Linux on CuriousCoding

DEFLATE, gzip, zlib, libz, et al.

Mon, 09 Feb 2026 00:00:00 +0100

1 File formats Link to heading

This stuff is all insanely confusing. My summary:

DEFLATE: The ‘original’ compression method. Works in 32kB blocks, and for each stores a small header with the compression mode and optional huffman encoded dictionary. It applies Lempel-Ziv'77 compression of replacing common texts by back-references. It uses a 32kiB context window for this, which may extend beyond the start of the block.
zlib: An implementation of DEFLATE. The file format wraps the raw deflate blocks in a header and footer.
gzip (GNU zip): Another file format around DEFLATE, consisting of a small header containing eg the original file name, then a list of DEFLATE blocks, and lastly a CRC32 checksum.
blocked gzip (BGZF, blocked gzip format): A file format developed for bioinformatics that is just multiple GZIP files concatenated. This allows faster compression and decompression by parallellizing over independent blocks, as well as random access via a small auxiliary index of block starts. This is backwards compatible with plain gzip.

2 Implementations Link to heading

zlib: The original C library.
zlib-ng: Modern C implementation of zlib using SIMD.
libz-sys crate: Rust bindings to zlib and zlib-ng.
zlib-rs crate: Pure Rust re-implementation.
zlib-rs-sys crate: zlib-compatible C-API to zlib-rs
flate2 crate: High level Rust crate with uniform bindings to multiple zlib implementations.

3 Containers Link to heading

Figure 1: Overview of the containers in a (blocked) GZIP file. Mim stores checkpoints at the start of DEFLATE blocks, which do not coincide with the start of GZIP blocks!

Trying to understand DDR memory

Tue, 20 Jan 2026 00:00:00 +0100

Table of Contents

1 Questions
2 A load of articles/blogs/pages to read
- 2.1 Wikipedia articles
- 2.2 More posts
- 2.3 Notes
- 2.4 My own RAM
- 2.5 Continued notes
- 2.6 Address mapping notation
- 2.7 Intel spec
- 2.8 Rank interleaving
- 2.9 Nontemporal reads/writes
3 reMap: using Performance counters
4 Sudoku
- 4.1 Step 1: DRAM addressing functions
- 4.2 Step 2: row/column bits
- 4.3 Step 3: validation
- 4.4 Step 4: which function is what?
- 4.5 Refreshes
- 4.6 Consecutive Accesses
5 Sudoku, now with only 1 DIMM
- 5.1 setup
- 5.2 1. reverse functions
- 5.3 2. identify bits
- 5.4 3. validate mapping
- 5.5 4. decompose functions
6 Final results
7 decode-dimms
- 7.1 Bank groups
- 7.2 Refresh
- 7.3 Random access throughput
8 CPU benchmarks
- 8.1 cpu-benchmarks
  - 8.1.1 random access throughput 1 DIMM
  - 8.1.2 random access throughput 2 DIMM
- 8.2 memory-read-experiment
  - 8.2.1 strided reading 1 DIMM
  - 8.2.2 strided reading 2 DIMM
9 tinymembench
10 Remaining questions

These are chronological (and thus, only lightly organized) notes on my attempt to understand how DDR4 and DDR5 RAM memory work.

Setting up traffic monitoring using GoAccess

Sat, 04 Jan 2025 00:00:00 +0100

Table of Contents

1 Nginx setup
2 GoAccess configuration
3 Systemd setup
4 Serving the static file
5 Serving live statistics
6 GeoIP database

GoAccess (goaccess.io, github) is a tool that analyses server logs and gives real-time statistics on network traffic. It took me some time to figure out exactly how to get the real-time websocket server working through Nginx, so I’m just sharing my configuration here.

Install via your package manager, e.g. sudo pacman -S goaccess on Arch.

Detached fullscreen in Sway

Fri, 02 Jul 2021 00:00:00 +0200

Backlinks: PR for Sway | AUR package sway-inhibit-fullscreen-git

Once upon a time, Chromium had a bug where using $mod+f in i3 to fullscreen the Chromium window changed the window to occupy the entire screen, but didn’t actually make Chromium enter full screen mode. According to some, those¹ were² the³ good⁴ days⁵^,⁶. Watching 4 YouTube streams in parallel was still possibly, back in those days:

Without patches, the best we can do nowadays⁷ is the following

Open source contributions

Fri, 02 Jul 2021 00:00:00 +0200

Table of Contents

My aur packages
Some issues I reported/fixed

My aur packages Link to heading

List on aur.archlinux.org

bapctools-git: BAPCtools is used for developing ICPC style programming contest problems.
feh-preload-next-image-git: Branch of Feh that loads the next image to speed up browsing images in a remote directory.
i3-focus-last-git: Window switcher for i3/sway.
python-pyexiftool-nocheck: the original python-pyexiftool is outdated, orphaned, and still depends on python2.
sway-inhibit-fullscreen-git: Sway branch that adds the inhibit_fullscreen toggle command. Bind this to e.g. $mod+Shift+f to disconnect the Sway full screen status from the application full screen status. Used to e.g. watch YouTube videos in Chromium in full screen mode, but in a window that is only a quarter of the screen.

Some issues I reported/fixed Link to heading

vimium/issues/3557 after searching and hitting Enter, vimium freezes and needs a mouse click to unfreeze. n and N do not work.
- fix here: add a missing return statement after many hours of debugging
vimium/issues/3844 Bug: Last characters dropped when using custom search engine
- duplicate of issues/3567
- PR pull/3846
sway/pull/6286 Add anything option to Grimshot to allow selecting either a window, output, or manual area.
mako/issues/358 Feature Request: Dismiss all notifications with given category
slurp/issues/87 Moving the mouse to a different output does not always grey out rectangles
slurp/issues/86 Clicking outside all rectangles should cancel
sway/issues/6299 Unexpected next_on_output behaviour with workspace_auto_back_and_forth
- follow-up PRs: 6332: cleanup, 6334: more cleanup, 6335: .clang-format
Signal-Desktop/issues/5307 ctrl-2 broken under Wayland

Powersearch with Vimium

Fri, 02 Jul 2021 00:00:00 +0200

Related posts: Dark mode with Vimium

Vimium (Github, Chromium extension) is not only a great way to navigate webpages; it’s also a great help to quickly search many webpages.

I am using it many times a day to search for just the documentation I need. Some of the search engines I have configured:

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# Documentation
archwiki: https://wiki.archlinux.org/index.php?search=%s ArchWiki
aur: https://aur.archlinux.org/packages/?K=%s AUR
cpp: https://en.cppreference.com/mwiki/index.php?search=%s CppReference
github: https://github.com/search?q=%s GitHub
hoogle: https://www.haskell.org/hoogle/?hoogle=%s Hoogle
oeis: https://oeis.org/search?q=%s OEIS
python: https://docs.python.org/3.7/search.html?q=%s Python
wiki: https://en.wikipedia.org/w/index.php?title=Special:Search&search=%s Wikipedia

# Translation
nlen: https://translate.google.nl/#nl/en/%s Dutch -> English
ennl: https://translate.google.nl/#en/nl/%s English -> Dutch
deen: https://translate.google.nl/#de/en/%s German -> English
ende: https://translate.google.nl/#en/de/%s English -> German

# Other
imdb: https://www.imdb.com/find?q=%s IMDB
# `pe 123` to jump straight to problem 123.
pe: https://projecteuler.net/problem=%s Project Euler
kattis: https://open.kattis.com/search?q=%s Kattis

Any of these can now be activated by typing their shorthand in the omnibar (which is usually activated by pressing o or O). Vimium even has live preview support for Wikipedia and Google search, as well as some others.

Wayland utilities

Fri, 02 Jul 2021 00:00:00 +0200

This post goes over some useful utilities I have been using on my Wayland system.

Screen brightness: `light` Link to heading

Light is a nice tool to manage screen and keyboard brightness.

Install light
Add your user to the video group: usermod -aG video <user>

I really like the light -T flag, which multiplies the current brightness by some value. This way you can have fine grained control both for very low and very high brightness values. To prevent yourself from decreasing the brightness all the way to 0, you can run e.g. light -N 0.2 to set a minimium screen brightness of 0.2. This value will be stored in your config directory under ~/.config/light/.

Browsing in the dark with Vimium and Dark Reader

Thu, 01 Jul 2021 00:00:00 +0200

Table of Contents

Chromium theme
Dark Reader
Vimium

Let’s quickly go over some settings you can change for a better dark mode experience in Chromium.

Chromium theme Link to heading

First of all, you can make Chromium itself use a dark theme. This will ensure both a dark tab bar and nice dark settings pages. As explained here, you’ll need to change the following:

Window switching in Sway

Thu, 01 Jul 2021 00:00:00 +0200

Sway has many commands for switching the active workspace and focused window. However, I find that most of my window switching comes down to a few simple commands that focus a specific application, or open it first when it has no open windows yet. E.g.:

$mod+s: open and/or focus slack
$mod+i: open and/or focus signal
$mod+m: open and/or focus emacs
$mod+c: open and/or focus chromium

In addition to this, some apps like emacs have a separate $mod+Shift+m command that always opens a new window/instance.

Clean your homedir with XDG Base Dir

Wed, 30 Jun 2021 00:00:00 +0200

Links: XDG specification | ArchWiki | Reddit post

In case you are, like me, tired of applications polluting your homedir with config and data files, the XDB Base Directory Specification (ArchWiki) has your back.

You probably saw the ~/.config directory already, and in fact, many programs can be told to use this directory instead of polluting your homedir. The ArchWiki page has a list of many applications and which environment variables need to be set to change the location of their configuration.

Emacs Doom

Wed, 30 Jun 2021 00:00:00 +0200

Table of Contents

Configuration
- init.el
- config.el
Running as server and client
Wayland
Useful commands
Emacs as mail client

Install Doom Emacs as explained in the readme.

Alongside it, you’ll want to install ripgrep and fd for better search integration, and possibly ttf-font-awesome for better icons.

Configuration Link to heading

Instead of the default ~/emacs.d/ and ~/doom.d/ config directories, you can also use ~/.config/emacs/ and ~/.config/doom/.

Environment variables done once

Wed, 30 Jun 2021 00:00:00 +0200

Links: GitHub issue

One problem I had with my Sway setup is that setting environment variables in my config.fish (the Fish equivalent to .bashrc or .zshrc) is not always sufficient.

In particular, I need my environment variables to be available in at least the following places:

my Fish shell,
applications launched from Sway (e.g. using keybindings),
applications launched as a systemd service (e.g. the Emacs server daemon).

Setting variables in the shell profile has the problem that they are not picked up by systemd services. Another option seems to be ~/.pam_environment, but this is deprecated.

X1 Extreme Gen 3 - Migrating to Wayland

Sun, 16 May 2021 00:00:00 +0200

I got a new laptop, so this felt like the right time to migrate to Wayland.

Delta Link to heading

what	before	after
hardware
laptop	Asus UX501V	Lenovo X1 Extreme Gen 3
CPU	i7-6700HQ	i7-10750H
GPU	GTX 960M	GTX 1650
RAM	16GB	64GB
OS
bootloader	Grub	EFISTUB
OS	Windows + Arch dualboot	Windows + Arch dualboot
networking	netctl	systemd-networkd
dns/dhcp	dhcpcd	systemd-resolved
wifi	wpa_supplicant	iwd
Wayland
display/login manager	-	-
display server	X	Wayland
window manager	i3	Sway
bar	i3blocks	waybar
backlight	xbacklight	light
night mode	redshift	gammastep
clipboard	-	wl-clipboard, clipman
program launcher	rofi	rofi [wayland]
password finder	rofi-pass	rofi-pass-git
key remapping	setxkbmap, xcape, xmodmap	interception-tools
Tools
terminal emulator	urxvt	foot
shell	zsh	fish
shell highlighting	zsh-syntax-highlight	-
environment variables	.zshrc	environment.d
text editor	vim	emacs doom
aur helper	packer	yay
directory usage	du	dust
password manager	pass	pass
search tool	ag [silver searcher]	ag + ripgrep + fd
file browser	terminal	terminal + ranger
calculator	qalc	qalc, rofi-calc
notification deamon	dunst	mako
image viewer	feh	feh + sxiv
music	-	spotifyd + spotify-tui + waybar custom/media
screenshot	teiler+scrot	grimshot (from sway) + custom upload wrapper
wallpaper	feh	sway
messenger	slack, signal-desktop	slack, signal-desktop [wayland]
system monitor	htop	htop
remote shell	ssh	ssh
browser	chromium	chromium
pdf viewer	zathura	zathura
vpn	-	openconnect

see also the i3 -> sway migration guide.

Linux on CuriousCoding

DEFLATE, gzip, zlib, libz, et al.

1 File formats Link to heading

2 Implementations Link to heading

3 Containers Link to heading

Trying to understand DDR memory

Setting up traffic monitoring using GoAccess

Detached fullscreen in Sway

Open source contributions

My aur packages Link to heading

Some issues I reported/fixed Link to heading

Powersearch with Vimium

Wayland utilities

Screen brightness: light Link to heading

Browsing in the dark with Vimium and Dark Reader

Chromium theme Link to heading

Window switching in Sway

Clean your homedir with XDG Base Dir

Emacs Doom

Configuration Link to heading

Environment variables done once

X1 Extreme Gen 3 - Migrating to Wayland

Delta Link to heading

Screen brightness: `light` Link to heading