gstreamer/gst/autoplug/gstautoplugcache.c

/* GStreamer
 * Copyright (C) 2001 RidgeRun, Inc. (www.ridgerun.com)
 *
 * gstautoplugcache.c: Data cache for the dynamic autoplugger
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <gst/gst.h>

GstElementDetails gst_autoplugcache_details = {
  "AutoplugCache",
  "Connection",
  "Data cache for the dynamic autoplugger",
  VERSION,
  "Erik Walthinsen <omega@temple-baptist.com>",
  "(C) 2001 RidgeRun, Inc. (www.ridgerun.com)",
};

#define GST_TYPE_AUTOPLUGCACHE \
  (gst_autoplugcache_get_type())
#define GST_AUTOPLUGCACHE(obj) \
  (GTK_CHECK_CAST((obj),GST_TYPE_AUTOPLUGCACHE,GstAutoplugCache))
#define GST_AUTOPLUGCACHE_CLASS(klass) \
  (GTK_CHECK_CLASS_CAST((klass),GST_TYPE_AUTOPLUGCACHE,GstAutoplugCacheClass))
#define GST_IS_AUTOPLUGCACHE(obj) \
  (GTK_CHECK_TYPE((obj),GST_TYPE_AUTOPLUGCACHE))
#define GST_IS_AUTOPLUGCACHE_CLASS(obj) \
  (GTK_CHECK_CLASS_TYPE((klass),GST_TYPE_AUTOPLUGCACHE))

typedef struct _GstAutoplugCache GstAutoplugCache;
typedef struct _GstAutoplugCacheClass GstAutoplugCacheClass;

struct _GstAutoplugCache {
  GstElement element;

  GstPad *sinkpad, *srcpad;

  GList *cache;
  GList *cache_start;
  gint buffer_count;
  GList *current_playout;
  gboolean fire_empty;
};

struct _GstAutoplugCacheClass {
  GstElementClass parent_class;

  void		(*cache_empty)		(GstElement *element);
};


/* Cache signals and args */
enum {
  CACHE_EMPTY,
  LAST_SIGNAL
};

enum {
  ARG_0,
  ARG_BUFFER_COUNT,
  ARG_RESET
};


static void			gst_autoplugcache_class_init	(GstAutoplugCacheClass *klass);
static void			gst_autoplugcache_init		(GstAutoplugCache *queue);

static void			gst_autoplugcache_set_arg	(GtkObject *object, GtkArg *arg, guint id);
static void			gst_autoplugcache_get_arg	(GtkObject *object, GtkArg *arg, guint id);

static void			gst_autoplugcache_loop		(GstElement *element);

static GstElementStateReturn	gst_autoplugcache_change_state	(GstElement *element);


static GstElementClass *parent_class = NULL;
static guint gst_autoplugcache_signals[LAST_SIGNAL] = { 0 };

GtkType
gst_autoplugcache_get_type(void) {
  static GtkType autoplugcache_type = 0;

  if (!autoplugcache_type) {
    static const GtkTypeInfo autoplugcache_info = {
      "GstAutoplugCache",
      sizeof(GstAutoplugCache),
      sizeof(GstAutoplugCacheClass),
      (GtkClassInitFunc)gst_autoplugcache_class_init,
      (GtkObjectInitFunc)gst_autoplugcache_init,
      (GtkArgSetFunc)gst_autoplugcache_set_arg,
      (GtkArgGetFunc)gst_autoplugcache_get_arg,
      (GtkClassInitFunc)NULL,
    };
    autoplugcache_type = gtk_type_unique (GST_TYPE_ELEMENT, &autoplugcache_info);
  }
  return autoplugcache_type;
}

static void
gst_autoplugcache_class_init (GstAutoplugCacheClass *klass)
{
  GtkObjectClass *gtkobject_class;
  GstElementClass *gstelement_class;

  gtkobject_class = (GtkObjectClass*)klass;
  gstelement_class = (GstElementClass*)klass;

  parent_class = gtk_type_class (GST_TYPE_ELEMENT);

  gst_autoplugcache_signals[CACHE_EMPTY] =
    gtk_signal_new ("cache_empty", GTK_RUN_LAST, gtkobject_class->type,
                    GTK_SIGNAL_OFFSET (GstAutoplugCacheClass, cache_empty),
                    gtk_marshal_NONE__NONE, GTK_TYPE_NONE, 0);
  gtk_object_class_add_signals (gtkobject_class, gst_autoplugcache_signals, LAST_SIGNAL);

  gtk_object_add_arg_type ("GstAutoplugCache::buffer_count", GTK_TYPE_INT,
                           GTK_ARG_READABLE, ARG_BUFFER_COUNT);
  gtk_object_add_arg_type ("GstAutoplugCache::reset", GTK_TYPE_BOOL,
                           GTK_ARG_WRITABLE, ARG_RESET);

  gtkobject_class->set_arg = gst_autoplugcache_set_arg;
  gtkobject_class->get_arg = gst_autoplugcache_get_arg;

  gstelement_class->change_state = gst_autoplugcache_change_state;
}

static void
gst_autoplugcache_init (GstAutoplugCache *cache)
{
  gst_element_set_loop_function(GST_ELEMENT(cache), GST_DEBUG_FUNCPTR(gst_autoplugcache_loop));

  cache->sinkpad = gst_pad_new ("sink", GST_PAD_SINK);
  gst_element_add_pad (GST_ELEMENT(cache), cache->sinkpad);

  cache->srcpad = gst_pad_new ("src", GST_PAD_SRC);
  gst_element_add_pad (GST_ELEMENT(cache), cache->srcpad);

  // provide a zero basis for the cache
  cache->cache = g_list_prepend(NULL, NULL);
  cache->cache_start = cache->cache;
  cache->buffer_count = 0;
  cache->current_playout = 0;
  cache->fire_empty = FALSE;
}

static void
gst_autoplugcache_loop (GstElement *element)
{
  GstAutoplugCache *cache;
  GstBuffer *buf;

  cache = GST_AUTOPLUGCACHE (element);

  /* Theory:
   * The cache is a doubly-linked list.  The front of the list is the most recent
   * buffer, the end of the list is the first buffer.  The playout pointer always
   * points to the latest buffer sent out the end.  cache points to the front
   * (most reccent) of the list at all times.  cache_start points to the first 
   * buffer, i.e. the end of the list.
   * If the playout pointer does not have a prev (towards the most recent) buffer 
   * (== NULL), a buffer must be pulled from the sink pad and added to the cache.
   * When the playout pointer gets reset (as in a set_arg), the cache is walked
   * without problems, because the playout pointer has a non-NULL next.  When
   * the playout pointer hits the end of cache again it has to start pulling.
   */

  do {
    // the first time through, the current_playout pointer is going to be NULL
    if (cache->current_playout == NULL) {
      // get a buffer
      buf = gst_pad_pull (cache->sinkpad);

      // add it to the cache, though cache == NULL
      gst_buffer_ref (buf);
      cache->cache = g_list_prepend (cache->cache, buf);
      cache->buffer_count++;

      // set the current_playout pointer
      cache->current_playout = cache->cache;

      // send the buffer on its way
      gst_pad_push (cache->srcpad, buf);
    }

    // the steady state is where the playout is at the front of the cache
    else if (g_list_previous(cache->current_playout) == NULL) {

      // if we've been told to fire an empty signal (after a reset)
      if (cache->fire_empty) {
        fprintf(stderr,"at front of cache, about to pull, but firing signal\n");
        gtk_signal_emit (GTK_OBJECT(cache), gst_autoplugcache_signals[CACHE_EMPTY], NULL);
      }

      // get a buffer
      buf = gst_pad_pull (cache->sinkpad);

      // add it to the front of the cache
      gst_buffer_ref (buf);
      cache->cache = g_list_prepend (cache->cache, buf);
      cache->buffer_count++;

      // set the current_playout pointer
      cache->current_playout = cache->cache;

      // send the buffer on its way
      gst_pad_push (cache->srcpad, buf);
    }

    // otherwise we're trundling through existing cached buffers
    else {
      // move the current_playout pointer
      cache->current_playout = g_list_previous (cache->current_playout);

      // push that buffer
      gst_pad_push (cache->srcpad, GST_BUFFER(cache->current_playout->data));
    }
  } while (!GST_FLAG_IS_SET (element, GST_ELEMENT_COTHREAD_STOPPING));
}

static GstElementStateReturn
gst_autoplugcache_change_state (GstElement *element)
{
  GstAutoplugCache *cache;

  if (GST_ELEMENT_CLASS (parent_class)->change_state)
    return GST_ELEMENT_CLASS (parent_class)->change_state (element);

  return GST_STATE_SUCCESS;
}

static void
gst_autoplugcache_set_arg (GtkObject *object, GtkArg *arg, guint id)
{
  GstAutoplugCache *cache;

  cache = GST_AUTOPLUGCACHE (object);

  switch (id) {
    case ARG_RESET:
      // no idea why anyone would set this to FALSE, but just in case ;-)
      if (GTK_VALUE_BOOL(*arg)) {
        fprintf(stderr,"resetting playout pointer\n");
        // reset the playout pointer to the begining again
        cache->current_playout = cache->cache_start;
        // now we can fire a signal when the cache runs dry
        cache->fire_empty = TRUE;
      }
      break;
    default:
      break;
  }
}

static void
gst_autoplugcache_get_arg (GtkObject *object, GtkArg *arg, guint id)
{
  GstAutoplugCache *cache;

  cache = GST_AUTOPLUGCACHE (object);

  switch (id) {
    case ARG_BUFFER_COUNT:
      GTK_VALUE_INT(*arg) = cache->buffer_count;
      break;
    default:
      arg->type = GTK_TYPE_INVALID;
      break;
  }
}

static gboolean
plugin_init (GModule *module, GstPlugin *plugin)
{
  GstElementFactory *factory;

  factory = gst_elementfactory_new ("autoplugcache", GST_TYPE_AUTOPLUGCACHE,
                                    &gst_autoplugcache_details);
  g_return_val_if_fail (factory != NULL, FALSE);

  gst_plugin_add_factory (plugin, factory);

  return TRUE;
}

GstPluginDesc plugin_desc = {
  GST_VERSION_MAJOR,
  GST_VERSION_MINOR,
  "autoplugcache",
  plugin_init
};