strtoumax: fix typo in previous commit.

[gnulib.git] / lib / getdtablesize.c

diff --git a/lib/getdtablesize.c b/lib/getdtablesize.c
index a348cdd..355c17e 100644 (file)
--- a/lib/getdtablesize.c
+++ b/lib/getdtablesize.c
@@ -1,5 +1,5 @@
 /* getdtablesize() function for platforms that don't have it.
-   Copyright (C) 2008 Free Software Foundation, Inc.
+   Copyright (C) 2008-2013 Free Software Foundation, Inc.
    Written by Bruno Haible <bruno@clisp.org>, 2008.
 
    This program is free software: you can redistribute it and/or modify
@@ -22,12 +22,86 @@
 
 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
 
-#include <stdio.h>
+# include <stdio.h>
+
+# include "msvc-inval.h"
+
+# 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;
+}
+#  define _setmaxstdio _setmaxstdio_nothrow
+# endif
+
+/* Cache for the previous getdtablesize () result.  Safe to cache because
+   Windows also lacks setrlimit.  */
+static int dtablesize;
 
 int
 getdtablesize (void)
 {
-  return _getmaxstdio ();
+  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;
+}
+
+#elif HAVE_GETDTABLESIZE
+
+# include <sys/resource.h>
+# undef getdtablesize
+
+int
+rpl_getdtablesize(void)
+{
+  /* To date, this replacement is only compiled for Cygwin 1.7.25,
+     which auto-increased the RLIMIT_NOFILE soft limit until it
+     hits the compile-time constant hard limit of 3200.  Although
+     that version of cygwin supported a child process inheriting
+     a smaller soft limit, the smaller limit is not enforced, so
+     we might as well just report the hard limit.  */
+  struct rlimit lim;
+  if (!getrlimit (RLIMIT_NOFILE, &lim) && lim.rlim_max != RLIM_INFINITY)
+    return lim.rlim_max;
+  return getdtablesize ();
 }
 
 #endif