X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/d841c4b43a5fb8d004b34ba52a3bf4407faf6810..b32b5a8d04e1b7a68b68f947aa2cc4e7316ba0e6:/include/xbt/future.hpp

diff --git a/include/xbt/future.hpp b/include/xbt/future.hpp
index d583c34509..55abdc7db3 100644
--- a/include/xbt/future.hpp
+++ b/include/xbt/future.hpp
@@ -1,4 +1,4 @@
-/* Copyright (c) 2015-2016. The SimGrid Team.
+/* Copyright (c) 2015-2017. The SimGrid Team.
  * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
@@ -9,15 +9,22 @@
 
 #include <cstddef>
 
-#include <utility>
 #include <exception>
+#include <functional>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+#include <xbt/ex.h>
 
 namespace simgrid {
 namespace xbt {
 
-/** A value or an exception
+/** A value or an exception (or nothing)
  *
- *  The API is similar to the one of future and promise.
+ *  This is similar to `optional<expected<T>>`` but it with a Future/Promise
+ *  like API.
+ *
+ *  Also the name is not so great.
  **/
 template<class T>
 class Result {
@@ -27,7 +34,7 @@ class Result {
     exception,
   };
 public:
-  Result() {}
+  Result() { /* Nothing to do */}
   ~Result() { this->reset(); }
 
   // Copy (if T is copyable) and move:
@@ -41,12 +48,14 @@ public:
     switch (that.status_) {
       case ResultStatus::invalid:
         break;
-      case ResultStatus::valid:
+      case ResultStatus::value:
         new (&value_) T(that.value);
         break;
       case ResultStatus::exception:
         new (&exception_) T(that.exception);
         break;
+      default:
+        THROW_IMPOSSIBLE;
     }
     return *this;
   }
@@ -60,7 +69,7 @@ public:
     switch (that.status_) {
       case ResultStatus::invalid:
         break;
-      case ResultStatus::valid:
+      case ResultStatus::value:
         new (&value_) T(std::move(that.value));
         that.value.~T();
         break;
@@ -68,18 +77,20 @@ public:
         new (&exception_) T(std::move(that.exception));
         that.exception.~exception_ptr();
         break;
+      default:
+        THROW_IMPOSSIBLE;
     }
     that.status_ = ResultStatus::invalid;
     return *this;
   }
 
-  bool is_valid()
+  bool is_valid() const
   {
     return status_ != ResultStatus::invalid;
   }
   void reset()
   {
-    switch(status_) {
+    switch (status_) {
       case ResultStatus::invalid:
         break;
       case ResultStatus::value:
@@ -88,6 +99,8 @@ public:
       case ResultStatus::exception:
         exception_.~exception_ptr();
         break;
+      default:
+        THROW_IMPOSSIBLE;
     }
     status_ = ResultStatus::invalid;
   }
@@ -112,14 +125,11 @@ public:
 
   /** Extract the value from the future
    *
-   *  After this the value is invalid.
+   *  After this, the value is invalid.
    **/
   T get()
   {
-    switch(status_) {
-      case ResultStatus::invalid:
-      default:
-        throw std::logic_error("Invalid result");
+    switch (status_) {
       case ResultStatus::value: {
         T value = std::move(value_);
         value_.~T();
@@ -133,6 +143,8 @@ public:
         std::rethrow_exception(std::move(exception));
         break;
       }
+      default:
+        throw std::logic_error("Invalid result");
     }
   }
 private:
@@ -144,7 +156,7 @@ private:
 };
 
 template<>
-class Result<void> : public Result<nullptr_t>
+class Result<void> : public Result<std::nullptr_t>
 {
 public:
   void set_value()
@@ -153,7 +165,7 @@ public:
   }
   void get()
   {
-    Result<nullptr_t>::get();
+    Result<std::nullptr_t>::get();
   }
 };
 
@@ -171,30 +183,40 @@ public:
   }
 };
 
-/** Fulfill a promise by executing a given code */
+/** Execute some code and set a promise or result accordingly
+ *
+ *  Roughly this does:
+ *
+ *  <pre>
+ *  promise.set_value(code());
+ *  </pre>
+ *
+ *  but it takes care of exceptions and works with `void`.
+ *
+ *  We might need this when working with generic code because
+ *  the trivial implementation does not work with `void` (before C++1z).
+ *
+ *  @param    code  What we want to do
+ *  @param  promise Where to want to store the result
+ */
 template<class R, class F>
 auto fulfillPromise(R& promise, F&& code)
 -> decltype(promise.set_value(code()))
 {
   try {
-    promise.set_value(code());
+    promise.set_value(std::forward<F>(code)());
   }
   catch(...) {
     promise.set_exception(std::current_exception());
   }
 }
 
-/** Fulfill a promise by executing a given code
- *
- *  This is a special version for `std::promise<void>` because the default
- *  version does not compile in this case.
- */
 template<class P, class F>
 auto fulfillPromise(P& promise, F&& code)
 -> decltype(promise.set_value())
 {
   try {
-    (code)();
+    std::forward<F>(code)();
     promise.set_value();
   }
   catch(...) {
@@ -202,6 +224,26 @@ auto fulfillPromise(P& promise, F&& code)
   }
 }
 
+/** Set a promise/result from a future/result
+ *
+ *  Roughly this does:
+ *
+ *  <pre>promise.set_value(future);</pre>
+ *
+ *  but it takes care of exceptions and works with `void`.
+ *
+ *  We might need this when working with generic code because
+ *  the trivial implementation does not work with `void` (before C++1z).
+ *
+ *  @param promise output (a valid future or a result)
+ *  @param future  input (a ready/waitable future or a valid result)
+ */
+template<class P, class F> inline
+void setPromise(P& promise, F&& future)
+{
+  fulfillPromise(promise, [&]{ return std::forward<F>(future).get(); });
+}
+
 }
 }