Re: JsInterop and Java collections?

On Friday, June 10, 2016 at 11:12:27 AM UTC+2, Kirill Prazdnikov wrote:

Hi Thomas

Lets forget about java.util, what about simple arrays ? 

It seems that we already have java [] array -> JS Array marshalling. 

And It would be very nice if we had these type of marshalling with zero performance penalty:

 java byte[] -> Int8ArrayNative

 java short[] -> Int16ArrayNative

 java float[] -> FloatArrayNative

Currently, there is no way of writing GWT compatible portable code that operates with  byte[] short[] int[] float[] without java array[] -> JS TypedArray performance issues

I think there was an experiment to actually implement byte[] et al. as JS typed arrays, but there were issues with it (browser compatibility to begin with, meaning that some browsers would have JS Arrays and some JS typed arrays, so interop with JS would be made harder and errorprone; not to mention that the compiler would then need to know which kind of output it needs to use depending on the permutation, something I don't know it can do today; backwards compatibility: some libraries rely on "conversion" from one type to another by passing through the JSNI boundary, so you can easily send a int[] to JSNI and have it return back the same object as a double[] –maybe–, using an Int32Array to implement int[] would break that; also casting to Object[] conflicts with the new-implemented treatment of java.lang.Double the same as 'double', so double[] and java.lang.Double[] are implemented the exact same way, so you could retrieve a JS Float64Array as a java.lang.Double[] and then it would likely break when cast to Object[])

In the end, JS type arrays are more like typed java.nio.Buffers (java.nio.DoubleBuffer, etc.) than arrays; so you'd better work with a similar abstraction than with Java arrays.

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