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Re: very long string support

From: Ben Pfaff
Subject: Re: very long string support
Date: Wed, 03 May 2006 08:04:07 -0700
User-agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux)

John Darrington <address@hidden> writes:

> It seems that spss formats a 2551 byte string as 10 consecutive
> 255-byte strings followed by a 103 byte string with the last 102 bytes
> empty.  
> Or in general a N byte string (where N > 255) is formated as 
> (N div 252) consecutive 255 byte strings followed by a  8xsup(N - (N div
> 252)x255/8) byte string (God knows why!).
> When reading we just have to assume that there'll be "a number" of 255
> byte strings, followed by a string <= 255 bytes in length.

That is truly bizarre.  I will have to do some thinking about why
it would do anything so zany.

What do you mean by "xsup"?

>      In both cases we'd also need to add something like
>      "w->has_very_long_strings" to the conditions to take the slow
>      path.
> OK.  I think that's where I came into problems.  I was trying to
> ensure that the fast path would always be taken. Maybe that was a
> misguided goal.

I don't think it's a worthwhile thing to try to optimize that
little bit of code, especially if it inconveniences other code.

> I'm not sure about the comments you made about AGGREGATE.  Can you
> provide a test case which fails.  Then I can check it in as a
> regression test.

On second thought I'm not sure whether AGGREGATE is affected.  It
does support long strings, though.  I'll see.
Ben Pfaff 
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