xref: /freebsd/contrib/llvm-project/libcxx/include/__ranges/empty_view.h (revision 86dc8398c9ca2283c5d6984992b7a585257b5adb)
1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 #ifndef _LIBCPP___RANGES_EMPTY_VIEW_H
10 #define _LIBCPP___RANGES_EMPTY_VIEW_H
11 
12 #include <__config>
13 #include <__ranges/view_interface.h>
14 #include <type_traits>
15 
16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17 #pragma GCC system_header
18 #endif
19 
20 _LIBCPP_PUSH_MACROS
21 #include <__undef_macros>
22 
23 _LIBCPP_BEGIN_NAMESPACE_STD
24 
25 #if !defined(_LIBCPP_HAS_NO_RANGES)
26 
27 namespace ranges {
28   template<class _Tp>
29     requires is_object_v<_Tp>
30   class empty_view : public view_interface<empty_view<_Tp>> {
31   public:
32     _LIBCPP_HIDE_FROM_ABI static constexpr _Tp* begin() noexcept { return nullptr; }
33     _LIBCPP_HIDE_FROM_ABI static constexpr _Tp* end() noexcept { return nullptr; }
34     _LIBCPP_HIDE_FROM_ABI static constexpr _Tp* data() noexcept { return nullptr; }
35     _LIBCPP_HIDE_FROM_ABI static constexpr size_t size() noexcept { return 0; }
36     _LIBCPP_HIDE_FROM_ABI static constexpr bool empty() noexcept { return true; }
37   };
38 } // namespace ranges
39 
40 #endif // !defined(_LIBCPP_HAS_NO_RANGES)
41 
42 _LIBCPP_END_NAMESPACE_STD
43 
44 _LIBCPP_POP_MACROS
45 
46 #endif // _LIBCPP___RANGES_EMPTY_VIEW_H
47