pausable_thread_loop.hpp

 
#pragma once
 
#include <atomic>
#include <cstdint>
#include <functional>
#include <thread>
 
#include <rapidsmpf/utils.hpp>
 
namespace rapidsmpf::detail {
class PausableThreadLoop {
  public:
    PausableThreadLoop(
        std::function<void()> func, Duration sleep = std::chrono::seconds{0}
    );
    ~PausableThreadLoop() noexcept;
 
    [[nodiscard]] bool is_running() const noexcept;
 
    void pause_nb() noexcept;
 
    void pause() noexcept;
 
    bool resume() noexcept;
 
    bool stop() noexcept;
 
  private:
    enum State : std::uint8_t {
        Stopped,  
        Stopping,  
        Paused,  
        Pausing,  
        Running,  
    };
 
    // State transition matrix:
    // | cur_state |         |          | nxt_state |          |         || Ops     |
    // |           |---------|----------|-----------|----------|---------||         |
    // |           | STOPPED | STOPPING | PAUSED    | PAUSING  | RUNNING ||---------|
    // |-----------|---------|----------|-----------|----------|---------|| e_loop  |
    // | STOPPED   | no_op   | X        | X         | X        | X       || pause   |
    // | STOPPING  | e_loop  | no_op    | X         | X        | X       || resume  |
    // | PAUSED    | X       | stop     | no_op     | X        | resume  || stop    |
    // | PAUSING   | e_loop  | stop     | e_loop    | no_op    | resume  || no_op   |
    // | RUNNING   | X       | stop     | X         | pause    | no_op   || X       |
    //
    // pause():
    //  RUNNING -> PAUSING
    // stop():
    //  RUNNING -> STOPPING | PAUSING -> STOPPING | PAUSED -> STOPPING
    // resume():
    //  PAUSING -> RUNNING | PAUSED -> RUNNING
    // automatic transition via event loop:
    //  PAUSING -> PAUSED
    //  STOPPING -> STOPPED
 
    std::thread thread_;
    std::atomic<State> state_{State::Paused};
};
 
}  // namespace rapidsmpf::detail