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PR/52499: Justin: stresep uses memmove with of-by-one length

/*	$NetBSD: stresep.c,v 1.4 2017/08/23 10:27:41 christos Exp $	*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * 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 REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)strsep.c	8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: stresep.c,v 1.4 2017/08/23 10:27:41 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"

#include <assert.h>
#include <string.h>

#ifdef __weak_alias
__weak_alias(stresep,_stresep)
#endif

/*
 * Get next token from string *stringp, where tokens are possibly-empty
 * strings separated by characters from delim. If esc is not NUL, then
 * the characters followed by esc are ignored and are not taken into account
 * when splitting the string.
 *
 * Writes NULs into the string at *stringp to end tokens.
 * delim need not remain constant from call to call.
 * On return, *stringp points past the last NUL written (if there might
 * be further tokens), or is NULL (if there are definitely no more tokens).
 *
 * If *stringp is NULL, stresep returns NULL.
 */
char *
stresep(char **stringp, const char *delim, int esc)
{
	char *s;
	const char *spanp;
	int c, sc;
	size_t l;
	char *tok;

	_DIAGASSERT(stringp != NULL);
	_DIAGASSERT(delim != NULL);

	if ((s = *stringp) == NULL)
		return NULL;
	l = strlen(s) + 1;
	for (tok = s;;) {
		c = *s++;
		l--;
		while (esc != '\0' && c == esc) {
			memmove(s - 1, s, l);
			c = *s++;
			l--;
		}
		spanp = delim;
		do {
			if ((sc = *spanp++) == c) {
				if (c == '\0')
					s = NULL;
				else
					s[-1] = '\0';
				*stringp = s;
				return tok;
			}
		} while (sc != '\0');
	}
}