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387 lines
13 KiB
C
387 lines
13 KiB
C
/* Gnome-Streamer
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* Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/* First, include the header file for the plugin, to bring in the
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* object definition and other useful things.
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*/
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#include "example.h"
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/* The ElementDetails structure gives a human-readable description
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* of the plugin, as well as author and version data.
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*/
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static GstElementDetails example_details = {
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"An example plugin",
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"Example/FirstExample",
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"Shows the basic structure of a plugin",
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VERSION,
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"your name <your.name@your.isp>",
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"(C) 2001",
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};
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/* These are the signals that this element can fire. They are zero-
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* based because the numbers themselves are private to the object.
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* LAST_SIGNAL is used for initialization of the signal array.
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*/
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enum {
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ASDF,
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/* FILL ME */
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LAST_SIGNAL
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};
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/* Arguments are identified the same way, but cannot be zero, so you
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* must leave the ARG_0 entry in as a placeholder.
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*/
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enum {
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ARG_0,
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ARG_ACTIVE,
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/* FILL ME */
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};
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/* The PadFactory structures describe what pads the element has or
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* can have. They can be quite complex, but for this example plugin
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* they are rather simple.
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*/
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static GstPadTemplate*
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sink_factory (void)
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{
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return
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gst_padtemplate_new (
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"sink", /* The name of the pad */
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GST_PAD_SINK, /* Direction of the pad */
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GST_PAD_ALWAYS, /* The pad exists for every instance */
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gst_caps_new (
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"example_sink", /* The name of the caps */
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"unknown/unknown", /* The overall MIME/type */
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gst_props_new (
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"foo", GST_PROPS_INT (1), /* An integer property */
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"bar", GST_PROPS_BOOLEAN (TRUE), /* A boolean */
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"baz", GST_PROPS_LIST ( /* A list of values for */
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GST_PROPS_INT (1),
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GST_PROPS_INT (3)
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),
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NULL)));
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}
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/* This factory is much simpler, and defines the source pad. */
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static GstPadTemplate*
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src_factory (void)
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{
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return
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gst_padtemplate_new (
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"src",
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GST_PAD_SRC,
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GST_PAD_ALWAYS,
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gst_caps_new (
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"example_src",
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"unknown/unknown",
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NULL));
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}
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/* A number of functon prototypes are given so we can refer to them later. */
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static void gst_example_class_init (GstExampleClass *klass);
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static void gst_example_init (GstExample *example);
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static void gst_example_chain (GstPad *pad, GstBuffer *buf);
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static void gst_example_set_arg (GtkObject *object,GtkArg *arg,guint id);
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static void gst_example_get_arg (GtkObject *object,GtkArg *arg,guint id);
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/* These hold the constructed pad templates, which are created during
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* plugin load, and used during element instantiation.
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*/
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static GstPadTemplate *src_template, *sink_template;
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/* The parent class pointer needs to be kept around for some object
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* operations.
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*/
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static GstElementClass *parent_class = NULL;
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/* This array holds the ids of the signals registered for this object.
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* The array indexes are based on the enum up above.
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*/
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static guint gst_example_signals[LAST_SIGNAL] = { 0 };
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/* This function is used to register and subsequently return the type
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* identifier for this object class. On first invocation, it will
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* register the type, providing the name of the class, struct sizes,
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* and pointers to the various functions that define the class.
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*/
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GtkType
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gst_example_get_type(void)
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{
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static GtkType example_type = 0;
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if (!example_type) {
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static const GtkTypeInfo example_info = {
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"GstExample",
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sizeof(GstExample),
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sizeof(GstExampleClass),
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(GtkClassInitFunc)gst_example_class_init,
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(GtkObjectInitFunc)gst_example_init,
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(GtkArgSetFunc)NULL, /* These last three are depracated */
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(GtkArgGetFunc)NULL,
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(GtkClassInitFunc)NULL,
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};
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example_type = gtk_type_unique(GST_TYPE_ELEMENT,&example_info);
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}
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return example_type;
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}
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/* In order to create an instance of an object, the class must be
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* initialized by this function. GtkObject will take care of running
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* it, based on the pointer to the function provided above.
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*/
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static void
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gst_example_class_init (GstExampleClass *klass)
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{
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/* Class pointers are needed to supply pointers to the private
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* implementations of parent class methods.
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*/
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GtkObjectClass *gtkobject_class;
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GstElementClass *gstelement_class;
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/* Since the example class contains the parent classes, you can simply
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* cast the pointer to get access to the parent classes.
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*/
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gtkobject_class = (GtkObjectClass*)klass;
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gstelement_class = (GstElementClass*)klass;
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/* The parent class is needed for class method overrides. */
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parent_class = gtk_type_class(GST_TYPE_ELEMENT);
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/* Here we add an argument to the object. This argument is an integer,
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* and can be both read and written.
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*/
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gtk_object_add_arg_type("GstExample::active", GTK_TYPE_INT,
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GTK_ARG_READWRITE, ARG_ACTIVE);
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/* Here we add a signal to the object. This is avery useless signal
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* called asdf. The signal will also pass a pointer to the listeners
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* which happens to be the example element itself */
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gst_example_signals[ASDF] =
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gtk_signal_new("asdf", GTK_RUN_LAST, gtkobject_class->type,
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GTK_SIGNAL_OFFSET (GstExampleClass, asdf),
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gtk_marshal_NONE__POINTER, GTK_TYPE_NONE, 1,
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GST_TYPE_EXAMPLE);
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gtk_object_class_add_signals (gtkobject_class, gst_example_signals,
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LAST_SIGNAL);
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/* The last thing is to provide the functions that implement get and set
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* of arguments.
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*/
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gtkobject_class->set_arg = gst_example_set_arg;
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gtkobject_class->get_arg = gst_example_get_arg;
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}
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/* This function is responsible for initializing a specific instance of
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* the plugin.
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*/
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static void
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gst_example_init(GstExample *example)
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{
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/* First we create the sink pad, which is the input to the element.
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* We will use the sink_template constructed in the plugin_init function
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* (below) to quickly generate the pad we need.
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*/
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example->sinkpad = gst_pad_new_from_template (sink_template, "sink");
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/* Setting the chain function allows us to supply the function that will
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* actually be performing the work. Without this, the element would do
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* nothing, with undefined results (assertion failures and such).
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*/
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gst_pad_set_chain_function(example->sinkpad,gst_example_chain);
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/* We then must add this pad to the element's list of pads. The base
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* element class manages the list of pads, and provides accessors to it.
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*/
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gst_element_add_pad(GST_ELEMENT(example),example->sinkpad);
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/* The src pad, the output of the element, is created and registered
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* in the same way, with the exception of the chain function. Source
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* pads don't have chain functions, because they can't accept buffers,
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* they only produce them.
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*/
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example->srcpad = gst_pad_new_from_template (src_template, "src");
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gst_element_add_pad(GST_ELEMENT(example),example->srcpad);
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/* Initialization of element's private variables. */
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example->active = FALSE;
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}
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/* The chain function is the heart of the element. It's where all the
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* work is done. It is passed a pointer to the pad in question, as well
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* as the buffer provided by the peer element.
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*/
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static void
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gst_example_chain (GstPad *pad, GstBuffer *buf)
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{
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GstExample *example;
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GstBuffer *outbuf;
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/* Some of these checks are of dubious value, since if there were not
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* already true, the chain function would never be called.
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*/
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g_return_if_fail(pad != NULL);
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g_return_if_fail(GST_IS_PAD(pad));
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g_return_if_fail(buf != NULL);
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/* We need to get a pointer to the element this pad belogs to. */
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example = GST_EXAMPLE(gst_pad_get_parent (pad));
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/* A few more sanity checks to make sure that the element that owns
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* this pad is the right kind of element, in case something got confused.
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*/
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g_return_if_fail(example != NULL);
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g_return_if_fail(GST_IS_EXAMPLE(example));
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/* If we are supposed to be doing something, here's where it happens. */
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if (example->active) {
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/* In this example we're going to copy the buffer to another one,
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* so we need to allocate a new buffer first. */
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outbuf = gst_buffer_new();
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/* We need to copy the size and offset of the buffer at a minimum. */
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GST_BUFFER_SIZE (outbuf) = GST_BUFFER_SIZE (buf);
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GST_BUFFER_OFFSET (outbuf) = GST_BUFFER_OFFSET (buf);
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/* Then allocate the memory for the new buffer */
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GST_BUFFER_DATA (outbuf) = (guchar *)g_malloc (GST_BUFFER_SIZE (outbuf));
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/* Then copy the data in the incoming buffer into the new buffer. */
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memcpy (GST_BUFFER_DATA (outbuf), GST_BUFFER_DATA (buf), GST_BUFFER_SIZE (outbuf));
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/* When we're done with the buffer, we push it on to the next element
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* in the pipeline, through the element's source pad, which is stored
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* in the element's structure.
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*/
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gst_pad_push(example->srcpad,outbuf);
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/* For fun we'll emit our useless signal here */
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gtk_signal_emit (GTK_OBJECT (example), gst_example_signals[ASDF],
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example);
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/* If we're not doing something, just send the original incoming buffer. */
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} else {
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gst_pad_push(example->srcpad,buf);
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}
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}
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/* Arguments are part of the Gtk+ object system, and these functions
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* enable the element to respond to various arguments.
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*/
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static void
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gst_example_set_arg (GtkObject *object,GtkArg *arg,guint id)
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{
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GstExample *example;
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/* It's not null if we got it, but it might not be ours */
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g_return_if_fail(GST_IS_EXAMPLE(object));
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/* Get a pointer of the right type. */
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example = GST_EXAMPLE(object);
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/* Check the argument id to see which argument we're setting. */
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switch (id) {
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case ARG_ACTIVE:
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/* Here we simply copy the value of the argument to our private
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* storage. More complex operations can be done, but beware that
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* they may occur at any time, possibly even while your chain function
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* is running, if you are using threads.
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*/
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example->active = GTK_VALUE_INT(*arg);
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g_print("example: set active to %d\n",example->active);
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break;
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default:
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break;
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}
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}
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/* The set function is simply the inverse of the get fuction. */
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static void
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gst_example_get_arg (GtkObject *object,GtkArg *arg,guint id)
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{
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GstExample *example;
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/* It's not null if we got it, but it might not be ours */
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g_return_if_fail(GST_IS_EXAMPLE(object));
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example = GST_EXAMPLE(object);
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switch (id) {
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case ARG_ACTIVE:
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GTK_VALUE_INT(*arg) = example->active;
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break;
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default:
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arg->type = GTK_TYPE_INVALID;
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break;
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}
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}
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/* This is the entry into the plugin itself. When the plugin loads,
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* this function is called to register everything that the plugin provides.
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*/
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static gboolean
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plugin_init (GModule *module, GstPlugin *plugin)
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{
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GstElementFactory *factory;
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/* We need to create an ElementFactory for each element we provide.
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* This consists of the name of the element, the GtkType identifier,
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* and a pointer to the details structure at the top of the file.
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*/
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factory = gst_elementfactory_new("example", GST_TYPE_EXAMPLE, &example_details);
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g_return_val_if_fail(factory != NULL, FALSE);
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/* The pad templates can be easily generated from the factories above,
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* and then added to the list of padtemplates for the elementfactory.
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* Note that the generated padtemplates are stored in static global
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* variables, for the gst_example_init function to use later on.
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*/
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sink_template = sink_factory ();
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gst_elementfactory_add_padtemplate (factory, sink_template);
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src_template = src_factory ();
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gst_elementfactory_add_padtemplate (factory, src_template);
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/* The very last thing is to register the elementfactory with the plugin. */
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gst_plugin_add_factory (plugin, factory);
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/* Now we can return successfully. */
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return TRUE;
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/* At this point, the GStreamer core registers the plugin, its
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* elementfactories, padtemplates, etc., for use in you application.
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*/
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}
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/* This structure describes the plugin to the system for dynamically loading
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* plugins, so that the version number and name can be checked in a uniform
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* way.
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*
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* The symbol pointing to this structure is the only symbol looked up when
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* loading the plugin.
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*/
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GstPluginDesc plugin_desc = {
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GST_VERSION_MAJOR, /* The major version of the core that this was built with */
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GST_VERSION_MINOR, /* The minor version of the core that this was built with */
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"example", /* The name of the plugin. This must be unique: plugins with
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* the same name will be assumed to be identical, and only
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* one will be loaded. */
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plugin_init /* Pointer to the initialisation function for the plugin. */
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};
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