gstreamer/docs/manual/utility.xml

<chapter id="cha-utility">
  <title>Utility functions</title>
  <para> 
    while you can use the regular g_object_getv () function to
    query the value of an object property, <application>GStreamer</application>
    provides some easy wrappers for this common operation.
  </para>
  <para> 
    Instead of writing the following Gtk+ code to query the GTK_STRING value
    of an object:
  </para>
  <programlisting>
  GtkArg arg;
  guchar *value;

  arg.name = argname;
  g_object_getv (G_OBJECT (object), 1, &amp;arg);
  value = GTK_VALUE_STRING (arg);
  </programlisting>
  <para> 
    You can also use:
  </para> 
  <programlisting>
  value = gst_util_get_string_arg (object, argname);
  </programlisting>
  <para> 
    These convenience functions exist for the following types:
    <itemizedlist>
      <listitem>
        <para>
         gint: with gst_util_get_int_arg ();
        </para>
      </listitem>
      <listitem>
        <para>
         gboolean: with gst_util_get_bool_arg ();
        </para>
      </listitem>
      <listitem>
        <para>
         glong: with gst_util_get_long_arg ();
        </para>
      </listitem>
      <listitem>
        <para>
         gfloat: with gst_util_get_float_arg ();
        </para>
      </listitem>
      <listitem>
        <para>
         gdouble: with gst_util_get_double_arg ();
        </para>
      </listitem>
      <listitem>
        <para>
         guchar*: with gst_util_get_string_arg ();
        </para>
      </listitem>
      <listitem>
        <para>
         gpointer: with gst_util_get_pointer_arg ();
        </para>
      </listitem>
    </itemizedlist>
  </para> 
  <para> 
    One usually sets object properties using g_object_set (). The problem with this
    method is that you need to know the type of the property. A convenience function,
    gst_utils_set_object_arg () is therefore provided so that you can always set 
    the property with a string value. for example:
  </para>
  <programlisting>
  gst_util_set_object_arg (someobject, "int_property", "1000");
  </programlisting>
  <para>
    Will do The Right Thing(tm), converting the string to the type of the property when
    needed.
  </para>

  <para> 
    There is also another utility function that can be used to dump a block
    of memory on the console. This function is very usefull for plugin
    developers. The function will dump size bytes of the memory pointed
    to by mem.
  </para> 
  <programlisting>
  void gst_util_dump_mem (guchar *mem, guint size);
  </programlisting>

</chapter>