Tool to read map width/height from RM2K LMU maps

lmusize.py

#!/usr/bin/env python3

def read_map(path):
    with open(path, 'rb') as file:
        header = read_slice(file)
        if header != b"LcfMapUnit":
            return
        width = None
        height = None
        while not (width and height):
            field = read_byte(file)
            data = read_slice(file)
            if field == 0x02:   # width
                width = read_int(data)
            elif field == 0x03: # height
                height = read_int(data)
            elif field == 0x51: # events, should not get here
                width = width or 20
                height = height or 15
        return width, height

def read_byte(file):
    try:
        return file.read(1)[0]
    except IndexError as err:
        raise ValueError('Expected a byte, got EOF') from err

def read_slice(file):
    length = read_byte(file)
    return file.read(length)

def read_int(data):
    value = 0
    for nibble in data:
        value = value << 7
        value = value | nibble & 0x7f;
        if not (nibble & 0x80):
            break
    return value

if __name__ == "__main__":
    from argparse import ArgumentParser
    parser = ArgumentParser(
        prog='lmusize',
        description='Get the width/height of an LMU map',
    )
    parser.add_argument('maps', metavar='MAP.lmu', nargs='+', help='Path to .lmu file(s) (RM2K map file)')
    parser.add_argument('-s', '--silent', action='store_true', help='Ignore warnings for invalid files')
    args = parser.parse_args()
    maps = args.maps
    silent = args.silent
    if len(maps) == 1:
        map = maps[0]
        if info := read_map(map):
            width, height = info
            print(f'{width=} {height=}')
            exit()
        print(f'{map=} is not a RM2K map file.')
        exit(1)
    for map in maps:
        try:
            if info := read_map(map):
                width, height = info
                print(f"{map=} {width=} {height=}")
        except ValueError:
            if not silent:
                print(f'{map=} does not have enough data; skipping')