Add support for both split and combined timestamp channels
In order to handle simulation sending messages as fast as possible, and
messages sent infrequently with timestamps delivered, we want to split
each channel's RemoteMessage timestamps into a separate channel.
Start by creating a class to sort out which one is which reliably, and
start by using and testing it in message_bridge.
Change-Id: I5d279836146a01f5d403f597e59d330440fe702c
diff --git a/aos/network/timestamp_channel.h b/aos/network/timestamp_channel.h
new file mode 100644
index 0000000..b62c5e9
--- /dev/null
+++ b/aos/network/timestamp_channel.h
@@ -0,0 +1,50 @@
+#ifndef AOS_NETWORK_TIMESTAMP_CHANNEL_
+#define AOS_NETWORK_TIMESTAMP_CHANNEL_
+
+#include <vector>
+
+#include "absl/container/btree_map.h"
+#include "aos/configuration.h"
+#include "aos/events/event_loop.h"
+#include "aos/network/remote_message_generated.h"
+#include "glog/logging.h"
+
+namespace aos {
+namespace message_bridge {
+
+// Class to manage lifetime, and creating senders for channels and connections.
+class ChannelTimestampSender {
+ public:
+ ChannelTimestampSender(aos::EventLoop *event_loop);
+
+ aos::Sender<RemoteMessage> *SenderForChannel(const Channel *channel,
+ const Connection *connection);
+
+ private:
+ aos::EventLoop *event_loop_;
+
+ // We've got 3 cases to consider.
+ // 1) The old single channel per connection exists.
+ // 2) A new channel per channel exists.
+ // 3) Both exist.
+ //
+ // I want the default to be such that if no channel is found, we explode
+ // looking for the single channel per channel. This means users will add the
+ // new channel when blindly fixing errors, which is what we want.
+ //
+ // I'd prefer 3) to be an error, but don't have strong opinions. We will
+ // still be correct if it gets used, as long as everything is consistent.
+
+ // List of Senders per node.
+ std::vector<aos::Sender<RemoteMessage>> timestamp_loggers_;
+
+ // Mapping from channel and connection to logger.
+ absl::btree_map<std::pair<const Channel *, const Connection *>,
+ std::unique_ptr<aos::Sender<RemoteMessage>>>
+ channel_timestamp_loggers_;
+};
+
+} // namespace message_bridge
+} // namespace aos
+
+#endif // AOS_NETWORK_TIMESTAMP_CHANNEL_