///////    Cirbuf.java    ///////

public class Cirbuf
{ 
    public Cirbuf()
    {  this(D_SIZE); }   // constructor call
    public Cirbuf(int s)
    {    head = tail = length = 0;
         fin = false;
         size = s;
         cb = new char[s];
    }
    public synchronized boolean is_empty() { return(length == 0); }
    public synchronized boolean is_full() { return(length == size);}
    public synchronized boolean finished() { return(fin); }
    public synchronized void finished(boolean v) { fin=v; }
    
    public synchronized void put(char c)
    {    while ( is_full() ) 
             try
             { wait();    // wait on monitor
             } catch (InterruptedException e){}
         cb[tail++] = c;
         length++;
         tail = mod(tail);
         notify();   // resume waiting consumer thread
    }
    
    public synchronized boolean get(char c[])
    {    while ( is_empty() )
         { if ( fin ) return ( false );
           else
              try
              { wait();   // wait on monitor
              } catch (InterruptedException e){}
         }
         c[0] = cb[head++];
         length--;
         head = mod(head);
         notify(); // resume waiting producer thread
         return(true);
    }
    private static final int D_SIZE = 16;
    private volatile boolean fin = false;
    private volatile int head;    // first char in buffer
    private volatile int tail;    // first empty slot in buffer
    private volatile int length;  // number of characters in buffer
    private int size;    // capacity of buffer
    private char[] cb;   // character buffer
    private int mod(int x)
    { return(x >= size ?  x - size : x); }
}