dist/ntp/libntp/atouint.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * atouint - convert an ascii string to an unsigned 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 atouint(
  14         const char *str,
  15         u_long *uval
  16         )
  17 {
  18         register u_long u;
  19         register const char *cp;
  20
  21         cp = str;
  22         if (*cp == '\0')
  23             return 0;
  24
  25         u = 0;
  26         while (*cp != '\0') {
  27                 if (!isdigit((int)*cp))
  28                     return 0;
  29                 if (u > 429496729 || (u == 429496729 && *cp >= '6'))
  30                     return 0;   /* overflow */
  31                 u = (u << 3) + (u << 1);
  32                 u += *cp++ - '0';       /* ascii dependent */
  33         }
  34
  35         *uval = u;
  36         return 1;
  37 }