Calculates checksum for a pikmin 2 save file entry

calc_pikmin2_checksum.py

import struct
import sys
"""
Extract Pikmin 2 save in dolphin as .gci, open gci in a hex editor 
and search for string "PlVa" which signals the start of a save file. 
Starting with the first symbol of the string, select 0xC000 bytes 
and copy it into a separate file. Use this script with that file.
"""
try:
    # Usage: python calc_pikmin2_checksum.py <file>
    infile = sys.argv[1]
except Exception as er:
    raise RuntimeException("Not enough arguments: {0}".format(sys.argv))
    
print(infile)
with open(infile, "rb") as f:
    data = f.read()

c1 = c2 = 0
for i in range(0, len(data)-4, 2): 
    val1 = data[i]
    val2 = data[i+1]

    val = (val1 << 8) + val2

    if True:
        c1 = (c1 + val) & 0xFFFF
        c2 = (c2 + (val ^ 0xFFFF)) & 0xFFFF

if c1 == 0xFFFF: c1 = 0
if c2 == 0xFFFF: c2 = 0

# These two values together form the checksum for the save data. 
# Replace the checksum in the save data with these.
print(hex(c1), hex(c2))