1 /* Copyright (c) 2015-2016. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
18 /** A value or an exception
20 * The API is similar to the one of future and promise.
24 enum class ResultStatus {
31 ~Result() { this->reset(); }
33 // Copy (if T is copyable) and move:
34 Result(Result const& that)
38 Result& operator=(Result const& that)
41 switch (that.status_) {
42 case ResultStatus::invalid:
44 case ResultStatus::valid:
45 new (&value_) T(that.value);
47 case ResultStatus::exception:
48 new (&exception_) T(that.exception);
55 *this = std::move(that);
57 Result& operator=(Result&& that)
60 switch (that.status_) {
61 case ResultStatus::invalid:
63 case ResultStatus::valid:
64 new (&value_) T(std::move(that.value));
67 case ResultStatus::exception:
68 new (&exception_) T(std::move(that.exception));
69 that.exception.~exception_ptr();
72 that.status_ = ResultStatus::invalid;
78 return status_ != ResultStatus::invalid;
83 case ResultStatus::invalid:
85 case ResultStatus::value:
88 case ResultStatus::exception:
89 exception_.~exception_ptr();
92 status_ = ResultStatus::invalid;
94 void set_exception(std::exception_ptr e)
97 new (&exception_) std::exception_ptr(std::move(e));
98 status_ = ResultStatus::exception;
100 void set_value(T&& value)
103 new (&value_) T(std::move(value));
104 status_ = ResultStatus::value;
106 void set_value(T const& value)
109 new (&value_) T(value);
110 status_ = ResultStatus::value;
113 /** Extract the value from the future
115 * After this the value is invalid.
120 case ResultStatus::invalid:
122 throw std::logic_error("Invalid result");
123 case ResultStatus::value: {
124 T value = std::move(value_);
126 status_ = ResultStatus::invalid;
127 return std::move(value);
129 case ResultStatus::exception: {
130 std::exception_ptr exception = std::move(exception_);
131 exception_.~exception_ptr();
132 status_ = ResultStatus::invalid;
133 std::rethrow_exception(std::move(exception));
139 ResultStatus status_ = ResultStatus::invalid;
142 std::exception_ptr exception_;
147 class Result<void> : public Result<nullptr_t>
152 Result<std::nullptr_t>::set_value(nullptr);
156 Result<nullptr_t>::get();
161 class Result<T&> : public Result<std::reference_wrapper<T>>
164 void set_value(T& value)
166 Result<std::reference_wrapper<T>>::set_value(std::ref(value));
170 return Result<std::reference_wrapper<T>>::get();
174 /** Fulfill a promise by executing a given code */
175 template<class R, class F>
176 auto fulfillPromise(R& promise, F&& code)
177 -> decltype(promise.set_value(code()))
180 promise.set_value(code());
183 promise.set_exception(std::current_exception());
187 /** Fulfill a promise by executing a given code
189 * This is a special version for `std::promise<void>` because the default
190 * version does not compile in this case.
192 template<class P, class F>
193 auto fulfillPromise(P& promise, F&& code)
194 -> decltype(promise.set_value())
201 promise.set_exception(std::current_exception());