string/strtok.c

   1 /* Copyright (C) 1991, 1996 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17 Boston, MA 02111-1307, USA.  */
  18
  19 #include <errno.h>
  20 #include <string.h>
  21
  22
  23 static char *olds = NULL;
  24
  25 /* Parse S into tokens separated by characters in DELIM.
  26    If S is NULL, the last string strtok() was called with is
  27    used.  For example:
  28         char s[] = "-abc-=-def";
  29         x = strtok(s, "-");             // x = "abc"
  30         x = strtok(NULL, "-=");         // x = "def"
  31         x = strtok(NULL, "=");          // x = NULL
  32                 // s = "abc\0-def\0"
  33 */
  34 char *
  35 strtok (s, delim)
  36      char *s;
  37      const char *delim;
  38 {
  39   char *token;
  40
  41   if (s == NULL)
  42     {
  43       if (olds == NULL)
  44         {
  45           errno = EINVAL;
  46           return NULL;
  47         }
  48       else
  49         s = olds;
  50     }
  51
  52   /* Scan leading delimiters.  */
  53   s += strspn (s, delim);
  54   if (*s == '\0')
  55     {
  56       olds = NULL;
  57       return NULL;
  58     }
  59
  60   /* Find the end of the token.  */
  61   token = s;
  62   s = strpbrk (token, delim);
  63   if (s == NULL)
  64     /* This token finishes the string.  */
  65     olds = NULL;
  66   else
  67     {
  68       /* Terminate the token and make OLDS point past it.  */
  69       *s = '\0';
  70       olds = s + 1;
  71     }
  72   return token;
  73 }