reactos/lib/string/strtoul.c

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