Added connection.pgconn_ptr and cursor.pgresult_ptr

Allow interacting with libpq in Python via ctypes.

See #782.

psycopg/connection_type.c

@@ -1008,7 +1008,7 @@ psyco_conn_get_backend_pid(connectionObject *self, PyObject *dummy)
 
 /* get info about the connection */
 
-#define psyco_conn_info_get_doc \
+#define psyco_conn_info_doc \
 "info -- Get connection info."
 
 static PyObject *
@@ -1019,6 +1019,23 @@ psyco_conn_info_get(connectionObject *self)
 }
 
 
+/* return the pointer to the PGconn structure */
+
+#define psyco_conn_pgconn_ptr_doc \
+"pgconn_ptr -- Get the PGconn structure pointer."
+
+static PyObject *
+psyco_conn_pgconn_ptr_get(connectionObject *self)
+{
+    if (self->pgconn) {
+        return PyLong_FromVoidPtr((void *)self->pgconn);
+    }
+    else {
+        Py_RETURN_NONE;
+    }
+}
+
+
 /* reset the currect connection */
 
 #define psyco_conn_reset_doc \
@@ -1270,7 +1287,10 @@ static struct PyGetSetDef connectionObject_getsets[] = {
         psyco_conn_deferrable_doc },
     { "info",
         (getter)psyco_conn_info_get, NULL,
-        psyco_conn_info_get_doc },
+        psyco_conn_info_doc },
+    { "pgconn_ptr",
+        (getter)psyco_conn_pgconn_ptr_get, NULL,
+        psyco_conn_pgconn_ptr_doc },
     {NULL}
 };
 #undef EXCEPTION_GETTER

psycopg/cursor_type.c

@@ -107,6 +107,8 @@ psyco_curs_close(cursorObject *self, PyObject *dummy)
     }
 
 close:
+    CLEARPGRES(self->pgres);
+
     self->closed = 1;
     Dprintf("psyco_curs_close: cursor at %p closed", self);
 
@@ -1716,6 +1718,21 @@ psyco_curs_scrollable_set(cursorObject *self, PyObject *pyvalue)
 }
 
 
+#define psyco_curs_pgresult_ptr_doc \
+"pgresult_ptr -- Get the PGresult structure pointer."
+
+static PyObject *
+psyco_curs_pgresult_ptr_get(cursorObject *self)
+{
+    if (self->pgres) {
+        return PyLong_FromVoidPtr((void *)self->pgres);
+    }
+    else {
+        Py_RETURN_NONE;
+    }
+}
+
+
 /** the cursor object **/
 
 /* iterator protocol */
@@ -1842,6 +1859,9 @@ static struct PyGetSetDef cursorObject_getsets[] = {
       (getter)psyco_curs_scrollable_get,
       (setter)psyco_curs_scrollable_set,
       psyco_curs_scrollable_doc, NULL },
+    { "pgresult_ptr",
+      (getter)psyco_curs_pgresult_ptr_get, NULL,
+      psyco_curs_pgresult_ptr_doc, NULL },
     {NULL}
 };
 

tests/test_connection.py

@@ -26,6 +26,7 @@ import re
 import os
 import sys
 import time
+import ctypes
 import threading
 import subprocess as sp
 from operator import attrgetter
@@ -346,6 +347,20 @@ class ConnectionTests(ConnectingTestCase):
         # we can't do anything else in Python
         self.assertIsNotNone(capsule)
 
+    def test_pgconn_ptr(self):
+        conn = self.connect()
+        self.assert_(conn.pgconn_ptr is not None)
+
+        f = self.libpq.PQserverVersion
+        f.argtypes = [ctypes.c_void_p]
+        f.restype = ctypes.c_int
+        ver = f(conn.pgconn_ptr)
+        self.assertEqual(ver, conn.server_version)
+
+        conn.close()
+        self.assert_(conn.pgconn_ptr is None)
+
+
 class ParseDsnTestCase(ConnectingTestCase):
     def test_parse_dsn(self):
         from psycopg2 import ProgrammingError

tests/test_cursor.py

@@ -23,6 +23,7 @@
 # License for more details.
 
 import time
+import ctypes
 import pickle
 import psycopg2
 import psycopg2.extensions
@@ -650,6 +651,23 @@ class CursorTests(ConnectingTestCase):
             [(i,) for i in range(5)])
         self.assertEqual(cur.rowcount, 5)
 
+    @skip_before_postgres(9)
+    def test_pgresult_ptr(self):
+        curs = self.conn.cursor()
+        self.assert_(curs.pgresult_ptr is None)
+
+        f = self.libpq.PQcmdStatus
+        f.argtypes = [ctypes.c_void_p]
+        f.restype = ctypes.c_char_p
+
+        curs.execute("select 'x'")
+        self.assert_(curs.pgresult_ptr is not None)
+        status = f(curs.pgresult_ptr)
+        self.assertEqual(status, b'SELECT 1')
+
+        curs.close()
+        self.assert_(curs.pgresult_ptr is None)
+
 
 def test_suite():
     return unittest.TestLoader().loadTestsFromName(__name__)

tests/testutils.py

@@ -26,10 +26,12 @@ import re
 import os
 import sys
 import types
+import ctypes
 import select
 import platform
 import unittest
 from functools import wraps
+from ctypes.util import find_library
 from .testconfig import dsn, repl_dsn
 from psycopg2.compat import text_type
 
@@ -174,6 +176,18 @@ class ConnectingTestCase(unittest.TestCase):
             else:
                 raise Exception("Unexpected result from poll: %r", state)
 
+    _libpq = None
+
+    @property
+    def libpq(self):
+        """Return a ctypes wrapper for the libpq library"""
+        if ConnectingTestCase._libpq is not None:
+            return ConnectingTestCase._libpq
+
+        libname = find_library('pq')
+        rv = ConnectingTestCase._libpq = ctypes.pydll.LoadLibrary(libname)
+        return rv
+
 
 def decorate_all_tests(obj, *decorators):
     """