1 /* $NetBSD: telldir.c,v 1.6 1997/07/21 14:07:38 jtc 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. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #include <sys/cdefs.h> 37 #if defined(LIBC_SCCS) && !defined(lint) 38 #if 0 39 static char sccsid[] = "@(#)telldir.c 8.1 (Berkeley) 6/4/93"; 40 #else 41 __RCSID("$NetBSD: telldir.c,v 1.6 1997/07/21 14:07:38 jtc Exp $"); 42 #endif 43 #endif /* LIBC_SCCS and not lint */ 44 45 #include "namespace.h" 46 #include <sys/param.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 long 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) ((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 /* 82 * return a pointer into a directory 83 */ 84 long 85 telldir(dirp) 86 const DIR *dirp; 87 { 88 register int index; 89 register struct ddloc *lp; 90 91 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 92 return (-1); 93 index = dd_loccnt++; 94 lp->loc_index = index; 95 lp->loc_seek = dirp->dd_seek; 96 lp->loc_loc = dirp->dd_loc; 97 lp->loc_next = dd_hash[LOCHASH(index)]; 98 dd_hash[LOCHASH(index)] = lp; 99 return (index); 100 } 101 102 /* 103 * seek to an entry in a directory. 104 * Only values returned by "telldir" should be passed to seekdir. 105 */ 106 void 107 __seekdir(dirp, loc) 108 register DIR *dirp; 109 long loc; 110 { 111 register struct ddloc *lp; 112 register struct ddloc **prevlp; 113 struct dirent *dp; 114 115 prevlp = &dd_hash[LOCHASH(loc)]; 116 lp = *prevlp; 117 while (lp != NULL) { 118 if (lp->loc_index == loc) 119 break; 120 prevlp = &lp->loc_next; 121 lp = lp->loc_next; 122 } 123 if (lp == NULL) 124 return; 125 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 126 goto found; 127 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 128 dirp->dd_seek = lp->loc_seek; 129 dirp->dd_loc = 0; 130 while (dirp->dd_loc < lp->loc_loc) { 131 dp = readdir(dirp); 132 if (dp == NULL) 133 break; 134 } 135 found: 136 #ifdef SINGLEUSE 137 *prevlp = lp->loc_next; 138 free((caddr_t)lp); 139 #endif 140 } 141