cs350/common/libc/string/strtok_r.c

/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *	The President and Fellows of Harvard College.
 *
 * 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 of the University 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 UNIVERSITY 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 UNIVERSITY 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.
 */

/*
 * This file is shared between libc and the kernel, so don't put anything
 * in here that won't work in both contexts.
 */

#ifdef _KERNEL
#include <types.h>
#include <lib.h>
#else
#include <string.h>
#endif

/*
 * Standard C string function: tokenize a string splitting based on a
 * list of separator characters. Reentrant version.
 *
 * The "context" argument should point to a "char *" that is preserved
 * between calls to strtok_r that wish to operate on same string.
 */
char *
strtok_r(char *string, const char *seps, char **context)
{
	char *head;  /* start of word */
	char *tail;  /* end of word */

	/* If we're starting up, initialize context */
	if (string) {
		*context = string;
	}

	/* Get potential start of this next word */
	head = *context;
	if (head == NULL) {
		return NULL;
	}

	/* Skip any leading separators */
	while (*head && strchr(seps, *head)) {
		head++;
	}

	/* Did we hit the end? */
	if (*head == 0) {
		/* Nothing left */
		*context = NULL;
		return NULL;
	}

	/* skip over word */
	tail = head;
	while (*tail && !strchr(seps, *tail)) {
		tail++;
	}

	/* Save head for next time in context */
	if (*tail == 0) {
		*context = NULL;
	}
	else {
		*tail = 0;
		tail++;
		*context = tail;
	}

	/* Return current word */
	return head;
}