THere doesn't seem to be any file compression utilities available for RISC OS
that support more recent file compression formats and retains RISC OS file type
information.

Luckily the libzip library (see libzip.org) suports more recent compression formats and makes
it straight forward to retain RISC OS file types.

Enclosed in the zip file testzip.zip available from "here":https.riscosports.co.uk/eabi are
two simple Frontend module apps. One called !testzip and the other !testunzip.

As the nane implies these are just simple test versions at the moment so may contain bugs and/or missing features.
For the fastest possible compression/decompression place everthing in a RAM disc.

Example usage for !testzip.

Folder RAM::RamDisc0.$.!ArtWorks2
Zip RAM::RamDisc0.$.Artworks2/zip

Options

o store     o bzip2     o xz
0 deflate   o lzma      o zstd

Compression Level [1]

Click 'Run' to start compressing 'Folder' to 'Zip' using 'deflate' compression level '1'.

Example usage for !testunzip

Zip RAM::RamDisc0.$.Artworks2/zip
Folder RAM::RamDisc0.$

Encryption

o Enable   0 disable
Password <password>

Click 'Run' to start uncompressing 'Zip' to 'Folder'.

Supported compression formats are,

store
deflate
bzip2
lzma
xz
zstd

Example usage for !testzipcheck

ZIp RAM::RamDisc0.$.Artworks2/zip

Options

0 Test zip file   0 Verbose
o List zip file contents
o Password <password>

Clieck 'Run to start testing the 'Zip'.

Supported compression formats are,

store (compatible with SparkFS)
deflate (compatible with SparkFS)
bzip2
lzma
xz
zstd

Encryption defaults to Winzip AES 256 when creating Zip files with !testzip.

When extracting a Zip file with !testunzip or testing with testzipcheck Winzip AES 128, 192, 256 and PKWARE
traditional encryption formats are supported.

Deflate and store are compatible with e.g. SparkFS. The other formats cause an 'unsupported compression format'
if you try to extract the files using SparkFS. The contents of the zip files can still be navigated using
SparkFS as they are just normal zip files but with an unsupported compression method.

Valid values for the compression level are 1-9. Use a lower number for faster compression.
each compression format has it's pros and cons. lzma and xz are much slower compressing but can produce much
smaller zip file. zstd gives much faster compression/decompression speed for certain types of files.

One thing to look out for it that the directory and file paths are held as UTF8 in the zip file. Some file names
will display incorrectly using e.g. SparkFS. !testunzip will convert them correctly when extracting from the zip file.

Also at the moment only folder paths can be compressed. So to compress a single file it must be located in a folder.

Contact
-------
Chris gransden - chrisg@care4free.net

License
-------

Copyright (C) 1999-2020 Dieter Baron and Thomas Klausner

The authors can be contacted at <libzip@nih.at>

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

1. Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in
  the documentation and/or other materials provided with the
  distribution.

3. The names of the authors may not be used to endorse or promote
  products derived from this software without specific prior
  written permission.

THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
