Add message bindings

Add C++ bindings for the sd_bus_message_* class functions.  This
binding creates a unique_ptr wrapper around sd_bus_message*, using
the appropriate sd_bus_message deref calls when the unique_ptr leaves
scope.

Change-Id: Ieb8b981a43406332ed3b65bc5326a0f18671d496
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>

1 files changed, 85 insertions, 0 deletions

diff --git a/sdbusplus/message.hpp b/sdbusplus/message.hpp
new file mode 100644
index 0000000..acaa04d
--- /dev/null
+++ b/sdbusplus/message.hpp
@@ -0,0 +1,85 @@
+#pragma once
+
+#include <memory>
+#include <systemd/sd-bus.h>
+#include <sdbusplus/message/append.hpp>
+
+namespace sdbusplus
+{
+
+    // Forward declare sdbusplus::bus::bus for 'friend'ship.
+namespace bus { struct bus; };
+
+namespace message
+{
+
+using msgp_t = sd_bus_message*;
+class message;
+
+namespace details
+{
+
+/** @brief unique_ptr functor to release a msg reference. */
+struct MsgDeleter
+{
+    void operator()(msgp_t ptr) const
+    {
+        sd_bus_message_unref(ptr);
+    }
+};
+
+/* @brief Alias 'msg' to a unique_ptr type for auto-release. */
+using msg = std::unique_ptr<sd_bus_message, MsgDeleter>;
+
+} // namespace details
+
+/** @class message
+ *  @brief Provides C++ bindings to the sd_bus_message_* class functions.
+ */
+struct message
+{
+        /* Define all of the basic class operations:
+         *     Not allowed:
+         *         - Default constructor to avoid nullptrs.
+         *         - Copy operations due to internal unique_ptr.
+         *     Allowed:
+         *         - Move operations.
+         *         - Destructor.
+         */
+    message() = delete;
+    message(const message&) = delete;
+    message& operator=(const message&) = delete;
+    message(message&&) = default;
+    message& operator=(message&&) = default;
+    ~message() = default;
+
+    /** @brief Conversion constructor for 'msgp_t'.
+     *
+     *  Takes ownership of the msg-pointer and releases it when done.
+     */
+    explicit message(msgp_t m) : _msg(m) {}
+
+    /** @brief Release ownership of the stored msg-pointer. */
+    msgp_t release() { return _msg.release(); }
+
+    /** @brief Perform sd_bus_message_append, with automatic type deduction.
+     *
+     *  @tparam ...Args - Type of items to append to message.
+     *  @param[in] args - Items to append to message.
+     */
+    template <typename ...Args> void append(Args&&... args)
+    {
+        sdbusplus::message::append(_msg.get(), std::forward<Args>(args)...);
+    }
+
+    friend struct sdbusplus::bus::bus;
+
+    private:
+        /** @brief Get a pointer to the owned 'msgp_t'. */
+        msgp_t get() { return _msg.get(); }
+        details::msg _msg;
+};
+
+} // namespace message
+
+} // namespace sdbusplus