request.h

/* Copyright (c) 2013-2015, Stefan.Eilemann@epfl.ch
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License version 2.1 as published
 * by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifndef LUNCHBOX_REQUEST_H
#define LUNCHBOX_REQUEST_H

#include <boost/mpl/if.hpp>
#include <boost/type_traits/is_same.hpp>
#include <lunchbox/future.h>

namespace lunchbox
{
class UnregisteredRequest : public std::runtime_error
{
public:
    UnregisteredRequest()
        : std::runtime_error("wait on an unregistered request")
    {
    }
};

template <class T>
class Request : public Future<T>
{
    class Impl;

public:
    Request(RequestHandler& handler, const uint32_t request);

    virtual ~Request();

    uint32_t getID() const;

    void unregister();
};
} // namespace lunchbox

// Implementation: Here be dragons

#include <lunchbox/requestHandler.h>
namespace lunchbox
{
template <class T>
class Request<T>::Impl : public FutureImpl<T>
{
    typedef typename boost::mpl::if_<boost::is_same<T, void>, void*, T>::type
        value_t;

public:
    Impl(RequestHandler& handler, const uint32_t req)
        : request(req)
        , result(0)
        , handler_(handler)
        , state_(UNRESOLVED)
    {
    }
    virtual ~Impl() {}
    const uint32_t request;
    value_t result;

    void unregister()
    {
        if (state_ == UNRESOLVED)
        {
            state_ = UNREGISTERED;
            handler_.unregisterRequest(request);
        }
    }

    bool isUnresolved() const { return state_ == UNRESOLVED; }

protected:
    T wait(const uint32_t timeout) final
    {
        switch (state_)
        {
        case UNREGISTERED:
            throw UnregisteredRequest();
        case UNRESOLVED:
            if (!handler_.waitRequest(request, result, timeout))
                throw FutureTimeout();
            state_ = DONE;
            break;
        case DONE:
        default:
            break;
        }
        return result;
    }

    bool isReady() const final
    {
        switch (state_)
        {
        case UNRESOLVED:
            return handler_.isRequestReady(request);
        case UNREGISTERED:
            return false;
        default: // DONE:
            return true;
        }
    }

private:
    RequestHandler& handler_;
    enum State
    {
        UNRESOLVED,
        DONE,
        UNREGISTERED
    };
    State state_;
};

template <>
inline void Request<void>::Impl::wait(const uint32_t timeout)
{
    switch (state_)
    {
    case UNREGISTERED:
        throw UnregisteredRequest();
    case UNRESOLVED:
        if (!handler_.waitRequest(request, result, timeout))
            throw FutureTimeout();
        state_ = DONE;
    // No break
    case DONE:;
    }
}

template <class T>
inline Request<T>::Request(RequestHandler& handler, const uint32_t request)
    : Future<T>(new Impl(handler, request))
{
}

template <class T>
inline Request<T>::~Request()
{
    if (static_cast<const Impl*>(this->impl_.get())->isUnresolved())
        this->wait();
}

template <class T>
inline uint32_t Request<T>::getID() const
{
    return static_cast<const Impl*>(this->impl_.get())->request;
}

template <class T>
inline void Request<T>::unregister()
{
    static_cast<Impl*>(this->impl_.get())->unregister();
}
} // namespace lunchbox

#endif // LUNCHBOX_REQUEST_H