Presentation topic: “Multi-Factor Authentication”
Presenter: Efstathios Chatzikyriakidis
PDF presentation: https://bit.ly/2ugskDH
Source code: https://bit.ly/2FkUfJf
Tag Archive: free software
This project refers to an Arduino library implementing a generic, dynamic stack (array version).
The data structure is implemented as a class in C++.
For more information, you can get the project itself ‘StackArray‘.
Hello people! I hope you are well!
In this article I would like to present you a simple C++ 3D vector library. This is just a prototype and I am sure you can find other better and more complete alternatives. So, we are just dealing here with a “Yet Another 3D Vector Library”.
I created this library because I wanted to reuse some 3D vector operations in various OpenGL computer graphics exercise programs (from my M.Sc. studies). Of course, I could use an already existing library. However, I wanted also to understand how some basic 3D vector operations work.
In this article I will present to you a dynamic string data structure helper implementation. In C, a string is just an array of characters terminated with the null character (NUL in ASCII). Also, some times we handle a string by using a pointer to a buffer containing sequential characters terminated also with the null character. The C standard liibrary provides various functions for string manipulation but it seems that whenever we want to extend a string by using pointers we have to perform all the time memory reallocation which leads to a bad evolution of replicated code. In a recent project, I needed to create a string and append to it any number of new strings in order to extend it without using strcat, strcpy, strlen and realloc functions all the time. So, I created a simple dynamic string data structure which solved my specific problem and I would like to share it with you people.
In this article I will present to you a useful function for getting the host name and service of a socket.
In this article I will present to you a POSIX function I wrote that can be used to create a server socket to support both IPv4 and IPv6 addresses (IP-Agnostic). Recently, I needed to support this feature in a server application. The implementation uses POSIX system calls and data structures that can be used as generics to support both IPv4 and IPv6.
Zepto Web Server is a tiny open source HTTP web server well-written in C that can handle simple HTTP requests and serve information in HTML format by using dynamic modules that can be loaded at runtime. Also, the HTTP web server runs as a daemon process and is designed according to the MPM (Multi-Processing Module) architecture that allows multiple requests to be processed almost simultaneously. The main server daemon process creates and maintains various server workers which handle incoming requests.
In this article I’ll show you how you can create the abstract syntax tree (AST) of an input stream while parsing it. A parser usually reads various tokens from its input by using a lexer as a helper coroutine and tries to match various grammar rules that specify the syntax of a language (the source language).
In this article I’ll present to you some common conflicts that usually occur in Bison grammars and ways of resolving these. At first, conflicts in Bison context are situations where a sequence of input can be parsed in multiple ways according to the specified BNF grammar rules.
In this article I’ll show you how syntactically similar tokens can be handled in a unified way in order to simplify both lexical and syntactic analysis. The trick is to use one token for several similar operators in order to keep down the size of the grammar in the parser and to simplify the regular expression rules in the lexer.
Sometimes while I exploring the source code of various free software Flex lexers and Bison parsers I see name declarations for single character tokens.
Many programming languages and computer files have a directive, often called “include” (as well as “copy” and “import”), that causes the contents of a second file to be inserted into the original file. These included files are called copybooks or header files. They are often used to define the physical layout of program data, pieces of procedural code and/or forward declarations while promoting encapsulation and the reuse of code.
Below, there are some useful regular expressions for matching C-like primitive data values.
Below, is a simple example for counting words, lines and characters by using a Flex lexer.
This project aims to the development of an open-source experimental prototype for solving and generating Sudoku puzzles by using only the strength of Genetic Algorithms. This is not a general purpose GA framework but a specific GA implementation for solving and generating Sudoku puzzles. The mechanics of the GA are based on the theoretical scientific paper “Solving and Rating Sudoku Puzzles with Genetic Algorithms” of Timo Mantere and Janne Koljonen. From the first moment, I liked the paper. So, I implemented it in Python. Also, I have add some variations to the algorithm in order to be more efficient. This project can be used in order to solve or generate new NxN Sudoku puzzles with N sub-boxes (e.g. 4×4, 9×9, etc).
In this article I’ll show you a simple PHP function that implements email validation.
The function performs two checks :
It checks both if the email has correct syntax and if the domain of the email exists.
In your lexer when lexical analysis is performed you may want to ignore any multiline C-like comments.
Whenever you want to post your email address to the public and don’t want to use a Contact Form which usually hides the address, try to display the address of the email as an image in order to avoid spam.
One way to achieve this is to manually create your email address as an image and embed it to your contact page. Most of the times we want this operation to be automatically. So, I have created a simple example to show you how you can make this possible.
Whenever we create a new source code file for a free software with Emacs we need first to add the short brief of the blessed GNU GPL v3. You can add a LISP function to your “~/.emacs” configuration file and call it whenever you want to add it.
If the file is missing you can create it.
After inserting the function and restarting Emacs you can call the function:
M-x insert-short-gpl (press Alt-x, type insert-short-gpl, press return).
Many text editors create backup files with names ending with “~”.
Most of the times these files are annoying and unnecessary…
So, you can use the following piped commands to remove them :
find / | grep "^.*~$"
| sed -e 's/\(^.*$\)/"\1"/g'
| xargs rm -f > /dev/null 2>&1
Please take account that this version handles correctly also filepaths containing space characters.
Within the framework of the course “Operating Systems I – Laboratory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we were asked to choose one of 25 available projects aiming to implement and then present to the entire class. My choice was project 17, whose goal was the implementation of the external ‘find’ command of the operating system MS-DOS.
This project refers to an Arduino sketch that implements a light indicator with the help of an external sensor (photoresistor) for the recognition of light, and a bar graph of many LEDs used as a rating indicator. Furthermore, if the indicator reaches the last rating which indicates that there is “perfect” light (the maximum light that the sensor can identify) then it plays a melody with a piezo speaker located in the system.
This project refers to an Arduino sketch which is used to produce animations with more than one LED. You can place several LEDs in a row or in any order you wish and enjoy the flow of traffic. Furthermore, if you wish to change the animation you can choose the next in line by pressing a special button. One such application might remind you of the Christmas lights.
Within the framework of the course “Software Engineering I – Laboratory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we developed as a semester assignment a parking management application.
Both the graphical user interface (GUI) and the application are implemented with Qt in C++. Specifically, with this application, the end user can manage a variety of customers, customer cards, vehicles, transactions, parking, vehicle fees, etc.
The project ‘tct ‘(The Crime Tracer) is an online adventure police game. Of course it has not yet implemented because it is under development. The game is a free software initiative of two volunteers who love and respect science and the freedom of users. Anyone can join the project as a volunteer, provided they are good-willed and have some free time. Also, the game is being developed using the Python programming language and the Pygame framework.
The project ‘shell-library’ (Shell Function Library) is a developers’ effort to develop a free shell library with POSIX general purpose functions. The functions that the library offers can be used within shell scripts developed to automate the work of your operating system.
The project ‘nxnes’ (NxN Equalisations Solver) is the implementation of project 5 from the list of selected projects in the course “Operating Systems II – Laboratory” (Department of Informatics and Communications, T.E.I. of Central Macedonia). The objective of this project was the implementation of the Gauss Elimination Method to solve a NxN system of linear equations.
Within the framework of the course “Operating Systems II – Laboratory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we were asked to choose one of the 20 available projects to achieve. My choice was project 10, whose goal was to implement a birthday and celebrations alert system.
The project ‘OSHACKERS’ (Operating System Hackers) and the website ‘oshackers.org’ refer to a safe, free, friendly and useful to the end-user online web system for visualising information related to the various users of the various free and open operating systems around the world.
The project ‘vs-cms’ (Very Simple Content Management System) is a personal project and a web content management system.
The project ‘www-el‘ (formerly ‘elwebtrans’) serves to translate all the important articles, texts (web pages) of the GNU Project in the Greek language. All members of the project ‘www-el‘ are volunteers who contribute their work to spread the GNU Project and the philosophy of the Free Software Foundation in the Greek public. If you have some free time and want to contribute to the defense of liberty and the further dissemination of Free Software, help our project.
Within the framework of the course “Operating Systems II – Laboratory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we developed as a semester assignment an application whose aim was to simulate the evolution of a colony of single-celled organisms, namely the creation of the famous game of life.
The project ‘tct‘ (The Crime Tracer) fanned my wish to create a resource manager for the needs of the game. Generally, a resource manager increases efficiency in most cases because it uses internal caching and mapping. The resource manager of the project ‘tct‘ is written in Python and manages graphics, sounds and Pygame fonts.
A beautiful and dynamic experience that I hope will be repeated again.
Congratulations to the organizers and participants of this conference.
Their contributions to Free Software was invaluable.
This project refers to the development of the procedural programming language YAFL (Yet Another Free Language) as well as its interpreter. The programming language YAFL is a tool for teaching the basic principles of procedural programming to secondary school students and beginners in general.
The GNU Project by Richard Stallman
The original version was published in the book “Open Sources”
The first software-sharing community
When I started working at the MIT Artificial Intelligence Lab in 1971, I became part of a software-sharing community that had existed for many years. Sharing of software was not limited to our particular community; it is as old as computers, just as sharing of recipes is as old as cooking. But we did it more than most.
The project “Steganography System” refers to an open-source steganography system which can be used to hide text in digital media formats (image, audio, video). Generally, steganography is the art of hiding a message in a way that its existence is only known to its recipient.
The project ‘tct‘ (The Crime Tracer) made me wish to create an engine for moving various sprites in two-dimensional games. This engine is a prototype and is continuously optimized. It has also been developed with the help of Pygame and Python. Additionally, you can find a rough example that uses the engine of the project ‘tct‘ (The Crime Tracer).
The project “PGASystem” (Parallel Genetic Algorithms System) is an under development system based on the client / server architecture and can be used to implement and study of parallel genetic algorithms.
TheHackerspace (Thessaloniki’s Hackerspace) is here!
We announce that at 7.00 pm on Thursday 30/6 we organize a kick-off event for the presentation of TheHackerspace at the Art Cafe “Kokini Klosti Demeni” which is the permanent meeting place at 32 Nicosia Street, Kalamaria, Thessaloniki. Come to get to know us, to see you and share ideas!
The TheHackerspace is an open laboratory for research, collaboration, creativity and learning. But above all, it is a vibrant community of people with ideas and concepts stemming from the philosophy of Free Software / Open Hardware. The idea for the project was started a few months ago by people who love Hacking, both software and hardware, and soon was put into practice with passion and desire to contribute to the community.
Our moto is “Love to hack embedded & operating systems!“.
Happy Hacking,
Stergios Kalamopoulos
Efstathios Chatzikyriakidis
Stavros Kalapothas
The Free Software / Open Source Software Association (FS / OSSA) recently organized a conference entitled “Open Source: Opportunity Development” in various cities. Also, last Sunday (22/05/11), I had the opportunity to attend the one-day workshop held at the University of Macedonia in Thessaloniki.
Probably sometime you will need to write a program in assembly language. For this reason, in this article we will develop a simple and typical executable “Hello World” program in assembly language to familiarize yourself with the process.
I quote below a personal portable implementation (in C++) of a classic Differential Evolution algorithm used to maximize the function f(x) = sin(x) in the domain 0 <= x <= 2pi. You can compile the program with the g++ compiler.
I quote below a personal portable implementation (in C++) of a classic genetic algorithm (evolutionary algorithm) used to maximize the function f(x, y) = sin(x) * sin(y) in the domain 0 <= x, y <= 2pi. You can compile the program with the g++ compiler.
I quote below a personal portable implementation (in C++) of a classic genetic algorithm (evolutionary algorithm) used to maximize the function f(x) = sin(x) in the domain 0 <= x <= 2pi. You can compile the program with the g++ compiler.
I quote below a personal portable implementation (in C++) of a classic genetic algorithm (evolutionary algorithm) used to maximize the function f(x) = sin(x) in the domain 0 <= x <= 2pi. You can compile the program with the g++ compiler.
I quote below a personal portable implementation (in C++) of a classic genetic algorithm (evolutionary algorithm) used to maximize the function f(x) = sin(x) in the domain 0 <= x <= 2pi. You can compile the program with the g++ compiler.
Within the framework of the course “Software Engineering II – Laboratory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we developed as a semester assignment an application for the management of hotel businesses.
Both the graphical user interface (GUI) and the application were implemented with Qt while the database in SQLite. More specifically, the end user can perform through this application functions such as: processing of customers / rooms, booking rooms, search rooms / customers, inventory of hotel services offered to customers, central management for the correct operation of the hotel, central management of the cost of services provided, as well as adding new users and system administrators to the system.
This project refers to a safe, friendly and useful to the end-user Web Geographic Information Management System which is used for displaying and managing GIS on the Internet. The Geographic Information is located on an exclusive database (MySQL) and the user can browse them by categories. The system also has both front-end for the viewing of GIS as well as back-end for managing the overall system.
This project is free software and you can improve it if you want to.
This project refers to an Arduino library implementing a generic, dynamic queue (array version).
The data structure is implemented as a class in C++.
For more information, you can get the project itself ‘QueueArray‘.
This project refers to an Arduino library for implementing a generic, dynamic queue (linked list version).
The data structure is implemented as a class in C++.
For more information, you can get the project itself ‘QueueList‘.
This project refers to an Arduino library implementing a generic, dynamic stack (linked list version).
The data structure is implemented as a class in C++.
For more information, you can get the project itself ‘StackList‘.
In this article, I quote a personal documentation implementation of the source code of the application “GNU Find String” using the Doxygen system. The source code of the application is written in ANSI C. You’ll find the documentation here: Doxygen documentation of the source code of the application “GNU Find String”.
The presence of errors in software development (and not only) is inevitable. However, over time the programs improve and tend to perfection through various techniques and methods we have developed.
The deterministic problems are easy to spot because they always lead to the same error. There are tools that run through the source code of an application to find possible deterministic errors (these tools are especially useful in applications written with scripting languages such as Python, Bash Scripting, etc).
The QT provides an adorable way to store the settings of a program with a GUI (and not only) by means of the QSettings library. Below, we quote a personal version of the project ‘parkman‘ (Parking Manager).
Below I quote a simple but useful library (implemented in C++) which contains functions for comparing double precision floating point numbers.
Within the framework of the course “Programming II – Laboratory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we were asked to implement as homework a program that reads characters from the standard input and then export to standard output a frequency histogram of the characters that appear.
This project refers to an Arduino sketch which is used to produce LEDs animations. So, we use an 8-bit shift register (namely the 74HC595). This way we can drive 8 different LEDs in the output committing only three PINS of the Arduino.
If we want to drive more LEDs, we connect into a cascade form two or more (depending on the number of LEDs we want to support) shift registers and act accordingly.
Within the framework of the course “Numerical Methods in Programming Environments – Theory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we were asked to develop an optional program that implements Müller’s numerical method for finding the root of equations of the form f(x) = 0.
Within the framework of the course “Visual Programming – Theory” (Department of Informatics and Communications, T.E.I. of Central Macedonia) we developed a clinic management application as a semester project.
The database of the application was implemented in Microsoft SQL Server and the graphical user interface in Borland C++ Builder.
More specifically, this application enables the end user to manage different patients, visits, appointments, diagnoses, treatments, prescriptions, tests, links.
The project ‘dec2bin’ (decimal to binary converter) is the implementation of an idea I had for some time. I have to admit that sometime in the past when studying possible ways of programming embedded systems with the programming language C and C++, I felt the need to be able to produce, through a program, supposed memory addresses in the form of binary numbers.
A beautiful and dynamic experience that I hope will be repeated again.
Congratulations to the organizers and participants of this conference.
Their contributions to Free Software was invaluable.
Ignoring multiline comments with start states in compilers with Flex.
In a previous article I have presented a way for ignoring multiline comments with an old fashion way.
In this article I’ll demonstrate a more elegant Flex-like way for ignoring multiline comments.
Continue reading →