Gautam gautamk

This was a response to a Hacker News comment asking me what I've been up to since 2010. I'm posting it here since HN rejects it with "that comment is too long." I suppose that's fair, since this ended up being something of an autobiography.

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What happened after 2010?

Controlling the Brother P-Touch Cube label maker from a computer

The Brother PTP300BT label maker is intended to be controlled using the official Brother P-Touch Design & Print iOS/Android app. The app has arbitrary limits on what you can print (1 text object and up to 3 preset icons), so I thought it would be a fun challenge to reverse engineer the protocol to print whatever I wanted.

Python code at the bottom if you want to skip the fine details.

Process

Intitially I had a quick peek at the Android APK to see if there was any useful information inside. The code that handles the communication with the printer in Print&Design turned out to be a native library, but the app clearly prepares a bitmap image and passes it to this native library for printing. Bitmaps are definitely something we can work with.

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

Auto-deploying built products to gh-pages with GitHub Actions

This is a set up for projects which want to check in only their source files, but have their gh-pages branch automatically updated with some compiled output every time they push.

A file below this one contains the steps for doing this with Travis CI. However, these days I recommend GitHub Actions, for the following reasons:

It is much easier and requires less steps, because you are already authenticated with GitHub, so you don't need to share secret keys across services like you do when coordinate Travis CI and GitHub.
It is free, with no quotas.
Anecdotally, builds are much faster with GitHub Actions than with Travis CI, especially in terms of time spent waiting for a builder.

Clojure Destructuring Tutorial and Cheat Sheet

(Related blog post)

Simply put, destructuring in Clojure is a way extract values from a datastructure and bind them to symbols, without having to explicitly traverse the datstructure. It allows for elegant and concise Clojure code.

Vectors and Sequences

% Git Submodules - The Good + The Bad % Paul Matthews % March 2012

This talk

Submodules
Essentials
Using submodules
Using distributed submodules

	#!/bin/sh
	# Set the AWS environment variables for an AWS profile
	# Useful for docker-machine
	#
	# Example:
	#
	# aws_env profile-for-testing
	#
	# Further information:
	# See the AWS CLI `aws configure`

	import java.io.File;
	import java.io.IOException;
	import java.net.URI;
	import java.net.URISyntaxException;
	import java.nio.file.*;

	// requires JDK 1.7.0+

	Path tmpPath = Paths.get( args[0])
	WatchService watchService = FileSystems.getDefault().newWatchService()

	#!/bin/bash
	/path/to/eclipse &
	P=`which eclipse`
	disown `pidof ${P}`