Unify `PyUncode_Count` and `unicode_count`

[sobolevn]

Feature or enhancement

Right now PyUnicode_Count from

cpython/Objects/unicodeobject.c

Lines 8968 to 9040 in cbdeda8

	Py_ssize_t
	PyUnicode_Count(PyObject *str,
	PyObject *substr,
	Py_ssize_t start,
	Py_ssize_t end)
	{
	Py_ssize_t result;
	int kind1, kind2;
	const void *buf1 = NULL, *buf2 = NULL;
	Py_ssize_t len1, len2;
	if (ensure_unicode(str) < 0 || ensure_unicode(substr) < 0)
	return -1;
	kind1 = PyUnicode_KIND(str);
	kind2 = PyUnicode_KIND(substr);
	if (kind1 < kind2)
	return 0;
	len1 = PyUnicode_GET_LENGTH(str);
	len2 = PyUnicode_GET_LENGTH(substr);
	ADJUST_INDICES(start, end, len1);
	if (end - start < len2)
	return 0;
	buf1 = PyUnicode_DATA(str);
	buf2 = PyUnicode_DATA(substr);
	if (kind2 != kind1){
	buf2 = unicode_askind(kind2, buf2, len2, kind1);
	if (!buf2)
	goto onError;
	}
	switch (kind1){
	case PyUnicode_1BYTE_KIND:
	if (PyUnicode_IS_ASCII(str) && PyUnicode_IS_ASCII(substr))
	result = asciilib_count(
	((const Py_UCS1*)buf1) + start, end - start,
	buf2, len2, PY_SSIZE_T_MAX
	);
	else
	result = ucs1lib_count(
	((const Py_UCS1*)buf1) + start, end - start,
	buf2, len2, PY_SSIZE_T_MAX
	);
	break;
	case PyUnicode_2BYTE_KIND:
	result = ucs2lib_count(
	((const Py_UCS2*)buf1) + start, end - start,
	buf2, len2, PY_SSIZE_T_MAX
	);
	break;
	case PyUnicode_4BYTE_KIND:
	result = ucs4lib_count(
	((const Py_UCS4*)buf1) + start, end - start,
	buf2, len2, PY_SSIZE_T_MAX
	);
	break;
	default:
	Py_UNREACHABLE();
	}
	assert((kind2 != kind1) == (buf2 != PyUnicode_DATA(substr)));
	if (kind2 != kind1)
	PyMem_Free((void *)buf2);
	return result;
	onError:
	assert((kind2 != kind1) == (buf2 != PyUnicode_DATA(substr)));
	if (kind2 != kind1)
	PyMem_Free((void *)buf2);
	return -1;
	}

and unicode_count from

cpython/Objects/unicodeobject.c

Lines 10854 to 10916 in cbdeda8

	static PyObject *
	unicode_count(PyObject *self, PyObject *args)
	{
	PyObject *substring = NULL; /* initialize to fix a compiler warning */
	Py_ssize_t start = 0;
	Py_ssize_t end = PY_SSIZE_T_MAX;
	PyObject *result;
	int kind1, kind2;
	const void *buf1, *buf2;
	Py_ssize_t len1, len2, iresult;
	if (!parse_args_finds_unicode("count", args, &substring, &start, &end))
	return NULL;
	kind1 = PyUnicode_KIND(self);
	kind2 = PyUnicode_KIND(substring);
	if (kind1 < kind2)
	return PyLong_FromLong(0);
	len1 = PyUnicode_GET_LENGTH(self);
	len2 = PyUnicode_GET_LENGTH(substring);
	ADJUST_INDICES(start, end, len1);
	if (end - start < len2)
	return PyLong_FromLong(0);
	buf1 = PyUnicode_DATA(self);
	buf2 = PyUnicode_DATA(substring);
	if (kind2 != kind1){
	buf2 = unicode_askind(kind2, buf2, len2, kind1);
	if (!buf2)
	return NULL;
	}
	switch (kind1){
	case PyUnicode_1BYTE_KIND:
	iresult = ucs1lib_count(
	((const Py_UCS1*)buf1) + start, end - start,
	buf2, len2, PY_SSIZE_T_MAX
	);
	break;
	case PyUnicode_2BYTE_KIND:
	iresult = ucs2lib_count(
	((const Py_UCS2*)buf1) + start, end - start,
	buf2, len2, PY_SSIZE_T_MAX
	);
	break;
	case PyUnicode_4BYTE_KIND:
	iresult = ucs4lib_count(
	((const Py_UCS4*)buf1) + start, end - start,
	buf2, len2, PY_SSIZE_T_MAX
	);
	break;
	default:
	Py_UNREACHABLE();
	}
	result = PyLong_FromSsize_t(iresult);
	assert((kind2 == kind1) == (buf2 == PyUnicode_DATA(substring)));
	if (kind2 != kind1)
	PyMem_Free((void *)buf2);
	return result;
	}

share a lot of code.

They can be unified, because the do the same thing.

Pitch

Citing @encukou:

Apparently unicode_count missed an optimization in 2011, otherwise they're equivalent (except arg parsing & converting the return value). Merging them could add the optimization to unicode_count.
If you want to work on that, note that there's also anylib_count that duplicates the main switch.

Previous discussion

Link: #96929

PR in the works.

[vstinner]

I remove asciilib_count() function in commit df3a6d9.

[vstinner]

Fixed by ccab67b