2 * SPDX-License-Identifier: BSD-3-Clause
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32 #include <sys/cdefs.h>
33 __SCCSID("@(#)telldir.c 8.1 (Berkeley) 6/4/93");
34 __FBSDID("$FreeBSD$");
36 #include "namespace.h"
37 #include <sys/param.h>
38 #include <sys/queue.h>
43 #include "un-namespace.h"
45 #include "libc_private.h"
46 #include "gen-private.h"
50 * return a pointer into a directory
55 struct ddloc_mem *lp, *flp;
56 union ddloc_packed ddloc;
59 _pthread_mutex_lock(&dirp->dd_lock);
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
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;
75 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
76 if (lp->loc_seek == dirp->dd_seek) {
79 if (lp->loc_loc == dirp->dd_loc)
81 } else if (flp != NULL) {
87 lp = malloc(sizeof(struct ddloc_mem));
90 _pthread_mutex_unlock(&dirp->dd_lock);
93 lp->loc_index = dirp->dd_td->td_loccnt++;
94 lp->loc_seek = dirp->dd_seek;
95 lp->loc_loc = dirp->dd_loc;
97 LIST_INSERT_BEFORE(flp, lp, loc_lqe);
99 LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
101 ddloc.i.is_packed = 0;
103 * Technically this assignment could overflow on 32-bit architectures,
104 * but we would get ENOMEM long before that happens.
106 ddloc.i.index = lp->loc_index;
110 _pthread_mutex_unlock(&dirp->dd_lock);
115 * seek to an entry in a directory.
116 * Only values returned by "telldir" should be passed to seekdir.
119 _seekdir(DIR *dirp, long loc)
121 struct ddloc_mem *lp;
123 union ddloc_packed ddloc;
129 if (ddloc.s.is_packed) {
130 loc_seek = ddloc.s.seek;
131 loc_loc = ddloc.s.loc;
133 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
134 if (lp->loc_index == ddloc.i.index)
140 loc_seek = lp->loc_seek;
141 loc_loc = lp->loc_loc;
143 if (loc_loc == dirp->dd_loc && loc_seek == dirp->dd_seek)
146 /* If it's within the same chunk of data, don't bother reloading. */
147 if (loc_seek == dirp->dd_seek) {
149 * If we go back to 0 don't make the next readdir
150 * trigger a call to getdirentries().
153 dirp->dd_flags |= __DTF_SKIPREAD;
154 dirp->dd_loc = loc_loc;
157 (void) lseek(dirp->dd_fd, (off_t)loc_seek, SEEK_SET);
158 dirp->dd_seek = loc_seek;
160 dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */
161 while (dirp->dd_loc < loc_loc) {
162 dp = _readdir_unlocked(dirp, 0);
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.
178 _fixtelldir(DIR *dirp, long oldseek, long oldloc)
180 struct ddloc_mem *lp;
182 lp = LIST_FIRST(&dirp->dd_td->td_locq);
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;
193 * Reclaim memory for telldir cookies which weren't used.
196 _reclaim_telldir(DIR *dirp)
198 struct ddloc_mem *lp;
199 struct ddloc_mem *templp;
201 lp = LIST_FIRST(&dirp->dd_td->td_locq);
204 lp = LIST_NEXT(lp, loc_lqe);
207 LIST_INIT(&dirp->dd_td->td_locq);