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From "Peter Lee (Jira)" <j...@apache.org>
Subject [jira] [Updated] (COMPRESS-550) Support writing self-extracting preamble data to a zip archive
Date Mon, 07 Sep 2020 06:37:00 GMT

     [ https://issues.apache.org/jira/browse/COMPRESS-550?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Peter Lee updated COMPRESS-550:
-------------------------------
    Assignee: Peter Lee

> Support writing self-extracting preamble data to a zip archive
> --------------------------------------------------------------
>
>                 Key: COMPRESS-550
>                 URL: https://issues.apache.org/jira/browse/COMPRESS-550
>             Project: Commons Compress
>          Issue Type: New Feature
>          Components: Archivers
>    Affects Versions: 1.20
>            Reporter: Scott Frederick
>            Assignee: Peter Lee
>            Priority: Major
>          Time Spent: 1h 40m
>  Remaining Estimate: 0h
>
> On Linux, it is possible to create a self-extracting zip file by prepending a script
or other executable to the zip file. For example, this can be done from the command line with
the following commands: 
> {code:bash}
> $ echo "test file text" > test.txt
> $ zip test.zip test.txt
>   adding: test.txt (stored 0%)
> $ cat /usr/bin/unzipsfx test.zip > test
> $ zipinfo test
> Archive:  test
> Zip file size: 101568 bytes, number of entries: 1
> warning [test]:  101392 extra bytes at beginning or within zipfile
>   (attempting to process anyway)
> -rw-r--r--  3.0 unx       10 tx stor 20-Jul-30 15:43 test.txt
> 1 file, 10 bytes uncompressed, 10 bytes compressed:  0.0%
> $ zip --adjust-sfx test.zip
> Zip entry offsets appear off by 101392 bytes - correcting...
> $ zipinfo test
> Archive:  test
> Zip file size: 101568 bytes, number of entries: 1
> -rw-r--r--  3.0 unx       10 tx stor 20-Jul-30 15:43 test.txt
> 1 file, 10 bytes uncompressed, 10 bytes compressed:  0.0%
> $ chmod 755 test 
> {code}
> Note that the first invocation of "zipinfo" reports that the central directory is invalid
because of extra bytes at the beginning of the zip file. "zip --adjust-sfx" can be used to
adjust the central directory to account for the self-extracting preamble bytes. 
> It would be nice to be able to prepend this kind of self-extracting preamble to a zip
using Apache Commons Compress. 
> A method like the following on ZipArchiveOutputStream seems to provide this behavior: 
> {code:java}
>     public void writePreamble(byte[] preamble) throws IOException {
>         if (entry != null) {
>             throw new IllegalStateException("Preamble must be written before creating
an entry");
>         }
>         this.streamCompressor.writeCounted(preamble);
>     }
> {code}
>  
>  



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