1
0
Fork 0
mirror of https://github.com/notwa/mm synced 2024-11-05 02:39:02 -08:00
mm/chksum.py

98 lines
2.3 KiB
Python
Executable file

#!/bin/python
# fixes the checksums in a Majora's Mask savefile for Bizhawk
# note: copies are ignored and overwritten, so don't bother editing them.
import sys
import struct, array
lament = lambda *args, **kwargs: print(*args, file=sys.stderr, **kwargs)
R2 = lambda data: struct.unpack('>H', data)[0]
W2 = lambda data: struct.pack('>H', data)
save_1 = 0x20800
save_2 = 0x24800
owl_1 = 0x28800
owl_2 = 0x30800
save_1_copy = 0x22800
save_2_copy = 0x26800
owl_1_copy = 0x2C800
owl_2_copy = 0x34800
def calc_sum(data):
chksum = 0
for b in data:
chksum += b
chksum &= 0xFFFF
return chksum
def fix_sum(f, addr, owl=False):
sum_pos = 0x100A
f.seek(addr)
data = f.read(0x2000)
chksum = calc_sum(data[:sum_pos])
if owl and data != b'\x00'*0x2000:
chksum += 0x24 # don't know why
chksum &= 0xFFFF
f.seek(addr + sum_pos)
old_chksum = R2(f.read(2))
f.seek(addr + sum_pos)
f.write(W2(chksum))
lament('{:04X} -> {:04X}'.format(old_chksum, chksum))
def copy_save(f, addr, addr2):
sum_pos = 0x100A
f.seek(addr)
data = f.read(0x2000)
f.seek(addr2)
f.write(data)
def delete_save(f, addr):
f.seek(addr)
f.write(b'\x00'*0x2000)
def swap_order(f, size='H'):
f.seek(0)
a = array.array(size, f.read())
a.byteswap()
f.seek(0)
f.write(a.tobytes())
def run(args):
args = args[1:]
if len(args) == 0:
lament("TODO: convert stdin to stdout")
return 0
for fn in args:
with open(fn, 'r+b') as f:
# dumb way to determine byte order
endian = 'big'
f.seek(0x10000)
if f.read(4) != b'\x03\x00\x03\x00':
endian = 'little'
if endian == 'little':
swap_order(f, 'L')
fix_sum(f, save_1)
fix_sum(f, save_2)
fix_sum(f, owl_1, owl=True)
fix_sum(f, owl_2, owl=True)
copy_save(f, save_1, save_1_copy)
copy_save(f, save_2, save_2_copy)
copy_save(f, owl_1, owl_1_copy)
copy_save(f, owl_2, owl_2_copy)
if endian == 'little':
swap_order(f, 'L')
return 0
if __name__ == '__main__':
ret = 0
try:
ret = run(sys.argv)
except KeyboardInterrupt:
sys.exit(1)
sys.exit(ret)