[Http-crcsync] General comments on crcsync document

Alex Wulms alex.wulms at scarlet.be
Thu Jul 9 17:02:07 EDT 2009


Hi,

I'll specify it as following in the spec:

number-of-full-blocks = filesize/blocksize
trailing-block-size = filesize%blocksize
trailing-block only exists if trailing-block-size != 0

All operations in integer logic, using C conventions (e.g. / is integer 
division, % is modulo)

Cheers,
Alex


Op donderdag 9 juli 2009, schreef Patrick McManus:
> > Regarding trailing block and file-size header: we specify the file-size
> > and we (plan to) specify the number of blocks (though, it could indeed be
> > implicitly derived from the blocks-header-size like somebody mentioned).
>
> so number of blocks is the missing information, not block-size?
>
> Doesn't that still make the block size ambiguous?
>
> e.g. file-size = 45, number of blocks = 3 ..
> wouldn't (3x15 + a trailer of 0) and (2x20 + a trailer of 5) both be
> legitimate?
>
> maybe I'm just missing something, but the block size would seem to be
> something the server would need to compute hashes when looking for a
> matched block.
>
> I've also got this inkling that you ought to at least put some SHOULDs
> around various recommended block sizes.. In the cases where the server
> is not creating the resource completely on the fly this would allow it
> to cache some important meta information and save itself some runtime
> computations if it at least had a reasonable expectation about what
> block size the next request would use...




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