activeresult.h

C++ class libraries for network-centric, portable applications, integrated perfectly with the C++ St

//
// ActiveResult.h
//
// $Id: //poco/1.2/Foundation/include/Poco/ActiveResult.h#1 $
//
// Library: Foundation
// Package: Threading
// Module:  ActiveObjects
//
// Definition of the ActiveResult class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_ActiveResult_INCLUDED
#define Foundation_ActiveResult_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Mutex.h"
#include "Poco/Event.h"
#include "Poco/RefCountedObject.h"
#include "Poco/Exception.h"


namespace Poco {


template <class ResultType>
class ActiveResultHolder: public RefCountedObject
	/// This class holds the result of an asynchronous method
	/// invocation. It is used to pass the result from the
	/// execution thread back to the invocation thread. 
	/// The class uses reference counting for memory management.
	/// Do not use this class directly, use ActiveResult instead.
{
public:
	ActiveResultHolder():
		_pExc(0),
		_event(false)
		/// Creates an ActiveResultHolder.
	{
	}
	
	ResultType& data()
		/// Returns a reference to the actual result.
	{
		return _data;
	}
	
	void wait()
		/// Pauses the caller until the result becomes available.
	{
		_event.wait();
	}
	
	bool tryWait(long milliseconds)
		/// Waits up to the specified interval for the result to
		/// become available. Returns true if the result became
		/// available, false otherwise.
	{
		return _event.tryWait(milliseconds);
	}
	
	void wait(long milliseconds)
		/// Waits up to the specified interval for the result to
		/// become available. Throws a TimeoutException if the
		/// result did not became available.
	{
		_event.wait(milliseconds);
	}
	
	void notify()
		/// Notifies the invoking thread that the result became available.
	{
		_event.set();
	}
	
	bool failed() const
		/// Returns true if the active method failed (and threw an exception).
		/// Information about the exception can be obtained by calling error().
	{
		return _pExc != 0;
	}
	
	std::string error() const
		/// If the active method threw an exception, a textual representation
		/// of the exception is returned. An empty string is returned if the
		/// active method completed successfully.
	{
		if (_pExc)
			return _pExc->message();
		else
			return std::string();
	}
	
	Exception* exception() const
		/// If the active method threw an exception, a clone of the exception
		/// object is returned, otherwise null.
	{
		return _pExc;
	}
	
	void error(const Exception& exc)
		/// Sets the exception.
	{
		delete _pExc;
		_pExc = exc.clone();
	}
	
	void error(const std::string& msg)
		/// Sets the exception.
	{
		delete _pExc;
		_pExc = new UnhandledException(msg);
	}

protected:
	~ActiveResultHolder()
	{
		delete _pExc;
	}

private:
	ResultType _data;
	Exception* _pExc;
	Event      _event;
};


template <class RT>
class ActiveResult
	/// This class holds the result of an asynchronous method
	/// invocation (see class ActiveMethod). It is used to pass the 
	/// result from the execution thread back to the invocation thread. 
{
public:
	typedef RT ResultType;
	typedef ActiveResultHolder<ResultType> ActiveResultHolderType;

	ActiveResult(ActiveResultHolderType* pHolder):
		_pHolder(pHolder)
		/// Creates the active result. For internal use only.
	{
		poco_check_ptr (pHolder);
	}
	
	ActiveResult(const ActiveResult& result)
		/// Copy constructor.
	{
		_pHolder = result._pHolder;
		_pHolder->duplicate();
	}
	
	~ActiveResult()
		/// Destroys the result.
	{
		_pHolder->release();
	}
	
	ActiveResult& operator = (const ActiveResult& result)
		/// Assignment operator.
	{
		if (&result != this)
		{
			_pHolder->release();
			_pHolder = result._pHolder;
			_pHolder->duplicate();
		}
		return *this;
	}
	
	const ResultType& data() const
		/// Returns a reference to the result data.
	{
		return _pHolder->data();
	}
	
	void wait()
		/// Pauses the caller until the result becomes available.
	{
		_pHolder->wait();
	}
	
	bool tryWait(long milliseconds)
		/// Waits up to the specified interval for the result to
		/// become available. Returns true if the result became
		/// available, false otherwise.
	{
		return _pHolder->tryWait(milliseconds);
	}
	
	void wait(long milliseconds)
		/// Waits up to the specified interval for the result to
		/// become available. Throws a TimeoutException if the
		/// result did not became available.
	{
		_pHolder->wait(milliseconds);
	}
	
	bool available() const
		/// Returns true if a result is available.
	{
		return _pHolder->tryWait(0);
	}
	
	bool failed() const
		/// Returns true if the active method failed (and threw an exception).
		/// Information about the exception can be obtained by calling error().
	{
		return _pHolder->failed();
	}
	
	std::string error() const
		/// If the active method threw an exception, a textual representation
		/// of the exception is returned. An empty string is returned if the
		/// active method completed successfully.
	{
		return _pHolder->error();
	}

	Exception* exception() const
		/// If the active method threw an exception, a clone of the exception
		/// object is returned, otherwise null.
	{
		return _pHolder->exception();
	}

	void notify()
		/// Notifies the invoking thread that the result became available.
		/// For internal use only.
	{
		_pHolder->notify();
	}
	
	ResultType& data()
		/// Returns a non-const reference to the result data. For internal
		/// use only.
	{
		return _pHolder->data();
	}
	
	void error(const std::string& msg)
		/// Sets the failed flag and the exception message.
	{
		_pHolder->error(msg);
	}

	void error(const Exception& exc)
		/// Sets the failed flag and the exception message.
	{
		_pHolder->error(exc);
	}
	
private:
	ActiveResult();

	ActiveResultHolderType* _pHolder;
};


} // namespace Poco


#endif // Foundation_ActiveResult_INCLUDED