introduce the aircraft scheduler to receive new messages from the backend

threading-concepts are used to avoid unnecessary main thread action

src/CMakeLists.txt

@@ -32,6 +32,7 @@ SET(SOURCE_FILES
 
 SET(SOURCE_COM_FILES
     com/AircraftReporter.cpp
+    com/AircraftScheduler.cpp
     com/ZmqContext.cpp
     com/ZmqContext.h
 )
@@ -50,6 +51,7 @@ SET(SOURCE_FILES_RES
 
 SET(INCLUDE_COM_FILES
     ${CMAKE_SOURCE_DIR}/include/aman/com/AircraftReporter.h
+    ${CMAKE_SOURCE_DIR}/include/aman/com/AircraftScheduler.h
 )
 
 SET(INCLUDE_CONFIG_FILES

src/com/AircraftScheduler.cpp

@@ -0,0 +1,105 @@
+/*
+ * Author:
+ *   Sven Czarnian <devel@svcz.de>
+ * Brief:
+ *   Implements the scheduling notification
+ * Copyright:
+ *   2021 Sven Czarnian
+ * License:
+ *   GNU General Public License v3 (GPLv3)
+ */
+
+#include <aman/com/AircraftScheduler.h>
+
+#include "ZmqContext.h"
+
+using namespace aman;
+using namespace std::chrono;
+
+AircraftScheduler::AircraftScheduler() noexcept :
+        m_socket(),
+        m_receiverThread(),
+        m_stopReceiver(false) { }
+
+bool AircraftScheduler::initialize(const Communication& configuration) {
+    if (nullptr != this->m_socket)
+        return true;
+    if (false == configuration.valid)
+        return false;
+
+    this->m_socket = std::make_unique<zmq::socket_t>(ZmqContext::instance().context(), zmq::socket_type::sub);
+
+    /* configure the encryption */
+    if (false == this->setSocketKey(configuration.serverPublicIdentifier, zmq::sockopt::curve_serverkey))
+        return false;
+    if (false == this->setSocketKey(configuration.clientPublicIdentifier, zmq::sockopt::curve_publickey))
+        return false;
+    if (false == this->setSocketKey(configuration.clientPrivateIdentifier, zmq::sockopt::curve_secretkey))
+        return false;
+
+    /* connect to the server */
+    try {
+        this->m_socket->connect("tcp://" + configuration.address + ":" + std::to_string(configuration.portNotification));
+    }
+    catch (zmq::error_t&) {
+        this->m_socket = std::unique_ptr<zmq::socket_t>();
+        return false;
+    }
+
+    this->m_stopReceiver = false;
+    this->m_receiverThread = std::thread(&AircraftScheduler::run, this);
+
+    return true;
+}
+
+bool AircraftScheduler::deinitialize() {
+    if (nullptr == this->m_socket)
+        return true;
+
+    this->m_stopReceiver = true;
+    this->m_receiverThread.join();
+    this->m_socket->close();
+    this->m_socket = std::make_unique<zmq::socket_t>();
+
+    return true;
+}
+
+bool AircraftScheduler::initialized() const noexcept {
+    return nullptr != this->m_socket;
+}
+
+std::unique_ptr<aman::AircraftSchedule> AircraftScheduler::receive() {
+    zmq::message_t message;
+
+    if (nullptr == this->m_socket)
+        return std::unique_ptr<aman::AircraftSchedule>();
+
+    try {
+        auto result = this->m_socket->recv(message, zmq::recv_flags::dontwait);
+        if (false == result.has_value() || 0 == result.value())
+            return std::unique_ptr<aman::AircraftSchedule>();
+    }
+    catch (zmq::error_t&) {
+        return std::unique_ptr<aman::AircraftSchedule>();
+    }
+
+    std::unique_ptr<aman::AircraftSchedule> retval = std::make_unique<aman::AircraftSchedule>();
+    retval->ParseFromString(reinterpret_cast<const char*>(message.data()));
+
+    return retval;
+}
+
+void AircraftScheduler::run() {
+    while (false == this->m_stopReceiver) {
+        auto message = this->receive();
+        if (nullptr == message) {
+            std::this_thread::sleep_for(500ms);
+            continue;
+        }
+    }
+}
+
+AircraftScheduler& AircraftScheduler::instance() noexcept {
+    static AircraftScheduler __instance;
+    return __instance;
+}