Mirror of :pserver:cvs@cvs.fefe.de:/cvs libowfat https://www.fefe.de/libowfat/
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#include "scan.h"
size_t scan_ulonglong(const char *src,unsigned long long *dest) {
register const char *tmp=src;
register unsigned long long l=0;
register unsigned char c;
while ((c=(unsigned char)(*tmp-'0'))<10) {
unsigned long long n;
#if defined(__GNUC__) && (__GNUC__ >= 5)
if (__builtin_mul_overflow(l,10,&n) || __builtin_add_overflow(n,c,&n))
break;
l=n;
#else
/* division is very slow on most architectures */
n=l<<3; if ((n>>3)!=l) break;
if (n+(l<<1) < n) break;
n+=l<<1;
if (n+c < n) break;
l=n+c;
#endif
++tmp;
}
if (tmp-src) *dest=l;
return (size_t)(tmp-src);
}
#ifdef UNITTEST
#include <assert.h>
int main() {
unsigned long long l;
assert(scan_ulonglong("0",&l)==1 && l==0);
assert(scan_ulonglong("1",&l)==1 && l==1);
assert(scan_ulonglong("4294967295",&l) == 10 && l==4294967295ull);
assert(scan_ulonglong("18446744073709551615",&l) == 20 && l==18446744073709551615ull);
assert(scan_ulonglong("18446744073709551616",&l) == 19 && l==1844674407370955161ull);
return 0;
}
#endif