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gh-132108: Add Buffer Protocol support to int.from_bytes to improve performance (#132109)

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Speed up conversion from `bytes-like` objects like `bytearray` while
keeping conversion from `bytes` stable.

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>
This commit is contained in:
Cody Maloney 2026-01-13 01:33:26 -08:00 committed by GitHub
parent e5b5a15804
commit 510ab7d6e1
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2 changed files with 29 additions and 8 deletions
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2
Misc/NEWS.d/next/Core_and_Builtins/2025-04-04-20-38-29.gh-issue-132108.UwZIQy.rst Normal file
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@ -0,0 +1,2 @@
Speed up :meth:`int.from_bytes` when passed object supports :ref:`buffer
protocol <bufferobjects>`, like :class:`bytearray` by ~1.2x.

35
Objects/longobject.c
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@ -6476,14 +6476,33 @@ int_from_bytes_impl(PyTypeObject *type, PyObject *bytes_obj,
return NULL;
}
bytes = PyObject_Bytes(bytes_obj);
if (bytes == NULL)
return NULL;
long_obj = _PyLong_FromByteArray(
(unsigned char *)PyBytes_AS_STRING(bytes), Py_SIZE(bytes),
little_endian, is_signed);
Py_DECREF(bytes);
/* Fast-path exact bytes. */
if (PyBytes_CheckExact(bytes_obj)) {
long_obj = _PyLong_FromByteArray(
(unsigned char *)PyBytes_AS_STRING(bytes_obj), Py_SIZE(bytes_obj),
little_endian, is_signed);
}
/* Use buffer protocol to avoid copies. */
else if (PyObject_CheckBuffer(bytes_obj)) {
Py_buffer view;
if (PyObject_GetBuffer(bytes_obj, &view, PyBUF_SIMPLE) != 0) {
return NULL;
}
long_obj = _PyLong_FromByteArray(view.buf, view.len, little_endian,
is_signed);
PyBuffer_Release(&view);
}
else {
/* fallback: Construct a bytes then convert. */
bytes = PyObject_Bytes(bytes_obj);
if (bytes == NULL) {
return NULL;
}
long_obj = _PyLong_FromByteArray(
(unsigned char *)PyBytes_AS_STRING(bytes), Py_SIZE(bytes),
little_endian, is_signed);
Py_DECREF(bytes);
}
if (long_obj != NULL && type != &PyLong_Type) {
Py_SETREF(long_obj, PyObject_CallOneArg((PyObject *)type, long_obj));