Add gnulib files to support higher-resolution time stamps.

[bpt/emacs.git] / lib / dtotimespec.c

diff --git a/lib/dtotimespec.c b/lib/dtotimespec.c
new file mode 100644 (file)
index 0000000..f30fa07
--- /dev/null
+++ b/lib/dtotimespec.c
@@ -0,0 +1,69 @@
+/* Convert double to timespec.
+
+   Copyright (C) 2011-2012 Free Software Foundation, Inc.
+
+   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 <http://www.gnu.org/licenses/>.  */
+
+/* written by Paul Eggert */
+
+/* Convert the double value SEC to a struct timespec.  Round toward
+   positive infinity.  On overflow, return an extremal value.  */
+
+#include <config.h>
+
+#include "timespec.h"
+
+#include "intprops.h"
+
+struct timespec
+dtotimespec (double sec)
+{
+  enum { BILLION = 1000 * 1000 * 1000 };
+  double min_representable = TYPE_MINIMUM (time_t);
+  double max_representable =
+    ((TYPE_MAXIMUM (time_t) * (double) BILLION + (BILLION - 1))
+     / BILLION);
+  struct timespec r;
+
+  if (! (min_representable < sec))
+    {
+      r.tv_sec = TYPE_MINIMUM (time_t);
+      r.tv_nsec = 0;
+    }
+  else if (! (sec < max_representable))
+    {
+      r.tv_sec = TYPE_MAXIMUM (time_t);
+      r.tv_nsec = BILLION - 1;
+    }
+  else
+    {
+      time_t s = sec;
+      double frac = BILLION * (sec - s);
+      long ns = frac;
+      ns += ns < frac;
+      s += ns / BILLION;
+      ns %= BILLION;
+
+      if (ns < 0)
+        {
+          s--;
+          ns += BILLION;
+        }
+
+      r.tv_sec = s;
+      r.tv_nsec = ns;
+    }
+
+  return r;
+}