Make 1553 Data Single-Bus

#!/usr/bin/env python

"""usage: allbus.py <src> <dst> [-b]

Switch 1553 format 1 messages to the same bus. Defaults to A unless "-b" flag
is present.
"""

import sys

from chapter10 import C10


if __name__ == '__main__':

    # Parse args
    if len(sys.argv) < 3:
        print(__doc__)
        raise SystemExit
    bus = int(sys.argv[-1].lower() == '-b')
    if bus:
        src, dst = sys.argv[-3:-1]
    else:
        src, dst = sys.argv[-2:]

    # Walk through the source file and write data to the output file.
    with open(dst, 'wb') as out:
        for packet in C10(src):

            raw = bytes(packet)

            # Write non-1553 out as-is.
            if packet.data_type != 0x19:
                out.write(raw)
                continue

            # Write out packet secondary header if applicable) and CSDW.
            offset = 28
            if packet.secondary_header:
                offset += 12
            out.write(raw[:offset])

            # Walk through messages and update bus ID as needed.
            for msg in packet:
                msg.bus = bus
                packed = msg.pack()
                out.write(packed)
                offset += len(packed)

            # Write filler if needed.
            for i in range(packet.packet_length - offset):
                out.write(b'0')