A minimalistic LZW (Lempel–Ziv–Welch) compression and decompression tool implemented in CPP and CMake as a header only project. Supports dictionary growth up to 15-bit codes (max code = 32767) and a “stop-growing dictionary” strategy once the dictionary is full.

• Encoding (compression):

  • Reads from a file or stdin.
  • Produces an .lzw file or writes to stdout (depending on environment variables).
  • Uses a variable code size, starting at 9 bits, up to a maximum of 15 bits.
  • Stops adding new dictionary entries once nextCode hits 32767, but continues encoding with existing entries.

• Decoding (decompression):

  • Can reads from any file, should be a .lzw file, or stdin.
  • Produces a decompressed output file (output.out) or writes to stdout based on CLI Env variable.
  • Mirrors the encoder’s logic (9-bit initial code size, grows to 15 bits).
  • Ignores any leftover bits that cannot form a valid code (to avoid out-of-range dictionary references).

• Threading and Parallelism:

  • Supports encoding / decoding multiple files at times using threads up to a maximum of 8.
  • For example, you can call ./encode <filename[1]> <filename[2]> ... <filename[8]>.
  • Has shown promising results when processing multiple, considerably big sized files.

Building lzip requires the following software installed:

• A C++17-compliant compiler
• CMake >= 3.9
• Doxygen (optional, documentation building is skipped if missing)

The following sequence of commands builds lzip. It assumes that your current working directory is the top-level directory of the freshly cloned repository:

mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release ..
cmake --build .

The build process can be customized with the following CMake variables, which can be set by adding -D<var>={ON, OFF} to the cmake call:

• BUILD_TESTING: Enable building of the test suite (default: ON)
• BUILD_DOCS: Enable building the documentation (default: ON)

When built according to the above explanation (with -DBUILD_TESTING=ON), the C++ test suite of lzip can be run using ctest from the build directory:

cd build
ctest

lzip provides a Sphinx-based documentation, that can be browsed online at readthedocs.org. To build it locally, first ensure the requirements are installed by running this command from the top-level source directory:

pip install -r doc/requirements.txt

Then build the sphinx documentation from the top-level build directory:

cmake --build . --target sphinx-doc

The web documentation can then be browsed by opening doc/sphinx/index.html in your browser.