1 /* $NetBSD: getcwd.c,v 1.4 1995/02/27 04:12:20 cgd Exp $ */ 2 3 /* 4 * Copyright (c) 1989, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #if defined(LIBC_SCCS) && !defined(lint) 37 #if 0 38 static char sccsid[] = "@(#)getcwd.c 8.1 (Berkeley) 6/4/93"; 39 #else 40 static char rcsid[] = "$NetBSD: getcwd.c,v 1.4 1995/02/27 04:12:20 cgd Exp $"; 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 #include <sys/param.h> 45 #include <sys/stat.h> 46 47 #include <errno.h> 48 #include <dirent.h> 49 #include <stdio.h> 50 #include <stdlib.h> 51 #include <string.h> 52 #include <unistd.h> 53 54 #define ISDOT(dp) \ 55 (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \ 56 dp->d_name[1] == '.' && dp->d_name[2] == '\0')) 57 58 char * 59 getcwd(pt, size) 60 char *pt; 61 size_t size; 62 { 63 register struct dirent *dp; 64 register DIR *dir; 65 register dev_t dev; 66 register ino_t ino; 67 register int first; 68 register char *bpt, *bup; 69 struct stat s; 70 dev_t root_dev; 71 ino_t root_ino; 72 size_t ptsize, upsize; 73 int save_errno; 74 char *ept, *eup, *up; 75 76 /* 77 * If no buffer specified by the user, allocate one as necessary. 78 * If a buffer is specified, the size has to be non-zero. The path 79 * is built from the end of the buffer backwards. 80 */ 81 if (pt) { 82 ptsize = 0; 83 if (!size) { 84 errno = EINVAL; 85 return (NULL); 86 } 87 ept = pt + size; 88 } else { 89 if ((pt = malloc(ptsize = 1024 - 4)) == NULL) 90 return (NULL); 91 ept = pt + ptsize; 92 } 93 bpt = ept - 1; 94 *bpt = '\0'; 95 96 /* 97 * Allocate bytes (1024 - malloc space) for the string of "../"'s. 98 * Should always be enough (it's 340 levels). If it's not, allocate 99 * as necessary. Special * case the first stat, it's ".", not "..". 100 */ 101 if ((up = malloc(upsize = 1024 - 4)) == NULL) 102 goto err; 103 eup = up + MAXPATHLEN; 104 bup = up; 105 up[0] = '.'; 106 up[1] = '\0'; 107 108 /* Save root values, so know when to stop. */ 109 if (stat("/", &s)) 110 goto err; 111 root_dev = s.st_dev; 112 root_ino = s.st_ino; 113 114 errno = 0; /* XXX readdir has no error return. */ 115 116 for (first = 1;; first = 0) { 117 /* Stat the current level. */ 118 if (lstat(up, &s)) 119 goto err; 120 121 /* Save current node values. */ 122 ino = s.st_ino; 123 dev = s.st_dev; 124 125 /* Check for reaching root. */ 126 if (root_dev == dev && root_ino == ino) { 127 *--bpt = '/'; 128 /* 129 * It's unclear that it's a requirement to copy the 130 * path to the beginning of the buffer, but it's always 131 * been that way and stuff would probably break. 132 */ 133 (void)bcopy(bpt, pt, ept - bpt); 134 free(up); 135 return (pt); 136 } 137 138 /* 139 * Build pointer to the parent directory, allocating memory 140 * as necessary. Max length is 3 for "../", the largest 141 * possible component name, plus a trailing NULL. 142 */ 143 if (bup + 3 + MAXNAMLEN + 1 >= eup) { 144 if ((up = realloc(up, upsize *= 2)) == NULL) 145 goto err; 146 bup = up; 147 eup = up + upsize; 148 } 149 *bup++ = '.'; 150 *bup++ = '.'; 151 *bup = '\0'; 152 153 /* Open and stat parent directory. */ 154 if (!(dir = opendir(up)) || fstat(dirfd(dir), &s)) 155 goto err; 156 157 /* Add trailing slash for next directory. */ 158 *bup++ = '/'; 159 160 /* 161 * If it's a mount point, have to stat each element because 162 * the inode number in the directory is for the entry in the 163 * parent directory, not the inode number of the mounted file. 164 */ 165 save_errno = 0; 166 if (s.st_dev == dev) { 167 for (;;) { 168 if (!(dp = readdir(dir))) 169 goto notfound; 170 if (dp->d_fileno == ino) 171 break; 172 } 173 } else 174 for (;;) { 175 if (!(dp = readdir(dir))) 176 goto notfound; 177 if (ISDOT(dp)) 178 continue; 179 bcopy(dp->d_name, bup, dp->d_namlen + 1); 180 181 /* Save the first error for later. */ 182 if (lstat(up, &s)) { 183 if (!save_errno) 184 save_errno = errno; 185 errno = 0; 186 continue; 187 } 188 if (s.st_dev == dev && s.st_ino == ino) 189 break; 190 } 191 192 /* 193 * Check for length of the current name, preceding slash, 194 * leading slash. 195 */ 196 if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) { 197 size_t len, off; 198 199 if (!ptsize) { 200 errno = ERANGE; 201 goto err; 202 } 203 off = bpt - pt; 204 len = ept - bpt; 205 if ((pt = realloc(pt, ptsize *= 2)) == NULL) 206 goto err; 207 bpt = pt + off; 208 ept = pt + ptsize; 209 (void)bcopy(bpt, ept - len, len); 210 bpt = ept - len; 211 } 212 if (!first) 213 *--bpt = '/'; 214 bpt -= dp->d_namlen; 215 bcopy(dp->d_name, bpt, dp->d_namlen); 216 (void)closedir(dir); 217 218 /* Truncate any file name. */ 219 *bup = '\0'; 220 } 221 222 notfound: 223 /* 224 * If readdir set errno, use it, not any saved error; otherwise, 225 * didn't find the current directory in its parent directory, set 226 * errno to ENOENT. 227 */ 228 if (!errno) 229 errno = save_errno ? save_errno : ENOENT; 230 /* FALLTHROUGH */ 231 err: 232 if (ptsize) 233 free(pt); 234 free(up); 235 return (NULL); 236 } 237