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/*
* This file is part of OpenTTD.
* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file countedptr.hpp CCountedPtr - smart pointer implementation. */
#ifndef COUNTEDPTR_HPP
#define COUNTEDPTR_HPP
/**
* CCountedPtr - simple reference counting smart pointer.
*
* One of the standard ways how to maintain object's lifetime.
*
* See http://ootips.org/yonat/4dev/smart-pointers.html for more
* general info about smart pointers.
*
* This class implements ref-counted pointer for objects/interfaces that
* support AddRef() and Release() methods.
*/
template <class Tcls_>
class CCountedPtr {
/** redefine the template argument to make it visible for derived classes */
public:
typedef Tcls_ Tcls;
protected:
/** here we hold our pointer to the target */
Tcls *m_pT;
public:
/** default (nullptr) construct or construct from a raw pointer */
inline CCountedPtr(Tcls *pObj = nullptr) : m_pT(pObj)
{
AddRef();
}
/** copy constructor (invoked also when initializing from another smart ptr) */
inline CCountedPtr(const CCountedPtr &src) : m_pT(src.m_pT)
{
AddRef();
}
/** destructor releasing the reference */
inline ~CCountedPtr()
{
Release();
}
protected:
/** add one ref to the underlying object */
inline void AddRef()
{
if (m_pT != nullptr) m_pT->AddRef();
}
public:
/** release smart pointer (and decrement ref count) if not null */
inline void Release()
{
if (m_pT != nullptr) {
Tcls *pT = m_pT;
m_pT = nullptr;
pT->Release();
}
}
/** dereference of smart pointer - const way */
inline const Tcls *operator->() const
{
assert(m_pT != nullptr);
return m_pT;
}
/** dereference of smart pointer - non const way */
inline Tcls *operator->()
{
assert(m_pT != nullptr);
return m_pT;
}
/** raw pointer casting operator - const way */
inline operator const Tcls*() const
{
assert(m_pT == nullptr);
return m_pT;
}
/** raw pointer casting operator - non-const way */
inline operator Tcls*()
{
return m_pT;
}
/** operator & to support output arguments */
inline Tcls** operator&()
{
assert(m_pT == nullptr);
return &m_pT;
}
/** assignment operator from raw ptr */
inline CCountedPtr& operator=(Tcls *pT)
{
Assign(pT);
return *this;
}
/** assignment operator from another smart ptr */
inline CCountedPtr& operator=(const CCountedPtr &src)
{
Assign(src.m_pT);
return *this;
}
/** assignment operator helper */
inline void Assign(Tcls *pT);
/** one way how to test for nullptr value */
inline bool IsNull() const
{
return m_pT == nullptr;
}
/** another way how to test for nullptr value */
//inline bool operator == (const CCountedPtr &sp) const {return m_pT == sp.m_pT;}
/** yet another way how to test for nullptr value */
//inline bool operator != (const CCountedPtr &sp) const {return m_pT != sp.m_pT;}
/** assign pointer w/o incrementing ref count */
inline void Attach(Tcls *pT)
{
Release();
m_pT = pT;
}
/** detach pointer w/o decrementing ref count */
inline Tcls *Detach()
{
Tcls *pT = m_pT;
m_pT = nullptr;
return pT;
}
};
template <class Tcls_>
inline void CCountedPtr<Tcls_>::Assign(Tcls *pT)
{
/* if they are the same, we do nothing */
if (pT != m_pT) {
if (pT != nullptr) pT->AddRef(); // AddRef new pointer if any
Tcls *pTold = m_pT; // save original ptr
m_pT = pT; // update m_pT to new value
if (pTold != nullptr) pTold->Release(); // release old ptr if any
}
}
/**
* Adapter wrapper for CCountedPtr like classes that can't be used directly by stl
* collections as item type. For example CCountedPtr has overloaded operator & which
* prevents using CCountedPtr in stl collections (i.e. std::list<CCountedPtr<MyType> >)
*/
template <class T> struct AdaptT {
T m_t;
/** construct by wrapping the given object */
AdaptT(const T &t)
: m_t(t)
{}
/** assignment operator */
T& operator = (const T &t)
{
m_t = t;
return t;
}
/** type-cast operator (used when AdaptT is used instead of T) */
operator T& ()
{
return m_t;
}
/** const type-cast operator (used when AdaptT is used instead of const T) */
operator const T& () const
{
return m_t;
}
};
/**
* Simple counted object. Use it as base of your struct/class if you want to use
* basic reference counting. Your struct/class will destroy and free itself when
* last reference to it is released (using Release() method). The initial reference
* count (when it is created) is zero (don't forget AddRef() at least one time if
* not using CCountedPtr<T>.
*
* @see misc/countedobj.cpp for implementation.
*/
struct SimpleCountedObject {
int32 m_ref_cnt;
SimpleCountedObject()
: m_ref_cnt(0)
{}
virtual ~SimpleCountedObject()
{}
virtual int32 AddRef();
virtual int32 Release();
virtual void FinalRelease() {};
};
#endif /* COUNTEDPTR_HPP */
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