def get_prg_addresses(fileInfo, args, handle):
# get PRG ROM addresses affected by code in file1
(cpuAddr, repl, comp) = qneslib.game_genie_decode(args.code)
if comp is None and qneslib.is_prg_bankswitched(fileInfo["prgSize"],
fileInfo["mapper"]):
sys.exit(
"Six-letter codes not supported because file1 uses PRG ROM bankswitching."
)
prgBankSize = qneslib.min_prg_bank_size(fileInfo["prgSize"],
fileInfo["mapper"])
prgAddresses = set()
if comp is None or comp != repl:
if comp is None:
# 6-letter code (old value must not equal replace value)
validValues = set(range(0x100)) - {repl}
else:
# 8-letter code (old value must equal compare value)
validValues = {comp}
for prgAddr in qneslib.address_cpu_to_prg(cpuAddr, prgBankSize,
fileInfo["prgSize"]):
handle.seek(fileInfo["prgStart"] + prgAddr)
if handle.read(1)[0] in validValues:
prgAddresses.add(prgAddr)
return prgAddresses
def get_fake_compare_value(handle, args):
# get a fake compare value from file1 for user's six-letter code
cpuAddr = qneslib.game_genie_decode(args.code)[0]
fileInfo = qneslib.ines_header_decode(handle)
prgAddr = cpuAddr & (fileInfo["prgSize"] - 1)
handle.seek(fileInfo["prgStart"] + prgAddr)
return handle.read(1)[0]
def print_results(cpuAddresses, compareValue, args):
# print codes with new addresses (sort by difference from original address)
(origCpuAddr, replaceValue) = qneslib.game_genie_decode(args.code)[:2]
cpuAddresses = sorted(cpuAddresses)
cpuAddresses.sort(key=lambda addr: abs(addr - origCpuAddr))
print(
"Game Genie codes for file2 (try the first one first):", ", ".join(
qneslib.game_genie_encode(a, replaceValue, compareValue)
for a in cpuAddresses))
def print_decoded_code(args):
(addr, repl, comp) = qneslib.game_genie_decode(args.code)
comp = "none" if comp is None else f"{comp:02x}"
print(
f"Code: CPU address={addr:04x}, replace value={repl:02x}, compare value={comp}"
)
def parse_arguments():
# parse command line arguments using argparse
parser = argparse.ArgumentParser(
description=
"Convert an NES Game Genie code from one version of a game to another using "
"both iNES ROM files (.nes). Technical explanation: decode the code; find out PRG ROM "
"addresses affected in file1; see what's in and around them; look for similar bytestrings "
"in file2's PRG ROM; convert the addresses back into CPU addresses; encode them into "
"codes.")
parser.add_argument(
"-s",
"--slice-length",
type=int,
default=4,
help=
"How many PRG ROM bytes to compare both before and after the relevant byte (that is, "
"total number of bytes compared is twice this value, plus one). Fewer bytes will be "
"compared if the relevant byte is too close to start or end of PRG ROM. 1 to 20, "
"default=4. Decrease to get more results.")
parser.add_argument(
"-d",
"--max-different-bytes",
type=int,
default=1,
help=
"Maximum number of non-matching bytes allowed in each pair of PRG ROM slices to "
"compare. (The relevant byte must always match.) Minimum=0, default=1, maximum=twice "
"--slice-length, minus one. Increase to get more results.")
parser.add_argument(
"-v",
"--verbose",
action="store_true",
help=
"Print more information. Note: all printed numbers are hexadecimal.")
parser.add_argument(
"code",
help=
"An NES Game Genie code that is known to work with file1. Six-letter codes are not "
"allowed if file1 uses PRG ROM bankswitching.")
parser.add_argument(
"file1",
help=
"An iNES ROM file (.nes) to read. The game your code is known to work with."
)
parser.add_argument(
"file2",
help=
"Another iNES ROM file (.nes) to read. The equivalent code for this game will be "
"searched for.")
args = parser.parse_args()
if not 1 <= args.slice_length <= 20:
sys.exit("Invalid --slice-length.")
if not 0 <= args.max_different_bytes < 2 * args.slice_length:
sys.exit("Invalid --max-different-bytes.")
if qneslib.game_genie_decode(args.code) is None:
sys.exit("Invalid code.")
if not os.path.isfile(args.file1):
sys.exit("file1 not found.")
if not os.path.isfile(args.file2):
sys.exit("file2 not found.")
return args
def main():
args = parse_arguments()
if args.verbose:
print_decoded_code(args)
compareValue = qneslib.game_genie_decode(args.code)[2]
# get PRG addresses, PRG slices and optionally a fake compare value from file1
try:
with open(args.file1, "rb") as handle:
fileInfo = qneslib.ines_header_decode(handle)
if fileInfo is None:
sys.exit("file1 is not a valid iNES ROM file.")
prgAddresses = get_prg_addresses(fileInfo, args, handle)
if not prgAddresses:
sys.exit("Your code seems to affect file1 in no way.")
slices = set(get_prg_slices(prgAddresses, fileInfo, args, handle))
if compareValue is None:
compareValue = get_fake_compare_value(handle, args)
if args.verbose:
print(f"Using fake compare value: {compareValue:02x}")
except OSError:
sys.exit("Error reading file1.")
if args.verbose:
print("PRG addresses in file1:",
", ".join(f"{addr:04x}" for addr in sorted(prgAddresses)))
print_slices(slices, compareValue)
# find PRG addresses in file2
try:
with open(args.file2, "rb") as handle:
fileInfo = qneslib.ines_header_decode(handle)
if fileInfo is None:
sys.exit("file2 is not a valid iNES ROM file.")
prgAddresses = set(
find_slices_in_prg(handle, slices, compareValue, args))
except OSError:
sys.exit("Error reading file2.")
if not prgAddresses:
sys.exit(
"file2 contains nothing similar to what your code affects in file1."
)
if args.verbose:
print("PRG address matches in file2:",
", ".join(f"{a:04x}" for a in sorted(prgAddresses)))
# convert PRG addresses into CPU addresses
cpuAddresses = set()
prgBankSize = qneslib.min_prg_bank_size(fileInfo["prgSize"],
fileInfo["mapper"])
for prgAddr in prgAddresses:
cpuAddresses.update(qneslib.address_prg_to_cpu(prgAddr, prgBankSize))
if args.verbose:
print("CPU address matches in file2:",
", ".join(f"{a:04x}" for a in sorted(cpuAddresses)))
# if file2 not bankswitched, discard compare value to output six-letter codes
if not qneslib.is_prg_bankswitched(fileInfo["prgSize"],
fileInfo["mapper"]):
compareValue = None
print_results(cpuAddresses, compareValue, args)
import sys
import qneslib # qalle's NES library, https://github.com/qalle2/nes-util
if len(sys.argv) == 2:
# decode Game Genie code
values = qneslib.game_genie_decode(sys.argv[1])
if values is None:
sys.exit("Invalid Game Genie code.")
# reencode to get canonical form
code = qneslib.game_genie_encode(*values)
elif 3 <= len(sys.argv) <= 4:
# encode Game Genie code
try:
values = [int(n, 16) for n in sys.argv[1:]]
except ValueError:
sys.exit("Invalid hexadecimal integers.")
code = qneslib.game_genie_encode(*values)
if code is None:
sys.exit("Hexadecimal integers out of range.")
# redecode to get canonical form
values = qneslib.game_genie_decode(code)
else:
sys.exit(
"Encode and decode NES Game Genie codes. Argument: six-letter code, eight-letter code, "
"AAAA RR or AAAA RR CC (AAAA = address in hexadecimal, RR = replacement value in "
"hexadecimal, CC = compare value in hexadecimal)."
)
comp = "none" if values[2] is None else f"0x{values[2]:02x}"
print(
f"{code}: CPU address = 0x{values[0]:04x}, replace value = 0x{values[1]:02x}, compare value = "
import os, sys
import qneslib # qalle's NES library, https://github.com/qalle2/nes-util
# read args
if len(sys.argv) != 3:
sys.exit(
"Find the PRG ROM addresses affected by an NES Game Genie code in an iNES ROM file (.nes). "
"Args: file code")
(filename, code) = sys.argv[1:]
# decode the code
values = qneslib.game_genie_decode(code)
if values is None:
sys.exit("Invalid code.")
(cpuAddr, replaceValue, compareValue) = values
if not os.path.isfile(filename):
sys.exit("File not found.")
try:
with open(filename, "rb") as handle:
# get file info
fileInfo = qneslib.ines_header_decode(handle)
if fileInfo is None:
sys.exit("Invalid iNES ROM file.")
# get PRG ROM addresses
prgAddresses = []
if compareValue is None or compareValue != replaceValue:
if compareValue is None:
# 6-letter code (old value must not equal replace value)
validValues = set(range(0x100)) - {
