Add support for callbacks

Callbacks are the response in the PDM 'trigger->response' model.
Add general support for implementing callbacks and implement
a log to systemd journal using that framework.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Change-Id: I8bead5368ee5472a02b47e8bba9e9df3a1f346bc

1 files changed, 57 insertions, 0 deletions

diff --git a/src/callback.hpp b/src/callback.hpp
new file mode 100644
index 0000000..d7a678c
--- /dev/null
+++ b/src/callback.hpp
@@ -0,0 +1,57 @@
+#pragma once
+
+#include "data_types.hpp"
+
+namespace phosphor
+{
+namespace dbus
+{
+namespace monitoring
+{
+
+/** @class Callback
+ *  @brief Callback interface.
+ *
+ *  Callbacks of any type can be run.
+ */
+class Callback
+{
+    public:
+        Callback() = default;
+        Callback(const Callback&) = delete;
+        Callback(Callback&&) = default;
+        Callback& operator=(const Callback&) = delete;
+        Callback& operator=(Callback&&) = default;
+        virtual ~Callback() = default;
+
+        /** @brief Run the callback. */
+        virtual void operator()() = 0;
+};
+
+/** @class IndexedCallback
+ *  @brief Callback with an index.
+ */
+class IndexedCallback : public Callback
+{
+    public:
+        IndexedCallback() = delete;
+        IndexedCallback(const IndexedCallback&) = delete;
+        IndexedCallback(IndexedCallback&&) = default;
+        IndexedCallback& operator=(const IndexedCallback&) = delete;
+        IndexedCallback& operator=(IndexedCallback&&) = default;
+        virtual ~IndexedCallback() = default;
+        explicit IndexedCallback(const PropertyIndex& callbackIndex)
+            : Callback(), index(callbackIndex) {}
+
+        /** @brief Run the callback. */
+        virtual void operator()() override = 0;
+
+    protected:
+
+        /** @brief Property names and their associated storage. */
+        const PropertyIndex& index;
+};
+
+} // namespace monitoring
+} // namespace dbus
+} // namespace phosphor