1 // Copyright 2016 PDFium 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. 4 5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com 6 7 #ifndef CORE_FXCRT_SHARED_COPY_ON_WRITE_H_ 8 #define CORE_FXCRT_SHARED_COPY_ON_WRITE_H_ 9 10 #include "core/fxcrt/fx_system.h" 11 #include "core/fxcrt/retain_ptr.h" 12 13 namespace fxcrt { 14 15 // A shared object with Copy on Write semantics that makes it appear as 16 // if each one were independent. 17 template <class ObjClass> 18 class SharedCopyOnWrite { 19 public: 20 SharedCopyOnWrite() {} 21 SharedCopyOnWrite(const SharedCopyOnWrite& other) 22 : m_pObject(other.m_pObject) {} 23 ~SharedCopyOnWrite() {} 24 25 template <typename... Args> 26 ObjClass* Emplace(Args... params) { 27 m_pObject.Reset(new ObjClass(params...)); 28 return m_pObject.Get(); 29 } 30 31 SharedCopyOnWrite& operator=(const SharedCopyOnWrite& that) { 32 if (*this != that) 33 m_pObject = that.m_pObject; 34 return *this; 35 } 36 37 void SetNull() { m_pObject.Reset(); } 38 const ObjClass* GetObject() const { return m_pObject.Get(); } 39 40 template <typename... Args> 41 ObjClass* GetPrivateCopy(Args... params) { 42 if (!m_pObject) 43 return Emplace(params...); 44 if (!m_pObject->HasOneRef()) 45 m_pObject.Reset(new ObjClass(*m_pObject)); 46 return m_pObject.Get(); 47 } 48 49 bool operator==(const SharedCopyOnWrite& that) const { 50 return m_pObject == that.m_pObject; 51 } 52 bool operator!=(const SharedCopyOnWrite& that) const { 53 return !(*this == that); 54 } 55 explicit operator bool() const { return !!m_pObject; } 56 57 private: 58 RetainPtr<ObjClass> m_pObject; 59 }; 60 61 } // namespace fxcrt 62 63 using fxcrt::SharedCopyOnWrite; 64 65 #endif // CORE_FXCRT_SHARED_COPY_ON_WRITE_H_ 66
