xz/dos

XZ Utils on DOS
===============

Introduction

    This document explains how to build XZ Utils for DOS using DJGPP.
    The resulting binaries should run at least on various DOS versions
    and under Windows 95/98/98SE/ME, which cannot run the Windows version
    of XZ Utils.

    This is currently experimental and has got very little testing.


Getting and Installing DJGPP

    You may use <http://www.delorie.com/djgpp/zip-picker.html> to help
    deciding what to download, but as of writing (2009-02-13) that may
    not be the most convenient way taking into account what components
    are actually required to build XZ Utils. However, using the
    zip-picker can still be worth doing to get nice short summary of
    installation instructions (they can be found from readme.1st too).

    For more manual method, first select a mirror from
    <http://www.delorie.com/djgpp/getting.html>. You need
    the following files:

        unzip32.exe
        beta/v2/djdev204.zip
        v2gnu/bnu219b.zip
        v2gnu/gcc432b.zip
        v2gnu/mak3791b.zip
        v2gnu/sed415b.zip
        v2misc/csdpmi5b.zip

    If newer versions are available, probably you should try them first.
    Note that djdev203.zip is too old to build XZ Utils; you need at
    least djdev204.zip. Also note that you want csdpmi5b.zip even if you
    run under Windows or DOSEMU, because the XZ Utils Makefile will embed
    cwsdstub.exe to the resulting binaries.

    See the instructions in readme.1st found from djdev204.zip. Here's
    a short summary, but you should still read readme.1st.

        C:\> mkdir DJGPP
        C:\> cd DJGPP
        C:\DJGPP> c:\download\unzip32 c:\download\djdev204.zip
        C:\DJGPP> c:\download\unzip32 c:\download\bnu219b.zip
        C:\DJGPP> c:\download\unzip32 c:\download\gcc432b.zip
        C:\DJGPP> c:\download\unzip32 c:\download\mak3791b.zip
        C:\DJGPP> c:\download\unzip32 c:\download\sed415b.zip
        C:\DJGPP> c:\download\unzip32 c:\download\csdpmi5b.zip

        C:\DJGPP> set PATH=C:\DJGPP\BIN;%PATH%
        C:\DJGPP> set DJGPP=C:\DJGPP\DJGPP.ENV

    You may want to add the last two lines into AUTOEXEC.BAT or have,
    for example, DJGPP.BAT which you can run before using DJGPP.

    Make sure you use completely upper case path in the DJGPP environment
    variable. This is not required by DJGPP, but the XZ Utils Makefile is
    a bit stupid and expects that everything in DJGPP environment variable
    is uppercase.


Building

    Just run "make" in this directory (the directory containing this
    README). You should get liblzma.a, xz.exe, xzdec.exe, and
    lzmadec.exe. Of these, probably xz.exe is the only interesting one.

    Note: You need to have an environment that supports long filenames.
    Once you have built XZ Utils, the resulting binaries can be run
    without long filename support.


Additional Make Flags and Targets

    You may want to try some additional optimizations, which may or
    may not make the code faster (and may or may not hit possible
    compiler bugs more easily):

        make CFLAGS="-O3 -fomit-frame-pointer -funroll-loops"

    If you want to enable assertions (the assert() macro), use DEBUG=1.
    You may want to disable optimizations too if you plan to actually
    debug the code. Never use DEBUG=1 for production builds!

        make DEBUG=1 CFLAGS="-g -O0"


Bugs

    "make clean" may remove src/xz/hardware.c when it tries to remove
    src/xz/hardware-fixed.c. This is probably a bug somewhere in the
    DOS environment I use. Maybe it tries truncated 8.3 name first and
    since that gives a name of an existing file, it doesn't look for
    long filename.

    "xz -fc /dev/tty" hangs at least in DOSEMU and cannot be interrupted
    by pressing C-c. Maybe xz should never accept non-regular files on
    DOS even when --force is used.

    Using different memory usage limit for encoding and decoding doesn't
    make sense under pure DOS. Maybe it is still OK when running under
    Windows.

    The progress indicator of "xz -v" doesn't get updated when running
    under Dosbox, but it works in DOSEMU. I currently (2009-02-13) don't
    know if it works in other environments.

    Report bugs to <lasse.collin@tukaani.org> (in English or Finnish).