Date   : Mon, 13 Jun 2011 15:32:45 +0100
From   : jgh@... (J.G.Harston)
Subject: Calculating CRCs

Rick Murray wrote:
> Google -> "crc 32 source code".
> Take your pick. Fifth link down is:
>    http://www.netrino.com/Embedded-Systems/How-To/CRC-Calculation-C-Code

Argh!!! That's *exactly* the useless sort of stuff I kept finding.

> which explains by bit, by byte, and differences in various types of CRC.

Lots of detailed theoretical analysis of what CRCs are and the
mathematics of how they work, but no actual real cut'n'paste usable
code. It even starts by saying "Before writing even one line of code,
let's first examine the mechanics of modulo-2 binary division...."
No!!! I don't care about the theory!!! I just need the code!!!!

> Because you were not specific enough in your search.
>
>    "xmodem crc calculation code"

Ah, yes, *now*. Try 15 years ago.

>    http://www.techfest.com/hardware/modem/xymodem.htm
> page 26 gives C code for CRC-16.

Yes, that's the document I finally managed to track down:
http://mdfs.net/Docs/Comp/Comms/FTP/

> Took me four minutes to find CRC-16 code in 6502 and ARM:
>    http://regregex.bbcmicro.net/crc-catalogue.htm#appendix.b

Yes, that's the first place I went to looking for CRC-32 code.

-- 
J.G.Harston - jgh@...