RFR: 8251329: (zipfs) Files.walkFileTree walks infinitely if zip has dir named "." inside

[Jaikiran Pai]

On Sun, 25 Jul 2021 21:56:10 GMT, Lance Andersen <lancea at openjdk.org> wrote:

> Hi,
> 
> As discussed in the https://mail.openjdk.java.net/pipermail/core-libs-dev/2021-July/079621.html thread, this is the revised patch to address the use of '.' and '..' within Zip FS
> 
> Zip FS needs to use "." and ".." as links to the current and parent directories and cannot reliably support entries that have "." and ".." as name elements.  This patch updates Zip Fs  to reject ZIP files that have entries in the CEN that can't be used for files in a file system.
> 
> 
> Mach5 tiers 1 through 3 have been run without any errors encountered .
> 
> Best,
> Lance

This change looks fine to me. I was unsure how the writing/creating entries with `.` or `..` with `ZipFileSystem` would behave in context of this change, so I gave this a try locally with the changes from this PR:


try (FileSystem zipfs = FileSystems.newFileSystem(ZIPFILE)) {
            final Path[] paths = new Path[]{
                    zipfs.getPath("./Hello.txt"),
                    zipfs.getPath("../../../Hello.txt"),
                    zipfs.getPath("../Hello.txt")};
            for (int i = 0; i < paths.length; i++) {
                try (OutputStream os = Files.newOutputStream(paths[i])) {
                    os.write(("Hello " + i).getBytes(StandardCharsets.UTF_8));
                }
            }
        }

This code runs fine and it ends up creating (just one) CEN entry for `Hello.txt`:

JTwork/scratch/zipfsDotDotTest.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
        7  07-26-2021 15:07   Hello.txt

In other words, the `ZipFileSystem` doesn't end up creating a zip file which is then rejected by `ZipFileSystem` when creating a new filesystem using `Files.newFileSystem`. That's a good thing.

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PR: https://git.openjdk.java.net/jdk/pull/4900