newlib/libc/posix/telldir.c

   1 #ifndef HAVE_OPENDIR
   2
   3 /*
   4  * Copyright (c) 1983 Regents of the University of California.
   5  * 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. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #if defined(LIBC_SCCS) && !defined(lint)
  33 static char sccsid[] = "@(#)telldir.c   5.9 (Berkeley) 2/23/91";
  34 #endif /* LIBC_SCCS and not lint */
  35
  36 #include <sys/param.h>
  37 #include <dirent.h>
  38 #include <stdlib.h>
  39 #include <unistd.h>
  40 #include <sys/lock.h>
  41
  42 /*
  43  * The option SINGLEUSE may be defined to say that a telldir
  44  * cookie may be used only once before it is freed. This option
  45  * is used to avoid having memory usage grow without bound.
  46  */
  47 #define SINGLEUSE
  48
  49 /*
  50  * One of these structures is malloced to describe the current directory
  51  * position each time telldir is called. It records the current magic
  52  * cookie returned by getdirentries and the offset within the buffer
  53  * associated with that return value.
  54  */
  55 struct ddloc {
  56         struct  ddloc *loc_next;/* next structure in list */
  57         long    loc_index;      /* key associated with structure */
  58         long    loc_seek;       /* magic cookie returned by getdirentries */
  59         long    loc_loc;        /* offset of entry in buffer */
  60         DIR    *loc_dirp;       /* DIR pointer */
  61 };
  62
  63 #define NDIRHASH        32      /* Num of hash lists, must be a power of 2 */
  64 #define LOCHASH(i)      ((i)&(NDIRHASH-1))
  65
  66 static long     dd_loccnt = 1;  /* Index of entry for sequential readdir's */
  67 static struct   ddloc *dd_hash[NDIRHASH];   /* Hash list heads for ddlocs */
  68
  69 #if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
  70 __LOCK_INIT(static, __dd_hash_mutex);
  71 #endif
  72
  73 /*
  74  * return a pointer into a directory
  75  */
  76
  77 #if !defined(_ELIX_LEVEL) || (_ELIX_LEVEL >= 2)
  78
  79 long
  80 telldir (DIR *dirp)
  81 {
  82         register int index;
  83         register struct ddloc *lp;
  84
  85         if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
  86                 return (-1);
  87
  88 #ifdef HAVE_DD_LOCK
  89         __lock_acquire_recursive(dirp->dd_lock);
  90 #ifndef __SINGLE_THREAD__
  91         __lock_acquire(__dd_hash_mutex);
  92 #endif
  93 #endif
  94         index = dd_loccnt++;
  95         lp->loc_index = index;
  96         lp->loc_seek = dirp->dd_seek;
  97         lp->loc_loc = dirp->dd_loc;
  98         lp->loc_dirp = dirp;
  99         lp->loc_next = dd_hash[LOCHASH(index)];
 100         dd_hash[LOCHASH(index)] = lp;
 101 #ifdef HAVE_DD_LOCK
 102 #ifndef __SINGLE_THREAD__
 103         __lock_release(__dd_hash_mutex);
 104 #endif
 105         __lock_release_recursive(dirp->dd_lock);
 106 #endif
 107         return (index);
 108 }
 109
 110 #endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 2 */
 111
 112 /*
 113  * seek to an entry in a directory.
 114  * Only values returned by "telldir" should be passed to seekdir.
 115  */
 116 void
 117 _seekdir (register DIR *dirp,
 118         long loc)
 119 {
 120         register struct ddloc *lp;
 121         register struct ddloc **prevlp;
 122         struct dirent *dp;
 123
 124 #if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
 125         __lock_acquire(__dd_hash_mutex);
 126 #endif
 127         if (loc != 0) {
 128                 prevlp = &dd_hash[LOCHASH(loc)];
 129                 lp = *prevlp;
 130                 while (lp != NULL) {
 131                         if (lp->loc_index == loc)
 132                                 break;
 133                         prevlp = &lp->loc_next;
 134                         lp = lp->loc_next;
 135                 }
 136                 if (lp == NULL) {
 137 #if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
 138                         __lock_release(__dd_hash_mutex);
 139 #endif
 140                         return;
 141                 }
 142                 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
 143                         goto found;
 144                 (void) lseek(dirp->dd_fd, lp->loc_seek, 0);
 145                 dirp->dd_seek = lp->loc_seek;
 146                 dirp->dd_loc = 0;
 147                 while (dirp->dd_loc < lp->loc_loc) {
 148                         dp = readdir(dirp);
 149                         if (dp == NULL)
 150                                 break;
 151                 }
 152 found:
 153 #ifdef SINGLEUSE
 154                 *prevlp = lp->loc_next;
 155                 free((caddr_t)lp);
 156 #endif
 157         } else {
 158                 // loc 0 means rewinding
 159                 (void) lseek(dirp->dd_fd, 0, 0);
 160                 dirp->dd_seek = 0;
 161                 dirp->dd_loc = 0;
 162         }
 163 #if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
 164         __lock_release(__dd_hash_mutex);
 165 #endif
 166 }
 167
 168 /* clean out any hash entries from a closed directory */
 169 void
 170 _cleanupdir (register DIR *dirp)
 171 {
 172         int i;
 173
 174 #if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
 175         __lock_acquire(__dd_hash_mutex);
 176 #endif
 177         for (i = 0; i < NDIRHASH; ++i) {
 178                 struct ddloc head;
 179                 register struct ddloc *lp;
 180                 register struct ddloc *prevlp;
 181
 182                 lp = dd_hash[i];
 183                 head.loc_next = lp;
 184                 prevlp = &head;
 185                 while (lp != NULL) {
 186                         struct ddloc *nextlp;
 187
 188                         nextlp = lp->loc_next;
 189                         if (lp->loc_dirp == dirp) {
 190                                 prevlp->loc_next = nextlp;
 191                                 free((caddr_t)lp);
 192                         }
 193                         else
 194                                 prevlp = lp;
 195                         lp = nextlp;
 196                 }
 197                 dd_hash[i] = head.loc_next;
 198         }
 199 #if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
 200         __lock_release(__dd_hash_mutex);
 201 #endif
 202
 203 }
 204 #endif /* ! HAVE_OPENDIR */