//
// Receiver Window Buffer
//
// Idea:  See SndWinBuf.h
//
// Usage Patterns ('sn' is a sequence number):
//
// o Create a w-slot window:		RcvWinBuf *rwin = new RcvWinBuf(w);
// o Display the window buffer:		rwin->dump();
// o Accept status:			Bool accept = rwin->isInWin(sn);
// o Accept a pkt:			rwin->insert(sn); rwin->advWin();
// o Has the seq num already buffered?	rwin->isBuffered(sn);
//

typedef struct {
	  Bool		accept;	// pkt has been accepted by rcvr?
	} Rbuf;

class RcvWinBuf  {
public:	int	lo;		// lowest sn in window	(RO)
	int	w;		// window size (#pkts)	(RO)
	RcvWinBuf(int w0);	// create new receiver window buffer with w0 slots
	void advWin(void);	// advance window until 1st slot needs a pkt

	inline void dump(void) {  // dump buffer
	  printf ("  RcvWinBuf:  lo = %d\n  ", lo);
	  for (int i=0; i<w; i++) { printf (" (%d, %d),", lo+i,
						buf[(lo+i)%w].accept); }
	  printf ("\n");
	  fflush(stdout);
	}
	inline Bool isBuffered(int sn) { // YES if sn(pkt) == sn; else NO
	  if (buf[sn%w].accept)	return YES;
	  else			return NO;
	}
	inline Bool isInWin(int sn0) {	// return YES if sn sn0 is in window; else NO
	  if ((sn0 >= lo) && (sn0 < (lo+w)))	return YES;
	  else					return NO;
	}
	inline void insert(int sn) {	// insert pkt with sn(p) into buffer
	  buf[sn%w].accept = YES;
	}
private:
	Rbuf	*buf;		// w buffer ptrs
};