zopfleech

Zopfleech provides a high-quality deflate compression library and a gzip-compatible command-line tool. The core algorithm is a powerful variant of zopfli, first seen in ECT, which blends key ideas from 7-zip.

About the Project

The name "zopfleech" explains the tributes in the scene:

• It's a variant of zopfli compression algorithm, which is known for its excellent compression ratio with extremely slow speed.
• The core improvement comes from the Efficient Compression Tool (ECT), whose author "leeched" the Binary Tree (BT) match finder from 7-zip to replace the inefficient one in zopfli.
  (Notably, 7-zip's finder is so effective that its deflate encoder can, in some cases, beat vanilla Zopfli even in ratio, all while remaining a practical and reasonable speed.)
• The result is an algorithm that usually beats zopfli in both speed and ratio. This project, in turn, leeches ECT's refined implementation, turning it into a more focused C library and command-line tool.

Key Differences from ECT

• Performance: Up to ~30% faster on AVX (level -9), the higher the level and the bigger the file, the greater the speed improvement. (PR contributed back)
• Reusability: A focused, reusable library with more developer controls vs. an integrated component.
• Goal: Dedicated lib and gzip-replacement archiver with full control vs. a multi-purpose optimizer.

Comparison Chart

The following tests are run on Ubuntu 24.04 WSL @AMD 9950x, All commands ran single-threaded.
zopgz produces byte-identical output to ect 0.95, differing only in the filename stored in the gzip header (ect enforces saving it, whereas zopgz uses the same switch -n as used in gzip to bypass it).

Command	Compressed Size(Ratio)	Time	Compressed Size(Ratio)	Time
Uncompressed Data	629186560(100.0%)	Ubuntu 1604 wsl install.tar	917544960(100.0%)	gcc-15.1.0.tar
gzip -9	206517627(32.82%)	49.61s	171315772(18.67%)	28.71s
zopfli --i1	198128222(31.49%)	585.28s	163697780(17.84%)	564.55s
zopfli (--i15)	197070543(31.32%)	1342.16s	162743248(17.74%)	1869.04s
zopgz -2	195803804(31.12%)	61.50s	163162496(17.78%)	85.63s
7z -tgzip -mx9 -mfb258	195779873(31.12%)	383.01s	162981178(17.76%)	679.82s
ect -gzip -4	194976663(30.99%)	114.19s	162624789(17.72%)	124.48s
zopgz -4n	194976653(30.99%)	110.86s	162624774(17.72%)	110.08s
ect -gzip -9	193833758(30.81%)	1304.69s	162143097(17.67%)	1610.46s
zopgz -9n	193833748(30.81%)	940.74s	162143082(17.67%)	1215.89s

As shown, zopgz at its highest setting (-9) provides the best compression ratio while being 25-30% faster than the original ECT implementation.

Features

lib

• Fully in C (relaxed ANSI C) for max reusability and portability.
  • In-memory and FILE* APIs.
  • Compressing into gzip/zlib/raw deflate streams.
  • No coroutine-style streaming API (feed by chunks).
• Compression Levels: 2-9 (same as upstream ECT project).
• Dependency-Free: The compression functions are self-contained and have no external dependencies (not even zlib).
• No Decpomression: Decompression code is provided as a reusable module within the CLI source for those who need it.

CLI

• gzip-compatible, near-complete replacement.
• default level is -3 (same as ECT, and already compresses more than gzip -9)
• level -1 mapping to backend zlib -9, same idea as ECT but not same compression/speed.
• mixed stdin (with -) with normal files not supported. This often suggests a script error. (zopgz -9 -${EMPTY_VAR} foo)

Building

The project uses a clean and flexible CMake-based build system.

Prerequisites:

• CMake 3.5 or higher with a C compiler.
• zlib (if you want the CLI tool to handle decompression)

Standard Build:

Build both the CLI Tool and a static lib.

mkdir build
cd build
cmake ..
make

In addition, you can add the following arguments to the cmake call:

• -DBUILD_SHARED_LIBS=ON: Build a shared lib. (CLI still links against static lib)
• -DZOPFLEECH_MIN_CPU=AVX2: (x86/x64 only) Build with AVX2 accelerated code. Possibe values are AVX2, AVX, SSE4.2 (the default), SSE2, or an empty string "".

Lib name explained:

While this project is named zopfleech, its API and source code layout is close to upstream zopfli (an old version later heavily modded by ECT), and this project is a perfect replacement of zopfli, so the names in APIs and lib still use zopfli.

Alternative Builds:

• The CMake build system is modular. Both src/ and src/zopfli can act as the top-level CMake entry to build CLI tool or lib only.