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)
31static 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: stable/10/lib/libc/gen/telldir.c 317634 2017-05-01 06:03:44Z mav $");
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 */
52long
53telldir(dirp)
54	DIR *dirp;
55{
56	struct ddloc *lp, *flp;
57	long idx;
58
59	if (__isthreaded)
60		_pthread_mutex_lock(&dirp->dd_lock);
61	flp = NULL;
62	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
63		if (lp->loc_seek == dirp->dd_seek) {
64			if (flp == NULL)
65				flp = lp;
66			if (lp->loc_loc == dirp->dd_loc)
67				break;
68		} else if (flp != NULL) {
69			lp = NULL;
70			break;
71		}
72	}
73	if (lp == NULL) {
74		lp = malloc(sizeof(struct ddloc));
75		if (lp == NULL) {
76			if (__isthreaded)
77				_pthread_mutex_unlock(&dirp->dd_lock);
78			return (-1);
79		}
80		lp->loc_index = dirp->dd_td->td_loccnt++;
81		lp->loc_seek = dirp->dd_seek;
82		lp->loc_loc = dirp->dd_loc;
83		if (flp != NULL)
84			LIST_INSERT_BEFORE(flp, lp, loc_lqe);
85		else
86			LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
87	}
88	idx = lp->loc_index;
89	if (__isthreaded)
90		_pthread_mutex_unlock(&dirp->dd_lock);
91	return (idx);
92}
93
94/*
95 * seek to an entry in a directory.
96 * Only values returned by "telldir" should be passed to seekdir.
97 */
98void
99_seekdir(dirp, loc)
100	DIR *dirp;
101	long loc;
102{
103	struct ddloc *lp;
104	struct dirent *dp;
105
106	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
107		if (lp->loc_index == loc)
108			break;
109	}
110	if (lp == NULL)
111		return;
112	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
113		return;
114
115	/* If it's within the same chunk of data, don't bother reloading. */
116	if (lp->loc_seek == dirp->dd_seek) {
117		/*
118		 * If we go back to 0 don't make the next readdir
119		 * trigger a call to getdirentries().
120		 */
121		if (lp->loc_loc == 0)
122			dirp->dd_flags |= __DTF_SKIPREAD;
123		dirp->dd_loc = lp->loc_loc;
124		return;
125	}
126	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
127	dirp->dd_seek = lp->loc_seek;
128	dirp->dd_loc = 0;
129	dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */
130	while (dirp->dd_loc < lp->loc_loc) {
131		dp = _readdir_unlocked(dirp, 0);
132		if (dp == NULL)
133			break;
134	}
135}
136
137/*
138 * After readdir returns the last entry in a block, a call to telldir
139 * returns a location that is after the end of that last entry.
140 * However, that location doesn't refer to a valid directory entry.
141 * Ideally, the call to telldir would return a location that refers to
142 * the first entry in the next block.  That location is not known
143 * until the next block is read, so readdir calls this function after
144 * fetching a new block to fix any such telldir locations.
145 */
146void
147_fixtelldir(DIR *dirp, long oldseek, long oldloc)
148{
149	struct ddloc *lp;
150
151	lp = LIST_FIRST(&dirp->dd_td->td_locq);
152	if (lp != NULL) {
153		if (lp->loc_loc == oldloc &&
154		    lp->loc_seek == oldseek) {
155			lp->loc_seek = dirp->dd_seek;
156			lp->loc_loc = dirp->dd_loc;
157		}
158	}
159}
160
161/*
162 * Reclaim memory for telldir cookies which weren't used.
163 */
164void
165_reclaim_telldir(dirp)
166	DIR *dirp;
167{
168	struct ddloc *lp;
169	struct ddloc *templp;
170
171	lp = LIST_FIRST(&dirp->dd_td->td_locq);
172	while (lp != NULL) {
173		templp = lp;
174		lp = LIST_NEXT(lp, loc_lqe);
175		free(templp);
176	}
177	LIST_INIT(&dirp->dd_td->td_locq);
178}
179