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67 lines
2.2 KiB
67 lines
2.2 KiB
4 months ago
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/*
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* Copyright 2014 Google Inc. All rights reserved.
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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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*/
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#ifndef FRUIT_LAMBDA_INVOKER_H
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#define FRUIT_LAMBDA_INVOKER_H
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#include <fruit/impl/fruit-config.h>
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#include <fruit/impl/injection_errors.h>
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#include <fruit/impl/meta/errors.h>
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#include <fruit/impl/meta/metaprogramming.h>
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#include <fruit/impl/meta/signatures.h>
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#include <fruit/impl/meta/wrappers.h>
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#include <cstddef>
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#include <functional>
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#include <type_traits>
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namespace fruit {
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namespace impl {
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template <typename T>
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struct SafeAlignmentOf {
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constexpr static const std::size_t value = alignof(T);
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};
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template <typename T, typename... Args>
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struct SafeAlignmentOf<T(Args...)> {
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constexpr static const std::size_t value = alignof(int);
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};
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class LambdaInvoker {
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public:
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template <typename F, typename... Args>
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FRUIT_ALWAYS_INLINE static auto invoke(Args&&... args)
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-> decltype(std::declval<const F&>()(std::declval<Args>()...)) {
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// We reinterpret-cast a char[] to avoid de-referencing nullptr, which would technically be
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// undefined behavior (even though we would not access any data there anyway).
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// Sharing this buffer for different types F would also be undefined behavior since we'd break
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// strict aliasing between those types.
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alignas(SafeAlignmentOf<F>::value) static char buf[1];
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FruitStaticAssert(fruit::impl::meta::IsEmpty(fruit::impl::meta::Type<F>));
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FruitStaticAssert(fruit::impl::meta::IsTriviallyCopyable(fruit::impl::meta::Type<F>));
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// Since `F' is empty, a valid value of type F is already stored at the beginning of buf.
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F* f = reinterpret_cast<F*>((char*)buf);
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return (*f)(std::forward<Args>(args)...);
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}
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};
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} // namespace impl
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} // namespace fruit
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#endif // FRUIT_LAMBDA_INVOKER_H
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