telldir.c revision 165903 
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: head/lib/libc/gen/telldir.c 165903 2007-01-09 00:28:16Z imp $");
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 "telldir.h"
47
48/*
49 * The option SINGLEUSE may be defined to say that a telldir
50 * cookie may be used only once before it is freed. This option
51 * is used to avoid having memory usage grow without bound.
52 */
53#define SINGLEUSE
54
55/*
56 * return a pointer into a directory
57 */
58long
59telldir(dirp)
60	DIR *dirp;
61{
62	struct ddloc *lp;
63
64	if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
65		return (-1);
66	if (__isthreaded)
67		_pthread_mutex_lock((pthread_mutex_t *)&dirp->dd_lock);
68	lp->loc_index = dirp->dd_td->td_loccnt++;
69	lp->loc_seek = dirp->dd_seek;
70	lp->loc_loc = dirp->dd_loc;
71	LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
72	if (__isthreaded)
73		_pthread_mutex_unlock((pthread_mutex_t *)&dirp->dd_lock);
74	return (lp->loc_index);
75}
76
77/*
78 * seek to an entry in a directory.
79 * Only values returned by "telldir" should be passed to seekdir.
80 */
81void
82_seekdir(dirp, loc)
83	DIR *dirp;
84	long loc;
85{
86	struct ddloc *lp;
87	struct dirent *dp;
88
89	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
90		if (lp->loc_index == loc)
91			break;
92	}
93	if (lp == NULL)
94		return;
95	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
96		goto found;
97	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
98	dirp->dd_seek = lp->loc_seek;
99	dirp->dd_loc = 0;
100	while (dirp->dd_loc < lp->loc_loc) {
101		dp = _readdir_unlocked(dirp);
102		if (dp == NULL)
103			break;
104	}
105found:
106#ifdef SINGLEUSE
107	LIST_REMOVE(lp, loc_lqe);
108	free((caddr_t)lp);
109#endif
110}
111
112/*
113 * Reclaim memory for telldir cookies which weren't used.
114 */
115void
116_reclaim_telldir(dirp)
117	DIR *dirp;
118{
119	struct ddloc *lp;
120	struct ddloc *templp;
121
122	lp = LIST_FIRST(&dirp->dd_td->td_locq);
123	while (lp != NULL) {
124		templp = lp;
125		lp = LIST_NEXT(lp, loc_lqe);
126		free(templp);
127	}
128	LIST_INIT(&dirp->dd_td->td_locq);
129}
130