Notices by Foone🏳️‍⚧️ (foone@digipres.club)

I've been bedridden for the last 6 months, unable to work as I try to get a surgeon and insurance lined up for my operation to let me work again.
If you could send a couple dollars, it'd really help. Time isn't on my side here, and waiting is very expensive.

https://ko-fi.com/fooneturing

Game ruined

Ugh. The Blue Prince has computer terminals that are clearly designed to be an Apple III but the floppy disks you find are 5.25" double sided disks.

The Apple III uses a single sided floppy drive!

disappointingly, the word for "floppy disk" in greek is δισκέτα, which is basically "diskette".

I was really hoping it was just δίσκος, so the greeks would be calling them floppy discuses.

people often ask me; "Foone, you're an amateur physical media historian, when is it spelled disc, and when is it disk?"

Well it's simple!
Discs grow down from the ceiling, and disks grow up from the floor.

@ned good news

So I'm working on implementing support for GameLink, which is an underdocumented protocol for talking to DOSBox, to let you grab frames and memory and submit input and such.

So I'm gonna write out some of how it works just so I'll (hopefully) understand it

The top level struct is sSharedMemoryMap_R4.

https://github.com/joncampbell123/dosbox-x/blob/921acaa2915db5ea28b2ecba520a15e42e218175/src/gamelink/gamelink.h#L108C9-L108C28

Code to refer to is here:

https://github.com/joncampbell123/dosbox-x/tree/master/src/gamelink

So it's a shared memory region and a mutex. The way it works is you hold the mutex to access the shared memory.

So, the peek interface.
https://github.com/joncampbell123/dosbox-x/blob/921acaa2915db5ea28b2ecba520a15e42e218175/src/gamelink/gamelink.h#L70C1-L77C4

It's got addr_count, addr, data. The later two being arrays.

dosbox will fill out the data values for the requested addresses.

I'm not sure how you know dosbox has filled them out.

So the way it works is that you set addr_count to how many bytes you want to read, and set the appropriate addresses in addr.
then you release the mutex and wait

a dumb-but-should-work way:
set the sSharedMemoryMap_R4.version to some other value. DOSBox-x sets it every frame (and never reads it, so it doesn't care what it is set to)

So if you read the value and it's 4, you know DOSBox-X has processed all your peeks. If it's not 4 yet, sleep a bit then lock the mutex and check again

well my first attempt at PEEKing over GameLink seems to be silently segfaulting python

I think (but I'm not 100% certain) that the addresses it wants are 32bit linear addresses. So if you're running at 16-bit DOS program (and who isn't?), you'll need to linearize your address

MapViewOfFile(shm_handle, FILE_MAP_READ, 0, 0, 0)

hey foone maybe if you want write access, you should ask for it

okay that was just a thinko.

but now I'm doing my version trick and it's not working. maybe I missed something

PermissionError: [WinError 5] Access is denied.

WHAT

okay the version trick isn't working (and I'm not sure why), but this process is successfully getting bytes out.

so GFX_EndUpdate calls OUTPUT_GAMELINK_Transfer.

OUTPUT_GAMELINK_Transfer calls GameLink::Out, which should set the values I'm looking at, including version.