libcxx/include/__algorithm/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_COPY_N_H
  10 #define _LIBCPP___ALGORITHM_COPY_N_H
  11
  12 #include <__algorithm/copy.h>
  13 #include <__config>
  14 #include <__iterator/iterator_traits.h>
  15 #include <__type_traits/enable_if.h>
  16 #include <__utility/convert_to_integral.h>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #  pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_BEGIN_NAMESPACE_STD
  23
  24 template <class _InputIterator,
  25           class _Size,
  26           class _OutputIterator,
  27           __enable_if_t<__has_input_iterator_category<_InputIterator>::value &&
  28                             !__has_random_access_iterator_category<_InputIterator>::value,
  29                         int> = 0>
  30 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
  31 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result) {
  32   typedef decltype(std::__convert_to_integral(__orig_n)) _IntegralSize;
  33   _IntegralSize __n = __orig_n;
  34   if (__n > 0) {
  35     *__result = *__first;
  36     ++__result;
  37     for (--__n; __n > 0; --__n) {
  38       ++__first;
  39       *__result = *__first;
  40       ++__result;
  41     }
  42   }
  43   return __result;
  44 }
  45
  46 template <class _InputIterator,
  47           class _Size,
  48           class _OutputIterator,
  49           __enable_if_t<__has_random_access_iterator_category<_InputIterator>::value, int> = 0>
  50 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
  51 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result) {
  52   typedef typename iterator_traits<_InputIterator>::difference_type difference_type;
  53   typedef decltype(std::__convert_to_integral(__orig_n)) _IntegralSize;
  54   _IntegralSize __n = __orig_n;
  55   return std::copy(__first, __first + difference_type(__n), __result);
  56 }
  57
  58 _LIBCPP_END_NAMESPACE_STD
  59
  60 #endif // _LIBCPP___ALGORITHM_COPY_N_H