GFileDescriptorBased: New interface

New interface for file descriptor based io object. The interface
is only exported on unix based systems. See bug 604086.

gio/gfiledescriptorbased.c

@@ -0,0 +1,72 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright (C) 2010 Christian Kellner
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser 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.
+ *
+ * Author: Christian Kellner <gicmo@gnome.org>
+ */
+
+#include "config.h"
+#include "gfiledescriptorbased.h"
+#include "glibintl.h"
+
+#include "gioalias.h"
+
+/**
+ * SECTION:gfile_descriptor_based
+ * @short_description: Stream seeking interface
+ * @include: gio/gio.h
+ * @see_also: #GInputStream, #GOutputStream
+ *
+ * #GFileDescriptorBased is implemented by streams (implementations of
+ * #GInputStream or #GOutputStream) that are based on file descriptors.
+ *
+ * Since: 2.24
+ *
+ **/
+
+typedef GFileDescriptorBasedIface GFileDescriptorBasedInterface;
+G_DEFINE_INTERFACE (GFileDescriptorBased, g_file_descriptor_based, G_TYPE_OBJECT)
+
+static void
+g_file_descriptor_based_default_init (GFileDescriptorBasedInterface *iface)
+{
+}
+
+/**
+ * g_file_descriptor_based_get_fd:
+ * @fd_based: a #GFileDescriptorBased.
+ *
+ * Gets the underlying file descriptor.
+ *
+ * Returns: The file descriptor
+ *
+ * Since: 2.24
+ **/
+int
+g_file_descriptor_based_get_fd (GFileDescriptorBased *fd_based)
+{
+  GFileDescriptorBasedIface *iface;
+
+  g_return_val_if_fail (G_IS_FILE_DESCRIPTOR_BASED (fd_based), 0);
+
+  iface = G_FILE_DESCRIPTOR_BASED_GET_IFACE (fd_based);
+
+  return (* iface->get_fd) (fd_based);
+}
+
+