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- /*
- * Copyright 2016-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #pragma once
- #include <cstddef>
- #include <utility>
- #include <folly/lang/Align.h>
- namespace folly {
- /**
- * Holds a type T, in addition to enough padding to ensure that it isn't subject
- * to false sharing within the range used by folly.
- *
- * If `sizeof(T) <= alignof(T)` then the inner `T` will be entirely within one
- * false sharing range (AKA cache line).
- */
- template <typename T>
- class CachelinePadded {
- static_assert(
- alignof(T) <= max_align_v,
- "CachelinePadded does not support over-aligned types.");
- public:
- template <typename... Args>
- explicit CachelinePadded(Args&&... args)
- : inner_(std::forward<Args>(args)...) {}
- T* get() {
- return &inner_;
- }
- const T* get() const {
- return &inner_;
- }
- T* operator->() {
- return get();
- }
- const T* operator->() const {
- return get();
- }
- T& operator*() {
- return *get();
- }
- const T& operator*() const {
- return *get();
- }
- private:
- static constexpr size_t paddingSize() noexcept {
- return hardware_destructive_interference_size -
- (alignof(T) % hardware_destructive_interference_size);
- }
- char paddingPre_[paddingSize()];
- T inner_;
- char paddingPost_[paddingSize()];
- };
- } // namespace folly
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