| /* |
| * |
| * Copyright 2016 gRPC authors. |
| * |
| * 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. |
| * |
| */ |
| |
| #ifndef GRPC_CORE_LIB_SUPPORT_MANUAL_CONSTRUCTOR_H |
| #define GRPC_CORE_LIB_SUPPORT_MANUAL_CONSTRUCTOR_H |
| |
| // manually construct a region of memory with some type |
| |
| #include <stddef.h> |
| #include <new> |
| #include <type_traits> |
| #include <utility> |
| |
| namespace grpc_core { |
| |
| template <typename Type> |
| class ManualConstructor { |
| public: |
| // No constructor or destructor because one of the most useful uses of |
| // this class is as part of a union, and members of a union could not have |
| // constructors or destructors till C++11. And, anyway, the whole point of |
| // this class is to bypass constructor and destructor. |
| |
| Type* get() { return reinterpret_cast<Type*>(&space_); } |
| const Type* get() const { return reinterpret_cast<const Type*>(&space_); } |
| |
| Type* operator->() { return get(); } |
| const Type* operator->() const { return get(); } |
| |
| Type& operator*() { return *get(); } |
| const Type& operator*() const { return *get(); } |
| |
| void Init() { new (&space_) Type; } |
| |
| // Init() constructs the Type instance using the given arguments |
| // (which are forwarded to Type's constructor). |
| // |
| // Note that Init() with no arguments performs default-initialization, |
| // not zero-initialization (i.e it behaves the same as "new Type;", not |
| // "new Type();"), so it will leave non-class types uninitialized. |
| template <typename... Ts> |
| void Init(Ts&&... args) { |
| new (&space_) Type(std::forward<Ts>(args)...); |
| } |
| |
| // Init() that is equivalent to copy and move construction. |
| // Enables usage like this: |
| // ManualConstructor<std::vector<int>> v; |
| // v.Init({1, 2, 3}); |
| void Init(const Type& x) { new (&space_) Type(x); } |
| void Init(Type&& x) { new (&space_) Type(std::move(x)); } |
| |
| void Destroy() { get()->~Type(); } |
| |
| private: |
| typename std::aligned_storage<sizeof(Type), alignof(Type)>::type space_; |
| }; |
| |
| } // namespace grpc_core |
| |
| #endif |