X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/8f2e8075d660a354a3aabf065998f42802f9cc11..a0846dc62a4cd480eaa8642b8d1bea8b84fddf3b:/include/simgrid/kernel/future.hpp

diff --git a/include/simgrid/kernel/future.hpp b/include/simgrid/kernel/future.hpp
index a11c8ec40c..777a9f48b2 100644
--- a/include/simgrid/kernel/future.hpp
+++ b/include/simgrid/kernel/future.hpp
@@ -7,17 +7,18 @@
 #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 {
 
@@ -35,6 +36,11 @@ enum class FutureStatus {
   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:
@@ -42,6 +48,8 @@ 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);
@@ -51,9 +59,9 @@ public:
     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
@@ -63,13 +71,15 @@ public:
     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;
     }
   }
 
@@ -84,8 +94,8 @@ public:
   }
 
 protected:
-  FutureStateBase() {}
-  ~FutureStateBase() {};
+  FutureStateBase() = default;
+  ~FutureStateBase() = default;
 
   /** Set the future as ready and trigger the continuation */
   void set_ready()
@@ -96,7 +106,7 @@ protected:
       // 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));
     }
   }
 
@@ -111,6 +121,7 @@ protected:
     status_ = FutureStatus::done;
     if (exception_) {
       std::exception_ptr exception = std::move(exception_);
+      exception_ = nullptr;
       std::rethrow_exception(std::move(exception));
     }
   }
@@ -193,6 +204,24 @@ public:
   }
 };
 
+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
@@ -252,8 +281,8 @@ public:
 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;
@@ -261,7 +290,8 @@ public:
   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:.
@@ -286,32 +316,78 @@ public:
     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
@@ -334,7 +410,16 @@ private:
   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.
@@ -373,10 +458,10 @@ public:
   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;
   }
@@ -434,8 +519,8 @@ public:
   }
 
   // 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_)
   {