syscall/js: no method to convert TypedArrays into slices

[superp00t]

You can convert a Go slice into a TypedArray by using js.TypedArrayOf(...), but there is apparently no way of doing the reverse operation.

You can write a function to Index() every byte value in an ArrayBuffer and put them in a byte slice, but this is cumbersome and incurs unacceptable overhead. There should be a function to directly copy the bytes into the Go heap, such as what js.Value.String() does.

[katiehockman]

/cc @neelance

[neelance]

WebAssembly is only able to access typed arrays which are backed by WebAssembly's memory. This does not hold for all typed arrays, so a mapping with direct access to the typed array is not possible. The best solution is to allocate a correctly sized byte slice in Go, pass it to JS with TypedArrayOf and then use https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/set to quickly copy all bytes.

[superp00t]

@neelance Thanks a lot, doing that solved my problem.

[bradfitz]

I added metadata to this CL before I read the final comment which makes it sounds like this bug is resolved. So, closing. Correct me if that's wrong.