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Re: English terminology / explanation needed

From: Branko ─îibej <brane_at_xbc.nu>
Date: 2004-05-26 12:51:58 CEST

Ben Collins-Sussman wrote:

>>include/svn_error_codes.h:683
>>"Svndiff data contains backward-sliding source view"
>>What the Dickens is a "backward-sliding source view" ?
>>
>>
>
>There's no way to explain svndiff encoding here. :-)
>In a nutshell, svndiff is our way of encoding binary diffs. It operates
>on "windows" that "slide" across the data as the diff is performed. The
>binary diff algorithm refers to the original data by discussing offsets
>into the current window. I think this error is complaining that an
>svndiff operation is attempting to talk about data that the window has
>already moved past.
>
>
Almost but not quite...

We don't use sliding windows, we use sequential adjacent windows. This
error is probably historical: Once upon a time, we used sequential
_overlapping_ windows instead, as that tended to reduce the size of the
delta (often by some 10 percent). But overlapping windows would have
complicated the delta combiner enormously, so we moved to adjacent ones
and put in a check to make sure that they really are. Well. A window
"slides back" if it starts before the end of the previous window; at
least, that's what this message is trying to say.

I'm almost of the opinion that we can ditch this error message
completely, because it signals a bug in the code rather than an error
condition. We should be aborting or assering instead.

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Received on Wed May 26 12:54:02 2004

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