-=> mark lewis wrote to Tony Langdon <=-
ml> there shouldn't really be any TIC software that /requires/ the CRC...
ml> it's only
ml> real use is to ensure that the file is not changed in transit...
Actually, it is a required field in the TIC specification, and the way one
hatched files in Mystic, it is effectively "in transit" from a dummy node.
ml> depending on your OS, you may have the necessary tools already at
ml> hand...
ml> cksum
That one didn't work for me.
ml> crc32
Don't have that one and can't find it for Raspian (though other distros seem to
have it available).
ml> cksum or crc32 is the one you want but you should check with a known
ml> file that has a known CRC value and see which program outputs the same
ml> match... i say this because at least crc32 hashes can have pre- and
ml> post- conditioning applied
ml> to them...
ml> i had to initialize the crc variable to $ffffffff (as a signed
ml> longint) and then feed each character individually to the crc
That sounds similar to the TIC specs.
ml> routine... i could have fed the entire blob of data and let the routine
ml> walk through it but that gave a different and wrong result... at the
ml> end, we did not XOR with $ffffffff but we do have to invert the result
ml> so the bytes are reversed since to match what's in
ml> the JAM data files... this byte reversal is because the legacy method used
ml> is for traditional analogue modems and the UART wants everything reversed
ml> for transmission... granted a UART is not used in this case
ml> but it is the way the sofware is written and there's a lot of software that
ml> uses this same formulation method...
Yes, again that rings a bell with the specs, which I did look up. There is some
code there showing how the CRC32 is generated, just prefer not to have to
re-learn file handling in Pascal just yet. :)
ml> [time passes]
ml> i just checked what i was checking for JAM with the cksum and crc32
ml> tools but neither returned the desired results... i'll have to go play,
ml> now, with checking a file and its TIC to see if i can determine which
ml> is correct if either one is... pre- and post- conditioning and whether
ml> to flip the bytes or not make a huge difference in the results...
I had no joy with cksum, and I don't have crc32 on my system.
... I hit the CTRL key but I'm still not in control!
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