B2W2 Force RNG on Game Init 1.0

-- B2W2 (U) RNG Script v1.0 --
-- written by ProjectRevoTPP --
-- based on MKDasher's scripts --
-- designed for DesMUmE v0.9.9+ --

-- DO NOT USE 32-BIT DESMUME WITH THIS SCRIPT, IT WONT WORK!--

module("mt19937", package.seeall)

-- CONFIG --

desired_seed = "0x8D133658030FC2E7"
display_config = 1 -- 0 for lua window, 1 for gui text, anything else to not print
game = 0 -- 0 for white2, 1 for black2

RNG_ADDR = 0x021FFC58-0x20*game
IVRNG_ADDR = 0x21FED68-0x20*game

------------------------------------------
-- main program below --

local UPPER_MASK = 0x80000000 -- most significant w-r bits
local LOWER_MASK = 0x7fffffff -- least significant r bits

local mt = {} -- the array for the state vector
local NUM = 624
local M = 397

desired_seed_1 = string.sub(desired_seed, 0, 10) -- upper
desired_seed_2 = "0x" .. string.sub(desired_seed, 11, 18) -- lower

function FramesAdvance(nframes)
	for frame = 1, nframes do
		emu.frameadvance()
	end
end

function drawguitext(rng2, rng1)
	gui.text(1,10,string.format("Current: %08X%08X",rng2,rng1))
end

-- initializes mt[N] with a seed
function randomseed(s)
s = bit.band(s, 0xffffffff)
mt[1] = s
for i = 1, NUM - 1 do
-- s = 1812433253 * (bit.bxor(s, bit.rshift(s, 30))) + i
s = bit.bxor(s, bit.rshift(s, 30))
local s_lo = bit.band(s, 0xffff)
local s_hi = bit.rshift(s, 16)
local s_lo2 = bit.band(1812433253 * s_lo, 0xffffffff)
local s_hi2 = bit.band(1812433253 * s_hi, 0xffff)
s = bit.bor(bit.lshift(bit.rshift(s_lo2, 16) + s_hi2, 16),
bit.band(s_lo2, 0xffff))
-- s = bit.band(s + i, 0xffffffff)
local s_lim = -bit.tobit(s)
-- assumes i<2^31
if (s_lim > 0 and s_lim <= i) then
s = i - s_lim
else
s = s + i
end
mt[i+1] = s
-- See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier.
-- In the previous versions, MSBs of the seed affect
-- only MSBs of the array mt[].
-- 2002/01/09 modified by Makoto Matsumoto
end
mti = NUM
end

local mag01 = { 0, MATRIX_A } -- mag01[x] = x * MATRIX_A for x=0,1

function writemersennetable(seed)
local N
randomseed(seed)

print("Writing mersenne table...")
for N = 1, 624 do
memory.writedword(IVRNG_ADDR + (4 * (N - 1)), mt[N])
N = N + 1
end
print("Write complete.")

end

last_known_rng_value_1 = 0; -- set initial local rng to 0
last_known_rng_value_2 = 0; -- set initial local rng to 0

emu.reset() -- reset the game.

FramesAdvance(30) -- wait for the first seed update before forcing

local rng1 = memory.readdword(RNG_ADDR)
local rng2 = memory.readdword(RNG_ADDR + 4)
print(string.format("Initial RNG seed: %08x%08x", rng2, rng1))

-- WARNING: does not support 32-bit! --
-- write the forced seed and backup. --
memory.writedword(RNG_ADDR, desired_seed_2)
memory.writedword(RNG_ADDR + 4, desired_seed_1)

last_known_rng_value_1 = desired_seed_1
last_known_rng_value_2 = desired_seed_2

local mtrng = memory.readdword(IVRNG_ADDR)

print(string.format("Initial IVRNG: %08x", mtrng))
print("RNG seed to be injected is: ", desired_seed)

-- force mersenne table. --
writemersennetable(desired_seed_1)
mtrng = memory.readdword(IVRNG_ADDR)
print(string.format("IVRNG After updating: %08x", mtrng))
print(string.format("RNG seed injected: %08x%08x", desired_seed_1, desired_seed_2))

-- do main loop. --
repeat
local rng1 = memory.readdword(RNG_ADDR)
local rng2 = memory.readdword(RNG_ADDR + 4)

if rng1 ~= last_known_rng_value_1 then
    if rng2 ~= last_known_rng_value_2 then
		if display_config == 0 then
			print(string.format("Current: %08x%08x", rng2, rng1))
		end
		last_known_rng_value_1 = rng1
		last_known_rng_value_2 = rng2
	end
end

if display_config == 1 then
	drawguitext(rng2, rng1)
end

emu.frameadvance()
until false

gui.register(drawguitext)