telldir.c revision 71579 
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 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * $FreeBSD: head/lib/libc/gen/telldir.c 71579 2001-01-24 13:01:12Z deischen $
34 */
35
36#if defined(LIBC_SCCS) && !defined(lint)
37static char sccsid[] = "@(#)telldir.c	8.1 (Berkeley) 6/4/93";
38#endif /* LIBC_SCCS and not lint */
39
40#include "namespace.h"
41#include <sys/param.h>
42#include <sys/queue.h>
43#include <dirent.h>
44#include <pthread.h>
45#include <stdlib.h>
46#include <unistd.h>
47#include "un-namespace.h"
48
49#include "libc_private.h"
50#include "telldir.h"
51
52/*
53 * The option SINGLEUSE may be defined to say that a telldir
54 * cookie may be used only once before it is freed. This option
55 * is used to avoid having memory usage grow without bound.
56 */
57#define SINGLEUSE
58
59/*
60 * return a pointer into a directory
61 */
62long
63telldir(dirp)
64	DIR *dirp;
65{
66	struct ddloc *lp;
67
68	if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
69		return (-1);
70	if (__isthreaded)
71		_pthread_mutex_lock((pthread_mutex_t *)&dirp->dd_lock);
72	lp->loc_index = dirp->dd_td->td_loccnt++;
73	lp->loc_seek = dirp->dd_seek;
74	lp->loc_loc = dirp->dd_loc;
75	LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
76	if (__isthreaded)
77		_pthread_mutex_unlock((pthread_mutex_t *)&dirp->dd_lock);
78	return (lp->loc_index);
79}
80
81/*
82 * seek to an entry in a directory.
83 * Only values returned by "telldir" should be passed to seekdir.
84 */
85void
86_seekdir(dirp, loc)
87	DIR *dirp;
88	long loc;
89{
90	struct ddloc *lp;
91	struct dirent *dp;
92
93	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
94		if (lp->loc_index == loc)
95			break;
96	}
97	if (lp == NULL)
98		return;
99	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
100		goto found;
101	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
102	dirp->dd_seek = lp->loc_seek;
103	dirp->dd_loc = 0;
104	while (dirp->dd_loc < lp->loc_loc) {
105		dp = _readdir_unlocked(dirp);
106		if (dp == NULL)
107			break;
108	}
109found:
110#ifdef SINGLEUSE
111	LIST_REMOVE(lp, loc_lqe);
112	free((caddr_t)lp);
113#endif
114}
115
116/*
117 * Reclaim memory for telldir cookies which weren't used.
118 */
119void
120_reclaim_telldir(dirp)
121	DIR *dirp;
122{
123	struct ddloc *lp;
124	struct ddloc *templp;
125
126	lp = LIST_FIRST(&dirp->dd_td->td_locq);
127	while (lp != NULL) {
128		templp = lp;
129		lp = LIST_NEXT(lp, loc_lqe);
130		free(templp);
131	}
132	LIST_INIT(&dirp->dd_td->td_locq);
133}
134