Eremey Valetov
4c5661eb33
Replace the fixed first-4KB FNV-1a prefix matching with content-defined chunking. Files are now split into ~4KB CDC chunks (Gear rolling hash), each chunk hashed with FNV-1a. Files sharing any chunk hash are grouped for master-block deduplication. This detects shared content at ANY position in the files, not just identical file prefixes. The improvement matters for: - Patched executables (same code, different version strings) - Edited documents (same body, different headers) - Similar data files (shared structures at varying offsets) The fallback master assignment (for backward compat with original UC2 Pro) still applies to ungrouped files, ensuring all files use custom master indices (>= 2). All 7 tests pass including master dedup round-trip and CDC unit tests.
UC2 v3.0.0 — UltraCompressor II
A cross-platform revival of UltraCompressor II, the DOS-era archiver by Nico de Vries (1992--1996). UC2 was notable for its advanced deduplication ("master blocks"), file versioning, and competitive compression ratios on the hardware of its day.
This project brings UC2 back as a modern, portable C99 tool. Phase 1 (current) provides decompression and archive listing, built on Jan Bobrowski's clean-room portable decompressor (unuc2/libunuc2). Phase 2 will add compression using the original algorithms.
Building
Requires CMake >= 3.16 and a C99 compiler (GCC, Clang, or MSVC).
cmake -B build
cmake --build build
The binary is at build/cli/uc2.
Usage
uc2 archive.uc2 # Extract all files
uc2 -l archive.uc2 # List contents
uc2 -t archive.uc2 # Test archive integrity
uc2 -d /tmp/out archive.uc2 # Extract to directory
uc2 -l archive.uc2 '*.txt' # List matching files
uc2 -p archive.uc2 readme.txt # Extract to stdout
Options
| Flag | Description |
|---|---|
-l |
List archive contents |
-t |
Test archive integrity |
-a |
Include all file versions (not just latest) |
-d path |
Extract to specified directory |
-f |
Overwrite existing files |
-p |
Extract to stdout |
-D |
Skip directory metadata; -DD also skips file metadata |
-T |
Tab-separated output (for scripting) |
Project Structure
UC2/
lib/ libuc2 decompression library
cli/ uc2 command-line tool
original/ preserved original sources (reference only)
cmake/ build system modules
tests/ test archives and test programs
History
- v1.0--v2.3 (1992--1996) Original DOS releases by Nico de Vries
- 2015 Source code released under LGPL-3.0 by Danny Bezemer
- 2020--2021 Jan Bobrowski writes unuc2/libunuc2 (portable decompressor)
- 2026 UC2 v3.0.0: cross-platform revival
License
GPL-3.0. See LICENSE and CREDITS.md for full attribution.