101 lines
2.7 KiB
C++
101 lines
2.7 KiB
C++
// Copyright 2021 The Abseil 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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// 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 ABSL_CLEANUP_INTERNAL_CLEANUP_H_
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#define ABSL_CLEANUP_INTERNAL_CLEANUP_H_
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#include <new>
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#include <type_traits>
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#include <utility>
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#include "absl/base/internal/invoke.h"
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#include "absl/base/macros.h"
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#include "absl/base/thread_annotations.h"
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#include "absl/utility/utility.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace cleanup_internal {
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struct Tag {};
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template <typename Arg, typename... Args>
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constexpr bool WasDeduced() {
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return (std::is_same<cleanup_internal::Tag, Arg>::value) &&
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(sizeof...(Args) == 0);
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}
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template <typename Callback>
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constexpr bool ReturnsVoid() {
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return (std::is_same<base_internal::invoke_result_t<Callback>, void>::value);
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}
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template <typename Callback>
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class Storage {
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public:
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Storage() = delete;
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explicit Storage(Callback callback) {
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// Placement-new into a character buffer is used for eager destruction when
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// the cleanup is invoked or cancelled. To ensure this optimizes well, the
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// behavior is implemented locally instead of using an absl::optional.
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::new (GetCallbackBuffer()) Callback(std::move(callback));
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is_callback_engaged_ = true;
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}
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Storage(Storage&& other) {
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ABSL_HARDENING_ASSERT(other.IsCallbackEngaged());
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::new (GetCallbackBuffer()) Callback(std::move(other.GetCallback()));
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is_callback_engaged_ = true;
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other.DestroyCallback();
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}
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Storage(const Storage& other) = delete;
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Storage& operator=(Storage&& other) = delete;
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Storage& operator=(const Storage& other) = delete;
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void* GetCallbackBuffer() { return static_cast<void*>(+callback_buffer_); }
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Callback& GetCallback() {
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return *reinterpret_cast<Callback*>(GetCallbackBuffer());
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}
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bool IsCallbackEngaged() const { return is_callback_engaged_; }
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void DestroyCallback() {
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is_callback_engaged_ = false;
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GetCallback().~Callback();
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}
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void InvokeCallback() ABSL_NO_THREAD_SAFETY_ANALYSIS {
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std::move(GetCallback())();
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}
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private:
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bool is_callback_engaged_;
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alignas(Callback) char callback_buffer_[sizeof(Callback)];
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};
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} // namespace cleanup_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_CLEANUP_INTERNAL_CLEANUP_H_
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