gstreamer/gst/gstbus.c

/* GStreamer
 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
 *
 * gstbus.c: GstBus subsystem
 *
 * 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 <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>

#include "gst_private.h"
#include "gstinfo.h"

#include "gstbus.h"

enum
{
  ARG_0,
};

static void gst_bus_class_init (GstBusClass * klass);
static void gst_bus_init (GstBus * bus);
static void gst_bus_dispose (GObject * object);

static void gst_bus_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_bus_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);

static GstObjectClass *parent_class = NULL;

/* static guint gst_bus_signals[LAST_SIGNAL] = { 0 }; */

GType
gst_bus_get_type (void)
{
  static GType bus_type = 0;

  if (!bus_type) {
    static const GTypeInfo bus_info = {
      sizeof (GstBusClass),
      NULL,
      NULL,
      (GClassInitFunc) gst_bus_class_init,
      NULL,
      NULL,
      sizeof (GstBus),
      0,
      (GInstanceInitFunc) gst_bus_init,
      NULL
    };

    bus_type = g_type_register_static (GST_TYPE_OBJECT, "GstBus", &bus_info, 0);
  }
  return bus_type;
}

static void
gst_bus_class_init (GstBusClass * klass)
{
  GObjectClass *gobject_class;
  GstObjectClass *gstobject_class;

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

  parent_class = g_type_class_ref (GST_TYPE_OBJECT);

  if (!g_thread_supported ())
    g_thread_init (NULL);

  gobject_class->dispose = GST_DEBUG_FUNCPTR (gst_bus_dispose);
  gobject_class->set_property = GST_DEBUG_FUNCPTR (gst_bus_set_property);
  gobject_class->get_property = GST_DEBUG_FUNCPTR (gst_bus_get_property);
}

static void
gst_bus_init (GstBus * bus)
{
  bus->queue = g_queue_new ();
  bus->queue_lock = g_mutex_new ();

  if (socketpair (PF_UNIX, SOCK_STREAM, 0, bus->control_socket) < 0)
    goto no_socketpair;

  bus->io_channel = g_io_channel_unix_new (bus->control_socket[0]);

  return;

  /* errors */
no_socketpair:
  {
    g_warning ("cannot create io channel");
    bus->io_channel = NULL;
  }
}

static void
gst_bus_dispose (GObject * object)
{
  GstBus *bus;

  bus = GST_BUS (object);

  if (bus->io_channel) {
    g_io_channel_shutdown (bus->io_channel, TRUE, NULL);
    g_io_channel_unref (bus->io_channel);
    bus->io_channel = NULL;
  }
  close (bus->control_socket[0]);
  close (bus->control_socket[1]);

  if (bus->queue) {
    g_mutex_lock (bus->queue_lock);
    g_queue_free (bus->queue);
    bus->queue = NULL;
    g_mutex_unlock (bus->queue_lock);
    g_mutex_free (bus->queue_lock);
    bus->queue_lock = NULL;
  }

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

static void
gst_bus_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstBus *bus;

  bus = GST_BUS (object);

  switch (prop_id) {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_bus_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstBus *bus;

  bus = GST_BUS (object);

  switch (prop_id) {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

GstBus *
gst_bus_new (void)
{
  GstBus *result;

  result = g_object_new (gst_bus_get_type (), NULL);

  return result;
}

/**
 * gst_bus_post:
 * @bus: a #GstBus to post on
 * @message: The #GstMessage to post
 *
 * Post a message on the given bus.
 *
 * Returns: TRUE if the message could be posted.
 *
 * MT safe.
 */
gboolean
gst_bus_post (GstBus * bus, GstMessage * message)
{
  gchar c;
  GstBusSyncReply reply = GST_BUS_PASS;
  GstBusSyncHandler handler;
  gpointer handler_data;
  gboolean need_write = FALSE;
  ssize_t write_ret = -1;

  g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
  g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);

  //g_print ("posting message on bus, type %d\n", GST_MESSAGE_TYPE (message));
  GST_DEBUG_OBJECT (bus, "posting message on bus");

  GST_LOCK (bus);
  handler = bus->sync_handler;
  handler_data = bus->sync_handler_data;
  GST_UNLOCK (bus);

  /* first call the sync handler if it is installed */
  if (handler) {
    reply = handler (bus, message, handler_data);
  }

  /* now see what we should do with the message */
  switch (reply) {
    case GST_BUS_DROP:
      /* drop the message */
      break;
    case GST_BUS_PASS:
      /* pass the message to the async queue */
      g_mutex_lock (bus->queue_lock);
      if (g_queue_get_length (bus->queue) == 0)
        need_write = TRUE;
      g_queue_push_tail (bus->queue, message);
      g_mutex_unlock (bus->queue_lock);

      if (need_write) {
        c = 'p';
        errno = EAGAIN;
        while (write_ret == -1) {
          switch (errno) {
            case EAGAIN:
            case EINTR:
              break;
            default:
              perror ("gst_bus_post: could not write to fd");
              return FALSE;
          }
          write_ret = write (bus->control_socket[1], &c, 1);
        }
      }
      break;
    case GST_BUS_ASYNC:
    {
      /* async delivery, we need a mutex and a cond to block
       * on */
      GMutex *lock = g_mutex_new ();
      GCond *cond = g_cond_new ();

      GST_MESSAGE_COND (message) = cond;
      GST_MESSAGE_GET_LOCK (message) = lock;

      GST_DEBUG ("waiting for async delivery of message %p", message);

      /* now we lock the message mutex, send the message to the async
       * queue. When the message is handled by the app and destroyed, 
       * the cond will be signalled and we can continue */
      g_mutex_lock (lock);
      g_mutex_lock (bus->queue_lock);
      if (g_queue_get_length (bus->queue) == 0)
        need_write = TRUE;
      g_queue_push_tail (bus->queue, message);
      g_mutex_unlock (bus->queue_lock);

      if (need_write) {
        c = 'p';
        errno = EAGAIN;
        while (write_ret == -1) {
          switch (errno) {
            case EAGAIN:
            case EINTR:
              break;
            default:
              perror ("gst_bus_post: could not write to fd");
              return FALSE;
          }
          write_ret = write (bus->control_socket[1], &c, 1);
        }
      }

      /* now block till the message is freed */
      g_cond_wait (cond, lock);
      g_mutex_unlock (lock);

      GST_DEBUG ("message %p delivered asynchronously", message);

      g_mutex_free (lock);
      g_cond_free (cond);
      break;
    }
  }

  return TRUE;
}

/**
 * gst_bus_have_pending:
 * @bus: a #GstBus to check
 *
 * Check if there are pending messages on the bus that should be 
 * handled.
 *
 * Returns: TRUE if there are messages on the bus to be handled.
 *
 * MT safe.
 */
gboolean
gst_bus_have_pending (GstBus * bus)
{
  gint length;

  g_return_val_if_fail (GST_IS_BUS (bus), FALSE);

  g_mutex_lock (bus->queue_lock);
  length = g_queue_get_length (bus->queue);
  g_mutex_unlock (bus->queue_lock);

  return (length > 0);
}

/**
 * gst_bus_pop:
 * @bus: a #GstBus to pop
 *
 * Get a message from the bus.
 *
 * Returns: The #GstMessage that is on the bus, or NULL if the bus is empty.
 *
 * MT safe.
 */
GstMessage *
gst_bus_pop (GstBus * bus)
{
  GstMessage *message;
  gboolean needs_read = FALSE;

  g_return_val_if_fail (GST_IS_BUS (bus), NULL);

  g_mutex_lock (bus->queue_lock);
  message = g_queue_pop_head (bus->queue);
  if (message && g_queue_get_length (bus->queue) == 0)
    needs_read = TRUE;
  g_mutex_unlock (bus->queue_lock);

  if (needs_read) {
    gchar c;
    ssize_t read_ret = -1;

    /* the char in the fd is essentially just a way to wake us up. read it off so
       we're not woken up again. */
    errno = EAGAIN;
    while (read_ret == -1) {
      switch (errno) {
        case EAGAIN:
        case EINTR:
          break;
        default:
          perror ("gst_bus_pop: could not read from fd");
          return NULL;
      }
      read_ret = read (bus->control_socket[0], &c, 1);
    }
  }

  return message;
}

/**
 * gst_bus_peek:
 * @bus: a #GstBus
 *
 * Peek the message on the top of the bus' queue. The bus maintains ownership of
 * the message, and the message will remain on the bus' message queue.
 *
 * Returns: The #GstMessage that is on the bus, or NULL if the bus is empty.
 *
 * MT safe.
 */
GstMessage *
gst_bus_peek (GstBus * bus)
{
  GstMessage *message;

  g_return_val_if_fail (GST_IS_BUS (bus), NULL);

  g_mutex_lock (bus->queue_lock);
  message = g_queue_peek_head (bus->queue);
  g_mutex_unlock (bus->queue_lock);

  return message;
}

/**
 * gst_bus_set_sync_handler:
 * @bus: a #GstBus to install the handler on
 * @func: The handler function to install
 * @data: User data that will be sent to the handler function.
 *
 * Install a synchronous handler on the bus. The function will be called
 * every time a new message is posted on the bus. Note that the function
 * will be called in the same thread context as the posting object.
 */
void
gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
{
  g_return_if_fail (GST_IS_BUS (bus));

  GST_LOCK (bus);
  bus->sync_handler = func;
  bus->sync_handler_data = data;
  GST_UNLOCK (bus);
}

/**
 * gst_bus_create_watch:
 * @bus: a #GstBus to create the watch for
 *
 * Create watch for this bus. 
 *
 * Returns: A #GSource that can be added to a mainloop.
 */
GSource *
gst_bus_create_watch (GstBus * bus)
{
  GSource *source;

  g_return_val_if_fail (GST_IS_BUS (bus), NULL);

  /* FIXME, we need to ref the bus and unref it when the source
   * is destroyed */
  source = g_io_create_watch (bus->io_channel, G_IO_IN);

  return source;
}

typedef struct
{
  GSource *source;
  GstBus *bus;
  gint priority;
  GstBusHandler handler;
  gpointer user_data;
  GDestroyNotify notify;
} GstBusWatch;

static gboolean
bus_watch_callback (GIOChannel * channel, GIOCondition cond,
    GstBusWatch * watch)
{
  GstMessage *message;
  gboolean needs_pop = TRUE;

  g_return_val_if_fail (GST_IS_BUS (watch->bus), FALSE);

  message = gst_bus_peek (watch->bus);

  g_return_val_if_fail (message != NULL, TRUE);

  if (watch->handler)
    needs_pop = watch->handler (watch->bus, message, watch->user_data);

  if (needs_pop)
    gst_message_unref (gst_bus_pop (watch->bus));

  return TRUE;
}

static void
bus_watch_destroy (GstBusWatch * watch)
{
  if (watch->notify) {
    watch->notify (watch->user_data);
  }
  gst_object_unref (GST_OBJECT_CAST (watch->bus));
  g_free (watch);
}

/**
 * gst_bus_add_watch_full:
 * @bus: a #GstBus to create the watch for.
 * @priority: The priority of the watch.
 * @handler: A function to call when a message is received.
 * @user_data: user data passed to @handler.
 * @notify: the function to call when the source is removed.
 *
 * Adds the bus to the mainloop with the given priority. If the handler returns
 * TRUE, the message will then be popped off the queue. When the handler is
 * called, the message belongs to the caller; if you want to keep a copy of it,
 * call gst_message_ref before leaving the handler.
 *
 * Returns: The event source id.
 *
 * MT safe.
 */
guint
gst_bus_add_watch_full (GstBus * bus, gint priority,
    GstBusHandler handler, gpointer user_data, GDestroyNotify notify)
{
  guint id;
  GstBusWatch *watch;

  g_return_val_if_fail (GST_IS_BUS (bus), 0);

  watch = g_new (GstBusWatch, 1);

  gst_object_ref (GST_OBJECT_CAST (bus));
  watch->source = gst_bus_create_watch (bus);
  watch->bus = bus;
  watch->priority = priority;
  watch->handler = handler;
  watch->user_data = user_data;
  watch->notify = notify;

  if (priority != G_PRIORITY_DEFAULT)
    g_source_set_priority (watch->source, priority);

  g_source_set_callback (watch->source, (GSourceFunc) bus_watch_callback,
      watch, (GDestroyNotify) bus_watch_destroy);

  id = g_source_attach (watch->source, NULL);
  g_source_unref (watch->source);

  return id;
}

/**
 * gst_bus_add_watch:
 * @bus: a #GstBus to create the watch for
 * @handler: A function to call when a message is received.
 * @user_data: user data passed to @handler.
 *
 * Adds the bus to the mainloop with the default priority.
 *
 * Returns: The event source id.
 *
 * MT safe.
 */
guint
gst_bus_add_watch (GstBus * bus, GstBusHandler handler, gpointer user_data)
{
  return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, handler, user_data,
      NULL);
}

typedef struct
{
  GMainLoop *loop;
  guint timeout_id;
  GstMessageType events;
  GstMessageType revent;
} GstBusPollData;

static gboolean
poll_handler (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
{
  if (GST_MESSAGE_TYPE (message) & poll_data->events) {
    poll_data->revent = GST_MESSAGE_TYPE (message);
    if (g_main_loop_is_running (poll_data->loop))
      g_main_loop_quit (poll_data->loop);
    /* keep the message on the queue */
    return FALSE;
  } else {
    /* pop and unref the message */
    return TRUE;
  }
}

static gboolean
poll_timeout (GstBusPollData * poll_data)
{
  poll_data->timeout_id = 0;
  g_main_loop_quit (poll_data->loop);
  /* returning FALSE will remove the source id */
  return FALSE;
}

/**
 * gst_bus_poll:
 * @bus: a #GstBus
 * @events: a mask of #GstMessageType, representing the set of message types to
 * poll for.
 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll indefinitely.
 *
 * Poll the bus for events. Will block while waiting for events to come. You can
 * specify a maximum time to poll with the @timeout parameter. If @timeout is
 * negative, this function will block indefinitely.
 *
 * Returns: The type of the message that was received, or GST_MESSAGE_UNKNOWN if
 * the poll timed out. The message will remain in the bus queue; you will need
 * to gst_bus_pop() it off before entering gst_bus_poll() again.
 */
GstMessageType
gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
{
  GstBusPollData *poll_data;
  GstMessageType ret;
  guint id;

  poll_data = g_new0 (GstBusPollData, 1);
  if (timeout >= 0)
    poll_data->timeout_id = g_timeout_add (timeout / GST_MSECOND,
        (GSourceFunc) poll_timeout, poll_data);
  poll_data->loop = g_main_loop_new (NULL, FALSE);
  poll_data->events = events;
  poll_data->revent = GST_MESSAGE_UNKNOWN;

  id = gst_bus_add_watch (bus, (GstBusHandler) poll_handler, poll_data);
  g_main_loop_run (poll_data->loop);
  g_source_remove (id);

  ret = poll_data->revent;

  if (poll_data->timeout_id)
    g_source_remove (poll_data->timeout_id);
  g_main_loop_unref (poll_data->loop);
  g_free (poll_data);

  return ret;
}