Jim Flynn | 6217c3d | 2022-06-14 10:58:23 +0100 | [diff] [blame] | 1 | // |
| 2 | // Copyright (c) MapBox All rights reserved. |
| 3 | // SPDX-License-Identifier: BSD-3-Clause |
| 4 | // |
| 5 | |
James Ward | 22a4e15 | 2020-09-25 11:43:21 +0100 | [diff] [blame] | 6 | #ifndef VARIANT_CAST_HPP |
| 7 | #define VARIANT_CAST_HPP |
| 8 | |
| 9 | #include <type_traits> |
| 10 | |
| 11 | namespace mapbox { |
| 12 | namespace util { |
| 13 | |
| 14 | namespace detail { |
| 15 | |
| 16 | template <class T> |
| 17 | class static_caster |
| 18 | { |
| 19 | public: |
| 20 | template <class V> |
| 21 | T& operator()(V& v) const |
| 22 | { |
| 23 | return static_cast<T&>(v); |
| 24 | } |
| 25 | }; |
| 26 | |
| 27 | template <class T> |
| 28 | class dynamic_caster |
| 29 | { |
| 30 | public: |
| 31 | using result_type = T&; |
| 32 | template <class V> |
| 33 | T& operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const |
| 34 | { |
| 35 | throw std::bad_cast(); |
| 36 | } |
| 37 | template <class V> |
| 38 | T& operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const |
| 39 | { |
| 40 | return dynamic_cast<T&>(v); |
| 41 | } |
| 42 | }; |
| 43 | |
| 44 | template <class T> |
| 45 | class dynamic_caster<T*> |
| 46 | { |
| 47 | public: |
| 48 | using result_type = T*; |
| 49 | template <class V> |
| 50 | T* operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const |
| 51 | { |
| 52 | return nullptr; |
| 53 | } |
| 54 | template <class V> |
| 55 | T* operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const |
| 56 | { |
| 57 | return dynamic_cast<T*>(&v); |
| 58 | } |
| 59 | }; |
| 60 | } |
| 61 | |
| 62 | template <class T, class V> |
| 63 | typename detail::dynamic_caster<T>::result_type |
| 64 | dynamic_variant_cast(V& v) |
| 65 | { |
| 66 | return mapbox::util::apply_visitor(detail::dynamic_caster<T>(), v); |
| 67 | } |
| 68 | |
| 69 | template <class T, class V> |
| 70 | typename detail::dynamic_caster<const T>::result_type |
| 71 | dynamic_variant_cast(const V& v) |
| 72 | { |
| 73 | return mapbox::util::apply_visitor(detail::dynamic_caster<const T>(), v); |
| 74 | } |
| 75 | |
| 76 | template <class T, class V> |
| 77 | T& static_variant_cast(V& v) |
| 78 | { |
| 79 | return mapbox::util::apply_visitor(detail::static_caster<T>(), v); |
| 80 | } |
| 81 | |
| 82 | template <class T, class V> |
| 83 | const T& static_variant_cast(const V& v) |
| 84 | { |
| 85 | return mapbox::util::apply_visitor(detail::static_caster<const T>(), v); |
| 86 | } |
| 87 | } |
| 88 | } |
| 89 | |
| 90 | #endif // VARIANT_CAST_HPP |