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// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
// SPDX-FileCopyrightInfo: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
#ifndef DUNE_COMMON_PARALLEL_FUTURE_HH
#define DUNE_COMMON_PARALLEL_FUTURE_HH
#include <memory>
#include <type_traits>
#include <dune/common/exceptions.hh>
namespace Dune{
/*! \brief This exception is thrown when `ready()`, `wait()` or `get()` is
called on an invalid future. A future is valid until `get()` is called and
if it is not default-constructed and it was not moved from.
*/
class InvalidFutureException : public InvalidStateException
{};
// forward declaration
template<class T>
class PseudoFuture;
/*! \brief Type-erasure for future-like objects. A future-like object is a
object satisfying the interface of FutureBase.
*/
template<class T>
class Future{
// Future interface:
class FutureBase{
public:
virtual ~FutureBase() = default;
virtual void wait() = 0;
virtual bool ready() const = 0;
virtual bool valid() const = 0;
virtual T get() = 0;
};
// model class
template<class F>
class FutureModel
: public FutureBase
{
F _future;
public:
FutureModel(F&& f)
: _future(std::forward<F>(f))
{}
virtual void wait() override
{
_future.wait();
}
virtual bool ready() const override
{
return _future.ready();
}
virtual bool valid() const override
{
return _future.valid();
}
virtual T get() override{
return (T)_future.get();
}
};
std::unique_ptr<FutureBase> _future;
public:
template<class F>
Future(F&& f)
: _future(std::make_unique<FutureModel<F>>(std::forward<F>(f)))
{}
template<class U, std::enable_if_t<std::is_same<U,T>::value && !std::is_same<T,void>::value>>
Future(U&& data)
: _future(std::make_unique<FutureModel<PseudoFuture<T>>>(PseudoFuture<T>(std::forward<U>(data))))
{}
Future() = default;
/*! \brief wait until the future is ready
\throws InvalidFutureException
*/
void wait(){
_future->wait();
}
/*! \brief Waits until the future is ready and returns the resulting value
\returns The contained value
\throws InvalidFutureException
*/
T get() {
return _future->get();
}
/*! \brief
\returns true is the future is ready, otherwise false
\throws InvalidFutureException
*/
bool ready() const {
return _future->ready();
}
/*! \brief Checks whether the future is valid. I.e. `get()' was not called
on that future and when it was not default-constructed and not moved
from.
\returns true is the future is valid, otherwise false
*/
bool valid() const {
if(_future)
return _future->valid();
return false;
}
};
/*! \brief A wrapper-class for a object which is ready immediately.
*/
template<class T>
class PseudoFuture{
bool valid_;
T data_;
public:
PseudoFuture() :
valid_(false)
{}
template<class U>
PseudoFuture(U&& u) :
valid_(true),
data_(std::forward<U>(u))
{}
void wait() {
if(!valid_)
DUNE_THROW(InvalidFutureException, "The PseudoFuture is not valid");
}
bool ready() const {
if(!valid_)
DUNE_THROW(InvalidFutureException, "The PseudoFuture is not valid");
return true;
}
T get() {
if(!valid_)
DUNE_THROW(InvalidFutureException, "The PseudoFuture is not valid");
valid_ = false;
return std::forward<T>(data_);
}
bool valid() const {
return valid_;
}
};
template<>
class PseudoFuture<void>{
bool valid_;
public:
PseudoFuture(bool valid = false) :
valid_(valid)
{}
void wait(){
if(!valid_)
DUNE_THROW(InvalidFutureException, "The PseudoFuture is not valid");
}
bool ready() const{
if(!valid_)
DUNE_THROW(InvalidFutureException, "The PseudoFuture is not valid");
return true;
}
void get(){
if(!valid_)
DUNE_THROW(InvalidFutureException, "The PseudoFuture is not valid");
valid_ = false;
}
bool valid() const{
return valid_;
}
};
}
#endif // DUNE_COMMON_PARALLEL_FUTURE_HH
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