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Date: Tue, 24 Nov 2015 17:36:58 +0100
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 <CAKQ1sVPD+sz3mYmSYEL=KTjELocT-_WHRmzbfeD61rNi9YxE2A@mail.gmail.com>
Subject: Re: svn commit: r1715938 -
 /httpd/httpd/trunk/modules/cache/cache_util.c
From: Yann Ylavic <ylavic.dev@gmail.com>
To: httpd-dev <dev@httpd.apache.org>
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On Tue, Nov 24, 2015 at 5:18 PM, Graham Leggett <minfrin@sharp.fm> wrote:
> On 24 Nov 2015, at 6:15 PM, Yann Ylavic <ylavic.dev@gmail.com> wrote:
>
>> Not sure:
>>    if (!strcmp(h, "max-age")
>>        || ap_cmpcasestr(h, "max-age"))
>> is likely to be a bit faster than a single ap_cmpcasestr() when it
>> matches, but much slower when it does not.
>
> Yep, that=E2=80=99s the point.
>
> The vast majority of comparisons are lowercase for tokens like this. Migh=
t as well test that fast path first before testing the worst case scenario.

Sure, but my point is that the worst case is likely depend on the
application, eg:

    case 'm':
    case 'M':
    if (!strncmp(token, "max-age", 7)
        || !ap_casecmpstrn(token, "max-age", 7)) {
        ...
    }
    else if (!strncmp(token, "max-stale", 9)
             || !ap_casecmpstrn(token, "max-stale", 9)) {
        ...
    }
    else if (!strncmp(token, "min-fresh", 9)
             || !ap_casecmpstrn(token, "min-fresh", 9)) {
        ...
    }
    else if (!strcmp(token, "max-revalidate")
             || !ap_casecmpstr(token, "must-revalidate")) {
        ...
    }
    else if ...

is going to be costly when matched against "must-revalidate", or worse
"my-token".

We could use all str[n]cmp() first, but still it's a lot of
comparisons, and now duplicated code too.

Regards,
Yann.