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78 lines
1.8 KiB
C++
78 lines
1.8 KiB
C++
/*
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* Copyright 2016-present Facebook, Inc.
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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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#pragma once
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#include <cstddef>
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#include <utility>
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#include <folly/lang/Align.h>
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namespace folly {
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/**
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* Holds a type T, in addition to enough padding to ensure that it isn't subject
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* to false sharing within the range used by folly.
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*
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* If `sizeof(T) <= alignof(T)` then the inner `T` will be entirely within one
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* false sharing range (AKA cache line).
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*/
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template <typename T>
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class CachelinePadded {
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static_assert(
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alignof(T) <= max_align_v,
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"CachelinePadded does not support over-aligned types.");
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public:
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template <typename... Args>
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explicit CachelinePadded(Args&&... args)
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: inner_(std::forward<Args>(args)...) {}
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T* get() {
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return &inner_;
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}
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const T* get() const {
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return &inner_;
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}
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T* operator->() {
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return get();
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}
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const T* operator->() const {
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return get();
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}
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T& operator*() {
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return *get();
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}
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const T& operator*() const {
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return *get();
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}
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private:
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static constexpr size_t paddingSize() noexcept {
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return hardware_destructive_interference_size -
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(alignof(T) % hardware_destructive_interference_size);
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}
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char paddingPre_[paddingSize()];
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T inner_;
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char paddingPost_[paddingSize()];
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};
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} // namespace folly
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