55 lines
2.3 KiB
Org Mode
55 lines
2.3 KiB
Org Mode
#+TITLE: gamebridge
|
|
|
|
An interface between Super Mario 64 and just about anything else your heart
|
|
desires.
|
|
|
|
* High level ideas
|
|
|
|
the rust program has two threads, one is getting the inputs from $SOMEWHERE and
|
|
the other is doing the file I/O to the game
|
|
|
|
the game bridge thread has two file descriptors open, a fifo for feeding inputs
|
|
to the game and a fifo opened by the game for signaling vblanks
|
|
|
|
the game will then write a readiness signal to the rust program and read the
|
|
button data fifo
|
|
|
|
then things will progress normally
|
|
|
|
the getting the input thread of the rust program will have some logic for
|
|
telling how long ago it got liveness of the input source (explicitly vaguely
|
|
defined to allow a controller to sit there and do nothing as long as it still
|
|
exists), and then "sticking" it until, say, 10 frames have passed and then it
|
|
will block infinitely, freezing the game in place
|
|
|
|
* Goals
|
|
|
|
+ Blocking, synchronous rust as much as possible
|
|
+ unix fifos are great, let's use them
|
|
|
|
* Protocol
|
|
|
|
The protocol between the game and the bridge will be as follows (based on the
|
|
[[http://tasvideos.org/EmulatorResources/Mupen/M64.html][Mupen64 demo format]]). Two unix fifos will be created by the bridge.
|
|
|
|
The game and the bridge will both need to take care that the files are opened in
|
|
*unbuffered I/O modes*. This can be done with
|
|
=setvbuf(f, (char *)NULL, _IONBF, 0);= in C and is the default in Rust.
|
|
|
|
The first one will be called =vblank= and will then be opened by the game in
|
|
write mode when it starts. The bridge will open this fifo in read mode.
|
|
|
|
The second one will be called =input= and will be opened by the game in read
|
|
mode. The bridge will open this fifo in write mode.
|
|
|
|
On every frame, the game *MUST* write the text ="OK\n"= to the vblank fifo. This
|
|
will signal the bridge that it *MUST* write four bytes of data to the input
|
|
fifo, conforming to the [[http://tasvideos.org/EmulatorResources/Mupen/M64.html#ControllerData][Controller Data]] specification of the Mupen64 format.
|
|
This data will be interpreted by the game as actions for Mario to take.
|
|
|
|
The bridge *MUST* block on waiting for the vblank fifo to be written to by the
|
|
game and the game *MUST* block on the input fifo being written to by the bridge.
|
|
|
|
When the game is exiting, the game *SHOULD* write ="BYE"= to the vblank fifo.
|
|
When the bridge recieves a ="BYE"= message, it *MUST* exit.
|