verdnatura-chat/ios/Pods/Folly/folly/CachelinePadded.h

83 lines
2.1 KiB
C++

/*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* 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 <cstdint>
#include <utility>
#include <folly/lang/Align.h>
#include <folly/lang/SafeAssert.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).
*
* CachelinePadded may add padding both before and after the value. Consider
* whether alignas(folly::hardware_destructive_interference_size) suffices.
*/
template <typename T>
class CachelinePadded {
public:
template <typename... Args>
explicit CachelinePadded(Args&&... args)
: inner_(std::forward<Args>(args)...) {
FOLLY_SAFE_DCHECK(
(reinterpret_cast<uintptr_t>(&inner_) % alignof(T)) == 0,
"CachelinePadded requires types aligned to their ABI requirement");
}
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