#include <cstddef>
-#include <utility>
#include <exception>
+#include <functional>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
namespace simgrid {
namespace xbt {
-/** A value or an exception
+/** A value or an exception (or nothing)
+ *
+ * This is similar to `optional<expected<T>>`` but it with a Future/Promise
+ * like API.
*
- * The API is similar to the one of future and promise.
+ * Also the name is not so great.
**/
template<class T>
class Result {
/** Extract the value from the future
*
- * After this the value is invalid.
+ * After this, the value is invalid.
**/
T get()
{
};
template<>
-class Result<void> : public Result<nullptr_t>
+class Result<void> : public Result<std::nullptr_t>
{
public:
void set_value()
}
void get()
{
- Result<nullptr_t>::get();
+ Result<std::nullptr_t>::get();
}
};
}
};
-/** 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(...) {
}
}
+/** 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(); });
+}
+
}
}