overlayfs.c

/*
 * overlayfs.c - Common functions of overlayfs from the Linux kernel
 *
 * Copyright (c) 2017 Huawei.  All Rights Reserved.
 * Author: zhangyi (F) <yi.zhang@huawei.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <stddef.h>

/*
 * Split directories to individual one.
 * (copied from linux kernel, see fs/overlayfs/super.c)
 */
unsigned int ovl_split_lowerdirs(char *lower)
{
	unsigned int ctr = 1;
	char *s, *d;

	for (s = d = lower;; s++, d++) {
		if (*s == '\\') {
			s++;
		} else if (*s == ':') {
			*d = '\0';
			ctr++;
			continue;
		}
		*d = *s;
		if (!*s)
			break;
	}
	return ctr;
}

/*
 * Split and return next opt.
 * (copied from linux kernel, see fs/overlayfs/super.c)
 */
char *ovl_next_opt(char **s)
{
	char *sbegin = *s;
	char *p;

	if (sbegin == NULL)
		return NULL;

	for (p = sbegin; *p; p++) {
		if (*p == '\\') {
			p++;
			if (!*p)
				break;
		} else if (*p == ',') {
			*p = '\0';
			*s = p + 1;
			return sbegin;
		}
	}
	*s = NULL;
	return sbegin;
}