MAME .inp importer

Pearl made a MAME+libTAS movie, which I used to create a MAME replay file (-record file.inp / -playback file.inp). I ran that file in actual MAME while running a script that dumps bizhawk inputs:

fields = {
	{ name = "|"},
	{ tag = ":COIN",    mask = 0x1,    name = "Coin 1",          value = ".", mnemonic = "C" },
	{ tag = ":COIN",    mask = 0x2,    name = "Coin 2",          value = ".", mnemonic = "C" },
	{ tag = ":SYSTEM",  mask = 0x1,    name = "1 Player Start",  value = ".", mnemonic = "1" },
	{ tag = ":SYSTEM",  mask = 0x2,    name = "2 Players Start", value = ".", mnemonic = "2" },
	{ tag = ":SYSTEM",  mask = 0x8,    name = "Service 1",       value = ".", mnemonic = "s" },
	{ tag = ":SYSTEM",  mask = 0x4,    name = "Service Mode",    value = ".", mnemonic = "S" },
	{ name = "|"},
	{ tag = ":INPUTS",  mask = 0x10,   name = "P1 Button 1",     value = ".", mnemonic = "1" },
	{ tag = ":INPUTS",  mask = 0x20,   name = "P1 Button 2",     value = ".", mnemonic = "2" },
	{ tag = ":INPUTS",  mask = 0x40,   name = "P1 Button 3",     value = ".", mnemonic = "3" },
	{ tag = ":INPUTS",  mask = 0x2,    name = "P1 Down",         value = ".", mnemonic = "D" },
	{ tag = ":INPUTS",  mask = 0x4,    name = "P1 Left",         value = ".", mnemonic = "L" },
	{ tag = ":INPUTS",  mask = 0x8,    name = "P1 Right",        value = ".", mnemonic = "R" },
	{ tag = ":INPUTS",  mask = 0x1,    name = "P1 Up",           value = ".", mnemonic = "U" },
	{ name = "|"},
	{ tag = ":INPUTS",  mask = 0x1000, name = "P2 Button 1",     value = ".", mnemonic = "1" },
	{ tag = ":INPUTS",  mask = 0x2000, name = "P2 Button 2",     value = ".", mnemonic = "2" },
	{ tag = ":INPUTS",  mask = 0x4000, name = "P2 Button 3",     value = ".", mnemonic = "3" },
	{ tag = ":INPUTS",  mask = 0x200,  name = "P2 Down",         value = ".", mnemonic = "D" },
	{ tag = ":INPUTS",  mask = 0x400,  name = "P2 Left",         value = ".", mnemonic = "L" },
	{ tag = ":INPUTS",  mask = 0x800,  name = "P2 Right",        value = ".", mnemonic = "R" },
	{ tag = ":INPUTS",  mask = 0x100,  name = "P2 Up",           value = ".", mnemonic = "U" },
	{ name = "|"}
}

local function getscreen()
    for k,v in pairs(manager.machine.screens) do return v end
end

local screen = getscreen()
local curframe = -1

local function log(s, name)
    logfile = io.open(name, "ab")
    logfile:write(s)
    logfile:close()
end

function framecount()
	if curframe == screen:frame_number() then return end	
	local line = ""	
	for i = 1, #fields do
		local char0 = "!"
		if fields[i].name ~= "|" then
			local state = manager.machine.ioport.ports[fields[i].tag]:read()
			char0 = (state & fields[i].mask == 0) and fields[i].mnemonic or "_"
		end
		line = line .. char0
	end	
	log(line .. "\n", "log.txt")	
	curframe = screen:frame_number()
end

emu.register_frame_done(framecount)

And barring a single place where a frame had to be inserted, it also synced on MAMEHawk. Which made me think it'd be not too hard to come up with a Hawk side .inp importer, because MAME replays use to sync across versions quite well.

The main advantage of such an importer is crazy amounts of existing MAME replays over the internet, so one could use them as a foundation for a TAS, or any kind of project that could benefit from Hawk tools. Also easier to encode them with Hawk than with MAME, that only dumps uncompressed. All that would be a good selling point of MAMEHawk IMO.

https://github.com/mamedev/mame/blob/dd355e4d68d77fa47a07ee26170a21f3d517ee22/src/emu/ioport.cpp#L2806

Bonus points if MAME-RR replays could also be imported.

https://github.com/TASEmulators/mame-rr/blob/14cc1b04768c56d0b98b0f0f506b72b711238f31/mame-rr/src/emu/inptport.c#L4352

Start by reading the referenced MAME ioport.cpp and MAME-RR inptport.c implementations to understand their .inp replay formats and compare them with MAMEHawk behavior. Done means BizHawk can import MAME replay files and preserve synchronization, with MAME-RR support as an optional extension.