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NNTP-Posting-Date: Tue, 10 May 2011 03:27:37 -0500
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Date: Tue, 10 May 2011 04:27:37 -0400
From: pete <pfiland@mindspring.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c:3672

Dr Nick wrote:
 
> I've got "caseless_strcmp" in my code, built on strcasecmp (and, on
> porting to Windows, stricmp)
> 
> Thusly:
> 
> #ifdef HAVE_STRCASECMP
>   #define caseless_strcmp(x,y) strcasecmp(x,y)
> #else
>   #ifdef HAVE_STRICMP
>     #define caseless_strcmp(x,y) stricmp(x,y)
>   #else
>     #error Need to implement caseless string comparison here
>   #endif
> #endif
> 
> So I push the problem off for the time being,
> avoid writing code I don't
> need to, but don't leave anyone porting it in the future to a non GNU
> system foundering with no idea of what has gone wrong.


This is what I have so far:

#include <ctype.h>

int str_ccmp(const char *s1, const char *s2)
{
    for (;;) {
        if (*s1 != *s2) {
            const int c1 = tolower(*(const unsigned char *)s1);
            const int c2 = tolower(*(const unsigned char *)s2);

            if (c2 != c1) {
                return c2 > c1 ? -1 : 1;
            }
        } else {
            if (*s1 == '\0') {
                return 0;
            }
        }
        ++s1;
        ++s2;
    }
}

I'm still not sure whether it's better to use
    tolower(*(const unsigned char *)s1)
or
    tolower((unsigned char)*s1)

-- 
pete