XS.xs 

static SV* _encoding_fix_latin_xs(SV* source) {
    SV* out = NULL;  // Defer initialisation
    U8 *ph, *pt;
    UV i, bytes;

    STRLEN l;
    ph = pt = SvPV(source, l);
    bytes = SvCUR(source);
    for(i = 0; i < bytes; i++, ph++) {
        if((*ph & 0x80) == 0)
            continue;
        // ...
    }

    if(out == NULL) return(source);