/* 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"

static int getttyname_r (char *buf, size_t buflen,

			 const struct stat64 *mytty, int save,

			 int *dostat);

static int

attribute_compat_text_section

getttyname_r (char *buf, size_t buflen, const struct stat64 *mytty,

	      int save, int *dostat)

{

  struct stat64 st;

  DIR *dirstream;

  struct dirent64 *d;

  size_t devlen = strlen (buf);

  dirstream = __opendir (buf);

  if (dirstream == NULL)

    {

      *dostat = -1;

      return errno;

    }

  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"))

      {

	char *cp;

	size_t needed = _D_EXACT_NAMLEN (d) + 1;

	if (needed > buflen)

	  {

	    *dostat = -1;

	    (void) __closedir (dirstream);

	    __set_errno (ERANGE);

	    return ERANGE;

	  }

	cp = __stpncpy (buf + devlen, d->d_name, needed);

	cp[0] = '\0';

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

	    && is_mytty (mytty, &st))

	  {

	    (void) __closedir (dirstream);

	    __set_errno (save);

	    return 0;

	  }

      }

  (void) __closedir (dirstream);

  __set_errno (save);

  /* It is not clear what to return in this case.  `isatty' says FD

     refers to a TTY but no entry in /dev has this inode.  */

  return ENOTTY;

}

/* Store at most BUFLEN character of the pathname of the terminal FD is

   open on in BUF.  Return 0 on success,  otherwise an error number.  */

int

__ttyname_r (int fd, char *buf, size_t buflen)

{

  char procname[30];

  struct stat64 st, st1;

  int dostat = 0;

  int doispty = 0;

  int save = errno;

  /* Test for the absolute minimal size.  This makes life easier inside

     the loop.  */

  if (!buf)

    {

      __set_errno (EINVAL);

      return EINVAL;

    }

  if (buflen < sizeof ("/dev/pts/"))

    {

      __set_errno (ERANGE);

      return ERANGE;

    }

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

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

  struct termios term;

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

    return errno;

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

    return errno;

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

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

  ssize_t ret = __readlink (procname, buf, buflen - 1);

  if (__glibc_unlikely (ret == -1 && errno == ENAMETOOLONG))

    {

      __set_errno (ERANGE);

      return ERANGE;

    }

  if (__glibc_likely (ret != -1))

    {

#define UNREACHABLE_LEN strlen ("(unreachable)")

      if (ret > UNREACHABLE_LEN

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

	{

	  memmove (buf, buf + UNREACHABLE_LEN, ret - UNREACHABLE_LEN);

	  ret -= UNREACHABLE_LEN;

	}

      /* readlink need not terminate the string.  */

      buf[ret] = '\0';

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

      if (buf[0] == '/'

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

	  && is_mytty (&st, &st1))

	return 0;

      doispty = 1;

    }

  /* Prepare the result buffer.  */

  memcpy (buf, "/dev/pts/", sizeof ("/dev/pts/"));

  buflen -= sizeof ("/dev/pts/") - 1;

  if (__xstat64 (_STAT_VER, buf, &st1) == 0 && S_ISDIR (st1.st_mode))

    {

      ret = getttyname_r (buf, buflen, &st, save,

			  &dostat);

    }

  else

    {

      __set_errno (save);

      ret = ENOENT;

    }

  if (ret && dostat != -1)

    {

      buf[sizeof ("/dev/") - 1] = '\0';

      buflen += sizeof ("pts/") - 1;

      ret = getttyname_r (buf, buflen, &st, save,

			  &dostat);

    }

  if (ret && dostat != -1)

    {

      buf[sizeof ("/dev/") - 1] = '\0';

      dostat = 1;

      ret = getttyname_r (buf, buflen, &st,

			  save, &dostat);

    }

  if (ret && 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 ENODEV;

    }

  return ret;

}

weak_alias (__ttyname_r, ttyname_r)