memory: add object based deleter for unique_ptr

Makefile.am

@@ -179,6 +179,8 @@ UTIL_FILES   =			\
     memory/buffer/circular.hpp	\
     memory/buffer/paged.cpp	\
     memory/buffer/paged.hpp	\
+    memory/deleter.cpp		\
+    memory/deleter.hpp		\
     memory/system.cpp		\
     memory/system.hpp		\
     net/address.cpp		\

memory/deleter.cpp

@@ -0,0 +1,32 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "./deleter.hpp"
+
+using util::memory::object_deleter;
+
+
+///////////////////////////////////////////////////////////////////////////////
+// This instantiation isn't required but it allows us to catch compilation
+// errors early within this library rather than at a call site in another
+// library.
+
+class owner {
+    void dealloc (void*);
+};
+
+
+template class util::memory::object_deleter<void,owner,&owner::dealloc>;

memory/deleter.hpp

@@ -0,0 +1,40 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_MEMORY_DELETER_HPP
+#define __UTIL_MEMORY_DELETER_HPP
+
+namespace util { namespace memory {
+    template <typename T, typename U, void (U::*F)(T*)>
+    class object_deleter {
+    public:
+        static_assert (F != nullptr, "destroy function must be non-null");
+
+        object_deleter (U &owner):
+            m_owner (owner)
+        { ; }
+
+        void operator() (T *t)
+        {
+            (m_owner.*F) (t);
+        }
+
+    private:
+        U& m_owner;
+    };
+} }
+
+#endif