reactos/lib/sdk/crt/string/strtoul.c

   1 #include <precomp.h>
   2 #include <ctype.h>
   3
   4 /*
   5  * Convert a string to an unsigned long integer.
   6  *
   7  * Ignores `locale' stuff.  Assumes that the upper and lower case
   8  * alphabets and digits are each contiguous.
   9  *
  10  * @implemented
  11  */
  12 unsigned long
  13 strtoul(const char *nptr, char **endptr, int base)
  14 {
  15   const char *s = nptr;
  16   unsigned long acc;
  17   int c;
  18   unsigned long cutoff;
  19   int neg = 0, any, cutlim;
  20
  21   /*
  22    * See strtol for comments as to the logic used.
  23    */
  24   do {
  25     c = *s++;
  26   } while (isspace(c));
  27   if (c == '-')
  28   {
  29     neg = 1;
  30     c = *s++;
  31   }
  32   else if (c == '+')
  33     c = *s++;
  34   if ((base == 0 || base == 16) &&
  35       c == '0' && (*s == 'x' || *s == 'X'))
  36   {
  37     c = s[1];
  38     s += 2;
  39     base = 16;
  40   }
  41   if (base == 0)
  42     base = c == '0' ? 8 : 10;
  43   cutoff = (unsigned long)ULONG_MAX / (unsigned long)base;
  44   cutlim = (unsigned long)ULONG_MAX % (unsigned long)base;
  45   for (acc = 0, any = 0;; c = *s++)
  46   {
  47     if (isdigit(c))
  48       c -= '0';
  49     else if (isalpha(c))
  50       c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  51     else
  52       break;
  53     if (c >= base)
  54       break;
  55     if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  56       any = -1;
  57     else {
  58       any = 1;
  59       acc *= base;
  60       acc += c;
  61     }
  62   }
  63   if (any < 0)
  64   {
  65     acc = ULONG_MAX;
  66 #ifndef _LIBCNT_
  67     _set_errno(ERANGE);
  68 #endif
  69   }
  70   else if (neg)
  71     acc = 0-acc;
  72   if (endptr != 0)
  73     *endptr = any ? (char *)((size_t)(s - 1)) : (char *)((size_t)nptr);
  74   return acc;
  75 }