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.
/*
base85 codec
Copyright 2006 Brendan Cully <brendan@kublai.com>
This software may be used and distributed according to the terms of
the GNU General Public License, incorporated herein by reference.
Largely based on git's implementation
*/
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include "util.h"
static const char b85chars[] =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~";
static char b85dec[256];
static void b85prep(void)
{
unsigned i;
memset(b85dec, 0, sizeof(b85dec));
for (i = 0; i < sizeof(b85chars); i++) {
b85dec[(int)(b85chars[i])] = i + 1;
}
}
static PyObject *b85encode(PyObject *self, PyObject *args)
{
const unsigned char *text;
PyObject *out;
char *dst;
Py_ssize_t len, olen, i;
unsigned int acc, val, ch;
int pad = 0;
if (!PyArg_ParseTuple(args, "y#|i", &text, &len, &pad)) {
return NULL;
}
if (pad) {
olen = ((len + 3) / 4 * 5) - 3;
} else {
olen = len % 4;
if (olen) {
olen++;
}
olen += len / 4 * 5;
}
if (!(out = PyBytes_FromStringAndSize(NULL, olen + 3))) {
return NULL;
}
dst = PyBytes_AsString(out);
while (len) {
acc = 0;
for (i = 24; i >= 0; i -= 8) {
ch = *text++;
acc |= ch << i;
if (--len == 0) {
break;
}
}
for (i = 4; i >= 0; i--) {
val = acc % 85;
acc /= 85;
dst[i] = b85chars[val];
}
dst += 5;
}
if (!pad) {
_PyBytes_Resize(&out, olen);
}
return out;
}
static PyObject *b85decode(PyObject *self, PyObject *args)
{
PyObject *out = NULL;
const char *text;
char *dst;
Py_ssize_t len, i, j, olen, cap;
int c;
unsigned int acc;
if (!PyArg_ParseTuple(args, "y#", &text, &len)) {
return NULL;
}
olen = len / 5 * 4;
i = len % 5;
if (i) {
olen += i - 1;
}
if (!(out = PyBytes_FromStringAndSize(NULL, olen))) {
return NULL;
}
dst = PyBytes_AsString(out);
i = 0;
while (i < len) {
acc = 0;
cap = len - i - 1;
if (cap > 4) {
cap = 4;
}
for (j = 0; j < cap; i++, j++) {
c = b85dec[(int)*text++] - 1;
if (c < 0) {
PyErr_Format(
PyExc_ValueError,
"bad base85 character at position %d",
(int)i);
goto bail;
}
acc = acc * 85 + c;
}
if (i++ < len) {
c = b85dec[(int)*text++] - 1;
if (c < 0) {
PyErr_Format(
PyExc_ValueError,
"bad base85 character at position %d",
(int)i);
goto bail;
}
/* overflow detection: 0xffffffff == "|NsC0",
* "|NsC" == 0x03030303 */
if (acc > 0x03030303 || (acc *= 85) > 0xffffffff - c) {
PyErr_Format(
PyExc_ValueError,
"bad base85 sequence at position %d",
(int)i);
goto bail;
}
acc += c;
}
cap = olen < 4 ? olen : 4;
olen -= cap;
for (j = 0; j < 4 - cap; j++) {
acc *= 85;
}
if (cap && cap < 4) {
acc += 0xffffff >> (cap - 1) * 8;
}
for (j = 0; j < cap; j++) {
acc = (acc << 8) | (acc >> 24);
*dst++ = acc;
}
}
return out;
bail:
Py_XDECREF(out);
return NULL;
}
static char base85_doc[] = "Base85 Data Encoding";
static PyMethodDef methods[] = {
{"b85encode", b85encode, METH_VARARGS,
"Encode text in base85.\n\n"
"If the second parameter is true, pad the result to a multiple of "
"five characters.\n"},
{"b85decode", b85decode, METH_VARARGS, "Decode base85 text.\n"},
{NULL, NULL},
};
static const int version = 1;
static struct PyModuleDef base85_module = {
PyModuleDef_HEAD_INIT, "base85", base85_doc, -1, methods,
};
PyMODINIT_FUNC PyInit_base85(void)
{
PyObject *m;
b85prep();
m = PyModule_Create(&base85_module);
PyModule_AddIntConstant(m, "version", version);
return m;
}