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[] = "@(#)telldir.c 8.1 (Berkeley) 6/4/93"; 36 #endif /* LIBC_SCCS and not lint */ 37 38 #include <sys/param.h> 39 #include <dirent.h> 40 #include <stdlib.h> 41 #include <unistd.h> 42 43 /* 44 * The option SINGLEUSE may be defined to say that a telldir 45 * cookie may be used only once before it is freed. This option 46 * is used to avoid having memory usage grow without bound. 47 */ 48 #define SINGLEUSE 49 50 /* 51 * One of these structures is malloced to describe the current directory 52 * position each time telldir is called. It records the current magic 53 * cookie returned by getdirentries and the offset within the buffer 54 * associated with that return value. 55 */ 56 struct ddloc { 57 struct ddloc *loc_next;/* next structure in list */ 58 long loc_index; /* key associated with structure */ 59 long loc_seek; /* magic cookie returned by getdirentries */ 60 long loc_loc; /* offset of entry in buffer */ 61 const DIR* loc_dirp; /* directory which used this entry */ 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_dirp = dirp; 87 lp->loc_next = dd_hash[LOCHASH(index)]; 88 dd_hash[LOCHASH(index)] = lp; 89 return (index); 90 } 91 92 /* 93 * seek to an entry in a directory. 94 * Only values returned by "telldir" should be passed to seekdir. 95 */ 96 void 97 _seekdir(dirp, loc) 98 register DIR *dirp; 99 long loc; 100 { 101 register struct ddloc *lp; 102 register struct ddloc **prevlp; 103 struct dirent *dp; 104 105 prevlp = &dd_hash[LOCHASH(loc)]; 106 lp = *prevlp; 107 while (lp != NULL) { 108 if (lp->loc_index == loc) 109 break; 110 prevlp = &lp->loc_next; 111 lp = lp->loc_next; 112 } 113 if (lp == NULL) 114 return; 115 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 116 goto found; 117 (void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET); 118 dirp->dd_seek = lp->loc_seek; 119 dirp->dd_loc = 0; 120 while (dirp->dd_loc < lp->loc_loc) { 121 dp = readdir(dirp); 122 if (dp == NULL) 123 break; 124 } 125 found: 126 #ifdef SINGLEUSE 127 *prevlp = lp->loc_next; 128 free((caddr_t)lp); 129 #endif 130 } 131 132 /* 133 * Reclaim memory for telldir cookies which weren't used. 134 */ 135 void 136 _reclaim_telldir(dirp) 137 register const DIR *dirp; 138 { 139 register struct ddloc *lp; 140 register struct ddloc **prevlp; 141 int i; 142 143 for (i = 0; i < NDIRHASH; i++) { 144 prevlp = &dd_hash[i]; 145 lp = *prevlp; 146 while (lp != NULL) { 147 if (lp->loc_dirp == dirp) { 148 *prevlp = lp->loc_next; 149 free((caddr_t)lp); 150 lp = *prevlp; 151 continue; 152 } 153 prevlp = &lp->loc_next; 154 lp = lp->loc_next; 155 } 156 } 157 } 158