1 /* $NetBSD: telldir.c,v 1.13 2001/12/30 19:27:42 thorpej 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 1.13 2001/12/30 19:27:42 thorpej Exp $"); 42 #endif 43 #endif /* LIBC_SCCS and not lint */ 44 45 #include "namespace.h" 46 #include <sys/param.h> 47 48 #include <assert.h> 49 #include <dirent.h> 50 #include <stdlib.h> 51 #include <unistd.h> 52 53 #ifdef __weak_alias 54 __weak_alias(telldir,_telldir) 55 #endif 56 57 /* 58 * The option SINGLEUSE may be defined to say that a telldir 59 * cookie may be used only once before it is freed. This option 60 * is used to avoid having memory usage grow without bound. 61 */ 62 #define SINGLEUSE 63 64 /* 65 * One of these structures is malloced to describe the current directory 66 * position each time telldir is called. It records the current magic 67 * cookie returned by getdirentries and the offset within the buffer 68 * associated with that return value. 69 */ 70 struct ddloc { 71 struct ddloc *loc_next;/* next structure in list */ 72 long loc_index; /* key associated with structure */ 73 off_t loc_seek; /* magic cookie returned by getdirentries */ 74 long loc_loc; /* offset of entry in buffer */ 75 }; 76 77 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 78 #define LOCHASH(i) (((int)i)&(NDIRHASH-1)) 79 80 static long dd_loccnt; /* Index of entry for sequential readdir's */ 81 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 82 83 /* 84 * return a pointer into a directory 85 */ 86 long 87 telldir(dirp) 88 const DIR *dirp; 89 { 90 long idx; 91 struct ddloc *lp; 92 93 94 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 95 return (-1); 96 idx = dd_loccnt++; 97 lp->loc_index = idx; 98 lp->loc_seek = dirp->dd_seek; 99 lp->loc_loc = dirp->dd_loc; 100 lp->loc_next = dd_hash[LOCHASH(idx)]; 101 dd_hash[LOCHASH(idx)] = lp; 102 return (idx); 103 } 104 105 /* 106 * seek to an entry in a directory. 107 * Only values returned by "telldir" should be passed to seekdir. 108 */ 109 void 110 __seekdir(dirp, loc) 111 DIR *dirp; 112 long loc; 113 { 114 struct ddloc *lp; 115 struct ddloc **prevlp; 116 struct dirent *dp; 117 118 _DIAGASSERT(dirp != NULL); 119 120 prevlp = &dd_hash[LOCHASH(loc)]; 121 lp = *prevlp; 122 while (lp != NULL) { 123 if (lp->loc_index == loc) 124 break; 125 prevlp = &lp->loc_next; 126 lp = lp->loc_next; 127 } 128 if (lp == NULL) 129 return; 130 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 131 goto found; 132 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 133 dirp->dd_seek = lp->loc_seek; 134 dirp->dd_loc = 0; 135 while (dirp->dd_loc < lp->loc_loc) { 136 dp = readdir(dirp); 137 if (dp == NULL) 138 break; 139 } 140 found: 141 #ifdef SINGLEUSE 142 *prevlp = lp->loc_next; 143 free(lp); 144 #endif 145 } 146