Add sdevent C++ wrappers

Add C++ wrappers around select sd-event APIs, for a more C++ like
programming API.

Includes support for core sd_event and timer related sd_event_source
APIs.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Change-Id: I10ac5406c9f8831b4efb294d3aef36026469d4a5

1 files changed, 139 insertions, 0 deletions

diff --git a/src/sdevent/timer.hpp b/src/sdevent/timer.hpp
new file mode 100644
index 0000000..863e725
--- /dev/null
+++ b/src/sdevent/timer.hpp
@@ -0,0 +1,139 @@
+#pragma once
+
+#include <chrono>
+#include <functional>
+#include <memory>
+#include <systemd/sd-event.h>
+
+#include "sdevent/source.hpp"
+#include "sdevent/event.hpp"
+
+// TODO: openbmc/openbmc#1720 - add error handling for sd_event API failures
+
+namespace sdevent
+{
+namespace event
+{
+namespace timer
+{
+
+/** @class Timer
+ *  @brief Provides C++ bindings to the sd_event_source* timer functions.
+ */
+class Timer
+{
+    public:
+        /* 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.
+         */
+        Timer() = delete;
+        Timer(const Timer&) = delete;
+        Timer& operator=(const Timer&) = delete;
+        Timer(Timer&&) = default;
+        Timer& operator=(Timer&&) = default;
+        ~Timer() = default;
+
+        using Callback = std::function<void(source::Source&)>;
+
+        /** @brief Register a timer callback.
+         *
+         *  @param[in] event - The event to register on.
+         *  @param[in] expires - The initial timer expiration time.
+         *  @param[in] callback - The callback method.
+         */
+        Timer(
+            sdevent::event::Event& event,
+            const std::chrono::steady_clock::time_point& expires,
+            Callback callback)
+            : src(nullptr),
+              cb(std::make_unique<Callback>(std::move(callback)))
+        {
+            using namespace std::chrono;
+            auto epoch = expires.time_since_epoch();
+            auto time = duration_cast<microseconds>(epoch);
+            sd_event_source* source = nullptr;
+            sd_event_add_time(
+                event.get(),
+                &source,
+                CLOCK_MONOTONIC,
+                time.count(),
+                0,
+                callCallback,
+                cb.get());
+// **INDENT-OFF**
+            src = decltype(src){source, std::false_type()};
+// **INDENT-ON**
+        }
+
+        /** @brief Register a disabled timer callback.
+         *
+         *  @param[in] event - The event to register on.
+         *  @param[in] callback - The callback method.
+         */
+        Timer(
+            sdevent::event::Event& event,
+            Callback callback)
+            : src(nullptr),
+              cb(std::make_unique<Callback>(std::move(callback)))
+        {
+            sd_event_source* source = nullptr;
+            sd_event_add_time(
+                event.get(),
+                &source,
+                CLOCK_MONOTONIC,
+                ULLONG_MAX,
+                0,
+                callCallback,
+                cb.get());
+// **INDENT-OFF**
+            src = decltype(src){source, std::false_type()};
+// **INDENT-ON**
+        }
+
+        /** @brief Set the timer expiration time. */
+        void setTime(
+            const std::chrono::steady_clock::time_point& expires)
+        {
+            src.setTime(expires);
+        }
+
+        /** @brief Get the timer expiration time. */
+        auto getTime()
+        {
+            return src.getTime();
+        }
+
+        /** @brief Set the timer source enable state. */
+        void enable(int enable)
+        {
+            src.enable(enable);
+        }
+
+        /** @brief Query timer state. */
+        auto enabled()
+        {
+            return src.enabled();
+        }
+
+    private:
+        source::Source src;
+        std::unique_ptr<Callback> cb = nullptr;
+
+        static int callCallback(sd_event_source* s, uint64_t usec,
+                                void* context)
+        {
+            source::Source source(s);
+            auto c = static_cast<Callback*>(context);
+            (*c)(source);
+
+            return 0;
+        }
+};
+} // namespace timer
+} // namespace event
+} // namespace sdevent