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5e8754f9 SDJ |
1 | /* getdtablesize() function for platforms that don't have it. |
2 | Copyright (C) 2008-2016 Free Software Foundation, Inc. | |
6ec2e0f5 SDJ |
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 | |
5e8754f9 | 16 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
6ec2e0f5 SDJ |
17 | |
18 | #include <config.h> | |
19 | ||
20 | /* Specification. */ | |
21 | #include <unistd.h> | |
22 | ||
5e8754f9 | 23 | #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__ |
6ec2e0f5 SDJ |
24 | |
25 | # include <stdio.h> | |
26 | ||
5e8754f9 | 27 | # include "msvc-inval.h" |
6ec2e0f5 SDJ |
28 | |
29 | # if HAVE_MSVC_INVALID_PARAMETER_HANDLER | |
30 | static 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 | } | |
5e8754f9 | 47 | # define _setmaxstdio _setmaxstdio_nothrow |
6ec2e0f5 SDJ |
48 | # endif |
49 | ||
50 | /* Cache for the previous getdtablesize () result. Safe to cache because | |
51 | Windows also lacks setrlimit. */ | |
52 | static int dtablesize; | |
53 | ||
54 | int | |
55 | getdtablesize (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; | |
5e8754f9 | 79 | for (bound = 0x10000; _setmaxstdio (bound) < 0; bound = bound / 2) |
6ec2e0f5 | 80 | ; |
5e8754f9 | 81 | _setmaxstdio (orig_max_stdio); |
6ec2e0f5 SDJ |
82 | dtablesize = bound; |
83 | } | |
84 | return dtablesize; | |
85 | } | |
86 | ||
87 | #else | |
88 | ||
89 | # include <limits.h> | |
90 | # include <sys/resource.h> | |
91 | ||
92 | # ifndef RLIM_SAVED_CUR | |
93 | # define RLIM_SAVED_CUR RLIM_INFINITY | |
94 | # endif | |
95 | # ifndef RLIM_SAVED_MAX | |
96 | # define RLIM_SAVED_MAX RLIM_INFINITY | |
97 | # endif | |
98 | ||
99 | # ifdef __CYGWIN__ | |
100 | /* Cygwin 1.7.25 auto-increases the RLIMIT_NOFILE soft limit until it | |
101 | hits the compile-time constant hard limit of 3200. We might as | |
102 | well just report the hard limit. */ | |
103 | # define rlim_cur rlim_max | |
104 | # endif | |
105 | ||
106 | int | |
107 | getdtablesize (void) | |
108 | { | |
109 | struct rlimit lim; | |
110 | ||
111 | if (getrlimit (RLIMIT_NOFILE, &lim) == 0 | |
112 | && 0 <= lim.rlim_cur && lim.rlim_cur <= INT_MAX | |
113 | && lim.rlim_cur != RLIM_INFINITY | |
114 | && lim.rlim_cur != RLIM_SAVED_CUR | |
115 | && lim.rlim_cur != RLIM_SAVED_MAX) | |
116 | return lim.rlim_cur; | |
117 | ||
118 | return INT_MAX; | |
119 | } | |
120 | ||
121 | #endif |