HOLZ: High-Order Entropy Encoding of Lempel-Ziv Factor Distances

Computes the High-Order Entropy Encoding for

• the Lempel-Ziv 77 parsing
• the bit-optimal parsing [1]

build

git clone https://github.com/koeppl/high-order-lz77.git
cd high-order-lz77
git submodule init
git submodule update
mkdir build
cd build
cmake ..
make
./holz -i Makefile

Caveats

The code assumes that there is no \0 byte in the input. One way would be to remove all \0 bytes, but then the decompression would not return the original file. Another way would be to use an escaper such as defined in https://github.com/koeppl/stringology-rust In the following example, we apply this escaper to use the byte 254 as an escape character, so '254' becomes '254 254', and '0' becomes '254 1'.

	cargo build
	cargo run --bin escape -- -i <INFILE> -e 254 -f '0' -t '1' -r -o <OUTFILE>

(Maybe call cargo update -p clap_derive --precise 3.0.0-beta.2 if cargo build fails.) Appending the parameter '-r' reverts the escaping.

Thanks

We used MitI_7's dynamic wavelet-matrix implementation for the experiments, of which we include a modified version in the folder WaveletMatrix

References

• Paolo Ferragina, Igor Nitto, Rossano Venturini: On the bit-complexity of Lempel-Ziv compression. SODA 2009: 768-777, http://dl.acm.org/citation.cfm?id=1496770.1496854