1 /* $NetBSD: telldir.c,v 1.15 2003/08/07 16:42:58 agc 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 1.15 2003/08/07 16:42:58 agc Exp $"); 38 #endif 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include "namespace.h" 42 #include "reentrant.h" 43 #include <sys/param.h> 44 45 #include <assert.h> 46 #include <dirent.h> 47 #include <stdlib.h> 48 #include <unistd.h> 49 50 #ifdef __weak_alias 51 __weak_alias(telldir,_telldir) 52 #endif 53 54 /* 55 * The option SINGLEUSE may be defined to say that a telldir 56 * cookie may be used only once before it is freed. This option 57 * is used to avoid having memory usage grow without bound. 58 */ 59 #define SINGLEUSE 60 61 /* 62 * One of these structures is malloced to describe the current directory 63 * position each time telldir is called. It records the current magic 64 * cookie returned by getdirentries and the offset within the buffer 65 * associated with that return value. 66 */ 67 struct ddloc { 68 struct ddloc *loc_next;/* next structure in list */ 69 long loc_index; /* key associated with structure */ 70 off_t loc_seek; /* magic cookie returned by getdirentries */ 71 long loc_loc; /* offset of entry in buffer */ 72 }; 73 74 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 75 #define LOCHASH(i) (((int)i)&(NDIRHASH-1)) 76 77 static long dd_loccnt; /* Index of entry for sequential readdir's */ 78 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 79 80 /* 81 * return a pointer into a directory 82 */ 83 long 84 telldir(dirp) 85 const DIR *dirp; 86 { 87 long idx; 88 struct ddloc *lp; 89 90 #ifdef _REENTRANT 91 if (__isthreaded) 92 mutex_lock((mutex_t *)dirp->dd_lock); 93 #endif 94 95 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 96 return (-1); 97 idx = dd_loccnt++; 98 lp->loc_index = idx; 99 lp->loc_seek = dirp->dd_seek; 100 lp->loc_loc = dirp->dd_loc; 101 lp->loc_next = dd_hash[LOCHASH(idx)]; 102 dd_hash[LOCHASH(idx)] = lp; 103 #ifdef _REENTRANT 104 if (__isthreaded) 105 mutex_unlock((mutex_t *)dirp->dd_lock); 106 #endif 107 return (idx); 108 } 109 110 /* 111 * seek to an entry in a directory. 112 * Only values returned by "telldir" should be passed to seekdir. 113 */ 114 void 115 __seekdir(dirp, loc) 116 DIR *dirp; 117 long loc; 118 { 119 struct ddloc *lp; 120 struct ddloc **prevlp; 121 struct dirent *dp; 122 123 _DIAGASSERT(dirp != NULL); 124 125 prevlp = &dd_hash[LOCHASH(loc)]; 126 lp = *prevlp; 127 while (lp != NULL) { 128 if (lp->loc_index == loc) 129 break; 130 prevlp = &lp->loc_next; 131 lp = lp->loc_next; 132 } 133 if (lp == NULL) 134 return; 135 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 136 goto found; 137 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 138 dirp->dd_seek = lp->loc_seek; 139 dirp->dd_loc = 0; 140 while (dirp->dd_loc < lp->loc_loc) { 141 dp = readdir(dirp); 142 if (dp == NULL) 143 break; 144 } 145 found: 146 #ifdef SINGLEUSE 147 *prevlp = lp->loc_next; 148 free(lp); 149 #endif 150 } 151