Entropy Coders

Entropy coders reduce a set of symbols according to their appearance probabilities.
They are typically used as stage 2 of many compression programs, including zip, rar or 7zip.

1) Range0
New : Slightly improved compression rate, compression animation report (cosmetic)
This is a semi-static Range Coder implementation. Data is divided into blocks of 256KB. Each compressed block starts with a frequency count header.
Compression speed : 130 MB/s
Decoding speed : 65 MB/s
enwik8 ratio : 1.578
enwik8-lz4-ml : 2.952

2) Huff0
New : Small speed improvement
This is a semi-static huffman coder implementation. Data is divided into blocks of 16KB. Each compressed block starts with a huffman tree header.
Compression speed : 210 MB/s
Decoding speed : 195 MB/s
enwik8 ratio : 1.585
enwik8-lz4-ml : 2.915


Comparing with other entropy coders :

Shindlet, from Piotr Tarsa, an optimized order-0 dynamic range coder written in assembler.
Compression speed : 18 MB/s
Decoding speed : 16.5 MB/s
enwik8 ratio : 1.590 (best ratio)
enwik8-lz4-ml : 2.895

o0c from Eugene Shelwien, a reference fully adaptative dynamic range coder
Compression speed : 5 MB/s
Decoding speed : 4.7 MB/s
enwik8 ratio : 1.585
enwik8-lz4-ml : 2.965 (best ratio)

Huff0
Improved compression rate

Range0
Initial release

Huff0
More flexible I/O, more precise benchmark, slightly improved compression rate

Huff0
improved decoding speed

Huff0
initial release