1 /* 2 * Copyright (c) 1989, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #if defined(LIBC_SCCS) && !defined(lint) 9 static char sccsid[] = "@(#)getcwd.c 8.1 (Berkeley) 06/04/93"; 10 #endif /* LIBC_SCCS and not lint */ 11 12 #include <sys/param.h> 13 #include <sys/stat.h> 14 15 #include <errno.h> 16 #include <dirent.h> 17 #include <stdio.h> 18 #include <stdlib.h> 19 #include <string.h> 20 #include <unistd.h> 21 22 #define ISDOT(dp) \ 23 (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \ 24 dp->d_name[1] == '.' && dp->d_name[2] == '\0')) 25 26 char * 27 getcwd(pt, size) 28 char *pt; 29 size_t size; 30 { 31 register struct dirent *dp; 32 register DIR *dir; 33 register dev_t dev; 34 register ino_t ino; 35 register int first; 36 register char *bpt, *bup; 37 struct stat s; 38 dev_t root_dev; 39 ino_t root_ino; 40 size_t ptsize, upsize; 41 int save_errno; 42 char *ept, *eup, *up; 43 44 /* 45 * If no buffer specified by the user, allocate one as necessary. 46 * If a buffer is specified, the size has to be non-zero. The path 47 * is built from the end of the buffer backwards. 48 */ 49 if (pt) { 50 ptsize = 0; 51 if (!size) { 52 errno = EINVAL; 53 return (NULL); 54 } 55 ept = pt + size; 56 } else { 57 if ((pt = malloc(ptsize = 1024 - 4)) == NULL) 58 return (NULL); 59 ept = pt + ptsize; 60 } 61 bpt = ept - 1; 62 *bpt = '\0'; 63 64 /* 65 * Allocate bytes (1024 - malloc space) for the string of "../"'s. 66 * Should always be enough (it's 340 levels). If it's not, allocate 67 * as necessary. Special * case the first stat, it's ".", not "..". 68 */ 69 if ((up = malloc(upsize = 1024 - 4)) == NULL) 70 goto err; 71 eup = up + MAXPATHLEN; 72 bup = up; 73 up[0] = '.'; 74 up[1] = '\0'; 75 76 /* Save root values, so know when to stop. */ 77 if (stat("/", &s)) 78 goto err; 79 root_dev = s.st_dev; 80 root_ino = s.st_ino; 81 82 errno = 0; /* XXX readdir has no error return. */ 83 84 for (first = 1;; first = 0) { 85 /* Stat the current level. */ 86 if (lstat(up, &s)) 87 goto err; 88 89 /* Save current node values. */ 90 ino = s.st_ino; 91 dev = s.st_dev; 92 93 /* Check for reaching root. */ 94 if (root_dev == dev && root_ino == ino) { 95 *--bpt = '/'; 96 /* 97 * It's unclear that it's a requirement to copy the 98 * path to the beginning of the buffer, but it's always 99 * been that way and stuff would probably break. 100 */ 101 (void)bcopy(bpt, pt, ept - bpt); 102 free(up); 103 return (pt); 104 } 105 106 /* 107 * Build pointer to the parent directory, allocating memory 108 * as necessary. Max length is 3 for "../", the largest 109 * possible component name, plus a trailing NULL. 110 */ 111 if (bup + 3 + MAXNAMLEN + 1 >= eup) { 112 if ((up = realloc(up, upsize *= 2)) == NULL) 113 goto err; 114 bup = up; 115 eup = up + upsize; 116 } 117 *bup++ = '.'; 118 *bup++ = '.'; 119 *bup = '\0'; 120 121 /* Open and stat parent directory. */ 122 if (!(dir = opendir(up)) || fstat(dirfd(dir), &s)) 123 goto err; 124 125 /* Add trailing slash for next directory. */ 126 *bup++ = '/'; 127 128 /* 129 * If it's a mount point, have to stat each element because 130 * the inode number in the directory is for the entry in the 131 * parent directory, not the inode number of the mounted file. 132 */ 133 save_errno = 0; 134 if (s.st_dev == dev) { 135 for (;;) { 136 if (!(dp = readdir(dir))) 137 goto notfound; 138 if (dp->d_fileno == ino) 139 break; 140 } 141 } else 142 for (;;) { 143 if (!(dp = readdir(dir))) 144 goto notfound; 145 if (ISDOT(dp)) 146 continue; 147 bcopy(dp->d_name, bup, dp->d_namlen + 1); 148 149 /* Save the first error for later. */ 150 if (lstat(up, &s)) { 151 if (!save_errno) 152 save_errno = errno; 153 errno = 0; 154 continue; 155 } 156 if (s.st_dev == dev && s.st_ino == ino) 157 break; 158 } 159 160 /* 161 * Check for length of the current name, preceding slash, 162 * leading slash. 163 */ 164 if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) { 165 size_t len, off; 166 167 if (!ptsize) { 168 errno = ERANGE; 169 goto err; 170 } 171 off = bpt - pt; 172 len = ept - bpt; 173 if ((pt = realloc(pt, ptsize *= 2)) == NULL) 174 goto err; 175 bpt = pt + off; 176 ept = pt + ptsize; 177 (void)bcopy(bpt, ept - len, len); 178 bpt = ept - len; 179 } 180 if (!first) 181 *--bpt = '/'; 182 bpt -= dp->d_namlen; 183 bcopy(dp->d_name, bpt, dp->d_namlen); 184 (void)closedir(dir); 185 186 /* Truncate any file name. */ 187 *bup = '\0'; 188 } 189 190 notfound: 191 /* 192 * If readdir set errno, use it, not any saved error; otherwise, 193 * didn't find the current directory in its parent directory, set 194 * errno to ENOENT. 195 */ 196 if (!errno) 197 errno = save_errno ? save_errno : ENOENT; 198 /* FALLTHROUGH */ 199 err: 200 if (ptsize) 201 free(pt); 202 free(up); 203 return (NULL); 204 } 205