1 /* $NetBSD: telldir.c,v 1.17 2006/01/24 19:33:10 christos Exp $ */ 2 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 #if defined(LIBC_SCCS) && !defined(lint) 34 #if 0 35 static char sccsid[] = "@(#)telldir.c 8.1 (Berkeley) 6/4/93"; 36 #else 37 __RCSID("$NetBSD: telldir.c,v 1.17 2006/01/24 19:33:10 christos Exp $"); 38 #endif 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include "namespace.h" 42 #include "reentrant.h" 43 #include "extern.h" 44 #include <sys/param.h> 45 46 #include <assert.h> 47 #include <dirent.h> 48 #include <stdlib.h> 49 #include <unistd.h> 50 51 #ifdef __weak_alias 52 __weak_alias(telldir,_telldir) 53 #endif 54 55 /* 56 * The option SINGLEUSE may be defined to say that a telldir 57 * cookie may be used only once before it is freed. This option 58 * is used to avoid having memory usage grow without bound. 59 */ 60 #define SINGLEUSE 61 62 /* 63 * One of these structures is malloced to describe the current directory 64 * position each time telldir is called. It records the current magic 65 * cookie returned by getdirentries and the offset within the buffer 66 * associated with that return value. 67 */ 68 struct ddloc { 69 struct ddloc *loc_next;/* next structure in list */ 70 long loc_index; /* key associated with structure */ 71 off_t loc_seek; /* magic cookie returned by getdirentries */ 72 long loc_loc; /* offset of entry in buffer */ 73 }; 74 75 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 76 #define LOCHASH(i) (((int)i)&(NDIRHASH-1)) 77 78 static long dd_loccnt; /* Index of entry for sequential readdir's */ 79 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 80 81 long 82 telldir(const DIR *dirp) 83 { 84 long rv; 85 #ifdef _REENTRANT 86 if (__isthreaded) { 87 mutex_lock((mutex_t *)dirp->dd_lock); 88 rv = _telldir_unlocked(dirp); 89 mutex_unlock((mutex_t *)dirp->dd_lock); 90 } else 91 #endif 92 rv = _telldir_unlocked(dirp); 93 return rv; 94 } 95 96 /* 97 * return a pointer into a directory 98 */ 99 long 100 _telldir_unlocked(const DIR *dirp) 101 { 102 long idx; 103 struct ddloc *lp; 104 105 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 106 return (-1); 107 idx = dd_loccnt++; 108 lp->loc_index = idx; 109 lp->loc_seek = dirp->dd_seek; 110 lp->loc_loc = dirp->dd_loc; 111 lp->loc_next = dd_hash[LOCHASH(idx)]; 112 dd_hash[LOCHASH(idx)] = lp; 113 return (idx); 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_unlocked(DIR *dirp, long loc) 122 { 123 struct ddloc *lp; 124 struct ddloc **prevlp; 125 struct dirent *dp; 126 127 _DIAGASSERT(dirp != NULL); 128 129 prevlp = &dd_hash[LOCHASH(loc)]; 130 lp = *prevlp; 131 while (lp != NULL) { 132 if (lp->loc_index == loc) 133 break; 134 prevlp = &lp->loc_next; 135 lp = lp->loc_next; 136 } 137 if (lp == NULL) 138 return; 139 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 140 goto found; 141 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 142 dirp->dd_seek = lp->loc_seek; 143 dirp->dd_loc = 0; 144 while (dirp->dd_loc < lp->loc_loc) { 145 dp = _readdir_unlocked(dirp); 146 if (dp == NULL) 147 break; 148 } 149 found: 150 #ifdef SINGLEUSE 151 *prevlp = lp->loc_next; 152 free(lp); 153 #endif 154 } 155