sysdeps/unix/readdir_r.c

   1 /* Copyright (C) 1991,92,93,94,95,96,97,98,99,2000 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <errno.h>
  20 #include <limits.h>
  21 #include <stddef.h>
  22 #include <string.h>
  23 #include <dirent.h>
  24 #include <unistd.h>
  25 #include <sys/types.h>
  26 #include <assert.h>
  27
  28 #include <dirstream.h>
  29
  30 #ifndef __READDIR_R
  31 # define __READDIR_R __readdir_r
  32 # define __GETDENTS __getdents
  33 # define DIRENT_TYPE struct dirent
  34 # define __READDIR_R_ALIAS
  35 #endif
  36
  37 /* Read a directory entry from DIRP.  */
  38 int
  39 __READDIR_R (DIR *dirp, DIRENT_TYPE *entry, DIRENT_TYPE **result)
  40 {
  41   DIRENT_TYPE *dp;
  42   size_t reclen;
  43
  44   __libc_lock_lock (dirp->lock);
  45
  46   do
  47     {
  48       if (dirp->offset >= dirp->size)
  49         {
  50           /* We've emptied out our buffer.  Refill it.  */
  51
  52           size_t maxread;
  53           ssize_t bytes;
  54
  55 #ifndef _DIRENT_HAVE_D_RECLEN
  56           /* Fixed-size struct; must read one at a time (see below).  */
  57           maxread = sizeof *dp;
  58 #else
  59           maxread = dirp->allocation;
  60 #endif
  61
  62           bytes = __GETDENTS (dirp->fd, dirp->data, maxread);
  63           if (bytes <= 0)
  64             {
  65               dp = NULL;
  66               /* Reclen != 0 signals that an error occurred.  */
  67               reclen = bytes != 0;
  68               break;
  69             }
  70           dirp->size = (size_t) bytes;
  71
  72           /* Reset the offset into the buffer.  */
  73           dirp->offset = 0;
  74         }
  75
  76       dp = (DIRENT_TYPE *) &dirp->data[dirp->offset];
  77
  78 #ifdef _DIRENT_HAVE_D_RECLEN
  79       reclen = dp->d_reclen;
  80 #else
  81       /* The only version of `struct dirent*' that lacks `d_reclen'
  82          is fixed-size.  */
  83       assert (sizeof dp->d_name > 1);
  84       reclen = sizeof *dp;
  85       /* The name is not terminated if it is the largest possible size.
  86          Clobber the following byte to ensure proper null termination.  We
  87          read just one entry at a time above so we know that byte will not
  88          be used later.  */
  89       dp->d_name[sizeof dp->d_name] = '\0';
  90 #endif
  91
  92       dirp->offset += reclen;
  93
  94 #ifdef _DIRENT_HAVE_D_OFF
  95       dirp->filepos = dp->d_off;
  96 #else
  97       dirp->filepos += reclen;
  98 #endif
  99
 100       /* Skip deleted files.  */
 101     }
 102   while (dp->d_ino == 0);
 103
 104   if (dp != NULL)
 105     *result = memcpy (entry, dp, reclen);
 106   else
 107     *result = NULL;
 108
 109   __libc_lock_unlock (dirp->lock);
 110
 111   return dp != NULL ? 0 : reclen ? errno : 0;
 112 }
 113
 114 #ifdef __READDIR_R_ALIAS
 115 weak_alias (__readdir_r, readdir_r)
 116 #endif