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#!/usr/bin/env python3
# SPDX-FileCopyrightText: © 2024 ZeldaRET
# SPDX-License-Identifier: MIT
from __future__ import annotations
import argparse
import ipl3checksum
from pathlib import Path
import struct
from typing import BinaryIO
def round_up(n: int, shift: int) -> int:
mod = 1 << shift
return (n + mod - 1) >> shift << shift
def pad_rom(f: BinaryIO, rom_len: int):
fill_00 = round_up(rom_len, 12)
fill_FF = round_up(fill_00, 17)
f.seek(rom_len)
if fill_00 > rom_len:
f.write(b"\0" * (fill_00 - rom_len))
if fill_FF > fill_00:
f.write(b"\xFF" * (fill_FF - fill_00))
def update_checksum(f: BinaryIO, detect: bool):
rom_bytes = f.read(0x101000)
assert len(rom_bytes) == 0x101000, "Small ROM?"
# Detect CIC
if detect:
cicKind = ipl3checksum.detectCIC(rom_bytes)
if cicKind is None:
print("Not able to detect CIC, defaulting to 6105")
cicKind = ipl3checksum.CICKind.CIC_X105
else:
cicKind = ipl3checksum.CICKind.CIC_X105
# Calculate checksum
calculatedChecksum = cicKind.calculateChecksum(rom_bytes)
assert calculatedChecksum is not None, "Not able to calculate checksum"
# Write checksum
checksum_bytes = struct.pack(f">II", calculatedChecksum[0], calculatedChecksum[1])
f.seek(0x10)
f.write(checksum_bytes)
def checksummer_main():
description = "Pads a rom in-place and updates its header checksum"
parser = argparse.ArgumentParser(description=description)
parser.add_argument("rom", help="input rom filename")
parser.add_argument(
"-d",
"--detect",
action="store_true",
help="Try to detect the IPL3 binary on the ROM instead of assuming the 6105 is being used. If not able to detect the IPL3 binary then this program will default to 6105",
)
args = parser.parse_args()
rom_path = Path(args.rom)
detect: bool = args.detect
rom_len = rom_path.stat().st_size
with rom_path.open("rb+") as f:
update_checksum(f, detect)
pad_rom(f, rom_len)
if __name__ == "__main__":
checksummer_main()
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