abs2rel.c

代码检索工具GLOBAL源码。可用来浏览分析LINUX源码。

/*
 * Copyright (c) 1997, 1999 Tama Communications Corporation
 *
 * This file is part of GNU GLOBAL.
 *
 * GNU GLOBAL 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; either version 2, or (at your option)
 * any later version.
 *
 * GNU GLOBAL is distributed in the hope that it will 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 to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <errno.h>
#ifdef STDC_HEADERS
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif

#include "abs2rel.h"

/*
 * abs2rel: convert an absolute path name into relative.
 *
 *	i)	path	absolute path
 *	i)	base	base directory (must be absolute path)
 *	o)	result	result buffer
 *	i)	size	size of result buffer
 *	r)		!= NULL: relative path
 *			== NULL: error
 */
char *
abs2rel(path, base, result, size)
	const char *path;
	const char *base;
	char *result;
	const int size;
{
	const char *pp, *bp, *branch;
	/*
	 * endp points the last position which is safe in the result buffer.
	 */
	const char *endp = result + size - 1;
	char *rp;

	if (*path != '/') {
		if (strlen(path) >= size)
			goto erange;
		strcpy(result, path);
		goto finish;
	} else if (*base != '/' || !size) {
		errno = EINVAL;
		return (NULL);
	} else if (size == 1)
		goto erange;
	/*
	 * seek to branched point.
	 */
	branch = path;
	for (pp = path, bp = base; *pp && *bp && *pp == *bp; pp++, bp++)
		if (*pp == '/')
			branch = pp;
	if ((*pp == 0 || (*pp == '/' && *(pp + 1) == 0)) &&
	    (*bp == 0 || (*bp == '/' && *(bp + 1) == 0))) {
		rp = result;
		*rp++ = '.';
		if (*pp == '/' || *(pp - 1) == '/')
			*rp++ = '/';
		if (rp > endp)
			goto erange;
		*rp = 0;
		goto finish;
	}
	if ((*pp == 0 && *bp == '/') || (*pp == '/' && *bp == 0))
		branch = pp;
	/*
	 * up to root.
	 */
	rp = result;
	for (bp = base + (branch - path); *bp; bp++)
		if (*bp == '/' && *(bp + 1) != 0) {
			if (rp + 3 > endp)
				goto erange;
			*rp++ = '.';
			*rp++ = '.';
			*rp++ = '/';
		}
	if (rp > endp)
		goto erange;
	*rp = 0;
	/*
	 * down to leaf.
	 */
	if (*branch) {
		if (rp + strlen(branch + 1) > endp)
			goto erange;
		strcpy(rp, branch + 1);
	} else
		*--rp = 0;
finish:
	return result;
erange:
	errno = ERANGE;
	return (NULL);
}