// $Id$
   
   import java.io.*;
   
   public class BitOutputStream
   {
     private OutputStream out;
     private int buffer;
     private int bitCount;
   
     public BitOutputStream( OutputStream out ) {
       this.out = out;
     }
   
     synchronized public void writeBit( int bit ) throws IOException {
       if (out==null)
         throw new IOException( "Already closed" );
   
       if (bit != 0 && bit != 1) {
         throw new IOException( bit+" is not a bit" );
       }
   
       buffer |= bit<<bitCount;
       bitCount++;
   
       if (bitCount==8) {
         flush();
       }
     }
   
     private void flush() throws IOException {
       if (bitCount>0) {
         out.write( (byte)buffer );
         bitCount=0;
         buffer=0;
       }
     }
   
     public void close() throws IOException {
       flush();
       out.close();
       out = null;
     }
   }