juce_ReferenceCountedObject.h

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/*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   The code included in this file is provided 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.
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
//==============================================================================
class JUCE_API  ReferenceCountedObject
{
public:
    //==============================================================================
    void incReferenceCount() noexcept
    {
        ++refCount;
    }

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

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

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

    ReferenceCountedObject (const ReferenceCountedObject&) noexcept {}
    ReferenceCountedObject (ReferenceCountedObject&&) noexcept {}
    ReferenceCountedObject& operator= (const ReferenceCountedObject&) noexcept  { return *this; }
    ReferenceCountedObject& operator= (ReferenceCountedObject&&) noexcept       { return *this; }

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

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

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

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

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

    SingleThreadedReferenceCountedObject (const SingleThreadedReferenceCountedObject&) {}
    SingleThreadedReferenceCountedObject (SingleThreadedReferenceCountedObject&&) {}
    SingleThreadedReferenceCountedObject& operator= (const SingleThreadedReferenceCountedObject&) { return *this; }
    SingleThreadedReferenceCountedObject& operator= (SingleThreadedReferenceCountedObject&&) { return *this; }

    virtual ~SingleThreadedReferenceCountedObject()
    {
        // it's dangerous to delete an object that's still referenced by something else!
        jassert (getReferenceCount() == 0);
    }
 
private:
    //==============================================================================
    int refCount = 0;
    friend struct ContainerDeletePolicy<ReferenceCountedObject>;
};
 
 
//==============================================================================
template <class ObjectType>
class ReferenceCountedObjectPtr
{
public:
    using ReferencedType = ObjectType;
 
    //==============================================================================
    ReferenceCountedObjectPtr() = default;

    ReferenceCountedObjectPtr (decltype (nullptr)) noexcept {}

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

    ReferenceCountedObjectPtr (ReferencedType& refCountedObject) noexcept
        : referencedObject (&refCountedObject)
    {
        refCountedObject.incReferenceCount();
    }

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

    ReferenceCountedObjectPtr (ReferenceCountedObjectPtr&& other) noexcept
        : referencedObject (other.referencedObject)
    {
        other.referencedObject = nullptr;
    }

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

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

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

    ReferenceCountedObjectPtr& operator= (ReferencedType* newObject)
    {
        if (newObject != nullptr)
            return operator= (*newObject);
 
        reset();
        return *this;
    }

    ReferenceCountedObjectPtr& operator= (ReferencedType& newObject)
    {
        if (referencedObject != &newObject)
        {
            newObject.incReferenceCount();
            auto* oldObject = referencedObject;
            referencedObject = &newObject;
            decIfNotNull (oldObject);
        }
 
        return *this;
    }

    ReferenceCountedObjectPtr& operator= (decltype (nullptr))
    {
        reset();
        return *this;
    }

    ReferenceCountedObjectPtr& operator= (ReferenceCountedObjectPtr&& other) noexcept
    {
        std::swap (referencedObject, other.referencedObject);
        return *this;
    }

    ~ReferenceCountedObjectPtr()
    {
        decIfNotNull (referencedObject);
    }
 
    //==============================================================================
    ReferencedType* get() const noexcept                    { return referencedObject; }

    void reset() noexcept
    {
        auto 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
    }
 
    // the -> operator is called on the referenced object
    ReferencedType* operator->() const noexcept
    {
        jassert (referencedObject != nullptr); // null pointer method call!
        return referencedObject;
    }

    ReferencedType& operator*() const noexcept              { jassert (referencedObject != nullptr); return *referencedObject; }

    bool operator== (decltype (nullptr)) const noexcept     { return referencedObject == nullptr; }
    bool operator!= (decltype (nullptr)) const noexcept     { return referencedObject != nullptr; }

    bool operator== (const ObjectType* other) const noexcept                 { return referencedObject == other; }
    bool operator== (const ReferenceCountedObjectPtr& other) const noexcept  { return referencedObject == other.get(); }
    bool operator!= (const ObjectType* other) const noexcept                 { return referencedObject != other; }
    bool operator!= (const ReferenceCountedObjectPtr& other) const noexcept  { return referencedObject != other.get(); }
 
   #if JUCE_STRICT_REFCOUNTEDPOINTER
    explicit operator bool() const noexcept                 { return referencedObject != nullptr; }
 
   #else
    operator ReferencedType*() const noexcept               { return referencedObject; }
   #endif
 
   #ifndef DOXYGEN
    [[deprecated ("Use the get method instead.")]]
    ReferencedType* getObject() const { return get(); }
   #endif
 
private:
    //==============================================================================
    ReferencedType* referencedObject = nullptr;
 
    static void incIfNotNull (ReferencedType* o) noexcept
    {
        if (o != nullptr)
            o->incReferenceCount();
    }
 
    static void decIfNotNull (ReferencedType* o) noexcept
    {
        if (o != nullptr && o->decReferenceCountWithoutDeleting())
            ContainerDeletePolicy<ReferencedType>::destroy (o);
    }
};
 
 
//==============================================================================
template <typename Type>
bool operator== (const Type* object1, const ReferenceCountedObjectPtr<Type>& object2) noexcept
{
    return object1 == object2.get();
}

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