sysdeps/unix/readdir.c

   1 /* Copyright (C) 1991, 92, 93, 94, 95, 96, 97 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
  31 /* Read a directory entry from DIRP.  */
  32 struct dirent *
  33 __readdir (DIR *dirp)
  34 {
  35   struct dirent *dp;
  36
  37   __libc_lock_lock (dirp->lock);
  38
  39   do
  40     {
  41       size_t reclen;
  42
  43       if (dirp->offset >= dirp->size)
  44         {
  45           /* We've emptied out our buffer.  Refill it.  */
  46
  47           size_t maxread;
  48           off_t base;
  49           ssize_t bytes;
  50
  51 #ifndef _DIRENT_HAVE_D_RECLEN
  52           /* Fixed-size struct; must read one at a time (see below).  */
  53           maxread = sizeof *dp;
  54 #else
  55           maxread = dirp->allocation;
  56 #endif
  57
  58           base = dirp->filepos;
  59           bytes = __getdirentries (dirp->fd, dirp->data, maxread, &base);
  60           if (bytes <= 0)
  61             {
  62               dp = NULL;
  63               break;
  64             }
  65           dirp->size = (size_t) bytes;
  66
  67           /* Reset the offset into the buffer.  */
  68           dirp->offset = 0;
  69         }
  70
  71       dp = (struct dirent *) &dirp->data[dirp->offset];
  72
  73 #ifdef _DIRENT_HAVE_D_RECLEN
  74       reclen = dp->d_reclen;
  75 #else
  76       /* The only version of `struct dirent' that lacks `d_reclen'
  77          is fixed-size.  */
  78       assert (sizeof dp->d_name > 1);
  79       reclen = sizeof *dp;
  80       /* The name is not terminated if it is the largest possible size.
  81          Clobber the following byte to ensure proper null termination.  We
  82          read jst one entry at a time above so we know that byte will not
  83          be used later.  */
  84       dp->d_name[sizeof dp->d_name] = '\0';
  85 #endif
  86
  87       dirp->offset += reclen;
  88
  89 #ifdef _DIRENT_HAVE_D_OFF
  90       dirp->filepos = dp->d_off;
  91 #else
  92       dirp->filepos += reclen;
  93 #endif
  94
  95       /* Skip deleted files.  */
  96     } while (dp->d_ino == 0);
  97
  98   __libc_lock_unlock (dirp->lock);
  99
 100   return dp;
 101 }
 102 weak_alias (__readdir, readdir)