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From Jim Jagielski <...@jaguNET.com>
Subject Re: apr_token_* conclusions (was: Better casecmpstr[n]?)
Date Wed, 25 Nov 2015 21:02:16 GMT
In general, strcmp() is not implemented via strcmp.c
(although if you do a source code search for strcmp, that's
what you'll get). Most of the time it's implemented in
assembly (strcmp.s) or simply leverages memcmp() where
you aren't doing a byte by byte comparison but are doing
a native memory word (32 or 64bit) comparison. This
makes them super fast.

Once we need to worry about case insensitivity, then
we see a whole gamut of implementations; some use
a mapped array as I did; some go char by char and call
tolower() on each one; some do other things such as
testing if isupper() before calling tolower() if needed.
The word-based optimizations seem less viable, as seen
in test results that I ran and Yann also verified (afaict)

In my tests, my impl was faster on OSX and CentOS5 and 6.
It's a very common function we use and with my test results
it seemed to make sense to provide our own impl, esp if
we decided that what we were really concerned about was
comparing for equality, and so would be able to avoid
the !strcasecmp logic leaping.

If we decide that all this was for moot, that's fine.
That's what these types of investigations and discussions
are for.

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