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, class _Size, class _OutputIterator,
  25          __enable_if_t<__has_input_iterator_category<_InputIterator>::value &&
  26                        !__has_random_access_iterator_category<_InputIterator>::value, int> = 0>
  27 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
  28 _OutputIterator
  29 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
  30 {
  31     typedef decltype(_VSTD::__convert_to_integral(__orig_n)) _IntegralSize;
  32     _IntegralSize __n = __orig_n;
  33     if (__n > 0)
  34     {
  35         *__result = *__first;
  36         ++__result;
  37         for (--__n; __n > 0; --__n)
  38         {
  39             ++__first;
  40             *__result = *__first;
  41             ++__result;
  42         }
  43     }
  44     return __result;
  45 }
  46
  47 template<class _InputIterator, class _Size, class _OutputIterator,
  48          __enable_if_t<__has_random_access_iterator_category<_InputIterator>::value, int> = 0>
  49 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
  50 _OutputIterator
  51 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
  52 {
  53     typedef typename iterator_traits<_InputIterator>::difference_type difference_type;
  54     typedef decltype(_VSTD::__convert_to_integral(__orig_n)) _IntegralSize;
  55     _IntegralSize __n = __orig_n;
  56     return _VSTD::copy(__first, __first + difference_type(__n), __result);
  57 }
  58
  59 _LIBCPP_END_NAMESPACE_STD
  60
  61 #endif // _LIBCPP___ALGORITHM_COPY_N_H