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#       1                 :            : // Copyright (c) 2018 The LevelDB Authors. All rights reserved.
#       2                 :            : // Use of this source code is governed by a BSD-style license that can be
#       3                 :            : // found in the LICENSE file. See the AUTHORS file for names of contributors.
#       4                 :            : 
#       5                 :            : #ifndef STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
#       6                 :            : #define STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
#       7                 :            : 
#       8                 :            : #include <type_traits>
#       9                 :            : #include <utility>
#      10                 :            : 
#      11                 :            : namespace leveldb {
#      12                 :            : 
#      13                 :            : // Wraps an instance whose destructor is never called.
#      14                 :            : //
#      15                 :            : // This is intended for use with function-level static variables.
#      16                 :            : template <typename InstanceType>
#      17                 :            : class NoDestructor {
#      18                 :            :  public:
#      19                 :            :   template <typename... ConstructorArgTypes>
#      20                 :        741 :   explicit NoDestructor(ConstructorArgTypes&&... constructor_args) {
#      21                 :        741 :     static_assert(sizeof(instance_storage_) >= sizeof(InstanceType),
#      22                 :        741 :                   "instance_storage_ is not large enough to hold the instance");
#      23                 :        741 :     static_assert(
#      24                 :        741 :         alignof(decltype(instance_storage_)) >= alignof(InstanceType),
#      25                 :        741 :         "instance_storage_ does not meet the instance's alignment requirement");
#      26                 :        741 :     new (&instance_storage_)
#      27                 :        741 :         InstanceType(std::forward<ConstructorArgTypes>(constructor_args)...);
#      28                 :        741 :   }
#      29                 :            : 
#      30                 :            :   ~NoDestructor() = default;
#      31                 :            : 
#      32                 :            :   NoDestructor(const NoDestructor&) = delete;
#      33                 :            :   NoDestructor& operator=(const NoDestructor&) = delete;
#      34                 :            : 
#      35                 :       8232 :   InstanceType* get() {
#      36                 :       8232 :     return reinterpret_cast<InstanceType*>(&instance_storage_);
#      37                 :       8232 :   }
#      38                 :            : 
#      39                 :            :  private:
#      40                 :            :   typename std::aligned_storage<sizeof(InstanceType),
#      41                 :            :                                 alignof(InstanceType)>::type instance_storage_;
#      42                 :            : };
#      43                 :            : 
#      44                 :            : }  // namespace leveldb
#      45                 :            : 
#      46                 :            : #endif  // STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_