daemon: debug segv correct use of dereferencing NULL.

[libguestfs.git] / python / guestfs-py-byhand.c

diff --git a/python/guestfs-py-byhand.c b/python/guestfs-py-byhand.c
index f454a7e..53c2e98 100644 (file)
--- a/python/guestfs-py-byhand.c
+++ b/python/guestfs-py-byhand.c
@@ -29,6 +29,8 @@
 
 #include "guestfs-py.h"
 
+static PyObject **get_all_event_callbacks (guestfs_h *g, size_t *len_rtn);
+
 PyObject *
 py_guestfs_create (PyObject *self, PyObject *args)
 {
@@ -53,17 +55,179 @@ py_guestfs_close (PyObject *self, PyObject *args)
   PyThreadState *py_save = NULL;
   PyObject *py_g;
   guestfs_h *g;
+  size_t i, len;
+  PyObject **callbacks;
 
   if (!PyArg_ParseTuple (args, (char *) "O:guestfs_close", &py_g))
     return NULL;
   g = get_handle (py_g);
 
+  /* As in the OCaml bindings, there is a hard to solve case where the
+   * caller can delete a callback from within the callback, resulting
+   * in a double-free here.  XXX
+   */
+  callbacks = get_all_event_callbacks (g, &len);
+
   if (PyEval_ThreadsInitialized ())
     py_save = PyEval_SaveThread ();
   guestfs_close (g);
   if (PyEval_ThreadsInitialized ())
     PyEval_RestoreThread (py_save);
 
+  for (i = 0; i < len; ++i)
+    Py_XDECREF (callbacks[i]);
+  free (callbacks);
+
+  Py_INCREF (Py_None);
+  return Py_None;
+}
+
+/* http://docs.python.org/release/2.5.2/ext/callingPython.html */
+static void
+py_guestfs_event_callback_wrapper (guestfs_h *g,
+                                   void *callback,
+                                   uint64_t event,
+                                   int event_handle,
+                                   int flags,
+                                   const char *buf, size_t buf_len,
+                                   const uint64_t *array, size_t array_len)
+{
+  PyGILState_STATE py_save = PyGILState_UNLOCKED;
+  PyObject *py_callback = callback;
+  PyObject *py_array;
+  PyObject *args;
+  PyObject *a;
+  size_t i;
+  PyObject *py_r;
+
+  py_array = PyList_New (array_len);
+  for (i = 0; i < array_len; ++i) {
+    a = PyLong_FromLongLong (array[i]);
+    PyList_SET_ITEM (py_array, i, a);
+  }
+
+  /* XXX As with Perl we don't pass the guestfs_h handle here. */
+  args = Py_BuildValue ("(Kis#O)",
+                        (unsigned PY_LONG_LONG) event, event_handle,
+                        buf, buf_len, py_array);
+
+  if (PyEval_ThreadsInitialized ())
+    py_save = PyGILState_Ensure ();
+
+  py_r = PyEval_CallObject (py_callback, args);
+
+  if (PyEval_ThreadsInitialized ())
+    PyGILState_Release (py_save);
+
+  Py_DECREF (args);
+
+  if (py_r != NULL)
+    Py_DECREF (py_r);
+  else
+    /* Callback threw an exception: print it. */
+    PyErr_PrintEx (0);
+}
+
+PyObject *
+py_guestfs_set_event_callback (PyObject *self, PyObject *args)
+{
+  PyObject *py_g;
+  guestfs_h *g;
+  PyObject *py_callback;
+  unsigned PY_LONG_LONG events;
+  int eh;
+  PyObject *py_eh;
+  char key[64];
+
+  if (!PyArg_ParseTuple (args, (char *) "OOK:guestfs_set_event_callback",
+                         &py_g, &py_callback, &events))
+    return NULL;
+
+  if (!PyCallable_Check (py_callback)) {
+    PyErr_SetString (PyExc_TypeError,
+                     "callback parameter is not callable "
+                     "(eg. lambda or function)");
+    return NULL;
+  }
+
+  g = get_handle (py_g);
+
+  eh = guestfs_set_event_callback (g, py_guestfs_event_callback_wrapper,
+                                   events, 0, py_callback);
+  if (eh == -1) {
+    PyErr_SetString (PyExc_RuntimeError, guestfs_last_error (g));
+    return NULL;
+  }
+
+  /* Increase the refcount for this callback since we are storing it
+   * in the opaque C libguestfs handle.  We need to remember that we
+   * did this, so we can decrease the refcount for all undeleted
+   * callbacks left around at close time (see py_guestfs_close).
+   */
+  Py_XINCREF (py_callback);
+
+  snprintf (key, sizeof key, "_python_event_%d", eh);
+  guestfs_set_private (g, key, py_callback);
+
+  py_eh = PyLong_FromLong ((long) eh);
+  return py_eh;
+}
+
+PyObject *
+py_guestfs_delete_event_callback (PyObject *self, PyObject *args)
+{
+  PyObject *py_g;
+  guestfs_h *g;
+  int eh;
+  PyObject *py_callback;
+  char key[64];
+
+  if (!PyArg_ParseTuple (args, (char *) "Oi:guestfs_delete_event_callback",
+                         &py_g, &eh))
+    return NULL;
+  g = get_handle (py_g);
+
+  snprintf (key, sizeof key, "_python_event_%d", eh);
+  py_callback = guestfs_get_private (g, key);
+  if (py_callback) {
+    Py_XDECREF (py_callback);
+    guestfs_set_private (g, key, NULL);
+    guestfs_delete_event_callback (g, eh);
+  }
+
   Py_INCREF (Py_None);
   return Py_None;
 }
+
+static PyObject **
+get_all_event_callbacks (guestfs_h *g, size_t *len_rtn)
+{
+  PyObject **r;
+  size_t i;
+  const char *key;
+  PyObject *cb;
+
+  /* Count the length of the array that will be needed. */
+  *len_rtn = 0;
+  cb = guestfs_first_private (g, &key);
+  while (cb != NULL) {
+    if (strncmp (key, "_python_event_", strlen ("_python_event_")) == 0)
+      (*len_rtn)++;
+    cb = guestfs_next_private (g, &key);
+  }
+
+  /* Copy them into the return array. */
+  r = guestfs_safe_malloc (g, sizeof (PyObject *) * (*len_rtn));
+
+  i = 0;
+  cb = guestfs_first_private (g, &key);
+  while (cb != NULL) {
+    if (strncmp (key, "_python_event_", strlen ("_python_event_")) == 0) {
+      r[i] = cb;
+      i++;
+    }
+    cb = guestfs_next_private (g, &key);
+  }
+
+  return r;
+}