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gh-129813, PEP 782: Use PyBytesWriter in _PyBytes_FormatEx() #138839

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Merged
merged 2 commits into from
Sep 15, 2025
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gh-129813, PEP 782: Use PyBytesWriter in _PyBytes_FormatEx() #138839

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aee6552
gh-129813, PEP 782: Use PyBytesWriter in _PyBytes_FormatEx()
vstinner Sep 12, 2025
4dbf187
Merge branch 'main' into pybyteswriter_bytes_format
vstinner Sep 14, 2025
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2 changes: 1 addition & 1 deletion Include/internal/pycore_long.h
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Original file line number Diff line number Diff line change
Expand Up @@ -135,7 +135,7 @@ extern int _PyLong_FormatWriter(
int alternate);

extern char* _PyLong_FormatBytesWriter(
_PyBytesWriter *writer,
PyBytesWriter *writer,
char *str,
PyObject *obj,
int base,
Expand Down
47 changes: 19 additions & 28 deletions Objects/bytesobject.c
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Expand Up @@ -432,7 +432,7 @@ getnextarg(PyObject *args, Py_ssize_t arglen, Py_ssize_t *p_argidx)

static char*
formatfloat(PyObject *v, int flags, int prec, int type,
PyObject **p_result, _PyBytesWriter *writer, char *str)
PyObject **p_result, PyBytesWriter *writer, char *str)
{
char *p;
PyObject *result;
Expand Down Expand Up @@ -460,7 +460,7 @@ formatfloat(PyObject *v, int flags, int prec, int type,

len = strlen(p);
if (writer != NULL) {
str = _PyBytesWriter_Prepare(writer, str, len);
str = PyBytesWriter_GrowAndUpdatePointer(writer, len, str);
if (str == NULL) {
PyMem_Free(p);
return NULL;
Expand Down Expand Up @@ -611,12 +611,10 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
PyObject *args, int use_bytearray)
{
const char *fmt;
char *res;
Py_ssize_t arglen, argidx;
Py_ssize_t fmtcnt;
int args_owned = 0;
PyObject *dict = NULL;
_PyBytesWriter writer;

if (args == NULL) {
PyErr_BadInternalCall();
Expand All @@ -625,14 +623,17 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
fmt = format;
fmtcnt = format_len;

_PyBytesWriter_Init(&writer);
writer.use_bytearray = use_bytearray;

res = _PyBytesWriter_Alloc(&writer, fmtcnt);
if (res == NULL)
PyBytesWriter *writer;
if (use_bytearray) {
writer = _PyBytesWriter_CreateByteArray(fmtcnt);
}
else {
writer = PyBytesWriter_Create(fmtcnt);
}
if (writer == NULL) {
return NULL;
if (!use_bytearray)
writer.overallocate = 1;
}
char *res = PyBytesWriter_GetData(writer);

if (PyTuple_Check(args)) {
arglen = PyTuple_GET_SIZE(args);
Expand Down Expand Up @@ -835,11 +836,6 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
if (v == NULL)
goto error;

if (fmtcnt == 0) {
/* last write: disable writer overallocation */
writer.overallocate = 0;
}

sign = 0;
fill = ' ';
switch (c) {
Expand Down Expand Up @@ -900,8 +896,7 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
}

/* Fast path */
writer.min_size -= 2; /* size preallocated for "%d" */
res = _PyLong_FormatBytesWriter(&writer, res,
res = _PyLong_FormatBytesWriter(writer, res,
v, base, alternate);
if (res == NULL)
goto error;
Expand Down Expand Up @@ -929,8 +924,7 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
&& !(flags & (F_SIGN | F_BLANK)))
{
/* Fast path */
writer.min_size -= 2; /* size preallocated for "%f" */
res = formatfloat(v, flags, prec, c, NULL, &writer, res);
res = formatfloat(v, flags, prec, c, NULL, writer, res);
if (res == NULL)
goto error;
continue;
Expand Down Expand Up @@ -986,9 +980,10 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
alloc++;
/* 2: size preallocated for %s */
if (alloc > 2) {
res = _PyBytesWriter_Prepare(&writer, res, alloc - 2);
if (res == NULL)
res = PyBytesWriter_GrowAndUpdatePointer(writer, alloc - 2, res);
if (res == NULL) {
goto error;
}
}
#ifndef NDEBUG
char *before = res;
Expand Down Expand Up @@ -1061,10 +1056,6 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
assert((res - before) == alloc);
#endif
} /* '%' */

/* If overallocation was disabled, ensure that it was the last
write. Otherwise, we missed an optimization */
assert(writer.overallocate || fmtcnt == 0 || use_bytearray);
} /* until end */

if (argidx < arglen && !dict) {
Expand All @@ -1076,10 +1067,10 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
if (args_owned) {
Py_DECREF(args);
}
return _PyBytesWriter_Finish(&writer, res);
return PyBytesWriter_FinishWithPointer(writer, res);

error:
_PyBytesWriter_Dealloc(&writer);
PyBytesWriter_Discard(writer);
if (args_owned) {
Py_DECREF(args);
}
Expand Down
30 changes: 16 additions & 14 deletions Objects/longobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2020,7 +2020,7 @@ static int
pylong_int_to_decimal_string(PyObject *aa,
PyObject **p_output,
_PyUnicodeWriter *writer,
_PyBytesWriter *bytes_writer,
PyBytesWriter *bytes_writer,
char **bytes_str)
{
PyObject *s = NULL;
Expand Down Expand Up @@ -2051,7 +2051,8 @@ pylong_int_to_decimal_string(PyObject *aa,
Py_ssize_t size = PyUnicode_GET_LENGTH(s);
const void *data = PyUnicode_DATA(s);
int kind = PyUnicode_KIND(s);
*bytes_str = _PyBytesWriter_Prepare(bytes_writer, *bytes_str, size);
*bytes_str = PyBytesWriter_GrowAndUpdatePointer(bytes_writer, size,
*bytes_str);
if (*bytes_str == NULL) {
goto error;
}
Expand Down Expand Up @@ -2088,7 +2089,7 @@ static int
long_to_decimal_string_internal(PyObject *aa,
PyObject **p_output,
_PyUnicodeWriter *writer,
_PyBytesWriter *bytes_writer,
PyBytesWriter *bytes_writer,
char **bytes_str)
{
PyLongObject *scratch, *a;
Expand Down Expand Up @@ -2214,7 +2215,8 @@ long_to_decimal_string_internal(PyObject *aa,
}
}
else if (bytes_writer) {
*bytes_str = _PyBytesWriter_Prepare(bytes_writer, *bytes_str, strlen);
*bytes_str = PyBytesWriter_GrowAndUpdatePointer(bytes_writer, strlen,
*bytes_str);
if (*bytes_str == NULL) {
Py_DECREF(scratch);
return -1;
Expand Down Expand Up @@ -2324,7 +2326,7 @@ long_to_decimal_string(PyObject *aa)
static int
long_format_binary(PyObject *aa, int base, int alternate,
PyObject **p_output, _PyUnicodeWriter *writer,
_PyBytesWriter *bytes_writer, char **bytes_str)
PyBytesWriter *bytes_writer, char **bytes_str)
{
PyLongObject *a = (PyLongObject *)aa;
PyObject *v = NULL;
Expand Down Expand Up @@ -2385,7 +2387,8 @@ long_format_binary(PyObject *aa, int base, int alternate,
return -1;
}
else if (bytes_writer) {
*bytes_str = _PyBytesWriter_Prepare(bytes_writer, *bytes_str, sz);
*bytes_str = PyBytesWriter_GrowAndUpdatePointer(bytes_writer, sz,
*bytes_str);
if (*bytes_str == NULL)
return -1;
}
Expand Down Expand Up @@ -2514,7 +2517,7 @@ _PyLong_FormatWriter(_PyUnicodeWriter *writer,
}

char*
_PyLong_FormatBytesWriter(_PyBytesWriter *writer, char *str,
_PyLong_FormatBytesWriter(PyBytesWriter *writer, char *str,
PyObject *obj,
int base, int alternate)
{
Expand Down Expand Up @@ -6403,8 +6406,6 @@ int_to_bytes_impl(PyObject *self, Py_ssize_t length, PyObject *byteorder,
/*[clinic end generated code: output=89c801df114050a3 input=66f9d0c20529b44f]*/
{
int little_endian;
PyObject *bytes;

if (byteorder == NULL)
little_endian = 0;
else if (_PyUnicode_Equal(byteorder, &_Py_ID(little)))
Expand All @@ -6417,18 +6418,19 @@ int_to_bytes_impl(PyObject *self, Py_ssize_t length, PyObject *byteorder,
return NULL;
}

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

if (_PyLong_AsByteArray((PyLongObject *)self,
(unsigned char *)PyBytes_AS_STRING(bytes),
PyBytesWriter_GetData(writer),
length, little_endian, is_signed, 1) < 0) {
Py_DECREF(bytes);
PyBytesWriter_Discard(writer);
return NULL;
}

return bytes;
return PyBytesWriter_Finish(writer);
}

/*[clinic input]
Expand Down
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