| // Copyright 2018 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #pragma once |
| |
| #include <type_traits> |
| #include <utility> |
| |
| namespace overnet { |
| |
| //#define OVERNET_UNIQUE_PTR_MANUAL_CONSTRUCTOR |
| |
| template <typename Type> |
| class ManualConstructor { |
| public: |
| ManualConstructor() {} |
| ~ManualConstructor() {} |
| ManualConstructor(const ManualConstructor&) = delete; |
| ManualConstructor& operator=(const ManualConstructor&) = delete; |
| |
| 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 (Materialize()) 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 (Materialize()) 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 (Materialize()) Type(x); } |
| void Init(Type&& x) { new (Materialize()) Type(std::move(x)); } |
| |
| void Destroy() { |
| get()->~Type(); |
| Dematerialize(); |
| } |
| |
| private: |
| #ifndef OVERNET_UNIQUE_PTR_MANUAL_CONSTRUCTOR |
| union { |
| Type space_; |
| }; |
| Type* space() { return &space_; } |
| const Type* space() const { return &space_; } |
| Type* Materialize() { return &space_; } |
| void Dematerialize() {} |
| #else |
| typedef std::aligned_storage_t<sizeof(Type), alignof(Type)> Storage; |
| std::unique_ptr<Storage> storage_; |
| Storage* space() { |
| assert(storage_ != nullptr); |
| return storage_.get(); |
| } |
| const Storage* space() const { |
| assert(storage_ != nullptr); |
| return storage_.get(); |
| } |
| Storage* Materialize() { |
| assert(storage_ == nullptr); |
| storage_.reset(new Storage); |
| return storage_.get(); |
| } |
| void Dematerialize() { |
| assert(storage_ != nullptr); |
| storage_.reset(); |
| } |
| #endif |
| }; |
| |
| } // namespace overnet |