/* Copyright (C) 1991-2018 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

   <http://www.gnu.org/licenses/>.  */

#include <dirent.h>

#include <fcntl.h>

#include <errno.h>

#include <stdio.h>	/* For BUFSIZ.  */

#include <sys/param.h>	/* For MIN and MAX.  */

#include <not-cancel.h>

/* The st_blksize value of the directory is used as a hint for the

   size of the buffer which receives struct dirent values from the

   kernel.  st_blksize is limited to MAX_DIR_BUFFER_SIZE, in case the

   file system provides a bogus value.  */

#define MAX_DIR_BUFFER_SIZE 1048576U

enum {

  opendir_oflags = O_RDONLY|O_NDELAY|O_DIRECTORY|O_LARGEFILE|O_CLOEXEC

};

static bool

invalid_name (const char *name)

{

  if (__glibc_unlikely (name[0] == '\0'))

    {

      /* POSIX.1-1990 says an empty name gets ENOENT;

	 but `open' might like it fine.  */

      __set_errno (ENOENT);

      return true;

    }

  return false;

}

static DIR *

opendir_tail (int fd)

{

  if (__glibc_unlikely (fd < 0))

    return NULL;

  /* Now make sure this really is a directory and nothing changed since the

     `stat' call.  The S_ISDIR check is superfluous if O_DIRECTORY works,

     but it's cheap and we need the stat call for st_blksize anyway.  */

  struct stat64 statbuf;

  if (__glibc_unlikely (__fxstat64 (_STAT_VER, fd, &statbuf) < 0))

    goto lose;

  if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode)))

    {

      __set_errno (ENOTDIR);

    lose:

      __close_nocancel_nostatus (fd);

      return NULL;

    }

  return __alloc_dir (fd, true, 0, &statbuf);

}

#if IS_IN (libc)

DIR *

__opendirat (int dfd, const char *name)

{

  if (__glibc_unlikely (invalid_name (name)))

    return NULL;

  return opendir_tail (__openat_nocancel (dfd, name, opendir_oflags));

}

#endif

/* Open a directory stream on NAME.  */

DIR *

__opendir (const char *name)

{

  if (__glibc_unlikely (invalid_name (name)))

    return NULL;

  return opendir_tail (__open_nocancel (name, opendir_oflags));

}

weak_alias (__opendir, opendir)

DIR *

__alloc_dir (int fd, bool close_fd, int flags, const struct stat64 *statp)

{

  /* We have to set the close-on-exit flag if the user provided the

     file descriptor.  */

  if (!close_fd

      && __glibc_unlikely (__fcntl64_nocancel (fd, F_SETFD, FD_CLOEXEC) < 0))

	goto lose;

  const size_t default_allocation = (4 * BUFSIZ < sizeof (struct dirent64)

				     ? sizeof (struct dirent64) : 4 * BUFSIZ);

  const size_t small_allocation = (BUFSIZ < sizeof (struct dirent64)

				   ? sizeof (struct dirent64) : BUFSIZ);

  size_t allocation = default_allocation;

#ifdef _STATBUF_ST_BLKSIZE

  /* Increase allocation if requested, but not if the value appears to

     be bogus.  */

  if (statp != NULL)

    allocation = MIN (MAX ((size_t) statp->st_blksize, default_allocation),

		      MAX_DIR_BUFFER_SIZE);

#endif

  DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation);

  if (dirp == NULL)

    {

      allocation = small_allocation;

      dirp = (DIR *) malloc (sizeof (DIR) + allocation);

      if (dirp == NULL)

      lose:

	{

	  if (close_fd)

	    {

	      int save_errno = errno;

	      __close_nocancel_nostatus (fd);

	      __set_errno (save_errno);

	    }

	  return NULL;

	}

    }

  dirp->fd = fd;

#if IS_IN (libc)

  __libc_lock_init (dirp->lock);

#endif

  dirp->allocation = allocation;

  dirp->size = 0;

  dirp->offset = 0;

  dirp->filepos = 0;

  dirp->errcode = 0;

  return dirp;

}