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-rw-r--r--core/fxcrt/cfx_count_ref.h81
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diff --git a/core/fxcrt/cfx_count_ref.h b/core/fxcrt/cfx_count_ref.h
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+// 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_CFX_COUNT_REF_H_
+#define CORE_FXCRT_CFX_COUNT_REF_H_
+
+#include "core/fxcrt/cfx_retain_ptr.h"
+#include "core/fxcrt/fx_system.h"
+
+// A shared object with Copy on Write semantics that makes it appear as
+// if each one were independent.
+template <class ObjClass>
+class CFX_CountRef {
+ public:
+ CFX_CountRef() {}
+ CFX_CountRef(const CFX_CountRef& other) : m_pObject(other.m_pObject) {}
+ ~CFX_CountRef() {}
+
+ template <typename... Args>
+ ObjClass* Emplace(Args... params) {
+ m_pObject.Reset(new CountedObj(params...));
+ return m_pObject.Get();
+ }
+
+ CFX_CountRef& operator=(const CFX_CountRef& 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.Reset(new CountedObj(*m_pObject));
+ return m_pObject.Get();
+ }
+
+ bool operator==(const CFX_CountRef& that) const {
+ return m_pObject == that.m_pObject;
+ }
+ bool operator!=(const CFX_CountRef& that) const { return !(*this == that); }
+ explicit operator bool() const { return !!m_pObject; }
+
+ private:
+ class CountedObj : public ObjClass {
+ public:
+ template <typename... Args>
+ CountedObj(Args... params) : ObjClass(params...), m_RefCount(0) {}
+
+ CountedObj(const CountedObj& src) : ObjClass(src), m_RefCount(0) {}
+ ~CountedObj() { m_RefCount = 0; }
+
+ bool HasOneRef() const { return m_RefCount == 1; }
+ void Retain() { m_RefCount++; }
+ void Release() {
+ ASSERT(m_RefCount);
+ if (--m_RefCount == 0)
+ delete this;
+ }
+
+ private:
+ // To ensure ref counts do not overflow, consider the worst possible case:
+ // the entire address space contains nothing but pointers to this object.
+ // Since the count increments with each new pointer, the largest value is
+ // the number of pointers that can fit into the address space. The size of
+ // the address space itself is a good upper bound on it.
+ intptr_t m_RefCount;
+ };
+
+ CFX_RetainPtr<CountedObj> m_pObject;
+};
+
+#endif // CORE_FXCRT_CFX_COUNT_REF_H_