* Remove the SINGLEUSE feature for telldir(), it does not conform to the
[dragonfly.git] / lib / libc / gen / telldir.c
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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: src/lib/libc/gen/telldir.c,v 1.4.12.1 2001/03/05 09:39:59 obrien Exp $
9d7ae7ac 34 * $DragonFly: src/lib/libc/gen/telldir.c,v 1.6 2008/04/22 21:29:42 dillon Exp $
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35 *
36 * @(#)telldir.c 8.1 (Berkeley) 6/4/93
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37 */
38
17ea2221 39#include "namespace.h"
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40#include <sys/param.h>
41#include <dirent.h>
17ea2221 42#include <pthread.h>
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43#include <stdlib.h>
44#include <unistd.h>
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45#include "un-namespace.h"
46
47#include "libc_private.h"
984263bc 48
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49/*
50 * One of these structures is malloced to describe the current directory
51 * position each time telldir is called. It records the current magic
52 * cookie returned by getdirentries and the offset within the buffer
53 * associated with that return value.
54 */
55struct ddloc {
56 struct ddloc *loc_next;/* next structure in list */
57 long loc_index; /* key associated with structure */
eac3020c 58 off_t loc_seek; /* magic cookie returned by getdirentries */
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59 long loc_loc; /* offset of entry in buffer */
60 const DIR* loc_dirp; /* directory which used this entry */
61};
62
63#define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */
64#define LOCHASH(i) ((i)&(NDIRHASH-1))
65
66static long dd_loccnt; /* Index of entry for sequential readdir's */
67static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */
9d7ae7ac 68static pthread_mutex_t dd_hash_lock;
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69
70/*
71 * return a pointer into a directory
72 */
73long
0f52d283 74telldir(const DIR *dirp)
984263bc 75{
9d7ae7ac 76 long index;
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77 struct ddloc *lp;
78
9d7ae7ac 79 if (__isthreaded) {
17ea2221 80 _pthread_mutex_lock((pthread_mutex_t *)&dirp->dd_lock);
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81 _pthread_mutex_lock(&dd_hash_lock);
82 }
83
84 /*
85 * Reduce memory use by reusing a ddloc that might already exist
86 * for this position.
87 */
88 for (lp = dd_hash[LOCHASH(dirp->dd_lastseek)]; lp; lp = lp->loc_next) {
89 if (lp->loc_dirp == dirp && lp->loc_seek == dirp->dd_seek &&
90 lp->loc_loc == dirp->dd_loc) {
91 index = lp->loc_index;
92 goto done;
93 }
94 }
95
96 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) {
97 index = -1;
98 goto done;
99 }
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100 index = dd_loccnt++;
101 lp->loc_index = index;
102 lp->loc_seek = dirp->dd_seek;
103 lp->loc_loc = dirp->dd_loc;
104 lp->loc_dirp = dirp;
9d7ae7ac 105
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106 lp->loc_next = dd_hash[LOCHASH(index)];
107 dd_hash[LOCHASH(index)] = lp;
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108
109done:
110 if (__isthreaded) {
111 _pthread_mutex_unlock(&dd_hash_lock);
17ea2221 112 _pthread_mutex_unlock((pthread_mutex_t *)&dirp->dd_lock);
9d7ae7ac 113 }
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114 return (index);
115}
116
117/*
118 * seek to an entry in a directory.
119 * Only values returned by "telldir" should be passed to seekdir.
120 */
121void
0f52d283 122_seekdir(DIR *dirp, long loc)
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123{
124 struct ddloc *lp;
125 struct ddloc **prevlp;
126 struct dirent *dp;
127
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128 if (__isthreaded)
129 _pthread_mutex_lock(&dd_hash_lock);
130 for (lp = dd_hash[LOCHASH(loc)]; lp; lp = lp->loc_next) {
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131 if (lp->loc_index == loc)
132 break;
984263bc 133 }
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134 if (__isthreaded)
135 _pthread_mutex_unlock(&dd_hash_lock);
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136 if (lp == NULL)
137 return;
138 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
9d7ae7ac 139 return;
eac3020c 140 lseek(dirp->dd_fd, lp->loc_seek, SEEK_SET);
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141 dirp->dd_seek = lp->loc_seek;
142 dirp->dd_loc = 0;
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143 dirp->dd_lastseek = loc;
144
145 /*
146 * Scan the buffer until we find dd_loc. If the directory
147 * changed between the tell and seek it is possible to
148 * load a new buffer or for dd_loc to not match directly.
149 */
150 while (dirp->dd_loc < lp->loc_loc && dirp->dd_seek == lp->loc_seek) {
17ea2221 151 dp = _readdir_unlocked(dirp);
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152 if (dp == NULL)
153 break;
154 }
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155}
156
157/*
158 * Reclaim memory for telldir cookies which weren't used.
159 */
160void
0f52d283 161_reclaim_telldir(DIR *dirp)
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162{
163 struct ddloc *lp;
164 struct ddloc **prevlp;
165 int i;
166
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167 if (__isthreaded)
168 _pthread_mutex_lock(&dd_hash_lock);
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169 for (i = 0; i < NDIRHASH; i++) {
170 prevlp = &dd_hash[i];
171 lp = *prevlp;
172 while (lp != NULL) {
173 if (lp->loc_dirp == dirp) {
174 *prevlp = lp->loc_next;
175 free((caddr_t)lp);
176 lp = *prevlp;
177 continue;
178 }
179 prevlp = &lp->loc_next;
180 lp = lp->loc_next;
181 }
182 }
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183 if (__isthreaded)
184 _pthread_mutex_unlock(&dd_hash_lock);
984263bc 185}