purplejacket’s gists

purplejacket / race_condition.c

Created March 29, 2026 19:55

Two threads try to increment a counter 50,000 times (each). What's the final count?

	#include <stdio.h>
	#include <pthread.h>
	#define ITERATIONS 100000
	long counter = 0;
	void increment_counter(void arg) {
	for (int i = 0; i < ITERATIONS/2; i++) {
	counter++;
	}
	return NULL;
	}

purplejacket / nibbles.c

Created November 8, 2023 00:56

movfuscator/validation/nibbles.c from https://github.com/Battelle/movfuscator -- needs the ncurses library to compile

	#include <stdlib.h>
	#define _Bool unsigned int /* lcc doesn't define this */
	#include <ncurses.h>

	#define MAX_LENGTH 100

	typedef enum { NONE, UP, DOWN, LEFT, RIGHT } dir_t;

	typedef struct {
	int x, y;

purplejacket / sort2.g0.s

Created June 16, 2023 23:33

zig cc -S -g0 sort2.c -o sort2.g0.s

	.section __TEXT,__text,regular,pure_instructions
	.build_version macos, 13, 1 sdk_version 13, 1
	.globl _variable_sort_2 ## -- Begin function variable_sort_2
	.p2align 4, 0x90
	_variable_sort_2: ## @variable_sort_2
	.cfi_startproc
	## %bb.0:
	pushq %rbp
	.cfi_def_cfa_offset 16
	.cfi_offset %rbp, -16

purplejacket / sort2.c

Created June 14, 2023 03:44

sort2.c — see for example "Faster sorting algorithms discovered using deep reinforcement learning" — https://www.nature.com/articles/s41586-023-06004-9

	void variable_sort_2(int length, int *a) {
	if(length == 2){
	if(a[0] > a[1]){
	int temp = a[0];
	a[0] = a[1];
	a[1] = temp;
	}
	}
	}

purplejacket / sort2.gcc.s

Created June 14, 2023 03:41

gcc -S sort2.c -o sort2.gcc.s

	.section __TEXT,__text,regular,pure_instructions
	.build_version macos, 13, 0 sdk_version 13, 1
	.globl _variable_sort_2 ## -- Begin function variable_sort_2
	.p2align 4, 0x90
	_variable_sort_2: ## @variable_sort_2
	.cfi_startproc
	## %bb.0:
	pushq %rbp
	.cfi_def_cfa_offset 16
	.cfi_offset %rbp, -16

purplejacket / sort2.zig_cc.s

Last active June 14, 2023 03:40

zig cc -S sort2.c -o sort2.zig_cc.s

	.section __TEXT,__text,regular,pure_instructions
	.build_version macos, 13, 1 sdk_version 13, 1
	.file 1 "/tmp" "sort2.c"
	.globl _variable_sort_2 ## -- Begin function variable_sort_2
	.p2align 4, 0x90
	_variable_sort_2: ## @variable_sort_2
	Lfunc_begin0:
	.loc 1 1 0 ## sort2.c:1:0
	.cfi_startproc
	## %bb.0:

purplejacket / umax4_8.c

Created December 21, 2021 19:57

MicroMax chess version 4.8 -- original source: https://home.hccnet.nl/h.g.muller/umax4_8.c

	/***************************************************************************/
	/* micro-Max, */
	/* A chess program smaller than 2KB (of non-blank source), by H.G. Muller */
	/***************************************************************************/
	/* version 4.8 (1953 characters) features: */
	/* - recursive negamax search */
	/* - all-capture MVV/LVA quiescence search */
	/* - (internal) iterative deepening */
	/* - best-move-first 'sorting' */
	/* - a hash table storing score and best move */

purplejacket / screeps_list.html

Created June 30, 2021 23:11

	<html>
	<head>
	<script src="https://cdn.jsdelivr.net/npm/p5@1.3.1/lib/p5.js"></script>
	<ul>
	Screeps
	<ul>
	<li>Harvesters </li>
	<li>Upgraders</li>
	<li>Builders</li>
	</ul>

purplejacket / your_phone_is_listening_to_you_ultrasonic_cross-device_tracking.txt

Last active April 4, 2022 11:37

Your phone is listening to you - ultrasonic cross-device tracking

	Original video: https://www.youtube.com/watch?v=j1FfVK6sj4I
	By: The Hated One

	Ultrasonic cross-device tracking:
	https://intellisec.de/pubs/2016-batmobile.pdf
	https://techcrunch.com/2014/07/24/silverpush-audio-beacons/
	https://www.wired.com/2016/11/block-ultrasonic-signals-didnt-know-tracking/
	https://thehackernews.com/2017/05/ultrasonic-tracking-signals-apps.html
	https://www.cbsnews.com/news/google-removes-apps-that-use-ultrasonic-frequencies-to-track-users/
	https://www.zdnet.com/article/hundreds-of-apps-are-using-ultrasonic-sounds-to-track-your-ad-habits/

purplejacket / mu_puzzle.rb

Created July 1, 2020 05:29

MU puzzle -- from Gödel Escher Bach by Douglas R. Hofstadter -- https://en.wikipedia.org/wiki/MU_puzzle

	# MU puzzle
	# From Gödel Escher Bach by Douglas R. Hofstadter
	# https://en.wikipedia.org/wiki/MU_puzzle

	# Nr. Formal rule Informal explanation Example
	# -----------------------------------------------------------------------------------
	# 1. xI → xIU Add a U to the end of any string ending in I MI to MIU
	# 2. Mx → Mxx Double the string after the M MIU to MIUIU
	# 3. xIIIy → xUy Replace any III with a U MUIIIU to MUUU
	# 4. xUUy → xy Remove any UU MUUU to MU

Kai Middleton purplejacket