kernel/lib/stdlib/atoi.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 int atoi (const char *s)
  21 {
  22     char ** endptr = (char **) &s;
  23     int base = 10;
  24
  25     int nDigit;
  26     int acc = 0;
  27
  28     while((nDigit = *s) != 0)
  29     {
  30         // Convert to digit
  31         nDigit -= '0';
  32         if(nDigit > 9)
  33             nDigit -= ('A' - '9' - 1);
  34         if(nDigit > base - 1)
  35             break;
  36
  37         // Move the value to the next rank and add the digit
  38         acc *= base;
  39         acc += nDigit;
  40         s ++;
  41     }
  42
  43     if(endptr != 0)
  44         *endptr = (char *) s;
  45
  46     return acc;
  47 }