ex_packet_extract.py

"""
This example extracts the packet described by the define_packet example.  If
that example hasn't run, you will need to do that now.  The file that is
created must be located where this program can find it.
The table below shows what is defined in the packet:
Name        Data Type           Size    Notes
Version     unsigned integer    4       Should always be zero
PktId       unsigned integer    12      For this packet, the value is 54
PktLen      unsigned integer    16      Length of packet after this point
PktCnt      unsigned integer    8       Packet counter
Time        system time         32      A.k.a. DT_UNIX_TIME
IntParam    signed integer      16      First data parameter
UintParam   unsigned integer    32      Three consecutive values
FloatParam  double              64      Little-endian floating point
StrParam    string              800     Varible length string
Checksum    unsigned integer    32      CRC-32 checksum
"""
import trek
 
 
def main() -> None:
    """
    Main Routine
    """
 
    try:
 
        # NOTE: There is only minimal error checking shown in the code below in
        # order to simplify the example.  In general, only the first time a
        # method is used will the error handling be in this example.  You should
        # always check the returned value when one is available to ensure proper
        # operation of the code.  Error handling for this example is to exit on
        # error.
        pkt = trek.Packet()
 
        # Read in the packet file.
        pkt.load_file("my_file.xml")
 
        # After loading a packet, you must create the 'map' that allows parameter lookup.
        pkt.create_global_packet_map()
 
        #  Normally you would extract a packet that came in from the network or
        #  some other interface.  Since this is a simple example a buffer is shown
        #  below already popluated with data that is valid (including the
        #  checksum).
        buf = bytearray(100)
        buf_size: int = 0
 
        buf[0] = 0x00  # Version = 0
        buf[1] = 0x36  # PktId = 54
        buf[2] = 0x00  # PktLen = 36 (40 - 4 byte offset)
        buf[3] = 0x24
        buf[4] = 0xFE  # PktCnt = 254
        buf[5] = 0x53  # Time = 2014-02-28 21:57:47
        buf[6] = 0x11
        buf[7] = 0x06
        buf[8] = 0x5B
        buf[9] = 0xFF  # IntParam = -1
        buf[10] = 0xFF
        buf[11] = 0x00  # UintParam(1) = 255
        buf[12] = 0x00
        buf[13] = 0x00
        buf[14] = 0xFF
        buf[15] = 0x00  # UintParam(2) = 256
        buf[16] = 0x00
        buf[17] = 0x01
        buf[18] = 0x00
        buf[19] = 0x00  # UintParam(3) = 65,536
        buf[20] = 0x01
        buf[21] = 0x00
        buf[22] = 0x00
        buf[23] = 0x00  # FloatParam = -10000.125
        buf[24] = 0x00
        buf[25] = 0x00
        buf[26] = 0x00
        buf[27] = 0x10
        buf[28] = 0x88
        buf[29] = 0xC3
        buf[30] = 0xC0
        buf[31] = 0x48  # StrParam = "Help!"
        buf[32] = 0x65
        buf[33] = 0x6C
        buf[34] = 0x70
        buf[35] = 0x21
        buf[36] = 0x00
        buf[37] = 0x20  # Checksum (decimal=1,534,784,980)
        buf[38] = 0x96
        buf[39] = 0x54
        buf[40] = 0x1C
        buf_size: int = 41
 
        _ = pkt.extract(buf, buf_size)  # returns last bit, unused.
 
        #  Get a list of the parameters in the packet sorted by their start
        #  location.  Get the values of all samples of each parameter as a string.
        all_params = pkt.get_sorted_parameter_list()
        for param_name in all_params:
            param = pkt.find_parameter(param_name)
 
            # See how many samples of parameter has and get each.
            for sample in range(1, param.get_number_of_samples() + 1):
                print(
                    f"{param_name} (sample {sample}): {param.get_value_as_string(sample)}"
                )
 
    except trek.TrekError as err:
        # Locate friendly message why it failed.
        print(err.find_error_code())
        print(err)
 
 
if __name__ == "__main__":
    main()