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 #include <sys/cdefs.h> 33 __SCCSID("@(#)telldir.c 8.1 (Berkeley) 6/4/93"); 34 __FBSDID("$FreeBSD$"); 35 36 #include "namespace.h" 37 #include <sys/param.h> 38 #include <sys/queue.h> 39 #include <dirent.h> 40 #include <pthread.h> 41 #include <stdlib.h> 42 #include <unistd.h> 43 #include "un-namespace.h" 44 45 #include "libc_private.h" 46 #include "gen-private.h" 47 #include "telldir.h" 48 49 /* 50 * return a pointer into a directory 51 */ 52 long 53 telldir(DIR *dirp) 54 { 55 struct ddloc_mem *lp, *flp; 56 union ddloc_packed ddloc; 57 58 if (__isthreaded) 59 _pthread_mutex_lock(&dirp->dd_lock); 60 /* 61 * Outline: 62 * 1) If the directory position fits in a packed structure, return that. 63 * 2) Otherwise, see if it's already been recorded in the linked list 64 * 3) Otherwise, malloc a new one 65 */ 66 if (dirp->dd_seek < (off_t)(1l << DD_SEEK_BITS) && 67 dirp->dd_loc < (1l << DD_LOC_BITS)) { 68 ddloc.s.is_packed = 1; 69 ddloc.s.loc = dirp->dd_loc; 70 ddloc.s.seek = dirp->dd_seek; 71 goto out; 72 } 73 74 flp = NULL; 75 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) { 76 if (lp->loc_seek == dirp->dd_seek) { 77 if (flp == NULL) 78 flp = lp; 79 if (lp->loc_loc == dirp->dd_loc) 80 break; 81 } else if (flp != NULL) { 82 lp = NULL; 83 break; 84 } 85 } 86 if (lp == NULL) { 87 lp = malloc(sizeof(struct ddloc_mem)); 88 if (lp == NULL) { 89 if (__isthreaded) 90 _pthread_mutex_unlock(&dirp->dd_lock); 91 return (-1); 92 } 93 lp->loc_index = dirp->dd_td->td_loccnt++; 94 lp->loc_seek = dirp->dd_seek; 95 lp->loc_loc = dirp->dd_loc; 96 if (flp != NULL) 97 LIST_INSERT_BEFORE(flp, lp, loc_lqe); 98 else 99 LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe); 100 } 101 ddloc.i.is_packed = 0; 102 /* 103 * Technically this assignment could overflow on 32-bit architectures, 104 * but we would get ENOMEM long before that happens. 105 */ 106 ddloc.i.index = lp->loc_index; 107 108 out: 109 if (__isthreaded) 110 _pthread_mutex_unlock(&dirp->dd_lock); 111 return (ddloc.l); 112 } 113 114 /* 115 * seek to an entry in a directory. 116 * Only values returned by "telldir" should be passed to seekdir. 117 */ 118 void 119 _seekdir(DIR *dirp, long loc) 120 { 121 struct ddloc_mem *lp; 122 struct dirent *dp; 123 union ddloc_packed ddloc; 124 off_t loc_seek; 125 long loc_loc; 126 127 ddloc.l = loc; 128 129 if (ddloc.s.is_packed) { 130 loc_seek = ddloc.s.seek; 131 loc_loc = ddloc.s.loc; 132 } else { 133 LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) { 134 if (lp->loc_index == ddloc.i.index) 135 break; 136 } 137 if (lp == NULL) 138 return; 139 140 loc_seek = lp->loc_seek; 141 loc_loc = lp->loc_loc; 142 } 143 if (loc_loc == dirp->dd_loc && loc_seek == dirp->dd_seek) 144 return; 145 146 /* If it's within the same chunk of data, don't bother reloading. */ 147 if (loc_seek == dirp->dd_seek) { 148 /* 149 * If we go back to 0 don't make the next readdir 150 * trigger a call to getdirentries(). 151 */ 152 if (loc_loc == 0) 153 dirp->dd_flags |= __DTF_SKIPREAD; 154 dirp->dd_loc = loc_loc; 155 return; 156 } 157 (void) lseek(dirp->dd_fd, (off_t)loc_seek, SEEK_SET); 158 dirp->dd_seek = loc_seek; 159 dirp->dd_loc = 0; 160 dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */ 161 while (dirp->dd_loc < loc_loc) { 162 dp = _readdir_unlocked(dirp, 0); 163 if (dp == NULL) 164 break; 165 } 166 } 167 168 /* 169 * After readdir returns the last entry in a block, a call to telldir 170 * returns a location that is after the end of that last entry. 171 * However, that location doesn't refer to a valid directory entry. 172 * Ideally, the call to telldir would return a location that refers to 173 * the first entry in the next block. That location is not known 174 * until the next block is read, so readdir calls this function after 175 * fetching a new block to fix any such telldir locations. 176 */ 177 void 178 _fixtelldir(DIR *dirp, long oldseek, long oldloc) 179 { 180 struct ddloc_mem *lp; 181 182 lp = LIST_FIRST(&dirp->dd_td->td_locq); 183 if (lp != NULL) { 184 if (lp->loc_loc == oldloc && 185 lp->loc_seek == oldseek) { 186 lp->loc_seek = dirp->dd_seek; 187 lp->loc_loc = dirp->dd_loc; 188 } 189 } 190 } 191 192 /* 193 * Reclaim memory for telldir cookies which weren't used. 194 */ 195 void 196 _reclaim_telldir(DIR *dirp) 197 { 198 struct ddloc_mem *lp; 199 struct ddloc_mem *templp; 200 201 lp = LIST_FIRST(&dirp->dd_td->td_locq); 202 while (lp != NULL) { 203 templp = lp; 204 lp = LIST_NEXT(lp, loc_lqe); 205 free(templp); 206 } 207 LIST_INIT(&dirp->dd_td->td_locq); 208 } 209