future.h

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/** @file
 *  @author Bram de Greve (bramz@users.sourceforge.net)
 *  @author Tom De Muer (tomdemuer@users.sourceforge.net)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2004-2007 the Initial Developer.
 *  All Rights Reserved.
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 *
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 *  GNU General Public License Version 2 or later (the GPL), in which case the 
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 *  of your version of this file only under the terms of the GPL and not to allow 
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 *  deleting the provisions above and replace them with the notice and other 
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 *  a recipient may use your version of this file under either the CPAL or the GPL.
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 *  *** END LICENSE INFORMATION ***
 */

/** Transporting Values and Exceptions between Threads
 *  @class lass::util::experimental::Future
 *
 *  See:
 *  @arg Peter Dimov: "Transporting Values and Exceptions between Threads", 
 *      http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2096.html
 *  @arg Matti Rintala: "Handling Multiple Concurrent Exceptions in C++ Using Futures", 
 *      teoksessa Advanced Topics in Exception Handling Techniques, 
 *      toim. C. Dony, J. L. Knudsen, A. Romanovsky, A. Tripathi. 
 *      LNCS 4419, 301 s, ISBN 3-540-37443-4, DOI 10.1007/11818502_4, Springer-Verlag 2006
 *      http://www.cs.tut.fi/cgi-bin/run/bitti/download/lncs-eh-draft.pdf
 *  @arg Matti Rintala: "Exceptions in remote procedure calls using C++ template metaprogramming", 
 *      Software—Practice and Experience, 2007, 37:231-246, 16 s, DOI: 10.1002/spe.754
 *      http://www.cs.tut.fi/cgi-bin/run/bitti/download/spe-mmr-preprint.pdf
 */  
 
#ifndef LASS_GUARDIAN_OF_INCLUSION_UTIL_FUTURE_H
#define LASS_GUARDIAN_OF_INCLUSION_UTIL_FUTURE_H

#include "util_common.h"
#include "shared_ptr.h"

namespace lass
{
namespace util
{
namespace experimental
{

/** @ingroup Thread
 *  @relates Future
 */
class FutureBindError: public util::Exception
{
public:
    FutureBindError(const std::string& msg, const std::string& loc): util::Exception(msg, loc) {}
private:
    LASS_UTIL_EXCEPTION_PRIVATE_IMPL(FutureBindError)
};



template <typename T>
class Future
{
public:

    Future(): pimpl_(new Impl) {}

    const bool isBound() const 
    {
        TLocker lock(pimpl_->mutex_);
        return pimpl_->isBound_ || pimpl_->isBadAlloc_ || pimpl_->error_.get(); 
    }
    const bool operator!() const { return !isBound(); }
    operator num::SafeBool() const { return isBound() ? num::safeFalse : num::safeTrue; }

    void wait() 
    {
        while (!isBound())
        {
            pimpl_->condition_.wait();
        }
    }
    const WaitResult wait(unsigned long milliSeconds)
    {
        return pimpl_->condition_.wait() == waitSuccess && isBound() ? waitSuccess : waitTimeout;
    }
    
    const T& operator()() const
    {
        wait();
        TLocker lock(pimpl_->mutex_);
        if (pimpl_->isBadAlloc_)
        {
            throw std::bad_alloc("::lass::Future::bindError: failed to clone exception");
        }
        if (pimpl_->error_.get())
        {
            pimpl_->error_->throwSelf();
        }
        return *reinterpret_cast<T*>(pimpl_->value_);
    }

    void bind(const T& value)
    {
        TLocker lock(pimpl_->mutex_);
        if (pimpl_->isBound())
        {
            LASS_THROW_EX(FutureBindError, "Future is already bound");
        }
        new (reinterpret_cast<T*>(pimpl_->value_)) T(value);
        pimpl_->isBound_ = true;
        pimpl_->condition_.broadcast();
    }
    void unbind()
    {
        TLocker lock(pimpl_->mutex_);
        pimpl_->unbind();
    }

    void error(const experimental::RemoteExceptionBase& error)
    {
        TLocker lock(pimpl_->mutex_);
        try
        {
            pimpl_->error_ = error.clone();
        }
        catch (std::bad_alloc)
        {
            pimpl_->isBadAlloc_ = true;
        }
        pimpl_->condition_.broadcast();
    }
    template <typename ExceptionType>
    void error(const ExceptionType& error)
    {
        TLocker lock(pimpl_->mutex_);
        try
        {
            pimpl_->error_ = new experimental::RemoteExceptionWrapper<ExceptionType>(error);
        }
        catch (std::bad_alloc)
        {
            pimpl_->isBadAlloc_ = true;
        }
        pimpl_->condition_.broadcast();
    }

private:

    typedef util::Semaphore TMutex;
    typedef util::Locker<TMutex> TLocker;

    struct Impl
    {
        char value_[sizeof(T)];
        std::auto_ptr<experimental::RemoteExceptionBase> error_;
        Condition condition_;
        TMutex mutex_;
        size_t referenceCount_;
        volatile bool isBound_;
        volatile bool isBadAlloc_;

        Impl(): isBound_(false) {}
        ~Impl() 
        {
            unbind();
        }
        void unbind()
        {
            if (isBound_)
            {
                reinterpret_cast<T*>(value_)->~T();
                isBound_ = false;
            }
        }
    };

    typedef util::IntrusiveCounter<Impl, size_t, &Impl::referenceCount_> TCounterPolicy;
    typedef util::SharedPtr<Impl, util::ObjectStorage, TCounterPolicy> TImplPtr;

    TImplPtr pimpl_;
};

}
}
}

#endif