procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
/*
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 <string.h>
#include "util.h"
#define PYLONG_VALUE(o) ((PyLongObject *)o)->ob_digit[0]
/*
* 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.
*/
/* clang-format off */
typedef struct {
PyObject_HEAD
PyObject *dict;
} dirsObject;
/* clang-format on */
static inline Py_ssize_t _finddir(const char *path, Py_ssize_t pos)
{
while (pos != -1) {
if (path[pos] == '/')
break;
pos -= 1;
}
if (pos == -1) {
return 0;
}
return pos;
}
/* Mercurial will fail to run on directory hierarchies deeper than
* this constant, so we should try and keep this constant as big as
* possible.
*/
#define MAX_DIRS_DEPTH 2048
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;
size_t num_slashes = 0;
/* 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. */
while ((pos = _finddir(cpath, pos - 1)) != -1) {
PyObject *val;
++num_slashes;
if (num_slashes > MAX_DIRS_DEPTH) {
PyErr_SetString(PyExc_ValueError,
"Directory hierarchy too deep.");
goto bail;
}
/* Sniff for trailing slashes, a marker of an invalid input. */
if (pos > 0 && cpath[pos - 1] == '/') {
PyErr_SetString(
PyExc_ValueError,
"found invalid consecutive slashes in path");
goto bail;
}
key = PyBytes_FromStringAndSize(cpath, pos);
if (key == NULL)
goto bail;
val = PyDict_GetItem(dirs, key);
if (val != NULL) {
PYLONG_VALUE(val) += 1;
Py_CLEAR(key);
break;
}
/* Force Python to not reuse a small shared int. */
val = PyLong_FromLong(0x1eadbeef);
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, bool only_tracked)
{
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 (only_tracked) {
if (!dirstate_tuple_check(value)) {
PyErr_SetString(PyExc_TypeError,
"expected a dirstate tuple");
return -1;
}
if (!(((dirstateItemObject *)value)->flags &
dirstate_flag_wc_tracked))
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 *kwargs)
{
PyObject *dirs = NULL, *source = NULL;
int only_tracked = 0;
int ret = -1;
static char *keywords_name[] = {"map", "only_tracked", NULL};
self->dict = NULL;
if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|Oi:__init__",
keywords_name, &source, &only_tracked))
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, (bool)only_tracked);
else if (only_tracked)
PyErr_SetString(PyExc_ValueError,
"`only_tracked` 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);
}