Generate ISO and retrieve the size after adding files

Question

I am trying to generate an ISO file with JIIC library:

https://github.com/stephenc/java-iso-tools

The thing is that I need to know the exact amount of the generated (to be) iso file after adding a file. (I need to have a restriction on the generated iso file size and if exceeds, to generate a new iso file).

I am trying:

        long currentIsoSize;
        var numOfCreatedIsos = 1;
        var root = new ISO9660RootDirectory();
        for (var i = 0; i<listFilesInPdfDir.length; i++) {
            if (listFilesInPdfDir[i].isDirectory()) {
                currentIsoSize = generateIso(event, numOfCreatedIsos, root, listFilesInPdfDir[i]);
                if (maxIsoFileSizeExceeds(currentIsoSize)) {
                    root.getDirectories().remove(root.getDirectories().get(root.getDirectories().size()-1));
                    generateIso(event, numOfCreatedIsos, root, null);
                    root = new ISO9660RootDirectory();
                    numOfCreatedIsos++;
                    i--;
                }
            } else {
                log.warn("File: {} skipped", listFilesInPdfDir[i]);
            }
        }


private long generateIso(ArchiveEventTrigger event, int numOfCreatedIsos, ISO9660RootDirectory root, File file) throws HandlerException, FileNotFoundException {
        if (file != null) {
            var directory = root.addDirectory(file);
            for (var pdf : Objects.requireNonNull(file.listFiles())) {
                directory.addFile(pdf);
            }
        }
        var isoName = ArchiveUtils.buildIsoName(event, numOfCreatedIsos);

        var isoFile = new File("DIR_TO_ISO"+isoName);

        var handler = new ISOImageFileHandler(isoFile);
        var iso = new CreateISO(handler, root);
        iso.process(Utils.isoConfig("daily-isos-"+numOfCreatedIsos), null, null, null);
        return new File("DIR_TO_ISO"+isoName).length();
    }

The thing is that it creates the appropriate ISO but:

1. The file size is not the expected one (files: 70MB - iso: 60MB(about the size of the first directory inserted to iso)
2. Only the first directory has valid files, the other directories have the files but are corrupted.

I noticed that it is happening because of the iso.process call for the same iso file.

Any suggestions?