debug: add timer

Adds a Timer object to easily benchmark code.

Should be used only for debugging code, so a warning is issued if the
header is included.

Change-Id: I89bc5454fc0c182a50b14cafd205ee116b4a167e

src/debug_utils.h

+/*
+ *  Copyright (C) 2018 Savoir-faire Linux Inc.
+ *
+ *  Author: Philippe Gorley <philippe.gorley@savoirfairelinux.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA.
+ */
+
+#pragma once
+
+#include "config.h"
+
+#include <chrono>
+#include <ratio>
+
+#warning Debug utilities included in build
+
+using Clock = std::chrono::steady_clock;
+
+namespace ring { namespace debug {
+
+/**
+ * Ex:
+ * Timer t;
+ * std::this_thread::sleep_for(std::chrono::milliseconds(10));
+ * RING_DBG() << "Task took " << t.getDuration<std::chrono::nanoseconds>() << " ns";
+ */
+class Timer
+{
+public:
+    Timer() { start_ = Clock::now(); }
+
+    template<class Period = std::ratio<1>>
+    uint64_t getDuration()
+    {
+        auto diff = std::chrono::duration_cast<Period>(Clock::now() - start_);
+        return diff.count();
+    }
+
+private:
+    std::chrono::time_point<Clock> start_;
+};
+
+}} // namespace ring::debug