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