[PATCH] add memrchr(3)

[Corinna Vinschen]

Hi Yaakov,

On May  9 14:02, Yaakov (Cygwin/X) wrote:
> On Wed, 2012-05-09 at 08:23 -0600, Eric Blake wrote: 
> > sizeof(unsigned char) is defined by C to be exactly 1; I always
> > question code that spells it out longhand instead of using 1.
> 
> But, but, magic numbers! :-) Not that I care either way here.
> 
> > >>       if (src > src_end) >> 	break;
> > 
> > Also, src will never be > src_end - memchr returns NULL rather than
> > reading beyond the bounds of length.
> 
> Actually, it *was* returning values beyond src_end and the effects
> weren't pretty, hence the check.
> 
> > Additionally, I think that searching forwards through the array via one
> > function call per occurrence of the byte in question is wasteful -
> > since we already know the array bounds, we might as well search in
> > reverse by doing a single C loop that iterates backwards over a word at
> > a time. strrchr must search forwards, because it is also searching for
> > the terminating NUL and doesn't know the length in advance, but memrchr
> > should be faster.
> 
> Fair enough, so code duplication it is then.  Revised source file
> attached.

Could you please provide a ChangeLog entry as well?


Thanks,
Corinna