Nevermind - someone figured it out: https://blog.cugu.eu/post/apfs/#checksum
My code was missing the extra (optional) "check bytes" after the sums calculation. I've updated my code accordingly: http://files.tempel.org/tmp/apfs-fletcher-test.zip It now also contains versions for fletcher-16 and -32, as well as an optimized form that avoids the use of the modulo operator (though, with modern desktop CPUs, I wonder if that even still makes a difference or if the MOD instruction is just as fast as an AND and a SHIFT instruction together). (As Quinn says) Enjoy, Thomas On Sun, Apr 30, 2017 at 1:47 AM, Toby Thain <t...@telegraphics.com.au> wrote: > On 2017-04-29 7:42 PM, Thomas Tempelmann wrote: > >> On Sun, Apr 30, 2017 at 1:37 AM, Toby Thain <t...@telegraphics.com.au >> <mailto:t...@telegraphics.com.au>> wrote: >> >> Seems you have % instead of & ? And watch out for sign extension on >> those literal 0xFFFFFFFF's. You probably want an unsigned and long >> long suffix on them. >> >> >> Nope, both are correct, at least for standard fletcher algorithm. It's >> always modulo (%) MAXINT-1. >> > > Ah, OK. Thanks for clarifying! > > > > And 0xFFFFFFFF's gets properly expanded to > >> unsigned 64 bit, as it should. I double checked using uint64_t variable >> all the way, and it didn't change the outcome. >> >> -- >> Thomas Tempelmann, http://www.tempel.org/ >> Follow me on Twitter: https://twitter.com/tempelorg >> Read my programming blog: http://blog.tempel.org/ >> > > -- Thomas Tempelmann, http://www.tempel.org/ Follow me on Twitter: https://twitter.com/tempelorg Read my programming blog: http://blog.tempel.org/
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