[PATCH libxkbcommon v2 1/2] makekeys: use GNU gperf to generate perfect hashtables

David Herrmann dh.herrmann at googlemail.com
Thu Oct 4 09:51:48 PDT 2012

Hi Bill

On Thu, Oct 4, 2012 at 6:46 PM, Bill Spitzak <spitzak at gmail.com> wrote:
> David Herrmann wrote:
>> Hi Bill
>> On Thu, Oct 4, 2012 at 6:40 PM, Bill Spitzak <spitzak at gmail.com> wrote:
>>> David Herrmann wrote:
>>>>> So since makekeys is ugly and gperf is a bit excessive, maybe we should
>>>>> just keep it simple, what do you think?
>>>> Works all very nice here! Thanks, I am all in favor of this approach.
>>>> Reviewed-by: David Herrmann <dh.herrmann at googlemail.com>
>>>> No need to resend for the small fixes I suggested, though.
>>>> I am working on a case-insensitive search based on this patch. I will
>>>> send it when done. The approach I am using is:
>>>> Use bsearch with strcasecmp() to find _one_ of the possible solutions
>>>> (not necessarily the first). Then I check the entries _before_ and
>>>> _after_ the one I found whether they are equal and then I use some
>>>> heuristic to return the lower-case keysym (that is, KEY_a, not KEY_A).
>>> Actually binary search can always find the first match (or the last one
>>> depending on exactly how it is written:
>> I don't need the first one. I need the one that is the lower-case keysym.
> What I meant is that you only have to look forward from the found item, not
> in both directions.

Depends how bsearch() is implemented. If it directly returns on
equality, then I cannot be sure. Please see man bsearch(3). It
explicitly mentions that the item returned is unspecified on

I we would use the algorithm you mentioned, then you're right. But the
bsearch() implementation might add additional conditions in the loop
which we cannot rely on to be not there.


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