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 * 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