--- /dev/null
+/* Copyright (c) 2016-2021. The SimGrid Team. All rights reserved. */
+
+/* This program is free software; you can redistribute it and/or modify it
+ * under the terms of the license (GNU LGPL) which comes with this package. */
+
+#ifndef SIMGRID_SIMIX_BLOCKING_SIMCALL_HPP
+#define SIMGRID_SIMIX_BLOCKING_SIMCALL_HPP
+
+#include <exception>
+#include <functional>
+#include <future>
+#include <utility>
+
+#include <xbt/sysdep.h>
+
+#include <simgrid/kernel/future.hpp>
+#include <simgrid/simix.h>
+#include <simgrid/simix.hpp>
+#include <xbt/promise.hpp>
+
+namespace simgrid {
+namespace simix {
+
+/** Execute some code in kernel mode and wakes up the actor when
+ * the result is available.
+ *
+ * It is given a callback which is executed in the SimGrid kernel and
+ * returns a `simgrid::kernel::Future<T>`. The kernel blocks the actor
+ * until the Future is ready and:
+ *
+ * - either returns the value wrapped in the future to the actor
+ *
+ * - or raises the exception stored in the future in the actor.
+ *
+ * This can be used to implement blocking calls without adding new simcalls.
+ * One downside of this approach is that we don't have any semantic on what
+ * the actor is waiting. This might be a problem for the model-checker and
+ * we'll have to devise a way to make it work.
+ *
+ * @param code Kernel code returning a `simgrid::kernel::Future<T>`
+ * @return Value of the kernel future
+ * @exception Exception from the kernel future
+ */
+template <class F> auto kernel_sync(F code) -> decltype(code().get())
+{
+ using T = decltype(code().get());
+ xbt_assert(not SIMIX_is_maestro(), "Cannot execute blocking call in kernel mode");
+
+ smx_actor_t self = SIMIX_process_self();
+ simgrid::xbt::Result<T> result;
+ simcall_run_blocking(
+ [&result, self, &code] {
+ try {
+ auto future = code();
+ future.then_([&result, self](std::shared_ptr<simgrid::kernel::FutureState<T>> value) {
+ simgrid::xbt::set_promise(result, simgrid::kernel::Future<T>(std::move(value)));
+ simgrid::simix::unblock(self);
+ });
+ } catch (...) {
+ result.set_exception(std::current_exception());
+ simgrid::simix::unblock(self);
+ }
+ },
+ nullptr);
+ return result.get();
+}
+
+/** A blocking (`wait()`-based) future for SIMIX processes */
+// TODO:
+// - .wait_for
+// - .wait_until
+// - SharedFuture
+// - simgrid::simix::when_all - wait for all future to be ready (this one is simple!)
+// - simgrid::simix::when_any - wait for any future to be ready
+template <class T> class Future {
+public:
+ Future() = default;
+ explicit Future(simgrid::kernel::Future<T> future) : future_(std::move(future)) {}
+ Future(Future&&) noexcept = default;
+ Future& operator=(Future&&) noexcept = default;
+
+ bool valid() const { return future_.valid(); }
+ T get()
+ {
+ if (not valid())
+ throw std::future_error(std::future_errc::no_state);
+ smx_actor_t self = SIMIX_process_self();
+ simgrid::xbt::Result<T> result;
+ simcall_run_blocking(
+ [this, &result, self] {
+ try {
+ // When the kernel future is ready...
+ this->future_.then_([&result, self](std::shared_ptr<simgrid::kernel::FutureState<T>> value) {
+ // ... wake up the process with the result of the kernel future.
+ simgrid::xbt::set_promise(result, simgrid::kernel::Future<T>(std::move(value)));
+ simgrid::simix::unblock(self);
+ });
+ } catch (...) {
+ result.set_exception(std::current_exception());
+ simgrid::simix::unblock(self);
+ }
+ },
+ nullptr);
+ return result.get();
+ }
+ bool is_ready() const
+ {
+ if (not valid())
+ throw std::future_error(std::future_errc::no_state);
+ return future_.is_ready();
+ }
+ void wait()
+ {
+ // The future is ready! We don't have to wait:
+ if (this->is_ready())
+ return;
+ // The future is not ready. We have to delegate to the SimGrid kernel:
+ std::exception_ptr exception;
+ smx_actor_t self = SIMIX_process_self();
+ simcall_run_blocking(
+ [this, &exception, self] {
+ try {
+ // When the kernel future is ready...
+ this->future_.then_([this, self](std::shared_ptr<simgrid::kernel::FutureState<T>> value) {
+ // ...store it the simix kernel and wake up.
+ this->future_ = simgrid::kernel::Future<T>(std::move(value));
+ simgrid::simix::unblock(self);
+ });
+ } catch (...) {
+ exception = std::current_exception();
+ simgrid::simix::unblock(self);
+ }
+ },
+ nullptr);
+ }
+
+private:
+ // We wrap an event-based kernel future:
+ simgrid::kernel::Future<T> future_;
+};
+
+/** Start some asynchronous work
+ *
+ * @param code SimGrid kernel code which returns a simgrid::kernel::Future
+ * @return Actor future
+ */
+template <class F> auto kernel_async(F code) -> Future<decltype(code().get())>
+{
+ using T = decltype(code().get());
+
+ // Execute the code in the kernel and get the kernel future:
+ simgrid::kernel::Future<T> future = simgrid::kernel::actor::simcall(std::move(code));
+
+ // Wrap the kernel future in an actor future:
+ return simgrid::simix::Future<T>(std::move(future));
+}
+}
+}
+
+#endif
