| // 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. |
| |
| // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com |
| |
| #ifndef CORE_FXCRT_SHARED_COPY_ON_WRITE_H_ |
| #define CORE_FXCRT_SHARED_COPY_ON_WRITE_H_ |
| |
| #include "core/fxcrt/fx_system.h" |
| #include "core/fxcrt/retain_ptr.h" |
| |
| namespace fxcrt { |
| |
| // A shared pointer to an object with Copy on Write semantics that makes it |
| // appear as if all instances were independent. |ObjClass| must implement the |
| // requirements of |Retainable| from retain_ptr.h, and must also provide a |
| // Clone() method. Often this will just call MakeRetain<>(*this) but will need |
| // to be virtual if |ObjClass| is subclassed. |
| template <class ObjClass> |
| class SharedCopyOnWrite { |
| public: |
| SharedCopyOnWrite() = default; |
| SharedCopyOnWrite(const SharedCopyOnWrite& other) |
| : m_pObject(other.m_pObject) {} |
| ~SharedCopyOnWrite() = default; |
| |
| template <typename... Args> |
| ObjClass* Emplace(Args... params) { |
| m_pObject = pdfium::MakeRetain<ObjClass>(params...); |
| return m_pObject.Get(); |
| } |
| |
| SharedCopyOnWrite& operator=(const SharedCopyOnWrite& that) { |
| if (*this != that) |
| m_pObject = that.m_pObject; |
| return *this; |
| } |
| |
| void SetNull() { m_pObject.Reset(); } |
| const ObjClass* GetObject() const { return m_pObject.Get(); } |
| |
| template <typename... Args> |
| ObjClass* GetPrivateCopy(Args... params) { |
| if (!m_pObject) |
| return Emplace(params...); |
| if (!m_pObject->HasOneRef()) |
| m_pObject = m_pObject->Clone(); |
| return m_pObject.Get(); |
| } |
| |
| bool operator==(const SharedCopyOnWrite& that) const { |
| return m_pObject == that.m_pObject; |
| } |
| bool operator!=(const SharedCopyOnWrite& that) const { |
| return !(*this == that); |
| } |
| explicit operator bool() const { return !!m_pObject; } |
| |
| private: |
| RetainPtr<ObjClass> m_pObject; |
| }; |
| |
| } // namespace fxcrt |
| |
| using fxcrt::SharedCopyOnWrite; |
| |
| #endif // CORE_FXCRT_SHARED_COPY_ON_WRITE_H_ |