mm/tools/decompress_baserom.py

#!/usr/bin/env python3

# SPDX-FileCopyrightText: © 2024 ZeldaRET
# SPDX-License-Identifier: CC0-1.0

from __future__ import annotations

import argparse
import hashlib
import io
from pathlib import Path
import struct
import sys

import crunch64
import ipl3checksum
import zlib

from buildtools import dmadata
from version import version_config


def decompress_zlib(data: bytes) -> bytes:
    decomp = zlib.decompressobj(-zlib.MAX_WBITS)
    output = bytearray()
    output.extend(decomp.decompress(data))
    while decomp.unconsumed_tail:
        output.extend(decomp.decompress(decomp.unconsumed_tail))
    output.extend(decomp.flush())
    return bytes(output)


def decompress(data: bytes, is_zlib_compressed: bool) -> bytes:
    if is_zlib_compressed:
        return decompress_zlib(data)
    return crunch64.yaz0.decompress(data)


def round_up(n, shift):
    mod = 1 << shift
    return (n + mod - 1) >> shift << shift


def update_crc(decompressed: io.BytesIO) -> io.BytesIO:
    print("Recalculating crc...")
    calculated_checksum = ipl3checksum.CICKind.CIC_X105.calculateChecksum(
        bytes(decompressed.getbuffer())
    )
    new_crc = struct.pack(f">II", calculated_checksum[0], calculated_checksum[1])

    decompressed.seek(0x10)
    decompressed.write(new_crc)
    return decompressed


def decompress_rom(
    file_content: bytearray,
    dmadata_start: int,
    dma_entries: list[dmadata.DmaEntry],
    is_zlib_compressed: bool,
) -> bytearray:
    rom_segments = {}  # vrom start : data s.t. len(data) == vrom_end - vrom_start
    new_dmadata = []  # new dmadata: list[dmadata.Entry]

    decompressed = io.BytesIO(b"")

    for dma_entry in dma_entries:
        v_start = dma_entry.vrom_start
        v_end = dma_entry.vrom_end
        p_start = dma_entry.rom_start
        p_end = dma_entry.rom_end
        if dma_entry.is_syms():
            new_dmadata.append(dma_entry)
            continue
        if dma_entry.is_compressed():
            new_contents = decompress(file_content[p_start:p_end], is_zlib_compressed)
            rom_segments[v_start] = new_contents
        else:
            rom_segments[v_start] = file_content[p_start : p_start + v_end - v_start]
        new_dmadata.append(dmadata.DmaEntry(v_start, v_end, v_start, 0))

    # write rom segments to vaddrs
    for vrom_st, data in rom_segments.items():
        decompressed.seek(vrom_st)
        decompressed.write(data)
    # write new dmadata
    decompressed.seek(dmadata_start)
    for dma_entry in new_dmadata:
        entry_data = bytearray(dmadata.DmaEntry.SIZE_BYTES)
        dma_entry.to_bin(entry_data)
        decompressed.write(entry_data)
    # pad to size
    padding_end = round_up(dma_entries[-1].vrom_end, 17)
    decompressed.seek(padding_end - 1)
    decompressed.write(bytearray([0]))
    # re-calculate crc
    return bytearray(update_crc(decompressed).getbuffer())


def get_str_hash(byte_array):
    return str(hashlib.md5(byte_array).hexdigest())


def check_existing_rom(rom_path: Path, correct_str_hash: str):
    # If the baserom exists and is correct, we don't need to change anything
    if rom_path.exists():
        if get_str_hash(rom_path.read_bytes()) == correct_str_hash:
            return True
    return False


def word_swap(file_content: bytearray) -> bytearray:
    words = str(int(len(file_content) / 4))
    little_byte_format = "<" + words + "I"
    big_byte_format = ">" + words + "I"
    tmp = struct.unpack_from(little_byte_format, file_content, 0)
    struct.pack_into(big_byte_format, file_content, 0, *tmp)
    return file_content


def byte_swap(file_content: bytearray) -> bytearray:
    halfwords = str(int(len(file_content) / 2))
    little_byte_format = "<" + halfwords + "H"
    big_byte_format = ">" + halfwords + "H"
    tmp = struct.unpack_from(little_byte_format, file_content, 0)
    struct.pack_into(big_byte_format, file_content, 0, *tmp)
    return file_content


def per_version_fixes(file_content: bytearray, version: str) -> bytearray:
    return file_content


def pad_rom(file_content: bytearray, dma_entries: list[dmadata.DmaEntry]) -> bytearray:
    padding_start = round_up(dma_entries[-1].vrom_end, 12)
    padding_end = round_up(dma_entries[-1].vrom_end, 17)
    print(f"Padding from {padding_start:X} to {padding_end:X}...")
    for i in range(padding_start, padding_end):
        file_content[i] = 0xFF
    return file_content


# Determine if we have a ROM file
ROM_FILE_EXTENSIONS = ["z64", "n64", "v64"]


def find_baserom(version: str) -> Path | None:
    for rom_file_ext_lower in ROM_FILE_EXTENSIONS:
        for rom_file_ext in (rom_file_ext_lower, rom_file_ext_lower.upper()):
            rom_file_name_candidate = Path(f"baseroms/{version}/baserom.{rom_file_ext}")
            if rom_file_name_candidate.exists():
                return rom_file_name_candidate
    return None


def main():
    parser = argparse.ArgumentParser(
        description="Convert a rom that uses dmadata to an uncompressed one."
    )
    parser.add_argument(
        "-v",
        "--version",
        help="Version of the game to decompress.",
        default="n64-us",
    )

    args = parser.parse_args()

    version = args.version

    baserom_dir = Path(f"baseroms/{version}")
    if not baserom_dir.exists():
        print(f"Error: Unknown version '{version}'.", file=sys.stderr)
        exit(1)

    uncompressed_path = baserom_dir / "baserom-decompressed.z64"

    config = version_config.load_version_config(version)

    dmadata_start = config.dmadata_start
    correct_str_hash = (baserom_dir / "checksum.md5").read_text().split()[0]

    if check_existing_rom(uncompressed_path, correct_str_hash):
        print("Found valid baserom - exiting early")
        return

    rom_file_name = find_baserom(version)

    if rom_file_name is None:
        path_list = [
            f"baseroms/{version}/baserom.{rom_file_ext}"
            for rom_file_ext in ROM_FILE_EXTENSIONS
        ]
        print(f"Error: Could not find {','.join(path_list)}.", file=sys.stderr)
        exit(1)

    # Read in the original ROM
    print(f"File '{rom_file_name}' found.")

    file_content = bytearray(rom_file_name.read_bytes())

    # Check if ROM needs to be byte/word swapped
    # Little-endian
    if file_content[0] == 0x40:
        # Word Swap ROM
        print("ROM needs to be word swapped...")
        file_content = word_swap(file_content)
        print("Word swapping done.")

    # Byte-swapped
    elif file_content[0] == 0x37:
        # Byte Swap ROM
        print("ROM needs to be byte swapped...")
        file_content = byte_swap(file_content)
        print("Byte swapping done.")

    file_content = per_version_fixes(file_content, version)

    dma_entries = dmadata.read_dmadata(file_content, dmadata_start)
    # Decompress
    if any(dma_entry.is_compressed() for dma_entry in dma_entries):
        print("Decompressing rom...")
        is_zlib_compressed = version in {"ique-cn", "ique-zh"}
        file_content = decompress_rom(
            file_content, dmadata_start, dma_entries, is_zlib_compressed
        )

    file_content = pad_rom(file_content, dma_entries)

    # Check to see if the ROM is a "vanilla" ROM
    str_hash = get_str_hash(file_content)
    if str_hash != correct_str_hash:
        print(
            f"Error: Expected a hash of {correct_str_hash} but got {str_hash}. The baserom has probably been tampered, find a new one",
            file=sys.stderr,
        )
        exit(1)

    # Write out our new ROM
    print(f"Writing new ROM {uncompressed_path}...")
    uncompressed_path.write_bytes(file_content)

    print("Done!")


if __name__ == "__main__":
    main()