C# port of Finite State Entropy codecs (https://github.com/Cyan4973/FiniteStateEntropy).
using FileStream fInput = File.OpenRead(@"C:\Data\input.dat.fse");
using FileStream fOutput = File.OpenWrite(@"C:\Data\output.dat");
using var fse = new FseStream(fInput, CompressionMode.Decompress, leaveOpen: true);
fse.CopyTo(fOutput);
using FileStream fInput = File.OpenRead(@"C:\Data\input.dat");
using FileStream fOutput = File.OpenWrite(@"C:\Data\output.dat.fse");
using var fse = new FseStream(fOutput, CompressionMode.Compress, leaveOpen: true);
fInput.CopyTo(fse);