|0.2.0||May 27, 2022|
|0.1.4||Nov 8, 2020|
|0.1.3||Oct 5, 2020|
#148 in WebAssembly
16,046 downloads per month
Used in 23 crates (2 directly)
std::thread replacement for wasm32 target.
This crate tries to closely replicate
std::thread API. Namely, it doesn't require you to bundle worker scripts and resolves wasm-bindgen shim URL automatically.
Note that some API is still missing and may be even impossible to implement given wasm limitations.
Using as a library
- This project supports
no-modules. If building for
web, enable the crate feature
es_modules. Otherwise, this package will target
use wasm_thread as thread. Note that some API might be missing.
- Build normally using
wasm-packor adapt build_wasm.sh to your project.
Notes on wasm limitations
- In order for multiple wasm instances to share the same memory,
SharedArrayBufferis required. This means that the COOP and COEP security headers for the webpage will need to be set (see Mozilla's documentation). These may be enabled by adjusting webserver settings or using a service worker.
- Any blocking API (
futures::block_on(), etc) on the main thread will freeze the browser for as long as lock is maintained. This also freezes any proxied functions, which means that worker spawning, network fetches and other similar asynchronous APIs will block also and can cause a deadlock. To avoid this, either run your
main()in a worker thread or use async futures.
- Atomic locks (
i32.atomic.waitto be specific) will panic on the main thread. This means that
mutex.lock()will likely crash. Solution is the same as above.
- Web workers are normally spawned by providing a script URL, however, to avoid bundling scripts this library uses URL encoded blob web_worker.js to avoid HTTP fetch.
.jsshim script is still needed and a hack is used to obtain its URL. If this for some reason does not work in your setup, please report an issue or use
Builder::wasm_bindgen_shim_url()to specify explicit URL.
- For additional information on wasm threading look at this blogpost or raytrace-parallel example.
For a higher-level threading solution, see wasm-bindgen-rayon, which allows one to utilize a fixed-size threadpool in web browsers.
cargo run --example simple
- Build with
./build_wasm.ps1(PowerShell). This custom build step is required because prebuilt standard library does not have support for atomics yet. Read more about this here.
examplesdirectory over HTTP with cross-origin isolation enabled and open
simple.htmlin the browser. Inspect console output. You can use
cargo install sfzas a basic HTTP server and serve with
sfz examples --coi.
- Build with
./examples-wasm-pack/web-build.shfor an example targeting
./examples/wasm-pack/web-build-no-module.shfor an example targeting
./examples-wasm-pack/no-module, respectively, over HTTP and open
simple.htmlin browser. Inspect console output.
hi number 1 from the spawned thread ThreadId(2)! hi number 1 from the main thread ThreadId(1)! hi number 1 from the spawned thread ThreadId(3)! hi number 2 from the main thread ThreadId(1)! hi number 2 from the spawned thread ThreadId(2)! hi number 2 from the spawned thread ThreadId(3)!
hi number 1 from the main thread ThreadId(1)! hi number 2 from the main thread ThreadId(1)! hi number 1 from the spawned thread ThreadId(2)! hi number 1 from the spawned thread ThreadId(3)! hi number 2 from the spawned thread ThreadId(2)! hi number 2 from the spawned thread ThreadId(3)!
As you can see wasm threads are only spawned after
main() returns, because browser event loop cannot continue while main thread is blocked.
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.