Compression – Choosing the Best Archive/Compression Format

To PUT data to the server compressed you must compress the request body and set the Content-Encoding: gzip header. The header itself must be uncompressed. It's documented in mod_deflate:

The mod_deflate module also provides a filter for decompressing a gzip compressed request body. In order to activate this feature you have to insert the DEFLATE filter into the input filter chain using SetInputFilter or AddInputFilter.

...

Now if a request contains a Content-Encoding: gzip header, the body will be automatically decompressed. Few browsers have the ability to gzip request bodies. However, some special applications actually do support request compression, for instance some WebDAV clients.

And an article describing it is here:

So how do you do it? Here is a blurb, again from the mod_deflate source code: only work on main request/no subrequests. This means that the whole body of the request must be gzip compressed if we chose to use this, it is not possible to compress only the part containing the file for example in a multipart request.

Separately, a browser can request server response content to be compressed by setting Accept-Encoding header as per here:

GET /index.html HTTP/1.1
Host: www.http-compression.com
Accept-Encoding: gzip
User-Agent: Firefox/1.0

This will return compressed data to the browser.

I think you'll want to use a case statement to choose how to unpack the input archive based on the filename (or perhaps use file to base it on the content instead). Unpack the input archive to a temporary directory, piping stdout/stdin to /dev/null or a file. Then run zip on the contents of the temporary directory, saving to a filename provided on the commandline. Remove the temporary directory.

Something like this (UNTESTED):

infile="$1"
outfile="$2"
# Add syntax checking here
tempdir=`mktemp -d`
case "$infile" in
    *.tar.gz)
        tar -C "$tempdir" -xzf "$infile" 2>/dev/null
        ;;
    *.tar)
        tar -C "$tempdir" -xf "$infile" 2>/dev/null
        ;;
... # Add handling for other input formats here
    *)
        echo "Unrecognized input format" >&2
        false
        ;;
esac
if [ $? -ne 0 ]; then
    echo "Error processing input file $infile" >&2 # or just echo "error"
    rm -rf "$tempdir"
    exit 1
fi
(cd "$tempdir" && zip "$outfile" .)
rm -rf "$tempdir"

You'll need to determine what errors you get from tar, etc when an achive is "encrypted", and update the error messages appropriately to match what you're after. But this should give you a reasonable starting point.