1 files changed, 71 insertions, 0 deletions
diff --git a/lib/timespec-sub.c b/lib/timespec-sub.c
new file mode 100644
index 0000000000..7c4c781b7f
--- /dev/null
+++ b/lib/timespec-sub.c
@@ -0,0 +1,71 @@
+/* Subtract two struct timespec values.
+
+   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.  */
+
+/* Return the difference between two timespec values A and B.  On
+   overflow, return an extremal value.  This assumes 0 <= tv_nsec <=
+   999999999.  */
+
+#include <config.h>
+#include "timespec.h"
+
+#include "intprops.h"
+
+struct timespec
+timespec_sub (struct timespec a, struct timespec b)
+{
+  struct timespec r;
+  time_t rs = a.tv_sec;
+  time_t bs = b.tv_sec;
+  int ns = a.tv_nsec - b.tv_nsec;
+  int rns = ns;
+
+  if (ns < 0)
+    {
+      rns = ns + 1000000000;
+      if (rs == TYPE_MINIMUM (time_t))
+        {
+          if (bs <= 0)
+            goto low_overflow;
+          bs--;
+        }
+      else
+        rs--;
+    }
+
+  if (INT_SUBTRACT_OVERFLOW (rs, bs))
+    {
+      if (rs < 0)
+        {
+        low_overflow:
+          rs = TYPE_MINIMUM (time_t);
+          rns = 0;
+        }
+      else
+        {
+          rs = TYPE_MAXIMUM (time_t);
+          rns = 999999999;
+        }
+    }
+  else
+    rs -= bs;
+
+  r.tv_sec = rs;
+  r.tv_nsec = rns;
+  return r;
+}