telldir.c revision 235647 
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 235647 2012-05-19 12:44:27Z gleb $");
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 * The option SINGLEUSE may be defined to say that a telldir
51 * cookie may be used only once before it is freed. This option
52 * is used to avoid having memory usage grow without bound.
53 */
54#define SINGLEUSE
55
56/*
57 * return a pointer into a directory
58 */
59long
60telldir(dirp)
61	DIR *dirp;
62{
63	struct ddloc *lp;
64
65	if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
66		return (-1);
67	if (__isthreaded)
68		_pthread_mutex_lock(&dirp->dd_lock);
69	lp->loc_index = dirp->dd_td->td_loccnt++;
70	lp->loc_seek = dirp->dd_seek;
71	lp->loc_loc = dirp->dd_loc;
72	LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
73	if (__isthreaded)
74		_pthread_mutex_unlock(&dirp->dd_lock);
75	return (lp->loc_index);
76}
77
78/*
79 * seek to an entry in a directory.
80 * Only values returned by "telldir" should be passed to seekdir.
81 */
82void
83_seekdir(dirp, loc)
84	DIR *dirp;
85	long loc;
86{
87	struct ddloc *lp;
88	struct dirent *dp;
89
90	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
91		if (lp->loc_index == loc)
92			break;
93	}
94	if (lp == NULL)
95		return;
96	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
97		goto found;
98	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
99	dirp->dd_seek = lp->loc_seek;
100	dirp->dd_loc = 0;
101	while (dirp->dd_loc < lp->loc_loc) {
102		dp = _readdir_unlocked(dirp, 0);
103		if (dp == NULL)
104			break;
105	}
106found:
107#ifdef SINGLEUSE
108	LIST_REMOVE(lp, loc_lqe);
109	free((caddr_t)lp);
110#endif
111}
112
113/*
114 * Reclaim memory for telldir cookies which weren't used.
115 */
116void
117_reclaim_telldir(dirp)
118	DIR *dirp;
119{
120	struct ddloc *lp;
121	struct ddloc *templp;
122
123	lp = LIST_FIRST(&dirp->dd_td->td_locq);
124	while (lp != NULL) {
125		templp = lp;
126		lp = LIST_NEXT(lp, loc_lqe);
127		free(templp);
128	}
129	LIST_INIT(&dirp->dd_td->td_locq);
130}
131