avoid recursive `require' when loading semantic
[bpt/emacs.git] / lib / getdtablesize.c
CommitLineData
067428c1 1/* getdtablesize() function for platforms that don't have it.
ba318903 2 Copyright (C) 2008-2014 Free Software Foundation, Inc.
067428c1
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3 Written by Bruno Haible <bruno@clisp.org>, 2008.
4
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
17
18#include <config.h>
19
20/* Specification. */
21#include <unistd.h>
22
23#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
24
0a858ebf 25# include <stdio.h>
067428c1 26
0a858ebf 27# include "msvc-inval.h"
067428c1 28
0a858ebf 29# if HAVE_MSVC_INVALID_PARAMETER_HANDLER
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30static int
31_setmaxstdio_nothrow (int newmax)
32{
33 int result;
34
35 TRY_MSVC_INVAL
36 {
37 result = _setmaxstdio (newmax);
38 }
39 CATCH_MSVC_INVAL
40 {
41 result = -1;
42 }
43 DONE_MSVC_INVAL;
44
45 return result;
46}
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47# define _setmaxstdio _setmaxstdio_nothrow
48# endif
067428c1 49
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50/* Cache for the previous getdtablesize () result. Safe to cache because
51 Windows also lacks setrlimit. */
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52static int dtablesize;
53
54int
55getdtablesize (void)
56{
57 if (dtablesize == 0)
58 {
59 /* We are looking for the number N such that the valid file descriptors
60 are 0..N-1. It can be obtained through a loop as follows:
61 {
62 int fd;
63 for (fd = 3; fd < 65536; fd++)
64 if (dup2 (0, fd) == -1)
65 break;
66 return fd;
67 }
68 On Windows XP, the result is 2048.
69 The drawback of this loop is that it allocates memory for a libc
70 internal array that is never freed.
71
72 The number N can also be obtained as the upper bound for
73 _getmaxstdio (). _getmaxstdio () returns the maximum number of open
74 FILE objects. The sanity check in _setmaxstdio reveals the maximum
75 number of file descriptors. This too allocates memory, but it is
76 freed when we call _setmaxstdio with the original value. */
77 int orig_max_stdio = _getmaxstdio ();
78 unsigned int bound;
79 for (bound = 0x10000; _setmaxstdio (bound) < 0; bound = bound / 2)
80 ;
81 _setmaxstdio (orig_max_stdio);
82 dtablesize = bound;
83 }
84 return dtablesize;
85}
86
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87#elif HAVE_GETDTABLESIZE
88
89# include <sys/resource.h>
90# undef getdtablesize
91
92int
93rpl_getdtablesize(void)
94{
95 /* To date, this replacement is only compiled for Cygwin 1.7.25,
96 which auto-increased the RLIMIT_NOFILE soft limit until it
97 hits the compile-time constant hard limit of 3200. Although
98 that version of cygwin supported a child process inheriting
99 a smaller soft limit, the smaller limit is not enforced, so
100 we might as well just report the hard limit. */
101 struct rlimit lim;
102 if (!getrlimit (RLIMIT_NOFILE, &lim) && lim.rlim_max != RLIM_INFINITY)
103 return lim.rlim_max;
104 return getdtablesize ();
105}
106
067428c1 107#endif