gstreamer/gst/gstmessage.c

/* GStreamer
 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
 *
 * gstmessage.c: GstMessage 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.
 */
/**
 * SECTION:gstmessage
 * @short_description: Lightweight objects to signal the application of pipeline events
 * @see_also: #GstBus,#GstMiniObject
 *
 * Messages are implemented as a subclass of #GstMiniObject with a generic 
 * #GstStructure as the content. This allows for writing custom messages without
 * requiring an API change while allowing a wide range of different types
 * of messages.
 *
 * Messages are posted by objects in the pipeline and are passed to the 
 * application using the #GstBus. 
 */

#include <string.h>             /* memcpy */

#include "gst_private.h"
#include "gsterror.h"
#include "gstinfo.h"
#include "gstmessage.h"
#include "gsttaglist.h"
#include "gstutils.h"


static void gst_message_init (GTypeInstance * instance, gpointer g_class);
static void gst_message_class_init (gpointer g_class, gpointer class_data);
static void gst_message_finalize (GstMessage * message);
static GstMessage *_gst_message_copy (GstMessage * message);


void
_gst_message_initialize (void)
{
  gpointer ptr;

  GST_CAT_INFO (GST_CAT_GST_INIT, "init messages");

  gst_message_get_type ();

  /* the GstMiniObject types need to be class_ref'd once before it can be
   * done from multiple threads;
   * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */
  ptr = g_type_class_ref (GST_TYPE_MESSAGE);
  g_type_class_unref (ptr);
}

GType
gst_message_get_type (void)
{
  static GType _gst_message_type;

  if (G_UNLIKELY (_gst_message_type == 0)) {
    static const GTypeInfo message_info = {
      sizeof (GstMessageClass),
      NULL,
      NULL,
      gst_message_class_init,
      NULL,
      NULL,
      sizeof (GstMessage),
      0,
      gst_message_init,
      NULL
    };

    _gst_message_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
        "GstMessage", &message_info, 0);
  }
  return _gst_message_type;
}

static void
gst_message_class_init (gpointer g_class, gpointer class_data)
{
  GstMessageClass *message_class = GST_MESSAGE_CLASS (g_class);

  message_class->mini_object_class.copy =
      (GstMiniObjectCopyFunction) _gst_message_copy;
  message_class->mini_object_class.finalize =
      (GstMiniObjectFinalizeFunction) gst_message_finalize;
}

static void
gst_message_init (GTypeInstance * instance, gpointer g_class)
{
  GstMessage *message = GST_MESSAGE (instance);

  GST_CAT_INFO (GST_CAT_MESSAGE, "new message %p", message);
  GST_MESSAGE_TIMESTAMP (message) = GST_CLOCK_TIME_NONE;
}

static void
gst_message_finalize (GstMessage * message)
{
  g_return_if_fail (message != NULL);

  GST_CAT_INFO (GST_CAT_MESSAGE, "finalize message %p", message);

  if (GST_MESSAGE_SRC (message)) {
    gst_object_unref (GST_MESSAGE_SRC (message));
    GST_MESSAGE_SRC (message) = NULL;
  }

  if (message->lock) {
    GST_MESSAGE_LOCK (message);
    GST_MESSAGE_SIGNAL (message);
    GST_MESSAGE_UNLOCK (message);
  }

  if (message->structure) {
    gst_structure_set_parent_refcount (message->structure, NULL);
    gst_structure_free (message->structure);
  }
}

static GstMessage *
_gst_message_copy (GstMessage * message)
{
  GstMessage *copy;

  GST_CAT_INFO (GST_CAT_MESSAGE, "copy message %p", message);

  copy = (GstMessage *) gst_mini_object_new (GST_TYPE_MESSAGE);

  /* FIXME, need to copy relevant data from the miniobject. */
  //memcpy (copy, message, sizeof (GstMessage));

  GST_MESSAGE_GET_LOCK (copy) = GST_MESSAGE_GET_LOCK (message);
  GST_MESSAGE_COND (copy) = GST_MESSAGE_COND (message);
  GST_MESSAGE_TYPE (copy) = GST_MESSAGE_TYPE (message);
  GST_MESSAGE_TIMESTAMP (copy) = GST_MESSAGE_TIMESTAMP (message);

  if (GST_MESSAGE_SRC (message)) {
    GST_MESSAGE_SRC (copy) = gst_object_ref (GST_MESSAGE_SRC (message));
  }

  if (message->structure) {
    copy->structure = gst_structure_copy (message->structure);
    gst_structure_set_parent_refcount (copy->structure,
        &message->mini_object.refcount);
  }

  return copy;
}

static GstMessage *
gst_message_new (GstMessageType type, GstObject * src)
{
  GstMessage *message;

  message = (GstMessage *) gst_mini_object_new (GST_TYPE_MESSAGE);

  GST_CAT_INFO (GST_CAT_MESSAGE, "creating new message %p %d", message, type);

  message->type = type;
  if (src) {
    message->src = gst_object_ref (src);
    GST_CAT_DEBUG_OBJECT (GST_CAT_MESSAGE, src, "message source");
  } else {
    message->src = NULL;
    GST_CAT_DEBUG (GST_CAT_MESSAGE, "NULL message source");
  }
  message->structure = NULL;

  return message;
}

/**
 * gst_message_new_eos:
 * @src: The object originating the message.
 *
 * Create a new eos message. This message is generated and posted in
 * the sink elements of a GstBin. The bin will only forward the EOS
 * message to the application if all sinks have posted an EOS message.
 *
 * Returns: The new eos message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_eos (GstObject * src)
{
  GstMessage *message;

  message = gst_message_new (GST_MESSAGE_EOS, src);

  return message;
}

/**
 * gst_message_new_error:
 * @src: The object originating the message.
 * @error: The GError for this message.
 * @debug: A debugging string for something or other.
 *
 * Create a new error message. The message will copy @error and
 * @debug. This message is posted by element when a fatal event
 * occured. The pipeline will probably (partially) stop. 
 *
 * Returns: The new error message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_error (GstObject * src, GError * error, gchar * debug)
{
  GstMessage *message;
  GstStructure *s;

  message = gst_message_new (GST_MESSAGE_ERROR, src);
  /* gst_structure_new takes copies of the types passed in */
  s = gst_structure_new ("GstMessageError", "gerror", GST_TYPE_G_ERROR, error,
      "debug", G_TYPE_STRING, debug, NULL);
  gst_structure_set_parent_refcount (s, &message->mini_object.refcount);
  message->structure = s;

  return message;
}

/**
 * gst_message_new_warning:
 * @src: The object originating the message.
 * @error: The GError for this message.
 * @debug: A debugging string for something or other.
 *
 * Create a new warning message. The message will make copies of @error and
 * @debug.
 *
 * Returns: The new warning message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_warning (GstObject * src, GError * error, gchar * debug)
{
  GstMessage *message;
  GstStructure *s;

  message = gst_message_new (GST_MESSAGE_WARNING, src);
  /* gst_structure_new takes copies of the types passed in */
  s = gst_structure_new ("GstMessageWarning", "gerror", GST_TYPE_G_ERROR, error,
      "debug", G_TYPE_STRING, debug, NULL);
  gst_structure_set_parent_refcount (s, &message->mini_object.refcount);
  message->structure = s;

  return message;
}

/**
 * gst_message_new_tag:
 * @src: The object originating the message.
 * @tag_list: The tag list for the message.
 *
 * Create a new tag message. The message will take ownership of the tag list.
 * The message is posted by elements that discovered a new taglist.
 *
 * Returns: The new tag message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_tag (GstObject * src, GstTagList * tag_list)
{
  GstMessage *message;

  g_return_val_if_fail (GST_IS_STRUCTURE (tag_list), NULL);

  message = gst_message_new (GST_MESSAGE_TAG, src);
  gst_structure_set_parent_refcount (tag_list, &message->mini_object.refcount);
  message->structure = tag_list;

  return message;
}

/**
 * gst_message_new_state_change:
 * @src: The object originating the message.
 * @old: The previous state.
 * @new: The new (current) state.
 *
 * Create a state change message. This message is posted whenever an element changed
 * its state.
 *
 * Returns: The new state change message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_state_changed (GstObject * src, GstState old, GstState new)
{
  GstMessage *message;
  GstStructure *s;

  message = gst_message_new (GST_MESSAGE_STATE_CHANGED, src);

  s = gst_structure_new ("GstMessageState", "old-state", G_TYPE_INT, (gint) old,
      "new-state", G_TYPE_INT, (gint) new, NULL);
  gst_structure_set_parent_refcount (s, &message->mini_object.refcount);
  message->structure = s;

  return message;
}

/**
 * gst_message_new_segment_start:
 * @src: The object originating the message.
 * @timestamp: The timestamp of the segment being played
 *
 * Create a new segment message. This message is posted by elements that
 * start playback of a segment as a result of a segment seek. This message
 * is not received by the application but is used for maintenance reasons in
 * container elements.
 *
 * Returns: The new segment start message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_segment_start (GstObject * src, GstClockTime timestamp)
{
  GstMessage *message;
  GstStructure *s;

  message = gst_message_new (GST_MESSAGE_SEGMENT_START, src);

  s = gst_structure_new ("GstMessageSegmentStart", "timestamp", G_TYPE_INT64,
      (gint64) timestamp, NULL);
  gst_structure_set_parent_refcount (s, &message->mini_object.refcount);
  message->structure = s;

  return message;
}

/**
 * gst_message_new_segment_done:
 * @src: The object originating the message.
 * @timestamp: The timestamp of the segment being played
 *
 * Create a new segment done message. This message is posted by elements that
 * finish playback of a segment as a result of a segment seek. This message
 * is received by the application after all elements that posted a segment_start
 * have posted the segment_done.
 *
 * Returns: The new segment done message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_segment_done (GstObject * src, GstClockTime timestamp)
{
  GstMessage *message;
  GstStructure *s;

  message = gst_message_new (GST_MESSAGE_SEGMENT_DONE, src);

  s = gst_structure_new ("GstMessageSegmentDone", "timestamp", G_TYPE_INT64,
      (gint64) timestamp, NULL);
  gst_structure_set_parent_refcount (s, &message->mini_object.refcount);
  message->structure = s;

  return message;
}

/**
 * gst_message_new_custom:
 * @type: The #GstMessageType to distinguish messages
 * @src: The object originating the message.
 * @structure: The structure for the message. The message will take ownership of
 * the structure.
 *
 * Create a new custom-typed message. This can be used for anything not
 * handled by other message-specific functions to pass a message to the
 * app. The structure field can be NULL.
 *
 * Returns: The new message.
 *
 * MT safe.
 */
GstMessage *
gst_message_new_custom (GstMessageType type, GstObject * src,
    GstStructure * structure)
{
  GstMessage *message;

  message = gst_message_new (type, src);
  if (structure) {
    gst_structure_set_parent_refcount (structure,
        &message->mini_object.refcount);
    message->structure = structure;
  }
  return message;
}

/**
 * gst_message_get_structure:
 * @message: The #GstMessage.
 *
 * Access the structure of the message.
 *
 * Returns: The structure of the message. The structure is still
 * owned by the message, which means that you should not free it and 
 * that the pointer becomes invalid when you free the message.
 *
 * MT safe.
 */
const GstStructure *
gst_message_get_structure (GstMessage * message)
{
  g_return_val_if_fail (GST_IS_MESSAGE (message), NULL);

  return message->structure;
}

/**
 * gst_message_parse_tag:
 * @message: A valid #GstMessage of type GST_MESSAGE_TAG.
 *
 * Extracts the tag list from the GstMessage. The tag list returned in the
 * output argument is a copy; the caller must free it when done.
 *
 * MT safe.
 */
void
gst_message_parse_tag (GstMessage * message, GstTagList ** tag_list)
{
  g_return_if_fail (GST_IS_MESSAGE (message));
  g_return_if_fail (GST_MESSAGE_TYPE (message) == GST_MESSAGE_TAG);

  *tag_list = (GstTagList *) gst_structure_copy (message->structure);
}

/**
 * gst_message_parse_state_changed:
 * @message: A valid #GstMessage of type GST_MESSAGE_STATE_CHANGED.
 *
 * Extracts the old and new states from the GstMessage.
 *
 * MT safe.
 */
void
gst_message_parse_state_changed (GstMessage * message, GstState * old,
    GstState * new)
{
  g_return_if_fail (GST_IS_MESSAGE (message));
  g_return_if_fail (GST_MESSAGE_TYPE (message) == GST_MESSAGE_STATE_CHANGED);

  if (!gst_structure_get_int (message->structure, "old-state", (gint *) old))
    g_assert_not_reached ();
  if (!gst_structure_get_int (message->structure, "new-state", (gint *) new))
    g_assert_not_reached ();
}

/**
 * gst_message_parse_error:
 * @message: A valid #GstMessage of type GST_MESSAGE_ERROR.
 *
 * Extracts the GError and debug string from the GstMessage. The values returned
 * in the output arguments are copies; the caller must free them when done.
 *
 * MT safe.
 */
void
gst_message_parse_error (GstMessage * message, GError ** gerror, gchar ** debug)
{
  const GValue *error_gvalue;
  GError *error_val;

  g_return_if_fail (GST_IS_MESSAGE (message));
  g_return_if_fail (GST_MESSAGE_TYPE (message) == GST_MESSAGE_ERROR);

  error_gvalue = gst_structure_get_value (message->structure, "gerror");
  g_return_if_fail (error_gvalue != NULL);
  g_return_if_fail (G_VALUE_TYPE (error_gvalue) == GST_TYPE_G_ERROR);

  error_val = (GError *) g_value_get_boxed (error_gvalue);
  if (error_val)
    *gerror = g_error_copy (error_val);
  else
    *gerror = NULL;
  *debug = g_strdup (gst_structure_get_string (message->structure, "debug"));
}

/**
 * gst_message_parse_warning:
 * @message: A valid #GstMessage of type GST_MESSAGE_WARNING.
 *
 * Extracts the GError and debug string from the GstMessage. The values returned
 * in the output arguments are copies; the caller must free them when done.
 *
 * MT safe.
 */
void
gst_message_parse_warning (GstMessage * message, GError ** gerror,
    gchar ** debug)
{
  const GValue *error_gvalue;
  GError *error_val;

  g_return_if_fail (GST_IS_MESSAGE (message));
  g_return_if_fail (GST_MESSAGE_TYPE (message) == GST_MESSAGE_WARNING);

  error_gvalue = gst_structure_get_value (message->structure, "gerror");
  g_return_if_fail (error_gvalue != NULL);
  g_return_if_fail (G_VALUE_TYPE (error_gvalue) == GST_TYPE_G_ERROR);

  error_val = (GError *) g_value_get_boxed (error_gvalue);
  if (error_val)
    *gerror = g_error_copy (error_val);
  else
    *gerror = NULL;

  *debug = g_strdup (gst_structure_get_string (message->structure, "debug"));
}

/**
 * gst_message_parse_segment_start:
 * @message: A valid #GstMessage of type GST_MESSAGE_SEGMENT_START.
 *
 * Extracts the timestamp from the segment start message.
 *
 * MT safe.
 */
void
gst_message_parse_segment_start (GstMessage * message, GstClockTime * timestamp)
{
  const GValue *time_gvalue;

  g_return_if_fail (GST_IS_MESSAGE (message));
  g_return_if_fail (GST_MESSAGE_TYPE (message) == GST_MESSAGE_SEGMENT_START);

  time_gvalue = gst_structure_get_value (message->structure, "timstamp");
  g_return_if_fail (time_gvalue != NULL);
  g_return_if_fail (G_VALUE_TYPE (time_gvalue) == G_TYPE_INT64);

  if (timestamp)
    *timestamp = (GstClockTime) g_value_get_int64 (time_gvalue);
}

/**
 * gst_message_parse_segment_done:
 * @message: A valid #GstMessage of type GST_MESSAGE_SEGMENT_DONE.
 *
 * Extracts the timestamp from the segment done message.
 *
 * MT safe.
 */
void
gst_message_parse_segment_done (GstMessage * message, GstClockTime * timestamp)
{
  const GValue *time_gvalue;

  g_return_if_fail (GST_IS_MESSAGE (message));
  g_return_if_fail (GST_MESSAGE_TYPE (message) == GST_MESSAGE_SEGMENT_DONE);

  time_gvalue = gst_structure_get_value (message->structure, "timstamp");
  g_return_if_fail (time_gvalue != NULL);
  g_return_if_fail (G_VALUE_TYPE (time_gvalue) == G_TYPE_INT64);

  if (timestamp)
    *timestamp = (GstClockTime) g_value_get_int64 (time_gvalue);
}