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 1.4 2005/11/13 00:07:42 swildner 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(const DIR *dirp) 81 { 82 int index; 83 struct ddloc *lp; 84 85 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 86 return (-1); 87 if (__isthreaded) 88 _pthread_mutex_lock((pthread_mutex_t *)&dirp->dd_lock); 89 index = dd_loccnt++; 90 lp->loc_index = index; 91 lp->loc_seek = dirp->dd_seek; 92 lp->loc_loc = dirp->dd_loc; 93 lp->loc_dirp = dirp; 94 lp->loc_next = dd_hash[LOCHASH(index)]; 95 dd_hash[LOCHASH(index)] = lp; 96 if (__isthreaded) 97 _pthread_mutex_unlock((pthread_mutex_t *)&dirp->dd_lock); 98 return (index); 99 } 100 101 /* 102 * seek to an entry in a directory. 103 * Only values returned by "telldir" should be passed to seekdir. 104 */ 105 void 106 _seekdir(DIR *dirp, long loc) 107 { 108 struct ddloc *lp; 109 struct ddloc **prevlp; 110 struct dirent *dp; 111 112 prevlp = &dd_hash[LOCHASH(loc)]; 113 lp = *prevlp; 114 while (lp != NULL) { 115 if (lp->loc_index == loc) 116 break; 117 prevlp = &lp->loc_next; 118 lp = lp->loc_next; 119 } 120 if (lp == NULL) 121 return; 122 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 123 goto found; 124 lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 125 dirp->dd_seek = lp->loc_seek; 126 dirp->dd_loc = 0; 127 while (dirp->dd_loc < lp->loc_loc) { 128 dp = _readdir_unlocked(dirp); 129 if (dp == NULL) 130 break; 131 } 132 found: 133 #ifdef SINGLEUSE 134 *prevlp = lp->loc_next; 135 free((caddr_t)lp); 136 #endif 137 } 138 139 /* 140 * Reclaim memory for telldir cookies which weren't used. 141 */ 142 void 143 _reclaim_telldir(DIR *dirp) 144 { 145 struct ddloc *lp; 146 struct ddloc **prevlp; 147 int i; 148 149 for (i = 0; i < NDIRHASH; i++) { 150 prevlp = &dd_hash[i]; 151 lp = *prevlp; 152 while (lp != NULL) { 153 if (lp->loc_dirp == dirp) { 154 *prevlp = lp->loc_next; 155 free((caddr_t)lp); 156 lp = *prevlp; 157 continue; 158 } 159 prevlp = &lp->loc_next; 160 lp = lp->loc_next; 161 } 162 } 163 } 164