public class Ringpuffer {
   private Object[] buf;
   /* add more variables here */

   public Ringpuffer (int size) {
      buf = new Object[size];
      /* fill code here to initialize buffer and other variables */
   }
  
   /* return index position in our array for a given sequence number */
   private int idx (int s) {
      /* fill code in here to compute index number */
      return -1; // change this as neccessary!
   }

  /* return data of next packet in sequence, or 'null' if none available */
   public Object getnextpacket() {
      /* fill code in here */
      return null; // change this as neccessary!
   }

   /* return sequence number if this packet is acknowledged, 
    * or -1 if no ACK is sent. 
    */
   public int storepacket (int s, Object data) {
      /* fill in here */
      return s;  // change this as neccessary!
   }

   /* Optional: return buffer state as string representation */
   public String show () {
      return ".";
   }
}