lib/libc/gen/telldir.c

   1 /*      $NetBSD: telldir.c,v 1.20 2013/03/06 11:27:28 yamt Exp $        */
   2
   3 /*
   4  * Copyright (c) 1983, 1993
   5  *      The Regents of the University of California.  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 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 #if 0
  35 static char sccsid[] = "@(#)telldir.c   8.1 (Berkeley) 6/4/93";
  36 #else
  37 __RCSID("$NetBSD: telldir.c,v 1.20 2013/03/06 11:27:28 yamt Exp $");
  38 #endif
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include "namespace.h"
  42 #include "reentrant.h"
  43 #include "extern.h"
  44 #include <sys/param.h>
  45
  46 #include <assert.h>
  47 #include <dirent.h>
  48 #include <stdlib.h>
  49 #include <unistd.h>
  50
  51 #include "dirent_private.h"
  52
  53 #ifdef __weak_alias
  54 __weak_alias(telldir,_telldir)
  55 #endif
  56
  57 long
  58 telldir(DIR *dirp)
  59 {
  60         long rv;
  61 #ifdef _REENTRANT
  62         if (__isthreaded) {
  63                 mutex_lock((mutex_t *)dirp->dd_lock);
  64                 rv = _telldir_unlocked(dirp);
  65                 mutex_unlock((mutex_t *)dirp->dd_lock);
  66         } else
  67 #endif
  68                 rv = _telldir_unlocked(dirp);
  69         return rv;
  70 }
  71
  72 /*
  73  * return a pointer into a directory
  74  */
  75 long
  76 _telldir_unlocked(DIR *dirp)
  77 {
  78         struct dirpos *lp;
  79
  80         for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
  81                 if (lp->dp_seek == dirp->dd_seek &&
  82                     lp->dp_loc == dirp->dd_loc)
  83                         return (intptr_t)lp;
  84
  85         if ((lp = malloc(sizeof(*lp))) == NULL)
  86                 return (-1);
  87
  88         lp->dp_seek = dirp->dd_seek;
  89         lp->dp_loc = dirp->dd_loc;
  90         lp->dp_next = dirp->dd_internal;
  91         dirp->dd_internal = lp;
  92
  93         return (intptr_t)lp;
  94 }
  95
  96 /*
  97  * seek to an entry in a directory.
  98  * Only values returned by "telldir" should be passed to seekdir.
  99  */
 100 void
 101 _seekdir_unlocked(DIR *dirp, long loc)
 102 {
 103         struct dirpos *lp;
 104
 105         _DIAGASSERT(dirp != NULL);
 106
 107         for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
 108                 if ((intptr_t)lp == loc)
 109                         break;
 110
 111         if (lp == NULL)
 112                 return;
 113
 114         if (lp->dp_loc == dirp->dd_loc && lp->dp_seek == dirp->dd_seek)
 115                 return;
 116
 117         dirp->dd_seek = lseek(dirp->dd_fd, lp->dp_seek, SEEK_SET);
 118         dirp->dd_loc = 0;
 119         while (dirp->dd_loc < lp->dp_loc)
 120                 if (_readdir_unlocked(dirp, 0) == NULL)
 121                         break;
 122 }