AssemblyScript - asyncify example - using the JS for asyncify_ functions . Compile passing ` --runPasses asyncify` to the assembly-script asc command

index.ts

import fs from 'fs';
const wasmBuffer = fs.readFileSync('./build/release.wasm');

interface WasmExports {
  asyncStackPtr: number;
  initAsyncStack(): void;
  asyncify_start_unwind(stackPtr: number): void;
  asyncify_start_rewind(stackPtr: number): void;
  asyncify_stop_rewind(): void;
  run(): void;
}

class AsyncDelay {
  private trigger_rewind = false;
  constructor(private wasmExports: WasmExports) {}

  public async_method: (() => Promise<void>) | null = null;

  trigger() {
    const exports = this.wasmExports;
    if(!this.trigger_rewind) {
      exports.asyncify_start_unwind(exports.asyncStackPtr);
      this.trigger_rewind = true;
      this.async_method!().then(() => {
        exports.asyncify_start_rewind(exports.asyncStackPtr);
        exports.run();
      })
    } else {
      exports.asyncify_stop_rewind();
      this.trigger_rewind = false;
    }
  }
}

let delay!: AsyncDelay;

WebAssembly.instantiate(wasmBuffer, {
  env: {
      abort: console.error,
      sleep: function () { return delay.trigger(); },
      log: function(p) { console.log(p) }
  }
  }).then(wasmModule => {

  delay = new AsyncDelay(wasmModule.instance.exports as any);
  const { run, initAsyncStack } = wasmModule.instance.exports as any as WasmExports;
  
  initAsyncStack();
  delay.async_method = () => new Promise(resolve => setTimeout(resolve, 2000));
  run();
});

sample_async_as.ts

@external("env", "log")
declare function print(num: i32): void;
@external("env", "sleep")
declare function sleep(): i32;

@unmanaged
class StackDescriptor {
  public stackStart: usize;
  public stackEnd: usize
  constructor(){
    this.stackStart = heap.alloc(1024);
    this.stackEnd = this.stackStart + 1024;
  }
}

@global
export let asyncStackPtr: usize = 0;
export function initAsyncStack(): void {
  const stack = new StackDescriptor();
  asyncStackPtr = changetype<usize>(stack);
}

export function run(): void {
  print(10);
  sleep();
  print(20);
}