Buffering NSOutputStream used as NSInputStream?

Question

I have this consumer class that takes an NSInputStream as argument which will be processed async, and I want to push data that comes from a producer class that requires that

Answer 1

You might want to consider subclassing NSInputStream, and wrapping the source stream in your new class that buffers and/or modifies the bytes as they pass through.

The main reason I found for doing this over the bound sockets approach is to support seeking. File based NSInputStreams use a stream property to seek within the file, and I couldn't easily arrange this without subclassing.

A problem with this approach is that it seems toll-free bridging won't work for you subclass - but there is a very nice article that will also give you a template subclass to start from if you need one:

http://bjhomer.blogspot.co.uk/2011/04/subclassing-nsinputstream.html

I got a buffering solution working using both approaches - although another issue I had with the subclass approach is that you need to take care to send events to listeners appropriately - for example, when your source stream sends you an EOF event, you won't pass it on to your consumer until they have emptied the buffer - so there is some messing about to do there.

Also - you might need to ensure that clients do their reading off the main run loop (I got it working with grand central dispatch) - because any observing you do in your subclass - on the source stream - will clash with the consumer otherwise. Although you appear to be able to pick any run loop to observe streams on, only the main one works.

So overall I'd say go with the paired streams unless you need to support seeking - or are particularly averse to the paired streams method.