Move the code implementing isinstance() and issubclass() to new C

APIs, PyObject_IsInstance() and PyObject_IsSubclass() -- both
returning an int, or -1 for errors.

1 files changed, 112 insertions, 0 deletions

diff --git a/Objects/abstract.c b/Objects/abstract.c
index 1189ae8..3ccac71 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -1626,3 +1626,115 @@ PyObject_CallMethod(PyObject *o, char *name, char *format, ...)
 
 	return retval;
 }
+
+
+/* isinstance(), issubclass() */
+
+static int
+abstract_issubclass(PyObject *derived, PyObject *cls, int first)
+{
+	static PyObject *__bases__ = NULL;
+	PyObject *bases;
+	int i, n;
+	int r = 0;
+
+	if (__bases__ == NULL) {
+		__bases__ = PyString_FromString("__bases__");
+		if (__bases__ == NULL)
+			return -1;
+	}
+
+	if (first) {
+		bases = PyObject_GetAttr(cls, __bases__);
+		if (bases == NULL || !PyTuple_Check(bases)) {
+			Py_XDECREF(bases);
+			PyErr_SetString(PyExc_TypeError,
+					"issubclass() arg 2 must be a class");
+			return -1;
+		}
+		Py_DECREF(bases);
+	}
+
+	if (derived == cls)
+		return 1;
+
+	bases = PyObject_GetAttr(derived, __bases__);
+	if (bases == NULL || !PyTuple_Check(bases)) {
+	        Py_XDECREF(bases);
+		PyErr_SetString(PyExc_TypeError,
+				"issubclass() arg 1 must be a class");
+		return -1;
+	}
+
+	n = PyTuple_GET_SIZE(bases);
+	for (i = 0; i < n; i++) {
+		r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls, 0);
+		if (r != 0)
+			break;
+	}
+
+	Py_DECREF(bases);
+
+	return r;
+}
+
+int
+PyObject_IsInstance(PyObject *inst, PyObject *cls)
+{
+	PyObject *icls;
+	static PyObject *__class__ = NULL;
+	int retval = 0;
+
+        if (PyClass_Check(cls)) {
+		if (PyInstance_Check(inst)) {
+			PyObject *inclass =
+				(PyObject*)((PyInstanceObject*)inst)->in_class;
+			retval = PyClass_IsSubclass(inclass, cls);
+		}
+	}
+	else if (PyType_Check(cls)) {
+		retval = ((PyObject *)(inst->ob_type) == cls);
+	}
+	else if (!PyInstance_Check(inst)) {
+		if (__class__ == NULL) {
+			__class__ = PyString_FromString("__class__");
+			if (__class__ == NULL)
+				return -1;
+		}
+		icls = PyObject_GetAttr(inst, __class__);
+		if (icls != NULL) {
+			retval = abstract_issubclass(icls, cls, 1);
+			Py_DECREF(icls);
+			if (retval < 0 &&
+			    !PyErr_ExceptionMatches(PyExc_TypeError))
+				return -1;
+		}
+		else
+			retval = -1;
+	}
+	else
+		retval = -1;
+
+	if (retval < 0) {
+		PyErr_SetString(PyExc_TypeError,
+				"isinstance() arg 2 must be a class or type");
+	}
+	return retval;
+}
+
+int
+PyObject_IsSubclass(PyObject *derived, PyObject *cls)
+{
+	int retval;
+
+	if (!PyClass_Check(derived) || !PyClass_Check(cls)) {
+		retval = abstract_issubclass(derived, cls, 1);
+	}
+	else {
+		/* shortcut */
+	  	if (!(retval = (derived == cls)))
+			retval = PyClass_IsSubclass(derived, cls);
+	}
+
+	return retval;
+}