OgreSharedPtr.h

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/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2014 Torus Knot Software Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
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furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
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*/
#ifndef __SharedPtr_H__
#define __SharedPtr_H__

#include "OgrePrerequisites.h"
#include "OgreAtomicScalar.h"

namespace Ogre {
    enum SharedPtrFreeMethod
    {
        SPFM_DELETE,
        SPFM_DELETE_T,
        SPFM_FREE
    };

    struct SharedPtrInfo {
        inline SharedPtrInfo() 
            : useCount(1)
        {}

        virtual ~SharedPtrInfo() {}

        AtomicScalar<unsigned>  useCount;
    };

    template <class T>
    class SharedPtrInfoDelete : public SharedPtrInfo
    {
        T* mObject;
    public:
        inline SharedPtrInfoDelete(T* o) : mObject(o) {}

        virtual ~SharedPtrInfoDelete()
        {
            OGRE_DELETE mObject;
        }
    };

    template <class T>
    class SharedPtrInfoDeleteT : public SharedPtrInfo
    {
        T* mObject;
    public:
        inline SharedPtrInfoDeleteT(T* o) : mObject(o) {}

        virtual ~SharedPtrInfoDeleteT()
        {
            OGRE_DELETE_T(mObject, T, MEMCATEGORY_GENERAL);
        }
    };

    template <class T>
    class SharedPtrInfoFree : public SharedPtrInfo
    {
        T* mObject;
    public:
        inline SharedPtrInfoFree(T* o) : mObject(o) {}        

        virtual ~SharedPtrInfoFree()
        {
            OGRE_FREE(mObject, MEMCATEGORY_GENERAL);
        }
    };


    template<class T> class SharedPtr
    {
        template<typename Y> friend class SharedPtr;
    protected:
        /* DO NOT ADD MEMBERS TO THIS CLASS!
         *
         * The average Ogre application has *thousands* of them. Every extra
         * member causes extra memory use in general, and causes extra padding
         * to be added to a multitude of structures. 
         *
         * Everything you need to do can be acomplished by creatively working 
         * with the SharedPtrInfo object.
         *
         * There is no reason for this object to ever have more than two members.
         */

        T*             pRep;
        SharedPtrInfo* pInfo;

        SharedPtr(T* rep, SharedPtrInfo* info) : pRep(rep), pInfo(info)
        {
        }

    public:
        SharedPtr() : pRep(0), pInfo(0)
        {}

    private:
        static SharedPtrInfo* createInfoForMethod(T* rep, SharedPtrFreeMethod method)
        {
            switch(method) {
                case SPFM_DELETE:   return OGRE_NEW_T(SharedPtrInfoDelete<T>,  MEMCATEGORY_GENERAL) (rep);
                case SPFM_DELETE_T: return OGRE_NEW_T(SharedPtrInfoDeleteT<T>, MEMCATEGORY_GENERAL) (rep);
                case SPFM_FREE:     return OGRE_NEW_T(SharedPtrInfoFree<T>,    MEMCATEGORY_GENERAL) (rep);
            }
            assert(!"Bad method");
            return 0;
        }
    public:

        template< class Y>
        explicit SharedPtr(Y* rep, SharedPtrFreeMethod inFreeMethod = SPFM_DELETE) 
            : pRep(rep)
            , pInfo(rep ? createInfoForMethod(rep, inFreeMethod) : 0)
        {
        }

        SharedPtr(const SharedPtr& r)
            : pRep(r.pRep)
            , pInfo(r.pInfo)
        {
            if (pRep) 
            {
                ++pInfo->useCount;
            }
        }

        SharedPtr& operator=(const SharedPtr& r) {
            if (pRep == r.pRep)
            {
                assert(pInfo == r.pInfo);
                return *this;
            }
            // Swap current data into a local copy
            // this ensures we deal with rhs and this being dependent
            SharedPtr<T> tmp(r);
            swap(tmp);
            return *this;
        }
        
        /* For C++11 compilers, use enable_if to only expose functions when viable
         *
         * MSVC 2012 and earlier only claim conformance to C++98. This is fortunate,
         * because they don't support default template parameters
         */
#if __cplusplus >= 201103L
        template<class Y,
            class = typename std::enable_if<std::is_convertible<Y*, T*>::value>::type>
#else
        template<class Y>
#endif
        SharedPtr(const SharedPtr<Y>& r)
            : pRep(r.getPointer())
            , pInfo(r.pInfo)
        {
            if (pRep) 
            {
                ++pInfo->useCount;
            }
        }

        
#if __cplusplus >= 201103L
        template<class Y,
                 class = typename std::enable_if<std::is_assignable<T*, Y*>::value>::type>
#else
        template<class Y>
#endif
        SharedPtr& operator=(const SharedPtr<Y>& r)
        {
            if (pRep == r.pRep)
                return *this;
            // Swap current data into a local copy
            // this ensures we deal with rhs and this being dependent
            SharedPtr<T> tmp(r);
            swap(tmp);
            return *this;
        }

        ~SharedPtr() {
            release();
        }


        template<typename Y>
        inline SharedPtr<Y> staticCast() const
        {
            if(pRep) {
                ++pInfo->useCount;
                return SharedPtr<Y>(static_cast<Y*>(pRep), pInfo);
            } else return SharedPtr<Y>();
        }

        template<typename Y>
        inline SharedPtr<Y> dynamicCast() const
        {
            if(pRep) {
                Y* rep = dynamic_cast<Y*>(pRep);
                ++pInfo->useCount;
                return SharedPtr<Y>(rep, pInfo);
            } else return SharedPtr<Y>();
        }

        inline T& operator*() const { assert(pRep); return *pRep; }
        inline T* operator->() const { assert(pRep); return pRep; }
        inline T* get() const { return pRep; }

        void bind(T* rep, SharedPtrFreeMethod inFreeMethod = SPFM_DELETE) {
            assert(!pRep && !pInfo);
            pInfo = createInfoForMethod(rep, inFreeMethod);
            pRep = rep;
        }

        inline bool unique() const { assert(pInfo && pInfo->useCount.get()); return pInfo->useCount.get() == 1; }
        inline unsigned int useCount() const { assert(pInfo && pInfo->useCount.get()); return pInfo->useCount.get(); }
        inline void setUseCount(unsigned value) { assert(pInfo); pInfo->useCount = value; }

        inline T* getPointer() const { return pRep; }

        inline bool isNull(void) const { return pRep == 0; }

        inline void setNull(void) { 
            if (pRep)
            {
                release();
            }
        }

    protected:

        inline void release(void)
        {
            if (pRep)
            {
                assert(pInfo);
                if(--pInfo->useCount == 0)
                    destroy();
            }

            pRep = 0;
            pInfo = 0;
        }

        inline void destroy(void)
        {
            assert(pRep && pInfo);
            OGRE_DELETE_T(pInfo, SharedPtrInfo, MEMCATEGORY_GENERAL);
        }

        inline void swap(SharedPtr<T> &other) 
        {
            std::swap(pRep, other.pRep);
            std::swap(pInfo, other.pInfo);
        }
    };

    template<class T, class U> inline bool operator==(SharedPtr<T> const& a, SharedPtr<U> const& b)
    {
        return a.get() == b.get();
    }

    template<class T, class U> inline bool operator!=(SharedPtr<T> const& a, SharedPtr<U> const& b)
    {
        return a.get() != b.get();
    }

    template<class T, class U> inline bool operator<(SharedPtr<T> const& a, SharedPtr<U> const& b)
    {
        return std::less<const void*>()(a.get(), b.get());
    }
}



#endif