Costava’s gists

Costava / fread_gotcha.c

Last active January 18, 2020 20:58

In C, the `fread` function can move the file position indicator forward but not read any objects if object size is greater than 1 and less than <object size> bytes remain in the file. This makes it possible to reach the end of the file, but 'miss' the last 1-3 bytes (1-3 if reading 4-byte objects).

	// If you try to read a 3-byte file for a 4-byte object,
	// then you will read 0 objects and the file position indicator will be moved
	// to the end of the file
	//
	// so you can reach end-of-file and possibly miss 1-3 bytes
	// if you've been reading 4-byte objects

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

Costava / uniquelines.c

Last active September 3, 2020 05:22

Prints a list of the lines in file1 that are not in file2 and a list of the lines in file2 that are not in file1

	// COMPILING:
	// gcc -std=c99 -Wall --output uniquelines uniquelines.c

	// USAGE:
	// ./uniquelines path/to/file1 path/to/file2

	// DESCRIPTION:
	// Prints a list of the lines in file1 that are not in file2
	// and a list of the lines in file2 that are not in file1
	// Within a file, lines are separated by a single-character `DELIMITER`

Costava / ray-demo.rkt

Created June 14, 2020 21:12

Small, interactive racket/gui program that uses a ray shot from a camera position to color each pixel of the window.

	#lang racket/gui

	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

	; File: ray-demo.rkt
	; Author: Costava
	; License: zlib license (see end of file)

	; Written for Racket 7.7
	; Opens a window

Costava / racket-gui-slider.rkt

Created July 3, 2020 21:09

Window with a slider labeled "Volume"

	#lang racket/gui

	(define frame (new frame% [label "Slider"]))

	(new slider%
	[parent frame]
	[label "Volume"]
	[min-value 0]
	[max-value 100])

Costava / solidcolorppm.c

Created August 20, 2020 01:20

Writes a solid color P3 .ppm file to stdout using the given width, height, and RGB color arguments

	// Writes a solid color P3 .ppm file to stdout
	// using the given width, height, and RGB color arguments

	// Info on the .ppm file format:
	// https://en.wikipedia.org/wiki/Netpbm#File_formats

	// Compile:
	// clang solidcolorppm.c --output solidcolorppm
	// Run:
	// ./solidcolorppm <width> <height> <r> <g> <b>

Costava / cwrap.c

Created September 3, 2020 04:24

	// gcc -std=c99 -Wall --output cwrap cwrap.c && ./cwrap

	#include <stdint.h>
	#include <stdio.h>

	int main(void)
	{
	uint8_t val = 255;
	val += 1;
	printf("val: %d\n", val);// val: 0

Costava / countnonwhitespace.c

Created September 3, 2020 04:32

Read stdin, count non-whitespace characters, and print the count to stdout

	// The program reads stdin, counts the number of non-whitespace characters, and
	// then prints the count to stdout
	// UTF-8 encoding is expected
	// If a non-ASCII character is found, the program prints to stderr and exits,
	// but the program should be easy to extend to properly support UTF-8

	// COMPILING:
	// gcc -std=c99 -Wall --output countnonwhitespace countnonwhitespace.c

	// USAGE:

Costava / fltk_radio_button_groups.cpp

Created September 20, 2020 19:54

FLTK GUI window with two sets of radio buttons

	// FLTK GUI window with two sets of radio buttons
	//
	// COMPILE AND RUN:
	/* g++ --output fltk_radio_button_groups -std=c++98 -Wall -g -lfltk \
	fltk_radio_button_groups.cpp && ./fltk_radio_button_groups */
	//
	// Install FLTK through your package manager e.g. pamac install fltk
	//
	// Unfortunately, this compiles with 4 ugly warnings that
	// the button variables are unused (using g++ v10.2.0)

Costava / rand_rgb_window.c

Created September 23, 2020 23:48

Benchmark touching every pixel of an SDL_Surface every frame

	// Sort of a benchmark --- if touching every pixel every frame,
	// a real program should not hope to get a higher frames per second
	// than this simple demo.
	//
	// Single process and thread
	// Uses SDL_Surface (none of SDL_Texture)

	#include <stdbool.h>
	#include <stdio.h>
	#include <stdint.h>

Costava / sdl2_tex_component_order.c

Created September 28, 2020 23:20

SDL_Texture color component order in pixels array (SDL2)

	// If a texture has format SDL_PIXELFORMAT_ABGR8888,
	// then the red component is the first byte in the pixels array of the texture
	// Tested on a little-endian (x86) system
	// Would the red component also come first in the array on a big-endian system?
	//
	// Tested with SDL2 version 2.0.12

	#include <stdbool.h>
	#include <stdio.h>
	#include <stdint.h>