ReferenceCountedObject.h

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/*
  ==============================================================================
 
   This file is part of the Water library.
   Copyright (c) 2016 ROLI Ltd.
   Copyright (C) 2017-2022 Filipe Coelho <falktx@falktx.com>
 
   Permission is granted to use this software under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license/
 
   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.
 
   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.
 
  ==============================================================================
*/
 
#ifndef WATER_REFERENCECOUNTEDOBJECT_H_INCLUDED
#define WATER_REFERENCECOUNTEDOBJECT_H_INCLUDED
 
#include "Atomic.h"
 
namespace water {
 
//==============================================================================
class ReferenceCountedObject
{
public:
    //==============================================================================
    void incReferenceCount() noexcept
    {
        ++refCount;
    }

    void decReferenceCount() noexcept
    {
        wassert (getReferenceCount() > 0);
 
        if (--refCount == 0)
            delete this;
    }

    bool decReferenceCountWithoutDeleting() noexcept
    {
        wassert (getReferenceCount() > 0);
        return --refCount == 0;
    }

    int getReferenceCount() const noexcept       { return refCount.get(); }
 
 
protected:
    //==============================================================================
    ReferenceCountedObject()
        : refCount() {}

    virtual ~ReferenceCountedObject()
    {
        // it's dangerous to delete an object that's still referenced by something else!
        wassert (getReferenceCount() == 0);
    }

    void resetReferenceCount() noexcept
    {
        refCount = 0;
    }
 
private:
    //==============================================================================
    Atomic<int> refCount;
 
    CARLA_DECLARE_NON_COPYABLE (ReferenceCountedObject)
};
 
 
//==============================================================================
class SingleThreadedReferenceCountedObject
{
public:
    //==============================================================================
    void incReferenceCount() noexcept
    {
        ++refCount;
    }

    void decReferenceCount() noexcept
    {
        wassert (getReferenceCount() > 0);
 
        if (--refCount == 0)
            delete this;
    }

    bool decReferenceCountWithoutDeleting() noexcept
    {
        wassert (getReferenceCount() > 0);
        return --refCount == 0;
    }

    int getReferenceCount() const noexcept       { return refCount; }
 
 
protected:
    //==============================================================================
    SingleThreadedReferenceCountedObject() : refCount (0)  {}

    virtual ~SingleThreadedReferenceCountedObject()
    {
        // it's dangerous to delete an object that's still referenced by something else!
        wassert (getReferenceCount() == 0);
    }
 
private:
    //==============================================================================
    int refCount;
 
    CARLA_DECLARE_NON_COPYABLE (SingleThreadedReferenceCountedObject)
};
 
 
//==============================================================================
template <class ReferenceCountedObjectClass>
class ReferenceCountedObjectPtr
{
public:
    typedef ReferenceCountedObjectClass ReferencedType;
 
    //==============================================================================
    ReferenceCountedObjectPtr() noexcept
        : referencedObject (nullptr)
    {
    }

    ReferenceCountedObjectPtr (ReferencedType* refCountedObject) noexcept
        : referencedObject (refCountedObject)
    {
        incIfNotNull (refCountedObject);
    }

    ReferenceCountedObjectPtr (const ReferenceCountedObjectPtr& other) noexcept
        : referencedObject (other.referencedObject)
    {
        incIfNotNull (referencedObject);
    }

    template <typename Convertible>
    ReferenceCountedObjectPtr (const ReferenceCountedObjectPtr<Convertible>& other) noexcept
        : referencedObject (static_cast<ReferencedType*> (other.get()))
    {
        incIfNotNull (referencedObject);
    }

    ReferenceCountedObjectPtr& operator= (const ReferenceCountedObjectPtr& other)
    {
        return operator= (other.referencedObject);
    }

    template <typename Convertible>
    ReferenceCountedObjectPtr& operator= (const ReferenceCountedObjectPtr<Convertible>& other)
    {
        return operator= (static_cast<ReferencedType*> (other.get()));
    }

    ReferenceCountedObjectPtr& operator= (ReferencedType* const newObject)
    {
        if (referencedObject != newObject)
        {
            incIfNotNull (newObject);
            ReferencedType* const oldObject = referencedObject;
            referencedObject = newObject;
            decIfNotNull (oldObject);
        }
 
        return *this;
    }

    ~ReferenceCountedObjectPtr()
    {
        ReferencedType* const oldObject = referencedObject; // need to null the pointer before deleting the object
        referencedObject = nullptr;                         // in case this ptr is itself deleted as a side-effect
        decIfNotNull (oldObject);                           // of the destructor
    }
 
    //==============================================================================
    operator ReferencedType*() const noexcept       { return referencedObject; }

    ReferencedType* get() const noexcept            { return referencedObject; }

    ReferencedType* getObject() const noexcept      { return referencedObject; }
 
    // the -> operator is called on the referenced object
    ReferencedType* operator->() const noexcept
    {
        wassert (referencedObject != nullptr); // null pointer method call!
        return referencedObject;
    }
 
private:
    //==============================================================================
    ReferencedType* referencedObject;
 
    static void incIfNotNull (ReferencedType* o) noexcept
    {
        if (o != nullptr)
            o->incReferenceCount();
    }
 
    static void decIfNotNull (ReferencedType* o) noexcept
    {
        if (o != nullptr && o->decReferenceCountWithoutDeleting())
            delete o;
    }
};
 
 
//==============================================================================
template <typename ReferenceCountedObjectClass>
bool operator== (const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object1, ReferenceCountedObjectClass* const object2) noexcept
{
    return object1.get() == object2;
}

template <typename ReferenceCountedObjectClass>
bool operator== (const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object1, const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object2) noexcept
{
    return object1.get() == object2.get();
}

template <typename ReferenceCountedObjectClass>
bool operator== (ReferenceCountedObjectClass* object1, const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object2) noexcept
{
    return object1 == object2.get();
}

template <typename ReferenceCountedObjectClass>
bool operator!= (const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object1, const ReferenceCountedObjectClass* object2) noexcept
{
    return object1.get() != object2;
}

template <typename ReferenceCountedObjectClass>
bool operator!= (const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object1, const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object2) noexcept
{
    return object1.get() != object2.get();
}

template <typename ReferenceCountedObjectClass>
bool operator!= (ReferenceCountedObjectClass* object1, const ReferenceCountedObjectPtr<ReferenceCountedObjectClass>& object2) noexcept
{
    return object1 != object2.get();
}
 
}
 
#endif // WATER_REFERENCECOUNTEDOBJECT_H_INCLUDED