/* 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 <termios.h>

#include <unistd.h>

#include <string.h>

#include <stdlib.h>

#include <_itoa.h>

#include "ttyname.h"

#if 0

/* Is this used anywhere?  It is not exported.  */

char *__ttyname;

#endif

static char *getttyname (const char *dev, const struct stat64 *mytty,

			 int save, int *dostat);

libc_freeres_ptr (static char *getttyname_name);

static char *

attribute_compat_text_section

getttyname (const char *dev, const struct stat64 *mytty, int save, int *dostat)

{

  static size_t namelen;

  struct stat64 st;

  DIR *dirstream;

  struct dirent64 *d;

  size_t devlen = strlen (dev) + 1;

  dirstream = __opendir (dev);

  if (dirstream == NULL)

    {

      *dostat = -1;

      return NULL;

    }

  /* Prepare for the loop.  If we already have a buffer copy the directory

     name we look at into it.  */

  if (devlen < namelen)

    *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';

  while ((d = __readdir64 (dirstream)) != NULL)

    if ((d->d_fileno == mytty->st_ino || *dostat)

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

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

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

      {

	size_t dlen = _D_ALLOC_NAMLEN (d);

	if (devlen + dlen > namelen)

	  {

	    free (getttyname_name);

	    namelen = 2 * (devlen + 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, devlen - 1)) = '/';

	  }

	memcpy (&getttyname_name[devlen], d->d_name, dlen);

	if (__xstat64 (_STAT_VER, getttyname_name, &st) == 0

	    && is_mytty (mytty, &st))

	  {

	    (void) __closedir (dirstream);

#if 0

	    __ttyname = getttyname_name;

#endif

	    __set_errno (save);

	    return getttyname_name;

	  }

      }

  (void) __closedir (dirstream);

  __set_errno (save);

  return NULL;

}

/* Static buffer in `ttyname'.  */

libc_freeres_ptr (static char *ttyname_buf);

/* 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)

{

  static size_t buflen;

  char procname[30];

  struct stat64 st, st1;

  int dostat = 0;

  int doispty = 0;

  char *name;

  int save = errno;

  struct termios term;

  /* isatty check, tcgetattr is used because it sets the correct

     errno (EBADF resp. ENOTTY) on error.  */

  if (__glibc_unlikely (__tcgetattr (fd, &term) < 0))

    return NULL;

  if (__fxstat64 (_STAT_VER, fd, &st) < 0)

    return NULL;

  /* We try using the /proc filesystem.  */

  *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0';

  if (buflen == 0)

    {

      buflen = 4095;

      ttyname_buf = (char *) malloc (buflen + 1);

      if (ttyname_buf == NULL)

	{

	  buflen = 0;

	  return NULL;

	}

    }

  ssize_t len = __readlink (procname, ttyname_buf, buflen);

  if (__glibc_likely (len != -1))

    {

      if ((size_t) len >= buflen)

	return NULL;

#define UNREACHABLE_LEN strlen ("(unreachable)")

      if (len > UNREACHABLE_LEN

	  && memcmp (ttyname_buf, "(unreachable)", UNREACHABLE_LEN) == 0)

	{

	  memmove (ttyname_buf, ttyname_buf + UNREACHABLE_LEN,

		   len - UNREACHABLE_LEN);

	  len -= UNREACHABLE_LEN;

	}

      /* readlink need not terminate the string.  */

      ttyname_buf[len] = '\0';

      /* Verify readlink result, fall back on iterating through devices.  */

      if (ttyname_buf[0] == '/'

	  && __xstat64 (_STAT_VER, ttyname_buf, &st1) == 0

	  && is_mytty (&st, &st1))

	return ttyname_buf;

      doispty = 1;

    }

  if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))

    {

      name = getttyname ("/dev/pts", &st, save, &dostat);

    }

  else

    {

      __set_errno (save);

      name = NULL;

    }

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

    {

      name = getttyname ("/dev", &st, save, &dostat);

    }

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

    {

      dostat = 1;

      name = getttyname ("/dev", &st, save, &dostat);

    }

  if (!name && doispty && is_pty (&st))

    {

      /* We failed to figure out the TTY's name, but we can at least

         signal that we did verify that it really is a PTY slave.

         This happens when we have inherited the file descriptor from

         a different mount namespace.  */

      __set_errno (ENODEV);

      return NULL;

    }

  return name;

}