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// Copyright (C) 2019 The Android Open Source Project
//
// Licensed 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 IORAP_SRC_COMMON_ASYNC_POOL_H_
#define IORAP_SRC_COMMON_ASYNC_POOL_H_
#include <atomic>
#include <vector>
#include <deque>
#include <future>
#include <condition_variable>
#include <future>
namespace iorap::common {
class AsyncPool {
std::atomic<bool> shutting_down_{false};
std::deque<std::future<void>> futures_;
std::mutex mutex_;
std::condition_variable cond_var_;
public:
// Any threads calling 'Join' should eventually unblock
// once all functors have run to completition.
void Shutdown() {
shutting_down_ = true;
cond_var_.notify_all();
}
// Block forever until Shutdown is called *and* all
// functors passed to 'LaunchAsync' have run to completition.
void Join() {
std::unique_lock<std::mutex> lock(mutex_);
while (true) {
// Pop all items eagerly
while (true) {
auto it = futures_.begin();
if (it == futures_.end()) {
break;
}
std::future<void> future = std::move(*it);
futures_.pop_front();
lock.unlock(); // do not stall callers of LaunchAsync
future.get();
lock.lock();
}
if (shutting_down_) {
break;
}
// Wait until we either get more items or ask to be shutdown.
cond_var_.wait(lock);
}
}
// Execute the functor 'u' in a new thread asynchronously.
// Using this spawns a new thread each time to immediately begin
// async execution.
template <typename T>
void LaunchAsync(T&& u) {
auto future = std::async(std::launch::async, std::forward<T>(u));
{
std::unique_lock<std::mutex> lock(mutex_);
futures_.push_back(std::move(future));
}
cond_var_.notify_one();
}
};
} // namespace iorap::common
#endif // IORAP_SRC_COMMON_ASYNC_POOL_H_
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