-/* Copyright (c) 2016. The SimGrid Team.
+/* Copyright (c) 2016-2018. The SimGrid Team.
* All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
#ifndef SIMGRID_KERNEL_FUTURE_HPP
#define SIMGRID_KERNEL_FUTURE_HPP
-#include <boost/optional.hpp>
-
-#include <xbt/base.h>
-
#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 {
// Those are implementation details:
enum class FutureStatus;
template<class T> class FutureState;
-class FutureContinuation;
-template<class T, class F> class FutureContinuationImpl;
enum class FutureStatus {
not_ready,
done,
};
-/** A continuation attached to a future to be executed when it is ready */
-XBT_PUBLIC_CLASS FutureContinuation {
-public:
- FutureContinuation() {}
-
- // No copy:
- FutureContinuation(FutureContinuation&) = delete;
- FutureContinuation& operator=(FutureContinuation&) = delete;
-
- virtual ~FutureContinuation() {}
- virtual void operator()() = 0;
-};
-
-/** Default implementation of `FutureContinuation`
- *
- * @param T value type of the future
- * @param F type of the wrapped code/callback/continuation
- */
-template<class T, class F>
-class FutureContinuationImpl : public FutureContinuation {
-public:
- FutureContinuationImpl(std::shared_ptr<FutureState<T>> ptr, F callback)
- : ptr_(std::move(ptr)), callback_(std::move(callback)) {}
- ~FutureContinuationImpl() override {}
- void operator()() override
- {
- try {
- callback_(Future<T>(ptr_));
- }
- // Those exceptions are lost.
- // If we want to implement callback chaining, we'll have to catch them and
- // foward them to the next future.
- catch (...) {
- // We could log this.
- }
- }
-private:
- std::shared_ptr<FutureState<T>> ptr_;
- F callback_;
-};
+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 {
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(std::unique_ptr<FutureContinuation> 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));
}
}
private:
FutureStatus status_ = FutureStatus::not_ready;
std::exception_ptr exception_;
- std::unique_ptr<FutureContinuation> continuation_;
+ simgrid::xbt::Task<void()> continuation_;
};
/** Shared state for future and promises
* You are not expected to use them directly but to create them
* implicitely through a @ref simgrid::kernel::Promise.
* Alternatively kernel operations could inherit or contain FutureState
- * if they are managed with @ref std::shared_ptr.
+ * if they are managed with std::shared_ptr.
**/
template<class T>
class FutureState : public FutureStateBase {
xbt_assert(this->value_);
T* result = value_;
value_ = nullptr;
- return *value_;
+ return *result;
}
private:
}
};
-/** Result of some (possibly ongoing, asynchronous) operation in the SimGrid kernel
+template <class T> void bind_promise(Promise<T> promise, Future<T> future)
+{
+ class PromiseBinder {
+ public:
+ explicit PromiseBinder(Promise<T> promise) : promise_(std::move(promise)) {}
+ void operator()(Future<T> future) { simgrid::xbt::set_promise(promise_, future); }
+
+ private:
+ Promise<T> promise_;
+ };
+ future.then_(PromiseBinder(std::move(promise)));
+}
+
+template <class T> Future<T> unwrap_future(Future<Future<T>> future);
+
+template <class T>
+XBT_ATTRIB_DEPRECATED_v323("Please use bind_promise") void bindPromise(Promise<T> promise, Future<T> future)
+{
+ bind_promise(promise, future);
+}
+template <class T>
+XBT_ATTRIB_DEPRECATED_v323("Please use unwrap_future") Future<T> unwrapFuture(Future<Future<T>> future)
+{
+ unwrap_future(future);
+}
+
+/** Result of some (probably) asynchronous operation in the SimGrid kernel
+ *
+ * @ref simgrid::simix::Future and @ref simgrid::simix::Future provide an
+ * abstration for asynchronous stuff happening in the SimGrid kernel. They
+ * are based on C++1z futures.
*
- * As the operation may not be completed yet, the result might be an exception.
+ * The future represents a value which will be available at some point when this
+ * asynchronous operaiont is finished. Alternatively, if this operations fails,
+ * the result of the operation might be an exception.
+ *
+ * As the operation is possibly no terminated yet, we cannot get the result
+ * yet. Moreover, as we cannot block in the SimGrid kernel we cannot wait for
+ * it. However, we can attach some code/callback/continuation which will be
+ * executed when the operation terminates.
*
* Example of the API (`simgrid::kernel::createProcess` does not exist):
* <pre>
* );
* </pre>
*
- * This is based on C++1z @ref std::future but with some differences:
+ * This is based on C++1z std::future but with some differences:
*
* * there is no thread synchronization (atomic, mutex, condition variable,
* etc.) because everything happens in the SimGrid event loop;
template<class T>
class Future {
public:
- Future() {}
- Future(std::shared_ptr<FutureState<T>> state): state_(std::move(state)) {}
+ Future() = default;
+ explicit 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::make_task(std::move(continuation), state));
+ }
+
+ /** Attach a continuation to this future
+ *
+ * This version never does future unwrapping.
+ */
+ template <class F> auto then_no_unwrap(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::make_task(
+ [](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::fulfill_promise(promise, [&] { return continuation(std::move(future)); });
+ },
+ std::move(promise), state, std::move(continuation)));
+ return future;
+ }
+
+ template <class F>
+ XBT_ATTRIB_DEPRECATED_v323("Please use then_no_unwrap") auto thenNoUnwrap(F continuation)
+ -> Future<decltype(continuation(std::move(*this)))>
+ {
+ then_no_unwrap(continuation);
+ }
+
/** 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->then_no_unwrap(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);
- std::unique_ptr<FutureContinuation> ptr =
- std::unique_ptr<FutureContinuation>(
- new FutureContinuationImpl<T,F>(state_, std::move(continuation)));
- state_->set_continuation(std::move(ptr));
- state_ = nullptr;
+ return unwrap_future(this->then_no_unwrap(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::future blocks when the future is not ready but we are
* completely single-threaded so blocking would be a deadlock.
* After the call, the future becomes invalid.
*
std::shared_ptr<FutureState<T>> state_;
};
-/** Producer side of a @simgrid::kernel::Future
+template <class T> Future<T> unwrap_future(Future<Future<T>> future)
+{
+ Promise<T> promise;
+ Future<T> result = promise.get_future();
+ bind_promise(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.
*
- * Similar to @ref std::promise
+ * Similar to std::promise
*
* <code>
* // Create a promise and a future:
class Promise {
public:
Promise() : state_(std::make_shared<FutureState<T>>()) {}
- Promise(std::shared_ptr<FutureState<T>> state) : state_(std::move(state)) {}
+ explicit 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;
}
class Promise<void> {
public:
Promise() : state_(std::make_shared<FutureState<void>>()) {}
- Promise(std::shared_ptr<FutureState<void>> state) : state_(std::move(state)) {}
+ explicit Promise(std::shared_ptr<FutureState<void>> state) : state_(std::move(state)) {}
~Promise()
{
if (state_ && state_->get_status() == FutureStatus::not_ready)
}
// 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_)
{
