2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1983, 1993
5 * The Regents of the University of California. All rights reserved.
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8 * modification, are permitted provided that the following conditions
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12 * 2. Redistributions in binary form must reproduce the above copyright
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16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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32 #if defined(LIBC_SCCS) && !defined(lint)
33 static char sccsid[] = "@(#)telldir.c 8.1 (Berkeley) 6/4/93";
34 #endif /* LIBC_SCCS and not lint */
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
38 #include "namespace.h"
39 #include <sys/param.h>
40 #include <sys/queue.h>
45 #include "un-namespace.h"
47 #include "libc_private.h"
48 #include "gen-private.h"
52 * return a pointer into a directory
57 struct ddloc_mem *lp, *flp;
58 union ddloc_packed ddloc;
61 _pthread_mutex_lock(&dirp->dd_lock);
64 * 1) If the directory position fits in a packed structure, return that.
65 * 2) Otherwise, see if it's already been recorded in the linked list
66 * 3) Otherwise, malloc a new one
68 if (dirp->dd_seek < (1ul << DD_SEEK_BITS) &&
69 dirp->dd_loc < (1ul << DD_LOC_BITS)) {
70 ddloc.s.is_packed = 1;
71 ddloc.s.loc = dirp->dd_loc;
72 ddloc.s.seek = dirp->dd_seek;
77 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
78 if (lp->loc_seek == dirp->dd_seek) {
81 if (lp->loc_loc == dirp->dd_loc)
83 } else if (flp != NULL) {
89 lp = malloc(sizeof(struct ddloc_mem));
92 _pthread_mutex_unlock(&dirp->dd_lock);
95 lp->loc_index = dirp->dd_td->td_loccnt++;
96 lp->loc_seek = dirp->dd_seek;
97 lp->loc_loc = dirp->dd_loc;
99 LIST_INSERT_BEFORE(flp, lp, loc_lqe);
101 LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
103 ddloc.i.is_packed = 0;
105 * Technically this assignment could overflow on 32-bit architectures,
106 * but we would get ENOMEM long before that happens.
108 ddloc.i.index = lp->loc_index;
112 _pthread_mutex_unlock(&dirp->dd_lock);
117 * seek to an entry in a directory.
118 * Only values returned by "telldir" should be passed to seekdir.
121 _seekdir(DIR *dirp, long loc)
123 struct ddloc_mem *lp;
125 union ddloc_packed ddloc;
131 if (ddloc.s.is_packed) {
132 loc_seek = ddloc.s.seek;
133 loc_loc = ddloc.s.loc;
135 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
136 if (lp->loc_index == ddloc.i.index)
142 loc_seek = lp->loc_seek;
143 loc_loc = lp->loc_loc;
145 if (loc_loc == dirp->dd_loc && loc_seek == dirp->dd_seek)
148 /* If it's within the same chunk of data, don't bother reloading. */
149 if (loc_seek == dirp->dd_seek) {
151 * If we go back to 0 don't make the next readdir
152 * trigger a call to getdirentries().
155 dirp->dd_flags |= __DTF_SKIPREAD;
156 dirp->dd_loc = loc_loc;
159 (void) lseek(dirp->dd_fd, (off_t)loc_seek, SEEK_SET);
160 dirp->dd_seek = loc_seek;
162 dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */
163 while (dirp->dd_loc < loc_loc) {
164 dp = _readdir_unlocked(dirp, 0);
171 * After readdir returns the last entry in a block, a call to telldir
172 * returns a location that is after the end of that last entry.
173 * However, that location doesn't refer to a valid directory entry.
174 * Ideally, the call to telldir would return a location that refers to
175 * the first entry in the next block. That location is not known
176 * until the next block is read, so readdir calls this function after
177 * fetching a new block to fix any such telldir locations.
180 _fixtelldir(DIR *dirp, long oldseek, long oldloc)
182 struct ddloc_mem *lp;
184 lp = LIST_FIRST(&dirp->dd_td->td_locq);
186 if (lp->loc_loc == oldloc &&
187 lp->loc_seek == oldseek) {
188 lp->loc_seek = dirp->dd_seek;
189 lp->loc_loc = dirp->dd_loc;
195 * Reclaim memory for telldir cookies which weren't used.
198 _reclaim_telldir(DIR *dirp)
200 struct ddloc_mem *lp;
201 struct ddloc_mem *templp;
203 lp = LIST_FIRST(&dirp->dd_td->td_locq);
206 lp = LIST_NEXT(lp, loc_lqe);
209 LIST_INIT(&dirp->dd_td->td_locq);