/*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#include <vector>
#include <folly/Optional.h>
-#include <folly/MoveWrapper.h>
-#include <folly/futures/Deprecated.h>
+#include <folly/Portability.h>
#include <folly/futures/DrivableExecutor.h>
#include <folly/futures/Promise.h>
-#include <folly/futures/Try.h>
+#include <folly/Try.h>
#include <folly/futures/FutureException.h>
#include <folly/futures/detail/Types.h>
Future(Future&&) noexcept;
Future& operator=(Future&&) noexcept;
- /// Construct a Future from a value (perfect forwarding)
- /* implicit */
- template <class T2 = T,
- typename std::enable_if<!isFuture<T2>::value, void*>::type = nullptr>
- Future(T2&& val);
+ // converting move
+ template <
+ class T2,
+ typename std::enable_if<
+ !std::is_same<T, typename std::decay<T2>::type>::value &&
+ std::is_constructible<T, T2&&>::value &&
+ std::is_convertible<T2&&, T>::value,
+ int>::type = 0>
+ /* implicit */ Future(Future<T2>&&);
+ template <
+ class T2,
+ typename std::enable_if<
+ !std::is_same<T, typename std::decay<T2>::type>::value &&
+ std::is_constructible<T, T2&&>::value &&
+ !std::is_convertible<T2&&, T>::value,
+ int>::type = 0>
+ explicit Future(Future<T2>&&);
+ template <
+ class T2,
+ typename std::enable_if<
+ !std::is_same<T, typename std::decay<T2>::type>::value &&
+ std::is_constructible<T, T2&&>::value,
+ int>::type = 0>
+ Future& operator=(Future<T2>&&);
- template <class T2 = T,
+ /// Construct a Future from a value (perfect forwarding)
+ template <class T2 = T, typename =
typename std::enable_if<
- folly::is_void_or_unit<T2>::value,
- int>::type = 0>
- Future();
+ !isFuture<typename std::decay<T2>::type>::value>::type>
+ /* implicit */ Future(T2&& val);
+
+ template <class T2 = T>
+ /* implicit */ Future(
+ typename std::enable_if<std::is_same<Unit, T2>::value>::type* = nullptr);
~Future();
// The ref-qualifier allows for `this` to be moved out so we
// don't get access-after-free situations in chaining.
// https://akrzemi1.wordpress.com/2014/06/02/ref-qualifiers/
- template <typename Executor>
- Future<T> via(Executor* executor) &&;
+ inline Future<T> via(
+ Executor* executor,
+ int8_t priority = Executor::MID_PRI) &&;
/// This variant creates a new future, where the ref-qualifier && version
/// moves `this` out. This one is less efficient but avoids confusing users
/// when "return f.via(x);" fails.
- template <typename Executor>
- Future<T> via(Executor* executor) &;
+ inline Future<T> via(
+ Executor* executor,
+ int8_t priority = Executor::MID_PRI) &;
/** True when the result (or exception) is ready. */
bool isReady() const;
+ /// sugar for getTry().hasValue()
+ bool hasValue();
+
+ /// sugar for getTry().hasException()
+ bool hasException();
+
/** A reference to the Try of the value */
Try<T>& getTry();
+ /// Call e->drive() repeatedly until the future is fulfilled. Examples
+ /// of DrivableExecutor include EventBase and ManualExecutor. Returns a
+ /// reference to the Try of the value.
+ Try<T>& getTryVia(DrivableExecutor* e);
+
/// If the promise has been fulfilled, return an Optional with the Try<T>.
/// Otherwise return an empty Optional.
/// Note that this moves the Try<T> out.
value(), which may rethrow if this has captured an exception. If func
throws, the exception will be captured in the Future that is returned.
*/
- /* TODO n3428 and other async frameworks have something like then(scheduler,
- Future), we might want to support a similar API which could be
- implemented a little more efficiently than
- f.via(executor).then(callback) */
- template <typename F, typename R = detail::callableResult<T, F>>
- typename R::Return then(F func) {
+ // gcc 4.8 requires that we cast function reference types to function pointer
+ // types. Fore more details see the comment on FunctionReferenceToPointer
+ // in Future-pre.h.
+ // gcc versions 4.9 and above (as well as clang) do not require this hack.
+ // For those, the FF tenplate parameter can be removed and occurences of FF
+ // replaced with F.
+ template <
+ typename F,
+ typename FF = typename detail::FunctionReferenceToPointer<F>::type,
+ typename R = detail::callableResult<T, FF>>
+ typename R::Return then(F&& func) {
typedef typename R::Arg Arguments;
- return thenImplementation<F, R>(std::move(func), Arguments());
+ return thenImplementation<FF, R>(std::forward<FF>(func), Arguments());
}
/// Variant where func is an member function
Future<typename isFuture<R>::Inner>
then(R(Caller::*func)(Args...), Caller *instance);
-// TODO(6838553)
-#ifndef __clang__
/// Execute the callback via the given Executor. The executor doesn't stick.
///
/// Contrast
///
/// In the former both b and c execute via x. In the latter, only b executes
/// via x, and c executes via the same executor (if any) that f had.
- template <class... Args>
- auto then(Executor* x, Args&&... args)
- -> decltype(this->then(std::forward<Args>(args)...));
-#endif
+ template <class Executor, class Arg, class... Args>
+ auto then(Executor* x, Arg&& arg, Args&&... args) {
+ auto oldX = getExecutor();
+ setExecutor(x);
+ return this->then(std::forward<Arg>(arg), std::forward<Args>(args)...)
+ .via(oldX);
+ }
- /// Convenience method for ignoring the value and creating a Future<void>.
+ /// Convenience method for ignoring the value and creating a Future<Unit>.
/// Exceptions still propagate.
- Future<void> then();
+ Future<Unit> then();
/// Set an error callback for this Future. The callback should take a single
/// argument of the type that you want to catch, and should return a value of
/// func shouldn't throw, but if it does it will be captured and propagated,
/// and discard any value/exception that this Future has obtained.
template <class F>
- Future<T> ensure(F func);
+ Future<T> ensure(F&& func);
/// Like onError, but for timeouts. example:
///
/// by then), and it is active (active by default).
///
/// Inactive Futures will activate upon destruction.
- Future<T>& activate() & {
+ FOLLY_DEPRECATED("do not use") Future<T>& activate() & {
core_->activate();
return *this;
}
- Future<T>& deactivate() & {
+ FOLLY_DEPRECATED("do not use") Future<T>& deactivate() & {
core_->deactivate();
return *this;
}
- Future<T> activate() && {
+ FOLLY_DEPRECATED("do not use") Future<T> activate() && {
core_->activate();
return std::move(*this);
}
- Future<T> deactivate() && {
+ FOLLY_DEPRECATED("do not use") Future<T> deactivate() && {
core_->deactivate();
return std::move(*this);
}
template <class E>
void raise(E&& exception) {
raise(make_exception_wrapper<typename std::remove_reference<E>::type>(
- std::move(exception)));
+ std::forward<E>(exception)));
}
/// Raise an interrupt. If the promise holder has an interrupt
/// If the predicate does not obtain with the value, the result
/// is a folly::PredicateDoesNotObtain exception
template <class F>
- Future<T> filter(F predicate);
+ Future<T> filter(F&& predicate);
+
+ /// Like reduce, but works on a Future<std::vector<T / Try<T>>>, for example
+ /// the result of collect or collectAll
+ template <class I, class F>
+ Future<I> reduce(I&& initial, F&& func);
+
+ /// Create a Future chain from a sequence of callbacks. i.e.
+ ///
+ /// f.then(a).then(b).then(c)
+ ///
+ /// where f is a Future<A> and the result of the chain is a Future<D>
+ /// becomes
+ ///
+ /// f.thenMulti(a, b, c);
+ template <class Callback, class... Callbacks>
+ auto thenMulti(Callback&& fn, Callbacks&&... fns) {
+ // thenMulti with two callbacks is just then(a).thenMulti(b, ...)
+ return then(std::forward<Callback>(fn))
+ .thenMulti(std::forward<Callbacks>(fns)...);
+ }
+
+ template <class Callback>
+ auto thenMulti(Callback&& fn) {
+ // thenMulti with one callback is just a then
+ return then(std::forward<Callback>(fn));
+ }
+
+ /// Create a Future chain from a sequence of callbacks. i.e.
+ ///
+ /// f.via(executor).then(a).then(b).then(c).via(oldExecutor)
+ ///
+ /// where f is a Future<A> and the result of the chain is a Future<D>
+ /// becomes
+ ///
+ /// f.thenMultiWithExecutor(executor, a, b, c);
+ template <class Callback, class... Callbacks>
+ auto thenMultiWithExecutor(Executor* x, Callback&& fn, Callbacks&&... fns) {
+ // thenMultiExecutor with two callbacks is
+ // via(x).then(a).thenMulti(b, ...).via(oldX)
+ auto oldX = getExecutor();
+ setExecutor(x);
+ return then(std::forward<Callback>(fn))
+ .thenMulti(std::forward<Callbacks>(fns)...)
+ .via(oldX);
+ }
+
+ template <class Callback>
+ auto thenMultiWithExecutor(Executor* x, Callback&& fn) {
+ // thenMulti with one callback is just a then with an executor
+ return then(x, std::forward<Callback>(fn));
+ }
+
+ /// Discard a result, but propagate an exception.
+ Future<Unit> unit() {
+ return then([]{ return Unit{}; });
+ }
protected:
typedef detail::Core<T>* corePtr;
friend class Promise<T>;
template <class> friend class Future;
+ template <class T2>
+ friend Future<T2> makeFuture(Try<T2>&&);
+
+ /// Repeat the given future (i.e., the computation it contains)
+ /// n times.
+ ///
+ /// thunk behaves like std::function<Future<T2>(void)>
+ template <class F>
+ friend Future<Unit> times(int n, F&& thunk);
+
+ /// Carry out the computation contained in the given future if
+ /// the predicate holds.
+ ///
+ /// thunk behaves like std::function<Future<T2>(void)>
+ template <class F>
+ friend Future<Unit> when(bool p, F&& thunk);
+
+ /// Carry out the computation contained in the given future if
+ /// while the predicate continues to hold.
+ ///
+ /// thunk behaves like std::function<Future<T2>(void)>
+ ///
+ /// predicate behaves like std::function<bool(void)>
+ template <class P, class F>
+ friend Future<Unit> whileDo(P&& predicate, F&& thunk);
+
// Variant: returns a value
// e.g. f.then([](Try<T> t){ return t.value(); });
template <typename F, typename R, bool isTry, typename... Args>
typename std::enable_if<!R::ReturnsFuture::value, typename R::Return>::type
- thenImplementation(F func, detail::argResult<isTry, F, Args...>);
+ thenImplementation(F&& func, detail::argResult<isTry, F, Args...>);
// Variant: returns a Future
// e.g. f.then([](Try<T> t){ return makeFuture<T>(t); });
template <typename F, typename R, bool isTry, typename... Args>
typename std::enable_if<R::ReturnsFuture::value, typename R::Return>::type
- thenImplementation(F func, detail::argResult<isTry, F, Args...>);
+ thenImplementation(F&& func, detail::argResult<isTry, F, Args...>);
Executor* getExecutor() { return core_->getExecutor(); }
- void setExecutor(Executor* x) { core_->setExecutor(x); }
+ void setExecutor(Executor* x, int8_t priority = Executor::MID_PRI) {
+ core_->setExecutor(x, priority);
+ }
};
-
} // folly
#include <folly/futures/Future-inl.h>
projects / folly.git / blobdiff