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Fewer allocations to put smaller bitset to stream #4818

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merged 6 commits into from
Jul 11, 2024
Merged

Fewer allocations to put smaller bitset to stream #4818

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044e579
Fewer allocations to put smaller bitset to stream
AlexGuteniev Jul 7, 2024
a2f068f
fix all bugs
AlexGuteniev Jul 7, 2024
7b7d742
define reservation
AlexGuteniev Jul 7, 2024
d153c3a
missing return
AlexGuteniev Jul 7, 2024
5934ad5
typo
AlexGuteniev Jul 7, 2024
d6613ef
`_Elem` doesn't need a default argument.
StephanTLavavej Jul 8, 2024
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60 changes: 39 additions & 21 deletions stl/inc/bitset
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,10 @@ _STL_DISABLE_CLANG_WARNINGS
#pragma push_macro("new")
#undef new

#ifndef _STD_BITSET_TO_STREAM_STACK_RESERVATION
#define _STD_BITSET_TO_STREAM_STACK_RESERVATION 128
#endif // !defined(_STD_BITSET_TO_STREAM_STACK_RESERVATION)

#if _USE_STD_VECTOR_ALGORITHMS
extern "C" {
__declspec(noalias) void __stdcall __std_bitset_to_string_1(
Expand Down Expand Up @@ -357,26 +361,7 @@ public:
// convert bitset to string
basic_string<_Elem, _Tr, _Alloc> _Str;
_Str._Resize_and_overwrite(_Bits, [this, _Elem0, _Elem1](_Elem* _Buf, size_t _Len) {
#if _USE_STD_VECTOR_ALGORITHMS
constexpr size_t _Bitset_vector_threshold = 32;
if constexpr (_Bits >= _Bitset_vector_threshold && is_integral_v<_Elem> && sizeof(_Elem) <= 2) {
if (!_Is_constant_evaluated()) {
if constexpr (sizeof(_Elem) == 1) {
__std_bitset_to_string_1(reinterpret_cast<char*>(_Buf), _Array, _Len, static_cast<char>(_Elem0),
static_cast<char>(_Elem1));
} else {
_STL_INTERNAL_STATIC_ASSERT(sizeof(_Elem) == 2);
__std_bitset_to_string_2(reinterpret_cast<wchar_t*>(_Buf), _Array, _Len,
static_cast<wchar_t>(_Elem0), static_cast<wchar_t>(_Elem1));
}
return _Len;
}
}
#endif // _USE_STD_VECTOR_ALGORITHMS

for (size_t _Pos = 0; _Pos < _Len; ++_Pos) {
_Buf[_Pos] = _Subscript(_Len - 1 - _Pos) ? _Elem1 : _Elem0;
}
_To_string(_Buf, _Len, _Elem0, _Elem1);
return _Len;
});
return _Str;
Expand Down Expand Up @@ -473,6 +458,32 @@ public:
return _Array[_Wpos];
}

template <class _Elem>
_CONSTEXPR23 void _To_string(
_Elem* const _Buf, const size_t _Len, const _Elem _Elem0, const _Elem _Elem1) const noexcept {
#if _USE_STD_VECTOR_ALGORITHMS
constexpr size_t _Bitset_vector_threshold = 32;
if constexpr (_Bits >= _Bitset_vector_threshold && is_integral_v<_Elem> && sizeof(_Elem) <= 2) {
if (!_Is_constant_evaluated()) {
if constexpr (sizeof(_Elem) == 1) {
__std_bitset_to_string_1(reinterpret_cast<char*>(_Buf), _Array, _Len, static_cast<char>(_Elem0),
static_cast<char>(_Elem1));
} else {
_STL_INTERNAL_STATIC_ASSERT(sizeof(_Elem) == 2);
__std_bitset_to_string_2(reinterpret_cast<wchar_t*>(_Buf), _Array, _Len,
static_cast<wchar_t>(_Elem0), static_cast<wchar_t>(_Elem1));
}

return;
}
}
#endif // _USE_STD_VECTOR_ALGORITHMS

for (size_t _Pos = 0; _Pos < _Len; ++_Pos) {
_Buf[_Pos] = _Subscript(_Len - 1 - _Pos) ? _Elem1 : _Elem0;
}
}

private:
friend hash<bitset<_Bits>>;

Expand Down Expand Up @@ -547,7 +558,14 @@ basic_ostream<_Elem, _Tr>& operator<<(basic_ostream<_Elem, _Tr>& _Ostr, const bi
const _Elem _Elem0 = _Ctype_fac.widen('0');
const _Elem _Elem1 = _Ctype_fac.widen('1');

return _Ostr << _Right.template to_string<_Elem, _Tr, allocator<_Elem>>(_Elem0, _Elem1);
if constexpr (_Bits * sizeof(_Elem) <= _STD_BITSET_TO_STREAM_STACK_RESERVATION) {
_Elem _Buf[_Bits + 1];
_Right._To_string(_Buf, _Bits, _Elem0, _Elem1);
_Buf[_Bits] = _Elem{'\0'};
return _Ostr << _Buf;
} else {
return _Ostr << _Right.template to_string<_Elem, _Tr, allocator<_Elem>>(_Elem0, _Elem1);
}
}

_EXPORT_STD template <class _Elem, class _Tr, size_t _Bits>
Expand Down