python: Make result objects more robust.

Results returned by the GPGME are fragile, i.e. they are only valid
until the next operation is performed in the context.

We cannot arbitrarily constrain the lifetime of Python objects, we
therefore create deep copies of the results.

* lang/python/gpgme.i (gpgme_tofu_info_t): Turn these into a list.
(gpgme_*_result_t): Create deep copies of these objects.
* lang/python/helpers.c (pygpgme_wrap_fragile_result): New function.
* lang/python/helpers.h (pygpgme_wrap_fragile_result): New prototype.
* lang/python/pyme/results.py: New file.

Signed-off-by: Justus Winter <justus@g10code.com>

lang/python/gpgme.i

@@ -283,10 +283,11 @@
 
 // Make types containing 'next' field to be lists
 %ignore next;
-%typemap(out) gpgme_sig_notation_t, gpgme_engine_info_t, gpgme_subkey_t, gpgme_key_sig_t,
-	gpgme_user_id_t, gpgme_invalid_key_t, gpgme_recipient_t, gpgme_new_signature_t,
-	gpgme_signature_t, gpgme_import_status_t, gpgme_conf_arg_t, gpgme_conf_opt_t,
-	gpgme_conf_comp_t {
+%typemap(out) gpgme_sig_notation_t, gpgme_engine_info_t, gpgme_subkey_t,
+   gpgme_key_sig_t, gpgme_user_id_t, gpgme_invalid_key_t,
+   gpgme_recipient_t, gpgme_new_signature_t, gpgme_signature_t,
+   gpgme_import_status_t, gpgme_conf_arg_t, gpgme_conf_opt_t,
+   gpgme_conf_comp_t, gpgme_tofu_info_t {
   int i;
   int size = 0;
   $1_ltype curr;
@@ -300,6 +301,75 @@
   }
 }
 
+
+
+/* Wrap the fragile result objects into robust Python ones.  */
+%typemap(out) gpgme_encrypt_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "EncryptResult");
+  Py_DECREF(fragile);
+}
+
+%typemap(out) gpgme_decrypt_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "DecryptResult");
+  Py_DECREF(fragile);
+}
+
+%typemap(out) gpgme_sign_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "SignResult");
+  Py_DECREF(fragile);
+}
+
+%typemap(out) gpgme_verify_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "VerifyResult");
+  Py_DECREF(fragile);
+}
+
+%typemap(out) gpgme_import_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "ImportResult");
+  Py_DECREF(fragile);
+}
+
+%typemap(out) gpgme_genkey_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "GenkeyResult");
+  Py_DECREF(fragile);
+}
+
+%typemap(out) gpgme_keylist_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "KeylistResult");
+  Py_DECREF(fragile);
+}
+
+%typemap(out) gpgme_vfs_mount_result_t {
+  PyObject *fragile;
+  fragile = SWIG_NewPointerObj(SWIG_as_voidptr($1), $1_descriptor,
+                               %newpointer_flags);
+  $result = pygpgme_wrap_fragile_result(fragile, "VFSMountResult");
+  Py_DECREF(fragile);
+}
+
+
+
 // Include mapper for edit callbacks
 %typemap(in) (gpgme_edit_cb_t fnc, void *fnc_value) {
   if (! PyTuple_Check($input))

lang/python/helpers.c

@@ -272,6 +272,38 @@ object_to_gpgme_data_t(PyObject *input, int argnum, gpgme_data_t *wrapper,
 
 
 
+PyObject *
+pygpgme_wrap_fragile_result(PyObject *fragile, const char *classname)
+{
+  static PyObject *results;
+  PyObject *class;
+  PyObject *replacement;
+
+  if (results == NULL)
+    {
+      PyObject *from_list = PyList_New(0);
+      if (from_list == NULL)
+        return NULL;
+
+      results = PyImport_ImportModuleLevel("results", PyEval_GetGlobals(),
+                                           PyEval_GetLocals(), from_list, 1);
+      Py_DECREF(from_list);
+
+      if (results == NULL)
+        return NULL;
+    }
+
+  class = PyMapping_GetItemString(PyModule_GetDict(results), classname);
+  if (class == NULL)
+    return NULL;
+
+  replacement = PyObject_CallFunctionObjArgs(class, fragile, NULL);
+  Py_DECREF(class);
+  return replacement;
+}
+
+
+
 /* Callback support.  */
 static gpgme_error_t pyPassphraseCb(void *hook,
 				    const char *uid_hint,

lang/python/helpers.h

@@ -34,6 +34,8 @@ PyObject *object_to_gpgme_data_t(PyObject *input, int argnum,
 				 gpgme_data_t *wrapper,
 				 PyObject **bytesio, Py_buffer *view);
 
+PyObject *pygpgme_wrap_fragile_result(PyObject *fragile, const char *classname);
+
 PyObject *pygpgme_raise_callback_exception(PyObject *self);
 
 PyObject *pygpgme_set_passphrase_cb(PyObject *self, PyObject *cb);

lang/python/pyme/results.py

@@ -0,0 +1,116 @@
+# Robust result objects
+#
+# Copyright (C) 2016 g10 Code GmbH
+#
+# This file is part of GPGME.
+#
+# GPGME 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 2.1 of the
+# License, or (at your option) any later version.
+#
+# GPGME 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 program; if not, see <http://www.gnu.org/licenses/>.
+
+"""Robust result objects
+
+Results returned by the underlying library are fragile, i.e. they are
+only valid until the next operation is performed in the context.
+
+We cannot arbitrarily constrain the lifetime of Python objects, we
+therefore create deep copies of the results.
+
+"""
+
+class Result(object):
+    """Result object
+
+    Describes the result of an operation.
+
+    """
+
+    """Convert to types"""
+    _type = {}
+
+    """Map functions over list attributes"""
+    _map = {}
+
+    """Automatically copy unless blacklisted"""
+    _blacklist = {
+        'acquire', 'append', 'disown', 'next', 'own', 'this', 'thisown',
+    }
+    def __init__(self, fragile):
+        for key, func in self._type.items():
+            setattr(self, key, func(getattr(fragile, key)))
+
+        for key, func in self._map.items():
+            setattr(self, key, list(map(func, getattr(fragile, key))))
+
+        for key, func in self._map.items():
+            setattr(self, key, list(map(func, getattr(fragile, key))))
+
+        for key in dir(fragile):
+            if key.startswith('_') or key in self._blacklist:
+                continue
+            if hasattr(self, key):
+                continue
+
+            setattr(self, key, getattr(fragile, key))
+
+    def __str__(self):
+        return '<{} {}>'.format(
+            self.__class__.__name__,
+            ', '.join('{}: {}'.format(k, getattr(self, k))
+                      for k in dir(self) if not k.startswith('_')))
+
+class InvalidKey(Result):
+    pass
+
+class EncryptResult(Result):
+    _map = dict(invalid_recipients=InvalidKey)
+
+class Recipient(Result):
+    pass
+
+class DecryptResult(Result):
+    _type = dict(wrong_key_usage=bool)
+    _map = dict(recipients=Recipient)
+
+class NewSignature(Result):
+    pass
+
+class SignResult(Result):
+    _map = dict(invalid_signers=InvalidKey, signatures=NewSignature)
+
+class Notation(Result):
+    pass
+
+class TofuInfo(Result):
+    pass
+
+class Signature(Result):
+    _type = dict(wrong_key_usage=bool, chain_model=bool)
+    _map = dict(notations=Notation, tofu=TofuInfo)
+
+class VerifyResult(Result):
+    _map = dict(signatures=Signature)
+
+class ImportStatus(Result):
+    pass
+
+class ImportResult(Result):
+    _map = dict(imports=ImportStatus)
+
+class GenkeyResult(Result):
+    _type = dict(primary=bool, sub=bool)
+
+class KeylistResult(Result):
+    _type = dict(truncated=bool)
+
+class VFSMountResult(Result):
+    pass