def initialize(input_file, out_stream, compressed):
    if compressed:
        bytestream = BytesIO(input_file.read())
        input_file = GzipFile(None, "rb", fileobj=bytestream)
    gzip_stream = CompressedOutputStream(out_stream, "gzip") if compressed else None
    writer = gzip_stream if compressed else out_stream
    return input_file, writer