///////    File Cirbuf.H    ///////

const int D_SIZE = 16;

class Cirbuf {
   private:
      int   _head;   // first char in buffer
      int   _tail;   // first empty slot in buffer
      int   _length; // number of characters in buffer
      int   _size;   // capacity of buffer
      char* _cb;     // pointer to buffer

      int mod (int x)
          { return (x >= _size ?  x - _size : x); }
   public:
      Cirbuf (int size = D_SIZE);  // constructor
      
      Cirbuf (const Cirbuf& buf);  // copy constructor
      Cirbuf& operator= (const Cirbuf& buf);
      
      int Produce (char c);
      int Consume ();
      int IsEmpty () { return (_length == 0); }
      int IsFull () { return (_length == _size); }

      ~Cirbuf();                  // destructor
};