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Re: deltification semi-rewrite starting now

From: Branko Čibej <brane_at_xbc.nu>
Date: 2001-09-25 18:40:45 CEST

Branko �ibej wrote:

> kfogel@collab.net wrote:
>
>> But what is REP-OFFSET? We understand the REP-KEY that precedes it.
>> That's simply the representation against whose fulltext this delta
>> applies, right?
>>
> Let me think ... Yes.
>
>> But why would we want an offset into that rep? We
>> had thought the relevant offset(s) are part of the svndiff encoding.
>> Is it a way of magically jumping over a certain number of windows and
>> landing on the right one, in next-most-immediate source
>> representation, or is it something else?
>>
> Although the offset is implicit in the svndiff, in real life you want
> to find the source (fulltext) *before* decoding the window. Also, as I
> noted, you might want to just use a (self-referencing) vdelta compress
> instead of a diff, if the result of the compression is smaller than
> the diff.
>
> Hmm. It's been a long time since I wrote that, and as usual I left
> some of the reasoning out. I'll have to think about this again. I sort
> of remember it had to do with true random access to the text.

I remember, I remember!

The offsets embedded in the svndiff are stored in a string; these
offsets would be in the representation. The point is that you get all
the information you need to select the appropriate windows from the rep
skel -- without touching a single string. This means a bit more space
used in the repository, but lots less memory used on the server.

-- 
Brane �ibej   <brane_at_xbc.nu>            http://www.xbc.nu/brane/
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Received on Sat Oct 21 14:36:42 2006

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