reactos/lib/string/strtol.c

   1 #include <string.h>
   2 #include <limits.h>
   3 #include <ctype.h>
   4
   5 /*
   6  * @implemented
   7  */
   8 long
   9 strtol(const char *nptr, char **endptr, int base)
  10 {
  11   const char *s = nptr;
  12   unsigned long acc;
  13   int c;
  14   unsigned long cutoff;
  15   int neg = 0, any, cutlim;
  16
  17   /*
  18    * Skip white space and pick up leading +/- sign if any.
  19    * If base is 0, allow 0x for hex and 0 for octal, else
  20    * assume decimal; if base is already 16, allow 0x.
  21    */
  22   do {
  23     c = *s++;
  24   } while (isspace(c));
  25   if (c == '-')
  26   {
  27     neg = 1;
  28     c = *s++;
  29   }
  30   else if (c == '+')
  31     c = *s++;
  32   if ((base == 0 || base == 16) &&
  33       c == '0' && (*s == 'x' || *s == 'X'))
  34   {
  35     c = s[1];
  36     s += 2;
  37     base = 16;
  38   }
  39   if (base == 0)
  40     base = c == '0' ? 8 : 10;
  41
  42   /*
  43    * Compute the cutoff value between legal numbers and illegal
  44    * numbers.  That is the largest legal value, divided by the
  45    * base.  An input number that is greater than this value, if
  46    * followed by a legal input character, is too big.  One that
  47    * is equal to this value may be valid or not; the limit
  48    * between valid and invalid numbers is then based on the last
  49    * digit.  For instance, if the range for longs is
  50    * [-2147483648..2147483647] and the input base is 10,
  51    * cutoff will be set to 214748364 and cutlim to either
  52    * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
  53    * a value > 214748364, or equal but the next digit is > 7 (or 8),
  54    * the number is too big, and we will return a range error.
  55    *
  56    * Set any if any `digits' consumed; make it negative to indicate
  57    * overflow.
  58    */
  59   cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
  60   cutlim = cutoff % (unsigned long)base;
  61   cutoff /= (unsigned long)base;
  62   for (acc = 0, any = 0;; c = *s++)
  63   {
  64     if (isdigit(c))
  65       c -= '0';
  66     else if (isalpha(c))
  67       c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  68     else
  69       break;
  70     if (c >= base)
  71       break;
  72     if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  73       any = -1;
  74     else
  75     {
  76       any = 1;
  77       acc *= base;
  78       acc += c;
  79     }
  80   }
  81   if (any < 0)
  82   {
  83     acc = neg ? LONG_MIN : LONG_MAX;
  84   }
  85   else if (neg)
  86     acc = -acc;
  87   if (endptr != 0)
  88     *endptr = any ? (char *)((size_t)(s - 1)) : (char *)((size_t)nptr);
  89   return acc;
  90 }