unsigned long long strtoull(const char *str, char **end, int base)
{
- long long ret = 0;
+ unsigned long long ret = 0;
if( !str || base < 0 || base > 36 || base == 1 ) {
if(end)
if( base == 0 )
base = 10;
+ // Value before getting within 1 digit of ULLONG_MAX
+ // - Used to avoid overflow in more accurate check
+ unsigned long long max_before_ullong_max = ULLONG_MAX / base;
+ unsigned int space_above = ULLONG_MAX - max_before_ullong_max * base;
while( *str )
{
int next = -1;
if( 'a' <= *str && *str <= 'a'+base-10-1 )
next = *str - 'a' + 10;
}
+ //_SysDebug("strtoull - ret=0x%llx,next=%i,str='%s'", ret, next, str);
if( next < 0 )
break;
+ // If we're already out of range, keep eating
if( ret == ULLONG_MAX ) {
errno = ERANGE;
str ++;
// Keep eating until first unrecognised character
continue;
}
- if( ret > (ULLONG_MAX-next)/base ) {
- //_SysDebug("strtoull - Out of range (0x%llx > 0x%llx)", ret, (ULLONG_MAX-next)/base);
- //_SysDebug("strtoull - (%llu > %llu)", ret, (ULLONG_MAX-next)/base);
- ret = ULLONG_MAX;
- errno = ERANGE;
- str ++;
- continue;
+
+ // Rough then accurate check against max value
+ if( ret >= max_before_ullong_max )
+ {
+ //_SysDebug("strtoull - 0x%llx>0x%llx", ret, max_before_ullong_max);
+ if( (ret - max_before_ullong_max) * base + next > space_above ) {
+ //_SysDebug("strtoull - %u*%u+%u (%u) > %u",
+ // (unsigned int)(ret - max_before_ullong_max), base, next, space_above);
+ ret = ULLONG_MAX;
+ errno = ERANGE;
+ str ++;
+ continue;
+ }
}
ret *= base;
ret += next;
//_SysDebug("strtoll - neg=%i,ret=%llu", neg, ret);
if( neg ) {
- if( -ret < LLONG_MIN ) {
+ // Abuses unsigned integer overflow
+ if( ret + LLONG_MIN < ret ) {
errno = ERANGE;
return LLONG_MIN;
}