/* Open a pseudoterminal.

   Copyright (C) 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 <support/tty.h>

#include <support/check.h>

#include <support/support.h>

#include <errno.h>

#include <stdlib.h>

#include <string.h>

#include <fcntl.h>

#include <termios.h>

#include <sys/ioctl.h>

#include <unistd.h>

/* As ptsname, but allocates space for an appropriately-sized string

   using malloc.  */

static char *

xptsname (int fd)

{

  int rv;

  size_t buf_len = 128;

  char *buf = xmalloc (buf_len);

  for (;;)

    {

      rv = ptsname_r (fd, buf, buf_len);

      if (rv)

        FAIL_EXIT1 ("ptsname_r: %s", strerror (errno));

      if (memchr (buf, '\0', buf_len))

        return buf; /* ptsname succeeded and the buffer was not truncated */

      buf_len *= 2;

      buf = xrealloc (buf, buf_len);

    }

}

void

support_openpty (int *a_outer, int *a_inner, char **a_name,

                 const struct termios *termp,

                 const struct winsize *winp)

{

  int outer = -1, inner = -1;

  char *namebuf = 0;

  outer = posix_openpt (O_RDWR | O_NOCTTY);

  if (outer == -1)

    FAIL_EXIT1 ("posix_openpt: %s", strerror (errno));

  if (grantpt (outer))

    FAIL_EXIT1 ("grantpt: %s", strerror (errno));

  if (unlockpt (outer))

    FAIL_EXIT1 ("unlockpt: %s", strerror (errno));

#ifdef TIOCGPTPEER

  inner = ioctl (outer, TIOCGPTPEER, O_RDWR | O_NOCTTY);

#endif

  if (inner == -1)

    {

      /* The kernel might not support TIOCGPTPEER, fall back to open

         by name.  */

      namebuf = xptsname (outer);

      inner = open (namebuf, O_RDWR | O_NOCTTY);

      if (inner == -1)

        FAIL_EXIT1 ("%s: %s", namebuf, strerror (errno));

    }

  if (termp)

    {

      if (tcsetattr (inner, TCSAFLUSH, termp))

        FAIL_EXIT1 ("tcsetattr: %s", strerror (errno));

    }

#ifdef TIOCSWINSZ

  if (winp)

    {

      if (ioctl (inner, TIOCSWINSZ, winp))

        FAIL_EXIT1 ("TIOCSWINSZ: %s", strerror (errno));

    }

#endif

  if (a_name)

    {

      if (!namebuf)

        namebuf = xptsname (outer);

      *a_name = namebuf;

    }

  else

    free (namebuf);

  *a_outer = outer;

  *a_inner = inner;

}