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https://gitlab.freedesktop.org/gstreamer/gstreamer.git
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429 lines
15 KiB
C
429 lines
15 KiB
C
/* GStreamer
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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 <string.h>
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#include "example.h"
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/* The ElementDetails structure gives a human-readable description of the
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* plugin, as well as author and version data. Use the GST_ELEMENT_DETAILS
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* macro when defining it.
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*/
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static GstElementDetails example_details =
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GST_ELEMENT_DETAILS ("An example plugin",
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"Example/FirstExample",
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"Shows the basic structure of a plugin",
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"your name <your.name@your.isp>");
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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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{
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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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{
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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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GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("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_STATIC_CAPS ("unknown/unknown, " /* The MIME media type */
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"foo:int=1, " /* an integer property */
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"bar:boolean=true, " /* a boolean property */
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"baz:int={ 1, 3 }" /* a list of values */
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)
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);
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/* This factory is much simpler, and defines the source pad. */
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GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
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GST_PAD_SRC,
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GST_PAD_ALWAYS,
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GST_STATIC_CAPS ("unknown/unknown")
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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, GstData * _data);
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static void gst_example_set_property (GObject * object, guint prop_id,
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const GValue * value, GParamSpec * pspec);
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static void gst_example_get_property (GObject * object, guint prop_id,
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GValue * value, GParamSpec * pspec);
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static GstElementStateReturn gst_example_change_state (GstElement * element);
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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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GType
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gst_example_get_type (void)
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{
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static GType example_type = 0;
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if (!example_type) {
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static const GTypeInfo example_info = {
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sizeof (GstExampleClass),
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NULL,
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NULL,
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(GClassInitFunc) gst_example_class_init,
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NULL,
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NULL,
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sizeof (GstExample),
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0,
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(GInstanceInitFunc) gst_example_init,
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};
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example_type =
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g_type_register_static (GST_TYPE_ELEMENT, "GstExample", &example_info,
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0);
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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. GObject 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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GObjectClass *gobject_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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gobject_class = (GObjectClass *) 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 = g_type_class_ref (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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g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_ACTIVE, g_param_spec_int ("active", "active", "active", G_MININT, G_MAXINT, 0, G_PARAM_READWRITE)); /* CHECKME */
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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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g_signal_new ("asdf", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
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G_STRUCT_OFFSET (GstExampleClass, asdf), NULL, NULL,
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g_cclosure_marshal_VOID__POINTER, G_TYPE_NONE, 1, GST_TYPE_EXAMPLE);
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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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gobject_class->set_property = gst_example_set_property;
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gobject_class->get_property = gst_example_get_property;
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/* we also override the default state change handler with our own
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* implementation */
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gstelement_class->change_state = gst_example_change_state;
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/* We can now provide the details for this element, that we defined earlier. */
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gst_element_class_set_details (gstelement_class, &example_details);
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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 class.
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*/
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gst_element_class_add_pad_template (gstelement_class,
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gst_static_pad_template_get (&sink_template));
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gst_element_class_add_pad_template (gstelement_class,
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gst_static_pad_template_get (&src_template));
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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 template constructed by the factory.
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*/
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example->sinkpad =
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gst_pad_new_from_template (gst_static_pad_template_get (&sink_template),
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"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 =
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gst_pad_new_from_template (gst_static_pad_template_get (&src_template),
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"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, GstData * _data)
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{
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GstBuffer *buf = GST_BUFFER (_data);
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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),
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GST_BUFFER_SIZE (outbuf));
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/* we don't need the incomming buffer anymore so we unref it. When we are
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* the last plugin with a handle to the buffer, its memory will be freed */
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gst_buffer_unref (buf);
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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, GST_DATA (outbuf));
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/* For fun we'll emit our useless signal here */
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g_signal_emit (G_OBJECT (example), gst_example_signals[ASDF], 0, 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, GST_DATA (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_property (GObject * object, guint prop_id, const GValue * value,
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GParamSpec * pspec)
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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 (prop_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 = g_value_get_int (value);
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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_property (GObject * object, guint prop_id, GValue * value,
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GParamSpec * pspec)
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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 (prop_id) {
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case ARG_ACTIVE:
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g_value_set_int (value, example->active);
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break;
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default:
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G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
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break;
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}
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}
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/* This is the state change function that will be called when
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* the element goes through the different state changes.
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* The plugin can prepare itself and its internal data structures
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* in the various state transitions.
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*/
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static GstElementStateReturn
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gst_example_change_state (GstElement * element)
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{
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GstExample *example;
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/* cast to our plugin */
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example = GST_EXAMPLE (element);
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/* we perform our actions based on the state transition
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* of the element */
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switch (GST_STATE_TRANSITION (element)) {
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/* The NULL to READY transition is used to
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* create threads (if any) */
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case GST_STATE_NULL_TO_READY:
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break;
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/* In the READY to PAUSED state, the element should
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* open devices (if any) */
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case GST_STATE_READY_TO_PAUSED:
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break;
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/* In the PAUSED to PLAYING state, the element should
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* prepare itself for operation or continue after a PAUSE */
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case GST_STATE_PAUSED_TO_PLAYING:
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break;
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/* In the PLAYING to PAUSED state, the element should
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* PAUSE itself and make sure it can resume operation */
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case GST_STATE_PLAYING_TO_PAUSED:
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break;
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/* In the PAUSED to READY state, the element should reset
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* its internal state and close any devices. */
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case GST_STATE_PAUSED_TO_READY:
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break;
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/* The element should free all resources, terminate threads
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* and put itself into its initial state again */
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case GST_STATE_READY_TO_NULL:
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break;
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}
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/* Then we call the parent state change handler */
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return parent_class->change_state (element);
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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 (GstPlugin * plugin)
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{
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/* We need to register each element we provide with the plugin. This consists
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* of the name of the element, a rank that gives the importance of the element
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* when compared to similar plugins and the GType identifier.
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*/
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if (!gst_element_register (plugin, "example", GST_RANK_MARGINAL,
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GST_TYPE_EXAMPLE))
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return FALSE;
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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 your 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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GST_PLUGIN_DEFINE (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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"an example plugin", /* a short description of the plugin in English */
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plugin_init, /* Pointer to the initialisation function for the plugin. */
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"0.1", /* The version number of the plugin */
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"LGPL", /* ieffective license the plugin can be shipped with. Must be
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* valid for all libraries it links to, too. */
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"my nifty plugin package",
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/* package this plugin belongs to. */
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"http://www.mydomain.com"
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/* originating URL for this plugin. This is the place to look
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* for updates, information and so on. */
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);
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