/*
 * call-seq:
 *    write(data)
 * Actually writes some data into this stream.
 *
 * @param [String] data the data to write
 * @return [Integer] the length of the data which was written (uncompressed)
 * @raise [IOError] if the stream has been closed
 */
static VALUE bz_writer_write(VALUE obj, VALUE a) {