1 /* 2 * Copyright (c) 1983, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * $FreeBSD: src/lib/libc/gen/telldir.c,v 1.4.12.1 2001/03/05 09:39:59 obrien Exp $ 34 */ 35 36 #if defined(LIBC_SCCS) && !defined(lint) 37 static char sccsid[] = "@(#)telldir.c 8.1 (Berkeley) 6/4/93"; 38 #endif /* LIBC_SCCS and not lint */ 39 40 #include <sys/param.h> 41 #include <dirent.h> 42 #include <stdlib.h> 43 #include <unistd.h> 44 45 /* 46 * The option SINGLEUSE may be defined to say that a telldir 47 * cookie may be used only once before it is freed. This option 48 * is used to avoid having memory usage grow without bound. 49 */ 50 #define SINGLEUSE 51 52 /* 53 * One of these structures is malloced to describe the current directory 54 * position each time telldir is called. It records the current magic 55 * cookie returned by getdirentries and the offset within the buffer 56 * associated with that return value. 57 */ 58 struct ddloc { 59 struct ddloc *loc_next;/* next structure in list */ 60 long loc_index; /* key associated with structure */ 61 long loc_seek; /* magic cookie returned by getdirentries */ 62 long loc_loc; /* offset of entry in buffer */ 63 const DIR* loc_dirp; /* directory which used this entry */ 64 }; 65 66 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 67 #define LOCHASH(i) ((i)&(NDIRHASH-1)) 68 69 static long dd_loccnt; /* Index of entry for sequential readdir's */ 70 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 71 72 /* 73 * return a pointer into a directory 74 */ 75 long 76 telldir(dirp) 77 const DIR *dirp; 78 { 79 int index; 80 struct ddloc *lp; 81 82 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 83 return (-1); 84 index = dd_loccnt++; 85 lp->loc_index = index; 86 lp->loc_seek = dirp->dd_seek; 87 lp->loc_loc = dirp->dd_loc; 88 lp->loc_dirp = dirp; 89 lp->loc_next = dd_hash[LOCHASH(index)]; 90 dd_hash[LOCHASH(index)] = lp; 91 return (index); 92 } 93 94 /* 95 * seek to an entry in a directory. 96 * Only values returned by "telldir" should be passed to seekdir. 97 */ 98 void 99 _seekdir(dirp, loc) 100 DIR *dirp; 101 long loc; 102 { 103 struct ddloc *lp; 104 struct ddloc **prevlp; 105 struct dirent *dp; 106 107 prevlp = &dd_hash[LOCHASH(loc)]; 108 lp = *prevlp; 109 while (lp != NULL) { 110 if (lp->loc_index == loc) 111 break; 112 prevlp = &lp->loc_next; 113 lp = lp->loc_next; 114 } 115 if (lp == NULL) 116 return; 117 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 118 goto found; 119 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 120 dirp->dd_seek = lp->loc_seek; 121 dirp->dd_loc = 0; 122 while (dirp->dd_loc < lp->loc_loc) { 123 dp = readdir(dirp); 124 if (dp == NULL) 125 break; 126 } 127 found: 128 #ifdef SINGLEUSE 129 *prevlp = lp->loc_next; 130 free((caddr_t)lp); 131 #endif 132 } 133 134 /* 135 * Reclaim memory for telldir cookies which weren't used. 136 */ 137 void 138 _reclaim_telldir(dirp) 139 const DIR *dirp; 140 { 141 struct ddloc *lp; 142 struct ddloc **prevlp; 143 int i; 144 145 for (i = 0; i < NDIRHASH; i++) { 146 prevlp = &dd_hash[i]; 147 lp = *prevlp; 148 while (lp != NULL) { 149 if (lp->loc_dirp == dirp) { 150 *prevlp = lp->loc_next; 151 free((caddr_t)lp); 152 lp = *prevlp; 153 continue; 154 } 155 prevlp = &lp->loc_next; 156 lp = lp->loc_next; 157 } 158 } 159 } 160