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 * 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