ClickHouse/base/poco/Foundation/include/Poco/Activity.h

//
// Activity.h
//
// Library: Foundation
// Package: Threading
// Module:  ActiveObjects
//
// Definition of the Activity template class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_Activity_INCLUDED
#define Foundation_Activity_INCLUDED


#include "Poco/Event.h"
#include "Poco/Foundation.h"
#include "Poco/Mutex.h"
#include "Poco/RunnableAdapter.h"
#include "Poco/ThreadPool.h"


namespace Poco
{


template <class C>
class Activity : public Runnable
/// This template class helps to implement active objects.
/// An active object uses threads to decouple method
/// execution from method invocation, or to perform tasks
/// autonomously, without intervention of a caller.
///
/// An activity is a (typically longer running) method
/// that executes within its own task. Activities can
/// be started automatically (upon object construction)
/// or manually at a later time. Activities can also
/// be stopped at any time. However, to make stopping
/// an activity work, the method implementing the
/// activity has to check periodically whether it
/// has been requested to stop, and if so, return.
/// Activities are stopped before the object they belong to is
/// destroyed. Methods implementing activities cannot have arguments
/// or return values.
///
/// Activity objects are used as follows:
///
///     class ActiveObject
///     {
///     public:
///         ActiveObject():
///             _activity(this, &ActiveObject::runActivity)
///         {
///             ...
///         }
///
///         ...
///
///     protected:
///         void runActivity()
///         {
///             while (!_activity.isStopped())
///             {
///                 ...
///             }
///         }
///
///     private:
///         Activity<ActiveObject> _activity;
///     };
{
public:
    typedef RunnableAdapter<C> RunnableAdapterType;
    typedef typename RunnableAdapterType::Callback Callback;

    Activity(C * pOwner, Callback method) : _pOwner(pOwner), _runnable(*pOwner, method), _stopped(true), _running(false), _done(false)
    /// Creates the activity. Call start() to
    /// start it.
    {
        poco_check_ptr(pOwner);
    }

    ~Activity()
    /// Stops and destroys the activity.
    {
        try
        {
            stop();
            wait();
        }
        catch (...)
        {
            poco_unexpected();
        }
    }

    void start()
    /// Starts the activity by acquiring a
    /// thread for it from the default thread pool.
    {
        start(ThreadPool::defaultPool());
    }

    void start(ThreadPool & pool)
    {
        FastMutex::ScopedLock lock(_mutex);

        if (!_running)
        {
            _done.reset();
            _stopped = false;
            _running = true;
            try
            {
                pool.start(*this);
            }
            catch (...)
            {
                _running = false;
                throw;
            }
        }
    }

    void stop()
    /// Requests to stop the activity.
    {
        FastMutex::ScopedLock lock(_mutex);

        _stopped = true;
    }

    void wait()
    /// Waits for the activity to complete.
    {
        if (_running)
        {
            _done.wait();
        }
    }

    void wait(long milliseconds)
    /// Waits the given interval for the activity to complete.
    /// An TimeoutException is thrown if the activity does not
    /// complete within the given interval.
    {
        if (_running)
        {
            _done.wait(milliseconds);
        }
    }

    bool isStopped() const
    /// Returns true if the activity has been requested to stop.
    {
        return _stopped;
    }

    bool isRunning() const
    /// Returns true if the activity is running.
    {
        return _running;
    }

protected:
    void run()
    {
        try
        {
            _runnable.run();
        }
        catch (...)
        {
            _running = false;
            _done.set();
            throw;
        }
        _running = false;
        _done.set();
    }

private:
    Activity();
    Activity(const Activity &);
    Activity & operator=(const Activity &);

    C * _pOwner;
    RunnableAdapterType _runnable;
    volatile bool _stopped;
    volatile bool _running;
    Event _done;
    FastMutex _mutex;
};


} // namespace Poco


#endif // Foundation_Activity_INCLUDED