private   byte [] pack( byte [] unpacked)
  {
     int  packedLen = unpacked.length - (unpacked.length /  8 );
     byte [] packed =  new   byte [packedLen];
     int  pos =  0 ;

     int  i =  0 ;
     while  (i < unpacked.length)
    {
       int  jmax = (i +  7 ) > unpacked.length ? unpacked.length - i :  7 ;
       int  mask = 0x1;
       for  ( int  j =  0 ; j < jmax; j++)
      {
         int  b1 = ( int )unpacked[i + j] & 0xff;
         int  b2 = 0x0;
         try 
        {
          b2 = ( int )unpacked[i + j +  1 ] & mask;
        }
         catch  (ArrayIndexOutOfBoundsException x)
        {
        }

        packed[pos++] = ( byte )((b1 >>> j) | (b2 << ( 8  - (j +  1 ))));
        mask = (mask <<  1 ) |  1 ;
      }

      i +=  8 ;
    }

     return  (packed);
  }