ntdll: rtlstr.c: Implement checking for control characters inRtlIsTextUnicode [try 2]

[Rolf Kalbermatter]

Zac Brown [mailto:zac at zacbrown.org] 
> Rolf Kalbermatter wrote:
> > Dan Kegel [mailto:dank at kegel.com]
> >  
> >> e.g.
> >>
> >>  if (flags & IS_TEXT_UNICODE_CONTROLS)
> >> 	    for (i = 0; i < len; i++)
> >>          switch (s[i]) {
> >>            case '\t':
> >>            case '\n':
> >>            case 'r':
> >>            case 0x20:
> >>                 out_flags |= IS_TEXT_UNICODE_CONTROLS;
> >>                 goto done;
> >>            default:
> >>          }
> >>     }
> >>     done:
> > 
> > Shouldn't a break instead of the goto work too?
> 
> A break will only exit the switch statement which is 
> pointless since we don't care about the rest of the string if 
> we find a control character.

Ah well, you are right of course! But personally I feel about the use
of a switch statement in such a case a bit "overdone". It's not so much
a selection of operations based on a variable as much more a clear
conditional expression such as

    if (expression1 OR
        expresssion2 OR
        ...)
    {
       out_flags |= IS_TEXT_UNICODE_CONTROLS;
       break;
    }

which I think Dan was trying to avoid since he might not like "complex"
conditional expressions. But then I would normally go myself to great
lengths to avoid a goto as I feel bad about the use of them :-)

The fact that s[i] would seem to be evaluated 4 times might look bad
but should be no problem for nowadays optimizing compilers to create
similar code as what a switch statement would produce and could be
also avoided by an incremented character pointer instead of the loop
counter i, which might be even more optimal.

Rolf Kalbermatter