From 74da141e618ef99959d509cb2e7be35a348a39db Mon Sep 17 00:00:00 2001 From: Thomas Guyot-Sionnest Date: Wed, 7 Apr 2010 21:11:46 -0400 Subject: Sync with the latest Gnulib code (177f525) Signed-off-by: Thomas Guyot-Sionnest --- gl/getdtablesize.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 gl/getdtablesize.c (limited to 'gl/getdtablesize.c') diff --git a/gl/getdtablesize.c b/gl/getdtablesize.c new file mode 100644 index 00000000..a565a2de --- /dev/null +++ b/gl/getdtablesize.c @@ -0,0 +1,63 @@ +/* getdtablesize() function for platforms that don't have it. + Copyright (C) 2008-2010 Free Software Foundation, Inc. + Written by Bruno Haible , 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 . */ + +#include + +/* Specification. */ +#include + +#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__ + +#include + +/* Cache for the previous getdtablesize () result. */ +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 (bound) < 0; bound = bound / 2) + ; + _setmaxstdio (orig_max_stdio); + dtablesize = bound; + } + return dtablesize; +} + +#endif -- cgit v1.2.3-74-g34f1