def go()

in xar/xar_util.py [0:0]
57 lines of code
12 McCabe index (conditional complexity)

    def go(self):
        "Make the XAR file."
        logger.info("Squashing %s to %s" % (self.dirname, self.output))
        if self.uuid is None:
            self.uuid = make_uuid()

        if self.version is None:
            self.version = time.time()

        tf = tempfile.NamedTemporaryFile(delete=False)
        # Create!
        sqopts = self.squashfs_options
        cmd = [
            sqopts.mksquashfs,
            self.dirname,
            tf.name,
            "-noappend",
            "-noI",
            "-noX",  # is this worth it?  probably
            "-force-uid",
            "nobody",
            "-force-gid",
            NOGROUP,
            "-b",
            str(sqopts.block_size),
            "-comp",
            sqopts.compression_algorithm,
        ]
        if sqopts.compression_algorithm == "zstd":
            cmd.extend(("-Xcompression-level", str(sqopts.zstd_level)))

        if self.sort_file:
            cmd.extend(["-sort", self.sort_file])

        if sys.stdout.isatty():
            subprocess.check_call(cmd)
        else:
            with open("/dev/null", "wb") as f:
                subprocess.check_call(cmd, stdout=f)

        headers = [self.header_prefix]
        # Take the squash file, create a header, and write it
        with open(self.output, "wb") as of:
            # Make a "safe" header that is easily parsed and also not
            # going to explode if accidentally executed.
            headers.append('OFFSET="$OFFSET"')
            headers.append('UUID="$UUID"')
            headers.append('VERSION="%d"' % self.version)
            for key, val in self.xar_header.items():
                headers.append('%s="%s"' % (key, str(val).replace('"', " ")))
            headers.append("#xar_stop")
            headers.append("echo This XAR file should not be executed by sh")
            headers.append("exit 1")
            headers.append("# Actual squashfs file begins at $OFFSET")
            text_headers = "\n".join(headers) + "\n"
            # 128 is to account for expansion of $OFFSET and $UUID;
            # it's well over what they might reasonably be.
            header_size = _align_offset(128 + len(text_headers))
            text_headers = text_headers.replace("$OFFSET", "%d" % header_size)
            text_headers = text_headers.replace("$UUID", self.uuid)
            text_headers += "\n" * (header_size - len(text_headers))
            of.write(text_headers.encode("UTF-8"))

            # Now append the squashfs file to the header.
            with open(tf.name, "rb") as rf:
                while True:
                    data = rf.read(1024 * 1024)
                    if not data:
                        break
                    of.write(data)