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

class Cirbuf
{ 
    public Cirbuf() { this(SIZE); }   // no-arg constructor
    public Cirbuf(int s)
    {    head = tail = length = 0;
         size = s;
         cb = new char[s];  // char array buffer
    }
    public boolean isEmpty() { return(length == 0); }
    public boolean isFull() { return(length == size);}
    
    public boolean put(char c)
    {   if ( ! isFull() ) 
        {  cb[tail++] = c;
           length++;
           tail = mod(tail);
           return(true);
        }
        return(false);
    }

    public boolean get(char[] c)
    {   if ( ! isEmpty() )
        {  c[0] = cb[head++];
           length--;
           head = mod(head);
           return(true);
        }
        return(false);
    }
    private static final int SIZE = 16;
    private int head;    // first char in buffer
    private int tail;    // first empty slot in buffer
    private 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); }
}