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 * abs2rel: convert an absolute path name into relative.
34 *
35 * i) path absolute 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: relative path
40 * == NULL: error
41 */
42 char *
abs2rel(const char * path,const char * base,char * result,const size_t size)43 abs2rel(const char *path, const char *base, char *result, const size_t size)
44 {
45 const char *pp, *bp, *branch;
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
52 if (*path != '/') {
53 if (strlen(path) >= size)
54 goto erange;
55 strcpy(result, path);
56 goto finish;
57 } else if (*base != '/' || !size) {
58 errno = EINVAL;
59 return (NULL);
60 } else if (size == 1)
61 goto erange;
62 /*
63 * seek to branched point.
64 */
65 branch = path;
66 for (pp = path, bp = base; *pp && *bp && *pp == *bp; pp++, bp++)
67 if (*pp == '/')
68 branch = pp;
69 if ((*pp == 0 || (*pp == '/' && *(pp + 1) == 0)) &&
70 (*bp == 0 || (*bp == '/' && *(bp + 1) == 0))) {
71 rp = result;
72 *rp++ = '.';
73 if (*pp == '/' || *(pp - 1) == '/')
74 *rp++ = '/';
75 if (rp > endp)
76 goto erange;
77 *rp = 0;
78 goto finish;
79 }
80 if ((*pp == 0 && *bp == '/') || (*pp == '/' && *bp == 0))
81 branch = pp;
82 /*
83 * up to root.
84 */
85 rp = result;
86 for (bp = base + (branch - path); *bp; bp++)
87 if (*bp == '/' && *(bp + 1) != 0) {
88 if (rp + 3 > endp)
89 goto erange;
90 *rp++ = '.';
91 *rp++ = '.';
92 *rp++ = '/';
93 }
94 if (rp > endp)
95 goto erange;
96 *rp = 0;
97 /*
98 * down to leaf.
99 */
100 if (*branch) {
101 if (rp + strlen(branch + 1) > endp)
102 goto erange;
103 strcpy(rp, branch + 1);
104 } else
105 *--rp = 0;
106 finish:
107 return result;
108 erange:
109 errno = ERANGE;
110 return (NULL);
111 }
112