/* ptrbit.h      v1.0  (C) 2000 adolfo@di-mare.com */

#ifndef   PTRBIT_H
#define   PTRBIT_H

class ptrbit {
public:
    ptrbit() {}
    ptrbit(      void*   x) : _p(x)    {}
    ptrbit(const ptrbit& x) : _p(x._p) {}

    void* operator=(void* x) { return (_p = x); }

    void* ai() const { return _p; } // ai() ==> As Is
    void* vp() const {              // vp() ==> Void Pointer
        return (void*) ((unsigned long)_p & ~1UL); }

    void set(void* p) { _p = p; }

    int  marked() { return (int)((unsigned long)_p & 1UL); }
    void mark()   { (unsigned long)_p |=  1UL;  }
    void unmark() { (unsigned long)_p &= ~1UL; }

    static int aligned(const void *p)
        { return 0 == ((unsigned long)p & 1UL); }
private:
    void operator*()  {}             // forbid dereferencing
    operator void*()  { return _p; } // forbid conversion
private: // ptrbit member fields
    void *_p;
}; // ptrbit

inline int operator==(const ptrbit& x, const ptrbit& y) {
    return x.ai() == y.ai(); }
inline int operator!=(const ptrbit& x, const ptrbit& y) {
    return !(x == y); }

// This implementation requires long to hold a pointer
class ptrbit_check_that_long_holds_a_void_pointer__ {
    char _[sizeof(unsigned long) == sizeof(void*)];
};

#endif /* PTRBIT_H */

/* EOF:   ptrbit.h */