Hello, I am trying to implement a schema to describe a LINK-16 message embedded within a DIS Signal PDU as described by SISO-STD-002 [1], paragraph 5.2.2.9 and table 5.2.3; commonly referred to as SISO-J. The problem is that fields are packed into 32 bit words with big endian byte order, and little endian bitfield order. It is currently an error to specify a byteOrder of bigEndian with a bitOrder of leastSignificantBitFirst. Also, I have not found a way to set word size; it appears that word size is implicitly set to the size of each field.
Following is a simple example to demonstrate how fields need to be interpreted. It is just an example and does not represent any part of a SISO-J message. Data is comprised of 3 unsigned integer bitfields: slot1 is 12 bits slot2 is 32 bits slot3 is 20 bits Given an input with the following bytes in hex: 01 23 45 67 89 AB CD EF Parsed results need to be (in hex): slot1: 0567 slot2: DEF01234 slot3: 089ABC Explanation of results: Since the bitfields need to consume data in a leastSignificantBitFirst order, it is easier to represent the input in right-to-left order where bits are consumed starting at the right and moving toward the left. Since words are 4 bytes, and in big endian order, the lowest bit in the 4th byte is the first bit to be consumed. Reordering the input data and consuming data from right to left yields the correct field boundaries. 89 AB CD EF 01 23 45 67 parse fields right to left 05 06 07 08 01 02 03 04 input byte position slot1 consumes the right 3 nibbles, slot2 consumes the next 8 nibbles, and slot3 consumes the left 5 nibbles. Could you please let me know if there is a way to parse fields in this manner? Marshall Miller [1] https://www.sisostds.org/DesktopModules/Bring2mind/DMX/Download.aspx?Command=Core_Download&EntryId=43048&PortalId=0&TabId=105
