kernel/lib/stdlib/strtol.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2007  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   4  *  Copyright (C) 2008  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   5  *
   6  *  This program is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <ctype.h>
  21
  22 long strtol (const char *nptr, char **endptr, int base)
  23 {
  24         const char *s = nptr;
  25         unsigned long acc;
  26         unsigned char c;
  27         unsigned long cutoff;
  28         int neg = 0;
  29         int any;
  30         int cutlim;
  31
  32         do {
  33                 c = *s++;
  34         } while (isspace (c));
  35
  36         if (c == '-') {
  37                 neg = 1;
  38                 c = *s++;
  39         } else if (c == '+')
  40                 c = *s ++;
  41
  42         if ((base == 0 || base == 16) &&
  43             c == '0' && (*s == 'x' || *s == 'X')) {
  44                 c = s[1];
  45                 s += 2;
  46                 base = 16;
  47         }
  48
  49         if (base == 0)
  50                 base = c == '0' ? 8 : 10;
  51
  52         cutoff = 2147483647;
  53         cutlim = cutoff % (unsigned long) base;
  54         cutoff /= (unsigned long) base;
  55
  56         for (acc = 0, any = 0;; c = *s ++) {
  57                 if (!isascii (c))
  58                         break;
  59                 if (isdigit (c))
  60                         c -= '0';
  61                 else if (isalpha(c))
  62                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  63                 else
  64                         break;
  65
  66                 if (c >= base)
  67                         break;
  68                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  69                         any = -1;
  70                 else {
  71                         any = 1;
  72                         acc *= base;
  73                         acc += c;
  74                 }
  75         }
  76
  77         if (any < 0) {
  78                 acc = 2147483647;
  79
  80         } else if (neg)
  81                 acc = -acc;
  82
  83         if (endptr != 0)
  84                 *endptr = (char *) (any ? s - 1 : nptr);
  85
  86         return acc;
  87 }
  88