RE: Early-posting a new idea for the summary format

[Philip Van Hoof <spam pvanhoof be>]

On Fri, 2007-02-02 at 09:18 +0200, Dirk-Jan Binnema nokia com wrote:

> >
> >Basic question and reason for posting this: what do you guys 
> >think of it?
> 
> Uhm, basic question - what is the problem you are trying to solve?

I want to make adding new summary information less intrusive. At this
moment adding new summary information means that the entire summary file
will eventually have to be rewritten.

I would rather want it to only write the new information to a file, and
mmap that one once it reached a certain amount. But if I would do that,
the changes would be large enough to also change the format.

The format I would change for the simple fact that string duplicates are
common in it. They can be avoided easily and avoiding it would
drastically reduce the amount what must be mmap()ed. Hence the ALIAS
stuff.

I would also take out the flags and put those in a different file, as a
read-write mmap. Same reason: level wearing of flash devices, avoiding
total rewrites, etc etc. 

> >"W" means "word length". On a 32 bit computer this is 4 bytes, 
> >on a 64 bit computer this is 8 bytes.
> [...]
> 
> Would that mean that 32-bit roadmaps are not readable by a 64-bit
> program? It's not uncommon to switch between 32 and 64 bit mode
> on, say, an AMD64 - it would suck if the summaries would be unreadable.

That is what it means, yes. Though the summary mmaps could be converted
between different architectures, but not without a tool.


-- 
Philip Van Hoof, software developer
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gnome: pvanhoof at gnome dot org 
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