[Bug 5804] New: unxz does not handle multiple xz streams on input

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=5804

           Summary: unxz does not handle multiple xz streams on input
           Product: Busybox
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: P5
         Component: Standard Compliance
        AssignedTo: unassigned at busybox.net
        ReportedBy: mjt+busybox at tls.msk.ru
                CC: busybox-cvs at busybox.net
   Estimated Hours: 0.0


According to xz format specs, http://tukaani.org/xz/xz-file-format-1.0.4.txt ,
it is explicitly allowed to have several complete xz streams (several xz files
concatenated together) in a compressed xz file.  Busybox unxz stops
decompression when seeing first end of stream.

 $ echo -n he | xz > file.xz
 $ echo llo  | xz >> file.xz
 $ unxz < file.xz
 hello
 $ busybox unxz < file.xz
 he$

Setting severity to "major" since it is a silent data loss - busybox unxz
decompresses first stream and exits with successful exit status, but remaining
data gets lost, silently.

There's at least one implementation of xz algorithm, pxz (parallel xz), which
produces multiple streams in output file.  See http://bugs.debian.org/686502
(where the above testcase comes from).

busybox zcat does this correctly.

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