Utilities for loading and running WASM modules from Dart code

Provides utilities for loading and running WASM modules

Built on top of the Wasmer runtime.

Setup

Start by installing the tools needed to build the Wasmer runtime:

• Install the Rust SDK.
• On Windows, to get link.exe, install the Visual Studio build tools with the “Desktop development with C++”-option selected.

Basic Usage

As a simple example, we’ll try to call a simple C function from Dart using package:wasm. For a more detailed example that uses WASI, check out the example directory.

1. First create new Dart app folder: dart create wasmtest
2. Add a dependency to package wasm in pubspec.yaml and run dart pub get
3. Next run dart run wasm:setup to build the Wasmer runtime. This will take a few minutes.
4. Then add a new file square.cc with the following contents:extern “C” int square(int n) { return n * n; }
5. We can compile this C++ code to WASM using a recent version of the clang compiler:clang –target=wasm32 -nostdlib “-Wl,–export-all” “-Wl,–no-entry” -o square.wasm square.cc
6. Replace the contents of your Dart program (bin/wasmtest.dart) with:
   

import ‘dart:io’;
import ‘package:wasm/wasm.dart’;

void main() {
final data = File(‘square.wasm’).readAsBytesSync();
final mod = WasmModule(data);
print(mod.describe());
final inst = mod.builder().build();
final square = inst.lookupFunction(‘square’);
print(square(12));
}

7. Run the Dart program: dart run. This should print:

export memory: memory
export function: int32 square(int32)

144

Download WASM source code on GitHub

https://github.com/dart-lang/wasm