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 34 #if defined(LIBC_SCCS) && !defined(lint) 35 /*static char sccsid[] = "from: @(#)telldir.c 8.1 (Berkeley) 6/4/93";*/ 36 static char rcsid[] = "$Id: telldir.c,v 1.3 1994/07/27 14:39:53 jtc Exp $"; 37 #endif /* LIBC_SCCS and not lint */ 38 39 #include <sys/param.h> 40 #include <dirent.h> 41 #include <stdlib.h> 42 #include <unistd.h> 43 44 /* 45 * The option SINGLEUSE may be defined to say that a telldir 46 * cookie may be used only once before it is freed. This option 47 * is used to avoid having memory usage grow without bound. 48 */ 49 #define SINGLEUSE 50 51 /* 52 * One of these structures is malloced to describe the current directory 53 * position each time telldir is called. It records the current magic 54 * cookie returned by getdirentries and the offset within the buffer 55 * associated with that return value. 56 */ 57 struct ddloc { 58 struct ddloc *loc_next;/* next structure in list */ 59 long loc_index; /* key associated with structure */ 60 long loc_seek; /* magic cookie returned by getdirentries */ 61 long loc_loc; /* offset of entry in buffer */ 62 }; 63 64 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 65 #define LOCHASH(i) ((i)&(NDIRHASH-1)) 66 67 static long dd_loccnt; /* Index of entry for sequential readdir's */ 68 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 69 70 /* 71 * return a pointer into a directory 72 */ 73 long 74 telldir(dirp) 75 const DIR *dirp; 76 { 77 register int index; 78 register struct ddloc *lp; 79 80 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 81 return (-1); 82 index = dd_loccnt++; 83 lp->loc_index = index; 84 lp->loc_seek = dirp->dd_seek; 85 lp->loc_loc = dirp->dd_loc; 86 lp->loc_next = dd_hash[LOCHASH(index)]; 87 dd_hash[LOCHASH(index)] = lp; 88 return (index); 89 } 90 91 /* 92 * seek to an entry in a directory. 93 * Only values returned by "telldir" should be passed to seekdir. 94 */ 95 void 96 __seekdir(dirp, loc) 97 register DIR *dirp; 98 long loc; 99 { 100 register struct ddloc *lp; 101 register struct ddloc **prevlp; 102 struct dirent *dp; 103 104 prevlp = &dd_hash[LOCHASH(loc)]; 105 lp = *prevlp; 106 while (lp != NULL) { 107 if (lp->loc_index == loc) 108 break; 109 prevlp = &lp->loc_next; 110 lp = lp->loc_next; 111 } 112 if (lp == NULL) 113 return; 114 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 115 goto found; 116 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 117 dirp->dd_seek = lp->loc_seek; 118 dirp->dd_loc = 0; 119 while (dirp->dd_loc < lp->loc_loc) { 120 dp = readdir(dirp); 121 if (dp == NULL) 122 break; 123 } 124 found: 125 #ifdef SINGLEUSE 126 *prevlp = lp->loc_next; 127 free((caddr_t)lp); 128 #endif 129 } 130