wmemchar for unix

[monarch_dodra]

On Tuesday, 27 August 2013 at 14:43:10 UTC, H. S. Teoh wrote:
> On Tue, Aug 27, 2013 at 07:37:02AM -0700, Sean Kelly wrote:
>> On Aug 26, 2013, at 11:57 PM, monarch_dodra 
>> <monarchdodra at gmail.com> wrote:
>> 
>> > For performance reasons, I need a "w" version of memchr.
>> > 
>> > C defines wmemchr as:
>> > wchar_t * wmemchr ( const wchar_t *, wchar_t, size_t );
>> > 
>> > Unfortunatly, on unix, "wchar_t" is defined a *4* bytes long,
>> > making wmemchr, effectivelly, "dmemchr".
>> > 
>> > Are there any "2 byte" alternatives for wmemchr on unix?
>> 
>> Why not cast the array to ushort[] and do a find()?  Or is 
>> that too
>> slow as well?
>
> Optimized searches of this kind ideally translate to the 
> various rep*
> instructions on x86. I'm not sure if dmd does that 
> optimization. If you
> really feel inclined, you could do static if (X86) and throw in 
> an asm
> block (but that would break purity, @safety, etc., so probably 
> not a
> good idea).
>
> You *might* be able to coax GDC (or LDC) to do loop unrolling 
> and/or
> substitution with rep* instructions with just plain D code, 
> though.
> Can't really say without trying it out.
>
>
> T

Hum... I think that is too complicated for what I'm trying to do. 
I don't know assembly enough. Ideally, I was hoping for a 
pre-existing C function to do the work for me :)

For now, I can settle for a simple:
version (windows)
     //use fast wmemchr
else
     //use standard code

But It feels weird, in the sense that there is no reason for 
"2byte" search to be more specific to windows than for unix...