/*==========================================================================
 * weakref.d
 *    Written in the D Programming Language (http://www.digitalmars.com/d)
 */
/***************************************************************************
 * <TODO: Module Summary>
 *
 * <TODO: Description>
 *
 * Authors:  William V. Baxter III
 * Date: 21 Jan 2008
 * Copyright: (C) 2007  William Baxter
 */
//===========================================================================

module weakref;

class WeakRef(T : Object) {
private:
    size_t cast_ptr_;
    void unhook(Object o) {
        debug { writefln("Unhook! [%s]",o); }
        if (cast(size_t)cast(void*)o == cast_ptr_) {
            o.notifyUnRegister(&unhook);
            cast_ptr_ = 0;
        }
    }
public:

    this(T tptr) {
        cast_ptr_ = cast(size_t)cast(void*)tptr;
        tptr.notifyRegister(&unhook);
    }
    ~this() {
        T p = ptr();
        if (p) p.notifyUnRegister(&unhook);
    }
    T ptr() {
        return cast(T)cast(void*)cast_ptr_;
    }
    WeakRef dup() {
        return new WeakRef(ptr());
    }
}


static import std.gc;
import std.stdio;

unittest {
    
    class Something {
        int value;
        this(int v) { value = v; }
        ~this() {
            writefln("something %d destroyed", value);
        }
        string toString() {
            return "Isn't that something (" ~ std.string.toString(value) ~") !";
        }
    }


    auto a = new Something(1);
    auto wa = new WeakRef!(Something)(a);

    std.gc.fullCollect();
    
    writefln("a = ", a);
    writefln("wa = ", wa.ptr);
    assert(a is wa.ptr);

    delete a;

    std.gc.fullCollect();
    
    writefln("a = ", a);
    writefln("wa = ", wa.ptr);

    assert(wa.ptr is null);


}

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