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April 9, 2022 16:52
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promise_future
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/** | |
* Licensed to the Apache Software Foundation (ASF) under one | |
* or more contributor license agreements. See the NOTICE file | |
* distributed with this work for additional information | |
* regarding copyright ownership. The ASF licenses this file | |
* to you under the Apache License, Version 2.0 (the | |
* "License"); you may not use this file except in compliance | |
* with the License. You may obtain a copy of the License at | |
* | |
* http://www.apache.org/licenses/LICENSE-2.0 | |
* | |
* Unless required by applicable law or agreed to in writing, | |
* software distributed under the License is distributed on an | |
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | |
* KIND, either express or implied. See the License for the | |
* specific language governing permissions and limitations | |
* under the License. | |
*/ | |
#ifndef LIB_FUTURE_H_ | |
#define LIB_FUTURE_H_ | |
#include <functional> | |
#include <mutex> | |
#include <memory> | |
#include <condition_variable> | |
#include <list> | |
typedef std::unique_lock<std::mutex> Lock; | |
namespace pulsar { | |
template <typename Result, typename Type> | |
struct InternalState { | |
std::mutex mutex; | |
std::condition_variable condition; | |
Result result; | |
Type value; | |
bool complete; | |
std::list<typename std::function<void(Result, const Type&)> > listeners; | |
}; | |
template <typename Result, typename Type> | |
class Future { | |
public: | |
typedef std::function<void(Result, const Type&)> ListenerCallback; | |
Future& addListener(ListenerCallback callback) { | |
InternalState<Result, Type>* state = state_.get(); | |
Lock lock(state->mutex); | |
if (state->complete) { | |
lock.unlock(); | |
callback(state->result, state->value); | |
} else { | |
state->listeners.push_back(callback); | |
} | |
return *this; | |
} | |
Result get(Type& result) { | |
InternalState<Result, Type>* state = state_.get(); | |
Lock lock(state->mutex); | |
if (!state->complete) { | |
// Wait for result | |
while (!state->complete) { | |
state->condition.wait(lock); | |
} | |
} | |
result = state->value; | |
return state->result; | |
} | |
private: | |
typedef std::shared_ptr<InternalState<Result, Type> > InternalStatePtr; | |
Future(InternalStatePtr state) : state_(state) {} | |
std::shared_ptr<InternalState<Result, Type> > state_; | |
template <typename U, typename V> | |
friend class Promise; | |
}; | |
template <typename Result, typename Type> | |
class Promise { | |
public: | |
Promise() : state_(std::make_shared<InternalState<Result, Type> >()) {} | |
bool setValue(const Type& value) const { | |
static Result DEFAULT_RESULT; | |
InternalState<Result, Type>* state = state_.get(); | |
Lock lock(state->mutex); | |
if (state->complete) { | |
return false; | |
} | |
state->value = value; | |
state->result = DEFAULT_RESULT; | |
state->complete = true; | |
decltype(state->listeners) listeners; | |
listeners.swap(state->listeners); | |
lock.unlock(); | |
for (auto& callback : listeners) { | |
callback(DEFAULT_RESULT, value); | |
} | |
state->condition.notify_all(); | |
return true; | |
} | |
bool setFailed(Result result) const { | |
static Type DEFAULT_VALUE; | |
InternalState<Result, Type>* state = state_.get(); | |
Lock lock(state->mutex); | |
if (state->complete) { | |
return false; | |
} | |
state->result = result; | |
state->complete = true; | |
decltype(state->listeners) listeners; | |
listeners.swap(state->listeners); | |
lock.unlock(); | |
for (auto& callback : listeners) { | |
callback(result, DEFAULT_VALUE); | |
} | |
state->condition.notify_all(); | |
return true; | |
} | |
bool isComplete() const { | |
InternalState<Result, Type>* state = state_.get(); | |
Lock lock(state->mutex); | |
return state->complete; | |
} | |
Future<Result, Type> getFuture() const { return Future<Result, Type>(state_); } | |
private: | |
typedef std::function<void(Result, const Type&)> ListenerCallback; | |
std::shared_ptr<InternalState<Result, Type> > state_; | |
}; | |
class Void {}; | |
} /* namespace pulsar */ | |
#endif /* LIB_FUTURE_H_ */ |
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Extracted from https://raw.githubusercontent.com/apache/pulsar/master/pulsar-client-cpp/lib/Future.h
All copyrights belongs to pulsar.