X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/b9a15f078a62e397f321dfb570254652785cc377..c3afdfa7a603897d1fbca56e7d1705983038405e:/include/simgrid/kernel/future.hpp

diff --git a/include/simgrid/kernel/future.hpp b/include/simgrid/kernel/future.hpp
index c58f46b164..cedfd39c96 100644
--- a/include/simgrid/kernel/future.hpp
+++ b/include/simgrid/kernel/future.hpp
@@ -7,9 +7,13 @@
 #ifndef SIMGRID_KERNEL_FUTURE_HPP
 #define SIMGRID_KERNEL_FUTURE_HPP
 
+#include <future>
+#include <type_traits>
+
 #include <boost/optional.hpp>
 
 #include <xbt/base.h>
+#include <xbt/functional.hpp>
 
 #include <functional>
 #include <future>
@@ -27,8 +31,6 @@ template<class T> class Promise;
 // 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,
@@ -36,46 +38,10 @@ enum class FutureStatus {
   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 : public std::integral_constant<bool, false> {};
+template<class T>
+struct is_future<Future<T>> : public std::integral_constant<bool, true> {};
 
 /** Bases stuff for all @ref simgrid::kernel::FutureState<T> */
 class FutureStateBase {
@@ -93,7 +59,7 @@ public:
     this->set_ready();
   }
 
-  void set_continuation(std::unique_ptr<FutureContinuation> continuation)
+  void set_continuation(simgrid::xbt::Task<void()> continuation)
   {
     xbt_assert(!continuation_);
     switch (status_) {
@@ -105,13 +71,15 @@ public:
     case FutureStatus::ready:
       // The future is ready, execute the continuation directly.
       // We might execute it from the event loop instead:
-      (*continuation)();
+      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;
     }
   }
 
@@ -126,8 +94,8 @@ public:
   }
 
 protected:
-  FutureStateBase() {}
-  ~FutureStateBase() {};
+  FutureStateBase() = default;
+  ~FutureStateBase() = default;
 
   /** Set the future as ready and trigger the continuation */
   void set_ready()
@@ -138,7 +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)();
+      continuation();
     }
   }
 
@@ -160,7 +128,7 @@ protected:
 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
@@ -235,6 +203,24 @@ 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
@@ -294,7 +280,7 @@ public:
 template<class T>
 class Future {
 public:
-  Future() {}
+  Future() = default;
   Future(std::shared_ptr<FutureState<T>> state): state_(std::move(state)) {}
 
   // Move type:
@@ -303,7 +289,8 @@ 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:.
@@ -328,28 +315,78 @@ 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>
-  void then(F continuation)
+  auto then(F continuation)
+  -> typename std::enable_if<
+       !is_future<decltype(continuation(std::move(*this)))>::value,
+       Future<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 this->thenNoUnwrap(std::move(continuation));
+  }
+
+  /** Attach a continuation to this future (future chaining) */
+  template<class F>
+  auto then(F continuation)
+  -> typename std::enable_if<
+       is_future<decltype(continuation(std::move(*this)))>::value,
+       decltype(continuation(std::move(*this)))
+     >::type
+  {
+    return unwrapFuture(this->thenNoUnwap(std::move(continuation)));
   }
 
   /** Get the value from the future
@@ -377,6 +414,15 @@ private:
   std::shared_ptr<FutureState<T>> state_;
 };
 
+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 @simgrid::kernel::Future
  *
  *  A @ref Promise is connected to some `Future` and can be used to
@@ -416,10 +462,10 @@ 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;
   }
@@ -477,8 +523,8 @@ 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_)
   {