sysdeps/unix/readdir.c

   1 /* Copyright (C) 1991, 92, 93, 94, 95, 96 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
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, 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   if (dirp == NULL || dirp->data == NULL)
  38     {
  39       errno = EINVAL;
  40       return NULL;
  41     }
  42
  43   do
  44     {
  45       size_t reclen;
  46
  47       if (dirp->offset >= dirp->size)
  48         {
  49           /* We've emptied out our buffer.  Refill it.  */
  50
  51           size_t maxread;
  52           off_t base;
  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           base = dirp->filepos;
  63           bytes = __getdirentries (dirp->fd, dirp->data, maxread, &base);
  64           if (bytes <= 0)
  65             return NULL;
  66           dirp->size = (size_t) bytes;
  67
  68           /* Reset the offset into the buffer.  */
  69           dirp->offset = 0;
  70         }
  71
  72       dp = (struct dirent *) &dirp->data[dirp->offset];
  73
  74 #ifdef _DIRENT_HAVE_D_RECLEN
  75       reclen = dp->d_reclen;
  76 #else
  77       /* The only version of `struct dirent' that lacks `d_reclen'
  78          is fixed-size.  */
  79       assert (sizeof dp->d_name > 1);
  80       reclen = sizeof *dp;
  81       /* The name is not terminated if it is the largest possible size.
  82          Clobber the following byte to ensure proper null termination.  We
  83          read jst one entry at a time above so we know that byte will not
  84          be used later.  */
  85       dp->d_name[sizeof dp->d_name] = '\0';
  86 #endif
  87
  88       dirp->offset += reclen;
  89
  90 #ifdef _DIRENT_HAVE_D_OFF
  91       dirp->filepos = dp->d_off;
  92 #else
  93       dirp->filepos += reclen;
  94 #endif
  95
  96       /* Skip deleted files.  */
  97     } while (dp->d_ino == 0);
  98
  99   return dp;
 100 }