Load a wasm module in rust

super-horst · December 24, 2021, 9:30pm

Merry Christmas to y'all

TL,DR: How to get a wasm instance inside wasm?

I'm trying to load a wasm 'plugin' inside another wasm module, both written in rust. To that end, I created a small PoC project with the 'main' wasm app, a 'plugin' wasm app and a simple webserver.

Fortunately the js_sys crate provides me with a tool to fetch and parse wasm binary code. However I cannot access the module or the instance generated by this call. Via the log, I can see, the return type is a JsValue containing an object which matches the specification. I already tried to use serde, but Module and Instance from the js_sys crate are not Deserializable.

It seems, that the behaviour can be accomplished by using a JS wrapper, but I'd like to create a solution entirely in rust.

Please see the code below:

github.com

super-horst/wasm-plugin-poc/blob/main/webapp/src/lib.rs#L35


      
                  let wasm_instance: WebAssembly::Instance = Reflect::get(&wasm_result, &"instance".into()).unwrap().dyn_into().unwrap();
          
          
        let wasm_exports = wasm_instance.exports();
          
          
        let add = Reflect::get(wasm_exports.as_ref(), &"__wbindgen_start".into())
                      .unwrap()
                      .dyn_into::<Function>()
                      .expect("wasm-bindgen start wasn't a function");
          
          
        add.call0(&JsValue::undefined()).unwrap();
                  info!("Completed load of 'plugin'")
              });
          }
          
          
fn set_panic_hook() {
              // When the `console_error_panic_hook` feature is enabled, we can call the
              // `set_panic_hook` function to get better error messages if we ever panic.
              console_error_panic_hook::set_once();
          }

super-horst · December 25, 2021, 9:47pm

Turns out wasm-bindgen provides quite elaborate examples, if you know what to look for
https://rustwasm.github.io/wasm-bindgen/examples/wasm-in-wasm.html

system · March 25, 2022, 9:47pm

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Load a wasm module in rust

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