code: public int copyTo(byte[] dest, int start)
        throws BufferTooSmallException {
      if (size > (dest.length - start)) {
        throw new BufferTooSmallException("size is " + size
            + ", buffer availabe size is " + (dest.length - start));
      }
      if (size > 0) {
        System.arraycopy(bytes, 0, dest, start, size);
      }
      return size;
    }
docs: copy the byte array to the dest array, and return the number of bytes
  copied.
  
  @param dest
  @param maxLen
  @param start
  @return