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#pragma once
#include <mbgl/actor/mailbox.hpp>
#include <mbgl/actor/scheduler.hpp>
#include <array>
#include <condition_variable>
#include <mutex>
#include <queue>
#include <thread>
namespace mbgl {
class ThreadedSchedulerBase : public Scheduler {
public:
void schedule(std::function<void()>) override;
protected:
ThreadedSchedulerBase() = default;
~ThreadedSchedulerBase() override;
void terminate();
std::thread makeSchedulerThread(size_t index);
std::queue<std::function<void()>> queue;
std::mutex mutex;
std::condition_variable cv;
bool terminated{false};
};
/**
* @brief ThreadScheduler implements Scheduler interface using a lightweight event loop
*
* @tparam N number of threads
*
* Note: If N == 1 all scheduled tasks are guaranteed to execute consequently;
* otherwise, some of the scheduled tasks might be executed in parallel.
*/
template <std::size_t N>
class ThreadedScheduler : public ThreadedSchedulerBase {
public:
ThreadedScheduler() {
for (std::size_t i = 0u; i < N; ++i) {
threads[i] = makeSchedulerThread(i);
}
}
~ThreadedScheduler() override {
terminate();
for (auto& thread : threads) {
thread.join();
}
}
mapbox::base::WeakPtr<Scheduler> makeWeakPtr() override { return weakFactory.makeWeakPtr(); }
private:
std::array<std::thread, N> threads;
mapbox::base::WeakPtrFactory<Scheduler> weakFactory{this};
static_assert(N > 0, "Thread count must be more than zero.");
};
using SequencedScheduler = ThreadedScheduler<1>;
template <std::size_t extra>
using ParallelScheduler = ThreadedScheduler<1 + extra>;
using ThreadPool = ParallelScheduler<3>;
} // namespace mbgl
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