python: Implement new event API.

This implements set_event_callback and delete_event_callback so that
Python programs can use the new event mechanism.

3 files changed, 215 insertions, 0 deletions

diff --git a/python/guestfs-py-byhand.c b/python/guestfs-py-byhand.c
index f454a7e6..af9686fc 100644
--- 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 +55,170 @@ 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]);
+
   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)
+{
+  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);
+
+  py_r = PyEval_CallObject (py_callback, args);
+  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 = PyInt_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;
+}
diff --git a/python/guestfs-py.h b/python/guestfs-py.h
index 6b7e05f0..29e84ba3 100644
--- a/python/guestfs-py.h
+++ b/python/guestfs-py.h
@@ -63,5 +63,7 @@ put_handle (guestfs_h *g)
 
 extern PyObject *py_guestfs_create (PyObject *self, PyObject *args);
 extern PyObject *py_guestfs_close (PyObject *self, PyObject *args);
+extern PyObject *py_guestfs_set_event_callback (PyObject *self, PyObject *args);
+extern PyObject *py_guestfs_delete_event_callback (PyObject *self, PyObject *args);
 
 #endif /* guestfs_py_h */
diff --git a/python/t/400-events.py b/python/t/400-events.py
new file mode 100644
index 00000000..1c29b004
--- /dev/null
+++ b/python/t/400-events.py
@@ -0,0 +1,58 @@
+# libguestfs Python bindings
+# Copyright (C) 2011 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+import os
+import guestfs
+
+g = guestfs.GuestFS()
+
+def log_callback (ev,eh,buf,array):
+    if ev == guestfs.EVENT_APPLIANCE:
+        buf = buf.rstrip()
+
+    # Log what happened.
+    print ("python event logged: event=0x%x eh=%d buf='%s' array=%s" %
+           (ev, eh, buf, array))
+
+close_invoked = 0
+
+def close_callback (ev, eh, buf, array):
+    global close_invoked
+    close_invoked += 1
+    log_callback (ev, eh, buf, array)
+
+# Register an event callback for all log messages.
+events = guestfs.EVENT_APPLIANCE | guestfs.EVENT_LIBRARY | guestfs.EVENT_TRACE
+g.set_event_callback (log_callback, events)
+
+# Register a callback for the close event.
+g.set_event_callback (close_callback, guestfs.EVENT_CLOSE)
+
+# Now make sure we see some messages.
+g.set_trace (1)
+g.set_verbose (1)
+
+# Do some stuff.
+g.add_drive_ro ("/dev/null")
+g.set_autosync (1)
+
+# Close the handle.  The close callback should be invoked.
+if close_invoked != 0:
+    raise "Error: close_invoked should be 0"
+del g
+if close_invoked != 1:
+    raise "Error: close_invoked should be 1"