1 /* $NetBSD: telldir.c,v 1.5 1997/07/13 19:46:20 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. 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 1.5 1997/07/13 19:46:20 christos Exp $"); 42 #endif 43 #endif /* LIBC_SCCS and not lint */ 44 45 #include <sys/param.h> 46 #include <dirent.h> 47 #include <stdlib.h> 48 #include <unistd.h> 49 50 /* 51 * The option SINGLEUSE may be defined to say that a telldir 52 * cookie may be used only once before it is freed. This option 53 * is used to avoid having memory usage grow without bound. 54 */ 55 #define SINGLEUSE 56 57 /* 58 * One of these structures is malloced to describe the current directory 59 * position each time telldir is called. It records the current magic 60 * cookie returned by getdirentries and the offset within the buffer 61 * associated with that return value. 62 */ 63 struct ddloc { 64 struct ddloc *loc_next;/* next structure in list */ 65 long loc_index; /* key associated with structure */ 66 long loc_seek; /* magic cookie returned by getdirentries */ 67 long loc_loc; /* offset of entry in buffer */ 68 }; 69 70 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 71 #define LOCHASH(i) ((i)&(NDIRHASH-1)) 72 73 static long dd_loccnt; /* Index of entry for sequential readdir's */ 74 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 75 76 /* 77 * return a pointer into a directory 78 */ 79 long 80 telldir(dirp) 81 const DIR *dirp; 82 { 83 register int index; 84 register struct ddloc *lp; 85 86 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 87 return (-1); 88 index = dd_loccnt++; 89 lp->loc_index = index; 90 lp->loc_seek = dirp->dd_seek; 91 lp->loc_loc = dirp->dd_loc; 92 lp->loc_next = dd_hash[LOCHASH(index)]; 93 dd_hash[LOCHASH(index)] = lp; 94 return (index); 95 } 96 97 /* 98 * seek to an entry in a directory. 99 * Only values returned by "telldir" should be passed to seekdir. 100 */ 101 void 102 __seekdir(dirp, loc) 103 register DIR *dirp; 104 long loc; 105 { 106 register struct ddloc *lp; 107 register struct ddloc **prevlp; 108 struct dirent *dp; 109 110 prevlp = &dd_hash[LOCHASH(loc)]; 111 lp = *prevlp; 112 while (lp != NULL) { 113 if (lp->loc_index == loc) 114 break; 115 prevlp = &lp->loc_next; 116 lp = lp->loc_next; 117 } 118 if (lp == NULL) 119 return; 120 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 121 goto found; 122 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 123 dirp->dd_seek = lp->loc_seek; 124 dirp->dd_loc = 0; 125 while (dirp->dd_loc < lp->loc_loc) { 126 dp = readdir(dirp); 127 if (dp == NULL) 128 break; 129 } 130 found: 131 #ifdef SINGLEUSE 132 *prevlp = lp->loc_next; 133 free((caddr_t)lp); 134 #endif 135 } 136