aos/events/raw-event-loop.h

#ifndef _AOS_EVENTS_RAW_EVENT_LOOP_H_
#define _AOS_EVENTS_RAW_EVENT_LOOP_H_

#include <atomic>
#include <memory>
#include <string>
#include "aos/common/queue.h"
#include "aos/common/time.h"

// This file contains raw versions of the classes in event-loop.h.
//
// Users should look exclusively at event-loop.h. Only people who wish to
// implement a new IPC layer (like a fake layer for example) may wish to use
// these classes.
namespace aos {

// Raw version of fetcher. Contains a local variable that the fetcher will
// update.
// It is the job of the typed version to cast this to the appropriate type.
class RawFetcher {
 public:
  class FetchValue;
  RawFetcher() {}
  virtual ~RawFetcher() {}

  virtual bool Fetch() = 0;

  const FetchValue *most_recent() { return most_recent_; }

 protected:
  RawFetcher(const RawFetcher &) = delete;
  RawFetcher &operator=(const RawFetcher &) = delete;
  void set_most_recent(const FetchValue *most_recent) {
    most_recent_ = most_recent;
  }

 private:
  const FetchValue *most_recent_ = nullptr;
};

// Raw version of sender. Sending a message is a 3 part process. Fetch an opaque
// token, cast that token to the message type, populate and then calling one of
// Send() or Free().
class RawSender {
 public:
  class SendContext;

  RawSender() {}
  virtual ~RawSender() {}

  virtual SendContext *GetContext() = 0;

  virtual void Free(SendContext *context) = 0;

  virtual bool Send(SendContext *context) = 0;

  // Call operator that calls Free().
  template <typename T>
  void operator()(T *t) {
    Free(reinterpret_cast<SendContext *>(t));
  }

 protected:
  RawSender(const RawSender &) = delete;
  RawSender &operator=(const RawSender &) = delete;
};

// Opaque Information extracted from a particular type passed to the underlying
// system so that it knows how much memory to allocate etc.
struct QueueTypeInfo {
  // Message size:
  size_t size;
  // This should be a globally unique identifier for the type.
  int hash;
  // Config parameter for how long the queue should be.
  int queue_length;

  template <typename T>
  static QueueTypeInfo Get() {
    QueueTypeInfo info;
    info.size = sizeof(T);
    info.hash = T::kHash;
    info.queue_length = T::kQueueLength;
    return info;
  }
};

// Virtual base class for all event queue-types.
class RawEventLoop {
 public:
  virtual ~RawEventLoop() {}

  // Current time.
  virtual monotonic_clock::time_point monotonic_now() = 0;

  // The passed in function will be called when the event loop starts.
  // Use this to run code once the thread goes into "real-time-mode",
  virtual void OnRun(std::function<void()> on_run) = 0;

  bool is_running() const { return is_running_.load(); }

  // Starts receiving events.
  virtual void Run() = 0;

  // Stops receiving events.
  virtual void Exit() = 0;

 protected:
  void set_is_running(bool value) { is_running_.store(value); }

  // Will send new messages from (path, type).
  virtual std::unique_ptr<RawSender> MakeRawSender(
      const std::string &path, const QueueTypeInfo &type) = 0;

  // Will fetch new messages from (path, type).
  virtual std::unique_ptr<RawFetcher> MakeRawFetcher(
      const std::string &path, const QueueTypeInfo &type) = 0;

  // Will watch (path, type) for new messages
  virtual void MakeRawWatcher(
      const std::string &path, const QueueTypeInfo &type,
      std::function<void(const Message *message)> watcher) = 0;

 private:
  std::atomic<bool> is_running_{false};
};

}  // namespace aos

#endif  // _AOS_EVENTS_RAW_EVENT_LOOP_H_