Why do most serializers use a stream instead of a byte array?

Question

I am currently working on a socket server and I was wondering Why do serializers like

• XmlSerializer
• BinaryFormatter
• Protobuf-net
• DataContractSerializer

all require a Stream instead of a byte array?

Answer 1

It means you can stream to arbitrary destinations rather than just to memory.

If you want to write something to a file, why would you want to create a complete copy in memory first? In some cases that could cause you to use a lot of extra memory, possibly causing a failure.

If you want to create a byte array, just use a MemoryStream:

var memoryStream = new MemoryStream(); serializer.Write(foo, memoryStream); // Or whatever you're using var bytes = memoryStream.ToArray(); 

So with an abstraction of "you use streams" you can easily work with memory - but if the abstraction is "you use a byte array" you are forced to work with memory even if you don't want to.

Answer 2

You can easily make a stream over a byte array...but a byte array is inherently size-constrained, where a stream is open-ended...big as you need. Some serialization can be pretty enormous.

Edit: Also, if I need to implement some kind of serialization, I want to do it for the most basic abstraction, and avoid having to do it over multiple abstractions. Stream would be my choice, as there are stream implementations over lots of things: memory, disk, network and so forth. As an implementer, I get those for "free".