Method wrapExport

web/src/asyncify.ts:149–192

* Warp an exported asynctify function so it can return promise * * @param func The input function * @returns The wrapped async function

(func: (...args: Array<any>) => any)

   * @returns The wrapped async function
   */
  wrapExport(func: (...args: Array<any>) => any): (...args: Array<any>) => Promise<any> {
    return async (...args: Array<any>) => {
      assert(this.getState() == AsyncifyStateKind.None);

      // call the original function
      let result = func(...args);

      // JUMP-PT-UNWIND
      // after calling the function
      // the caller may hit a unwinding point depending on
      // the if (isPromise(value)) condition in wrapImport
      while (this.getState() == AsyncifyStateKind.Unwinding) {
        this.stopUnwind();
        // try to resolve the promise that the internal requested
        // we then store it into the temp value in storedValueBeforeRewind
        // which then get passed onto the function(see wrapImport)
        // that can return the value
        const storedPromiseBeforeUnwind = this.storedPromiseBeforeUnwind;
        this.storedPromiseBeforeUnwind = null;
        assert(this.storedExceptionBeforeRewind === null);
        assert(this.storedValueBeforeRewind == null);

        try {
          this.storedValueBeforeRewind = await storedPromiseBeforeUnwind;
        } catch (error) {
          // the store exception
          this.storedExceptionBeforeRewind = error;
        }
        assert(!isPromise(this.storedValueBeforeRewind));
        // because we called asynctify_stop_unwind,the state is now none
        assert(this.getState() == AsyncifyStateKind.None);

        // re-enter the function, jump to JUMP-PT-REWIND in wrapImport
        // the value will be passed to that point via storedValueBeforeRewind
        //
        // NOTE: we guarantee that if exception is throw the asynctify state
        // will already be at None, this is because we will goto JUMP-PT-REWIND
        // which will call aynctify_stop_rewind
        this.startRewind();
        result = func(...args);
      }
      return result;
    };
  }

  private startRewind() : void {
    if (this.exports.asyncify_start_rewind === undefined) {