nancygold's Journal

Stronghold Decompilation Progress
https://github.com/NancyAurum/dest

The progress is steady. Even got a bit into the game logic, since I was
trying to map all the C-strings references and name all the overlays.
Still need to reverse the audio and video code.

One annoying thing is Github converting line endings, which breaks scripts,
like .bat files, should be in crlf. Is removing everything from .gitattributes
and then adding there single line

* -text

The forces treating all files as binary.

Then one has to run:

git add --renormalize .

That cancel the damage git already did to our files.
- Why isn't that default?
- Because Linux Torvalds is not smarter than his Linux.
See https://www.reddit.com/r/git/comments/s8kr76/how_to_configure_git_to_never_modify_a_line_ending/

The most interesting place is the 3168:0000 exit procedure.
It asks providing the error number to Cathryn.
Meaning Cathryn Mataga was out of the closet at the time of development.

void stExit(int n) {
  if (n && n < E_STRING) { //just in case we are still in text mode
    printf("\n\rError %d\n", n);
    biosReadKey();
  }
  biosVideoCall(0x0,0x3); /* Restore video to the 80x25 text mode */
  if (!n) { /* No error; just exit */ }
  else if (n < E_STRING) {
    printf(("Error %d %d.  (Give Cathryn BOTH numbers.)\n", GGameState, n);
  } else {
    printf("%s\n", GErrorStrings[n-E_STRING]);
  }
  if (CFG_Mice) miceDisableHandler();
  if (MusRunning) midMidiStop();
  if (MIDHandle) audio_done((void _seg*)MIDHandle);
  if (DIGHandle) audio_done((void _seg*)DIGHandle);
  if (FMStrongDat >= 0) fmClose(FMStrongDat);
  xmsFree();
  emsFree();
  chpath(GOriginalDir);
  if (n) exit(0x80);
  exit(0);
}

During the DOS times, games were expected to handle the audio drivers.
Stronghold uses the 3rd party driver libraries, called MIDPAK and DIGPAK.
These were recently open sourced by their author:
https://github.com/jratcliff63367/digpak

There are two of these driver packs, one for sound effects and another for music
in MIDI format. That because music in uncompressed form takes hundreds of
megabytes, while typical DOS hard drive had just 40MB during the times of
Stronghold. The CDs with audio tracks were not popular enough and
compressed audio was too resource intensive to play and rather low quality.

So the solution was to synthesize music in real time. And that required
hardware acceleration, since the x86 was too weak to do it in software.
Still audio effects are impossible to synthesize with anything but
the modern AI modelling. So we have a separate sfx drivers for a set of
audio cards, some of which can play only PCM audio. Additionally,
many music cards were unable to play PCM so some systems had two cards.

Other interesting note: the game exe can take an argument: "grab" or "debug".
The "debug" turns on a few keys, implemented by 2e25:0adf processKey() routine.
Among them is the ability to show additional info, like the game's world seed,
as well as various cheats, like increasing character levels. The "grab" is like
debug but apparently created the STRONG.DAT file from a the external
files on a Novel Netware share. That is hinted by the network aware file code,
where the game installs a custom handler and waits for the file to be available.

Novel was similar to the NFS or Samba shares, but ran over IPX/SPX.
Don't pass the "grab" option to the game, or you're up to a nasty surprise.
It will erase your STRONG.DAT, but wont create a new one, since there are no
new source files.

My theory that each overlay corresponds to a separate file was correct.
These are good news, since everything is nicely organized for us,
map areas in a Zelda game, connected to a central hub.
But it will take some time till I name every file in there,
not speaking about decompiling them.

Current Mood: amused