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

   1 #include <precomp.h>
   2
   3 /*
   4  * @implemented
   5  */
   6 long
   7 strtol(const char *nptr, char **endptr, int base)
   8 {
   9   const char *s = nptr;
  10   unsigned long acc;
  11   int c;
  12   unsigned long cutoff;
  13   int neg = 0, any, cutlim;
  14
  15   /*
  16    * Skip white space and pick up leading +/- sign if any.
  17    * If base is 0, allow 0x for hex and 0 for octal, else
  18    * assume decimal; if base is already 16, allow 0x.
  19    */
  20   do {
  21     c = *s++;
  22   } while (isspace(c));
  23   if (c == '-')
  24   {
  25     neg = 1;
  26     c = *s++;
  27   }
  28   else if (c == '+')
  29     c = *s++;
  30   if ((base == 0 || base == 16) &&
  31       c == '0' && (*s == 'x' || *s == 'X'))
  32   {
  33     c = s[1];
  34     s += 2;
  35     base = 16;
  36   }
  37   if (base == 0)
  38     base = c == '0' ? 8 : 10;
  39
  40   /*
  41    * Compute the cutoff value between legal numbers and illegal
  42    * numbers.  That is the largest legal value, divided by the
  43    * base.  An input number that is greater than this value, if
  44    * followed by a legal input character, is too big.  One that
  45    * is equal to this value may be valid or not; the limit
  46    * between valid and invalid numbers is then based on the last
  47    * digit.  For instance, if the range for longs is
  48    * [-2147483648..2147483647] and the input base is 10,
  49    * cutoff will be set to 214748364 and cutlim to either
  50    * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
  51    * a value > 214748364, or equal but the next digit is > 7 (or 8),
  52    * the number is too big, and we will return a range error.
  53    *
  54    * Set any if any `digits' consumed; make it negative to indicate
  55    * overflow.
  56    */
  57   cutoff = neg ? ((unsigned long)LONG_MAX+1) : LONG_MAX;
  58   cutlim = cutoff % (unsigned long)base;
  59   cutoff /= (unsigned long)base;
  60   for (acc = 0, any = 0;; c = *s++)
  61   {
  62     if (isdigit(c))
  63       c -= '0';
  64     else if (isalpha(c))
  65       c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  66     else
  67       break;
  68     if (c >= base)
  69       break;
  70     if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  71       any = -1;
  72     else
  73     {
  74       any = 1;
  75       acc *= base;
  76       acc += c;
  77     }
  78   }
  79   if (any < 0)
  80   {
  81     acc = neg ? LONG_MIN : LONG_MAX;
  82 #ifndef _LIBCNT_
  83     _set_errno(ERANGE);
  84 #endif
  85   }
  86   else if (neg)
  87     acc = 0-acc;
  88   if (endptr != 0)
  89     *endptr = any ? (char *)((size_t)(s - 1)) : (char *)((size_t)nptr);
  90   return acc;
  91 }