Can we disable the NSStream bytes/space available callbacks using CFSocketDisableCallbacks() on NSStream underling socket?

Now is there any way we can disable NSStream read/space callbacks and enable it again as this is possible with CFSocket.

Not really. You could try unscheduling the stream but that’d put you well off the beaten path.

I tried to get the underlying socket of the NSStream … and tried to call

CFSocketDisableCallbacks

on it but it did not disable the bytes/space available callbacks.

CFSocketStream does not necessarily use CFSocket. There used to be a direct relationship back in the day but things have moved on a lot since then.

The reason behing this is I do not want to keep buffer for storing the read bytes from NSInputStream and the consumer for those bytes is asynchronous.

I’m not sure I understand your requirements, but it sounds like you can simply stop responding to

.HasBytesAvailable

messages. When you use NSStream in async mode, I/O is based on an ‘interlock’ mechanism:

1. you get a

   .HasBytesAvailable

   event

2. you make a

   read(_:maxLength:)

   call

3. you get another

   .HasBytesAvailable

   event

Similarly for

.HasSpaceAvailable

and

write(_:maxLength:)

.

Step 3 doesn’t happen until step 2 is done. Thus, if you want to implement receive-side flow control on the stream (because of send-side flow control on your sink), skip step 2. Typically this involves a flag to record that you got, and ignored, a

.HasBytesAvailable

event. That way, when send-side flow control is lifted on the sink, you know that you can immediately resume at step 2.

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—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Thanks Quinn. I would try this.

Is is also the case with 'getBuffer'? Can I use 'getBuffer' instead of read and the NSStream would not call bytesAvailable until I call getBuffer?

Is is also the case with 'getBuffer'?

-getBuffer:length:

is quite useless (I’ve been working with NSStreams for decades and I’ve never found any place where it actually helps). In the case of a socket stream,

-getBuffer:length:

will always returns false because the socket buffer is inside the kernel, and thus not accessible to code running in your process.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"