TypedArray fail to serialize

[galvesribeiro]

Hello folks!

While I was implementing Blazor.Extensions.WebUSB, I had to send/receive buffers to the USB device connected. In C#, I was sending byte[] down to JS and it was working perfectly fine. However, when I was sending a buffer back from JS to C#, it fail without any errors since it was unable to deserialize the Uint8Array into a byte[]. It just hang on the resolve(array) call.

After a day trying to figure out what is going on, I noticed that if I convert it to a regular array it works perfectly with Array.prototype.slice.call(new Uint8Array(out.data.buffer)). That is very inefficient...

The reason for that (looks like) is because we don't have support to deserialize TypedArrays on SimpleJson...

The same problem happens on Blazor.Extensions.SignalR when we have a callback that expects a byte[].

Look at the examples here and here.

Do we have a less hacky/slow alternative to this?

Thanks!

[danroth27]

Thanks for pointing this limitation out to us!

Do we have a less hacky/slow alternative to this?

Not that I'm aware of

[vertonghenb]

Same issue with sending Enums up and down to JS(without parsing them to int).
However the performance loss is nothing compared to the arrays.

[SteveSandersonMS]

Check how Blazor's WebAssembly HTTP client deals with returning a large byte array from JS to C#.

Fundamentally you do have to copy the data at least once, because a JavaScript object isn't a .NET object and can't participate in the GC system directly. So for HTTP, the JS code asks the .NET code to allocate a byte[] of the desired size, then it copies the data into the .NET memory heap at that location.