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

[Tao Xu <tao3.xu@intel.com>]

On 12/19/2019 2:26 AM, Markus Armbruster wrote:
> Tao Xu <tao3.xu@intel.com> 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.