1 files changed, 23 insertions, 0 deletions
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 1fd89f3a55bf..33b06ca955df 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -303,6 +303,29 @@ bool hasSuffix(const string & s, const string & suffix);
 void ignoreException();
 
 
+/* STL functions such as sort() pass a binary function object around
+   by value, so it gets cloned a lot.  This is bad if the function
+   object has state or is simply large.  This adapter wraps the
+   function object to simulate passing by reference. */
+template<class F>
+struct binary_function_ref_adapter
+{
+    F * p;
+
+    binary_function_ref_adapter(F * _p)
+    {
+        p = _p;
+    }
+    
+    typename F::result_type operator () (
+        const typename F::first_argument_type & x,
+        const typename F::second_argument_type & y)
+    {
+        return (*p)(x, y);
+    }
+};
+
+
 }