/*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2016 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 <stdexcept>
#include <vector>
+#include <folly/Executor.h>
+#include <folly/Function.h>
+#include <folly/MicroSpinLock.h>
#include <folly/Optional.h>
-#include <folly/SmallLocks.h>
-
-#include <folly/futures/Try.h>
-#include <folly/futures/Promise.h>
#include <folly/futures/Future.h>
-#include <folly/Executor.h>
+#include <folly/futures/Promise.h>
+#include <folly/futures/Try.h>
#include <folly/futures/detail/FSM.h>
#include <folly/io/async/Request.h>
/// time there won't be any problems.
template<typename T>
class Core {
+ static_assert(!std::is_void<T>::value,
+ "void futures are not supported. Use Unit instead.");
public:
/// This must be heap-constructed. There's probably a way to enforce that in
/// code but since this is just internal detail code and I don't know how
/// off-hand, I'm punting.
- Core() {}
+ Core() : result_(), fsm_(State::Start), attached_(2) {}
explicit Core(Try<T>&& t)
: result_(std::move(t)),
Core(Core&&) noexcept = delete;
Core& operator=(Core&&) = delete;
+ // Core is assumed to be convertible only if the type is convertible
+ // and the size is the same. This is a compromise for the complexity
+ // of having to make Core truly have a conversion constructor which
+ // would cause various other problems.
+ // If we made Core move constructible then we would need to update the
+ // Promise and Future with the location of the new Core. This is complex
+ // and may be inefficient.
+ // Core should only be modified so that for size(T) == size(U),
+ // sizeof(Core<T>) == size(Core<U>).
+ // This assumption is used as a proxy to make sure that
+ // the members of Core<T> and Core<U> line up so that we can use a
+ // reinterpret cast.
+ template <
+ class U,
+ typename = typename std::enable_if<std::is_convertible<U, T>::value &&
+ sizeof(U) == sizeof(T)>::type>
+ static Core<T>* convert(Core<U>* from) {
+ return reinterpret_cast<Core<T>*>(from);
+ }
+
/// May call from any thread
bool hasResult() const {
switch (fsm_.getState()) {
}
}
- template <typename F>
- class LambdaBufHelper {
- public:
- explicit LambdaBufHelper(F&& func) : func_(std::forward<F>(func)) {}
- void operator()(Try<T>&& t) {
- SCOPE_EXIT { this->~LambdaBufHelper(); };
- func_(std::move(t));
- }
- private:
- F func_;
- };
-
/// Call only from Future thread.
template <typename F>
- void setCallback(F func) {
+ void setCallback(F&& func) {
bool transitionToArmed = false;
auto setCallback_ = [&]{
context_ = RequestContext::saveContext();
-
- // Move the lambda into the Core if it fits
- if (sizeof(LambdaBufHelper<F>) <= lambdaBufSize) {
- auto funcLoc = static_cast<LambdaBufHelper<F>*>((void*)lambdaBuf_);
- new (funcLoc) LambdaBufHelper<F>(std::forward<F>(func));
- callback_ = std::ref(*funcLoc);
- } else {
- callback_ = std::move(func);
- }
+ callback_ = std::forward<F>(func);
};
FSM_START(fsm_)
// detachPromise() and setResult() should never be called in parallel
// so we don't need to protect this.
if (UNLIKELY(!result_)) {
- setResult(Try<T>(exception_wrapper(BrokenPromise())));
+ setResult(Try<T>(exception_wrapper(BrokenPromise(typeid(T).name()))));
}
detachOne();
}
}
void doCallback() {
- RequestContext::setContext(context_);
-
Executor* x = executor_;
int8_t priority;
if (x) {
executorLock_.unlock();
}
+ // keep Core alive until callback did its thing
+ ++attached_;
+
if (x) {
- // keep Core alive until executor did its thing
- ++attached_;
try {
if (LIKELY(x->getNumPriorities() == 1)) {
x->add([this]() mutable {
SCOPE_EXIT { detachOne(); };
+ RequestContext::setContext(context_);
+ SCOPE_EXIT { callback_ = {}; };
callback_(std::move(*result_));
});
} else {
x->addWithPriority([this]() mutable {
SCOPE_EXIT { detachOne(); };
+ RequestContext::setContext(context_);
+ SCOPE_EXIT { callback_ = {}; };
callback_(std::move(*result_));
}, priority);
}
} catch (...) {
+ --attached_; // Account for extra ++attached_ before try
+ RequestContext::setContext(context_);
result_ = Try<T>(exception_wrapper(std::current_exception()));
+ SCOPE_EXIT { callback_ = {}; };
callback_(std::move(*result_));
}
} else {
+ SCOPE_EXIT { detachOne(); };
+ RequestContext::setContext(context_);
+ SCOPE_EXIT { callback_ = {}; };
callback_(std::move(*result_));
}
}
}
}
- // lambdaBuf occupies exactly one cache line
- static constexpr size_t lambdaBufSize = 8 * sizeof(void*);
- char lambdaBuf_[lambdaBufSize];
+ // Core should only be modified so that for size(T) == size(U),
+ // sizeof(Core<T>) == size(Core<U>).
+ // See Core::convert for details.
+
+ folly::Function<
+ void(Try<T>&&),
+ folly::FunctionMoveCtor::MAY_THROW,
+ 8 * sizeof(void*)>
+ callback_;
// place result_ next to increase the likelihood that the value will be
// contained entirely in one cache line
- folly::Optional<Try<T>> result_ {};
- std::function<void(Try<T>&&)> callback_ {nullptr};
- FSM<State> fsm_ {State::Start};
- std::atomic<unsigned char> attached_ {2};
+ folly::Optional<Try<T>> result_;
+ FSM<State> fsm_;
+ std::atomic<unsigned char> attached_;
std::atomic<bool> active_ {true};
std::atomic<bool> interruptHandlerSet_ {false};
folly::MicroSpinLock interruptLock_ {0};
p.setException(std::move(t.exception()));
}
} else if (!threw) {
- std::get<I>(results) = std::move(t.value());
+ std::get<I>(results) = std::move(t);
}
}
~CollectVariadicContext() {
if (!threw.exchange(true)) {
- p.setValue(std::move(results));
+ p.setValue(unwrap(std::move(results)));
}
}
Promise<std::tuple<Ts...>> p;
- std::tuple<Ts...> results;
- std::atomic<bool> threw;
+ std::tuple<folly::Try<Ts>...> results;
+ std::atomic<bool> threw {false};
typedef Future<std::tuple<Ts...>> type;
+
+ private:
+ template <typename... Ts2>
+ static std::tuple<Ts...> unwrap(std::tuple<folly::Try<Ts>...>&& o,
+ Ts2&&... ts2) {
+ static_assert(sizeof...(ts2) <
+ std::tuple_size<std::tuple<folly::Try<Ts>...>>::value,
+ "Non-templated unwrap should be used instead");
+ assert(std::get<sizeof...(ts2)>(o).hasValue());
+
+ return unwrap(std::move(o),
+ std::forward<Ts2>(ts2)...,
+ std::move(*std::get<sizeof...(ts2)>(o)));
+ }
+
+ static std::tuple<Ts...> unwrap(std::tuple<folly::Try<Ts>...>&& /* o */,
+ Ts&&... ts) {
+ return std::tuple<Ts...>(std::forward<Ts>(ts)...);
+ }
};
-template <template <typename ...> class T, typename... Ts>
-void collectVariadicHelper(const std::shared_ptr<T<Ts...>>& ctx) {
+template <template <typename...> class T, typename... Ts>
+void collectVariadicHelper(const std::shared_ptr<T<Ts...>>& /* ctx */) {
// base case
}
projects / folly.git / blobdiff