parameter_refresher.h

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#pragma once
 
#include <chrono>
#include <condition_variable>
#include <cstddef>
#include <cstdint>
#include <map>
#include <mutex>
#include <optional>
#include <stop_token>
#include <thread>
#include <vector>
 
namespace mm::node {
 
class DeviceManager;
 
class ParameterRefresher {
 public:
  explicit ParameterRefresher(DeviceManager& deviceManager);
 
  ~ParameterRefresher();
 
  ParameterRefresher(const ParameterRefresher&) = delete;
  ParameterRefresher& operator=(const ParameterRefresher&) = delete;
 
  void acquire(uint16_t devicePosition, uint16_t index, uint8_t subindex,
               std::chrono::milliseconds period);
 
  void release(uint16_t devicePosition, uint16_t index, uint8_t subindex);
 
  void start();
 
  void stop();
 
  std::size_t trackedCount() const;
 
  void pollDue();
 
 private:
  struct Entry {
    uint16_t devicePosition = 0;
    uint16_t index = 0;
    uint8_t subindex = 0;
    int refCount = 0;
    std::chrono::milliseconds period{};
    std::chrono::steady_clock::time_point nextDue{};  // default (epoch) => due immediately
    std::chrono::milliseconds backoff{};              // 0 until a poll fails
  };
 
  struct Drive {
    bool busy = false;
    std::chrono::steady_clock::time_point openAt{};  // default (epoch) => open
  };
 
  struct Job {
    uint64_t key = 0;
    uint16_t devicePosition = 0;
    uint16_t index = 0;
    uint8_t subindex = 0;
  };
 
  static uint64_t makeKey(uint16_t devicePosition, uint16_t index, uint8_t subindex);
 
  std::optional<Job> takeDue(std::chrono::steady_clock::time_point now,
                             std::chrono::steady_clock::time_point& wakeAt);
 
  void poll(const Job& job);
 
  void work(const std::stop_token& stopToken);
 
  DeviceManager& deviceManager_;
  mutable std::mutex mutex_;           
  std::condition_variable cv_;         
  std::map<uint64_t, Entry> entries_;  
  std::map<uint16_t, Drive> drives_;
  std::vector<std::jthread> workers_;  
};
 
}  // namespace mm::node