if f.err != nil {
		return f.err // Only occurs if size condition is violated
	}

	// Write the header and data.
	if err := tw.writeRawHeader(&tw.blk, int64(len(data)), flag); err != nil {
		return err
	}
	_, err := io.WriteString(tw, data)
	return err
}

// writeRawHeader writes the value of blk, regardless of its value.
// It sets up the Writer such that it can accept a file of the given size.