2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1983, 1993
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32 #include <sys/cdefs.h>
33 __SCCSID("@(#)telldir.c 8.1 (Berkeley) 6/4/93");
34 #include "namespace.h"
35 #include <sys/param.h>
36 #include <sys/queue.h>
41 #include "un-namespace.h"
43 #include "libc_private.h"
44 #include "gen-private.h"
48 * return a pointer into a directory
53 struct ddloc_mem *lp, *flp;
54 union ddloc_packed ddloc;
57 _pthread_mutex_lock(&dirp->dd_lock);
60 * 1) If the directory position fits in a packed structure, return that.
61 * 2) Otherwise, see if it's already been recorded in the linked list
62 * 3) Otherwise, malloc a new one
64 if (dirp->dd_seek < (off_t)(1l << DD_SEEK_BITS) &&
65 dirp->dd_loc < (1l << DD_LOC_BITS)) {
66 ddloc.s.is_packed = 1;
67 ddloc.s.loc = dirp->dd_loc;
68 ddloc.s.seek = dirp->dd_seek;
73 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
74 if (lp->loc_seek == dirp->dd_seek) {
77 if (lp->loc_loc == dirp->dd_loc)
79 } else if (flp != NULL) {
85 lp = malloc(sizeof(struct ddloc_mem));
88 _pthread_mutex_unlock(&dirp->dd_lock);
91 lp->loc_index = dirp->dd_td->td_loccnt++;
92 lp->loc_seek = dirp->dd_seek;
93 lp->loc_loc = dirp->dd_loc;
95 LIST_INSERT_BEFORE(flp, lp, loc_lqe);
97 LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
99 ddloc.i.is_packed = 0;
101 * Technically this assignment could overflow on 32-bit architectures,
102 * but we would get ENOMEM long before that happens.
104 ddloc.i.index = lp->loc_index;
108 _pthread_mutex_unlock(&dirp->dd_lock);
113 * seek to an entry in a directory.
114 * Only values returned by "telldir" should be passed to seekdir.
117 _seekdir(DIR *dirp, long loc)
119 struct ddloc_mem *lp;
121 union ddloc_packed ddloc;
127 if (ddloc.s.is_packed) {
128 loc_seek = ddloc.s.seek;
129 loc_loc = ddloc.s.loc;
131 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
132 if (lp->loc_index == ddloc.i.index)
138 loc_seek = lp->loc_seek;
139 loc_loc = lp->loc_loc;
141 if (loc_loc == dirp->dd_loc && loc_seek == dirp->dd_seek)
144 /* If it's within the same chunk of data, don't bother reloading. */
145 if (loc_seek == dirp->dd_seek) {
147 * If we go back to 0 don't make the next readdir
148 * trigger a call to getdirentries().
151 dirp->dd_flags |= __DTF_SKIPREAD;
152 dirp->dd_loc = loc_loc;
155 (void) lseek(dirp->dd_fd, (off_t)loc_seek, SEEK_SET);
156 dirp->dd_seek = loc_seek;
158 dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */
159 while (dirp->dd_loc < loc_loc) {
160 dp = _readdir_unlocked(dirp, 0);
167 * After readdir returns the last entry in a block, a call to telldir
168 * returns a location that is after the end of that last entry.
169 * However, that location doesn't refer to a valid directory entry.
170 * Ideally, the call to telldir would return a location that refers to
171 * the first entry in the next block. That location is not known
172 * until the next block is read, so readdir calls this function after
173 * fetching a new block to fix any such telldir locations.
176 _fixtelldir(DIR *dirp, long oldseek, long oldloc)
178 struct ddloc_mem *lp;
180 lp = LIST_FIRST(&dirp->dd_td->td_locq);
182 if (lp->loc_loc == oldloc &&
183 lp->loc_seek == oldseek) {
184 lp->loc_seek = dirp->dd_seek;
185 lp->loc_loc = dirp->dd_loc;
191 * Reclaim memory for telldir cookies which weren't used.
194 _reclaim_telldir(DIR *dirp)
196 struct ddloc_mem *lp;
197 struct ddloc_mem *templp;
199 lp = LIST_FIRST(&dirp->dd_td->td_locq);
202 lp = LIST_NEXT(lp, loc_lqe);
205 LIST_INIT(&dirp->dd_td->td_locq);