libbtrfsutil: add Python bindings

The C libbtrfsutil library isn't very useful for scripting, so we also
want bindings for Python. Writing unit tests in Python is also much
easier than doing so in C. Only Python 3 is supported; if someone really
wants Python 2 support, they can write their own bindings. This commit
is just the scaffolding.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 166 insertions, 0 deletions

diff --git a/libbtrfsutil/python/module.c b/libbtrfsutil/python/module.c
new file mode 100644
index 00000000..d7398808
--- /dev/null
+++ b/libbtrfsutil/python/module.c
@@ -0,0 +1,166 @@
+/*
+ * Copyright (C) 2018 Facebook
+ *
+ * This file is part of libbtrfsutil.
+ *
+ * libbtrfsutil 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * libbtrfsutil 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 libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "btrfsutilpy.h"
+
+static int fd_converter(PyObject *o, void *p)
+{
+	int *fd = p;
+	long tmp;
+	int overflow;
+
+	tmp = PyLong_AsLongAndOverflow(o, &overflow);
+	if (tmp == -1 && PyErr_Occurred())
+		return 0;
+	if (overflow > 0 || tmp > INT_MAX) {
+		PyErr_SetString(PyExc_OverflowError,
+				"fd is greater than maximum");
+		return 0;
+	}
+	if (overflow < 0 || tmp < 0) {
+		PyErr_SetString(PyExc_ValueError, "fd is negative");
+		return 0;
+	}
+	*fd = tmp;
+	return 1;
+}
+
+int path_converter(PyObject *o, void *p)
+{
+	struct path_arg *path = p;
+	int is_index, is_bytes, is_unicode;
+	PyObject *bytes = NULL;
+	Py_ssize_t length = 0;
+	char *tmp;
+
+	if (o == NULL) {
+		path_cleanup(p);
+		return 1;
+	}
+
+	path->object = path->cleanup = NULL;
+	Py_INCREF(o);
+
+	path->fd = -1;
+
+	is_index = path->allow_fd && PyIndex_Check(o);
+	is_bytes = PyBytes_Check(o);
+	is_unicode = PyUnicode_Check(o);
+
+	if (!is_index && !is_bytes && !is_unicode) {
+		_Py_IDENTIFIER(__fspath__);
+		PyObject *func;
+
+		func = _PyObject_LookupSpecial(o, &PyId___fspath__);
+		if (func == NULL)
+			goto err_format;
+		Py_DECREF(o);
+		o = PyObject_CallFunctionObjArgs(func, NULL);
+		Py_DECREF(func);
+		if (o == NULL)
+			return 0;
+		is_bytes = PyBytes_Check(o);
+		is_unicode = PyUnicode_Check(o);
+	}
+
+	if (is_unicode) {
+		if (!PyUnicode_FSConverter(o, &bytes))
+			goto err;
+	} else if (is_bytes) {
+		bytes = o;
+		Py_INCREF(bytes);
+	} else if (is_index) {
+		if (!fd_converter(o, &path->fd))
+			goto err;
+		path->path = NULL;
+		goto out;
+	} else {
+err_format:
+		PyErr_Format(PyExc_TypeError, "expected %s, not %s",
+			     path->allow_fd ? "string, bytes, os.PathLike, or integer" :
+			     "string, bytes, or os.PathLike",
+			     Py_TYPE(o)->tp_name);
+		goto err;
+	}
+
+	length = PyBytes_GET_SIZE(bytes);
+	tmp = PyBytes_AS_STRING(bytes);
+	if ((size_t)length != strlen(tmp)) {
+		PyErr_SetString(PyExc_TypeError,
+				"path has embedded nul character");
+		goto err;
+	}
+
+	path->path = tmp;
+	if (bytes == o)
+		Py_DECREF(bytes);
+	else
+		path->cleanup = bytes;
+	path->fd = -1;
+
+out:
+	path->length = length;
+	path->object = o;
+	return Py_CLEANUP_SUPPORTED;
+
+err:
+	Py_XDECREF(o);
+	Py_XDECREF(bytes);
+	return 0;
+}
+
+void path_cleanup(struct path_arg *path)
+{
+	Py_CLEAR(path->object);
+	Py_CLEAR(path->cleanup);
+}
+
+static PyMethodDef btrfsutil_methods[] = {
+	{},
+};
+
+static struct PyModuleDef btrfsutilmodule = {
+	PyModuleDef_HEAD_INIT,
+	"btrfsutil",
+	"Library for managing Btrfs filesystems",
+	-1,
+	btrfsutil_methods,
+};
+
+PyMODINIT_FUNC
+PyInit_btrfsutil(void)
+{
+	PyObject *m;
+
+	BtrfsUtilError_type.tp_base = (PyTypeObject *)PyExc_OSError;
+	if (PyType_Ready(&BtrfsUtilError_type) < 0)
+		return NULL;
+
+	m = PyModule_Create(&btrfsutilmodule);
+	if (!m)
+		return NULL;
+
+	Py_INCREF(&BtrfsUtilError_type);
+	PyModule_AddObject(m, "BtrfsUtilError",
+			   (PyObject *)&BtrfsUtilError_type);
+
+	add_module_constants(m);
+
+	return m;
+}