Re: [coreboot] r3236 - in trunk/payloads/libpayload: include libc

[a a]

Ulf Jordan wrote:
> On Fri, 11 Apr 2008, [e-mail] wrote:
> > +int isxdigit(int c)
> > +{
> > return isdigit(c) || (tolower(c)>= 'a' && tolower(c) <= 'z');
> >
> > +}
>
> Shouldn't this be
>
> return isdigit(c) || (tolower(c)>= 'a' && tolower(c) <= 'f');

jep it should..
but why not :
  return isdigit(c) || c>= 'a' && c <= 'f' || c>= 'A' && c <= 'F' );
it might be even faster if you do
return isdigit(c) || (c & ~0x20)>= 'A' && (c & ~0x20) <= 'F' );
> /ulf

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r3236 - in trunk/payloads/libpayload: include libc

[Segher Boessenkool]

> > > +int isxdigit(int c)
> > > +{
> > > return isdigit(c) || (tolower(c)>= 'a' && tolower(c) <= 'z');
> > >
> > > +}
> >
> > Shouldn't this be
> >
> > return isdigit(c) || (tolower(c)>= 'a' && tolower(c) <= 'f');
>
> jep it should..
> but why not :
>  return isdigit(c) || c>= 'a' && c <= 'f' || c>= 'A' && c <= 'F' );

For one thing, because it doesn't compile.  Also, the compiler
will generate equivalent code (also wrt size and speed).
> it might be even faster if you do
> return isdigit(c) || (c & ~0x20)>= 'A' && (c & ~0x20) <= 'F' );

Or we could write it as

return ((c >= '0') + (c > '9') + (c >= 'a') + (c > 'f') + (c >= 'A') + 
(c > 'F')) & 1;

which might be even faster!

You cannot tell without measuring, and it doesn't matter anyway:
the most important things to optimise for are readability and
maintainability (and those two are very much related).

Segher