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Simplify control flow in _Traits_find_MEOW_not_of #5006

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merged 11 commits into from
Oct 12, 2024
Merged

Simplify control flow in _Traits_find_MEOW_not_of #5006

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703982f
Replace unnecessarily confusing `break`s with immediate `return`s.
StephanTLavavej Oct 9, 2024
e2918bb
Add a `return` instead of relying on fall-through.
StephanTLavavej Oct 9, 2024
e968071
Flip `!_Matches._Mark` tests.
StephanTLavavej Oct 9, 2024
d892ca8
Transform "call self with `_Special=false`" to fall-through.
StephanTLavavej Oct 9, 2024
d11acd0
Extract `_Elem`.
StephanTLavavej Oct 9, 2024
5b2d81a
Extract `_Hay_start`, `_Hay_end`.
StephanTLavavej Oct 10, 2024
e22295f
Fuse `bool _Special` into its usage.
StephanTLavavej Oct 10, 2024
8d902d9
Use early returns to reduce indentation
CaseyCarter Oct 10, 2024
9a248c3
Revert changes to `_Traits_find_last_of`
CaseyCarter Oct 10, 2024
f7a8c35
Elide dead returns
CaseyCarter Oct 10, 2024
e801c71
Merge branch 'main' into transform-find-meow-of
StephanTLavavej Oct 12, 2024
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91 changes: 47 additions & 44 deletions stl/inc/__msvc_string_view.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -635,7 +635,7 @@ constexpr size_t _Traits_rfind(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
return static_cast<size_t>(-1); // at beginning, no more chance for match
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}
}
}
Expand All @@ -654,7 +654,7 @@ constexpr size_t _Traits_rfind_ch(_In_reads_(_Hay_size) const _Traits_ptr_t<_Tra
}
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if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}
}
Expand Down Expand Up @@ -714,7 +714,7 @@ class _String_bitmap<_Elem, false> { // _String_bitmap for wchar_t/unsigned shor
bool _Matches[256] = {};
};

template <class _Traits, bool _Special = _Is_implementation_handled_char_traits<_Traits>>
template <class _Traits>
constexpr size_t _Traits_find_first_of(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack,
const size_t _Hay_size, const size_t _Start_at, _In_reads_(_Needle_size) const _Traits_ptr_t<_Traits> _Needle,
const size_t _Needle_size) noexcept {
Expand All @@ -723,7 +723,7 @@ constexpr size_t _Traits_find_first_of(_In_reads_(_Hay_size) const _Traits_ptr_t
const auto _Hay_start = _Haystack + _Start_at;
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const auto _Hay_end = _Haystack + _Hay_size;

if constexpr (_Special) {
if constexpr (_Is_implementation_handled_char_traits<_Traits>) {
if (!_STD _Is_constant_evaluated()) {
using _Elem = typename _Traits::char_type;

Expand Down Expand Up @@ -814,32 +814,33 @@ constexpr size_t _Traits_find_last_of(_In_reads_(_Hay_size) const _Traits_ptr_t<
return static_cast<size_t>(-1); // no match
}

template <class _Traits, bool _Special = _Is_implementation_handled_char_traits<_Traits>>
template <class _Traits>
constexpr size_t _Traits_find_first_not_of(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack,
const size_t _Hay_size, const size_t _Start_at, _In_reads_(_Needle_size) const _Traits_ptr_t<_Traits> _Needle,
const size_t _Needle_size) noexcept {
// in [_Haystack, _Haystack + _Hay_size), look for none of [_Needle, _Needle + _Needle_size), at/after _Start_at
if (_Start_at < _Hay_size) { // room for match, look for it
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if constexpr (_Special) {
_String_bitmap<typename _Traits::char_type> _Matches;
if (!_Matches._Mark(_Needle, _Needle + _Needle_size)) { // couldn't put one of the characters into the
// bitmap, fall back to the serial algorithm
return _Traits_find_first_not_of<_Traits, false>(
_Haystack, _Hay_size, _Start_at, _Needle, _Needle_size);
}
const auto _Hay_start = _Haystack + _Start_at;
const auto _Hay_end = _Haystack + _Hay_size;

const auto _End = _Haystack + _Hay_size;
for (auto _Match_try = _Haystack + _Start_at; _Match_try < _End; ++_Match_try) {
if (!_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
if constexpr (_Is_implementation_handled_char_traits<_Traits>) {
using _Elem = typename _Traits::char_type;
_String_bitmap<_Elem> _Matches;
if (_Matches._Mark(_Needle, _Needle + _Needle_size)) {
for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (!_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
}
return static_cast<size_t>(-1); // no match
}
} else {
const auto _End = _Haystack + _Hay_size;
for (auto _Match_try = _Haystack + _Start_at; _Match_try < _End; ++_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

// couldn't put one of the characters into the bitmap, fall back to the serial algorithm
}

for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
}
}
Expand All @@ -863,37 +864,39 @@ constexpr size_t _Traits_find_not_ch(_In_reads_(_Hay_size) const _Traits_ptr_t<_
return static_cast<size_t>(-1); // no match
}

template <class _Traits, bool _Special = _Is_implementation_handled_char_traits<_Traits>>
template <class _Traits>
constexpr size_t _Traits_find_last_not_of(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack,
const size_t _Hay_size, const size_t _Start_at, _In_reads_(_Needle_size) const _Traits_ptr_t<_Traits> _Needle,
const size_t _Needle_size) noexcept {
// in [_Haystack, _Haystack + _Hay_size), look for none of [_Needle, _Needle + _Needle_size), before _Start_at
if (_Hay_size != 0) { // worth searching, do it
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if constexpr (_Special) {
_String_bitmap<typename _Traits::char_type> _Matches;
if (!_Matches._Mark(_Needle, _Needle + _Needle_size)) { // couldn't put one of the characters into the
// bitmap, fall back to the serial algorithm
return _Traits_find_last_not_of<_Traits, false>(_Haystack, _Hay_size, _Start_at, _Needle, _Needle_size);
}
const auto _Hay_start = (_STD min)(_Start_at, _Hay_size - 1);

if constexpr (_Is_implementation_handled_char_traits<_Traits>) {
using _Elem = typename _Traits::char_type;
_String_bitmap<_Elem> _Matches;
if (_Matches._Mark(_Needle, _Needle + _Needle_size)) {
for (auto _Match_try = _Haystack + _Hay_start;; --_Match_try) {
if (!_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
if (!_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
if (_Match_try == _Haystack) {
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
}
// couldn't put one of the characters into the bitmap, fall back to the serial algorithm
}

for (auto _Match_try = _Haystack + _Hay_start;; --_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
} else {
for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
}
if (_Match_try == _Haystack) {
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}
}
Expand All @@ -912,7 +915,7 @@ constexpr size_t _Traits_rfind_not_ch(_In_reads_(_Hay_size) const _Traits_ptr_t<
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}
}
Expand Down
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