lib/libc/gen/telldir.c

   1 /*      $NetBSD: telldir.c,v 1.19 2008/05/04 18:53:26 tonnerre 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 1.19 2008/05/04 18:53:26 tonnerre Exp $");
  38 #endif
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include "namespace.h"
  42 #include "reentrant.h"
  43
  44 #ifdef __minix
  45 #include <sys/types.h>
  46 #endif
  47
  48 #include "extern.h"
  49 #include <sys/param.h>
  50
  51 #include <assert.h>
  52 #include <dirent.h>
  53 #include <stdlib.h>
  54 #include <unistd.h>
  55
  56 #include "dirent_private.h"
  57
  58 #ifdef __weak_alias
  59 __weak_alias(telldir,_telldir)
  60 #endif
  61
  62 long
  63 telldir(DIR *dirp)
  64 {
  65         long rv;
  66 #ifdef _REENTRANT
  67         if (__isthreaded) {
  68                 mutex_lock((mutex_t *)dirp->dd_lock);
  69                 rv = (intptr_t)_telldir_unlocked(dirp);
  70                 mutex_unlock((mutex_t *)dirp->dd_lock);
  71         } else
  72 #endif
  73                 rv = (intptr_t)_telldir_unlocked(dirp);
  74         return rv;
  75 }
  76
  77 /*
  78  * return a pointer into a directory
  79  */
  80 long
  81 _telldir_unlocked(DIR *dirp)
  82 {
  83         struct dirpos *lp;
  84
  85         for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
  86                 if (lp->dp_seek == dirp->dd_seek &&
  87                     lp->dp_loc == dirp->dd_loc)
  88                         return (intptr_t)lp;
  89
  90         if ((lp = malloc(sizeof(*lp))) == NULL)
  91                 return (-1);
  92
  93         lp->dp_seek = dirp->dd_seek;
  94         lp->dp_loc = dirp->dd_loc;
  95         lp->dp_next = dirp->dd_internal;
  96         dirp->dd_internal = lp;
  97
  98         return (intptr_t)lp;
  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_unlocked(DIR *dirp, long loc)
 107 {
 108         struct dirpos *lp;
 109
 110         _DIAGASSERT(dirp != NULL);
 111
 112         for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
 113                 if ((intptr_t)lp == loc)
 114                         break;
 115
 116         if (lp == NULL)
 117                 return;
 118
 119         if (lp->dp_loc == dirp->dd_loc && lp->dp_seek == dirp->dd_seek)
 120                 return;
 121
 122         dirp->dd_seek = lseek(dirp->dd_fd, lp->dp_seek, SEEK_SET);
 123         dirp->dd_loc = 0;
 124         while (dirp->dd_loc < lp->dp_loc)
 125                 if (_readdir_unlocked(dirp, 0) == NULL)
 126                         break;
 127 }