/* getdtablesize() function: Return maximum possible file descriptor value + 1.

   Copyright (C) 2008-2020 Free Software Foundation, Inc.

   Written by Bruno Haible <bruno@clisp.org>, 2008.

   This program 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.

   This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include <unistd.h>

#if defined _WIN32 && ! defined __CYGWIN__

# include <stdio.h>

# if HAVE_MSVC_INVALID_PARAMETER_HANDLER

#  include "msvc-inval.h"

# endif

# if HAVE_MSVC_INVALID_PARAMETER_HANDLER

static int

_setmaxstdio_nothrow (int newmax)

{

  int result;

  TRY_MSVC_INVAL

    {

      result = _setmaxstdio (newmax);

    }

  CATCH_MSVC_INVAL

    {

      result = -1;

    }

  DONE_MSVC_INVAL;

  return result;

}

# else

#  define _setmaxstdio_nothrow _setmaxstdio

# endif

/* Cache for the previous getdtablesize () result.  Safe to cache because

   Windows also lacks setrlimit.  */

static int dtablesize;

int

getdtablesize (void)

{

  if (dtablesize == 0)

    {

      /* We are looking for the number N such that the valid file descriptors

         are 0..N-1.  It can be obtained through a loop as follows:

           {

             int fd;

             for (fd = 3; fd < 65536; fd++)

               if (dup2 (0, fd) == -1)

                 break;

             return fd;

           }

         On Windows XP, the result is 2048.

         The drawback of this loop is that it allocates memory for a libc

         internal array that is never freed.

         The number N can also be obtained as the upper bound for

         _getmaxstdio ().  _getmaxstdio () returns the maximum number of open

         FILE objects.  The sanity check in _setmaxstdio reveals the maximum

         number of file descriptors.  This too allocates memory, but it is

         freed when we call _setmaxstdio with the original value.  */

      int orig_max_stdio = _getmaxstdio ();

      unsigned int bound;

      for (bound = 0x10000; _setmaxstdio_nothrow (bound) < 0; bound = bound / 2)

        ;

      _setmaxstdio_nothrow (orig_max_stdio);

      dtablesize = bound;

    }

  return dtablesize;

}

#else

# include <limits.h>

# include <sys/resource.h>

# ifndef RLIM_SAVED_CUR

#  define RLIM_SAVED_CUR RLIM_INFINITY

# endif

# ifndef RLIM_SAVED_MAX

#  define RLIM_SAVED_MAX RLIM_INFINITY

# endif

# ifdef __CYGWIN__

  /* Cygwin 1.7.25 auto-increases the RLIMIT_NOFILE soft limit until it

     hits the compile-time constant hard limit of 3200.  We might as

     well just report the hard limit.  */

#  define rlim_cur rlim_max

# endif

int

getdtablesize (void)

{

  struct rlimit lim;

  if (getrlimit (RLIMIT_NOFILE, &lim) == 0

      && 0 <= lim.rlim_cur && lim.rlim_cur <= INT_MAX

      && lim.rlim_cur != RLIM_INFINITY

      && lim.rlim_cur != RLIM_SAVED_CUR

      && lim.rlim_cur != RLIM_SAVED_MAX)

    return lim.rlim_cur;

  return INT_MAX;

}

#endif