SHITPRESS

Super tiny/KISS/suckless C compression library + utility. Features:

- single header library, no linking bullcrap:
  - fewer than 200 lines of PURE C99, extremely small and nonbloated
  - both compression and decompression are streaming! no file buffers needed
  - constant memory complexity, super low RAM requirements (a few bytes)
  - linear time complexity, super fast
  - ABSOLUTELY ZERO dependencies, not even standard library is used
  - very simple algorithm (see source code for its description)
  - still OK compression ratios (see table below) up to a maximum of 33% (the
    best the algorithm can do is to reduce a 6 byte sequence to a 2 byte
    sequence), of course some inputs may end up being enlarged (this is
    mathematically unavoidable and the fact that the file can be enlarged by
    more than 1 bit follows from the streaming nature of the algorithm, that's
    common even among common compression utils like lz4)
- two executable utilities using the library also included:
  - shitpress: Super simple, fast, streaming, max. compression ratio 33%.
  - supershitpress: Non-streaming, repeatedly compresses as long as file size
    reduces, potentially compresses more (even to less than 1%!) but is slower,
    eats more RAM and uses malloc. Guarantees to never enlarge a file by more
    than 1 byte (unlike normal shitpress)!
- everything completely public domain under CC0, no legal requirements at all,
  do literally anything you want to without bullshit like giving credit etc.
- generally usable for any type of data, not assuming any specific use (such as
  file compression), i.e. can be used in any wild hacking style (e.g. to
  compress stuff in RAM on low-RAM embedded computers etc.)
- everything super KISS/suckless, no bullshit, no furry mascot, no COC, fuck
  soydev idiots

Here are some measured stats for shitpress, supershitpress and a commonly used
lz4 utility (sizes in bytes):

input                    orig    compressed   compressed  compr. r.  compr. r. | compressed compr. r.
                         size    (shitpress) (supershit.) (shitpr.) (supersh.) |   (lz4)     (lz4)
-------------------------------------------------------------------------------+---------------------
100000 "A"s txt          100002  33339       134          33.3%     0.1% !!!   | 422        42.0%
WM Commons screens. raw  3072000 1522151     1018285      49.5%     33.1%      | 721531     23.4%
shitpress binary         30888   16995       16896        55.0%     54.7%      | 12859      41.6%
shitpress source         4886    3834        3836         78.4%     78.5%      | 580        75.3%
Wikip. main page HTML    96085   78957       78959        82.1%     82.1%      | 32459      33.7%
Flatland (txt book)      219615  197874      197876       90.1%     90.1%      | 135782     61.8%
100000 pi digits txt     100002  94254       94256        94.2%     94.2%      | 95354      95.3%
Lenna raw image          1048576 1023261     1023263      97.5%     97.5%      | 1039481    99.1%
Willhelm scr. raw audio  155858  152170      152172       97.6%     97.6%      | 152434     97.8% 
100% random data         1024    1027        1025         100.2%    100.0%     | 1043       101.8%
forged malicious data    100     200         101          200.0%    101.0%     | 30         30.0%

by drummyfish, 2023, released under CC0 1.0, public domain
(https://creativecommons.org/publicdomain/zero/1.0/)