Hakim Benoudjit h4k1m0u

File structure

Libraries: Userland/Libraries/{LibC, LibGUI...}
Games: Userland/Games/{Snake, Solitaire...}
Applications: Userland/Applications/{Calculator, Calendar...}

Ninja

SerenityOS is built using CMake and Ninja.

Target: output files of the build process (executables, libraries).
Use Ninja with CMake: cmake -G Ninja (generates a build.ninja file)
Build target: ninja

Electronic components

Breadboard: Rectangular plastic board with tiny holes to insert electronic components in them.
Jump wire: Electrical wire used to interconnect components.
Transistor: Used to amplify current, switch on/off the flow of current, and to construct logic gates.
Diodes: Allows the flow of current in one direction & blocks the other direction (like a valve).
Resistors: Limits the flow of current.
Capacitor: Stores and releases electricity (like a temporary battery).
LED: emits light when current flows through it.
Arduino devices:
Sensors: Used to monitor physical phenomena (e.g. temperature, humidity, motion, light...).

C++ syntax

List initialization

Advantage: Doesn't allow narrowing, i.e. the following throws an error:

int i {2.0f};

Direct and copy initialization

Advantage: Doesn't create a copy (practical for objects):

Below some notions about USB that could be useful to access USB devices programatically with [libusb]. For more details refer to [USB2.0 specification][usb2-specification].

Terminology

Host: Computer.
USB device: Peripheral connected to computer via USB.
Hub: USB device providing additionnal connections to the USB.
IRQ (Interrupt request): a hardware signal from device requesting attention from host.
Pipe: Logical abstraction for associating device's endpoint and host's software. There two types of pipes:
- Stream pipe: data no USB-defined structure.
Message pipe: data has a USB-defined structure.

OSI model

For systems interconnections in a network, and has 7 layers (from top to bottom):

Application: Closest to user, e.g. HTTP, FTP...
Presentation: Encryption/Decryption, Compression/decompression, e.g. jpeg, mpeg...
Session: e.g. sync file transfers with checkpoints (to avoid restarting from beginning on failure).
Transport: Flow and error control, e.g. TCP, UDP
Network: breaks/assembleds data into packets, routing, e.g. IP
Data link: connects devices that are physically in the same network, e.g. Ethernet, MAC
Pyhsical: bit (raw data), e.g. cables

SF2 format

File format (binary) storing multiple instruments.
Stores instrument samples to play MIDI.
Samples are stored:
- For each note of an instrument (e.g. all piano keys).
- Possibly multiple velocities by key (how hard the note was struck).
[Polyphone][polyphone] can be used to read sf2 files.
[soundfont-fluid][soundfont-fluid] and [freepats-general-midi][freepats-general-midi] provide free samples in sf2 format (installed to /usr/share/soundfonts/).
Jack2: is an audio server like pulseaudio and alsa but professional audio production thanks to its low latency:

Dependencies

$ sudo pacman -Sy raylib

How to run

$ mkdir build
$ cd build
$ cmake .. &amp;&amp; make -j

	#include <limits.h>
	#include <string.h>
	#include <stdbool.h>
	#include <gd.h>

	#include "utils.h"

	/**
	* Print password written beforehand on image with steganography_write.c
	* - GD documentation: https://libgd.github.io/manuals/2.1.1/files/preamble-txt.html

	#include <gd.h>

	// C doesn't allow variable length arrays (even using a constant)
	#define N_CORNERS 3

	typedef struct {
	int x;
	int y;
	} Point;

	#include <stdio.h>
	#include <stdint.h>
	#include <stdlib.h>
	#include <string.h>
	#include <math.h>

	/**
	* Parse bitmap image to find RGB values at given row and column
	* Bitmap format: https://en.wikipedia.org/wiki/BMP_file_format
	* Tested input bitmap image saved in Gimp without color space information and in 24bits format