Support streams when sending and/or receiving

Describe the feature request

The MqttApplicationMessage only supports byte[] but it would be nice if it would support a Stream object. The MQTT spec allows for 256MB payloads and using streams makes sense from both when sending and receiving. For example, the ability to pass a FileStream and especially useful if the stream is still being written to.

Is your feature request related to a problem? Please describe. A clear and concise description of what the problem is. Example. I’m am trying to do […] but […]

Which project is your feature request related to?

• Client

Describe the solution you’d like

Support streams when sending and/or receiving

Describe alternatives you’ve considered

The payload byte[] requires all data to be first loaded into memory which is not ideal when dealing with large data fragments and results in unneeded memory pressure.

[mg90707]

@ramonsmits I think it would have to be a ReadOnlyMemory<Byte> as a Spans can only exists on the Stack, not the Heap.

[mg90707]

@chkr1011 Just a small suggestion: Wouldn’t just allocating a new buffer here

https://github.com/chkr1011/MQTTnet/blob/b88924bce50671b4270282f4ca7ec10e429eaa49/Source/MQTTnet/Formatter/MqttPacketWriter.cs#L214

be more effective as Array.Resize also copies the old contents over to the new, shrinked buffer (at least as much as possible)? Doesn’t seem necessary to me when the buffer will be overwritten with the contents of the next message anyways.