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ActiveResult.h

//
// 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>
00054 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.
      {
      }
      
00069       ResultType& data()
            /// Returns a reference to the actual result.
      {
            return _data;
      }
      
00075       void wait()
            /// Pauses the caller until the result becomes available.
      {
            _event.wait();
      }
      
00081       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);
      }
      
00089       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);
      }
      
00097       void notify()
            /// Notifies the invoking thread that the result became available.
      {
            _event.set();
      }
      
00103       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;
      }
      
00110       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();
      }
      
00121       Exception* exception() const
            /// If the active method threw an exception, a clone of the exception
            /// object is returned, otherwise null.
      {
            return _pExc;
      }
      
00128       void error(const Exception& exc)
            /// Sets the exception.
      {
            delete _pExc;
            _pExc = exc.clone();
      }
      
00135       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>
00156 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);
      }
      
00172       ActiveResult(const ActiveResult& result)
            /// Copy constructor.
      {
            _pHolder = result._pHolder;
            _pHolder->duplicate();
      }
      
00179       ~ActiveResult()
            /// Destroys the result.
      {
            _pHolder->release();
      }
      
00185       ActiveResult& operator = (const ActiveResult& result)
            /// Assignment operator.
      {
            if (&result != this)
            {
                  _pHolder->release();
                  _pHolder = result._pHolder;
                  _pHolder->duplicate();
            }
            return *this;
      }
      
00197       const ResultType& data() const
            /// Returns a reference to the result data.
      {
            return _pHolder->data();
      }
      
00203       void wait()
            /// Pauses the caller until the result becomes available.
      {
            _pHolder->wait();
      }
      
00209       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);
      }
      
00217       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);
      }
      
00225       bool available() const
            /// Returns true if a result is available.
      {
            return _pHolder->tryWait(0);
      }
      
00231       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();
      }
      
00238       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();
      }

00246       Exception* exception() const
            /// If the active method threw an exception, a clone of the exception
            /// object is returned, otherwise null.
      {
            return _pHolder->exception();
      }

00253       void notify()
            /// Notifies the invoking thread that the result became available.
            /// For internal use only.
      {
            _pHolder->notify();
      }
      
00260       ResultType& data()
            /// Returns a non-const reference to the result data. For internal
            /// use only.
      {
            return _pHolder->data();
      }
      
00267       void error(const std::string& msg)
            /// Sets the failed flag and the exception message.
      {
            _pHolder->error(msg);
      }

00273       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

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