nuttx/lib/string/lib_strtokr.c

/****************************************************************************
 * lib/string/lib_strtokr.c
 *
 *   Copyright (C) 2007, 2008, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <string.h>

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: strtok_r
 *
 * Description:
 *   The strtok_r() function is a reentrant version strtok().
 *   Like strtok(), it  parses  a string into a sequence of
 *   tokens.  On the first call to strtok() the string to be
 *   parsed should be specified in 'str'.  In each subsequent
 *   call that should parse the same string, 'str' should be
 *   NULL.
 *
 *   The 'saveptr' argument is a pointer to a char *
 *   variable  that  is  used internally by strtok_r() in
 *   order to maintain context between successive calls
 *   that parse the same string.
 *
 *   On the first call to strtok_r(), 'str' should point to the
 *   string to be parsed, and the value of 'saveptr' is 
 *   ignored.  In subsequent calls, 'str' should be NULL, and
 *   saveptr should be unchanged since the previous call.
 *
 *   The 'delim' argument specifies a set of characters that
 *   delimit the tokens in the parsed string.  The caller
 *   may specify different strings in delim in successive
 *   calls that parse the same string.
 *
 *   Each call to strtok_r() returns a pointer to a null-
 *   terminated string containing the next token. This
 *   string  does not include the delimiting character.  If
 *   no more tokens are found, strtok_r() returns NULL.
 *
 *   A sequence of two or more contiguous delimiter
 *   characters in the parsed string is considered to be a
 *   single delimiter. Delimiter characters at the start or
 *   end of the string are ignored.  The tokens returned by
 *   strtok() are always non-empty strings.
 *
 * Return
 *    strtok_r() returns a pointer to the next token, or NULL
 *    if there are no more tokens.
 *
 ****************************************************************************/

char *strtok_r(char *str, const char *delim, char **saveptr)
{
  char *pbegin;
  char *pend = NULL;

  /* Decide if we are starting a new string or continuing from
   * the point we left off.
   */

  if (str)
    {
      pbegin = str;
    }
  else if (saveptr && *saveptr)
    {
      pbegin = *saveptr;
    }
  else
    {
      return NULL;
    }

  /* Find the beginning of the next token */

  for (;
       *pbegin && strchr(delim, *pbegin) != NULL;
       pbegin++);

  /* If we are at the end of the string with nothing
   * but delimiters found, then return NULL.
   */

  if (!*pbegin)
    {
      return NULL;
    }

  /* Find the end of the token */

  for (pend = pbegin + 1;
       *pend && strchr(delim, *pend) == NULL;
       pend++);


  /* pend either points to the end of the string or to
   * the first delimiter after the string.
   */

  if (*pend)
    {
      /* Turn the delimiter into a null terminator */

      *pend++ = '\0';
    }

  /* Save the pointer where we left off and return the
   * beginning of the token.
   */

  if (saveptr)
    {
      *saveptr = pend;
    }
  return pbegin;
}