Extract the data and resource forks from a MacBinary II file

macbinary2extract.py

#!/usr/bin/env python3

# extract the data and resource forks from a mac binary 2 file

import sys
import struct

def unpack(stream, fmt):
    size = struct.calcsize(fmt)
    buf = stream.read(size)
    return struct.unpack(fmt, buf)

def extract_from_stream(in_stream, data_stream, resource_stream):
    in_stream.seek(83)
    data_size = unpack(in_stream, '>i')[0]
    resource_size = unpack(in_stream, '>i')[0]
    print(data_size, resource_size)
    in_stream.seek(128)
    data_stream.write(in_stream.read(data_size))
    in_stream.seek(128 + data_size + data_size % 128)
    resource_stream.write(in_stream.read(resource_size))

def extract_from_path(in_path: str):
    data_path = in_path + '.dat'
    resource_path = in_path + '.res'
    with open(in_path, 'rb') as in_stream:
        with open(data_path, 'wb') as data_stream:
            with open(resource_path, 'wb') as resource_stream:
                extract_from_stream(in_stream, data_stream, resource_stream)

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print(f'Usage: {sys.argv[0]} [path to file]')
    else:
        extract_from_path(sys.argv[1])