mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-11-23 07:19:15 +00:00
125 lines
3.3 KiB
C
125 lines
3.3 KiB
C
/* 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 General Public License as published by
|
|
the Free Software Foundation; either version 3 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 General Public License for more details.
|
|
|
|
You should have received a copy of the GNU 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
|