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[libc++] Refactor for_each_n #150635

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91 changes: 33 additions & 58 deletions libcxx/include/__algorithm/for_each_n.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,15 +12,16 @@

#include <__algorithm/for_each.h>
#include <__algorithm/for_each_n_segment.h>
#include <__algorithm/min.h>
#include <__config>
#include <__cstddef/size_t.h>
#include <__functional/identity.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/segmented_iterator.h>
#include <__type_traits/disjunction.h>
#include <__type_traits/enable_if.h>
#include <__iterator/unreachable_sentinel.h>
#include <__type_traits/invoke.h>
#include <__type_traits/negation.h>
#include <__utility/convert_to_integral.h>
#include <__type_traits/is_same.h>
#include <__utility/exchange.h>
#include <__utility/move.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
Expand All @@ -30,73 +31,47 @@
_LIBCPP_PUSH_MACROS
#include <__undef_macros>

#if _LIBCPP_STD_VER >= 17

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _InputIterator,
class _Size,
class _Func,
class _Proj,
__enable_if_t<!__has_random_access_iterator_category<_InputIterator>::value &&
_Or<integral_constant<bool, !__is_segmented_iterator_v<_InputIterator> >,
_Not<__has_random_access_local_iterator<_InputIterator> > >::value,
int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _InputIterator
__for_each_n(_InputIterator __first, _Size __orig_n, _Func& __f, _Proj& __proj) {
typedef decltype(std::__convert_to_integral(__orig_n)) _IntegralSize;
_IntegralSize __n = __orig_n;
while (__n > 0) {
std::__invoke(__f, std::__invoke(__proj, *__first));
++__first;
--__n;
template <class _Iter, class _Sent, class _Size, class _Func, class _Proj>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter
__for_each_n(_Iter __first, _Sent __last, _Size& __n, _Func& __func, _Proj& __proj) {
if constexpr (__has_random_access_iterator_category<_Iter>::value) {
if constexpr (is_same_v<_Sent, __unreachable_sentinel_t>) {
return std::__for_each(__first, __first + std::exchange(__n, 0), __func, __proj);
} else {
auto __count = std::min<size_t>(__n, __last - __first);
__n -= __count;
return std::__for_each(__first, __first + __count, __func, __proj);
}
} else if constexpr (__is_segmented_iterator_v<_Iter>) {
return std::__for_each_n_segment(__first, __n, [&](auto __lfirst, auto __llast, _Size __max) {
std::__for_each_n(__lfirst, __llast, __max, __func, __proj);
return __max;
});
} else {
while (__n > 0 && __first != __last) {
std::__invoke(__func, std::__invoke(__proj, *__first));
++__first;
--__n;
}
return std::move(__first);
}
return std::move(__first);
}

template <class _RandIter,
class _Size,
class _Func,
class _Proj,
__enable_if_t<__has_random_access_iterator_category<_RandIter>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _RandIter
__for_each_n(_RandIter __first, _Size __orig_n, _Func& __f, _Proj& __proj) {
typename std::iterator_traits<_RandIter>::difference_type __n = __orig_n;
auto __last = __first + __n;
std::__for_each(__first, __last, __f, __proj);
return __last;
}

#ifndef _LIBCPP_CXX03_LANG
template <class _SegmentedIterator,
class _Size,
class _Func,
class _Proj,
__enable_if_t<!__has_random_access_iterator_category<_SegmentedIterator>::value &&
__is_segmented_iterator_v<_SegmentedIterator> &&
__has_random_access_iterator_category<
typename __segmented_iterator_traits<_SegmentedIterator>::__local_iterator>::value,
int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _SegmentedIterator
__for_each_n(_SegmentedIterator __first, _Size __orig_n, _Func& __f, _Proj& __proj) {
using __local_iterator_t = typename __segmented_iterator_traits<_SegmentedIterator>::__local_iterator;
return std::__for_each_n_segment(__first, __orig_n, [&](__local_iterator_t __lfirst, __local_iterator_t __llast) {
std::__for_each(__lfirst, __llast, __f, __proj);
});
}
#endif // !_LIBCPP_CXX03_LANG

#if _LIBCPP_STD_VER >= 17

template <class _InputIterator, class _Size, class _Func>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _InputIterator
for_each_n(_InputIterator __first, _Size __orig_n, _Func __f) {
__identity __proj;
return std::__for_each_n(__first, __orig_n, __f, __proj);
return std::__for_each_n(__first, __unreachable_sentinel, __orig_n, __f, __proj);
}

#endif // _LIBCPP_STD_VER >= 17

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_STD_VER >= 17

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_FOR_EACH_N_H
24 changes: 8 additions & 16 deletions libcxx/include/__algorithm/for_each_n_segment.h
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Original file line number Diff line number Diff line change
Expand Up @@ -26,36 +26,28 @@ _LIBCPP_BEGIN_NAMESPACE_STD

template <class _SegmentedIterator, class _Size, class _Functor>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator
__for_each_n_segment(_SegmentedIterator __first, _Size __orig_n, _Functor __func) {
__for_each_n_segment(_SegmentedIterator __first, _Size __n, _Functor __func) {
static_assert(__is_segmented_iterator_v<_SegmentedIterator> &&
__has_random_access_iterator_category<
typename __segmented_iterator_traits<_SegmentedIterator>::__local_iterator>::value,
"__for_each_n_segment only works with segmented iterators with random-access local iterators");
if (__orig_n <= 0)
if (__n <= 0)
return __first;

using _Traits = __segmented_iterator_traits<_SegmentedIterator>;
using __local_iter_t = typename _Traits::__local_iterator;
using __difference_t = typename std::iterator_traits<__local_iter_t>::difference_type;
__difference_t __n = __orig_n;
auto __seg = _Traits::__segment(__first);
auto __segment_iter = _Traits::__segment(__first);
auto __local_first = _Traits::__local(__first);
__local_iter_t __local_last;

__n = __func(_Traits::__local(__first), _Traits::__end(__segment_iter), __n);

while (__n > 0) {
__local_last = _Traits::__end(__seg);
auto __seg_size = __local_last - __local_first;
if (__n <= __seg_size) {
__local_last = __local_first + __n;
__func(__local_first, __local_last);
break;
}
__func(__local_first, __local_last);
__n -= __seg_size;
__local_first = _Traits::__begin(++__seg);
++__segment_iter;
__n = __func(_Traits::__begin(__segment_iter), _Traits::__end(__segment_iter), __n);
}

return _Traits::__compose(__seg, __local_last);
return _Traits::__compose(__segment_iter, __local_last);
}

_LIBCPP_END_NAMESPACE_STD
Expand Down
5 changes: 2 additions & 3 deletions libcxx/include/__algorithm/ranges_for_each_n.h
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Original file line number Diff line number Diff line change
Expand Up @@ -15,9 +15,8 @@
#include <__functional/identity.h>
#include <__iterator/concepts.h>
#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/projected.h>
#include <__ranges/concepts.h>
#include <__iterator/unreachable_sentinel.h>
#include <__utility/move.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
Expand All @@ -40,7 +39,7 @@ struct __for_each_n {
template <input_iterator _Iter, class _Proj = identity, indirectly_unary_invocable<projected<_Iter, _Proj>> _Func>
_LIBCPP_HIDE_FROM_ABI constexpr for_each_n_result<_Iter, _Func>
operator()(_Iter __first, iter_difference_t<_Iter> __count, _Func __func, _Proj __proj = {}) const {
auto __last = std::__for_each_n(std::move(__first), __count, __func, __proj);
auto __last = std::__for_each_n(std::move(__first), __unreachable_sentinel, __count, __func, __proj);
return {std::move(__last), std::move(__func)};
}
};
Expand Down
5 changes: 0 additions & 5 deletions libcxx/include/__iterator/segmented_iterator.h
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Original file line number Diff line number Diff line change
Expand Up @@ -75,11 +75,6 @@ inline const bool __has_specialization_v<_Tp, sizeof(_Tp) * 0> = true;
template <class _Iterator>
inline const bool __is_segmented_iterator_v = __has_specialization_v<__segmented_iterator_traits<_Iterator> >;

template <class _SegmentedIterator>
struct __has_random_access_local_iterator
: __has_random_access_iterator_category<
typename __segmented_iterator_traits< _SegmentedIterator >::__local_iterator > {};

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___SEGMENTED_ITERATOR_H
33 changes: 33 additions & 0 deletions libcxx/include/__iterator/unreachable_sentinel.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,13 +12,46 @@

#include <__config>
#include <__iterator/concepts.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/is_same.h>
#include <__type_traits/remove_cvref.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

inline constexpr struct __unreachable_sentinel_t {} __unreachable_sentinel;

template <class _UnreachableSentinel,
class _Iter,
__enable_if_t<is_same<__remove_cvref_t<_UnreachableSentinel>, __unreachable_sentinel_t>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr bool operator==(_UnreachableSentinel&&, _Iter&&) {
return false;
}

template <class _UnreachableSentinel,
class _Iter,
__enable_if_t<is_same<__remove_cvref_t<_UnreachableSentinel>, __unreachable_sentinel_t>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr bool operator==(_Iter&&, _UnreachableSentinel&&) {
return false;
}

template <class _UnreachableSentinel,
class _Iter,
__enable_if_t<is_same<__remove_cvref_t<_UnreachableSentinel>, __unreachable_sentinel_t>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr bool operator!=(_UnreachableSentinel&&, _Iter&&) {
return true;
}

template <class _UnreachableSentinel,
class _Iter,
__enable_if_t<is_same<__remove_cvref_t<_UnreachableSentinel>, __unreachable_sentinel_t>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr bool operator!=(_Iter&&, _UnreachableSentinel&&) {
return true;
}

#if _LIBCPP_STD_VER >= 20

struct unreachable_sentinel_t {
Expand Down
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