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 1.3 2005/01/31 22:29:15 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 * 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 * One of these structures is malloced to describe the current directory 58 * position each time telldir is called. It records the current magic 59 * cookie returned by getdirentries and the offset within the buffer 60 * associated with that return value. 61 */ 62 struct ddloc { 63 struct ddloc *loc_next;/* next structure in list */ 64 long loc_index; /* key associated with structure */ 65 long loc_seek; /* magic cookie returned by getdirentries */ 66 long loc_loc; /* offset of entry in buffer */ 67 const DIR* loc_dirp; /* directory which used this entry */ 68 }; 69 70 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 71 #define LOCHASH(i) ((i)&(NDIRHASH-1)) 72 73 static long dd_loccnt; /* Index of entry for sequential readdir's */ 74 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 75 76 /* 77 * return a pointer into a directory 78 */ 79 long 80 telldir(dirp) 81 const DIR *dirp; 82 { 83 int index; 84 struct ddloc *lp; 85 86 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 87 return (-1); 88 if (__isthreaded) 89 _pthread_mutex_lock((pthread_mutex_t *)&dirp->dd_lock); 90 index = dd_loccnt++; 91 lp->loc_index = index; 92 lp->loc_seek = dirp->dd_seek; 93 lp->loc_loc = dirp->dd_loc; 94 lp->loc_dirp = dirp; 95 lp->loc_next = dd_hash[LOCHASH(index)]; 96 dd_hash[LOCHASH(index)] = lp; 97 if (__isthreaded) 98 _pthread_mutex_unlock((pthread_mutex_t *)&dirp->dd_lock); 99 return (index); 100 } 101 102 /* 103 * seek to an entry in a directory. 104 * Only values returned by "telldir" should be passed to seekdir. 105 */ 106 void 107 _seekdir(dirp, loc) 108 DIR *dirp; 109 long loc; 110 { 111 struct ddloc *lp; 112 struct ddloc **prevlp; 113 struct dirent *dp; 114 115 prevlp = &dd_hash[LOCHASH(loc)]; 116 lp = *prevlp; 117 while (lp != NULL) { 118 if (lp->loc_index == loc) 119 break; 120 prevlp = &lp->loc_next; 121 lp = lp->loc_next; 122 } 123 if (lp == NULL) 124 return; 125 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 126 goto found; 127 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 128 dirp->dd_seek = lp->loc_seek; 129 dirp->dd_loc = 0; 130 while (dirp->dd_loc < lp->loc_loc) { 131 dp = _readdir_unlocked(dirp); 132 if (dp == NULL) 133 break; 134 } 135 found: 136 #ifdef SINGLEUSE 137 *prevlp = lp->loc_next; 138 free((caddr_t)lp); 139 #endif 140 } 141 142 /* 143 * Reclaim memory for telldir cookies which weren't used. 144 */ 145 void 146 _reclaim_telldir(dirp) 147 DIR *dirp; 148 { 149 struct ddloc *lp; 150 struct ddloc **prevlp; 151 int i; 152 153 for (i = 0; i < NDIRHASH; i++) { 154 prevlp = &dd_hash[i]; 155 lp = *prevlp; 156 while (lp != NULL) { 157 if (lp->loc_dirp == dirp) { 158 *prevlp = lp->loc_next; 159 free((caddr_t)lp); 160 lp = *prevlp; 161 continue; 162 } 163 prevlp = &lp->loc_next; 164 lp = lp->loc_next; 165 } 166 } 167 } 168