How can I split (copy) a Stream in .NET?

Question

Does anyone know where I can find a Stream splitter implementation?

I\'m looking to take a Stream, and obtain two separate streams that can be independently read a

Answer 1

With the introduction of async / await, so long as all but one of your reading tasks are async, you should be able to process the same data twice using only a single OS thread.

What I think you want, is a linked list of the data blocks you have seen so far. Then you can have multiple custom Stream instances that hold a pointer into this list. As blocks fall off the end of the list, they will be garbage collected. Reusing the memory immediately would require some other kind of circular list and reference counting. Doable, but more complicated.

When your custom Stream can answer a ReadAsync call from the cache, copy the data, advance the pointer down the list and return.

When your Stream has caught up to the end of the cache list, you want to issue a single ReadAsync to the underlying stream, without awaiting it, and cache the returned Task with the data block. So if any other Stream reader also catches up and tries to read more before this read completes, you can return the same Task object.

This way, both readers will hook their await continuation to the result of the same ReadAsync call. When the single read returns, both reading tasks will sequentially execute the next step of their process.