dist/ntp/libntp/atoint.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * atoint - convert an ascii string to a signed long, with error checking
   5  */
   6 #include <sys/types.h>
   7 #include <ctype.h>
   8
   9 #include "ntp_types.h"
  10 #include "ntp_stdlib.h"
  11
  12 int
  13 atoint(
  14         const char *str,
  15         long *ival
  16         )
  17 {
  18         register long u;
  19         register const char *cp;
  20         register int isneg;
  21         register int oflow_digit;
  22
  23         cp = str;
  24
  25         if (*cp == '-') {
  26                 cp++;
  27                 isneg = 1;
  28                 oflow_digit = '8';
  29         } else {
  30                 isneg = 0;
  31                 oflow_digit = '7';
  32         }
  33
  34         if (*cp == '\0')
  35             return 0;
  36
  37         u = 0;
  38         while (*cp != '\0') {
  39                 if (!isdigit((int)*cp))
  40                     return 0;
  41                 if (u > 214748364 || (u == 214748364 && *cp > oflow_digit))
  42                     return 0;   /* overflow */
  43                 u = (u << 3) + (u << 1);
  44                 u += *cp++ - '0';       /* ascii dependent */
  45         }
  46
  47         if (isneg)
  48             *ival = -u;
  49         else
  50             *ival = u;
  51         return 1;
  52 }