Throttler.h

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/*
* Copyright Onix Solutions Limited [OnixS]. All rights reserved.
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* and international copyright treaties.
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#pragma once

#include <cstddef>

#include <OnixS/FIXEngine/ABI.h>

namespace OnixS {
namespace FIX {

/// The throttler class to perform the throttling.
class ONIXS_FIXENGINE_API Throttler
{
public:

    /// The constructor.
    ///
    /// @param messagesCount The message limit per time unit.
    /// @param intervalInMs The time interval to limit messages.
    Throttler(size_t messagesCount, size_t intervalInMs = 1000);

    /// The destructor.
    ~Throttler();

    /// Performs the throttling. This method must be called before each action that should be throttled.
    /// If the count of messages per time unit exceeds the throttling limit, the function will be blocked until the given time interval is passed.
    void throttle();

    /// Checks the throttling. This method must be called before each action that should be throttled.
    /// If the count of messages per time unit exceeds the throttling limit, the function returns the delay (in milliseconds) until the action becomes possible. Otherwise, it returns 0.
    ///
    /// @param resetWhenDelay The flag indicates if the calculation of messages per throttling interval should be reset and started again when a delay is returned.
    size_t tryThrottle(bool resetWhenDelay = false);

    /// Resets the throttling parameters.
    ///
    /// @param messagesCount The message limit per time unit.
    /// @param intervalInMs The time interval to limit messages.
    void reset(size_t messagesCount, size_t intervalInMs = 1000);

private:

    Throttler(const Throttler &);
    Throttler & operator = (const Throttler &);

    class Impl;
    Impl * const impl_;
};

}
}