// Copyright 2016 PDFium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef CORE_FXCRT_CFX_MAYBE_OWNED_H_ #define CORE_FXCRT_CFX_MAYBE_OWNED_H_ #include <algorithm> #include <memory> #include <utility> #include "core/fxcrt/fx_memory.h" #include "core/fxcrt/fx_system.h" // A template that can hold either owned or unowned references, and cleans up // appropriately. Possibly the most pernicious anti-pattern imaginable, but // it crops up throughout the codebase due to a desire to avoid copying-in // objects or data. template <typename T, typename D = std::default_delete<T>> class CFX_MaybeOwned { public: CFX_MaybeOwned() : m_pObj(nullptr) {} explicit CFX_MaybeOwned(T* ptr) : m_pObj(ptr) {} explicit CFX_MaybeOwned(std::unique_ptr<T, D> ptr) : m_pOwnedObj(std::move(ptr)), m_pObj(m_pOwnedObj.get()) {} CFX_MaybeOwned(const CFX_MaybeOwned& that) = delete; CFX_MaybeOwned(CFX_MaybeOwned&& that) noexcept : m_pOwnedObj(that.m_pOwnedObj.release()), m_pObj(that.m_pObj) { that.m_pObj = nullptr; } void Reset(std::unique_ptr<T, D> ptr) { m_pOwnedObj = std::move(ptr); m_pObj = m_pOwnedObj.get(); } void Reset(T* ptr = nullptr) { m_pOwnedObj.reset(); m_pObj = ptr; } bool IsOwned() const { return !!m_pOwnedObj; } T* Get() const { return m_pObj; } std::unique_ptr<T, D> Release() { ASSERT(IsOwned()); return std::move(m_pOwnedObj); } CFX_MaybeOwned& operator=(const CFX_MaybeOwned& that) = delete; CFX_MaybeOwned& operator=(CFX_MaybeOwned&& that) { m_pOwnedObj = std::move(that.m_pOwnedObj); m_pObj = that.m_pObj; that.m_pObj = nullptr; return *this; } CFX_MaybeOwned& operator=(T* ptr) { Reset(ptr); return *this; } CFX_MaybeOwned& operator=(std::unique_ptr<T, D> ptr) { Reset(std::move(ptr)); return *this; } bool operator==(const CFX_MaybeOwned& that) const { return Get() == that.Get(); } bool operator==(const std::unique_ptr<T, D>& ptr) const { return Get() == ptr.get(); } bool operator==(T* ptr) const { return Get() == ptr; } bool operator!=(const CFX_MaybeOwned& that) const { return !(*this == that); } bool operator!=(const std::unique_ptr<T, D> ptr) const { return !(*this == ptr); } bool operator!=(T* ptr) const { return !(*this == ptr); } explicit operator bool() const { return !!m_pObj; } T& operator*() const { return *m_pObj; } T* operator->() const { return m_pObj; } private: std::unique_ptr<T, D> m_pOwnedObj; T* m_pObj; }; #endif // CORE_FXCRT_CFX_MAYBE_OWNED_H_