Annotation of src/lib/libc/gen/getcwd.c, Revision 1.1.1.1
1.1 cgd 1: /*
2: * Copyright (c) 1989, 1991 The Regents of the University of California.
3: * 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: * 3. All advertising materials mentioning features or use of this software
14: * must display the following acknowledgement:
15: * This product includes software developed by the University of
16: * California, Berkeley and its contributors.
17: * 4. Neither the name of the University nor the names of its contributors
18: * may be used to endorse or promote products derived from this software
19: * without specific prior written permission.
20: *
21: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31: * SUCH DAMAGE.
32: */
33:
34: #if defined(LIBC_SCCS) && !defined(lint)
35: static char sccsid[] = "@(#)getcwd.c 5.11 (Berkeley) 2/24/91";
36: #endif /* LIBC_SCCS and not lint */
37:
38: #include <sys/param.h>
39: #include <sys/stat.h>
40: #include <errno.h>
41: #include <dirent.h>
42: #include <stdio.h>
43: #include <stdlib.h>
44: #include <string.h>
45: #include <unistd.h>
46:
47: #define ISDOT(dp) \
48: (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
49: dp->d_name[1] == '.' && dp->d_name[2] == '\0'))
50:
51: char *
52: getcwd(pt, size)
53: char *pt;
54: size_t size;
55: {
56: register struct dirent *dp;
57: register DIR *dir;
58: register dev_t dev;
59: register ino_t ino;
60: register int first;
61: register char *bpt, *bup;
62: struct stat s;
63: dev_t root_dev;
64: ino_t root_ino;
65: size_t ptsize, upsize;
66: int save_errno;
67: char *ept, *eup, *up;
68:
69: /*
70: * If no buffer specified by the user, allocate one as necessary.
71: * If a buffer is specified, the size has to be non-zero. The path
72: * is built from the end of the buffer backwards.
73: */
74: if (pt) {
75: ptsize = 0;
76: if (!size) {
77: errno = EINVAL;
78: return((char *)NULL);
79: }
80: ept = pt + size;
81: } else {
82: if (!(pt = (char *)malloc(ptsize = 1024 - 4)))
83: return((char *)NULL);
84: ept = pt + ptsize;
85: }
86: bpt = ept - 1;
87: *bpt = '\0';
88:
89: /*
90: * Allocate bytes (1024 - malloc space) for the string of "../"'s.
91: * Should always be enough (it's 340 levels). If it's not, allocate
92: * as necessary. Special * case the first stat, it's ".", not "..".
93: */
94: if (!(up = (char *)malloc(upsize = 1024 - 4)))
95: goto err;
96: eup = up + MAXPATHLEN;
97: bup = up;
98: up[0] = '.';
99: up[1] = '\0';
100:
101: /* Save root values, so know when to stop. */
102: if (stat("/", &s))
103: goto err;
104: root_dev = s.st_dev;
105: root_ino = s.st_ino;
106:
107: errno = 0; /* XXX readdir has no error return. */
108:
109: for (first = 1;; first = 0) {
110: /* Stat the current level. */
111: if (lstat(up, &s))
112: goto err;
113:
114: /* Save current node values. */
115: ino = s.st_ino;
116: dev = s.st_dev;
117:
118: /* Check for reaching root. */
119: if (root_dev == dev && root_ino == ino) {
120: *--bpt = '/';
121: /*
122: * It's unclear that it's a requirement to copy the
123: * path to the beginning of the buffer, but it's always
124: * been that way and stuff would probably break.
125: */
126: (void)bcopy(bpt, pt, ept - bpt);
127: free(up);
128: return(pt);
129: }
130:
131: /*
132: * Build pointer to the parent directory, allocating memory
133: * as necessary. Max length is 3 for "../", the largest
134: * possible component name, plus a trailing NULL.
135: */
136: if (bup + 3 + MAXNAMLEN + 1 >= eup) {
137: if (!(up = (char *)realloc(up, upsize *= 2)))
138: goto err;
139: eup = up + upsize;
140: }
141: *bup++ = '.';
142: *bup++ = '.';
143: *bup = '\0';
144:
145: /* Open and stat parent directory. */
146: if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
147: goto err;
148:
149: /* Add trailing slash for next directory. */
150: *bup++ = '/';
151:
152: /*
153: * If it's a mount point, have to stat each element because
154: * the inode number in the directory is for the entry in the
155: * parent directory, not the inode number of the mounted file.
156: */
157: save_errno = 0;
158: if (s.st_dev == dev) {
159: for (;;) {
160: if (!(dp = readdir(dir)))
161: goto notfound;
162: if (dp->d_fileno == ino)
163: break;
164: }
165: } else
166: for (;;) {
167: if (!(dp = readdir(dir)))
168: goto notfound;
169: if (ISDOT(dp))
170: continue;
171: bcopy(dp->d_name, bup, dp->d_namlen + 1);
172:
173: /* Save the first error for later. */
174: if (lstat(up, &s)) {
175: if (!save_errno)
176: save_errno = errno;
177: errno = 0;
178: continue;
179: }
180: if (s.st_dev == dev && s.st_ino == ino)
181: break;
182: }
183:
184: /*
185: * Check for length of the current name, preceding slash,
186: * leading slash.
187: */
188: if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
189: size_t len, off;
190:
191: if (!ptsize) {
192: errno = ERANGE;
193: goto err;
194: }
195: off = bpt - pt;
196: len = ept - bpt;
197: if (!(pt = (char *)realloc(pt, ptsize *= 2)))
198: goto err;
199: bpt = pt + off;
200: ept = pt + ptsize;
201: (void)bcopy(bpt, ept - len, len);
202: bpt = ept - len;
203: }
204: if (!first)
205: *--bpt = '/';
206: bpt -= dp->d_namlen;
207: bcopy(dp->d_name, bpt, dp->d_namlen);
208: (void)closedir(dir);
209:
210: /* Truncate any file name. */
211: *bup = '\0';
212: }
213:
214: notfound:
215: /*
216: * If readdir set errno, use it, not any saved error; otherwise,
217: * didn't find the current directory in its parent directory, set
218: * errno to ENOENT.
219: */
220: if (!errno)
221: errno = save_errno ? save_errno : ENOENT;
222: /* FALLTHROUGH */
223: err:
224: if (ptsize)
225: free(pt);
226: free(up);
227: return((char *)NULL);
228: }
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