Projects (non-commercial)

I've written a lot of stuff so far. In the following I present a selection of relevant texts and projects.


Compiler construction course [German only, 3 parts]
I've written a compiler construction course for beginners (including a demo interpreter called Blogmath). The course is available online for free (part 1, part 2, part 3).
Internet security [German only]
End-user internet security is an important topic nowadays. In 2011 I've written a compact and easy-to-understand overview article which describes most of the pitfalls and techniques which are being used today to protect end-users.


Route planner (for bicycles, cars, short-range transit)

I've written an online route planning software, primarily for cyclists (but it got also profiles for cars; short-range transit is planned). It provides a developer-friendly API and a simple user interface. It's written entirely in Golang and HTML/CSS. A HTML5 track-by-track navigation is planned as well.

The code is open sourced under the MIT license on GitHub (flosch/routeplanner).

Currently only Berlin (Germany) and the surrounding region is supported. More to come.

pongo2 playground

I've written a playground for the pongo2 template engine.

trindex: trigram search for Go (demo)

Demo search page with all German Wikidata lemmas (4064962 in total) being indexed using my library trindex.

Development libraries

simpleapi (Python)
A simple API-framework to provide an easy to use, consistent and portable client/server-architecture (standalone and also for django, Flask, AppEngine and all WSGI-compatible implementations like gunicorn).
pongo2 (Golang)
Template-engine and successor of pongo. [see my blog post]
pongo (Golang)
A template engine which implements a Django-template-like syntax.
trindex (Golang)
A trigram (fuzzy) search library for Go.
libdht (Python)
Pure python library for implementing a simple DHT based on the Kademlia protocol. [see my blog post about libdht as well, German only]
A simple RPC-framework written in Python [relevant blog post]

Demos and proof-of-concepts

In the last few years I've written a lot of demos and proof-of-concepts which I haven't published yet in source code. This list presents a few of them.

A proof-of-concept which allows signing into a web account using an Android smartphone and QR codes.
Peer-to-peer instant messenger (with screencast)
A peer-to-peer instant-messenger which - obviously - does not need a central server. It's entirely based on public-key-cryptography and is using a DHT-algorithm similar to Kademlia. Implemented using my libdht.
Automatic encryption and anonymization of incoming e-mails using OpenPGP (with screencast)
A mail (smtp) server (written in Golang) which allows creating mail boxes using an API and which anonymizes and encrypts every incoming mail using public-key-cryptography (in OpenPGP-format). You can receive any incoming, encrypted mail using the API.
Private browser-to-browser file sharing (with screencast)
A modern approach to realize easy browser-to-browser file sharing.


GoPy [related blog post in German]
GoPy is a Python-interpreter which executes compiled Python-bytecode. GoPy is written entirely in Golang.
jspy [demo (known to be broken due to some browser changes in the last few years)]
Same as GoPy, but written in JavaScript. A rudimentary Python-interpreter.
A Light Cycle game (with network support). Written entirely in Python.

... and a lot more including compilers, databases, distributed systems, virtual machines and Android apps.