Major Description
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:
$ 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
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:
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);
}
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