--- a/src/JackHandler.h	Tue Sep 29 20:49:04 2020 +0200
+++ b/src/JackHandler.h	Wed Sep 30 00:34:41 2020 +0200
@@ -17,6 +17,7 @@
 #pragma once
 
 #include <memory>
+#include <atomic>
 #include <string>
 #include <vector>
 #include <iostream>
@@ -24,6 +25,7 @@
 #include <locale>
 #include <codecvt>
 #include <sys/mman.h>
+#include <signal.h>
 
 #include <jack/jack.h>
 #include <jack/midiport.h>
@@ -41,6 +43,8 @@
 namespace out {
 namespace jack {
 
+int dequeueMessages(jack_nframes_t frames, void* arg);
+
 class JackHandler : public relpipe::reader::handlers::RelationalReaderStringHandler {
 private:
 	Configuration& configuration;
@@ -48,7 +52,18 @@
 
 	jack_client_t* jackClient = nullptr;
 	jack_port_t* jackPort = nullptr;
-	//jack_ringbuffer_t* ringBuffer = nullptr;
+	jack_ringbuffer_t* ringBuffer = nullptr;
+
+	std::atomic<bool> continueProcessing{true};
+
+	const int RING_BUFFER_SIZE = 100;
+
+	struct MidiMessage {
+		uint8_t buffer[4096];
+		uint32_t size;
+		uint32_t time;
+	};
+
 public:
 
 	JackHandler(Configuration& configuration) : configuration(configuration) {
@@ -57,9 +72,9 @@
 		jackClient = jack_client_open(clientName.c_str(), JackNullOption, nullptr);
 		if (jackClient == nullptr) throw JackException(L"Could not create JACK client.");
 
-		//ringBuffer = jack_ringbuffer_create(RING_BUFFER_SIZE * sizeof (MidiMessage));
+		ringBuffer = jack_ringbuffer_create(RING_BUFFER_SIZE * sizeof (MidiMessage));
 
-		//jack_set_process_callback(jackClient, relpipe::in::jack::enqueueMessage, this);
+		jack_set_process_callback(jackClient, relpipe::out::jack::dequeueMessages, this);
 		// TODO: report also other events (connections etc.)
 
 		jackPort = jack_port_register(jackClient, "output", JACK_DEFAULT_MIDI_TYPE, JackPortIsOutput, 0);
@@ -72,26 +87,48 @@
 	}
 
 	void startRelation(const relpipe::common::type::StringX name, std::vector<relpipe::reader::handlers::AttributeMetadata> attributes) override {
-		
+		// TODO: validate metadata and prepare attribute mappings (names and types are important, order does not matter)
+
 	}
 
 	void attribute(const relpipe::common::type::StringX& value) override {
-		
+		// TODO: append to current message + if this is last attribute, put whole message to the ring buffer
+		// TODO: if (continueProcessing) {} ?
 	}
 
 	void endOfPipe() {
-		
+		// TODO: send optional (configurable) MIDI events
+		// TODO: wait until the ring buffer is empty
+	}
+
+	int dequeueMessages(jack_nframes_t frames) {
+
+
+		// TODO: send events from the ring buffer to JACK + correct timing
+		std::cout << "dequeueMessages(" << frames << ")" << std::endl;
+
+
+		return 0;
+	}
+
+	void finish(int sig) {
+		continueProcessing = false;
 	}
 
 	virtual ~JackHandler() {
 		// Close JACK connection:
 		jack_deactivate(jackClient);
 		jack_client_close(jackClient);
-		//jack_ringbuffer_free(ringBuffer);
+		jack_ringbuffer_free(ringBuffer);
 	}
 
 };
 
+int dequeueMessages(jack_nframes_t frames, void* arg) {
+	JackHandler* instance = (JackHandler*) arg;
+	return instance->dequeueMessages(frames);
+}
+
 }
 }
 }

--- a/src/relpipe-out-jack.cpp	Tue Sep 29 20:49:04 2020 +0200
+++ b/src/relpipe-out-jack.cpp	Wed Sep 30 00:34:41 2020 +0200
@@ -35,18 +35,26 @@
 using namespace relpipe::reader;
 using namespace relpipe::out::jack;
 
+static std::shared_ptr<JackHandler> jackHandler = nullptr;
+
+void finish(int sig) {
+	if (jackHandler) jackHandler->finish(sig);
+}
+
 int main(int argc, char**argv) {
 	CLI cli(argc, argv);
 	CLI::untieStdIO();
-	
+
 	int resultCode = CLI::EXIT_CODE_UNEXPECTED_ERROR;
 
 	try {
+		signal(SIGHUP, finish);
+		signal(SIGINT, finish);
 		CLIParser cliParser;
 		Configuration configuration = cliParser.parse(cli.arguments());
 		std::shared_ptr<RelationalReader> reader(Factory::create(std::cin));
-		JackHandler handler(configuration);
-		reader->addHandler(&handler);
+		jackHandler.reset(new JackHandler(configuration));
+		reader->addHandler(jackHandler.get());
 		reader->process();
 
 		resultCode = CLI::EXIT_CODE_SUCCESS;