TCR Compressor and Decompressor  v1.00

Here's C source and (Atari) executables for creating and extracting TCR files.

TCR is a text compression format that's especially useful with Psion Series 3 
and Series 5 machines: there are text viewers for both which can display TCR-
compressed files directly (VReader for the 5, Reader for the 3).

    SOURCE  (Those funny-looking files ending in .c)

The source code is included here so you can compile it for other machines.  
It's written in C for the GCC compiler, and should be easily portable to 
other compilers.

See the comments in the code for restrictions and details on the format and 
algorithms.

    EXECUTABLES  (Those funny-looking files ending in .ttp)

These are for the Atari ST range.  I've only tested them on my Falcon under 
MagiC, but they should work on other machines, and with TOS, MiNT etc.  In 
particular, they handle long filenames correctly.

A TCR-encoded version of this file is included for you to practice on :)

    USAGE  (What do I with them?)

The programs have a simple text interface, for versatility and portability, 
and also because I can't write GUIs on the Atari :)

Each one takes one or more filenames on the command line, and de/compresses 
those files, creating appropriately named ones with a different 
filename extension - .tcr for compressed files, .txt for uncompressed ones.

In addition, if the decompressor is launched with an empty command lines, it 
decompresses the standard input to the standard output, so it can be used in 
shell pipelines etc.

You can use them from a GUI fairly easily too, e.g. by creating icons on the 
desktop to which you can drag-and-drop files, or by installing applications 
for file types .tcr and/or .txt.

    HISTORY  (Where's this `TCR' format from anyway?)

Ian Young originally designed a format called ZVR for a Psion text file 
viewer - see http://ww.rats.demon.co.uk/zvr/, where there's also a program 
called ZVRZ for the de/compression (including source).  Unlike most 
compression formats, which need to be decompressed right from the beginning 
each time, with ZVR you can restart anywhere, which is obviously much better 
for a text viewer.  Compression is still quite good though - average saving 
is about 50%, as compared with (very roughly) 65% for ZIP.

When Barry Childress (73510.1420@compuserve.com) came to write a text file 
viewer for the Psion Series 3, Reader3 (available on 
http://3lib.ukonline.co.uk), he adapted the ZVR format slightly to make TCR 
(Text Compression for Reader). He also included a compression program called 
TCReader - this is very much faster than Ian's ZVRZ, but only runs on a PC.

The format has become quite popular in the Psion world, so that when Jean-Luc 
Damnet (jldamnet@pca.fr) wrote his VReader5 viewer for the Series 5, he also 
included TCR support.  (Currently at http://ady.net/psion/files/vr100.zip)

Meanwhile, although you could use TCR files on a Psion, you needed a PC to 
create them, which annoyed me as I've an Atari instead.  Barry Childress 
wasn't keen on letting me have his source code, so in desperation I decided 
to write my own!  (And don't I wish I hadn't :)  Although this version uses 
some ideas from Ian's original ZVRZ, and some from interesting discussions 
with pmaud@cix.co.uk, it's all my own work, and (in my very biased opinion) 
is better than previous ones :)  So, with thanks to Ian and Peter, and 
apologies to Barry, here's a version you can compile for your machine.

But why, I hear you ask, didn't I write a Psion version?  Speed and 
convenience, but mainly coz I haven't got a C compiler for my Psion!  (Does 
some enterprising soul with a C SDK want to try porting it?)

    RESTRICTIONS  (What can I do with this?)

The code and executables are freeware - use and share them freely.  However: 
you're not allowed to make any money from them (apart from reasonable 
distribution costs etc.), and if you use my source code, you must give me 
credit. Reasonable?  (Email, postcard or monetary apreciation would be nice, 
too :)

    CONTACT  (Who do I send money to?)

Questions, comments, etc. to:

        Andrew Giddings

        gidds@cix.co.uk

        1 Pavilion Close
        Southend-on-Sea
        Essex  SS2 4TZ
        UK

    GRATUITOUS GREETINGS

Thanks to Ian Young, Barry Childress amd Jean-Luc Damnet for their programs.

Thanks and Hi to Peter Maud for explaining ZVRZ to me, and Steve Litchfield 
for putting this on 3-Lib (I hope!).