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109 lines
3.0 KiB
109 lines
3.0 KiB
2 years ago
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// Copyright 2019 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef dap_variant_h
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#define dap_variant_h
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#include "any.h"
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namespace dap {
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// internal functionality
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namespace detail {
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template <typename T, typename...>
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struct TypeIsIn {
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static constexpr bool value = false;
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};
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template <typename T, typename List0, typename... ListN>
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struct TypeIsIn<T, List0, ListN...> {
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static constexpr bool value =
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std::is_same<T, List0>::value || TypeIsIn<T, ListN...>::value;
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};
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} // namespace detail
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// variant represents a type-safe union of DAP types.
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// variant can hold a value of any of the template argument types.
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// variant defaults to a default-constructed T0.
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template <typename T0, typename... Types>
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class variant {
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public:
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// constructors
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inline variant();
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template <typename T>
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inline variant(const T& val);
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// assignment
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template <typename T>
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inline variant& operator=(const T& val);
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// get() returns the contained value of the type T.
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// If the any does not contain a value of type T, then get() will assert.
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template <typename T>
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inline T& get() const;
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// is() returns true iff the contained value is of type T.
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template <typename T>
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inline bool is() const;
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// accepts() returns true iff the variant accepts values of type T.
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template <typename T>
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static constexpr bool accepts();
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private:
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friend class Serializer;
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friend class Deserializer;
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any value;
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};
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template <typename T0, typename... Types>
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variant<T0, Types...>::variant() : value(T0()) {}
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template <typename T0, typename... Types>
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template <typename T>
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variant<T0, Types...>::variant(const T& v) : value(v) {
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static_assert(accepts<T>(), "variant does not accept template type T");
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}
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template <typename T0, typename... Types>
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template <typename T>
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variant<T0, Types...>& variant<T0, Types...>::operator=(const T& v) {
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static_assert(accepts<T>(), "variant does not accept template type T");
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value = v;
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return *this;
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}
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template <typename T0, typename... Types>
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template <typename T>
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T& variant<T0, Types...>::get() const {
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static_assert(accepts<T>(), "variant does not accept template type T");
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return value.get<T>();
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}
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template <typename T0, typename... Types>
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template <typename T>
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bool variant<T0, Types...>::is() const {
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return value.is<T>();
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}
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template <typename T0, typename... Types>
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template <typename T>
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constexpr bool variant<T0, Types...>::accepts() {
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return detail::TypeIsIn<T, T0, Types...>::value;
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}
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} // namespace dap
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#endif // dap_variant_h
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