While it doesn't happen right now in this particular example, `lastPtr` can be potentially overridden several times before the module is fully initialised.
Rather than having a boolean and a storage for one last argument, `await` a promise returned from `wasm_bindgen` itself in the new `onmessage` handler before executing actual command.
This way all the potential tasks will queue up naturally, wait for the initialisation, and then execute in a correct order.
One of the best parts about concurrency in Rust is using `rayon` and how
easy it makes parallelization of tasks, so it's the ideal example for
parallel Rust on the web! Previously we've been unable to use `rayon`
because there wasn't a way to customize how rayon threads themselves are
spawned, but [that's now being developed for us][rayon]!
This commit uses that PR to rewrite the `raytrace-parallel` example in
this repository. While not a perfect idiomatic representation of using
`rayon` I think this is far more idiomatic than the previous iteration
of `raytrace-parallel`! I'm hoping that we can continue to iterate on
this, but otherwise show it off as a good example of parallel Rust on
the web.
[rayon]: https://github.com/rayon-rs/rayon/pull/636
... and add a parallel raytracing demo!
This commit adds enough support to `wasm-bindgen` to produce a workable
wasm binary *today* with the experimental WebAssembly threads support
implemented in Firefox Nightly. I've tried to comment what's going on in
the commits and such, but at a high level the changes made here are:
* A new transformation, living in a new `wasm-bindgen-threads-xform`
crate, prepares a wasm module for parallel execution. This performs a
number of mundane tasks which I hope to detail in a blog post later on.
* The `--no-modules` output is enhanced with more support for when
shared memory is enabled, allowing passing in the module/memory to
initialize the wasm instance on multiple threads (sharing both module
and memory).
* The `wasm-bindgen` crate now offers the ability, in `--no-modules`
mode, to get a handle on the `WebAssembly.Module` instance.
* The example itself requires Xargo to recompile the standard library
with atomics and an experimental feature enabled. Afterwards it
experimentally also enables threading support in wasm-bindgen.
I've also added hopefully enough CI support to compile this example in a
builder so we can upload it and poke around live online. I hope to
detail more about the technical details here in a blog post soon as
well!
