAME (src), GST_ELEMENT_NAME (dest));
  return FALSE;  
}

/**
 * gst_element_connect_many:
 * @element_1: the first element in the connection chain
 * @element_2: the second element in the connection chain
 * @...: NULL-terminated list of elements to connect in order
 * 
 * Chain together a series of elements. Uses #gst_element_connect.
 *
 * Returns: TRUE on success, FALSE otherwise.
 */
gboolean
gst_element_connect_many (GstElement *element_1, GstElement *element_2, ...)
{
  va_list args;

  g_return_val_if_fail (element_1 != NULL && element_2 != NULL, FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (element_1) && GST_IS_ELEMENT (element_2), FALSE);

  va_start (args, element_2);

  while (element_2) {
    if (!gst_element_connect (element_1, element_2))
      return FALSE;
    
    element_1 = element_2;
    element_2 = va_arg (args, GstElement*);
  }

  va_end (args);
  
  return TRUE;
}

/**
 * gst_element_connect:
 * @src: element containing source pad
 * @dest: element containing destination pad
 *
 * Connect the source to the destination element.
 * The connection must be from source to destination, the other
 * direction will not be tried.
 * The functions looks for existing pads and request pads that aren't
 * connected yet. If multiple connections are possible, only one is
 * established.
 *
 * Returns: TRUE if the elements could be connected.
 */
gboolean
gst_element_connect (GstElement *src, GstElement *dest)
{
  return gst_element_connect_filtered (src, dest, NULL);
}

/**
 * gst_element_connect_pads_filtered:
 * @src: element containing source pad
 * @srcpadname: name of pad in source element
 * @dest: element containing destination pad
 * @destpadname: name of pad in destination element
 * @filtercaps: the caps to use as a filter
 *
 * Connect the two named pads of the source and destination elements.
 * Side effect is that if one of the pads has no parent, it becomes a
 * child of the parent of the other element.  If they have different
 * parents, the connection fails.
 *
 * Returns: TRUE if the pads could be connected.
 */
gboolean
gst_element_connect_pads_filtered (GstElement *src, const gchar *srcpadname,
                                   GstElement *dest, const gchar *destpadname, 
                                   GstCaps *filtercaps)
{
  GstPad *srcpad,*destpad;

  g_return_val_if_fail (src != NULL, FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (src), FALSE);
  g_return_val_if_fail (srcpadname != NULL, FALSE);
  g_return_val_if_fail (dest != NULL, FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (dest), FALSE);
  g_return_val_if_fail (destpadname != NULL, FALSE);

  /* obtain the pads requested */
  srcpad = gst_element_get_pad (src, srcpadname);
  if (srcpad == NULL) {
    GST_ERROR (src, "source element has no pad \"%s\"", srcpadname);
    return FALSE;
  }
  destpad = gst_element_get_pad (dest, destpadname);
  if (srcpad == NULL) {
    GST_ERROR (dest, "destination element has no pad \"%s\"", destpadname);
    return FALSE;
  }

  /* we're satisified they can be connected, let's do it */
  return gst_pad_connect_filtered (srcpad, destpad, filtercaps);
}

/**
 * gst_element_connect_pads:
 * @src: element containing source pad
 * @srcpadname: name of pad in source element
 * @dest: element containing destination pad
 * @destpadname: name of pad in destination element
 *
 * Connect the two named pads of the source and destination elements.
 * Side effect is that if one of the pads has no parent, it becomes a
 * child of the parent of the other element.  If they have different
 * parents, the connection fails.
 *
 * Returns: TRUE if the pads could be connected.
 */
gboolean
gst_element_connect_pads (GstElement *src, const gchar *srcpadname,
                          GstElement *dest, const gchar *destpadname)
{
  return gst_element_connect_pads_filtered (src, srcpadname, dest, destpadname, NULL);
}

/**
 * gst_element_disconnect_pads:
 * @src: element containing source pad
 * @srcpadname: name of pad in source element
 * @dest: element containing destination pad
 * @destpadname: name of pad in destination element
 *
 * Disconnect the two named pads of the source and destination elements.
 */
void
gst_element_disconnect_pads (GstElement *src, const gchar *srcpadname,
                             GstElement *dest, const gchar *destpadname)
{
  GstPad *srcpad,*destpad;

  g_return_if_fail (src != NULL);
  g_return_if_fail (GST_IS_ELEMENT(src));
  g_return_if_fail (srcpadname != NULL);
  g_return_if_fail (dest != NULL);
  g_return_if_fail (GST_IS_ELEMENT(dest));
  g_return_if_fail (destpadname != NULL);

  /* obtain the pads requested */
  srcpad = gst_element_get_pad (src, srcpadname);
  if (srcpad == NULL) {
    GST_ERROR(src,"source element has no pad \"%s\"",srcpadname);
    return;
  }
  destpad = gst_element_get_pad (dest, destpadname);
  if (srcpad == NULL) {
    GST_ERROR(dest,"destination element has no pad \"%s\"",destpadname);
    return;
  }

  /* we're satisified they can be disconnected, let's do it */
  gst_pad_disconnect(srcpad,destpad);
}

/**
 * gst_element_disconnect_many:
 * @element_1: the first element in the connection chain
 * @element_2: the second element in the connection chain
 * @...: NULL-terminated list of elements to disconnect in order
 * 
 * Disconnect a series of elements. Uses #gst_element_disconnect.
 */
void
gst_element_disconnect_many (GstElement *element_1, GstElement *element_2, ...)
{
  va_list args;

  g_return_if_fail (element_1 != NULL && element_2 != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element_1) && GST_IS_ELEMENT (element_2));

  va_start (args, element_2);

  while (element_2) {
    gst_element_disconnect (element_1, element_2);
    
    element_1 = element_2;
    element_2 = va_arg (args, GstElement*);
  }

  va_end (args);
}

/**
 * gst_element_disconnect:
 * @src: source element
 * @dest: sink element
 *
 * Disconnect all pads connecting the two elements in the direction src -> dest.
 */
void
gst_element_disconnect (GstElement *src, GstElement *dest)
{
  GList *srcpads;
  GstPad *pad;

  g_return_if_fail (GST_IS_ELEMENT(src));
  g_return_if_fail (GST_IS_ELEMENT(dest));

  srcpads = gst_element_get_pad_list (src);

  while (srcpads) {
    pad = GST_PAD (srcpads->data);
    
    if (GST_PAD_DIRECTION (pad) == GST_PAD_SRC)
      if (GST_OBJECT_PARENT (GST_PAD_PEER (pad)) == (GstObject*) dest)
        gst_pad_disconnect (pad, GST_PAD_PEER (pad));

    srcpads = g_list_next (srcpads);
  }
}

static void
gst_element_error_func (GstElement* element, GstElement *source, gchar *errormsg)
{
  /* tell the parent */
  if (GST_OBJECT_PARENT (element)) {
    GST_DEBUG (GST_CAT_EVENT, "forwarding error \"%s\" from %s to %s", errormsg, 
	       GST_ELEMENT_NAME (element), GST_OBJECT_NAME (GST_OBJECT_PARENT (element)));

    gst_object_ref (GST_OBJECT (element));
    g_signal_emit (G_OBJECT (GST_OBJECT_PARENT (element)), gst_element_signals[ERROR], 0, source, errormsg);
    gst_object_unref (GST_OBJECT (element));
  }
}

/**
 * gst_element_error:
 * @element: Element with the error
 * @error: A printf-like string describing the error
 * @...: optional arguments for the string 
 *
 * This function is used internally by elements to signal an error
 * condition.  It results in the "error" signal.
 */
void
gst_element_error (GstElement *element, const gchar *error, ...)
{
  va_list var_args;
  gchar *string;
  
  /* checks */
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (element != NULL);
  g_return_if_fail (error != NULL);

  /* create error message */
  va_start (var_args, error);
  string = g_strdup_vprintf (error, var_args);
  va_end (var_args);
  GST_INFO (GST_CAT_EVENT, "ERROR in %s: %s", GST_ELEMENT_NAME (element), string);

  /* emit the signal, make sure the element stays available */
  gst_object_ref (GST_OBJECT (element));
  g_signal_emit (G_OBJECT (element), gst_element_signals[ERROR], 0, element, string);
  
 /* tell the scheduler */
  if (element->sched) {
    gst_scheduler_error (element->sched, element); 
  } 

  /* cleanup */
  gst_object_unref (GST_OBJECT (element));
  g_free (string);
}

/**
 * gst_element_get_state:
 * @element: a #GstElement to get state of
 *
 * Gets the state of the element. 
 *
 * Returns: The #GstElementState of the element
 */
GstElementState
gst_element_get_state (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_VOID_PENDING);

  return GST_STATE (element);
}

/**
 * gst_element_wait_state_change:
 * @element: a #GstElement to wait for
 *
 * Waits and blocks until the element changed its state.
 */
void
gst_element_wait_state_change (GstElement *element)
{
  g_mutex_lock (element->state_mutex);
  g_cond_wait (element->state_cond, element->state_mutex);
  g_mutex_unlock (element->state_mutex);
}

/**
 * gst_element_set_state:
 * @element: a #GstElement to change state of
 * @state: the element's new #GstElementState
 *
 * Sets the state of the element. This function will try to set the
 * requested state by going through all the intermediary states and calling
 * the class's state change function for each.
 *
 * Returns: whether or not the state was successfully set 
 * (using #GstElementStateReturn).
 */
gint
gst_element_set_state (GstElement *element, GstElementState state)
{
  GstElementClass *oclass;
  GstElementState curpending;
  GstElementStateReturn return_val = GST_STATE_SUCCESS;

  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_FAILURE);

  /* start with the current state */
  curpending = GST_STATE(element);

  GST_DEBUG_ELEMENT (GST_CAT_STATES, element, "setting state from %s to %s",
                     gst_element_state_get_name (curpending),
                     gst_element_state_get_name (state));

  /* loop until the final requested state is set */
  while (GST_STATE (element) != state 
      && GST_STATE (element) != GST_STATE_VOID_PENDING) {
    /* move the curpending state in the correct direction */
    if (curpending < state) 
      curpending <<= 1;
    else 
      curpending >>= 1;

    /* set the pending state variable */
    /* FIXME: should probably check to see that we don't already have one */
    GST_STATE_PENDING (element) = curpending;

    if (curpending != state) {
      GST_DEBUG_ELEMENT (GST_CAT_STATES, element, 
	                 "intermediate: setting state from %s to %s",
			 gst_element_state_get_name (GST_STATE (element)),
                         gst_element_state_get_name (curpending));
    }

    /* call the state change function so it can set the state */
    oclass = CLASS (element);
    if (oclass->change_state)
      return_val = (oclass->change_state) (element);

    switch (return_val) {
      case GST_STATE_FAILURE:
        GST_DEBUG_ELEMENT (GST_CAT_STATES, element, "have failed change_state return");
        goto exit;
      case GST_STATE_ASYNC:
        GST_DEBUG_ELEMENT (GST_CAT_STATES, element, "element will change state async");
        goto exit;
      case GST_STATE_SUCCESS:
        /* Last thing we do is verify that a successful state change really
         * did change the state... */
        if (GST_STATE (element) != curpending) {
          GST_DEBUG_ELEMENT (GST_CAT_STATES, element, 
			  "element claimed state-change success, but state didn't change %s, %s <-> %s",
                     	  gst_element_state_get_name (GST_STATE (element)),
                     	  gst_element_state_get_name (GST_STATE_PENDING (element)),
                     	  gst_element_state_get_name (curpending));
          return GST_STATE_FAILURE;
	}
        break;
      default:
	/* somebody added a GST_STATE_ and forgot to do stuff here ! */
	g_assert_not_reached ();
    }
  }
exit:

  return return_val;
}

static gboolean
gst_element_negotiate_pads (GstElement *element)
{
  GList *pads = GST_ELEMENT_PADS (element);

  GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, "negotiating pads");

  while (pads) {
    GstPad *pad = GST_PAD (pads->data);
    GstRealPad *srcpad;

    pads = g_list_next (pads);
    
    if (!GST_IS_REAL_PAD (pad))
      continue;

    srcpad = GST_PAD_REALIZE (pad);

    /* if we have a connection on this pad and it doesn't have caps
     * allready, try to negotiate */
    if (GST_PAD_IS_CONNECTED (srcpad) && !GST_PAD_CAPS (srcpad)) {
      GstRealPad *sinkpad;
      GstElementState otherstate;
      GstElement *parent;
      
      sinkpad = GST_RPAD_PEER (GST_PAD_REALIZE (srcpad));

      /* check the parent of the peer pad, if there is no parent do nothing */
      parent = GST_PAD_PARENT (sinkpad);
      if (!parent) 
	continue;

      otherstate = GST_STATE (parent);

      /* swap pads if needed */
      if (!GST_PAD_IS_SRC (srcpad)) {
        GstRealPad *temp;

	temp = srcpad;
	srcpad = sinkpad;
	sinkpad = temp;
      }

      /* only try to negotiate if the peer element is in PAUSED or higher too */
      if (otherstate >= GST_STATE_READY) {
        GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, "perform negotiate for %s:%s and %s:%s",
		      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));
        if (!gst_pad_perform_negotiate (GST_PAD (srcpad), GST_PAD (sinkpad)))
	  return FALSE;
      }
      else {
        GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, "not negotiatiating %s:%s and %s:%s, not in READY yet",
		      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));
      }
    }
  }

  return TRUE;
}

static void
gst_element_clear_pad_caps (GstElement *element)
{
  GList *pads = GST_ELEMENT_PADS (element);

  GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, "clearing pad caps");

  while (pads) {
    GstRealPad *pad = GST_PAD_REALIZE (pads->data);

    if (GST_PAD_CAPS (pad)) {
      GST_PAD_CAPS (pad) = NULL;
    }
    pads = g_list_next (pads);
  }
}

static GstElementStateReturn
gst_element_change_state (GstElement *element)
{
  GstElementState old_state;
  GstObject *parent;
  gint old_pending, old_transition;

  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_FAILURE);

  old_state = GST_STATE (element);
  old_pending = GST_STATE_PENDING (element);
  old_transition = GST_STATE_TRANSITION (element);

  if (old_pending == GST_STATE_VOID_PENDING || old_state == GST_STATE_PENDING (element)) {
    GST_INFO (GST_CAT_STATES, "no state change needed for element %s (VOID_PENDING)", GST_ELEMENT_NAME (element));
    return GST_STATE_SUCCESS;
  }
  
  GST_INFO (GST_CAT_STATES, "%s default handler sets state from %s to %s %d", GST_ELEMENT_NAME (element),
                     gst_element_state_get_name (old_state),
                     gst_element_state_get_name (old_pending),
		     GST_STATE_TRANSITION (element));

  /* we set the state change early for the negotiation functions */
  GST_STATE (element) = old_pending;
  GST_STATE_PENDING (element) = GST_STATE_VOID_PENDING;

  /* if we are going to paused, we try to negotiate the pads */
  if (old_transition == GST_STATE_NULL_TO_READY) {
    if (!gst_element_negotiate_pads (element)) 
      goto failure;
  }
  /* going to the READY state clears all pad caps */
  else if (old_transition == GST_STATE_READY_TO_NULL) {
    gst_element_clear_pad_caps (element);
  }

  /* tell the scheduler if we have one */
  if (element->sched) {
    if (gst_scheduler_state_transition (element->sched, element, old_transition) 
		    != GST_STATE_SUCCESS) {
      goto failure;
    }
  }

  parent = GST_ELEMENT_PARENT (element);

  /* tell our parent about the state change */
  if (parent && GST_IS_BIN (parent)) {
    gst_bin_child_state_change (GST_BIN (parent), old_state, GST_STATE (element), element);
  }

  g_signal_emit (G_OBJECT (element), gst_element_signals[STATE_CHANGE],
		  0, old_state, GST_STATE (element));

  /* signal the state change in case somebody is waiting for us */
  g_mutex_lock (element->state_mutex);
  g_cond_signal (element->state_cond);
  g_mutex_unlock (element->state_mutex);

  return GST_STATE_SUCCESS;

failure:
  /* undo the state change */
  GST_STATE (element) = old_state;
  GST_STATE_PENDING (element) = old_pending;

  return GST_STATE_FAILURE;
}

/**
 * gst_element_get_factory:
 * @element: element to request the factory
 *
 * Retrieves the factory that was used to create this element
 *
 * Returns: the factory used for creating this element
 */
GstElementFactory*
gst_element_get_factory (GstElement *element)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  oclass = CLASS (element);

  return oclass->elementfactory;
}

static void
gst_element_dispose (GObject *object)
{
  GstElement *element = GST_ELEMENT (object);
  GList *pads;
  GstPad *pad;
  
  GST_DEBUG_ELEMENT (GST_CAT_REFCOUNTING, element, "dispose");

  gst_element_set_state (element, GST_STATE_NULL);

  /* first we break all our connections with the ouside */
  if (element->pads) {
    GList *orig;
    orig = pads = g_list_copy (element->pads);
    while (pads) {
      pad = GST_PAD (pads->data);

      if (GST_PAD_PEER (pad)) {
        GST_DEBUG (GST_CAT_REFCOUNTING, "disconnecting pad '%s'",
			GST_OBJECT_NAME (GST_OBJECT (GST_PAD (GST_PAD_PEER (pad)))));
        gst_pad_disconnect (pad, GST_PAD (GST_PAD_PEER (pad)));
      }
      gst_element_remove_pad (element, pad);

      pads = g_list_next (pads);
    }
    g_list_free (orig);
    g_list_free (element->pads);
    element->pads = NULL;
  }

  element->numsrcpads = 0;
  element->numsinkpads = 0;
  element->numpads = 0;
  g_mutex_free (element->state_mutex);
  g_cond_free (element->state_cond);

  G_OBJECT_CLASS (parent_class)->dispose (object);
}

#ifndef GST_DISABLE_LOADSAVE
/**
 * gst_element_save_thyself:
 * @element: GstElement to save
 * @parent: the xml parent node
 *
 * Saves the element as part of the given XML structure
 *
 * Returns: the new xml node
 */
static xmlNodePtr
gst_element_save_thyself (GstObject *object,
		          xmlNodePtr parent)
{
  GList *pads;
  GstElementClass *oclass;
  GParamSpec **specs, *spec;
  gint nspecs, i;
  GValue value = { 0, };
  GstElement *element;

  g_return_val_if_fail (GST_IS_ELEMENT (object), parent);

  element = GST_ELEMENT (object);

  oclass = CLASS (element);

  xmlNewChild(parent, NULL, "name", GST_ELEMENT_NAME(element));

  if (oclass->elementfactory != NULL) {
    GstElementFactory *factory = (GstElementFactory *)oclass->elementfactory;

    xmlNewChild (parent, NULL, "type", GST_OBJECT_NAME (factory));
    xmlNewChild (parent, NULL, "version", factory->details->version);
  }

/* FIXME: what is this? */  
/*  if (element->manager) */
/*    xmlNewChild(parent, NULL, "manager", GST_ELEMENT_NAME(element->manager)); */

  /* params */
  specs = g_object_class_list_properties (G_OBJECT_GET_CLASS (object), &nspecs);
  
  for (i=0; i<nspecs; i++) {
    spec = specs[i];
    if (spec->flags & G_PARAM_READABLE) {
      xmlNodePtr param;
      
      g_value_init(&value, G_PARAM_SPEC_VALUE_TYPE (spec));
      
      g_object_get_property (G_OBJECT (element), spec->name, &value);
      param = xmlNewChild (parent, NULL, "param", NULL);
      xmlNewChild (param, NULL, "name", spec->name);
      
      if (G_IS_PARAM_SPEC_STRING (spec))
        xmlNewChild (param, NULL, "value", g_value_dup_string (&value));
      else if (G_IS_PARAM_SPEC_ENUM (spec))
        xmlNewChild (param, NULL, "value", g_strdup_printf ("%d", g_value_get_enum (&value)));
      else if (G_IS_PARAM_SPEC_INT64 (spec))
        xmlNewChild (param, NULL, "value", g_strdup_printf ("%lld", g_value_get_int64 (&value)));
      else
        xmlNewChild (param, NULL, "value", g_strdup_value_contents (&value));
      
      g_value_unset(&value);
    }
  }

  pads = GST_ELEMENT_PADS (element);

  while (pads) {
    GstPad *pad = GST_PAD (pads->data);
    /* figure out if it's a direct pad or a ghostpad */
    if (GST_ELEMENT (GST_OBJECT_PARENT (pad)) == element) {
      xmlNodePtr padtag = xmlNewChild (parent, NULL, "pad", NULL);
      gst_object_save_thyself (GST_OBJECT (pad), padtag);
    }
    pads = g_list_next (pads);
  }

  return parent;
}

static void
gst_element_restore_thyself (GstObject *object, xmlNodePtr self)
{
  xmlNodePtr children;
  GstElement *element;
  guchar *name = NULL;
  guchar *value = NULL;

  element = GST_ELEMENT (object);
  g_return_if_fail (element != NULL);

  /* parameters */
  children = self->xmlChildrenNode;
  while (children) {
    if (!strcmp (children->name, "param")) {
      xmlNodePtr child = children->xmlChildrenNode;

      while (child) {
        if (!strcmp (child->name, "name")) {
          name = xmlNodeGetContent (child);
	}
	else if (!strcmp (child->name, "value")) {
          value = xmlNodeGetContent (child);
	}
        child = child->next;
      }
      /* FIXME: can this just be g_object_set ? */
      gst_util_set_object_arg ((GObject *)G_OBJECT (element), name, value);
    }
    children = children->next;
  }
  
  /* pads */
  children = self->xmlChildrenNode;
  while (children) {
    if (!strcmp (children->name, "pad")) {
      gst_pad_load_and_connect (children, GST_OBJECT (element));
    }
    children = children->next;
  }

  if (GST_OBJECT_CLASS(parent_class)->restore_thyself)
    (GST_OBJECT_CLASS(parent_class)->restore_thyself) (object, self);
}
#endif /* GST_DISABLE_LOADSAVE */

/**
 * gst_element_yield:
 * @element: Element to yield
 *
 * Request a yield operation for the child. The scheduler will typically
 * give control to another element.
 */
void
gst_element_yield (GstElement *element)
{
  if (GST_ELEMENT_SCHED (element)) {
    gst_scheduler_yield (GST_ELEMENT_SCHED (element), element);
  }
}

/**
 * gst_element_interrupt:
 * @element: Element to interrupt
 *
 * Request the scheduler of this element to interrupt the execution of
 * this element and scheduler another one.
 *
 * Returns: a boolean indicating that the child should exit its chain/loop/get
 * function ASAP, depending on the scheduler implementation.
 */
gboolean
gst_element_interrupt (GstElement *element)
{
  if (GST_ELEMENT_SCHED (element)) {
    return gst_scheduler_interrupt (GST_ELEMENT_SCHED (element), element);
  }
  else 
    return FALSE;
}

/**
 * gst_element_set_sched:
 * @element: Element to set manager of.
 * @sched: @GstScheduler to set.
 *
 * Sets the scheduler of the element.  For internal use only, unless you're
 * writing a new bin subclass.
 */
void
gst_element_set_sched (GstElement *element,
		       GstScheduler *sched)
{
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  GST_INFO_ELEMENT (GST_CAT_PARENTAGE, element, "setting scheduler to %p", sched);

  element->sched = sched;
}

/**
 * gst_element_get_sched:
 * @element: Element to get manager of.
 *
 * Returns the scheduler of the element.
 *
 * Returns: Element's scheduler
 */
GstScheduler*
gst_element_get_sched (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  return element->sched;
}

/**
 * gst_element_set_loop_function:
 * @element: Element to set loop function of.
 * @loop: Pointer to loop function.
 *
 * This sets the loop function for the element.  The function pointed to
 * can deviate from the GstElementLoopFunction definition in type of
 * pointer only.
 *
 * NOTE: in order for this to take effect, the current loop function *must*
 * exit.  Assuming the loop function itself is the only one who will cause
 * a new loopfunc to be assigned, this should be no problem.
 */
void
gst_element_set_loop_function (GstElement *element,
                               GstElementLoopFunction loop)
{
  g_return_if_fail (GST_IS_ELEMENT (element));

  /* set the loop function */
  element->loopfunc = loop;

  /* set the NEW_LOOPFUNC flag so everyone knows to go try again */
  GST_FLAG_SET (element, GST_ELEMENT_NEW_LOOPFUNC);
}

/**
 * gst_element_set_eos:
 * @element: element to set to the EOS state
 *
 * Perform the actions needed to bring the element in the EOS state.
 */
void
gst_element_set_eos (GstElement *element)
{
  g_return_if_fail (GST_IS_ELEMENT (element));

  GST_DEBUG (GST_CAT_EVENT, "setting EOS on element %s", GST_OBJECT_NAME (element));

  gst_element_set_state (element, GST_STATE_PAUSED);

  g_signal_emit (G_OBJECT (element), gst_element_signals[EOS], 0);
}


/**
 * gst_element_state_get_name:
 * @state: a #GstElementState to get the name of
 *
 * Gets a string representing the given state.
 *
 * Returns: a string with the statename.
 */
const gchar*
gst_element_state_get_name (GstElementState state) 
{
  switch (state) {
#ifdef GST_DEBUG_COLOR
    case GST_STATE_VOID_PENDING: return "NONE_PENDING";break;
    case GST_STATE_NULL: return "\033[01;37mNULL\033[00m";break;
    case GST_STATE_READY: return "\033[01;31mREADY\033[00m";break;
    case GST_STATE_PLAYING: return "\033[01;32mPLAYING\033[00m";break;
    case GST_STATE_PAUSED: return "\033[01;33mPAUSED\033[00m";break;
    default: return g_strdup_printf ("\033[01;37;41mUNKNOWN!\033[00m(%d)", state);
#else
    case GST_STATE_VOID_PENDING: return "NONE_PENDING";break;
    case GST_STATE_NULL: return "NULL";break;
    case GST_STATE_READY: return "READY";break;
    case GST_STATE_PLAYING: return "PLAYING";break;
    case GST_STATE_PAUSED: return "PAUSED";break;
    default: return "UNKNOWN!";
#endif
  }
  return "";
}

static void
gst_element_populate_std_props (GObjectClass * klass,
				const char *prop_name, guint arg_id, GParamFlags flags)
{
  GQuark prop_id = g_quark_from_string (prop_name);
  GParamSpec *pspec;

  static GQuark fd_id = 0;
  static GQuark blocksize_id;
  static GQuark bytesperread_id;
  static GQuark dump_id;
  static GQuark filesize_id;
  static GQuark mmapsize_id;
  static GQuark location_id;
  static GQuark offset_id;
  static GQuark silent_id;
  static GQuark touch_id;

  if (!fd_id) {
    fd_id = g_quark_from_static_string ("fd");
    blocksize_id = g_quark_from_static_string ("blocksize");
    bytesperread_id = g_quark_from_static_string ("bytesperread");
    dump_id = g_quark_from_static_string ("dump");
    filesize_id = g_quark_from_static_string ("filesize");
    mmapsize_id = g_quark_from_static_string ("mmapsize");
    location_id = g_quark_from_static_string ("location");
    offset_id = g_quark_from_static_string ("offset");
    silent_id = g_quark_from_static_string ("silent");
    touch_id = g_quark_from_static_string ("touch");
  }

  if (prop_id == fd_id) {
    pspec = g_param_spec_int ("fd", "File-descriptor",
			      "File-descriptor for the file being read",
			      0, G_MAXINT, 0, flags);
  }
  else if (prop_id == blocksize_id) {
    pspec = g_param_spec_ulong ("blocksize", "Block Size",
				"Block size to read per buffer",
				0, G_MAXULONG, 4096, flags);

  }
  else if (prop_id == bytesperread_id) {
    pspec = g_param_spec_int ("bytesperread", "Bytes per read",
			      "Number of bytes to read per buffer",
			      G_MININT, G_MAXINT, 0, flags);

  }
  else if (prop_id == dump_id) {
    pspec = g_param_spec_boolean ("dump", "Dump", "Dump bytes to stdout", FALSE, flags);

  }
  else if (prop_id == filesize_id) {
    pspec = g_param_spec_int64 ("filesize", "File Size",
				"Size of the file being read",
				0, G_MAXINT64, 0, flags);

  }
  else if (prop_id == mmapsize_id) {
    pspec = g_param_spec_ulong ("mmapsize", "mmap() Block Size",
				"Size in bytes of mmap()d regions",
				0, G_MAXULONG, 4 * 1048576, flags);

  }
  else if (prop_id == location_id) {
    pspec = g_param_spec_string ("location", "File Location",
				 "Location of the file to read",
				 NULL, flags);

  }
  else if (prop_id == offset_id) {
    pspec = g_param_spec_int64 ("offset", "File Offset",
				"Byte offset of current read pointer",
				0, G_MAXINT64, 0, flags);

  }
  else if (prop_id == silent_id) {
    pspec = g_param_spec_boolean ("silent", "Silent", "Don't produce events",
				  FALSE, flags);

  }
  else if (prop_id == touch_id) {
    pspec = g_param_spec_boolean ("touch", "Touch read data",
				  "Touch data to force disk read before "
				  "push ()", TRUE, flags);
  }
  else {
    g_warning ("Unknown - 'standard' property '%s' id %d from klass %s",
               prop_name, arg_id, g_type_name (G_OBJECT_CLASS_TYPE (klass)));
    pspec = NULL;
  }

  if (pspec) {
    g_object_class_install_property (klass, arg_id, pspec);
  }
}

/**
 * gst_element_class_install_std_props:
 * @klass: the class to add the properties to
 * @first_name: the first in a NULL terminated
 * 'name', 'id', 'flags' triplet list.
 * @...: the triplet list
 * 
 * Add a list of standardized properties with types to the @klass.
 * the id is for the property switch in your get_prop method, and
 * the flags determine readability / writeability.
 **/
void
gst_element_class_install_std_props (GstElementClass * klass, const char *first_name, ...)
{
  const char *name;

  va_list args;

  g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));

  va_start (args, first_name);

  name = first_name;

  while (name) {
    int arg_id = va_arg (args, int);
    int flags = va_arg (args, int);

    gst_element_populate_std_props ((GObjectClass *) klass, name, arg_id, flags);

    name = va_arg (args, char *);
  }

  va_end (args);
}

/**
 * gst_element_get_managing_bin:
 * @element: a #GstElement
 * 
 * Gets the managing bin (a pipeline or a thread, for example) of an element.
 *
 * Returns: the #GstBin, or NULL on failure
 **/
GstBin*
gst_element_get_managing_bin (GstElement *element)
{
  GstBin *bin;

  g_return_val_if_fail (element != NULL, NULL);

  bin = GST_BIN (gst_object_get_parent (GST_OBJECT_CAST (element)));

  while (bin && !GST_FLAG_IS_SET (GST_OBJECT_CAST (bin), GST_BIN_FLAG_MANAGER))
    bin = GST_BIN (gst_object_get_parent (GST_OBJECT_CAST (bin)));
  
  return bin;
}