libcxx/include/__algorithm/ranges_copy_n.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___ALGORITHM_RANGES_COPY_N_H
  10 #define _LIBCPP___ALGORITHM_RANGES_COPY_N_H
  11
  12 #include <__algorithm/copy.h>
  13 #include <__algorithm/in_out_result.h>
  14 #include <__algorithm/iterator_operations.h>
  15 #include <__algorithm/ranges_copy.h>
  16 #include <__config>
  17 #include <__functional/identity.h>
  18 #include <__iterator/concepts.h>
  19 #include <__iterator/incrementable_traits.h>
  20 #include <__iterator/unreachable_sentinel.h>
  21 #include <__iterator/wrap_iter.h>
  22 #include <__utility/move.h>
  23
  24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  25 #  pragma GCC system_header
  26 #endif
  27
  28 _LIBCPP_BEGIN_NAMESPACE_STD
  29
  30 #if _LIBCPP_STD_VER >= 20
  31
  32 namespace ranges {
  33
  34 template <class _Ip, class _Op>
  35 using copy_n_result = in_out_result<_Ip, _Op>;
  36
  37 namespace __copy_n {
  38 struct __fn {
  39   template <class _InIter, class _DiffType, class _OutIter>
  40   _LIBCPP_HIDE_FROM_ABI constexpr static copy_n_result<_InIter, _OutIter>
  41   __go(_InIter __first, _DiffType __n, _OutIter __result) {
  42     while (__n != 0) {
  43       *__result = *__first;
  44       ++__first;
  45       ++__result;
  46       --__n;
  47     }
  48     return {std::move(__first), std::move(__result)};
  49   }
  50
  51   template <random_access_iterator _InIter, class _DiffType, random_access_iterator _OutIter>
  52   _LIBCPP_HIDE_FROM_ABI constexpr static copy_n_result<_InIter, _OutIter>
  53   __go(_InIter __first, _DiffType __n, _OutIter __result) {
  54     auto __ret = std::__copy<_RangeAlgPolicy>(__first, __first + __n, __result);
  55     return {__ret.first, __ret.second};
  56   }
  57
  58   template <input_iterator _Ip, weakly_incrementable _Op>
  59     requires indirectly_copyable<_Ip, _Op>
  60   _LIBCPP_HIDE_FROM_ABI constexpr copy_n_result<_Ip, _Op>
  61   operator()(_Ip __first, iter_difference_t<_Ip> __n, _Op __result) const {
  62     return __go(std::move(__first), __n, std::move(__result));
  63   }
  64 };
  65 } // namespace __copy_n
  66
  67 inline namespace __cpo {
  68 inline constexpr auto copy_n = __copy_n::__fn{};
  69 } // namespace __cpo
  70 } // namespace ranges
  71
  72 #endif // _LIBCPP_STD_VER >= 20
  73
  74 _LIBCPP_END_NAMESPACE_STD
  75
  76 #endif // _LIBCPP___ALGORITHM_RANGES_COPY_N_H