contrib/cvs/lib/strtoul.c

   1 /*
   2  * strtol : convert a string to long.
   3  *
   4  * Andy Wilson, 2-Oct-89.
   5  */
   6
   7 #include <errno.h>
   8 #include <ctype.h>
   9 #include <stdio.h>
  10
  11 #ifdef HAVE_CONFIG_H
  12 #include "config.h"
  13 #endif
  14
  15 #ifndef ULONG_MAX
  16 #define ULONG_MAX       ((unsigned long)(~0L))          /* 0xFFFFFFFF */
  17 #endif
  18
  19 extern int errno;
  20
  21 unsigned long
  22 strtoul(s, ptr, base)
  23      const char *s; char **ptr; int base;
  24 {
  25   unsigned long total = 0;
  26   unsigned digit;
  27   const char *start=s;
  28   int did_conversion=0;
  29   int overflow = 0;
  30   int negate = 0;
  31   unsigned long maxdiv, maxrem;
  32
  33   if (s==NULL)
  34     {
  35       errno = ERANGE;
  36       if (!ptr)
  37         *ptr = (char *)start;
  38       return 0L;
  39     }
  40
  41   while (isspace(*s))
  42     s++;
  43   if (*s == '+')
  44     s++;
  45   else if (*s == '-')
  46     s++, negate = 1;
  47   if (base==0 || base==16) /*  the 'base==16' is for handling 0x */
  48     {
  49       int tmp;
  50
  51       /*
  52        * try to infer base from the string
  53        */
  54       if (*s != '0')
  55         tmp = 10;       /* doesn't start with 0 - assume decimal */
  56       else if (s[1] == 'X' || s[1] == 'x')
  57         tmp = 16, s += 2; /* starts with 0x or 0X - hence hex */
  58       else
  59         tmp = 8;        /* starts with 0 - hence octal */
  60       if (base==0)
  61         base = (int)tmp;
  62     }
  63
  64   maxdiv = ULONG_MAX / base;
  65   maxrem = ULONG_MAX % base;
  66
  67   while ((digit = *s) != '\0')
  68     {
  69       if (digit >= '0' && digit < ('0'+base))
  70         digit -= '0';
  71       else
  72         if (base > 10)
  73           {
  74             if (digit >= 'a' && digit < ('a'+(base-10)))
  75               digit = digit - 'a' + 10;
  76             else if (digit >= 'A' && digit < ('A'+(base-10)))
  77               digit = digit - 'A' + 10;
  78             else
  79               break;
  80           }
  81         else
  82           break;
  83       did_conversion = 1;
  84       if (total > maxdiv
  85           || (total == maxdiv && digit > maxrem))
  86         overflow = 1;
  87       total = (total * base) + digit;
  88       s++;
  89     }
  90   if (overflow)
  91     {
  92       errno = ERANGE;
  93       if (ptr != NULL)
  94         *ptr = (char *)s;
  95       return (ULONG_MAX);
  96     }
  97   if (ptr != NULL)
  98     *ptr = (char *) ((did_conversion) ? (char *)s : (char *)start);
  99   return negate ? -total : total;
 100 }