2 * Copyright 2014-present Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 #include <folly/Portability.h>
20 #include <folly/executors/InlineExecutor.h>
21 #include <folly/futures/Promise.h>
26 * SharedPromise provides the same interface as Promise, but you can extract
27 * multiple Futures from it, i.e. you can call getFuture() as many times as
28 * you'd like. When the SharedPromise is fulfilled, all of the Futures will be
29 * called back. Calls to getFuture() after the SharedPromise is fulfilled return
30 * a completed Future. If you find yourself constructing collections of Promises
31 * and fulfilling them simultaneously with the same value, consider this
32 * utility instead. Likewise, if you find yourself in need of setting multiple
33 * callbacks on the same Future (which is indefinitely unsupported), consider
34 * refactoring to use SharedPromise to "split" the Future.
39 SharedPromise() = default;
40 ~SharedPromise() = default;
43 SharedPromise(SharedPromise const&) = delete;
44 SharedPromise& operator=(SharedPromise const&) = delete;
47 SharedPromise(SharedPromise<T>&&) noexcept;
48 SharedPromise& operator=(SharedPromise<T>&&) noexcept;
51 * Return a Future tied to the shared core state. Unlike Promise::getFuture,
52 * this can be called an unlimited number of times per SharedPromise.
54 SemiFuture<T> getSemiFuture();
57 * Return a Future tied to the shared core state. Unlike Promise::getFuture,
58 * this can be called an unlimited number of times per SharedPromise.
59 * NOTE: This function is deprecated. Please use getSemiFuture and pass the
60 * appropriate executor to .via on the returned SemiFuture to get a
61 * valid Future where necessary.
63 Future<T> getFuture();
65 /** Return the number of Futures associated with this SharedPromise */
68 /** Fulfill the SharedPromise with an exception_wrapper */
69 void setException(exception_wrapper ew);
71 /** Fulfill the SharedPromise with an exception_ptr, e.g.
75 p.setException(std::current_exception());
78 FOLLY_DEPRECATED("use setException(exception_wrapper)")
79 void setException(std::exception_ptr const&);
81 /** Fulfill the SharedPromise with an exception type E, which can be passed to
82 std::make_exception_ptr(). Useful for originating exceptions. If you
83 caught an exception the exception_wrapper form is more appropriate.
86 typename std::enable_if<std::is_base_of<std::exception, E>::value>::type
87 setException(E const&);
89 /// Set an interrupt handler to handle interrupts. See the documentation for
90 /// Future::raise(). Your handler can do whatever it wants, but if you
91 /// bother to set one then you probably will want to fulfill the SharedPromise with
92 /// an exception (or special value) indicating how the interrupt was
94 void setInterruptHandler(std::function<void(exception_wrapper const&)>);
96 /// Sugar to fulfill this SharedPromise<Unit>
97 template <class B = T>
98 typename std::enable_if<std::is_same<Unit, B>::value, void>::type
103 /** Set the value (use perfect forwarding for both move and copy) */
105 void setValue(M&& value);
107 void setTry(Try<T>&& t);
109 /** Fulfill this SharedPromise with the result of a function that takes no
110 arguments and returns something implicitly convertible to T.
111 Captures exceptions. e.g.
113 p.setWith([] { do something that may throw; return a T; });
116 void setWith(F&& func);
123 bool hasValue_{false};
125 std::vector<Promise<T>> promises_;
126 std::function<void(exception_wrapper const&)> interruptHandler_;
131 #include <folly/futures/Future.h>
132 #include <folly/futures/SharedPromise-inl.h>