#ifndef SIMGRID_KERNEL_FUTURE_HPP
#define SIMGRID_KERNEL_FUTURE_HPP
-#include <boost/optional.hpp>
-
-#include <xbt/base.h>
-#include <xbt/functional.hpp>
-
#include <functional>
#include <future>
#include <memory>
#include <utility>
#include <type_traits>
+#include <boost/optional.hpp>
+
+#include <xbt/base.h>
+#include <xbt/functional.hpp>
+#include <xbt/future.hpp>
+
namespace simgrid {
namespace kernel {
done,
};
+template<class T>
+struct is_future : std::false_type {};
+template<class T>
+struct is_future<Future<T>> : std::true_type {};
+
/** Bases stuff for all @ref simgrid::kernel::FutureState<T> */
class FutureStateBase {
public:
FutureStateBase(FutureStateBase const&) = delete;
FutureStateBase& operator=(FutureStateBase const&) = delete;
+ XBT_PUBLIC(void) schedule(simgrid::xbt::Task<void()>&& job);
+
void set_exception(std::exception_ptr exception)
{
xbt_assert(exception_ == nullptr);
this->set_ready();
}
- void set_continuation(simgrid::xbt::Task<void()> continuation)
+ void set_continuation(simgrid::xbt::Task<void()>&& continuation)
{
- xbt_assert(!continuation_);
+ xbt_assert(not continuation_);
switch (status_) {
case FutureStatus::done:
// This is not supposed to happen if continuation is set
case FutureStatus::ready:
// The future is ready, execute the continuation directly.
// We might execute it from the event loop instead:
- continuation();
+ schedule(std::move(continuation));
break;
case FutureStatus::not_ready:
// The future is not ready so we mast keep the continuation for
// executing it later:
continuation_ = std::move(continuation);
break;
+ default:
+ DIE_IMPOSSIBLE;
}
}
}
protected:
- FutureStateBase() {}
- ~FutureStateBase() {};
+ FutureStateBase() = default;
+ ~FutureStateBase() = default;
/** Set the future as ready and trigger the continuation */
void set_ready()
// We need to do this becase the current implementation of the
// continuation has a shared_ptr to the FutureState.
auto continuation = std::move(continuation_);
- continuation();
+ this->schedule(std::move(continuation));
}
}
status_ = FutureStatus::done;
if (exception_) {
std::exception_ptr exception = std::move(exception_);
+ exception_ = nullptr;
std::rethrow_exception(std::move(exception));
}
}
}
};
+template<class T>
+void bindPromise(Promise<T> promise, Future<T> future)
+{
+ struct PromiseBinder {
+ public:
+ PromiseBinder(Promise<T> promise) : promise_(std::move(promise)) {}
+ void operator()(Future<T> future)
+ {
+ simgrid::xbt::setPromise(promise_, future);
+ }
+ private:
+ Promise<T> promise_;
+ };
+ future.then_(PromiseBinder(std::move(promise)));
+}
+
+template<class T> Future<T> unwrapFuture(Future<Future<T>> future);
+
/** Result of some (probably) asynchronous operation in the SimGrid kernel
*
* @ref simgrid::simix::Future and @ref simgrid::simix::Future provide an
template<class T>
class Future {
public:
- Future() {}
- Future(std::shared_ptr<FutureState<T>> state): state_(std::move(state)) {}
+ Future() = default;
+ Future(std::shared_ptr<FutureState<T>> state) : state_(std::move(state)) {}
// Move type:
Future(Future&) = delete;
Future(Future&& that) : state_(std::move(that.state_)) {}
Future& operator=(Future&& that)
{
- state_ = std::move(that.stat_);
+ state_ = std::move(that.state_);
+ return *this;
}
/** Whether the future is valid:.
return state_ != nullptr && state_->is_ready();
}
+ /** Attach a continuation to this future
+ *
+ * This is like .then() but avoid the creation of a new future.
+ */
+ template<class F>
+ void then_(F continuation)
+ {
+ if (state_ == nullptr)
+ throw std::future_error(std::future_errc::no_state);
+ // Give shared-ownership to the continuation:
+ auto state = std::move(state_);
+ state->set_continuation(simgrid::xbt::makeTask(
+ std::move(continuation), state));
+ }
+
+ /** Attach a continuation to this future
+ *
+ * This version never does future unwrapping.
+ */
+ template<class F>
+ auto thenNoUnwrap(F continuation)
+ -> Future<decltype(continuation(std::move(*this)))>
+ {
+ typedef decltype(continuation(std::move(*this))) R;
+ if (state_ == nullptr)
+ throw std::future_error(std::future_errc::no_state);
+ auto state = std::move(state_);
+ // Create a new future...
+ Promise<R> promise;
+ Future<R> future = promise.get_future();
+ // ...and when the current future is ready...
+ state->set_continuation(simgrid::xbt::makeTask(
+ [](Promise<R> promise, std::shared_ptr<FutureState<T>> state, F continuation) {
+ // ...set the new future value by running the continuation.
+ Future<T> future(std::move(state));
+ simgrid::xbt::fulfillPromise(promise,[&]{
+ return continuation(std::move(future));
+ });
+ },
+ std::move(promise), state, std::move(continuation)));
+ return std::move(future);
+ }
+
/** Attach a continuation to this future
*
* The future must be valid in order to make this call.
* The continuation is executed when the future becomes ready.
* The future becomes invalid after this call.
*
- * We don't support future chaining for now (`.then().then()`).
- *
* @param continuation This function is called with a ready future
* the future is ready
* @exception std::future_error no state is associated with the future
*/
+ template <class F>
+ auto then(F continuation) -> typename std::enable_if<not is_future<decltype(continuation(std::move(*this)))>::value,
+ Future<decltype(continuation(std::move(*this)))>>::type
+ {
+ return this->thenNoUnwrap(std::move(continuation));
+ }
+
+ /** Attach a continuation to this future (future chaining) */
template<class F>
- void then(F continuation)
+ auto then(F continuation)
+ -> typename std::enable_if<
+ is_future<decltype(continuation(std::move(*this)))>::value,
+ decltype(continuation(std::move(*this)))
+ >::type
{
- if (state_ == nullptr)
- throw std::future_error(std::future_errc::no_state);
- // Give shared-ownership to the continuation:
- auto state = std::move(state_);
- state->set_continuation(simgrid::xbt::makeTask(
- std::move(continuation), state));
+ return unwrapFuture(this->thenNoUnwap(std::move(continuation)));
}
/** Get the value from the future
- *
- * This is expected to be called
*
* The future must be valid and ready in order to make this call.
* @ref std::future blocks when the future is not ready but we are
std::shared_ptr<FutureState<T>> state_;
};
-/** Producer side of a @simgrid::kernel::Future
+template<class T>
+Future<T> unwrapFuture(Future<Future<T>> future)
+{
+ Promise<T> promise;
+ Future<T> result = promise.get_future();
+ bindPromise(std::move(promise), std::move(future));
+ return std::move(result);
+}
+
+/** Producer side of a @ref simgrid::kernel::Future
*
* A @ref Promise is connected to some `Future` and can be used to
* set its result.
Promise(std::shared_ptr<FutureState<T>> state) : state_(std::move(state)) {}
// Move type
- Promise(Promise&) = delete;
- Promise& operator=(Promise&) = delete;
+ Promise(Promise const&) = delete;
+ Promise& operator=(Promise const&) = delete;
Promise(Promise&& that) :
- state_(std::move(that.state_)), future_get_(that.future_set)
+ state_(std::move(that.state_)), future_get_(that.future_get_)
{
that.future_get_ = false;
}
}
// Move type
- Promise(Promise&) = delete;
- Promise& operator=(Promise&) = delete;
+ Promise(Promise const&) = delete;
+ Promise& operator=(Promise const&) = delete;
Promise(Promise&& that) :
state_(std::move(that.state_)), future_get_(that.future_get_)
{
