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/*
* Copyright 2009, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
// Yet another implementation of a basic, intrusive reference-counting system.
#ifndef O3D_CORE_CROSS_SMART_PTR_H_
#define O3D_CORE_CROSS_SMART_PTR_H_
#include "base/basictypes.h"
namespace o3d {
// The intrusive part of the reference counting mechanism. All objects to
// be used within the reference-counting system must inherit from RefCounted.
// The class contains the reference count.
class RefCounted {
template <class C>
friend class SmartPointer;
protected:
RefCounted() : reference_count_(0) {
}
// Call when a new reference is made to the object.
void AddRef() const {
++reference_count_;
}
// Call when a reference to the object is no longer needed.
int Release() const {
return --reference_count_;
}
private:
mutable int reference_count_;
DISALLOW_COPY_AND_ASSIGN(RefCounted);
};
// Template wrapper class that controls the lifetime of heap-constructed
// objects.
template <class C>
class SmartPointer {
public:
typedef C* Pointer;
typedef C& Reference;
typedef C ClassType;
// SmartPointer objects initialize to NULL on construction.
SmartPointer() : data_(NULL) {
}
// This copy constructor is not marked explicit on purpose, so that
// we can copy smart pointers implicitly.
SmartPointer(const SmartPointer<C>& pointer) // NOLINT
: data_(pointer.Get()) {
AddRef();
}
explicit SmartPointer(Pointer data) : data_(data) {
AddRef();
}
~SmartPointer() {
Release();
}
SmartPointer<C>& operator=(const SmartPointer<C>& rhs);
// Operators to return a reference and pointer to the data, respectively.
// Note that the constness of the operators obeys normal C++ pointer
// semantics: If the pointer is const, the data is not const.
Reference operator*() const {
return *data_;
}
Pointer operator->() const {
return data_;
}
// Casting opertor needed by the plug-in generator code.
// TODO: Remove this method so that all conversions between smart-
// pointers and raw-pointers are explicit.
operator Pointer() const {
return data_;
}
Pointer Get() const {
return data_;
}
bool IsNull() const {
return data_ == NULL;
}
void Reset() {
*this = SmartPointer<C>(NULL);
}
private:
// Helper function to conditionally add a reference to the pointed-to-data.
void AddRef() {
if (data_) {
data_->AddRef();
}
}
// Helper function to decrement the reference count of the pointed-to-data.
// If the reference count is zero after the decrement, then the object is
// deleted, and the pointer assigned to NULL.
void Release();
Pointer data_;
};
// Provide a convenience equality test operator on SmartPointer objects.
template <class C>
inline bool operator==(const SmartPointer<C>& lhs, const SmartPointer<C>& rhs) {
return lhs.Get() == rhs.Get();
}
template <class C>
inline SmartPointer<C>& SmartPointer<C>::operator=(const SmartPointer<C>& rhs) {
if (this == &rhs) {
return *this;
}
Release();
data_ = rhs.data_;
AddRef();
return *this;
}
template <class C>
void SmartPointer<C>::Release() {
if (data_) {
if (data_->Release() == 0) {
delete data_;
}
data_ = NULL;
}
}
} // namespace o3d
#endif // O3D_CORE_CROSS_SMART_PTR_H_
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