Added the thread safe TSQueue and using it in mainwindow to replace the adhoc queue implementation.

asyncdbconnection.h

@@ -0,0 +1,68 @@
+#ifndef ASYNCDBCONNECTION_H
+#define ASYNCDBCONNECTION_H
+
+#include "PgsqlConn.h"
+#include <functional>
+#include <vector>
+
+class ASyncDBConnection {
+public:
+	enum class State {
+		NotConnected,
+		Connecting,
+		Connected,
+		QuerySend,
+		CancelSend
+	};
+
+	using on_result_callback = std::function<void(Pgsql::Result)>;
+	using on_state_callback = std::function<void(State)>;
+
+	ASyncDBConnection();
+
+	void setupConnection(const std::string &connstring);
+	void closeConnection();
+
+	void setStateCallback(on_state_callback state_callback);
+
+	/** Sends command to the server.
+
+	When the result is in and no result_task_queue was passed then on_result will be
+	called directly within the thread.
+
+	If the command gives multiple results on_result will be called for each result.
+	*/
+	bool send(const std::string &command, on_result_callback on_result);
+
+private:
+
+	class Command {
+	public:
+		std::string command;
+		on_result_callback on_result;
+	};
+
+	/// Contains all the members accessed by the thread
+	class Thread {
+	public:
+		on_state_callback m_state_callback;
+		std::string m_init_string;
+
+		/// Is started as a seperate thread by ASyncDBConnection
+		void run();
+
+		/// Sends a cancel request to the DB server
+		void cancel();
+	private:
+
+		Pgsql::Connection m_connection;
+		bool terminateRequested = false; ///< is set when the thread should stop
+
+		bool makeConnection();
+		void communicate();
+	};
+
+	Thread thread;
+};
+
+#endif // ASYNCDBCONNECTION_H