/* 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 <errno.h>

#include <limits.h>

#include <stddef.h>

#include <dirent.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <unistd.h>

#include <string.h>

#include <stdlib.h>

char *__ttyname;

static char *getttyname (int fd, dev_t mydev, ino_t myino,

			 int save, int *dostat);

libc_freeres_ptr (static char *getttyname_name);

static char *

getttyname (int fd, dev_t mydev, ino_t myino, int save, int *dostat)

{

  static const char dev[] = "/dev";

  static size_t namelen;

  struct stat st;

  DIR *dirstream;

  struct dirent *d;

  dirstream = __opendir (dev);

  if (dirstream == NULL)

    {

      *dostat = -1;

      return NULL;

    }

  while ((d = __readdir (dirstream)) != NULL)

    if (((ino_t) d->d_fileno == myino || *dostat)

	&& strcmp (d->d_name, "stdin")

	&& strcmp (d->d_name, "stdout")

	&& strcmp (d->d_name, "stderr"))

      {

	size_t dlen = _D_ALLOC_NAMLEN (d);

	if (sizeof (dev) + dlen > namelen)

	  {

	    free (getttyname_name);

	    namelen = 2 * (sizeof (dev) + dlen); /* Big enough.  */

	    getttyname_name = malloc (namelen);

	    if (! getttyname_name)

	      {

		*dostat = -1;

		/* Perhaps it helps to free the directory stream buffer.  */

		(void) __closedir (dirstream);

		return NULL;

	      }

	    *((char *) __mempcpy (getttyname_name, dev, sizeof (dev) - 1))

	      = '/';

	  }

	(void) __mempcpy (&getttyname_name[sizeof (dev)], d->d_name, dlen);

	if (stat (getttyname_name, &st) == 0

#ifdef _STATBUF_ST_RDEV

	    && S_ISCHR (st.st_mode) && st.st_rdev == mydev

#else

	    && (ino_t) d->d_fileno == myino && st.st_dev == mydev

#endif

	   )

	  {

	    (void) __closedir (dirstream);

	    __ttyname = getttyname_name;

	    __set_errno (save);

	    return getttyname_name;

	  }

      }

  (void) __closedir (dirstream);

  __set_errno (save);

  return NULL;

}

/* Return the pathname of the terminal FD is open on, or NULL on errors.

   The returned storage is good only until the next call to this function.  */

char *

ttyname (int fd)

{

  struct stat st;

  int dostat = 0;

  char *name;

  int save = errno;

  if (!__isatty (fd))

    return NULL;

  if (fstat (fd, &st) < 0)

    return NULL;

#ifdef _STATBUF_ST_RDEV

  name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);

#else

  name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);

#endif

  if (!name && dostat != -1)

    {

      dostat = 1;

#ifdef _STATBUF_ST_RDEV

      name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);

#else

      name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);

#endif

    }

  return name;

}