diff -r ef8f4023e32e -r bddcf2bf29f2 DJMFix.cpp
--- a/DJMFix.cpp	Sat Dec 19 17:33:16 2020 +0100
+++ b/DJMFix.cpp	Sat Dec 19 23:59:39 2020 +0100
@@ -17,18 +17,23 @@
 #include <iostream>
 #include <iomanip>
 #include <thread>
+#include <mutex>
 #include <atomic>
 #include <chrono>
 #include <stdexcept>
+#include <vector>
 
 #include "DJMFix.h"
 
 namespace djmfix {
 
+using Bytes = std::vector<uint8_t>;
+
 class DJMFixImpl : public DJMFix {
 private:
 	MidiSender* midiSender;
 	std::thread keepAliveThread;
+	std::recursive_mutex midiMutex;
 	std::atomic<bool> running{false};
 	std::atomic<bool> stopped{false};
 
@@ -40,13 +45,64 @@
 		}
 	}
 
-	// TODO: remove
-	std::string toString(const MidiMessage& midiMessage) {
+	void send(const MidiMessage& midiMessage) {
+		std::lock_guard<std::recursive_mutex> lock(midiMutex);
+		midiSender->send(midiMessage);
+	}
+
+	std::string toString(const Bytes& midiMessage) {
 		std::stringstream result;
 		for (uint8_t b : midiMessage) result << std::hex << std::setw(2) << std::setfill('0') << (int) b;
 		return result.str();
 	}
 
+	Bytes normalize(const Bytes& data) {
+		if (data.size() % 2) throw std::invalid_argument("data before normalization must have even number of bytes");
+		Bytes result;
+		result.reserve(data.size() / 2);
+		for (size_t i = 0; i < data.size() / 2; i++) result.push_back((data[i * 2] & 0x0F) << 4 | (data[i * 2 + 1] & 0x0F));
+		return result;
+	}
+
+	uint32_t fnv32hash(const Bytes& buff) {
+		uint32_t hash = 0x811c9dc5;
+		for (uint8_t b : buff) hash = ((b^hash) * 0x1000193);
+		return hash;
+	}
+
+	Bytes toBytes(const uint32_t value) {
+		Bytes result;
+		result.reserve(4);
+		result.push_back(value >> 24);
+		result.push_back(value >> 16);
+		result.push_back(value >> 8);
+		result.push_back(value >> 0);
+		return result;
+	}
+
+	bool equals(Bytes a, Bytes b) {
+		if (a.size() != b.size()) return false;
+		for (size_t i = 0; i < a.size(); i++) if (a[i] != b[i]) return false;
+		return true;
+	}
+
+	template<typename T> std::vector<T> concat(const std::vector<T>& a, const std::vector<T>& b, const std::vector<T>& c = {}) {
+		std::vector<T> result;
+		result.reserve(a.size() + b.size() + c.size());
+		for (size_t i = 0; i < a.size(); i++) result.push_back(a[i]);
+		for (size_t i = 0; i < b.size(); i++) result.push_back(b[i]);
+		for (size_t i = 0; i < c.size(); i++) result.push_back(c[i]);
+		return result;
+	}
+
+	template<typename T> std::vector<T> xOR(const std::vector<T>& a, const std::vector<T>& b) {
+		if (a.size() != b.size()) throw std::invalid_argument("xor: both must be the same length");
+		std::vector<T> result;
+		result.reserve(a.size());
+		for (size_t i = 0; i < a.size(); i++) result.push_back(a[i] ^ b[i]);
+		return result;
+	}
+
 public:
 
 	virtual ~DJMFixImpl() override {
@@ -59,11 +115,27 @@
 		this->midiSender = midiSender;
 	}
 
-	virtual void receive(MidiMessage midiMessage) override {
+	virtual void receive(const MidiMessage& midiMessage) override {
 		std::cerr << "DJMFixImpl::receive(): size = " << midiMessage.size() << " data = " << toString(midiMessage) << std::endl; // TODO: do not mess STDIO
+		std::lock_guard<std::recursive_mutex> lock(midiMutex);
+
+		if (midiMessage.size() == 54 && midiMessage[9] == 0x13 && midiMessage[33] == 0x04 && midiMessage[43] == 0x03) {
+			Bytes hash1(midiMessage.begin() + 35, midiMessage.begin() + 35 + 8);
+			Bytes seed2(midiMessage.begin() + 45, midiMessage.begin() + 45 + 8);
+			hash1 = normalize(hash1);
+			seed2 = normalize(seed2);
+			std::cerr << "DJMFixImpl::receive(): got message with hash1 = " << toString(hash1) << " and seed2 = " << toString(seed2) << std::endl; // TODO: do not mess STDIO
 
-		if (midiMessage.size() == 54 && midiMessage[9] == 0x13) {
-			std::cerr << "DJMFixImpl::receive(): got message with HashA and SeedE" << std::endl; // TODO: do not mess STDIO
+			Bytes seed0 = {0x68, 0x01, 0x31, 0xFB};
+			Bytes seed1 = {0x29, 0x00, 0x00, 0x00, 0x23, 0x48, 0x00, 0x00};
+
+			Bytes hash1check = toBytes(fnv32hash(concat(seed1, xOR(seed0, seed2))));
+
+			if (equals(hash1, hash1check)) {
+				std::cerr << "DJMFixImpl::receive(): hash1 verification: OK" << std::endl;
+			} else {
+				std::cerr << "DJMFixImpl::receive(): hash1 verification: ERROR: check = " << toString(hash1check) << std::endl;
+			}
 		}
 
 	}
@@ -73,9 +145,9 @@
 		if (midiSender == nullptr) throw std::logic_error("need a midiSender when starting DJMFix");
 
 		// TODO: methods for parsing and constructing messages from parts (TLV)
-		midiSender->send({0xf0, 0x00, 0x40, 0x05, 0x00, 0x00, 0x00, 0x17, 0x00, 0x50, 0x01, 0xf7});
-		std::this_thread::sleep_for(std::chrono::milliseconds(10));
-		midiSender->send({0xf0, 0x00, 0x40, 0x05, 0x00, 0x00, 0x00, 0x17, 0x00, 0x12, 0x2a, 0x01, 0x0b, 0x50, 0x69, 0x6f, 0x6e, 0x65, 0x65, 0x72, 0x44, 0x4a, 0x02, 0x0b, 0x72, 0x65, 0x6b, 0x6f, 0x72, 0x64, 0x62, 0x6f, 0x78, 0x03, 0x12, 0x02, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x03, 0x04, 0x08, 0x00, 0x00, 0x00, 0x00, 0xf7});
+		send({0xf0, 0x00, 0x40, 0x05, 0x00, 0x00, 0x00, 0x17, 0x00, 0x50, 0x01, 0xf7});
+		std::this_thread::sleep_for(std::chrono::milliseconds(30)); // TODO: wait until we got the response
+		send({0xf0, 0x00, 0x40, 0x05, 0x00, 0x00, 0x00, 0x17, 0x00, 0x12, 0x2a, 0x01, 0x0b, 0x50, 0x69, 0x6f, 0x6e, 0x65, 0x65, 0x72, 0x44, 0x4a, 0x02, 0x0b, 0x72, 0x65, 0x6b, 0x6f, 0x72, 0x64, 0x62, 0x6f, 0x78, 0x03, 0x12, 0x02, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x03, 0x04, 0x08, 0x00, 0x00, 0x00, 0x00, 0xf7});
 
 		keepAliveThread = std::thread(&DJMFixImpl::run, this);
 		running = true;