您最多选择25个主题
主题必须以字母或数字开头，可以包含连字符 (-)，并且长度不得超过35个字符
46 行
1.5 KiB
46 行
1.5 KiB
// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#ifndef STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
|
|
#define STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
|
|
|
|
#include <type_traits>
|
|
#include <utility>
|
|
|
|
namespace leveldb {
|
|
|
|
// Wraps an instance whose destructor is never called.
|
|
//
|
|
// This is intended for use with function-level static variables.
|
|
template <typename InstanceType>
|
|
class NoDestructor {
|
|
public:
|
|
template <typename... ConstructorArgTypes>
|
|
explicit NoDestructor(ConstructorArgTypes&&... constructor_args) {
|
|
static_assert(sizeof(instance_storage_) >= sizeof(InstanceType),
|
|
"instance_storage_ is not large enough to hold the instance");
|
|
static_assert(
|
|
alignof(decltype(instance_storage_)) >= alignof(InstanceType),
|
|
"instance_storage_ does not meet the instance's alignment requirement");
|
|
new (&instance_storage_)
|
|
InstanceType(std::forward<ConstructorArgTypes>(constructor_args)...);
|
|
}
|
|
|
|
~NoDestructor() = default;
|
|
|
|
NoDestructor(const NoDestructor&) = delete;
|
|
NoDestructor& operator=(const NoDestructor&) = delete;
|
|
|
|
InstanceType* get() {
|
|
return reinterpret_cast<InstanceType*>(&instance_storage_);
|
|
}
|
|
|
|
private:
|
|
typename std::aligned_storage<sizeof(InstanceType),
|
|
alignof(InstanceType)>::type instance_storage_;
|
|
};
|
|
|
|
} // namespace leveldb
|
|
|
|
#endif // STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
|