/**
     * Continues an MD4 message digest using the input byte.
     */
    public void engineUpdate (byte b) {
        // compute number of bytes still unhashed; ie. present in buffer
        int i = (int)(count % BLOCK_LENGTH);
        count++;                                        // update number of bytes
        buffer[i] = b;
        if (i == BLOCK_LENGTH - 1)
            transform(buffer, 0);
    }

    /**