libcxx/include/__algorithm/for_each_n.h

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___ALGORITHM_FOR_EACH_N_H
#define _LIBCPP___ALGORITHM_FOR_EACH_N_H

#include <__algorithm/for_each.h>
#include <__algorithm/for_each_n_segment.h>
#include <__config>
#include <__functional/identity.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/segmented_iterator.h>
#include <__type_traits/invoke.h>
#include <__utility/convert_to_integral.h>
#include <__utility/forward.h>
#include <__utility/move.h>

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

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _InputIterator, class _Size, class _Func, class _Proj>
_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;

#ifndef _LIBCPP_CXX03_LANG
  if constexpr (__is_segmented_iterator_v<_InputIterator>) {
    using __local_iterator = typename __segmented_iterator_traits<_InputIterator>::__local_iterator;
    if constexpr (__has_random_access_iterator_category<__local_iterator>::value) {
      return std::__for_each_n_segment(__first, __orig_n, [&](__local_iterator __lfirst, __local_iterator __llast) {
        std::__for_each(__lfirst, __llast, __f, __proj);
      });
    } else {
      return std::__for_each(__first, __first + __n, std::forward<_Func>(__f), __proj);
    }
  } else
#endif
  {
    while (__n > 0) {
      std::__invoke(__f, std::__invoke(__proj, *__first));
      ++__first;
      --__n;
    }
    return std::move(__first);
  }
}

#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);
}

#endif // _LIBCPP_STD_VER >= 17

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_FOR_EACH_N_H