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gh-129813, PEP 782: Use PyBytesWriter in posix extension #138829

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merged 1 commit into from
Sep 13, 2025
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gh-129813, PEP 782: Use PyBytesWriter in posix extension #138829

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95 changes: 36 additions & 59 deletions Modules/posixmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -11507,30 +11507,25 @@ static PyObject *
os_read_impl(PyObject *module, int fd, Py_ssize_t length)
/*[clinic end generated code: output=dafbe9a5cddb987b input=1df2eaa27c0bf1d3]*/
{
Py_ssize_t n;
PyObject *buffer;

if (length < 0) {
errno = EINVAL;
return posix_error();
}

length = Py_MIN(length, _PY_READ_MAX);

buffer = PyBytes_FromStringAndSize((char *)NULL, length);
if (buffer == NULL)
PyBytesWriter *writer = PyBytesWriter_Create(length);
if (writer == NULL) {
return NULL;
}

n = _Py_read(fd, PyBytes_AS_STRING(buffer), length);
Py_ssize_t n = _Py_read(fd, PyBytesWriter_GetData(writer), length);
if (n == -1) {
Py_DECREF(buffer);
PyBytesWriter_Discard(writer);
return NULL;
}

if (n != length)
_PyBytes_Resize(&buffer, n);

return buffer;
return PyBytesWriter_FinishWithSize(writer, n);
}

/*[clinic input]
Expand Down Expand Up @@ -11708,20 +11703,20 @@ os_pread_impl(PyObject *module, int fd, Py_ssize_t length, Py_off_t offset)
{
Py_ssize_t n;
int async_err = 0;
PyObject *buffer;

if (length < 0) {
errno = EINVAL;
return posix_error();
}
buffer = PyBytes_FromStringAndSize((char *)NULL, length);
if (buffer == NULL)
PyBytesWriter *writer = PyBytesWriter_Create(length);
if (writer == NULL) {
return NULL;
}

do {
Py_BEGIN_ALLOW_THREADS
_Py_BEGIN_SUPPRESS_IPH
n = pread(fd, PyBytes_AS_STRING(buffer), length, offset);
n = pread(fd, PyBytesWriter_GetData(writer), length, offset);
_Py_END_SUPPRESS_IPH
Py_END_ALLOW_THREADS
} while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
Expand All @@ -11730,12 +11725,10 @@ os_pread_impl(PyObject *module, int fd, Py_ssize_t length, Py_off_t offset)
if (!async_err) {
posix_error();
}
Py_DECREF(buffer);
PyBytesWriter_Discard(writer);
return NULL;
}
if (n != length)
_PyBytes_Resize(&buffer, n);
return buffer;
return PyBytesWriter_FinishWithSize(writer, n);
}
#endif /* HAVE_PREAD */

Expand Down Expand Up @@ -14945,29 +14938,26 @@ os_getxattr_impl(PyObject *module, path_t *path, path_t *attribute,
int follow_symlinks)
/*[clinic end generated code: output=5f2f44200a43cff2 input=025789491708f7eb]*/
{
Py_ssize_t i;
PyObject *buffer = NULL;

if (fd_and_follow_symlinks_invalid("getxattr", path->fd, follow_symlinks))
return NULL;

if (PySys_Audit("os.getxattr", "OO", path->object, attribute->object) < 0) {
return NULL;
}

for (i = 0; ; i++) {
void *ptr;
for (Py_ssize_t i = 0; ; i++) {
ssize_t result;
static const Py_ssize_t buffer_sizes[] = {128, XATTR_SIZE_MAX, 0};
Py_ssize_t buffer_size = buffer_sizes[i];
if (!buffer_size) {
path_error(path);
return NULL;
}
buffer = PyBytes_FromStringAndSize(NULL, buffer_size);
if (!buffer)
PyBytesWriter *writer = PyBytesWriter_Create(buffer_size);
if (writer == NULL) {
return NULL;
ptr = PyBytes_AS_STRING(buffer);
}
void *ptr = PyBytesWriter_GetData(writer);

Py_BEGIN_ALLOW_THREADS;
if (path->fd >= 0)
Expand All @@ -14979,23 +14969,16 @@ os_getxattr_impl(PyObject *module, path_t *path, path_t *attribute,
Py_END_ALLOW_THREADS;

if (result < 0) {
PyBytesWriter_Discard(writer);
if (errno == ERANGE) {
Py_DECREF(buffer);
continue;
}
path_error(path);
Py_DECREF(buffer);
return NULL;
}

if (result != buffer_size) {
/* Can only shrink. */
_PyBytes_Resize(&buffer, result);
}
break;
return PyBytesWriter_FinishWithSize(writer, result);
}

return buffer;
}


Expand Down Expand Up @@ -15222,19 +15205,22 @@ static PyObject *
os_urandom_impl(PyObject *module, Py_ssize_t size)
/*[clinic end generated code: output=42c5cca9d18068e9 input=58a0def87dbc2c22]*/
{
PyObject *bytes;
int result;
if (size < 0) {
return PyErr_Format(PyExc_ValueError,
"negative argument not allowed");
}

bytes = PyBytes_FromStringAndSize(NULL, size);
if (bytes == NULL)
PyBytesWriter *writer = PyBytesWriter_Create(size);
if (writer == NULL) {
return NULL;
}

result = _PyOS_URandom(PyBytes_AS_STRING(bytes), PyBytes_GET_SIZE(bytes));
int result = _PyOS_URandom(PyBytesWriter_GetData(writer), size);
if (result == -1) {
Py_DECREF(bytes);
PyBytesWriter_Discard(writer);
return NULL;
}
return bytes;
return PyBytesWriter_Finish(writer);
}

#ifdef HAVE_MEMFD_CREATE
Expand Down Expand Up @@ -16704,25 +16690,20 @@ static PyObject *
os_getrandom_impl(PyObject *module, Py_ssize_t size, int flags)
/*[clinic end generated code: output=b3a618196a61409c input=59bafac39c594947]*/
{
PyObject *bytes;
Py_ssize_t n;

if (size < 0) {
errno = EINVAL;
return posix_error();
}

bytes = PyBytes_FromStringAndSize(NULL, size);
if (bytes == NULL) {
PyErr_NoMemory();
PyBytesWriter *writer = PyBytesWriter_Create(size);
if (writer == NULL) {
return NULL;
}
void *data = PyBytesWriter_GetData(writer);

Py_ssize_t n;
while (1) {
n = syscall(SYS_getrandom,
PyBytes_AS_STRING(bytes),
PyBytes_GET_SIZE(bytes),
flags);
n = syscall(SYS_getrandom, data, size, flags);
if (n < 0 && errno == EINTR) {
if (PyErr_CheckSignals() < 0) {
goto error;
Expand All @@ -16739,14 +16720,10 @@ os_getrandom_impl(PyObject *module, Py_ssize_t size, int flags)
goto error;
}

if (n != size) {
_PyBytes_Resize(&bytes, n);
}

return bytes;
return PyBytesWriter_FinishWithSize(writer, n);

error:
Py_DECREF(bytes);
PyBytesWriter_Discard(writer);
return NULL;
}
#endif /* HAVE_GETRANDOM_SYSCALL */
Expand Down
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