This scripts takes a binary file containing CCSDS packets and splits them into one file per packet. Assumes CCSDS packets always have a secondary header, and that the first 4 bytes of data are a SCLK timestamp in seconds with 2010-01-01 as epoch as per the NASA IMAP Mission spec.

PacketSplitter.py

#!/usr/bin/python

# This scripts takes a binary file containing CCSDS packets and splits them into one file per packet

# Usage > python3 PacketSplitter.py -i <InputFile> -o <outputFiles>

import datetime
import sys, getopt, os
from os.path import exists

HEADER_LENGTH = 6
SCLK_LENGTH = 4


def main(argv):
    inputfile = ""
    outputfile = ""
    helptext = "Example: python3 PacketSplitter.py -i <InputFile> -o <outputFiles>"

    # parse arguments from command line
    try:
        opts, args = getopt.getopt(argv, "hi:o:", ["ifile=", "ofile="])
    except getopt.GetoptError:
        print(helptext)
        sys.exit(2)
    for opt, arg in opts:
        if opt == "-h":
            print(helptext)
            sys.exit()
        elif opt in ("-i", "--ifile"):
            inputfile = arg
        elif opt in ("-o", "--ofile"):
            outputfile = arg

    # validate arguments
    if not exists(inputfile):
        print(f"Input file {inputfile} not found")
        sys.exit(3)

    outfilename, outfile_extension = os.path.splitext(outputfile)

    # We are ready to proceed - inform user
    inputFileSize = os.path.getsize(inputfile)
    print(f"Input file {inputfile} is {inputFileSize} bytes")

    bytesWritten = 0
    packetDone = False
    packetBytes = bytes()
    ApId = 0
    SeqCnt = 0
    sclk = 0
    length = 0
    packetTime = datetime.datetime.now()
    packetCount = 0
    outputfile1 = ""
    with open(inputfile, "rb") as inputFileStream:
        byte = inputFileStream.read(1)
        while byte:
            packetBytes += byte
            byte = inputFileStream.read(1)

            if len(packetBytes) == HEADER_LENGTH + SCLK_LENGTH:
                ApId = ((packetBytes[0] << 8) | (packetBytes[1] << 0)) & 0x7FF
                SeqCnt = ((packetBytes[2] << 8) | (packetBytes[3] << 0)) & 0x3FFF
                length = int.from_bytes(packetBytes[4:6], byteorder="big")
                sclk = int.from_bytes(packetBytes[6:10], byteorder="big")
                packetTime = datetime.datetime(
                    2010, 1, 1, 0, 0, 0, 0, tzinfo=datetime.timezone.utc
                ) + datetime.timedelta(seconds=sclk)
                outputfile1 = f'{outfilename}_{packetTime.strftime("%Y%m%d")}_{packetTime.strftime("%H%M%S")}_ApId_{hex(ApId)}_Seq_{SeqCnt}{outfile_extension}'
                print(
                    f'Packet found: APID={hex(ApId)}, SeqCnt={SeqCnt}, Length={length}, SCLK={sclk}, Time={packetTime.strftime("%Y%m%d %H%M%S")}, File={outputfile1}'
                )

            if length != 0 and len(packetBytes) == length + 1 + HEADER_LENGTH:
                packetDone = True

            if packetDone:
                if exists(outputfile1):
                    print(f'Output file {outputfile1} already exists! Quitting...')
                    sys.exit(4) 

                with open(outputfile1, "wb") as outputFileStream1:
                    outputFileStream1.write(packetBytes)
                    bytesWritten += len(packetBytes)
                    outputFileStream1.close()

                packetCount += 1
                packetDone = False
                packetBytes = bytes()
                ApId = 0
                SeqCnt = 0
                length = 0
                sclk = 0
                packetTime = datetime.datetime.now()

    inputFileStream.close()

    print(
        f"{bytesWritten} bytes written across {packetCount} files. Packet Spliiting is complete :-)"
    )


if __name__ == "__main__":
    main(sys.argv[1:])