DCing algorithm

[Dia6lo]

Are you sure that the code opens the file every byte?
I do not know much about C#, but I would imagine that it opens the file once, and then reads every byte separately, which is obviously still causes a major slowdown, but not nearly the same as opening the file each time a byte is read.

Good job on improving the code.

Thanks. AFAIK opening files is more expensive(in performance terms) operation than reading data from opened ones. And FileStream just gives you interface to operate with given file(and doesn't read any data from it). So, everytime by calling ReadByte() you ask computer to open file and read a single byte, while File.ReadAllBytes() opens file once and reads all data in one go. While first method is memory-friendly and usually used to read small amounts of data, latter is more fast in reading large chunks of data.
OFC I've done other optimisations(by using LINQ and Enumerators), but ReadByte() caused main slowdown.