Mirror of :pserver:cvs@cvs.fefe.de:/cvs libowfat https://www.fefe.de/libowfat/
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.

#### 39 lines 1.0 KiB Raw Blame History

 ``````#include "scan.h" static const unsigned int maxint = ((unsigned int)-1)>>1; size_t scan_int(const char* src,int* dest) { register const char *tmp; register int l; register unsigned char c; unsigned int neg; int ok; tmp=src; l=0; ok=0; neg=0; switch (*tmp) { case '-': neg=1; /* fall through */ case '+': ++tmp; } while ((c=(unsigned char)(*tmp-'0'))<10) { unsigned int n; /* we want to do: l=l*10+c * but we need to check for integer overflow. * to check whether l*10 overflows, we could do * if ((l*10)/10 != l) * however, multiplication and division are expensive. * so instead of *10 we do (l<<3) (i.e. *8) + (l<<1) (i.e. *2) * and check for overflow on all the intermediate steps */ n=(unsigned int)l<<3; if ((n>>3)!=(unsigned int)l) break; if (n+((unsigned int)l<<1) < n) break; n+=(unsigned int)l<<1; if (n+c < n) break; n+=c; if (n > maxint+neg) break; l=(int)n; ++tmp; ok=1; } if (!ok) return 0; *dest=(neg?-l:l); return (size_t)(tmp-src); }``````