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+/**
+ * \file
+ * \brief RoundRobinQuantum class header
+ *
+ * \author Copyright (C) 2014-2016 Kamil Szczygiel http://www.distortec.com http://www.freddiechopin.info
+ *
+ * \par License
+ * This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not
+ * distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDE_DISTORTOS_INTERNAL_SCHEDULER_ROUNDROBINQUANTUM_HPP_
+#define INCLUDE_DISTORTOS_INTERNAL_SCHEDULER_ROUNDROBINQUANTUM_HPP_
+
+#include "distortos/TickClock.hpp"
+
+namespace distortos
+{
+
+namespace internal
+{
+
+/// RoundRobinQuantum class is a quantum of time for round-robin scheduling
+class RoundRobinQuantum
+{
+public:
+
+	/// type of quantum counter
+	using Representation = uint8_t;
+
+	/// duration type used for quantum
+	using Duration = std::chrono::duration<Representation, TickClock::period>;
+
+	/**
+	 * \return initial value for round-robin quantum
+	 */
+
+	constexpr static Duration getInitial()
+	{
+		return Duration{quantumRawInitializer_};
+	}
+
+	/**
+	 * \brief RoundRobinQuantum's constructor
+	 *
+	 * Initializes quantum value to initial value - just like after call to reset().
+	 */
+
+	constexpr RoundRobinQuantum() :
+			quantum_{getInitial()}
+	{
+
+	}
+
+	/**
+	 * \brief Decrements round-robin's quantum.
+	 *
+	 * This function should be called from tick interrupt for the currently running thread. Underflow of quantum after
+	 * this decrement is not possible.
+	 *
+	 * \note this function must be called with enabled interrupt masking
+	 */
+
+	void decrement()
+	{
+		if (isZero() == false)
+			--quantum_;
+	}
+
+	/**
+	 * \brief Gets current value of round-robin's quantum.
+	 *
+	 * \return current value of round-robin's quantum of the thread
+	 */
+
+	Duration get() const
+	{
+		return quantum_;
+	}
+
+	/**
+	 * \brief Convenience function to test whether the quantum is already at 0.
+	 *
+	 * \return true if quantum is zero, false otherwise
+	 */
+
+	bool isZero() const
+	{
+		return quantum_ == Duration{0};
+	}
+
+	/**
+	 * \brief Resets value of round-robin's quantum.
+	 *
+	 * This function should be called from context switcher after selecting new task that will be run.
+	 */
+
+	void reset()
+	{
+		quantum_ = getInitial();
+	}
+
+private:
+
+	static_assert(CONFIG_TICK_FREQUENCY > 0, "CONFIG_TICK_FREQUENCY must be positive and non-zero!");
+	static_assert(CONFIG_ROUND_ROBIN_FREQUENCY > 0, "CONFIG_ROUND_ROBIN_FREQUENCY must be positive and non-zero!");
+
+	/// raw initializer value for round-robin quantum, calculated with rounding to nearest
+	constexpr static auto quantumRawInitializer_ = (CONFIG_TICK_FREQUENCY + CONFIG_ROUND_ROBIN_FREQUENCY / 2) /
+			CONFIG_ROUND_ROBIN_FREQUENCY;
+
+	static_assert(quantumRawInitializer_ > 0 || quantumRawInitializer_ <= UINT8_MAX,
+			"CONFIG_TICK_FREQUENCY and CONFIG_ROUND_ROBIN_FREQUENCY values produce invalid round-robin quantum!");
+
+	/// round-robin quantum
+	Duration quantum_;
+};
+
+}	// namespace internal
+
+}	// namespace distortos
+
+#endif	// INCLUDE_DISTORTOS_INTERNAL_SCHEDULER_ROUNDROBINQUANTUM_HPP_