gistfile1.d

struct File
{
    private struct Impl
    {
        uint refs = uint.max / 2;
        //Other 'by-reference' members ...
        this(uint r)
        {
            refs = r;
        }
    }
    private Impl * p;

    this()
    {
        p = new Impl(1);
    }

    ~this()
    {
        if (!p) return;
        if (p.refs == 1) close();
        else --p.refs;
    }

    this(this)
    {
        if (!p) return;
        assert(p.refs);
        ++p.refs;
    }

    /**
    Assigns a file to another. The target of the assignment gets detached
    from whatever file it was attached to, and attaches itself to the new
    file.
    */
    void opAssign(File rhs)
    {
        swap(p, rhs.p);
    }

    void detach()
    {
        if (!p) return;
        if (p.refs == 1) close();
        else --p.refs;
        p = null;
    }
}