1 /*
2 * Copyright (c) 1983, 1993
3 * The Regents of the University of California. 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 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #if defined(LIBC_SCCS) && !defined(lint)
31 static char sccsid[] = "@(#)telldir.c 8.1 (Berkeley) 6/4/93";
32 #endif /* LIBC_SCCS and not lint */
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
35
36 #include "namespace.h"
37 #include <sys/param.h>
38 #include <sys/queue.h>
39 #include <dirent.h>
40 #include <pthread.h>
41 #include <stdlib.h>
42 #include <unistd.h>
43 #include "un-namespace.h"
44
45 #include "libc_private.h"
46 #include "gen-private.h"
47 #include "telldir.h"
48
49 /*
50 * return a pointer into a directory
51 */
52 long
telldir(DIR * dirp)53 telldir(DIR *dirp)
54 {
55 struct ddloc_mem *lp, *flp;
56 union ddloc_packed ddloc;
57
58 if (__isthreaded)
59 _pthread_mutex_lock(&dirp->dd_lock);
60 /*
61 * Outline:
62 * 1) If the directory position fits in a packed structure, return that.
63 * 2) Otherwise, see if it's already been recorded in the linked list
64 * 3) Otherwise, malloc a new one
65 */
66 if (dirp->dd_seek < (1ul << DD_SEEK_BITS) &&
67 dirp->dd_loc < (1ul << DD_LOC_BITS)) {
68 ddloc.s.is_packed = 1;
69 ddloc.s.loc = dirp->dd_loc;
70 ddloc.s.seek = dirp->dd_seek;
71 goto out;
72 }
73
74 flp = NULL;
75 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
76 if (lp->loc_seek == dirp->dd_seek) {
77 if (flp == NULL)
78 flp = lp;
79 if (lp->loc_loc == dirp->dd_loc)
80 break;
81 } else if (flp != NULL) {
82 lp = NULL;
83 break;
84 }
85 }
86 if (lp == NULL) {
87 lp = malloc(sizeof(struct ddloc_mem));
88 if (lp == NULL) {
89 if (__isthreaded)
90 _pthread_mutex_unlock(&dirp->dd_lock);
91 return (-1);
92 }
93 lp->loc_index = dirp->dd_td->td_loccnt++;
94 lp->loc_seek = dirp->dd_seek;
95 lp->loc_loc = dirp->dd_loc;
96 if (flp != NULL)
97 LIST_INSERT_BEFORE(flp, lp, loc_lqe);
98 else
99 LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
100 }
101 ddloc.i.is_packed = 0;
102 /*
103 * Technically this assignment could overflow on 32-bit architectures,
104 * but we would get ENOMEM long before that happens.
105 */
106 ddloc.i.index = lp->loc_index;
107
108 out:
109 if (__isthreaded)
110 _pthread_mutex_unlock(&dirp->dd_lock);
111 return (ddloc.l);
112 }
113
114 /*
115 * seek to an entry in a directory.
116 * Only values returned by "telldir" should be passed to seekdir.
117 */
118 void
_seekdir(DIR * dirp,long loc)119 _seekdir(DIR *dirp, long loc)
120 {
121 struct ddloc_mem *lp;
122 struct dirent *dp;
123 union ddloc_packed ddloc;
124 off_t loc_seek;
125 long loc_loc;
126
127 ddloc.l = loc;
128
129 if (ddloc.s.is_packed) {
130 loc_seek = ddloc.s.seek;
131 loc_loc = ddloc.s.loc;
132 } else {
133 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
134 if (lp->loc_index == ddloc.i.index)
135 break;
136 }
137 if (lp == NULL)
138 return;
139
140 loc_seek = lp->loc_seek;
141 loc_loc = lp->loc_loc;
142 }
143 if (loc_loc == dirp->dd_loc && loc_seek == dirp->dd_seek)
144 return;
145
146 /* If it's within the same chunk of data, don't bother reloading. */
147 if (loc_seek == dirp->dd_seek) {
148 /*
149 * If we go back to 0 don't make the next readdir
150 * trigger a call to getdirentries().
151 */
152 if (loc_loc == 0)
153 dirp->dd_flags |= __DTF_SKIPREAD;
154 dirp->dd_loc = loc_loc;
155 return;
156 }
157 (void) lseek(dirp->dd_fd, (off_t)loc_seek, SEEK_SET);
158 dirp->dd_seek = loc_seek;
159 dirp->dd_loc = 0;
160 dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */
161 while (dirp->dd_loc < loc_loc) {
162 dp = _readdir_unlocked(dirp, 0);
163 if (dp == NULL)
164 break;
165 }
166 }
167
168 /*
169 * After readdir returns the last entry in a block, a call to telldir
170 * returns a location that is after the end of that last entry.
171 * However, that location doesn't refer to a valid directory entry.
172 * Ideally, the call to telldir would return a location that refers to
173 * the first entry in the next block. That location is not known
174 * until the next block is read, so readdir calls this function after
175 * fetching a new block to fix any such telldir locations.
176 */
177 void
_fixtelldir(DIR * dirp,long oldseek,long oldloc)178 _fixtelldir(DIR *dirp, long oldseek, long oldloc)
179 {
180 struct ddloc_mem *lp;
181
182 lp = LIST_FIRST(&dirp->dd_td->td_locq);
183 if (lp != NULL) {
184 if (lp->loc_loc == oldloc &&
185 lp->loc_seek == oldseek) {
186 lp->loc_seek = dirp->dd_seek;
187 lp->loc_loc = dirp->dd_loc;
188 }
189 }
190 }
191
192 /*
193 * Reclaim memory for telldir cookies which weren't used.
194 */
195 void
_reclaim_telldir(DIR * dirp)196 _reclaim_telldir(DIR *dirp)
197 {
198 struct ddloc_mem *lp;
199 struct ddloc_mem *templp;
200
201 lp = LIST_FIRST(&dirp->dd_td->td_locq);
202 while (lp != NULL) {
203 templp = lp;
204 lp = LIST_NEXT(lp, loc_lqe);
205 free(templp);
206 }
207 LIST_INIT(&dirp->dd_td->td_locq);
208 }
209