glibc/sysdeps/unix/sysv/linux/readdir64.c

/* Read a directory.  Linux LFS version.
   Copyright (C) 1997-2021 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

/* When _DIRENT_MATCHES_DIRENT64 is defined we can alias 'readdir64' to
   'readdir'.  However the function signatures are not equal due
   different return types, so we need to suppress {__}readdir so weak
   and strong alias do not throw conflicting types errors.  */
#define readdir   __no_readdir_decl
#define __readdir __no___readdir_decl
#include <dirent.h>
#undef __readdir
#undef readdir

/* Read a directory entry from DIRP.  */
struct dirent64 *
__readdir64 (DIR *dirp)
{
  struct dirent64 *dp;
  int saved_errno = errno;

#if IS_IN (libc)
  __libc_lock_lock (dirp->lock);
#endif

  do
    {
      size_t reclen;

      if (dirp->offset >= dirp->size)
	{
	  /* We've emptied out our buffer.  Refill it.  */

	  size_t maxread = dirp->allocation;
	  ssize_t bytes;

	  bytes = __getdents64 (dirp->fd, dirp->data, maxread);
	  if (bytes <= 0)
	    {
	      /* On some systems getdents fails with ENOENT when the
		 open directory has been rmdir'd already.  POSIX.1
		 requires that we treat this condition like normal EOF.  */
	      if (bytes < 0 && errno == ENOENT)
		bytes = 0;

	      /* Don't modifiy errno when reaching EOF.  */
	      if (bytes == 0)
		__set_errno (saved_errno);
	      dp = NULL;
	      break;
	    }
	  dirp->size = (size_t) bytes;

	  /* Reset the offset into the buffer.  */
	  dirp->offset = 0;
	}

      dp = (struct dirent64 *) &dirp->data[dirp->offset];

      reclen = dp->d_reclen;

      dirp->offset += reclen;

      dirp->filepos = dp->d_off;

      /* Skip deleted files.  */
    } while (dp->d_ino == 0);

#if IS_IN (libc)
  __libc_lock_unlock (dirp->lock);
#endif

  return dp;
}
libc_hidden_def (__readdir64)

#if _DIRENT_MATCHES_DIRENT64
strong_alias (__readdir64, __readdir)
weak_alias (__readdir64, readdir64)
weak_alias (__readdir64, readdir)
#else
/* The compat code expects the 'struct direct' with d_ino being a __ino_t
   instead of __ino64_t.  */
# include <shlib-compat.h>
# if IS_IN(rtld)
weak_alias (__readdir64, readdir64)
# else
versioned_symbol (libc, __readdir64, readdir64, GLIBC_2_2);
# endif
# if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
#  include <olddirent.h>

attribute_compat_text_section
struct __old_dirent64 *
__old_readdir64 (DIR *dirp)
{
  struct __old_dirent64 *dp;
  int saved_errno = errno;

#if IS_IN (libc)
  __libc_lock_lock (dirp->lock);
#endif

  do
    {
      size_t reclen;

      if (dirp->offset >= dirp->size)
	{
	  /* We've emptied out our buffer.  Refill it.  */

	  size_t maxread = dirp->allocation;
	  ssize_t bytes;

	  bytes = __old_getdents64 (dirp->fd, dirp->data, maxread);
	  if (bytes <= 0)
	    {
	      /* On some systems getdents fails with ENOENT when the
		 open directory has been rmdir'd already.  POSIX.1
		 requires that we treat this condition like normal EOF.  */
	      if (bytes < 0 && errno == ENOENT)
		bytes = 0;

	      /* Don't modifiy errno when reaching EOF.  */
	      if (bytes == 0)
		__set_errno (saved_errno);
	      dp = NULL;
	      break;
	    }
	  dirp->size = (size_t) bytes;

	  /* Reset the offset into the buffer.  */
	  dirp->offset = 0;
	}

      dp = (struct __old_dirent64 *) &dirp->data[dirp->offset];

      reclen = dp->d_reclen;

      dirp->offset += reclen;

      dirp->filepos = dp->d_off;

      /* Skip deleted files.  */
    } while (dp->d_ino == 0);

#if IS_IN (libc)
  __libc_lock_unlock (dirp->lock);
#endif

  return dp;
}
libc_hidden_def (__old_readdir64)
compat_symbol (libc, __old_readdir64, readdir64, GLIBC_2_1);
# endif /* SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)  */
#endif /* _DIRENT_MATCHES_DIRENT64  */