Re: [PATCH] util/cutils: Expand do_strtosz parsing precision to 64 bits

[Tao Xu]

On 12/19/2019 2:26 AM, Markus Armbruster wrote:
> Tao Xu <address@hidden> writes:
>
> > On 12/18/2019 9:33 AM, Tao Xu wrote:
> > > On 12/17/2019 6:25 PM, Markus Armbruster wrote:
> [...]
> > > > Also fun: for "0123", we use uint64_t 83, not double 123.0.  But for
> > > > "0123.", we use 123.0, not 83.
> > > >
> > > > Do we really want to accept octal and hexadecimal integers?
> > >
> > > Thank you for reminding me. Octal and hexadecimal may bring more
> > > confusion. I will use qemu_strtou64(nptr, &suffixu, 10, &valu) and
> > > add test for input like "0123".
> >
> > Hi Markus,
> >
> > After I use qemu_strtou64(nptr, &suffixu, 10, &valu), it cause another
> > question. Because qemu_strtod_finite support hexadecimal input, so in
> > this situation, it will parsed as double. It will also let large
> > hexadecimal integers be rounded. So there may be two solution:
> >
> > 1: use qemu_strtou64(nptr, &suffixu, 0, &valu) and parse octal as
> > decimal. This will keep hexadecimal valid as now.
> >
> > "0123" --> 123; "0x123" --> 291
>
> How would you make qemu_strtou64() parse octal as decimal?

How about this solution, set @base as variable, if we detect 
hexadecimal, we use 0, then can prase decimal as u64, else we use 10, 
then can prase octal as decimal, because 0 prefix will be ignored in 
qemu_strtou64(nptr, &suffixu, 10, &valu);

    const char *p = nptr;
    while (qemu_isspace(*p)) {
       p++;
    }
    if (*p == '0' && (qemu_toupper(*(p+1)) == 'X' ||) {
        base = 0;
    } else {
        base = 10;
    }

    retd = qemu_strtod_finite(nptr, &suffixd, &vald);
    retu = qemu_strtou64(nptr, &suffixu, base, &valu);
    use_strtod = strlen(suffixd) < strlen(suffixu);

    if (use_strtod) {
        endptr = suffixd;
        retval = retd;
    } else {
        endptr = suffixu;
        retval = retu;
    }
> > 2: use qemu_strtou64(nptr, &suffixu, 10, &valu) and reject octal and
> > decimal.
> >
> > "0123" --> Error; "0x123" --> Error
>
> How would you reject the 0x prefix?
How about check the first&second character is '0' and 'x' and then 
return -EINVAL.