/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gstscheduler.c: Default scheduling code for most cases
 *
 * 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.
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include <gst/gst.h>

#include "cothreads_compat.h"

GST_DEBUG_CATEGORY_STATIC (debug_dataflow);
GST_DEBUG_CATEGORY_STATIC (debug_scheduler);
#define GST_CAT_DEFAULT debug_scheduler

typedef struct _GstSchedulerChain GstSchedulerChain;

#define GST_ELEMENT_THREADSTATE(elem)	(GST_ELEMENT (elem)->sched_private)
#define GST_RPAD_BUFPEN(pad)		(GST_REAL_PAD(pad)->sched_private)

#define GST_ELEMENT_COTHREAD_STOPPING			GST_ELEMENT_SCHEDULER_PRIVATE1
#define GST_ELEMENT_IS_COTHREAD_STOPPING(element)	GST_FLAG_IS_SET((element), GST_ELEMENT_COTHREAD_STOPPING)

typedef struct _GstBasicScheduler GstBasicScheduler;
typedef struct _GstBasicSchedulerClass GstBasicSchedulerClass;

#ifdef _COTHREADS_STANDARD
# define _SCHEDULER_NAME "standard"
#else
# define _SCHEDULER_NAME "basic"
#endif

struct _GstSchedulerChain
{
  GstBasicScheduler *sched;

  GList *disabled;

  GList *elements;
  gint num_elements;

  GstElement *entry;

  gint cothreaded_elements;
  gboolean schedule;
};

#define GST_TYPE_BASIC_SCHEDULER \
  (gst_basic_scheduler_get_type())
#define GST_BASIC_SCHEDULER(obj) \
  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_BASIC_SCHEDULER,GstBasicScheduler))
#define GST_BASIC_SCHEDULER_CLASS(klass) \
  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_BASIC_SCHEDULER,GstBasicSchedulerClass))
#define GST_IS_BASIC_SCHEDULER(obj) \
  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_BASIC_SCHEDULER))
#define GST_IS_BASIC_SCHEDULER_CLASS(obj) \
  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_BASIC_SCHEDULER))

#define SCHED(element) GST_BASIC_SCHEDULER (GST_ELEMENT_SCHEDULER (element))

typedef enum
{
  GST_BASIC_SCHEDULER_STATE_NONE,
  GST_BASIC_SCHEDULER_STATE_STOPPED,
  GST_BASIC_SCHEDULER_STATE_ERROR,
  GST_BASIC_SCHEDULER_STATE_RUNNING
}
GstBasicSchedulerState;

typedef enum
{
  /* something important has changed inside the scheduler */
  GST_BASIC_SCHEDULER_CHANGE = GST_SCHEDULER_FLAG_LAST
}
GstBasicSchedulerFlags;

struct _GstBasicScheduler
{
  GstScheduler parent;

  GList *elements;
  gint num_elements;

  GList *chains;
  gint num_chains;

  GstBasicSchedulerState state;

  cothread_context *context;
  GstElement *current;
};

struct _GstBasicSchedulerClass
{
  GstSchedulerClass parent_class;
};

static GType _gst_basic_scheduler_type = 0;

static void gst_basic_scheduler_class_init (GstBasicSchedulerClass * klass);
static void gst_basic_scheduler_init (GstBasicScheduler * scheduler);

static void gst_basic_scheduler_dispose (GObject * object);

static void gst_basic_scheduler_setup (GstScheduler * sched);
static void gst_basic_scheduler_reset (GstScheduler * sched);
static void gst_basic_scheduler_add_element (GstScheduler * sched,
    GstElement * element);
static void gst_basic_scheduler_remove_element (GstScheduler * sched,
    GstElement * element);
static GstElementStateReturn gst_basic_scheduler_state_transition (GstScheduler
    * sched, GstElement * element, gint transition);
static gboolean gst_basic_scheduler_yield (GstScheduler * sched,
    GstElement * element);
static gboolean gst_basic_scheduler_interrupt (GstScheduler * sched,
    GstElement * element);
static void gst_basic_scheduler_error (GstScheduler * sched,
    GstElement * element);
static void gst_basic_scheduler_pad_link (GstScheduler * sched, GstPad * srcpad,
    GstPad * sinkpad);
static void gst_basic_scheduler_pad_unlink (GstScheduler * sched,
    GstPad * srcpad, GstPad * sinkpad);
static GstData *gst_basic_scheduler_pad_select (GstScheduler * sched,
    GstPad ** selected, GstPad ** padlist);
static GstSchedulerState gst_basic_scheduler_iterate (GstScheduler * sched);

static void gst_basic_scheduler_show (GstScheduler * sched);

static GstSchedulerClass *parent_class = NULL;

/* for threaded bins, these pre- and post-run functions lock and unlock the
 * elements. we have to avoid deadlocks, so we make these convenience macros
 * that will avoid using do_cothread_switch from within the scheduler. */

#define do_element_switch(element) G_STMT_START{		\
  SCHED (element)->current = element;				\
  do_cothread_switch (GST_ELEMENT_THREADSTATE (element));	\
}G_STMT_END

#define do_switch_to_main(sched) G_STMT_START{			\
  ((GstBasicScheduler*) sched)->current = NULL;				\
  do_cothread_switch						\
    (do_cothread_get_main					\
       (((GstBasicScheduler*)sched)->context));			\
}G_STMT_END

#define do_switch_from_main(entry) G_STMT_START{		\
  SCHED (entry)->current = entry;				\
  do_cothread_switch (GST_ELEMENT_THREADSTATE (entry));		\
}G_STMT_END

static GType
gst_basic_scheduler_get_type (void)
{
  if (!_gst_basic_scheduler_type) {
    static const GTypeInfo scheduler_info = {
      sizeof (GstBasicSchedulerClass),
      NULL,
      NULL,
      (GClassInitFunc) gst_basic_scheduler_class_init,
      NULL,
      NULL,
      sizeof (GstBasicScheduler),
      0,
      (GInstanceInitFunc) gst_basic_scheduler_init,
      NULL
    };

    _gst_basic_scheduler_type =
        g_type_register_static (GST_TYPE_SCHEDULER,
        "Gst" COTHREADS_NAME_CAPITAL "Scheduler", &scheduler_info, 0);
  }
  return _gst_basic_scheduler_type;
}

static void
gst_basic_scheduler_class_init (GstBasicSchedulerClass * klass)
{
  GObjectClass *gobject_class;
  GstObjectClass *gstobject_class;
  GstSchedulerClass *gstscheduler_class;

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

  parent_class = g_type_class_ref (GST_TYPE_SCHEDULER);

  gobject_class->dispose = GST_DEBUG_FUNCPTR (gst_basic_scheduler_dispose);

  gstscheduler_class->setup = GST_DEBUG_FUNCPTR (gst_basic_scheduler_setup);
  gstscheduler_class->reset = GST_DEBUG_FUNCPTR (gst_basic_scheduler_reset);
  gstscheduler_class->add_element =
      GST_DEBUG_FUNCPTR (gst_basic_scheduler_add_element);
  gstscheduler_class->remove_element =
      GST_DEBUG_FUNCPTR (gst_basic_scheduler_remove_element);
  gstscheduler_class->state_transition =
      GST_DEBUG_FUNCPTR (gst_basic_scheduler_state_transition);
  gstscheduler_class->yield = GST_DEBUG_FUNCPTR (gst_basic_scheduler_yield);
  gstscheduler_class->interrupt =
      GST_DEBUG_FUNCPTR (gst_basic_scheduler_interrupt);
  gstscheduler_class->error = GST_DEBUG_FUNCPTR (gst_basic_scheduler_error);
  gstscheduler_class->pad_link =
      GST_DEBUG_FUNCPTR (gst_basic_scheduler_pad_link);
  gstscheduler_class->pad_unlink =
      GST_DEBUG_FUNCPTR (gst_basic_scheduler_pad_unlink);
  gstscheduler_class->pad_select =
      GST_DEBUG_FUNCPTR (gst_basic_scheduler_pad_select);
  gstscheduler_class->clock_wait = NULL;
  gstscheduler_class->iterate = GST_DEBUG_FUNCPTR (gst_basic_scheduler_iterate);

  gstscheduler_class->show = GST_DEBUG_FUNCPTR (gst_basic_scheduler_show);

  do_cothreads_init (NULL);
}

static void
gst_basic_scheduler_init (GstBasicScheduler * scheduler)
{
  scheduler->elements = NULL;
  scheduler->num_elements = 0;
  scheduler->chains = NULL;
  scheduler->num_chains = 0;

  GST_FLAG_SET (scheduler, GST_SCHEDULER_FLAG_NEW_API);
}

static void
gst_basic_scheduler_dispose (GObject * object)
{
  G_OBJECT_CLASS (parent_class)->dispose (object);
}

static gboolean
plugin_init (GstPlugin * plugin)
{
  if (!gst_scheduler_register (plugin, "basic" COTHREADS_NAME,
          "A basic scheduler using " COTHREADS_NAME " cothreads",
          gst_basic_scheduler_get_type ()))
    return FALSE;

  GST_DEBUG_CATEGORY_INIT (debug_dataflow, "basic_dataflow", 0,
      "basic scheduler dataflow");
  GST_DEBUG_CATEGORY_INIT (debug_scheduler, "basic_scheduler", 0,
      "basic scheduler general information");

  return TRUE;
}

GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    "gstbasic" COTHREADS_NAME "scheduler",
    "a basic scheduler using " COTHREADS_NAME " cothreads",
    plugin_init, VERSION, GST_LICENSE, GST_PACKAGE, GST_ORIGIN)

     static int gst_basic_scheduler_loopfunc_wrapper (int argc, char **argv)
{
  GstElement *element = GST_ELEMENT (argv);
  G_GNUC_UNUSED const gchar *name = GST_ELEMENT_NAME (element);

  GST_DEBUG ("entering loopfunc wrapper of %s", name);

  gst_object_ref (GST_OBJECT (element));
  do {
    GST_CAT_DEBUG (debug_dataflow, "calling loopfunc %s for element %s",
        GST_DEBUG_FUNCPTR_NAME (element->loopfunc), name);
    (element->loopfunc) (element);
    GST_CAT_DEBUG (debug_dataflow, "element %s ended loop function", name);

  } while (!GST_ELEMENT_IS_COTHREAD_STOPPING (element));
  GST_FLAG_UNSET (element, GST_ELEMENT_COTHREAD_STOPPING);

  /* due to oddities in the cothreads code, when this function returns it will
   * switch to the main cothread. thus, we need to unlock the current element. */
  if (SCHED (element)) {
    SCHED (element)->current = NULL;
  }

  GST_DEBUG ("leaving loopfunc wrapper of %s", name);
  gst_object_unref (GST_OBJECT (element));

  return 0;
}

static int
gst_basic_scheduler_chain_wrapper (int argc, char **argv)
{
  GSList *already_iterated = NULL;
  GstElement *element = GST_ELEMENT (argv);
  G_GNUC_UNUSED const gchar *name = GST_ELEMENT_NAME (element);

  GST_DEBUG ("entered chain wrapper of element %s", name);

  GST_CAT_DEBUG (debug_dataflow, "stepping through pads");

  gst_object_ref (GST_OBJECT (element));
  do {
    GList *pads;

    do {
      pads = element->pads;

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

        if (!GST_IS_REAL_PAD (pad))
          continue;

        realpad = GST_REAL_PAD (pad);

        if (GST_RPAD_DIRECTION (realpad) == GST_PAD_SINK &&
            GST_PAD_IS_LINKED (realpad) &&
            g_slist_find (already_iterated, pad) == NULL) {
          GstData *data;

          GST_CAT_DEBUG (debug_dataflow, "pulling data from %s:%s", name,
              GST_PAD_NAME (pad));
          data = gst_pad_pull (pad);
          if (data) {
            if (GST_IS_EVENT (data) && !GST_ELEMENT_IS_EVENT_AWARE (element)) {
              gst_pad_send_event (pad, GST_EVENT (data));
            } else {
              GST_CAT_DEBUG (debug_dataflow,
                  "calling chain function of %s:%s %p", name,
                  GST_PAD_NAME (pad), data);
              gst_pad_call_chain_function (GST_PAD (realpad), data);
              GST_CAT_DEBUG (debug_dataflow,
                  "calling chain function of element %s done", name);
            }
          }
          already_iterated = g_slist_prepend (already_iterated, pad);
          break;
        }
        pads = g_list_next (pads);
      }
    } while (pads != NULL);
    if (already_iterated == NULL) {
      GST_DEBUG_OBJECT (SCHED (element), "nothing to iterate for element %s",
          GST_ELEMENT_NAME (element));
      break;
    }
    g_slist_free (already_iterated);
    already_iterated = NULL;
  } while (!GST_ELEMENT_IS_COTHREAD_STOPPING (element));

  GST_FLAG_UNSET (element, GST_ELEMENT_COTHREAD_STOPPING);

  /* due to oddities in the cothreads code, when this function returns it will
   * switch to the main cothread. thus, we need to unlock the current element. */
  if (SCHED (element)) {
    SCHED (element)->current = NULL;
  }

  GST_CAT_DEBUG (debug_dataflow, "leaving chain wrapper of element %s", name);
  gst_object_unref (GST_OBJECT (element));

  return 0;
}

static int
gst_basic_scheduler_src_wrapper (int argc, char **argv)
{
  GstElement *element = GST_ELEMENT (argv);
  GList *pads;
  GstRealPad *realpad;
  GstData *data = NULL;
  gboolean inf_loop;
  G_GNUC_UNUSED const gchar *name = GST_ELEMENT_NAME (element);

  GST_DEBUG ("entering src wrapper of element %s", name);

  do {
    inf_loop = TRUE;
    pads = element->pads;
    while (pads) {

      if (!GST_IS_REAL_PAD (pads->data))
        continue;

      realpad = GST_REAL_PAD (pads->data);

      pads = g_list_next (pads);
      if (GST_RPAD_DIRECTION (realpad) == GST_PAD_SRC) {
        inf_loop = FALSE;
        GST_CAT_DEBUG (debug_dataflow, "calling _getfunc for %s:%s",
            GST_DEBUG_PAD_NAME (realpad));
        data = gst_pad_call_get_function (GST_PAD (realpad));
        if (data) {
          GST_CAT_DEBUG (debug_dataflow, "calling gst_pad_push on pad %s:%s %p",
              GST_DEBUG_PAD_NAME (realpad), data);
          gst_pad_push (GST_PAD (realpad), data);
        }
      }
    }
  } while (!GST_ELEMENT_IS_COTHREAD_STOPPING (element) && !inf_loop);

  GST_FLAG_UNSET (element, GST_ELEMENT_COTHREAD_STOPPING);

  /* due to oddities in the cothreads code, when this function returns it will
   * switch to the main cothread. thus, we need to unlock the current element. */
  SCHED (element)->current = NULL;

  GST_DEBUG ("leaving src wrapper of element %s", name);

  return 0;
}

static void
gst_basic_scheduler_chainhandler_proxy (GstPad * pad, GstData * data)
{
  gint loop_count = 100;
  GstElement *parent;
  GstRealPad *peer;

  parent = GST_PAD_PARENT (pad);
  peer = GST_RPAD_PEER (pad);

  GST_CAT_DEBUG (debug_dataflow, "putting buffer %p in peer \"%s:%s\"'s pen",
      data, GST_DEBUG_PAD_NAME (peer));

  /* 
   * loop until the bufferpen is empty so we can fill it up again
   */
  while (GST_RPAD_BUFPEN (GST_RPAD_PEER (pad)) != NULL && --loop_count) {
    GST_CAT_DEBUG (debug_dataflow, "switching to %p to empty bufpen %d",
        GST_ELEMENT_THREADSTATE (parent), loop_count);

    do_element_switch (parent);

    /* we may no longer be the same pad, check. */
    if (GST_RPAD_PEER (peer) != (GstRealPad *) pad) {
      GST_CAT_DEBUG (debug_dataflow, "new pad in mid-switch!");
      pad = (GstPad *) GST_RPAD_PEER (peer);
    }
    parent = GST_PAD_PARENT (pad);
    peer = GST_RPAD_PEER (pad);
  }

  if (loop_count == 0) {
    GST_ELEMENT_ERROR (parent, CORE, SCHEDULER, (NULL),
        ("(internal error) basic: maximum number of switches exceeded"));
    return;
  }

  g_assert (GST_RPAD_BUFPEN (GST_RPAD_PEER (pad)) == NULL);

  /* now fill the bufferpen and switch so it can be consumed */
  GST_RPAD_BUFPEN (GST_RPAD_PEER (pad)) = data;
  GST_CAT_DEBUG (debug_dataflow, "switching to %p to consume buffer %p",
      GST_ELEMENT_THREADSTATE (GST_PAD_PARENT (pad)), data);

  do_element_switch (parent);

  GST_CAT_DEBUG (debug_dataflow, "leaving chainhandler proxy of %s:%s",
      GST_DEBUG_PAD_NAME (pad));
}

static void
gst_basic_scheduler_select_proxy (GstPad * pad, GstData * data)
{
  GstElement *parent;

  parent = GST_PAD_PARENT (pad);

  GST_CAT_DEBUG (debug_dataflow, "putting buffer %p in peer's pen of pad %s:%s",
      data, GST_DEBUG_PAD_NAME (pad));

  g_assert (GST_RPAD_BUFPEN (GST_RPAD_PEER (pad)) == NULL);
  /* now fill the bufferpen and switch so it can be consumed */
  GST_RPAD_BUFPEN (GST_RPAD_PEER (pad)) = data;
  GST_CAT_DEBUG (debug_dataflow, "switching to %p",
      GST_ELEMENT_THREADSTATE (parent));
  /* FIXME temporarily diabled */
  /* parent->select_pad = pad; */

  do_element_switch (parent);

  GST_CAT_DEBUG (debug_dataflow, "done switching");
}


static GstData *
gst_basic_scheduler_gethandler_proxy (GstPad * pad)
{
  GstData *data;
  GstElement *parent;
  GstRealPad *peer;

  GST_CAT_DEBUG (debug_dataflow, "entering gethandler proxy of %s:%s",
      GST_DEBUG_PAD_NAME (pad));

  parent = GST_PAD_PARENT (pad);
  peer = GST_RPAD_PEER (pad);

  /* FIXME this should be bounded */
  /* we will loop switching to the peer until it's filled up the bufferpen */
  while (GST_RPAD_BUFPEN (pad) == NULL) {

    GST_CAT_DEBUG (debug_dataflow, "switching to \"%s\": %p to fill bufpen",
        GST_ELEMENT_NAME (parent), GST_ELEMENT_THREADSTATE (parent));

    do_element_switch (parent);

    /* we may no longer be the same pad, check. */
    if (GST_RPAD_PEER (peer) != (GstRealPad *) pad) {
      GST_CAT_DEBUG (debug_dataflow, "new pad in mid-switch!");
      pad = (GstPad *) GST_RPAD_PEER (peer);
      if (!pad) {
        GST_ELEMENT_ERROR (parent, CORE, PAD, (NULL), ("pad unlinked"));
      }
      parent = GST_PAD_PARENT (pad);
      peer = GST_RPAD_PEER (pad);
    }
  }
  GST_CAT_DEBUG (debug_dataflow, "done switching");

  /* now grab the buffer from the pen, clear the pen, and return the buffer */
  data = GST_RPAD_BUFPEN (pad);
  GST_RPAD_BUFPEN (pad) = NULL;

  GST_CAT_DEBUG (debug_dataflow, "leaving gethandler proxy of %s:%s",
      GST_DEBUG_PAD_NAME (pad));

  return data;
}

static gboolean
gst_basic_scheduler_eventhandler_proxy (GstPad * srcpad, GstEvent * event)
{
  gboolean flush;

  GST_CAT_INFO (debug_dataflow, "intercepting event %d on pad %s:%s",
      GST_EVENT_TYPE (event), GST_DEBUG_PAD_NAME (srcpad));

  /* figure out if we need to flush */
  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_FLUSH:
      flush = TRUE;
      break;
    case GST_EVENT_SEEK:
    case GST_EVENT_SEEK_SEGMENT:
      flush = GST_EVENT_SEEK_FLAGS (event) & GST_SEEK_FLAG_FLUSH;
      break;
    default:
      flush = FALSE;
      break;
  }

  if (flush) {
    GstData *data = GST_RPAD_BUFPEN (srcpad);

    GST_CAT_INFO (debug_dataflow, "event is flush");

    if (data) {
      GST_CAT_INFO (debug_dataflow, "need to clear some buffers");

      gst_data_unref (data);
      GST_RPAD_BUFPEN (srcpad) = NULL;
    }
  }
  return GST_RPAD_EVENTFUNC (srcpad) (srcpad, event);
}

static gboolean
gst_basic_scheduler_cothreaded_chain (GstBin * bin, GstSchedulerChain * chain)
{
  GList *elements;
  GstElement *element;
  cothread_func wrapper_function;
  const GList *pads;
  GstPad *pad;

  GST_DEBUG ("chain is using COTHREADS");

  g_assert (chain->sched->context != NULL);

  /* walk through all the chain's elements */
  elements = chain->elements;
  while (elements) {
    gboolean decoupled;

    element = GST_ELEMENT (elements->data);
    elements = g_list_next (elements);

    decoupled = GST_FLAG_IS_SET (element, GST_ELEMENT_DECOUPLED);

    /* start out without a wrapper function, we select it later */
    wrapper_function = NULL;

    /* if the element has a loopfunc... */
    if (element->loopfunc != NULL) {
      wrapper_function =
          GST_DEBUG_FUNCPTR (gst_basic_scheduler_loopfunc_wrapper);
      GST_DEBUG ("element '%s' is a loop-based", GST_ELEMENT_NAME (element));
    } else {
      /* otherwise we need to decide what kind of cothread
       * if it's not DECOUPLED, we decide based on 
       * whether it's a source or not */
      if (!decoupled) {
        /* if it doesn't have any sinks, it must be a source (duh) */
        if (element->numsinkpads == 0) {
          wrapper_function =
              GST_DEBUG_FUNCPTR (gst_basic_scheduler_src_wrapper);
          GST_DEBUG ("element '%s' is a source, using _src_wrapper",
              GST_ELEMENT_NAME (element));
        } else {
          wrapper_function =
              GST_DEBUG_FUNCPTR (gst_basic_scheduler_chain_wrapper);
          GST_DEBUG ("element '%s' is a filter, using _chain_wrapper",
              GST_ELEMENT_NAME (element));
        }
      }
    }

    /* now we have to walk through the pads to set up their state */
    pads = element->pads;
    while (pads) {
      GstPad *peerpad;

      pad = GST_PAD (pads->data);
      pads = g_list_next (pads);

      if (!GST_IS_REAL_PAD (pad))
        continue;

      peerpad = GST_PAD_PEER (pad);
      if (peerpad) {
        GstElement *peerelement = GST_ELEMENT (GST_PAD_PARENT (peerpad));
        gboolean different_sched =
            (peerelement->scheduler != GST_SCHEDULER (chain->sched));
        gboolean peer_decoupled =
            GST_FLAG_IS_SET (peerelement, GST_ELEMENT_DECOUPLED);

        GST_DEBUG ("inspecting pad %s:%s", GST_DEBUG_PAD_NAME (peerpad));

        /* we don't need to check this for decoupled elements */
        if (!decoupled) {
          /* if the peer element is in another schedule, 
           * it's not decoupled and we are not decoupled
           * either, we have an error */
          if (different_sched && !peer_decoupled) {
            GST_ELEMENT_ERROR (element, CORE, SCHEDULER, (NULL),
                ("element \"%s\" is not decoupled but has pads in different schedulers",
                    GST_ELEMENT_NAME (element)));
            return FALSE;
          }
          /* ok, the peer is in a different scheduler and is decoupled, 
           * we need to set the
           * handlers so we can talk with it */
          else if (different_sched) {
            if (GST_RPAD_DIRECTION (peerpad) == GST_PAD_SINK) {
              GST_DEBUG ("copying chain func into push proxy for peer %s:%s",
                  GST_DEBUG_PAD_NAME (peerpad));
              GST_RPAD_CHAINHANDLER (peerpad) = gst_pad_call_chain_function;
            } else {
              GST_DEBUG ("copying get func into pull proxy for peer %s:%s",
                  GST_DEBUG_PAD_NAME (peerpad));
              GST_RPAD_GETHANDLER (peerpad) = gst_pad_call_get_function;
            }
          }
        }
        /* in any case we need to copy the eventfunc into the handler */
        GST_RPAD_EVENTHANDLER (peerpad) = GST_RPAD_EVENTFUNC (peerpad);
      }

      /* if the element is DECOUPLED or outside the manager, we have to chain */
      if (decoupled) {
        /* set the chain proxies */
        if (GST_RPAD_DIRECTION (pad) == GST_PAD_SINK) {
          GST_DEBUG ("copying chain function into push proxy for %s:%s",
              GST_DEBUG_PAD_NAME (pad));
          GST_RPAD_CHAINHANDLER (pad) = gst_pad_call_chain_function;
        } else {
          GST_DEBUG ("copying get function into pull proxy for %s:%s",
              GST_DEBUG_PAD_NAME (pad));
          GST_RPAD_GETHANDLER (pad) = gst_pad_call_get_function;
        }
      }
      /* otherwise we really are a cothread */
      else {
        if (GST_RPAD_DIRECTION (pad) == GST_PAD_SINK) {
          GST_DEBUG ("setting cothreaded push proxy for sinkpad %s:%s",
              GST_DEBUG_PAD_NAME (pad));
          GST_RPAD_CHAINHANDLER (pad) =
              GST_DEBUG_FUNCPTR (gst_basic_scheduler_chainhandler_proxy);
          GST_RPAD_EVENTHANDLER (pad) = GST_RPAD_EVENTFUNC (pad);
        } else {
          GST_DEBUG ("setting cothreaded pull proxy for srcpad %s:%s",
              GST_DEBUG_PAD_NAME (pad));
          GST_RPAD_GETHANDLER (pad) =
              GST_DEBUG_FUNCPTR (gst_basic_scheduler_gethandler_proxy);
          /* the gethandler proxy function can queue a buffer in the bufpen, we need
           * to remove this buffer when a flush event is sent on the pad */
          GST_RPAD_EVENTHANDLER (pad) =
              GST_DEBUG_FUNCPTR (gst_basic_scheduler_eventhandler_proxy);
        }
      }
    }

    /* need to set up the cothread now */
    if (wrapper_function != NULL) {
      if (GST_ELEMENT_THREADSTATE (element) == NULL) {
        GST_DEBUG ("about to create a cothread, wrapper for '%s' is &%s",
            GST_ELEMENT_NAME (element),
            GST_DEBUG_FUNCPTR_NAME (wrapper_function));
        do_cothread_create (GST_ELEMENT_THREADSTATE (element),
            chain->sched->context, wrapper_function, 0, (char **) element);
        if (GST_ELEMENT_THREADSTATE (element) == NULL) {
          GST_ELEMENT_ERROR (element, RESOURCE, TOO_LAZY, (NULL),
              ("could not create cothread for \"%s\"",
                  GST_ELEMENT_NAME (element)));
          return FALSE;
        }
        GST_DEBUG ("created cothread %p for '%s'",
            GST_ELEMENT_THREADSTATE (element), GST_ELEMENT_NAME (element));
      } else {
        /* set the cothread wrapper function */
        GST_DEBUG ("about to set the wrapper function for '%s' to &%s",
            GST_ELEMENT_NAME (element),
            GST_DEBUG_FUNCPTR_NAME (wrapper_function));
        do_cothread_setfunc (GST_ELEMENT_THREADSTATE (element),
            chain->sched->context, wrapper_function, 0, (char **) element);
        GST_DEBUG ("set wrapper function for '%s' to &%s",
            GST_ELEMENT_NAME (element),
            GST_DEBUG_FUNCPTR_NAME (wrapper_function));
      }
    }
  }

  return TRUE;
}

static GstSchedulerChain *
gst_basic_scheduler_chain_new (GstBasicScheduler * sched)
{
  GstSchedulerChain *chain = g_new (GstSchedulerChain, 1);

  /* initialize the chain with sane values */
  chain->sched = sched;
  chain->disabled = NULL;
  chain->elements = NULL;
  chain->num_elements = 0;
  chain->entry = NULL;
  chain->cothreaded_elements = 0;
  chain->schedule = FALSE;

  /* add the chain to the schedulers' list of chains */
  sched->chains = g_list_prepend (sched->chains, chain);
  sched->num_chains++;

  /* notify the scheduler that something changed */
  GST_FLAG_SET (sched, GST_BASIC_SCHEDULER_CHANGE);

  GST_INFO ("created new chain %p, now are %d chains in sched %p",
      chain, sched->num_chains, sched);

  return chain;
}

static void
gst_basic_scheduler_chain_destroy (GstSchedulerChain * chain)
{
  GstBasicScheduler *sched = chain->sched;

  /* remove the chain from the schedulers' list of chains */
  sched->chains = g_list_remove (sched->chains, chain);
  sched->num_chains--;

  /* destroy the chain */
  g_list_free (chain->disabled);        /* should be empty... */
  g_list_free (chain->elements);        /* ditto              */

  GST_INFO ("destroyed chain %p, now are %d chains in sched %p", chain,
      sched->num_chains, sched);

  g_free (chain);

  /* notify the scheduler that something changed */
  GST_FLAG_SET (sched, GST_BASIC_SCHEDULER_CHANGE);
}

static void
gst_basic_scheduler_chain_add_element (GstSchedulerChain * chain,
    GstElement * element)
{
  /* set the sched pointer for the element */
  element->scheduler = GST_SCHEDULER (chain->sched);

  /* add the element to either the main list or the disabled list */
  if (GST_STATE (element) == GST_STATE_PLAYING) {
    GST_INFO ("adding element \"%s\" to chain %p enabled",
        GST_ELEMENT_NAME (element), chain);
    chain->elements = g_list_prepend (chain->elements, element);
  } else {
    GST_INFO ("adding element \"%s\" to chain %p disabled",
        GST_ELEMENT_NAME (element), chain);
    chain->disabled = g_list_prepend (chain->disabled, element);
  }
  chain->num_elements++;

  /* notify the scheduler that something changed */
  GST_FLAG_SET (chain->sched, GST_BASIC_SCHEDULER_CHANGE);
}

static gboolean
gst_basic_scheduler_chain_enable_element (GstSchedulerChain * chain,
    GstElement * element)
{
  GST_INFO ("enabling element \"%s\" in chain %p",
      GST_ELEMENT_NAME (element), chain);

  /* remove from disabled list */
  chain->disabled = g_list_remove (chain->disabled, element);

  /* add to elements list */
  chain->elements = g_list_prepend (chain->elements, element);

  /* notify the scheduler that something changed */
  GST_FLAG_SET (chain->sched, GST_BASIC_SCHEDULER_CHANGE);
  /* GST_FLAG_UNSET(element, GST_ELEMENT_COTHREAD_STOPPING); */

  /* reschedule the chain */
  return gst_basic_scheduler_cothreaded_chain (GST_BIN (GST_SCHEDULER (chain->
              sched)->parent), chain);
}

static void
gst_basic_scheduler_chain_disable_element (GstSchedulerChain * chain,
    GstElement * element)
{
  GST_INFO ("disabling element \"%s\" in chain %p",
      GST_ELEMENT_NAME (element), chain);

  /* remove from elements list */
  chain->elements = g_list_remove (chain->elements, element);

  /* add to disabled list */
  chain->disabled = g_list_prepend (chain->disabled, element);

  /* notify the scheduler that something changed */
  GST_FLAG_SET (chain->sched, GST_BASIC_SCHEDULER_CHANGE);
  GST_FLAG_SET (element, GST_ELEMENT_COTHREAD_STOPPING);

  /* reschedule the chain */
/* FIXME this should be done only if manager state != NULL */
/*  gst_basic_scheduler_cothreaded_chain(GST_BIN(chain->sched->parent),chain); */
}

static void
gst_basic_scheduler_chain_remove_element (GstSchedulerChain * chain,
    GstElement * element)
{
  GST_INFO ("removing element \"%s\" from chain %p", GST_ELEMENT_NAME (element),
      chain);

  /* if it's active, deactivate it */
  if (g_list_find (chain->elements, element)) {
    gst_basic_scheduler_chain_disable_element (chain, element);
  }
  /* we have to check for a threadstate here because a queue doesn't have one */
  if (GST_ELEMENT_THREADSTATE (element)) {
    do_cothread_destroy (GST_ELEMENT_THREADSTATE (element));
    GST_ELEMENT_THREADSTATE (element) = NULL;
  }

  /* remove the element from the list of elements */
  chain->disabled = g_list_remove (chain->disabled, element);
  chain->num_elements--;

  /* notify the scheduler that something changed */
  GST_FLAG_SET (chain->sched, GST_BASIC_SCHEDULER_CHANGE);

  /* if there are no more elements in the chain, destroy the chain */
  if (chain->num_elements == 0)
    gst_basic_scheduler_chain_destroy (chain);

}

static void
gst_basic_scheduler_chain_elements (GstBasicScheduler * sched,
    GstElement * element1, GstElement * element2)
{
  GList *chains;
  GstSchedulerChain *chain;
  GstSchedulerChain *chain1 = NULL, *chain2 = NULL;
  GstElement *element;

  /* first find the chains that hold the two  */
  chains = sched->chains;
  while (chains) {
    chain = (GstSchedulerChain *) (chains->data);
    chains = g_list_next (chains);

    if (g_list_find (chain->disabled, element1))
      chain1 = chain;
    else if (g_list_find (chain->elements, element1))
      chain1 = chain;

    if (g_list_find (chain->disabled, element2))
      chain2 = chain;
    else if (g_list_find (chain->elements, element2))
      chain2 = chain;
  }

  /* first check to see if they're in the same chain, we're done if that's the case */
  if ((chain1 != NULL) && (chain1 == chain2)) {
    GST_INFO ("elements are already in the same chain");
    return;
  }

  /* now, if neither element has a chain, create one */
  if ((chain1 == NULL) && (chain2 == NULL)) {
    GST_INFO ("creating new chain to hold two new elements");
    chain = gst_basic_scheduler_chain_new (sched);
    gst_basic_scheduler_chain_add_element (chain, element1);
    gst_basic_scheduler_chain_add_element (chain, element2);
    /* FIXME chain changed here */
/*    gst_basic_scheduler_cothreaded_chain(chain->sched->parent,chain); */

    /* otherwise if both have chains already, join them */
  } else if ((chain1 != NULL) && (chain2 != NULL)) {
    GST_INFO ("merging chain %p into chain %p", chain2, chain1);
    /* take the contents of chain2 and merge them into chain1 */
    chain1->disabled =
        g_list_concat (chain1->disabled, g_list_copy (chain2->disabled));
    chain1->elements =
        g_list_concat (chain1->elements, g_list_copy (chain2->elements));
    chain1->num_elements += chain2->num_elements;
    gst_basic_scheduler_chain_destroy (chain2);
    if (sched->context)

      gst_basic_scheduler_cothreaded_chain (GST_BIN (GST_SCHEDULER (chain1->
                  sched)->parent), chain1);

    /* otherwise one has a chain already, the other doesn't */
  } else {
    /* pick out which one has the chain, and which doesn't */
    if (chain1 != NULL)
      chain = chain1, element = element2;
    else
      chain = chain2, element = element1;

    GST_INFO ("adding element to existing chain");
    gst_basic_scheduler_chain_add_element (chain, element);
    /* FIXME chain changed here */
/*    gst_basic_scheduler_cothreaded_chain(chain->sched->parent,chain); */
  }

}


/* find the chain within the scheduler that holds the element, if any */
static GstSchedulerChain *
gst_basic_scheduler_find_chain (GstBasicScheduler * sched, GstElement * element)
{
  GList *chains;
  GstSchedulerChain *chain;

  GST_INFO ("searching for element \"%s\" in chains",
      GST_ELEMENT_NAME (element));

  chains = sched->chains;
  while (chains) {
    chain = (GstSchedulerChain *) (chains->data);
    chains = g_list_next (chains);

    if (g_list_find (chain->elements, element))
      return chain;
    if (g_list_find (chain->disabled, element))
      return chain;
  }

  return NULL;
}

static void
gst_basic_scheduler_chain_recursive_add (GstSchedulerChain * chain,
    GstElement * element, gboolean remove)
{
  GList *pads;
  GstPad *pad;
  GstElement *peerelement;
  GstSchedulerChain *prevchain;

  /* check to see if it's in a chain already */
  prevchain = gst_basic_scheduler_find_chain (chain->sched, element);
  /* if it's already in another chain, either remove or punt */
  if (prevchain != NULL) {
    if (remove == TRUE)
      gst_basic_scheduler_chain_remove_element (prevchain, element);
    else
      return;
  }

  /* add it to this one */
  gst_basic_scheduler_chain_add_element (chain, element);

  GST_DEBUG ("recursing on element \"%s\"", GST_ELEMENT_NAME (element));
  /* now go through all the pads and see which peers can be added */
  pads = element->pads;
  while (pads) {
    pad = GST_PAD (pads->data);
    pads = g_list_next (pads);

    GST_DEBUG ("have pad %s:%s, checking for valid peer",
        GST_DEBUG_PAD_NAME (pad));
    /* if the peer exists and could be in the same chain */
    if (GST_PAD_PEER (pad)) {
      GST_DEBUG ("has peer %s:%s", GST_DEBUG_PAD_NAME (GST_PAD_PEER (pad)));
      peerelement = GST_PAD_PARENT (GST_PAD_PEER (pad));
      if (GST_ELEMENT_SCHEDULER (GST_PAD_PARENT (pad)) ==
          GST_ELEMENT_SCHEDULER (peerelement)) {
        GST_DEBUG ("peer \"%s\" is valid for same chain",
            GST_ELEMENT_NAME (peerelement));
        gst_basic_scheduler_chain_recursive_add (chain, peerelement, remove);
      }
    }
  }
}

/*
 * Entry points for this scheduler.
 */
static void
gst_basic_scheduler_setup (GstScheduler * sched)
{
  /* first create thread context */
  if (GST_BASIC_SCHEDULER (sched)->context == NULL) {
    GST_DEBUG ("initializing cothread context");
    GST_BASIC_SCHEDULER (sched)->context = do_cothread_context_init ();
  }
}

static void
gst_basic_scheduler_reset (GstScheduler * sched)
{
  cothread_context *ctx;
  GList *elements = GST_BASIC_SCHEDULER (sched)->elements;

  while (elements) {
    GstElement *element = GST_ELEMENT (elements->data);

    if (GST_ELEMENT_THREADSTATE (element)) {
      do_cothread_destroy (GST_ELEMENT_THREADSTATE (element));
      GST_ELEMENT_THREADSTATE (element) = NULL;
    }
    elements = g_list_next (elements);
  }

  ctx = GST_BASIC_SCHEDULER (sched)->context;

  do_cothread_context_destroy (ctx);

  GST_BASIC_SCHEDULER (sched)->context = NULL;
}

static void
gst_basic_scheduler_add_element (GstScheduler * sched, GstElement * element)
{
  GstSchedulerChain *chain;
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  GST_INFO ("adding element \"%s\" to scheduler", GST_ELEMENT_NAME (element));

  /* only deal with elements after this point, not bins */
  /* exception is made for Bin's that are schedulable, like the autoplugger */
  if (GST_IS_BIN (element)
      && !GST_FLAG_IS_SET (element, GST_BIN_SELF_SCHEDULABLE))
    return;

  /* first add it to the list of elements that are to be scheduled */
  bsched->elements = g_list_prepend (bsched->elements, element);
  bsched->num_elements++;

  /* create a chain to hold it, and add */
  chain = gst_basic_scheduler_chain_new (bsched);
  gst_basic_scheduler_chain_add_element (chain, element);
}

static void
gst_basic_scheduler_remove_element (GstScheduler * sched, GstElement * element)
{
  GstSchedulerChain *chain;
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  if (g_list_find (bsched->elements, element)) {
    GST_INFO ("removing element \"%s\" from scheduler",
        GST_ELEMENT_NAME (element));

    /* if we are removing the currently scheduled element */
    if (bsched->current == element) {
      GST_FLAG_SET (element, GST_ELEMENT_COTHREAD_STOPPING);
      bsched->current = NULL;
    }
    /* find what chain the element is in */
    chain = gst_basic_scheduler_find_chain (bsched, element);

    /* remove it from its chain */
    if (chain != NULL) {
      gst_basic_scheduler_chain_remove_element (chain, element);
    }

    /* remove it from the list of elements */
    bsched->elements = g_list_remove (bsched->elements, element);
    bsched->num_elements--;

    /* unset the scheduler pointer in the element */
  }
}

static GstElementStateReturn
gst_basic_scheduler_state_transition (GstScheduler * sched,
    GstElement * element, gint transition)
{
  GstSchedulerChain *chain;
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  /* check if our parent changed state */
  if (GST_SCHEDULER_PARENT (sched) == element) {
    GST_INFO ("parent \"%s\" changed state", GST_ELEMENT_NAME (element));
    if (transition == GST_STATE_PLAYING_TO_PAUSED) {
      GST_INFO ("setting scheduler state to stopped");
      GST_SCHEDULER_STATE (sched) = GST_SCHEDULER_STATE_STOPPED;
    } else if (transition == GST_STATE_PAUSED_TO_PLAYING) {
      GST_INFO ("setting scheduler state to running");
      GST_SCHEDULER_STATE (sched) = GST_SCHEDULER_STATE_RUNNING;
    } else {
      GST_INFO ("no interesting state change, doing nothing");
    }
  } else if (transition == GST_STATE_PLAYING_TO_PAUSED ||
      transition == GST_STATE_PAUSED_TO_PLAYING) {
    /* find the chain the element is in */
    chain = gst_basic_scheduler_find_chain (bsched, element);

    /* remove it from the chain */
    if (chain) {
      if (transition == GST_STATE_PLAYING_TO_PAUSED) {
        gst_basic_scheduler_chain_disable_element (chain, element);
      } else if (transition == GST_STATE_PAUSED_TO_PLAYING) {
        if (!gst_basic_scheduler_chain_enable_element (chain, element)) {
          GST_INFO ("could not enable element \"%s\"",
              GST_ELEMENT_NAME (element));
          return GST_STATE_FAILURE;
        }
      }
    } else {
      GST_INFO ("element \"%s\" not found in any chain, no state change",
          GST_ELEMENT_NAME (element));
    }
  }

  return GST_STATE_SUCCESS;
}

static gboolean
gst_basic_scheduler_yield (GstScheduler * sched, GstElement * element)
{
  if (GST_ELEMENT_IS_COTHREAD_STOPPING (element)) {

    do_switch_to_main (sched);

    /* no need to do a pre_run, the cothread is stopping */
  }
  return FALSE;
}

static gboolean
gst_basic_scheduler_interrupt (GstScheduler * sched, GstElement * element)
{

  GST_FLAG_SET (element, GST_ELEMENT_COTHREAD_STOPPING);
  do_switch_to_main (sched);

  return FALSE;
}

static void
gst_basic_scheduler_error (GstScheduler * sched, GstElement * element)
{
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  if (GST_ELEMENT_THREADSTATE (element)) {
    GstSchedulerChain *chain;

    chain = gst_basic_scheduler_find_chain (bsched, element);
    if (chain)
      gst_basic_scheduler_chain_disable_element (chain, element);

    GST_SCHEDULER_STATE (sched) = GST_SCHEDULER_STATE_ERROR;

    do_switch_to_main (sched);
  }
}

static void
gst_basic_scheduler_pad_link (GstScheduler * sched, GstPad * srcpad,
    GstPad * sinkpad)
{
  GstElement *srcelement, *sinkelement;
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  srcelement = GST_PAD_PARENT (srcpad);
  g_return_if_fail (srcelement != NULL);
  sinkelement = GST_PAD_PARENT (sinkpad);
  g_return_if_fail (sinkelement != NULL);

  GST_INFO ("have pad linked callback on %s:%s to %s:%s",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));
  GST_DEBUG ("srcpad sched is %p, sinkpad sched is %p",
      GST_ELEMENT_SCHEDULER (srcelement), GST_ELEMENT_SCHEDULER (sinkelement));

  gst_basic_scheduler_chain_elements (bsched, srcelement, sinkelement);
}

static void
gst_basic_scheduler_pad_unlink (GstScheduler * sched, GstPad * srcpad,
    GstPad * sinkpad)
{
  GstElement *element1, *element2;
  GstSchedulerChain *chain1, *chain2;
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  GST_INFO ("unlinking pads %s:%s and %s:%s",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  /* we need to have the parent elements of each pad */
  element1 = GST_ELEMENT (GST_PAD_PARENT (srcpad));
  element2 = GST_ELEMENT (GST_PAD_PARENT (sinkpad));

  /* first task is to remove the old chain they belonged to.
   * this can be accomplished by taking either of the elements,
   * since they are guaranteed to be in the same chain
   * FIXME is it potentially better to make an attempt at splitting cleaner??
   */
  chain1 = gst_basic_scheduler_find_chain (bsched, element1);
  chain2 = gst_basic_scheduler_find_chain (bsched, element2);

/* FIXME: The old code still works in most cases, but does not deal with
 * the problem of screwed up sched chains in some autoplugging cases.
 * The new code has an infinite recursion bug during pipeline shutdown,
 * which must be fixed before it can be enabled again.
 */
#if 1
  if (chain1 != chain2) {
    /* elements not in the same chain don't need to be separated */
    GST_INFO ("elements not in the same chain");
    return;
  }

  if (chain1) {
    GST_INFO ("destroying chain");
    gst_basic_scheduler_chain_destroy (chain1);

    /* now create a new chain to hold element1 and build it from scratch */
    chain1 = gst_basic_scheduler_chain_new (bsched);
    gst_basic_scheduler_chain_recursive_add (chain1, element1, FALSE);
  }

  /* check the other element to see if it landed in the newly created chain */
  if (gst_basic_scheduler_find_chain (bsched, element2) == NULL) {
    /* if not in chain, create chain and build from scratch */
    chain2 = gst_basic_scheduler_chain_new (bsched);
    gst_basic_scheduler_chain_recursive_add (chain2, element2, FALSE);
  }
#else

  /* if they're both in the same chain, move second set of elements to a new chain */
  if (chain1 && (chain1 == chain2)) {
    GST_INFO ("creating new chain for second element and peers");
    chain2 = gst_basic_scheduler_chain_new (bsched);
    gst_basic_scheduler_chain_recursive_add (chain2, element2, TRUE);
  }
#endif
}

static GstData *
gst_basic_scheduler_pad_select (GstScheduler * sched, GstPad ** selected,
    GstPad ** padlist)
{
  GstData *data = NULL;
  gint i = 0;

  GST_INFO ("performing select");

  while (padlist[i]) {
    GstPad *pad = padlist[i];

    GST_RPAD_CHAINHANDLER (pad) =
        GST_DEBUG_FUNCPTR (gst_basic_scheduler_select_proxy);
  }

  do_element_switch (GST_PAD_PARENT (GST_PAD_PEER (padlist[0])));

  i = 0;
  while (padlist[i]) {
    GstPad *pad = padlist[i];

    if (GST_RPAD_BUFPEN (pad)) {
      *selected = pad;
      data = GST_RPAD_BUFPEN (pad);
      GST_RPAD_BUFPEN (pad) = NULL;
    }

    GST_RPAD_CHAINHANDLER (pad) =
        GST_DEBUG_FUNCPTR (gst_basic_scheduler_chainhandler_proxy);
  }

  g_assert (data != NULL);
  return data;
}

static GstSchedulerState
gst_basic_scheduler_iterate (GstScheduler * sched)
{
  GList *chains;
  GstSchedulerChain *chain;
  GstElement *entry;
  GList *elements;
  gint scheduled = 0;
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  GST_CAT_LOG_OBJECT (debug_dataflow, sched,
      "starting iteration in bin %s", GST_ELEMENT_NAME (sched->parent));

  /* clear the changes flag */
  GST_FLAG_UNSET (bsched, GST_BASIC_SCHEDULER_CHANGE);

  /* step through all the chains */
  chains = bsched->chains;

  if (chains == NULL)
    return GST_SCHEDULER_STATE_STOPPED;

  while (chains) {
    chain = (GstSchedulerChain *) (chains->data);
    chains = g_list_next (chains);

    /* all we really have to do is switch to the first child            */
    /* FIXME this should be lots more intelligent about where to start  */
    GST_CAT_DEBUG (debug_dataflow,
        "starting iteration via cothreads using %s scheduler", _SCHEDULER_NAME);

    if (chain->elements) {
      entry = NULL;             /*MattH ADDED? */
      GST_DEBUG ("there are %d elements in this chain", chain->num_elements);
      elements = chain->elements;
      while (elements) {
        entry = GST_ELEMENT (elements->data);
        elements = g_list_next (elements);
        if (GST_FLAG_IS_SET (entry, GST_ELEMENT_DECOUPLED)) {
          GST_DEBUG ("entry \"%s\" is DECOUPLED, skipping",
              GST_ELEMENT_NAME (entry));
          entry = NULL;
        } else if (GST_FLAG_IS_SET (entry, GST_ELEMENT_INFINITE_LOOP)) {
          GST_DEBUG ("entry \"%s\" is not valid, skipping",
              GST_ELEMENT_NAME (entry));
          entry = NULL;
        } else
          break;
      }
      if (entry) {
        GstSchedulerState state;

        GST_FLAG_SET (entry, GST_ELEMENT_COTHREAD_STOPPING);

        GST_CAT_DEBUG (debug_dataflow,
            "set COTHREAD_STOPPING flag on \"%s\"(@%p)",
            GST_ELEMENT_NAME (entry), entry);
        if (GST_ELEMENT_THREADSTATE (entry)) {

          do_switch_from_main (entry);

          state = GST_SCHEDULER_STATE (sched);
          /* if something changed, return - go on else */
          if (GST_FLAG_IS_SET (bsched, GST_BASIC_SCHEDULER_CHANGE) &&
              state != GST_SCHEDULER_STATE_ERROR)
            return GST_SCHEDULER_STATE_RUNNING;
        } else {
          GST_CAT_DEBUG (debug_dataflow,
              "cothread switch not possible, element has no threadstate");
          return GST_SCHEDULER_STATE_ERROR;
        }

        /* following is a check to see if the chain was interrupted due to a
         * top-half state_change().  (i.e., if there's a pending state.)
         *
         * if it was, return to gstthread.c::gst_thread_main_loop() to
         * execute the state change.
         */
        GST_CAT_DEBUG (debug_dataflow, "cothread switch ended or interrupted");

        if (state != GST_SCHEDULER_STATE_RUNNING) {
          GST_CAT_INFO (debug_dataflow, "scheduler is not running, in state %d",
              state);
          return state;
        }

        scheduled++;
      } else {
        GST_CAT_INFO (debug_dataflow,
            "no entry in this chain, trying the next one");
      }
    } else {
      GST_CAT_INFO (debug_dataflow,
          "no enabled elements in this chain, trying the next one");
    }
  }

  GST_CAT_LOG_OBJECT (debug_dataflow, sched, "leaving (%s)",
      GST_ELEMENT_NAME (sched->parent));
  if (scheduled == 0) {
    GST_CAT_INFO (debug_dataflow, "nothing was scheduled, return STOPPED");
    return GST_SCHEDULER_STATE_STOPPED;
  } else {
    GST_CAT_INFO (debug_dataflow, "scheduler still running, return RUNNING");
    return GST_SCHEDULER_STATE_RUNNING;
  }
}


static void
gst_basic_scheduler_show (GstScheduler * sched)
{
  GList *chains, *elements;
  GstElement *element;
  GstSchedulerChain *chain;
  GstBasicScheduler *bsched = GST_BASIC_SCHEDULER (sched);

  if (sched == NULL) {
    g_print ("scheduler doesn't exist for this element\n");
    return;
  }

  g_return_if_fail (GST_IS_SCHEDULER (sched));

  g_print ("SCHEDULER DUMP FOR MANAGING BIN \"%s\"\n",
      GST_ELEMENT_NAME (sched->parent));

  g_print ("scheduler has %d elements in it: ", bsched->num_elements);
  elements = bsched->elements;
  while (elements) {
    element = GST_ELEMENT (elements->data);
    elements = g_list_next (elements);

    g_print ("%s, ", GST_ELEMENT_NAME (element));
  }
  g_print ("\n");

  g_print ("scheduler has %d chains in it\n", bsched->num_chains);
  chains = bsched->chains;
  while (chains) {
    chain = (GstSchedulerChain *) (chains->data);
    chains = g_list_next (chains);

    g_print ("%p: ", chain);

    elements = chain->disabled;
    while (elements) {
      element = GST_ELEMENT (elements->data);
      elements = g_list_next (elements);

      g_print ("!%s, ", GST_ELEMENT_NAME (element));
    }

    elements = chain->elements;
    while (elements) {
      element = GST_ELEMENT (elements->data);
      elements = g_list_next (elements);

      g_print ("%s, ", GST_ELEMENT_NAME (element));
    }
    g_print ("\n");
  }
}