Hydra zh4n7wm

One-line Tree in Python

Using Python's built-in defaultdict we can easily define a tree data structure:

def tree(): return defaultdict(tree)

That's it!

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Do not use this guide. The dnscrypt protocol and dnscrypt-proxy configuration file have changed a lot since I wrote this gist. Check the following links for help:

Install & Configure

Install DNSMasq

$ brew install dnsmasq

Docker - How to cleanup (unused) resources

Once in a while, you may need to cleanup resources (containers, volumes, images, networks) ...

delete volumes

// see: https://github.com/chadoe/docker-cleanup-volumes

$ docker volume rm $(docker volume ls -qf dangling=true)

$ docker volume ls -qf dangling=true | xargs -r docker volume rm

How to recover lost Python source code if it's still resident in-memory

I screwed up using git ("git checkout --" on the wrong file) and managed to delete the code I had just written... but it was still running in a process in a docker container. Here's how I got it back, using https://pypi.python.org/pypi/pyrasite/ and https://pypi.python.org/pypi/uncompyle6

Attach a shell to the docker container

Install GDB (needed by pyrasite)

apt-get update && apt-get install gdb

If you created your key pair using AWS, you can use the OpenSSL tools to generate a fingerprint as follows:

$ openssl pkcs8 -in path_to_private_key -inform PEM -outform DER -topk8 -nocrypt | openssl sha1 -c

If you created a key pair using a third-party tool and uploaded the public key to AWS, you can use the OpenSSL tools to generate the fingerprint as follows:

$ openssl rsa -in path_to_private_key -pubout -outform DER | openssl md5 -c

	#!/usr/bin/python2


	# Copyright (C) 2016 Sixten Bergman
	# License WTFPL
	#
	# This program is free software. It comes without any warranty, to the extent
	# permitted by applicable law.
	# You can redistribute it and/or modify it under the terms of the Do What The
	# Fuck You Want To Public License, Version 2, as published by Sam Hocevar. See

	#!/bin/bash
	set -x

	cd ${0%/*}/..

	# codesigning and choosing of provisioning profile is configured via project settings and is dependent of build config

	: ${BUILD_NUMBER:?"Need to set BUILD_NUMBER"}

	WORKSPACE=<yourworkspace>.xcworkspace

	package main

	import (
	"fmt"

	"github.com/ethereum/go-ethereum/accounts"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/ethereum/go-ethereum/crypto"
	)

	#!/bin/bash
	#
	# Install specific version of a Homebrew formula
	#
	# Usage: brewv.sh install\|upgrade formula_name desired_version
	#
	# Notes:
	# - this may unshallow your brew repo copy. It might take some time the first time
	# you call this script.
	# - my "git log" uses less by default and when that happens it breaks the script