lib/libc/gen/telldir.c

   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  * $DragonFly: src/lib/libc/gen/telldir.c,v 1.4 2005/11/13 00:07:42 swildner Exp $
  35  *
  36  * @(#)telldir.c        8.1 (Berkeley) 6/4/93
  37  */
  38
  39 #include "namespace.h"
  40 #include <sys/param.h>
  41 #include <dirent.h>
  42 #include <pthread.h>
  43 #include <stdlib.h>
  44 #include <unistd.h>
  45 #include "un-namespace.h"
  46
  47 #include "libc_private.h"
  48
  49 /*
  50  * The option SINGLEUSE may be defined to say that a telldir
  51  * cookie may be used only once before it is freed. This option
  52  * is used to avoid having memory usage grow without bound.
  53  */
  54 #define SINGLEUSE
  55
  56 /*
  57  * One of these structures is malloced to describe the current directory
  58  * position each time telldir is called. It records the current magic
  59  * cookie returned by getdirentries and the offset within the buffer
  60  * associated with that return value.
  61  */
  62 struct ddloc {
  63         struct  ddloc *loc_next;/* next structure in list */
  64         long    loc_index;      /* key associated with structure */
  65         long    loc_seek;       /* magic cookie returned by getdirentries */
  66         long    loc_loc;        /* offset of entry in buffer */
  67         const DIR* loc_dirp;    /* directory which used this entry */
  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(const DIR *dirp)
  81 {
  82         int index;
  83         struct ddloc *lp;
  84
  85         if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
  86                 return (-1);
  87         if (__isthreaded)
  88                 _pthread_mutex_lock((pthread_mutex_t *)&dirp->dd_lock);
  89         index = dd_loccnt++;
  90         lp->loc_index = index;
  91         lp->loc_seek = dirp->dd_seek;
  92         lp->loc_loc = dirp->dd_loc;
  93         lp->loc_dirp = dirp;
  94         lp->loc_next = dd_hash[LOCHASH(index)];
  95         dd_hash[LOCHASH(index)] = lp;
  96         if (__isthreaded)
  97                 _pthread_mutex_unlock((pthread_mutex_t *)&dirp->dd_lock);
  98         return (index);
  99 }
 100
 101 /*
 102  * seek to an entry in a directory.
 103  * Only values returned by "telldir" should be passed to seekdir.
 104  */
 105 void
 106 _seekdir(DIR *dirp, long loc)
 107 {
 108         struct ddloc *lp;
 109         struct ddloc **prevlp;
 110         struct dirent *dp;
 111
 112         prevlp = &dd_hash[LOCHASH(loc)];
 113         lp = *prevlp;
 114         while (lp != NULL) {
 115                 if (lp->loc_index == loc)
 116                         break;
 117                 prevlp = &lp->loc_next;
 118                 lp = lp->loc_next;
 119         }
 120         if (lp == NULL)
 121                 return;
 122         if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
 123                 goto found;
 124         lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
 125         dirp->dd_seek = lp->loc_seek;
 126         dirp->dd_loc = 0;
 127         while (dirp->dd_loc < lp->loc_loc) {
 128                 dp = _readdir_unlocked(dirp);
 129                 if (dp == NULL)
 130                         break;
 131         }
 132 found:
 133 #ifdef SINGLEUSE
 134         *prevlp = lp->loc_next;
 135         free((caddr_t)lp);
 136 #endif
 137 }
 138
 139 /*
 140  * Reclaim memory for telldir cookies which weren't used.
 141  */
 142 void
 143 _reclaim_telldir(DIR *dirp)
 144 {
 145         struct ddloc *lp;
 146         struct ddloc **prevlp;
 147         int i;
 148
 149         for (i = 0; i < NDIRHASH; i++) {
 150                 prevlp = &dd_hash[i];
 151                 lp = *prevlp;
 152                 while (lp != NULL) {
 153                         if (lp->loc_dirp == dirp) {
 154                                 *prevlp = lp->loc_next;
 155                                 free((caddr_t)lp);
 156                                 lp = *prevlp;
 157                                 continue;
 158                         }
 159                         prevlp = &lp->loc_next;
 160                         lp = lp->loc_next;
 161                 }
 162         }
 163 }