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 #include <errno.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include "pathconv.h" /* prototypes */
30 /*
31 * abs2rel: convert an absolute path name into relative.
32 *
33 * i) path absolute path
34 * i) base base directory (must be absolute path)
35 * o) result result buffer
36 * i) size size of result buffer
37 * r) != NULL: relative path
38 * == NULL: error
39 */
40 char *
abs2rel(const char * path,const char * base,char * result,const size_t size)41 abs2rel(const char *path, const char *base, char *result, const size_t size)
42 {
43 const char *pp, *bp, *branch;
44 /*
45 * endp points the last position which is safe in the result buffer.
46 */
47 const char *endp = result + size - 1;
48 char *rp;
49
50 if (*path != '/') {
51 if (strlen(path) >= size)
52 goto erange;
53 strcpy(result, path);
54 goto finish;
55 } else if (*base != '/' || !size) {
56 errno = EINVAL;
57 return (NULL);
58 } else if (size == 1)
59 goto erange;
60 /*
61 * seek to branched point.
62 */
63 branch = path;
64 for (pp = path, bp = base; *pp && *bp && *pp == *bp; pp++, bp++)
65 if (*pp == '/')
66 branch = pp;
67 if ((*pp == 0 || (*pp == '/' && *(pp + 1) == 0)) &&
68 (*bp == 0 || (*bp == '/' && *(bp + 1) == 0))) {
69 rp = result;
70 *rp++ = '.';
71 if (*pp == '/' || *(pp - 1) == '/')
72 *rp++ = '/';
73 if (rp > endp)
74 goto erange;
75 *rp = 0;
76 goto finish;
77 }
78 if ((*pp == 0 && *bp == '/') || (*pp == '/' && *bp == 0))
79 branch = pp;
80 /*
81 * up to root.
82 */
83 rp = result;
84 for (bp = base + (branch - path); *bp; bp++)
85 if (*bp == '/' && *(bp + 1) != 0) {
86 if (rp + 3 > endp)
87 goto erange;
88 *rp++ = '.';
89 *rp++ = '.';
90 *rp++ = '/';
91 }
92 if (rp > endp)
93 goto erange;
94 *rp = 0;
95 /*
96 * down to leaf.
97 */
98 if (*branch) {
99 if (rp + strlen(branch + 1) > endp)
100 goto erange;
101 strcpy(rp, branch + 1);
102 } else
103 *--rp = 0;
104 finish:
105 return result;
106 erange:
107 errno = ERANGE;
108 return (NULL);
109 }
110