Add from_buffer and from_buffer_copy class methods to ctypes types.

1 files changed, 115 insertions, 0 deletions

diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index c9da7d3..1bb76e3 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -412,6 +412,115 @@ CDataType_from_address(PyObject *type, PyObject *value)
 	return CData_AtAddress(type, buf);
 }
 
+static char from_buffer_doc[] =
+"C.from_buffer(object, offset=0) -> C instance\ncreate a C instance from a writeable buffer";
+
+static int
+KeepRef(CDataObject *target, Py_ssize_t index, PyObject *keep);
+
+static PyObject *
+CDataType_from_buffer(PyObject *type, PyObject *args)
+{
+	void *buffer;
+	Py_ssize_t buffer_len;
+	Py_ssize_t offset = 0;
+	PyObject *obj, *result;
+	StgDictObject *dict = PyType_stgdict(type);
+	assert (dict);
+
+	if (!PyArg_ParseTuple(args,
+#if (PY_VERSION_HEX < 0x02050000)
+			      "O|i:from_buffer",
+#else
+			      "O|n:from_buffer",
+#endif
+			      &obj, &offset))
+		return NULL;
+
+	if (-1 == PyObject_AsWriteBuffer(obj, &buffer, &buffer_len))
+		return NULL;
+
+	if (offset < 0) {
+		PyErr_SetString(PyExc_ValueError,
+				"offset cannit be negative");
+		return NULL;
+	}
+	if (dict->size > buffer_len - offset) {
+		PyErr_Format(PyExc_ValueError,
+#if (PY_VERSION_HEX < 0x02050000)
+			     "Buffer size too small (%d instead of at least %d bytes)",
+#else
+			     "Buffer size too small (%zd instead of at least %zd bytes)",
+#endif
+			     buffer_len, dict->size + offset);
+		return NULL;
+	}
+
+	result = CData_AtAddress(type, (char *)buffer + offset);
+	if (result == NULL)
+		return NULL;
+
+	Py_INCREF(obj);
+	if (-1 == KeepRef((CDataObject *)result, -1, obj)) {
+		Py_DECREF(result);
+		return NULL;
+	}
+	return result;
+}
+
+static char from_buffer_copy_doc[] =
+"C.from_buffer_copy(object, offset=0) -> C instance\ncreate a C instance from a readable buffer";
+
+static PyObject *
+GenericCData_new(PyTypeObject *type, PyObject *args, PyObject *kwds);
+
+static PyObject *
+CDataType_from_buffer_copy(PyObject *type, PyObject *args)
+{
+	void *buffer;
+	Py_ssize_t buffer_len;
+	Py_ssize_t offset = 0;
+	PyObject *obj, *result;
+	StgDictObject *dict = PyType_stgdict(type);
+	assert (dict);
+
+	if (!PyArg_ParseTuple(args,
+#if (PY_VERSION_HEX < 0x02050000)
+			      "O|i:from_buffer",
+#else
+			      "O|n:from_buffer",
+#endif
+			      &obj, &offset))
+		return NULL;
+
+	if (-1 == PyObject_AsReadBuffer(obj, &buffer, &buffer_len))
+		return NULL;
+
+	if (offset < 0) {
+		PyErr_SetString(PyExc_ValueError,
+				"offset cannit be negative");
+		return NULL;
+	}
+
+	if (dict->size > buffer_len - offset) {
+		PyErr_Format(PyExc_ValueError,
+#if (PY_VERSION_HEX < 0x02050000)
+			     "Buffer size too small (%d instead of at least %d bytes)",
+#else
+			     "Buffer size too small (%zd instead of at least %zd bytes)",
+#endif
+			     buffer_len, dict->size + offset);
+		return NULL;
+	}
+
+	result = GenericCData_new((PyTypeObject *)type, NULL, NULL);
+	if (result == NULL)
+		return NULL;
+	memcpy(((CDataObject *)result)->b_ptr,
+	       (char *)buffer+offset, dict->size);
+	return result;
+}
+
 static char in_dll_doc[] =
 "C.in_dll(dll, name) -> C instance\naccess a C instance in a dll";
 
@@ -516,6 +625,8 @@ CDataType_from_param(PyObject *type, PyObject *value)
 static PyMethodDef CDataType_methods[] = {
 	{ "from_param", CDataType_from_param, METH_O, from_param_doc },
 	{ "from_address", CDataType_from_address, METH_O, from_address_doc },
+	{ "from_buffer", CDataType_from_buffer, METH_VARARGS, from_buffer_doc, },
+	{ "from_buffer_copy", CDataType_from_buffer_copy, METH_VARARGS, from_buffer_copy_doc, },
 	{ "in_dll", CDataType_in_dll, METH_VARARGS, in_dll_doc },
 	{ NULL, NULL },
 };
@@ -845,6 +956,8 @@ PointerType_from_param(PyObject *type, PyObject *value)
 
 static PyMethodDef PointerType_methods[] = {
 	{ "from_address", CDataType_from_address, METH_O, from_address_doc },
+	{ "from_buffer", CDataType_from_buffer, METH_VARARGS, from_buffer_doc, },
+	{ "from_buffer_copy", CDataType_from_buffer_copy, METH_VARARGS, from_buffer_copy_doc, },
 	{ "in_dll", CDataType_in_dll, METH_VARARGS, in_dll_doc},
 	{ "from_param", (PyCFunction)PointerType_from_param, METH_O, from_param_doc},
 	{ "set_type", (PyCFunction)PointerType_set_type, METH_O },
@@ -1859,6 +1972,8 @@ SimpleType_from_param(PyObject *type, PyObject *value)
 static PyMethodDef SimpleType_methods[] = {
 	{ "from_param", SimpleType_from_param, METH_O, from_param_doc },
 	{ "from_address", CDataType_from_address, METH_O, from_address_doc },
+	{ "from_buffer", CDataType_from_buffer, METH_VARARGS, from_buffer_doc, },
+	{ "from_buffer_copy", CDataType_from_buffer_copy, METH_VARARGS, from_buffer_copy_doc, },
 	{ "in_dll", CDataType_in_dll, METH_VARARGS, in_dll_doc},
 	{ NULL, NULL },
 };