shy attempt at simplifying the simcall mechanism

[simgrid.git] / include / xbt / future.hpp

diff --git a/include/xbt/future.hpp b/include/xbt/future.hpp
index be488ed..4d2842f 100644 (file)
--- a/include/xbt/future.hpp
+++ b/include/xbt/future.hpp
@@ -1,4 +1,4 @@
-/* Copyright (c) 2015-2018. The SimGrid Team.
+/* Copyright (c) 2015-2019. The SimGrid Team.
  * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
@@ -9,8 +9,10 @@
 
 #include <cstddef>
 
+#include <boost/variant.hpp>
 #include <exception>
 #include <functional>
+#include <future> // std::future_error
 #include <stdexcept>
 #include <type_traits>
 #include <utility>
@@ -28,99 +30,22 @@ namespace xbt {
  **/
 template<class T>
 class Result {
-  enum class ResultStatus {
-    invalid,
-    value,
-    exception,
-  };
 public:
-  Result() { /* Nothing to do */}
-  ~Result() { this->reset(); }
-
-  // Copy (if T is copyable) and move:
-  Result(Result const& that)
-  {
-    (*this) = that;
-  }
-  Result& operator=(Result const& that)
-  {
-    this->reset();
-    switch (that.status_) {
-      case ResultStatus::invalid:
-        break;
-      case ResultStatus::value:
-        new (&value_) T(that.value);
-        break;
-      case ResultStatus::exception:
-        new (&exception_) T(that.exception);
-        break;
-      default:
-        THROW_IMPOSSIBLE;
-    }
-    return *this;
-  }
-  Result(Result&& that)
-  {
-    *this = std::move(that);
-  }
-  Result& operator=(Result&& that)
-  {
-    this->reset();
-    switch (that.status_) {
-      case ResultStatus::invalid:
-        break;
-      case ResultStatus::value:
-        new (&value_) T(std::move(that.value));
-        that.value.~T();
-        break;
-      case ResultStatus::exception:
-        new (&exception_) T(std::move(that.exception));
-        that.exception.~exception_ptr();
-        break;
-      default:
-        THROW_IMPOSSIBLE;
-    }
-    that.status_ = ResultStatus::invalid;
-    return *this;
-  }
-
   bool is_valid() const
   {
-    return status_ != ResultStatus::invalid;
-  }
-  void reset()
-  {
-    switch (status_) {
-      case ResultStatus::invalid:
-        break;
-      case ResultStatus::value:
-        value_.~T();
-        break;
-      case ResultStatus::exception:
-        exception_.~exception_ptr();
-        break;
-      default:
-        THROW_IMPOSSIBLE;
-    }
-    status_ = ResultStatus::invalid;
+    return value_.which() > 0;
   }
   void set_exception(std::exception_ptr e)
   {
-    this->reset();
-    new (&exception_) std::exception_ptr(std::move(e));
-    status_ = ResultStatus::exception;
+    value_ = std::move(e);
   }
   void set_value(T&& value)
   {
-    this->reset();
-    new (&value_) T(std::move(value));
-    status_ = ResultStatus::value;
+    value_ = std::move(value);
   }
   void set_value(T const& value)
   {
-    this->reset();
-    new (&value_) T(value);
-    status_ = ResultStatus::value;
+    value_ = value;
   }
 
   /** Extract the value from the future
@@ -129,30 +54,24 @@ public:
    **/
   T get()
   {
-    switch (status_) {
-      case ResultStatus::value: {
-        T value = std::move(value_);
-        value_.~T();
-        status_ = ResultStatus::invalid;
-        return std::move(value);
+    switch (value_.which()) {
+      case 1: {
+        T value = std::move(boost::get<T>(value_));
+        value_  = boost::blank();
+        return value;
       }
-      case ResultStatus::exception: {
-        std::exception_ptr exception = std::move(exception_);
-        exception_.~exception_ptr();
-        status_ = ResultStatus::invalid;
+      case 2: {
+        std::exception_ptr exception = std::move(boost::get<std::exception_ptr>(value_));
+        value_                       = boost::blank();
         std::rethrow_exception(std::move(exception));
         break;
       }
       default:
-        throw std::logic_error("Invalid result");
+        throw std::future_error(std::future_errc::no_state);
     }
   }
 private:
-  ResultStatus status_ = ResultStatus::invalid;
-  union {
-    T value_;
-    std::exception_ptr exception_;
-  };
+  boost::variant<boost::blank, T, std::exception_ptr> value_;
 };
 
 template<>
@@ -207,19 +126,8 @@ template <class R, class F> auto fulfill_promise(R& promise, F&& code) -> declty
     promise.set_exception(std::current_exception());
   }
 }
-template <class R, class F>
-XBT_ATTRIB_DEPRECATED_v323("Please use xbt::fulfill_promise()") auto fulfillPromise(R& promise, F&& code)
-    -> decltype(promise.set_value(code()))
-{
-  try {
-    promise.set_value(std::forward<F>(code)());
-  }
-  catch(...) {
-    promise.set_exception(std::current_exception());
-  }
-}
 
-template <class P, class F> auto fulfill_promise(P& promise, F&& code) -> decltype(promise.set_value())
+template <class R, class F> auto fulfill_promise(R& promise, F&& code) -> decltype(promise.set_value())
 {
   try {
     std::forward<F>(code)();
@@ -228,18 +136,6 @@ template <class P, class F> auto fulfill_promise(P& promise, F&& code) -> declty
     promise.set_exception(std::current_exception());
   }
 }
-template <class P, class F>
-XBT_ATTRIB_DEPRECATED_v323("Please use xbt::fulfill_promise()") auto fulfillPromise(P& promise, F&& code)
-    -> decltype(promise.set_value())
-{
-  try {
-    std::forward<F>(code)();
-    promise.set_value();
-  }
-  catch(...) {
-    promise.set_exception(std::current_exception());
-  }
-}
 
 /** Set a promise/result from a future/result
  *
@@ -257,12 +153,7 @@ XBT_ATTRIB_DEPRECATED_v323("Please use xbt::fulfill_promise()") auto fulfillProm
  */
 template <class P, class F> inline void set_promise(P& promise, F&& future)
 {
-  fulfill_promise(promise, [&] { return std::forward<F>(future).get(); });
-}
-template <class P, class F>
-inline XBT_ATTRIB_DEPRECATED_v323("Please use xbt::set_promise()") void setPromise(P& promise, F&& future)
-{
-  fulfill_promise(promise, [&] { return std::forward<F>(future).get(); });
+  fulfill_promise(promise, [&future] { return std::forward<F>(future).get(); });
 }
 
 }