Added Xid.from_string() constructor.

It exposes the parsing rules used in restore.

psycopg/xid_type.c

@@ -231,6 +231,20 @@ exit:
     return rv;
 }
 
+
+static const char xid_from_string_doc[] =
+    "Create a Xid object from a string representation.";
+
+static PyObject *
+xid_from_string_method(PyObject *cls, PyObject *args)
+{
+    PyObject *s = NULL;
+
+    if (!PyArg_ParseTuple(args, "O", &s)) { return NULL; }
+
+    return (PyObject *)xid_from_string(s);
+}
+
 static PySequenceMethods xid_sequence = {
     (lenfunc)xid_len,          /* sq_length */
     0,                         /* sq_concat */
@@ -244,6 +258,14 @@ static PySequenceMethods xid_sequence = {
     0,                         /* sq_inplace_repeat */
 };
 
+
+static struct PyMethodDef xid_methods[] = {
+    {"from_string", (PyCFunction)xid_from_string_method,
+     METH_VARARGS|METH_STATIC, xid_from_string_doc},
+    {NULL}
+};
+
+
 static const char xid_doc[] =
     "A transaction identifier used for two phase commit.";
 
@@ -288,7 +310,7 @@ PyTypeObject XidType = {
 
     /* Attribute descriptor and subclassing stuff */
 
-    0,          /*tp_methods*/
+    xid_methods, /*tp_methods*/
     xid_members, /*tp_members*/
     0,          /*tp_getset*/
     0,          /*tp_base*/
@@ -327,12 +349,8 @@ XidObject *xid_ensure(PyObject *oxid)
         Py_INCREF(oxid);
         rv = (XidObject *)oxid;
     }
-    else if (PyString_Check(oxid)) {
-        rv = xid_from_string(oxid);
-    }
     else {
-        PyErr_SetString(PyExc_TypeError,
+        rv = xid_from_string(oxid);
-            "not a valid transaction id");
     }
 
     return rv;
@@ -572,6 +590,11 @@ XidObject *
 xid_from_string(PyObject *str) {
     XidObject *rv;
 
+    if (!PyString_Check(str)) {
+        PyErr_SetString(PyExc_TypeError, "not a valid transaction id");
+        return NULL;
+    }
+
     /* Try to parse an XA triple from the string. This may fail for several
      * reasons, such as the rules stated in Xid.__init__. */
     rv = _xid_parse_string(str);

tests/test_connection.py

@@ -353,6 +353,36 @@ class ConnectionTwoPhaseTests(unittest.TestCase):
 
             cnn.tpc_rollback(xid)
 
+    def test_xid_construction(self):
+        from psycopg2.extensions import Xid
+
+        x1 = Xid(74, 'foo', 'bar')
+        self.assertEqual(74, x1.format_id)
+        self.assertEqual('foo', x1.gtrid)
+        self.assertEqual('bar', x1.bqual)
+
+    def test_xid_from_string(self):
+        from psycopg2.extensions import Xid
+
+        x2 = Xid.from_string('42_Z3RyaWQ=_YnF1YWw=')
+        self.assertEqual(42, x2.format_id)
+        self.assertEqual('gtrid', x2.gtrid)
+        self.assertEqual('bqual', x2.bqual)
+
+        x3 = Xid.from_string('99_xxx_yyy')
+        self.assertEqual(None, x3.format_id)
+        self.assertEqual('99_xxx_yyy', x3.gtrid)
+        self.assertEqual(None, x3.bqual)
+
+    def test_xid_to_string(self):
+        from psycopg2.extensions import Xid
+
+        x1 = Xid.from_string('42_Z3RyaWQ=_YnF1YWw=')
+        self.assertEqual(str(x1), '42_Z3RyaWQ=_YnF1YWw=')
+
+        x2 = Xid.from_string('99_xxx_yyy')
+        self.assertEqual(str(x2), '99_xxx_yyy')
+
 
 def test_suite():
     return unittest.TestLoader().loadTestsFromName(__name__)