arcRepack.py

import os
import struct
import zlib
import argparse


def main():
    parser = argparse.ArgumentParser(description='Repack extracted Dai Gyakuten Saiban .arc files')
    parser.add_argument('dir', help='the directory containing the extracted .arc and manifest.txt')
    parser.add_argument('-o', dest='outfile', help='the file name of the output .arc file')
    parser.add_argument('-f', type=int, choices=[0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
                        help='force a compression level across all files in archive')
    args = parser.parse_args()

    if args.outfile is None:
        args.outfile = args.dir + '-repacked.arc'

    if not os.path.exists(args.dir):
        print("Directory doesn't exist")
        return
    else:
        os.chdir(args.dir)

    if not os.path.isfile('manifest.txt'):
        print("manifest.txt does not exist, arc files will not work in-game if file order isn't preserved")
        return

    with open('manifest.txt', 'r') as f:
        file_list = f.readlines()

    file_entries = struct.pack('<3sxBxH4x', 'ARC', 0x11, len(file_list))
    deflated_data = ''
    file_entries_length = 0xC + 0x50 * len(file_list)

    # Round up to nearest 32 bytes
    if file_entries_length % 32 != 0:
        file_entries_length = ((file_entries_length / 32) + 1) * 32

    for filename in file_list:

        filename = filename.rstrip('\n')
        filename, cmp_lvl = filename.split(',')
        cmp_lvl = int(cmp_lvl)

        split_path = os.path.splitext(filename)[0]
        split_path = os.path.splitext(split_path)

        name_only = split_path[0]
        ext = int(split_path[1][1:], 16)

        file_entries += struct.pack('<64sI', name_only.replace('/', '\\'), ext)

        with open(filename, 'rb') as f:
            file_str = f.read()

        data_position = (file_entries_length + len(deflated_data))

        if args.f is None:
            comp = zlib.compress(file_str, cmp_lvl)
        else:
            comp = zlib.compress(file_str, args.f)

        deflated_data += comp
        real_len = len(file_str) | 0x40000000
        file_entries += struct.pack('<III', len(comp), real_len, data_position)
        print('Packing ' + filename)

    os.chdir('..')

    for i in range(len(file_entries), file_entries_length):
        file_entries += struct.pack('<B', 0)

    file_entries += deflated_data

    with open(args.outfile, 'wb') as f:
        f.write(file_entries)


main()