Universal escaping in KConfigINI: Summary and patch

[Andreas Hartmetz]

On Thursday 24 May 2007 20:14:47 Ingo Klöcker wrote:
> On Thursday 24 May 2007 19:05, Oswald Buddenhagen wrote:
> > On Thu, May 24, 2007 at 06:47:41PM +0200, Andreas Hartmetz wrote:
> > > The switch blocks are not inelegant, they are really ugly :)
> > > The use of switch statements was a conscious decision.
> > > These implementations have the advantage of obviously not having
> > > any index out of bounds errors, and I trust the compiler to make a
> > > table out of switch statements where possible. The simplistic
> > > switch statement should be easy to understand by the compiler so it
> > > can optimize well.
> > > If you are reasonably sure that one of the target compilers won't
> > > do this, I'll change it.
> >
> > no sane compiler will automatically generate an almost-256-entry
> > table for 16 values. ;) if you used the *low* nibble in toHex it
> > *might* optimize it, but given that the manual solution is much nicer
> > i would not take chances.
> > i see little chance for toChar being optimized, too, but you can look
> > at the -S output ... but even if, it would be still ugly for almost
> > no benefit (the bounds checking and indexing will outweight the few
> > comparisons and arithmetics easily).
>
> Shouldn't there be a single, fast implementation of those two
> conversions somewhere in kdelibs/kdecore? I bet those conversions have
> been re-implemented all over KDE.
>
> Please don't add another private version of those methods but instead
> add public versions for example to
> trunk/KDE/kdelibs/kdecore/text/kstringhandler.*
>
Ah, I thought the same, but then I thought that nobody will find these 
functions anyway. Doing the Right Thing would still make sense...
My current versions of these functions look like this now, for the record:

inline static char hexToChar(const char *str)
{
    char ret = 0;
    char c;
    for (int i = 0; i < 2; i++) {
        ret <<= 4;
        c = str[i];

        if (c >= '0' && c <= '9') {
            ret |= c - '0';
        } else if (c >= 'a' && c <= 'f') {
            ret |= c - 'a' + 0x0a;
        } else if (c >= 'A' && c <= 'F') {
            ret |= c - 'A' + 0x0a;
        } else {
             //TODO: warning
            return 'x';
        }
    }
    return ret;
}

inline static void charToHex(char c, char *str)
{
    static const char lookup[] = {
        '0', '1', '2', '3', '4', '5', '6', '7',
        '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
    };

    for (int i = 0; i < 2; i++) {
        str[i] = lookup[c >> 4];
        c <<= 4;
    }
}


> Regards,
> Ingo