Python plugin loader implementation.

Fixes #304361.

Makefile.am

@@ -1,4 +1,4 @@
-SUBDIRS = common codegen gst examples testsuite pkgconfig
+SUBDIRS = common codegen gst examples plugin testsuite pkgconfig
 
 common_cflags = $(PYTHON_INCLUDES) $(PYGOBJECT_CFLAGS) $(GST_CFLAGS) $(GST_OPTION_CFLAGS) -fno-strict-aliasing
 common_libadd = $(GST_LIBS) $(GST_OPTION_LIBS)

acinclude.m4

@@ -64,3 +64,24 @@ $1],dnl
 $2])
 CPPFLAGS="$save_CPPFLAGS"
 ])
+
+dnl a macro to check for ability to embed python
+dnl  AM_CHECK_PYTHON_LIBS([ACTION-IF-POSSIBLE], [ACTION-IF-NOT-POSSIBLE])
+dnl function also defines PYTHON_LIBS
+AC_DEFUN([AM_CHECK_PYTHON_LIBS],
+[AC_REQUIRE([AM_CHECK_PYTHON_HEADERS])
+AC_MSG_CHECKING(for libraries required to embed python)
+dnl deduce PYTHON_LIBS
+py_exec_prefix=`$PYTHON -c "import sys; print sys.exec_prefix"`
+PYTHON_LIBS="-L${py_prefix}/lib -lpython${PYTHON_VERSION}"
+PYTHON_LIB_LOC="${py_prefix}/lib" 
+AC_SUBST(PYTHON_LIBS)
+AC_SUBST(PYTHON_LIB_LOC)
+dnl check if the headers exist:
+save_LIBS="$LIBS"
+LIBS="$LIBS $PYTHON_LIBS"
+AC_TRY_LINK_FUNC(Py_Initialize, dnl
+         [LIBS="$save_LIBS"; AC_MSG_RESULT(yes); $1], dnl
+         [LIBS="$save_LIBS"; AC_MSG_RESULT(no); $2])
+
+])

configure.ac

@@ -83,6 +83,7 @@ dnl check for GStreamer
 GST_MAJORMINOR=0.10
 AC_SUBST(GST_MAJORMINOR)
 PKG_CHECK_MODULES(GST, gstreamer-$GST_MAJORMINOR >= $GST_REQ)
+AC_DEFINE_UNQUOTED(GST_MAJORMINOR, "$GST_MAJORMINOR", [Gst MajorMinor version])
 AC_SUBST(GST_CFLAGS)
 AC_SUBST(GST_LIBS)
 
@@ -358,6 +359,13 @@ dnl add debugging options ...
 
 AG_GST_VALGRIND_CHECK
 
+dnl Stuff needed for the python plugin loader
+
+AM_CHECK_PYTHON_LIBS(,[AC_MSG_ERROR(could not find Python lib)])
+
+AG_GST_SET_PLUGINDIR
+
+
 AC_OUTPUT([
   Makefile
   codegen/Makefile
@@ -370,6 +378,7 @@ AC_OUTPUT([
   pkgconfig/Makefile
   pkgconfig/gst-python.pc
   pkgconfig/gst-python-uninstalled.pc
+  plugin/Makefile
   testsuite/Makefile
   win32/common/config.h
   gst-python.spec

plugin/Makefile.am

@@ -0,0 +1,12 @@
+plugin_LTLIBRARIES = libgstpython.la
+
+INCLUDES = $(PYGOBJECT_CFLAGS) $(GST_CFLAGS)\
+	-DPYTHON_VERSION=\"$(PYTHON_VERSION)\"		\
+	-DPY_LIB_LOC="\"$(PYTHON_LIB_LOC)\""		\
+	$(PYTHON_INCLUDES)
+
+libgstpython_la_SOURCES = gstpythonplugin.c
+#libgstpython_la_CFLAGS = $(PYGTK_CFLAGS) $(GST_CFLAGS)
+#libgstpython_la_LDFLAGS = $(GST_PLUGIN_LDFLAGS) -avoid-version -module # $(PYTHON_LIBS) -lpython2.4
+libgstpython_la_LDFLAGS = -module -avoid-version
+libgstpython_la_LIBADD = $(GST_LIBS) $(PYTHON_LIBS)

plugin/gstpythonplugin.c

@@ -0,0 +1,370 @@
+/* gst-python
+ * Copyright (C) 2009 Edward Hervey <bilboed@bilboed.com>
+ *               2005 Benjamin Otte <otte@gnome.org>
+ *
+ * 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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+/* include this first, before NO_IMPORT_PYGOBJECT is defined */
+#include <pygobject.h>
+#include <gst/gst.h>
+
+PyTypeObject *_PyGstElement_Type;
+#define PyGstElement_Type (*_PyGstElement_Type)
+
+
+GST_DEBUG_CATEGORY_STATIC (pyplugindebug);
+#define GST_CAT_DEFAULT pyplugindebug
+
+#define GST_ORIGIN "http://gstreamer.freedesktop.org"
+
+static PyObject *element;
+
+static inline gboolean
+np_init_pygobject (void)
+{
+  PyObject *gobject = PyImport_ImportModule ("gobject");
+  gboolean res = TRUE;
+
+  if (gobject != NULL) {
+    PyObject *mdict = PyModule_GetDict (gobject);
+    PyObject *cobject = PyDict_GetItemString (mdict, "_PyGObject_API");
+    if (PyCObject_Check (cobject)) {
+      _PyGObject_API =
+          (struct _PyGObject_Functions *) PyCObject_AsVoidPtr (cobject);
+    } else {
+      PyErr_SetString (PyExc_RuntimeError,
+          "could not find _PyGObject_API object");
+      PyErr_Print ();
+      res = FALSE;
+      goto beach;
+    }
+    if (!(PyObject_CallMethod (gobject, "threads_init", NULL, NULL))) {
+      PyErr_SetString (PyExc_RuntimeError, "Could not initialize threads");
+      PyErr_Print ();
+      res = FALSE;
+      goto beach;
+    }
+  } else {
+    PyErr_Print ();
+    GST_WARNING ("could not import gobject");
+    res = FALSE;
+  }
+
+beach:
+  return res;
+}
+
+static gboolean
+gst_python_plugin_load_file (GstPlugin * plugin, const char *name)
+{
+  PyObject *main_module, *main_locals;
+  PyObject *elementfactory;
+  int pos = 0;
+  GType gtype;
+  PyObject *module;
+  const gchar *facname;
+  guint rank;
+  PyObject *class;
+
+  GST_DEBUG ("loading plugin %s", name);
+
+  main_module = PyImport_AddModule ("__main__");
+  if (main_module == NULL) {
+    GST_WARNING ("Could not get __main__, ignoring plugin %s", name);
+    PyErr_Print ();
+    PyErr_Clear ();
+    return FALSE;
+  }
+
+  main_locals = PyModule_GetDict (main_module);
+  module =
+      PyImport_ImportModuleEx ((char *) name, main_locals, main_locals, NULL);
+  if (!module) {
+    GST_DEBUG ("Could not load module, ignoring plugin %s", name);
+    PyErr_Print ();
+    PyErr_Clear ();
+    return FALSE;
+  }
+
+  /* Get __gstelementfactory__ from file */
+  elementfactory = PyObject_GetAttrString (module, "__gstelementfactory__");
+  if (!elementfactory) {
+    GST_DEBUG ("python file doesn't contain __gstelementfactory__");
+    PyErr_Clear ();
+    return FALSE;
+  }
+
+  /* parse tuple : name, rank, gst.ElementClass */
+  if (!PyArg_ParseTuple (elementfactory, "sIO", &facname, &rank, &class)) {
+    GST_WARNING ("__gstelementfactory__ isn't correctly formatted");
+    PyErr_Print ();
+    PyErr_Clear ();
+    Py_DECREF (elementfactory);
+    return FALSE;
+  }
+
+  if (!PyType_Check (class)
+      || !(PyObject_IsSubclass (class, (PyObject *) & PyGstElement_Type))) {
+    GST_WARNING ("the class provided isn't a subclass of gst.Element");
+    PyErr_Print ();
+    PyErr_Clear ();
+    Py_DECREF (elementfactory);
+    Py_DECREF (class);
+  }
+
+  GST_LOG ("Valid plugin");
+  Py_DECREF (elementfactory);
+
+  return gst_element_register (plugin, facname, rank,
+      pyg_type_from_object (class));
+}
+
+static gboolean
+gst_python_load_directory (GstPlugin * plugin, gchar * path)
+{
+  GST_LOG ("Checking for python plugins in %s", path);
+  GDir *dir;
+  const gchar *file;
+  GError *error = NULL;
+  gboolean ret = TRUE;
+
+  dir = g_dir_open (path, 0, &error);
+  if (!dir) {
+    /*retval should probably be depending on error, but since we ignore it... */
+    GST_WARNING ("Couldn't open Python plugin dir: %s", error->message);
+    g_error_free (error);
+    return FALSE;
+  }
+  while ((file = g_dir_read_name (dir))) {
+    /* FIXME : go down in subdirectories */
+    if (g_str_has_suffix (file, ".py")) {
+      gsize len = strlen (file) - 3;
+      gchar *name = g_strndup (file, len);
+      ret &= gst_python_plugin_load_file (plugin, name);
+      g_free (name);
+    }
+  }
+  return TRUE;
+}
+
+static gboolean
+gst_python_plugin_load (GstPlugin * plugin)
+{
+  PyObject *sys_path;
+  const gchar *plugin_path;
+  gboolean ret = TRUE;
+
+  sys_path = PySys_GetObject ("path");
+
+  /* Mimic the order in which the registry is checked in core */
+
+  /* 1. check env_variable GST_PLUGIN_PATH */
+  plugin_path = g_getenv ("GST_PLUGIN_PATH");
+  if (plugin_path) {
+    char **list;
+    int i;
+
+    GST_DEBUG ("GST_PLUGIN_PATH set to %s", plugin_path);
+    list = g_strsplit (plugin_path, G_SEARCHPATH_SEPARATOR_S, 0);
+    for (i = 0; list[i]; i++) {
+      gchar *sysdir = g_build_filename (list[i], "python", NULL);
+      PyList_Insert (sys_path, 0, PyString_FromString (sysdir));
+      gst_python_load_directory (plugin, sysdir);
+      g_free (sysdir);
+    }
+
+    g_strfreev (list);
+  }
+
+  /* 2. Check for GST_PLUGIN_SYSTEM_PATH */
+  plugin_path = g_getenv ("GST_PLUGIN_SYSTEM_PATH");
+  if (plugin_path == NULL) {
+    char *home_plugins;
+
+    /* 2.a. Scan user and system-wide plugin directory */
+    GST_DEBUG ("GST_PLUGIN_SYSTEM_PATH not set");
+
+    /* plugins in the user's home directory take precedence over
+     * system-installed ones */
+    home_plugins = g_build_filename (g_get_home_dir (),
+        ".gstreamer-" GST_MAJORMINOR, "plugins", "python", NULL);
+    PyList_Insert (sys_path, 0, PyString_FromString (home_plugins));
+    gst_python_load_directory (plugin, home_plugins);
+    g_free (home_plugins);
+
+    /* add the main (installed) library path */
+    PyList_Insert (sys_path, 0, PyString_FromString (PLUGINDIR "/python"));
+    gst_python_load_directory (plugin, PLUGINDIR "/python");
+  } else {
+    gchar **list;
+    gint i;
+
+    /* 2.b. Scan GST_PLUGIN_SYSTEM_PATH */
+    GST_DEBUG ("GST_PLUGIN_SYSTEM_PATH set to %s", plugin_path, plugin_path);
+    list = g_strsplit (plugin_path, G_SEARCHPATH_SEPARATOR_S, 0);
+    for (i = 0; list[i]; i++) {
+      gchar *sysdir;
+
+      sysdir = g_build_filename (list[i], "python", NULL);
+
+      PyList_Insert (sys_path, 0, PyString_FromString (sysdir));
+      gst_python_load_directory (plugin, sysdir);
+      g_free (sysdir);
+    }
+    g_strfreev (list);
+  }
+
+
+  return ret;
+}
+
+/** 
+ *pygst_require:
+ * @version: the version required
+ *
+ * Checks if the pygst/gst python modules are available.
+ * Requests the specified version.
+ *
+ * Returns: the gst-python module, or NULL if there was an error.
+ */
+
+static PyObject *
+pygst_require (gchar * version)
+{
+  PyObject *pygst, *gst;
+  PyObject *require;
+
+  if (!(pygst = PyImport_ImportModule ("pygst"))) {
+    GST_ERROR ("the pygst module is not available!");
+    goto error;
+  }
+
+  if (!(PyObject_CallMethod (pygst, "require", "s", version))) {
+    GST_ERROR ("the required version, %s, of gst-python is not available!");
+    Py_DECREF (pygst);
+    goto error;
+  }
+
+  if (!(gst = PyImport_ImportModule ("gst"))) {
+    GST_ERROR ("couldn't import the gst module");
+    Py_DECREF (pygst);
+    goto error;
+  }
+#define IMPORT(x, y) \
+    _PyGst##x##_Type = (PyTypeObject *)PyObject_GetAttrString(gst, y); \
+	if (_PyGst##x##_Type == NULL) { \
+		PyErr_Print(); \
+		return NULL; \
+	}
+  IMPORT (Element, "Element");
+
+  return gst;
+
+error:
+  {
+    PyErr_Print ();
+    PyErr_Clear ();
+    return NULL;
+  }
+}
+
+static gboolean
+plugin_init (GstPlugin * plugin)
+{
+  PyGILState_STATE state;
+  PyObject *gst, *dict, *pyplugin;
+  gboolean we_initialized = FALSE;
+  GModule *libpython;
+  gpointer has_python = NULL;
+
+  GST_DEBUG_CATEGORY_INIT (pyplugindebug, "pyplugin", 0,
+      "Python plugin loader");
+
+  gst_plugin_add_dependency_simple (plugin,
+      "HOME/.gstreamer-0.10/plugins/python:GST_PLUGIN_SYSTEM_PATH/python:GST_PLUGIN_PATH/python",
+      NULL, NULL, GST_PLUGIN_DEPENDENCY_FLAG_NONE);
+
+  GST_LOG ("Checking to see if libpython is already loaded");
+  g_module_symbol (g_module_open (NULL, G_MODULE_BIND_LOCAL), "Py_None",
+      &has_python);
+  if (has_python) {
+    GST_LOG ("libpython is already loaded");
+  } else {
+    GST_LOG ("loading libpython");
+    libpython =
+        g_module_open (PY_LIB_LOC "/libpython" PYTHON_VERSION "."
+        G_MODULE_SUFFIX, 0);
+    if (!libpython) {
+      GST_WARNING ("Couldn't g_module_open libpython. Reason: %s",
+          g_module_error ());
+      return FALSE;
+    }
+  }
+
+  if (!Py_IsInitialized ()) {
+    GST_LOG ("python wasn't initialized");
+    /* set the correct plugin for registering stuff */
+    Py_Initialize ();
+    we_initialized = TRUE;
+  } else {
+    GST_LOG ("python was already initialized");
+    state = pyg_gil_state_ensure ();
+  }
+
+  GST_LOG ("initializing pygobject");
+  if (!np_init_pygobject ()) {
+    GST_WARNING ("pygobject initialization failed");
+    return FALSE;
+  }
+
+  if (!(gst = pygst_require ("0.10"))) {
+    return FALSE;
+  }
+
+  if (we_initialized) {
+    pyplugin = pygobject_new (G_OBJECT (plugin));
+    if (!pyplugin || PyModule_AddObject (gst, "__plugin__", pyplugin) != 0) {
+      g_warning ("Couldn't set plugin");
+      Py_DECREF (pyplugin);
+    }
+  }
+
+  dict = PyModule_GetDict (gst);
+  if (!dict) {
+    GST_ERROR ("no dict?!");
+    return FALSE;
+  }
+
+  gst_python_plugin_load (plugin);
+
+  if (we_initialized) {
+    /* We need to release the GIL since we're going back to C land */
+    PyEval_SaveThread ();
+  } else
+    pyg_gil_state_release (state);
+  return TRUE;
+}
+
+GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
+    GST_VERSION_MINOR,
+    "python",
+    "loader for plugins written in python",
+    plugin_init, VERSION, "LGPL", PACKAGE_NAME, GST_ORIGIN)