Martin

module refcounting;

import core.exception;
import std.c.stdlib;

__gshared Object lock;
__gshared int[void*] refCounts;

shared static this()
{

    enum objSize = __traits(classInstanceSize, Object);

    void* memory = malloc(objSize);

    if (!memory)
    {
        throw new OutOfMemoryError;
    }

    lock = emplace!(Object)(memory[0..objSize]);

}

struct RefCountedObj(T)
    if (is(T == class))
{
private:
    T _val;

public:
    alias _val this;

    static RefCountedObj!(T) create(Args...)(Args args)
    {

        RefCountedObj!(T) obj;
        obj._val = alloc!(T)(args);

        return obj;

    }

    this(this)
    {

        synchronized(lock)
        {
            ++refCounts[cast(void*)_val];
        }

    }

    ~this()
    {

        synchronized(lock)
        {

            int refCount = --refCounts[cast(void*)_val];

            if (refCount == 0)
            {
                _val.__dtor;
                free(cast(void*)_val);
            }
        }

    }

    void opAssign(T value)
    {

        if (cast(void*)value != cast(void*)_val)
        {

            synchronized(lock)
            {

                int refCount = --refCounts[cast(void*)_val];

                if (refCount == 0)
                {
                    _val.__dtor;
                    free(cast(void*)_val);
                }

            }

        }

    }

}