1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1983, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 #if defined(LIBC_SCCS) && !defined(lint) 33 static char sccsid[] = "@(#)telldir.c 8.1 (Berkeley) 6/4/93"; 34 #endif /* LIBC_SCCS and not lint */ 35 #include <sys/cdefs.h> 36 __FBSDID("$FreeBSD$"); 37 38 #include "namespace.h" 39 #include <sys/param.h> 40 #include <sys/queue.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 #include "gen-private.h" 49 #include "telldir.h" 50 51 /* 52 * return a pointer into a directory 53 */ 54 long 55 telldir(DIR *dirp) 56 { 57 struct ddloc_mem *lp, *flp; 58 union ddloc_packed ddloc; 59 60 if (__isthreaded) 61 _pthread_mutex_lock(&dirp->dd_lock); 62 /* 63 * Outline: 64 * 1) If the directory position fits in a packed structure, return that. 65 * 2) Otherwise, see if it's already been recorded in the linked list 66 * 3) Otherwise, malloc a new one 67 */ 68 if (dirp->dd_seek < (1ul << DD_SEEK_BITS) && 69 dirp->dd_loc < (1ul << DD_LOC_BITS)) { 70 ddloc.s.is_packed = 1; 71 ddloc.s.loc = dirp->dd_loc; 72 ddloc.s.seek = dirp->dd_seek; 73 goto out; 74 } 75 76 flp = NULL; 77 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) { 78 if (lp->loc_seek == dirp->dd_seek) { 79 if (flp == NULL) 80 flp = lp; 81 if (lp->loc_loc == dirp->dd_loc) 82 break; 83 } else if (flp != NULL) { 84 lp = NULL; 85 break; 86 } 87 } 88 if (lp == NULL) { 89 lp = malloc(sizeof(struct ddloc_mem)); 90 if (lp == NULL) { 91 if (__isthreaded) 92 _pthread_mutex_unlock(&dirp->dd_lock); 93 return (-1); 94 } 95 lp->loc_index = dirp->dd_td->td_loccnt++; 96 lp->loc_seek = dirp->dd_seek; 97 lp->loc_loc = dirp->dd_loc; 98 if (flp != NULL) 99 LIST_INSERT_BEFORE(flp, lp, loc_lqe); 100 else 101 LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe); 102 } 103 ddloc.i.is_packed = 0; 104 /* 105 * Technically this assignment could overflow on 32-bit architectures, 106 * but we would get ENOMEM long before that happens. 107 */ 108 ddloc.i.index = lp->loc_index; 109 110 out: 111 if (__isthreaded) 112 _pthread_mutex_unlock(&dirp->dd_lock); 113 return (ddloc.l); 114 } 115 116 /* 117 * seek to an entry in a directory. 118 * Only values returned by "telldir" should be passed to seekdir. 119 */ 120 void 121 _seekdir(DIR *dirp, long loc) 122 { 123 struct ddloc_mem *lp; 124 struct dirent *dp; 125 union ddloc_packed ddloc; 126 off_t loc_seek; 127 long loc_loc; 128 129 ddloc.l = loc; 130 131 if (ddloc.s.is_packed) { 132 loc_seek = ddloc.s.seek; 133 loc_loc = ddloc.s.loc; 134 } else { 135 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) { 136 if (lp->loc_index == ddloc.i.index) 137 break; 138 } 139 if (lp == NULL) 140 return; 141 142 loc_seek = lp->loc_seek; 143 loc_loc = lp->loc_loc; 144 } 145 if (loc_loc == dirp->dd_loc && loc_seek == dirp->dd_seek) 146 return; 147 148 /* If it's within the same chunk of data, don't bother reloading. */ 149 if (loc_seek == dirp->dd_seek) { 150 /* 151 * If we go back to 0 don't make the next readdir 152 * trigger a call to getdirentries(). 153 */ 154 if (loc_loc == 0) 155 dirp->dd_flags |= __DTF_SKIPREAD; 156 dirp->dd_loc = loc_loc; 157 return; 158 } 159 (void) lseek(dirp->dd_fd, (off_t)loc_seek, SEEK_SET); 160 dirp->dd_seek = loc_seek; 161 dirp->dd_loc = 0; 162 dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */ 163 while (dirp->dd_loc < loc_loc) { 164 dp = _readdir_unlocked(dirp, 0); 165 if (dp == NULL) 166 break; 167 } 168 } 169 170 /* 171 * After readdir returns the last entry in a block, a call to telldir 172 * returns a location that is after the end of that last entry. 173 * However, that location doesn't refer to a valid directory entry. 174 * Ideally, the call to telldir would return a location that refers to 175 * the first entry in the next block. That location is not known 176 * until the next block is read, so readdir calls this function after 177 * fetching a new block to fix any such telldir locations. 178 */ 179 void 180 _fixtelldir(DIR *dirp, long oldseek, long oldloc) 181 { 182 struct ddloc_mem *lp; 183 184 lp = LIST_FIRST(&dirp->dd_td->td_locq); 185 if (lp != NULL) { 186 if (lp->loc_loc == oldloc && 187 lp->loc_seek == oldseek) { 188 lp->loc_seek = dirp->dd_seek; 189 lp->loc_loc = dirp->dd_loc; 190 } 191 } 192 } 193 194 /* 195 * Reclaim memory for telldir cookies which weren't used. 196 */ 197 void 198 _reclaim_telldir(DIR *dirp) 199 { 200 struct ddloc_mem *lp; 201 struct ddloc_mem *templp; 202 203 lp = LIST_FIRST(&dirp->dd_td->td_locq); 204 while (lp != NULL) { 205 templp = lp; 206 lp = LIST_NEXT(lp, loc_lqe); 207 free(templp); 208 } 209 LIST_INIT(&dirp->dd_td->td_locq); 210 } 211