Majora's Mask - char_checker

-- char_checker.lua
--
-- Automate the process of checking whether or not a printed
-- character will crash Majora's Mask (U) on Bizhawk. Can be
-- swapped over to test japanese characters on (J) by changing
-- the writes to be 16 bit as well as finding the new addresses
--
-- Author: @Faschz
-- Created: April 6th, 2019

CHARACTER_ADDR = 0x1D0714
TEXTBOX_ADDR = 0x3FD355
TIMER_ADDR = 0x1F9F83

for c=0, 255 do
    -- Recover from any crashes by loading a state about to select
    -- the soaring location for Great Bay Coast
    savestate.loadslot(2)

    -- Set the character in the message table
    mainmemory.writebyte(CHARACTER_ADDR, c)

    -- Select the soaring location
    joypad.set({["A"] = true}, 1)
    emu.frameadvance()
    joypad.set({["A"] = false}, 1)

    -- Wait until the textbox appears and changes the address
    while c ~= mainmemory.readbyte(TEXTBOX_ADDR) do
        emu.frameadvance()
    end

    -- Check if the game is crashed by reading the frame count
    start = mainmemory.readbyte(TIMER_ADDR)
    is_crashed = true

    --3 frames work, but lets be on the safe side
    for frame=0, 5 do
        if start ~= mainmemory.readbyte(TIMER_ADDR) then
            is_crashed = false
            break
        end
        emu.frameadvance()
    end

    if is_crashed then
        print(c)
    end
end

print("DONE!")