The Ulam spiral is a graphical depiction of a set of prime numbers devised by the mathematician Stanislaw Ulam. To quote the Wiki, it’s constructed by writing the positive integers in a square spiral and specially marking the prime numbers. The outcome is a square with distinct diagonal, horizontal, and vertical lines. This post will walk through the development of a Ulam spiral visualization tool. Creating a Ulam Spiral Take a look at the 4x4 Ulam spiral below: ...
The Caesar Cipher (CC) is a classic symmetric key algorithm dating back to the time of Julius Caesar. If you are new to cryptography, the Caesar Cipher is a great first crypto algorithm to learn. This post will walk through the details of implementing a CC encrypt/decrypt function. You’ll then get a look at the internals of a CC code cracker. Algorithm Description There are four key ingredients to a Caesar Cipher: ...
Have you implemented a shared pointer class in C++? If you have, did you do it in an interview setting? You might be familiar with the STL shared_ptr and the fact that many implementations of shared_ptr use reference counting to manage the lifetime of a dynamically allocated object. That said, if you’ve never thought about or tried to actually implement the concept itself, doing so in an interview is a tall order. This article walks you through the implementation of an interview grade SharedPtr class. ...
This article gives an overview of how to setup a Linux kernel development environment that leverages QEMU. Why should you bother with this setup? Here are the highlights: Make changes to core kernel code or modules without the risk of loading buggy kernel code onto real hardware. Up the speed of the edit, build, run cycle while developing kernel code. The ability to test code across different architectures (for example, aarch64, x86_64, etc.). What’s QEMU? According to Wikipedia: ...
Do you remember when you first learned about recursion? The thought triggered a memory from an old CS101 Java course. The textbook had some fractal triangle thing made with only 20 lines of code. At the time, it was a confusing 20 lines of code. A quick search on Google for “fractal triangle recursion” led straight to the Sierpinski triangle. A Sierpinski triangle generator with an ncurses visualization is a fun afternoon project. ...
If you’ve worked in a large C++ codebase within the last couple of years, you’ve probably come across the GoogleTest unit testing framework. Chances are you’ve also encountered everyone’s favorite build generator: CMake. In this article, you will see two options for integrating GoogleTest into your next CMake project. The content that follows is largely a condensed version of the tips found in “An Introduction to Modern CMake”. This post summarizes the bits relevant to using CMake with GoogleTest to act as a quick reference when setting up future projects. ...
If you’ve been around the open source community long enough, you’ve probably heard of people signing their VCS commits/tags. This post covers the why and how of signing your Git commits. The focus will be on commits but keep in mind that these tips equally apply to tags. Why Sign Your Commits The short answer is, signing your commits makes it harder for an attacker to impersonate you. Sure, if you work solo on rinky-dink toy projects, having your commits signed isn’t a big deal. Now consider the case where you make commits to an open source project with sensitive code or at your day job where you make commits and PRs on a product. It might be worth safeguarding those commits just a bit. ...
Do you have a bunch of dotfiles? Do you maintain a GitHub repo with all your dotfiles? Whenever you upgrade your machine, do you find yourself manually placing the dotfiles in the right spots in your home directory? If you answered yes to these questions, read on. Enter GNU Stow GNU Stow is a dotfile management utility. Stow has all the makings of a varsity athlete: Stow is small (a 32KB Perl script). Stow is simple to use with a solid manpage. Stow doesn’t get in the way of version controlling dotfiles. Real world Stow usage is pretty simple and best explained with an example. Imagine you had your i3wm and Bash configurations stored in your home directory. The layout might look something like this: ...
If you grind old Advent of Code problems, you might notice a particular style of problem crop up more than once. The people of Reddit refer to their solutions as a variation of Conway’s Game of Life (GoL). Wikipedia has a great article on GoL. The animations are eye catching. The Wiki serves as motivation for a terminal app that visualizes GoL simulations. Rules of the Game What are the GoL rules? The setup is simple. You have an MxN grid of “cells.” Each cell is always in one of two states: live or dead. The grid transitions through states on a frame tick. You apply the following rule at each tick. ...
You ever come across one of those ASMR programming videos? This video where the developer programs a terminal display with a couple of spinning cubes is neat. This video is the motivation for the development of a ncurses application that renders a user controlled 3D cube. Perspective Projection and Rotation Matrices So how do you take an object in 3D space and visualize it in 2D space? The answer is perspective projection. Many videos explain the technique in detail. One of the better videos is “Carl the Person”’s (cool name by the way) video tutorial: ...