lib/libc/atoi.c

   1 /* $Id: atoi.c,v 1.1.1.1 2006/09/14 01:59:06 root Exp $ */
   2
   3 /*
   4  * Copyright (c) 2000-2002 Opsycon AB  (www.opsycon.se)
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 3. All advertising materials mentioning features or use of this software
  15  *    must display the following acknowledgement:
  16  *      This product includes software developed by Opsycon AB.
  17  * 4. The name of the author may not be used to endorse or promote products
  18  *    derived from this software without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
  21  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  22  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  24  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  */
  33
  34 #include <string.h>
  35 #include <stdlib.h>
  36 #include <ctype.h>
  37
  38 /** atoi(p) converts p to int */
  39
  40 int32_t
  41 atoi(const char *p)
  42 {
  43         int32_t digit, isneg;
  44         int32_t value;
  45
  46         isneg = 0;
  47         value = 0;
  48         for (; isspace (*p); p++);      /* gobble up leading whitespace */
  49
  50         /* do I have a sign? */
  51         if (*p == '-') {
  52                 isneg = 1;
  53                 p++;
  54         }
  55         else if (*p == '+')
  56                 p++;
  57
  58         for (; *p; p++) {
  59                 if (*p >= '0' && *p <= '9')
  60                         digit = *p - '0';
  61                 else
  62                         break;
  63                 value *= 10;
  64                 value += digit;
  65         }
  66
  67         if (isneg)
  68                 value = 0 - value;
  69         return (value);
  70 }