Question

I have function with streams(one for input and another for output) as parametrs. It is cryptographic fucnction so streams can be very big. But stream, that function need is not a whole file it is file field.So, how I can put file field(it may be very big so no MemoryStreams etc.) in stream? Sorry for my bad english.

Answer 1

If you mean you meed to supply a Stream that is a part of a file (or any other Stream) then you typically would use one of two approaches:

• create a SubStream : Stream class that encapsulates (decorates) an inner Stream and keeps track of how much data has been read, and only allows Read of “n” bytes (supplied in the constructor), and would return 0 from Read once consumed (also remembering to Max the requested bytes and remaining bytes during Read)
• write your code such that it internally tracks data against some cap, and simply never over-reads

The first is useful if you need to pass that Stream to pre-existing code / libraries.

In both cases, IMO the code that sets up the stream should worry about the “before” data, with the above just worrying about not reading too much.

Edit: here’s one I wrote earlier: http://protobuf-net.googlecode.com/svn/branches/v1/protobuf-net/SubStream.cs