88 lines
3.2 KiB
C++
88 lines
3.2 KiB
C++
// Copyright 2020 The Tint Authors.
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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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// http://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 SRC_TRAITS_H_
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#define SRC_TRAITS_H_
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#include <tuple>
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namespace tint {
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namespace traits {
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/// NthTypeOf returns the `N`th type in `Types`
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template <int N, typename... Types>
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using NthTypeOf = typename std::tuple_element<N, std::tuple<Types...>>::type;
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/// ParamType is a traits helper that infers the type of the `N`th parameter
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/// of the function, method, static method, lambda, or function-like object `F`.
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template <typename F, int N>
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struct ParamType {
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/// The type of the `N`th parameter of the function-like object `F`
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using type = typename ParamType<decltype(&F::operator()), N>::type;
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};
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/// ParamType specialization for a regular function or static method.
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template <typename R, int N, typename... Args>
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struct ParamType<R (*)(Args...), N> {
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/// Arg is the raw type of the `N`th parameter of the function
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using Arg = NthTypeOf<N, Args...>;
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/// The type of the `N`th parameter of the function
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using type = typename std::decay<Arg>::type;
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};
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/// ParamType specialization for a non-static method.
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template <typename R, typename C, int N, typename... Args>
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struct ParamType<R (C::*)(Args...), N> {
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/// Arg is the raw type of the `N`th parameter of the function
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using Arg = NthTypeOf<N, Args...>;
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/// The type of the `N`th parameter of the function
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using type = typename std::decay<Arg>::type;
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};
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/// ParamType specialization for a non-static, const method.
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template <typename R, typename C, int N, typename... Args>
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struct ParamType<R (C::*)(Args...) const, N> {
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/// Arg is the raw type of the `N`th parameter of the function
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using Arg = NthTypeOf<N, Args...>;
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/// The type of the `N`th parameter of the function
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using type = typename std::decay<Arg>::type;
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};
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/// ParamTypeT is an alias to `typename ParamType<F, N>::type`.
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template <typename F, int N>
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using ParamTypeT = typename ParamType<F, N>::type;
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/// `IsTypeOrDerived<T, BASE>::value` is true iff `T` is of type `BASE`, or
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/// derives from `BASE`.
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template <typename T, typename BASE>
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using IsTypeOrDerived = std::integral_constant<
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bool,
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std::is_base_of<BASE, typename std::decay<T>::type>::value ||
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std::is_same<BASE, typename std::decay<T>::type>::value>;
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/// If `CONDITION` is true then EnableIf resolves to type T, otherwise an
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/// invalid type.
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template <bool CONDITION, typename T>
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using EnableIf = typename std::enable_if<CONDITION, T>::type;
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/// If T is a base of BASE then EnableIfIsType resolves to type T, otherwise an
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/// invalid type.
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template <typename T, typename BASE>
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using EnableIfIsType = EnableIf<IsTypeOrDerived<T, BASE>::value, T>;
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} // namespace traits
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} // namespace tint
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#endif // SRC_TRAITS_H_
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