openPMD-api
Variant.hpp
1 /* Copyright 2017-2020 Fabian Koller
2  *
3  * This file is part of openPMD-api.
4  *
5  * openPMD-api is free software: you can redistribute it and/or modify
6  * it under the terms of of either the GNU General Public License or
7  * the GNU Lesser General Public License as published by
8  * the Free Software Foundation, either version 3 of the License, or
9  * (at your option) any later version.
10  *
11  * openPMD-api is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU General Public License and the GNU Lesser General Public License
15  * for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * and the GNU Lesser General Public License along with openPMD-api.
19  * If not, see <http://www.gnu.org/licenses/>.
20  */
21 #pragma once
22 
23 #if __cplusplus >= 201703L
24 # include <variant> // IWYU pragma: export
25 namespace variantSrc = std;
26 #else
27 # include <mpark/variant.hpp> // IWYU pragma: export
28 namespace variantSrc = mpark;
29 #endif
30 
31 #include <type_traits>
32 
33 
34 namespace openPMD
35 {
36 namespace auxiliary
37 {
43 template< class T_DTYPES, typename ... T >
44 class Variant
45 {
46  static_assert(std::is_enum< T_DTYPES >::value, "Datatypes to Variant must be supplied as enum.");
47 
48 public:
49  using resource = variantSrc::variant< T ... >;
57  Variant(resource r)
58  : dtype{static_cast<T_DTYPES>(r.index())},
59  m_data{r}
60  { }
61 
68  template< typename U >
69  U get() const
70  {
71  return variantSrc::get< U >(m_data);
72  }
73 
78  resource getResource() const
79  {
80  return m_data;
81  }
82 
87  constexpr size_t index() const noexcept
88  {
89  return m_data.index();
90  }
91 
92  T_DTYPES dtype;
93 
94 private:
95  resource m_data;
96 };
97 } // auxiliary
98 } // openPMD
Variant(resource r)
Construct a lightweight wrapper around a generic object that indicates the concrete datatype of the s...
Definition: Variant.hpp:57
STL namespace.
Generic object to store a set of datatypes in without losing type safety.
Definition: Variant.hpp:44
constexpr size_t index() const noexcept
Retrieve the index of the alternative that is currently been held.
Definition: Variant.hpp:87
Public definitions of openPMD-api.
Definition: Date.cpp:28
resource getResource() const
Retrieve the stored generic object.
Definition: Variant.hpp:78