refs #321 token bucket algorithm implementation

src/blackcore/token_bucket.cpp

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+/* Copyright (C) 2014
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#include "token_bucket.h"
+
+namespace BlackCore
+{
+    bool CTokenBucket::tryConsume(int numTokens)
+    {
+        Q_ASSERT(numTokens > 0 && numTokens < m_capacity);
+
+        // Replenish maximal up to capacity
+        int replenishedTokens = qMin(m_capacity, getTokens());
+
+        // Take care of overflows
+        m_availableTokens = qMin(m_availableTokens + replenishedTokens, m_capacity);
+
+        if (numTokens <= m_availableTokens)
+        {
+            m_availableTokens -= numTokens;
+            return true;
+        }
+
+        return false;
+    }
+
+    int CTokenBucket::getTokens()
+    {
+        auto now = QDateTime::currentDateTime();
+        auto deltaSeconds = m_lastReplenishmentTime.secsTo(now);
+        int numberOfTokens = static_cast<int>( m_numTokensToRefill * deltaSeconds / m_interval.value(BlackMisc::PhysicalQuantities::CTimeUnit::s()));
+
+        // Update the time only when replenishment actually took place. We will end up in a infinite loop otherwise.
+        if (numberOfTokens > 0 ) m_lastReplenishmentTime = now;
+        return numberOfTokens;
+    }
+
+} // namespace

src/blackcore/token_bucket.h

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+/* Copyright (C) 2014
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#ifndef BLACKCORE_TOKENBUCKET_H
+#define BLACKCORE_TOKENBUCKET_H
+
+#include "blackmisc/pqtime.h"
+#include <QtGlobal>
+#include <QDateTime>
+
+namespace BlackCore
+{
+    /*!
+     * Token bucket algorithm
+     *
+     * This class implements the token bucket algorithm. Tokens as arbitrary unit are added to the bucket at a defined rate.
+     * Token can be consumsed as long as there are enough available. This class can be used to throttle traffic and packet
+     * generation. Each time a packet needs to be generated and sent a token is consumed. If no token is available, consumption
+     * will fail the the packet cannot be sent.
+     */
+    class CTokenBucket
+    {
+
+    public:
+
+        //! Constructor
+        //! \tparam Replenishment policy
+        CTokenBucket(int capacity, BlackMisc::PhysicalQuantities::CTime interval, int numTokensToRefill)
+            : m_capacity(capacity), m_interval(interval), m_numTokensToRefill(numTokensToRefill) {}
+
+        //! Try to consume a token
+        bool tryConsume()
+        {
+            return tryConsume(1);
+        }
+
+        //! Try to consume a number of tokens
+        bool tryConsume(int numTokens);
+
+    private:
+
+        //! Get available tokens since last replenishment.
+        // Note that replenishment is implemented lazy. This means, tokens will not replenished
+        // on regular basis via a running timer, but they will be replenished while trying to consume
+        // them.
+        int getTokens();
+
+        int m_capacity = 10;                    //!< Maximum capacity of tokens
+        int m_availableTokens = 10;             //!< Currently available tokens. The initial value is 10
+        BlackMisc::PhysicalQuantities::CTime m_interval;            //!< Refill interval, e.g. every 5 secs
+        int m_numTokensToRefill;                                    //!< Number of tokens to be refilled each interval
+        QDateTime m_lastReplenishmentTime = QDateTime::currentDateTime();  //!< Last time
+    };
+}
+
+#endif