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