mux_messaging.h

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#pragma once
 
#include "roo_collections.h"
#include "roo_collections/flat_small_hash_map.h"
#include "roo_transport/messaging/messaging.h"
 
namespace roo_transport {
 
/// Multiplexes up to 256 logical messaging channels over one `Messaging` link.
class MuxMessaging {
 public:
  using ChannelId = uint8_t;
 
  class Channel;
 
  MuxMessaging(Messaging& messaging);
  ~MuxMessaging();
 
 private:
  friend class Channel;
 
  class Dispatcher : public Messaging::Receiver {
   public:
    explicit Dispatcher(MuxMessaging& mux) : mux_(mux) {}
 
    void received(Messaging::ConnectionId connection_id, const roo::byte* data,
                  size_t len) override;
 
    void reset(Messaging::ConnectionId connection_id) override {
      mux_.reset(connection_id);
    }
 
   private:
    MuxMessaging& mux_;
  };
 
  /// Called by `Channel` constructor.
  void registerChannel(Channel& channel);
 
  /// Called by `Channel` destructor.
  void unregisterChannel(Channel& channel);
 
  void received(Messaging::ConnectionId connection_id, ChannelId channel_id,
                const roo::byte* data, size_t len);
 
  void reset(Messaging::ConnectionId connection_id);
 
  Messaging& messaging_;
  Dispatcher dispatcher_;
  roo_collections::FlatSmallHashMap<ChannelId, Channel*> receivers_;
};
 
class MuxMessaging::Channel : public Messaging {
 public:
  using Messaging::send;
  using Messaging::sendContinuation;
 
  Channel(MuxMessaging& messaging, ChannelId id)
      : messaging_(messaging), id_(id) {
    messaging_.registerChannel(*this);
  }
 
  ~Channel() { messaging_.unregisterChannel(*this); }
 
  bool send(const roo::byte* header, size_t header_size,
            const roo::byte* payload, size_t payload_size,
            ConnectionId* connection_id) override;
 
  bool sendContinuation(ConnectionId connection_id, const roo::byte* header,
                        size_t header_size, const roo::byte* payload,
                        size_t payload_size) override;
 
 private:
  friend class MuxMessaging;
 
  MuxMessaging& messaging_;
  ChannelId id_;
};
 
}  // namespace roo_transport