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Re: svn commit: rev 2112 - trunk/subversion/libsvn_repos

From: Greg Stein <gstein_at_lyra.org>
Date: 2002-06-07 22:59:44 CEST

On Fri, Jun 07, 2002 at 03:04:34PM -0500, Karl Fogel wrote:
> Ben Collins-Sussman <sussman@collab.net> writes:
> > Just a sanity check here, correct me if I'm wrong. The rule we're
> > following is, "if you know the length, use it. otherwise, use
> > APR_HASH_KEY_STRING."

Yes, that is the rule.

Note that it is possible to use binary values for hash keys, but we don't do
that. Of course, in that case, you will always be supplying a length.

> > Is that right? I mean, the constant is just
> > running strlen, right?
>
> Not quite. The reason to prefer the constant is that it tells the
> hash function "This is a null-terminated string, so compute the key
> length *while* you compute its hash value." So it only runs over the
> bytes once, instead of twice.

Exactly.

You can see the code in: apr/tables/apr_hash.c::find_entry(). (line 263)

Cheers,
-g

-- 
Greg Stein, http://www.lyra.org/
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Received on Fri Jun 7 22:58:47 2002

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