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 $ 34 * $DragonFly: src/lib/libc/gen/telldir.c,v 1.7 2008/05/03 22:07:37 dillon Exp $ 35 * 36 * @(#)telldir.c 8.1 (Berkeley) 6/4/93 37 */ 38 39 #include "namespace.h" 40 #include <sys/param.h> 41 #include <dirent.h> 42 #include <pthread.h> 43 #include <stdlib.h> 44 #include <unistd.h> 45 #include "un-namespace.h" 46 47 #include "libc_private.h" 48 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 */ 55 struct ddloc { 56 struct ddloc *loc_next;/* next structure in list */ 57 long loc_index; /* key associated with structure */ 58 off_t loc_seek; /* magic cookie returned by getdirentries */ 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 66 static long dd_loccnt; /* Index of entry for sequential readdir's */ 67 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 68 static pthread_mutex_t dd_hash_lock; 69 70 /* 71 * return a pointer into a directory 72 */ 73 long 74 telldir(const DIR *dirp) 75 { 76 long index; 77 struct ddloc *lp; 78 79 if (__isthreaded) { 80 _pthread_mutex_lock((pthread_mutex_t *)&dirp->dd_lock); 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 } 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; 105 106 lp->loc_next = dd_hash[LOCHASH(index)]; 107 dd_hash[LOCHASH(index)] = lp; 108 109 done: 110 if (__isthreaded) { 111 _pthread_mutex_unlock(&dd_hash_lock); 112 _pthread_mutex_unlock((pthread_mutex_t *)&dirp->dd_lock); 113 } 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 */ 121 void 122 _seekdir(DIR *dirp, long loc) 123 { 124 struct ddloc *lp; 125 struct ddloc **prevlp; 126 struct dirent *dp; 127 128 if (__isthreaded) 129 _pthread_mutex_lock(&dd_hash_lock); 130 for (lp = dd_hash[LOCHASH(loc)]; lp; lp = lp->loc_next) { 131 if (lp->loc_dirp == dirp && lp->loc_index == loc) 132 break; 133 } 134 if (__isthreaded) 135 _pthread_mutex_unlock(&dd_hash_lock); 136 if (lp == NULL) 137 return; 138 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 139 return; 140 lseek(dirp->dd_fd, lp->loc_seek, SEEK_SET); 141 dirp->dd_seek = lp->loc_seek; 142 dirp->dd_loc = 0; 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) { 151 dp = _readdir_unlocked(dirp, 0); 152 if (dp == NULL) 153 break; 154 } 155 } 156 157 /* 158 * Reclaim memory for telldir cookies which weren't used. 159 */ 160 void 161 _reclaim_telldir(DIR *dirp) 162 { 163 struct ddloc *lp; 164 struct ddloc **prevlp; 165 int i; 166 167 if (__isthreaded) 168 _pthread_mutex_lock(&dd_hash_lock); 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 } 183 if (__isthreaded) 184 _pthread_mutex_unlock(&dd_hash_lock); 185 } 186