xref: /freebsd/lib/libpathconv/rel2abs.c (revision c66ec88fed842fbaad62c30d510644ceb7bd2d71)
1 /*
2  * Copyright (c) 1997 Shigio Yamaguchi. All rights reserved.
3  * Copyright (c) 1999 Tama Communications Corporation. All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  *
26  * $FreeBSD$
27  */
28 #include <errno.h>
29 #include <stdlib.h>
30 #include <string.h>
31 #include "pathconv.h" /* prototypes */
32 /*
33  * rel2abs: convert an relative path name into absolute.
34  *
35  *	i)	path	relative path
36  *	i)	base	base directory (must be absolute path)
37  *	o)	result	result buffer
38  *	i)	size	size of result buffer
39  *	r)		!= NULL: absolute path
40  *			== NULL: error
41  */
42 char *
43 rel2abs(const char *path, const char *base, char *result, const size_t size)
44 {
45 	const char *pp, *bp;
46 	/*
47 	 * endp points the last position which is safe in the result buffer.
48 	 */
49 	const char *endp = result + size - 1;
50 	char *rp;
51 	size_t length;
52 
53 	if (*path == '/') {
54 		if (strlen(path) >= size)
55 			goto erange;
56 		strcpy(result, path);
57 		goto finish;
58 	} else if (*base != '/' || !size) {
59 		errno = EINVAL;
60 		return (NULL);
61 	} else if (size == 1)
62 		goto erange;
63 
64 	length = strlen(base);
65 
66 	if (!strcmp(path, ".") || !strcmp(path, "./")) {
67 		if (length >= size)
68 			goto erange;
69 		strcpy(result, base);
70 		/*
71 		 * rp points the last char.
72 		 */
73 		rp = result + length - 1;
74 		/*
75 		 * remove the last '/'.
76 		 */
77 		if (*rp == '/') {
78 			if (length > 1)
79 				*rp = 0;
80 		} else
81 			rp++;
82 		/* rp point NULL char */
83 		if (*++path == '/') {
84 			/*
85 			 * Append '/' to the tail of path name.
86 			 */
87 			*rp++ = '/';
88 			if (rp > endp)
89 				goto erange;
90 			*rp = 0;
91 		}
92 		goto finish;
93 	}
94 	bp = base + length;
95 	if (*(bp - 1) == '/')
96 		--bp;
97 	/*
98 	 * up to root.
99 	 */
100 	for (pp = path; *pp && *pp == '.'; ) {
101 		if (!strncmp(pp, "../", 3)) {
102 			pp += 3;
103 			while (bp > base && *--bp != '/')
104 				;
105 		} else if (!strncmp(pp, "./", 2)) {
106 			pp += 2;
107 		} else if (!strncmp(pp, "..\0", 3)) {
108 			pp += 2;
109 			while (bp > base && *--bp != '/')
110 				;
111 		} else
112 			break;
113 	}
114 	/*
115 	 * down to leaf.
116 	 */
117 	length = bp - base;
118 	if (length >= size)
119 		goto erange;
120 	strncpy(result, base, length);
121 	rp = result + length;
122 	if (*pp || *(pp - 1) == '/' || length == 0)
123 		*rp++ = '/';
124 	if (rp + strlen(pp) > endp)
125 		goto erange;
126 	strcpy(rp, pp);
127 finish:
128 	return result;
129 erange:
130 	errno = ERANGE;
131 	return (NULL);
132 }
133