The TH04/TH05 BGM/SE mode setup is a good example for code where
different structure field offsets will vanish completely upon reverse-
engineering. If we continued to use the per-game ID string as the
variable name, we'd only have another game-specific "difference" there.
Part of P0065, funded by Touhou Patch Center.
Funny how the actual scores are stored as little-endian gaiji strings
in the bold font, yet never actually used as such.
Part of P0063, funded by -Tom-.
So many things named `score_*`, so many things named `hiscore_*`…
Let's go with `scoredat_*`, which clearly indicates that this stuff is
saved into a file, while still being only 8 characters.
Part of P0063, funded by -Tom-.
At least wherever Turbo C++ and master.lib want us to use a
non-pointer, since both use uint16_t for segment values throughout
their APIs instead of the more sensible void __seg*. Maybe, integer
arithmetic on segment values was widely considered more important than
dereferencing?
*Finally*. We already used `(unsigned) int` in quite a few places where
we actually want a 16-bit value, which was bound to annoy future port
developers.
Not applying this leak to TH03 since it would have more than one
`key_det` variable, resulting in names that are as much fanfiction as
the current ones…
Yup, function parameters that can clearly be identified as coordinates
are by far the fastest way to raise the calculated position
independence percentage. Kinda makes it sound like useless work, which
I'm only doing because it's dictated by some counting algorithm on a
website, but decompilation will want to un-hex all of these values
anyway. We're merely doing that right now, across all games.
Part of P0058, funded by -Tom-.
That should make this convoluted copypasta a bit easier to read. And
sure, I could have done something about the loop as well, but
SHOT_FUNC_INIT already hides enough control flow behind a macro…
Part of P0037, funded by zorg.
With both 16- and 32-bit build parts soon having full dependency
tracking, having more small includes wins out over having fewer, larger
ones – and also, over having to fix tons of macro conflicts that stem
from most .inc files assuming the context of the big .asm files.
Case in point, including ReC98.inc doesn't work right now without
defining a .MODEL, which is counter-productive for ASM compilation
units.
Part of P0035, funded by zorg.
The TH02 version is a piece of cake…
… but TH04 starts turning it into this un-decompilable piece of
unnecessarily micro-optimized ZUN code. Couldn't have chosen anything
better for the first separate ASM translation unit.
Aside from now having to convert names of exported *variables* to
uppercase for visibility in ASM translation units, the most notable
lesson in this was the one about avoiding fixup overflows. From the
Borland C++ Version 4.0 User's Guide:
"In an assembly language program, a fixup overflow frequently
occurs if you have declared an external variable within a
segment definition, but this variable actually exists in a
different segment."
Can't be restated often enough.
Completes P0032, funded by zorg.
Rule of thumb going forward: Everything that emits data is .asm,
everything that doesn't is .inc.
(Let's hope that th01_reiiden_2.inc won't exist for that much longer!)
Part of P0032, funded by zorg.
Many thanks to http://bytepointer.com/tasm/index.htm for providing a
better searchable resource for TASM's default `LEA imm16` → `MOV imm16`
optimization, which we initially had to hack around here.
Funded by -Tom-.
Yes, you're reading that correctly. If the cursor is at 255, reading a
16-bit value will fill the upper 8 bits with the neighboring cursor
value, which always is 0xFF.
Funded by -Tom-.
Which is the last step on the way to completely position-independent
code, with no random hex numbers that should have been data pointers,
but weren't automatically turned into data pointers by IDA because
they're only ever addressed in the indirect fashion of
mov bx, [bp-array_index]
mov ax, [bx+0D00h] ; 0D00h is obviously an array of some sort
Removing all of these makes it practicable to add or delete code without
breaking the game in the process. Basic "modding", so to speak.
Automatically catching all possible cases where this happens actually
amounts to emulating the entire game, and *even then*, we're not
guaranteed that the *size* of the array just falls out as a byproduct
of this emulation and the tons of heuristics I would have thrown on top
of that. ZUN hates proper bounds checking and the correct size of each
array may simply never be implied anywhere.
So, rather than going through all that trouble of that (and hell, I
haven't even finished *parsing* this nasty MASM assembly format), and
since nothing really has happened in this project for almost two years,
I chose to just turn this into a text manipulation issue and figure out
the rest manually. Yeah, quick and dirty, and it probably won't scale if
I ever end up doing the same for PC-98 Policenauts, but it'd better work
at least for the rest of PC-98 Touhou.
Trying to do one of those per day from now on. Probably won't make it
due to the reverse-engineering effort required for the big main
executables of each game, but it'd sure be cool if I did.
This, hands down, has been the single worst stretch of decompilation so far.
Three extremely difficult functions that each still required inline assembly.
And no, this didn't even work out with any of the optimization features in
Borland C++ that aren't included in Turbo C++.
nmlgc