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 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
26 typename enable_if
27 <
28     __has_input_iterator_category<_InputIterator>::value &&
29    !__has_random_access_iterator_category<_InputIterator>::value,
30     _OutputIterator
31 >::type
32 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
33 {
34     typedef decltype(_VSTD::__convert_to_integral(__orig_n)) _IntegralSize;
35     _IntegralSize __n = __orig_n;
36     if (__n > 0)
37     {
38         *__result = *__first;
39         ++__result;
40         for (--__n; __n > 0; --__n)
41         {
42             ++__first;
43             *__result = *__first;
44             ++__result;
45         }
46     }
47     return __result;
48 }
49 
50 template<class _InputIterator, class _Size, class _OutputIterator>
51 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
52 typename enable_if
53 <
54     __has_random_access_iterator_category<_InputIterator>::value,
55     _OutputIterator
56 >::type
57 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
58 {
59     typedef typename iterator_traits<_InputIterator>::difference_type difference_type;
60     typedef decltype(_VSTD::__convert_to_integral(__orig_n)) _IntegralSize;
61     _IntegralSize __n = __orig_n;
62     return _VSTD::copy(__first, __first + difference_type(__n), __result);
63 }
64 
65 _LIBCPP_END_NAMESPACE_STD
66 
67 #endif // _LIBCPP___ALGORITHM_COPY_N_H
68