sysdeps/unix/readdir.c

   1 /* Copyright (C) 1991-1997,1999,2000,2002,2007 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    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
  31 # define __READDIR __readdir
  32 # define __GETDENTS __getdents
  33 # define DIRENT_TYPE struct dirent
  34 # define __READDIR_ALIAS
  35 #endif
  36
  37 /* Read a directory entry from DIRP.  */
  38 DIRENT_TYPE *
  39 __READDIR (DIR *dirp)
  40 {
  41   DIRENT_TYPE *dp;
  42   int saved_errno = errno;
  43
  44 #ifndef NOT_IN_libc
  45   __libc_lock_lock (dirp->lock);
  46 #endif
  47
  48   do
  49     {
  50       size_t reclen;
  51
  52       if (dirp->offset >= dirp->size)
  53         {
  54           /* We've emptied out our buffer.  Refill it.  */
  55
  56           size_t maxread;
  57           ssize_t bytes;
  58
  59 #ifndef _DIRENT_HAVE_D_RECLEN
  60           /* Fixed-size struct; must read one at a time (see below).  */
  61           maxread = sizeof *dp;
  62 #else
  63           maxread = dirp->allocation;
  64 #endif
  65
  66           bytes = __GETDENTS (dirp->fd, dirp->data, maxread);
  67           if (bytes <= 0)
  68             {
  69               /* On some systems getdents fails with ENOENT when the
  70                  open directory has been rmdir'd already.  POSIX.1
  71                  requires that we treat this condition like normal EOF.  */
  72               if (bytes < 0 && errno == ENOENT)
  73                 bytes = 0;
  74
  75               /* Don't modifiy errno when reaching EOF.  */
  76               if (bytes == 0)
  77                 __set_errno (saved_errno);
  78               dp = NULL;
  79               break;
  80             }
  81           dirp->size = (size_t) bytes;
  82
  83           /* Reset the offset into the buffer.  */
  84           dirp->offset = 0;
  85         }
  86
  87       dp = (DIRENT_TYPE *) &dirp->data[dirp->offset];
  88
  89 #ifdef _DIRENT_HAVE_D_RECLEN
  90       reclen = dp->d_reclen;
  91 #else
  92       /* The only version of `struct dirent*' that lacks `d_reclen'
  93          is fixed-size.  */
  94       assert (sizeof dp->d_name > 1);
  95       reclen = sizeof *dp;
  96       /* The name is not terminated if it is the largest possible size.
  97          Clobber the following byte to ensure proper null termination.  We
  98          read jst one entry at a time above so we know that byte will not
  99          be used later.  */
 100       dp->d_name[sizeof dp->d_name] = '\0';
 101 #endif
 102
 103       dirp->offset += reclen;
 104
 105 #ifdef _DIRENT_HAVE_D_OFF
 106       dirp->filepos = dp->d_off;
 107 #else
 108       dirp->filepos += reclen;
 109 #endif
 110
 111       /* Skip deleted files.  */
 112     } while (dp->d_ino == 0);
 113
 114 #ifndef NOT_IN_libc
 115   __libc_lock_unlock (dirp->lock);
 116 #endif
 117
 118   return dp;
 119 }
 120
 121 #ifdef __READDIR_ALIAS
 122 weak_alias (__readdir, readdir)
 123 #endif