/*

 dirs.c - dynamic directory diddling for dirstates

 Copyright 2013 Facebook

 This software may be used and distributed according to the terms of

 the GNU General Public License, incorporated herein by reference.

*/

#define PY_SSIZE_T_CLEAN

#include <Python.h>

#include "util.h"

#ifdef IS_PY3K

#define PYLONG_VALUE(o) ((PyLongObject *)o)->ob_digit[1]

#else

#define PYLONG_VALUE(o) PyInt_AS_LONG(o)

#endif

/*

 * This is a multiset of directory names, built from the files that

 * appear in a dirstate or manifest.

 *

 * A few implementation notes:

 *

 * We modify Python integers for refcounting, but those integers are

 * never visible to Python code.

 *

 * We mutate strings in-place, but leave them immutable once they can

 * be seen by Python code.

 */

typedef struct {

	PyObject_HEAD

	PyObject *dict;

} dirsObject;

static inline Py_ssize_t _finddir(const char *path, Py_ssize_t pos)

{

	while (pos != -1) {

		if (path[pos] == '/')

			break;

		pos -= 1;

	}

	return pos;

}

static int _addpath(PyObject *dirs, PyObject *path)

{

	const char *cpath = PyBytes_AS_STRING(path);

	Py_ssize_t pos = PyBytes_GET_SIZE(path);

	PyObject *key = NULL;

	int ret = -1;

	/* This loop is super critical for performance. That's why we inline

	* access to Python structs instead of going through a supported API.

	* The implementation, therefore, is heavily dependent on CPython

	* implementation details. We also commit violations of the Python

	* "protocol" such as mutating immutable objects. But since we only

	* mutate objects created in this function or in other well-defined

	* locations, the references are known so these violations should go

	* unnoticed. The code for adjusting the length of a PyBytesObject is

	* essentially a minimal version of _PyBytes_Resize. */

	while ((pos = _finddir(cpath, pos - 1)) != -1) {

		PyObject *val;

		/* It's likely that every prefix already has an entry

		   in our dict. Try to avoid allocating and

		   deallocating a string for each prefix we check. */

		if (key != NULL)

			((PyBytesObject *)key)->ob_shash = -1;

		else {

			/* Force Python to not reuse a small shared string. */

			key = PyBytes_FromStringAndSize(cpath,

							 pos < 2 ? 2 : pos);

			if (key == NULL)

				goto bail;

		}

		/* Py_SIZE(o) refers to the ob_size member of the struct. Yes,

		* assigning to what looks like a function seems wrong. */

		Py_SIZE(key) = pos;

		((PyBytesObject *)key)->ob_sval[pos] = '\0';

		val = PyDict_GetItem(dirs, key);

		if (val != NULL) {

			PYLONG_VALUE(val) += 1;

			break;

		}

		/* Force Python to not reuse a small shared int. */

#ifdef IS_PY3K

		val = PyLong_FromLong(0x1eadbeef);

#else

		val = PyInt_FromLong(0x1eadbeef);

#endif

		if (val == NULL)

			goto bail;

		PYLONG_VALUE(val) = 1;

		ret = PyDict_SetItem(dirs, key, val);

		Py_DECREF(val);

		if (ret == -1)

			goto bail;

		Py_CLEAR(key);

	}

	ret = 0;

bail:

	Py_XDECREF(key);

	return ret;

}

static int _delpath(PyObject *dirs, PyObject *path)

{

	char *cpath = PyBytes_AS_STRING(path);

	Py_ssize_t pos = PyBytes_GET_SIZE(path);

	PyObject *key = NULL;

	int ret = -1;

	while ((pos = _finddir(cpath, pos - 1)) != -1) {

		PyObject *val;

		key = PyBytes_FromStringAndSize(cpath, pos);

		if (key == NULL)

			goto bail;

		val = PyDict_GetItem(dirs, key);

		if (val == NULL) {

			PyErr_SetString(PyExc_ValueError,

					"expected a value, found none");

			goto bail;

		}

		if (--PYLONG_VALUE(val) <= 0) {

			if (PyDict_DelItem(dirs, key) == -1)

				goto bail;

		} else

			break;

		Py_CLEAR(key);

	}

	ret = 0;

bail:

	Py_XDECREF(key);

	return ret;

}

static int dirs_fromdict(PyObject *dirs, PyObject *source, char skipchar)

{

	PyObject *key, *value;

	Py_ssize_t pos = 0;

	while (PyDict_Next(source, &pos, &key, &value)) {

		if (!PyBytes_Check(key)) {

			PyErr_SetString(PyExc_TypeError, "expected string key");

			return -1;

		}

		if (skipchar) {

			if (!dirstate_tuple_check(value)) {

				PyErr_SetString(PyExc_TypeError,

						"expected a dirstate tuple");

				return -1;

			}

			if (((dirstateTupleObject *)value)->state == skipchar)

				continue;

		}

		if (_addpath(dirs, key) == -1)

			return -1;

	}

	return 0;

}

static int dirs_fromiter(PyObject *dirs, PyObject *source)

{

	PyObject *iter, *item = NULL;

	int ret;

	iter = PyObject_GetIter(source);

	if (iter == NULL)

		return -1;

	while ((item = PyIter_Next(iter)) != NULL) {

		if (!PyBytes_Check(item)) {

			PyErr_SetString(PyExc_TypeError, "expected string");

			break;

		}

		if (_addpath(dirs, item) == -1)

			break;

		Py_CLEAR(item);

	}

	ret = PyErr_Occurred() ? -1 : 0;

	Py_DECREF(iter);

	Py_XDECREF(item);

	return ret;

}

/*

 * Calculate a refcounted set of directory names for the files in a

 * dirstate.

 */

static int dirs_init(dirsObject *self, PyObject *args)

{

	PyObject *dirs = NULL, *source = NULL;

	char skipchar = 0;

	int ret = -1;

	self->dict = NULL;

	if (!PyArg_ParseTuple(args, "|Oc:__init__", &source, &skipchar))

		return -1;

	dirs = PyDict_New();

	if (dirs == NULL)

		return -1;

	if (source == NULL)

		ret = 0;

	else if (PyDict_Check(source))

		ret = dirs_fromdict(dirs, source, skipchar);

	else if (skipchar)

		PyErr_SetString(PyExc_ValueError,

				"skip character is only supported "

				"with a dict source");

	else

		ret = dirs_fromiter(dirs, source);

	if (ret == -1)

		Py_XDECREF(dirs);

	else

		self->dict = dirs;

	return ret;

}

PyObject *dirs_addpath(dirsObject *self, PyObject *args)

{

	PyObject *path;

	if (!PyArg_ParseTuple(args, "O!:addpath", &PyBytes_Type, &path))

		return NULL;

	if (_addpath(self->dict, path) == -1)

		return NULL;

	Py_RETURN_NONE;

}

static PyObject *dirs_delpath(dirsObject *self, PyObject *args)

{

	PyObject *path;

	if (!PyArg_ParseTuple(args, "O!:delpath", &PyBytes_Type, &path))

		return NULL;

	if (_delpath(self->dict, path) == -1)

		return NULL;

	Py_RETURN_NONE;

}

static int dirs_contains(dirsObject *self, PyObject *value)

{

	return PyBytes_Check(value) ? PyDict_Contains(self->dict, value) : 0;

}

static void dirs_dealloc(dirsObject *self)

{

	Py_XDECREF(self->dict);

	PyObject_Del(self);

}

static PyObject *dirs_iter(dirsObject *self)

{

	return PyObject_GetIter(self->dict);

}

static PySequenceMethods dirs_sequence_methods;

static PyMethodDef dirs_methods[] = {

	{"addpath", (PyCFunction)dirs_addpath, METH_VARARGS, "add a path"},

	{"delpath", (PyCFunction)dirs_delpath, METH_VARARGS, "remove a path"},

	{NULL} /* Sentinel */

};

static PyTypeObject dirsType = { PyVarObject_HEAD_INIT(NULL, 0) };

void dirs_module_init(PyObject *mod)

{

	dirs_sequence_methods.sq_contains = (objobjproc)dirs_contains;

	dirsType.tp_name = "parsers.dirs";

	dirsType.tp_new = PyType_GenericNew;

	dirsType.tp_basicsize = sizeof(dirsObject);

	dirsType.tp_dealloc = (destructor)dirs_dealloc;

	dirsType.tp_as_sequence = &dirs_sequence_methods;

	dirsType.tp_flags = Py_TPFLAGS_DEFAULT;

	dirsType.tp_doc = "dirs";

	dirsType.tp_iter = (getiterfunc)dirs_iter;

	dirsType.tp_methods = dirs_methods;

	dirsType.tp_init = (initproc)dirs_init;

	if (PyType_Ready(&dirsType) < 0)

		return;

	Py_INCREF(&dirsType);

	PyModule_AddObject(mod, "dirs", (PyObject *)&dirsType);

}