wasm_ffi 2.3.0

A wrapper for wasm which can be used as a drop-in replacement for dart:ffi for Web platform.

example/README.md

wasm_ffi Example

This directory contains a complete example of using wasm_ffi to port the opus_dart library to the web.

It demonstrates:

• Compiling a C library (libopus) to WebAssembly using Emscripten.
• Using ffigen with a proxy file to generate bindings.
• Setting up the necessary boilerplate to initialize wasm_ffi in a vanilla Dart web app.

Project Structure

• bin/: Contains the main entry point for the vanilla Dart app.
• lib/src/: Contains the specific binding code (generated.dart), the proxy (proxy_ffi.dart), and initialization logic.
• web/: Contains the HTML and build artifacts for the web.

Building the C Library

We use Docker to ensure a consistent build environment for the libopus library.

1. Build the Docker image: The generic Dockerfile is available in the root of the example.

2. Compile to WASM: Detailed instructions and the Makefile are in the Makefile (if present) or described in the original tutorial. > Note: The pre-compiled libopus.js and libopus.wasm are already included in the web/ directory for convenience.

   To rebuild them yourself using the Docker method from the original tutorial:

   docker build -t wasm_ffi_opus_builder .
   docker run --rm -v $(pwd):/src wasm_ffi_opus_builder
   

   (Adjust the commands based on the actual Dockerfile logic if you want to reproduce the build exactly).

Running the Example

1. Compile Dart to JavaScript: We use dart2js to compile the Dart application code.

   dart compile js ./bin/main.dart -o ./web/main.dart.js
   

2. Serve the Web Application: You need a simple HTTP server to serve the web directory. We recommend dhttpd.

   Install dhttpd if you haven't:

   dart pub global activate dhttpd
   

   Run the server:

   cd web
   dart pub global run dhttpd -p 8080
   

3. Open in Browser: Navigate to http://localhost:8080 in your browser. Open the Developer Console (F12) to see the output. You should see the Opus version string printed (e.g., libopus 1.3.1).

Learn More

For a detailed explanation of the concepts used here, including how proxy_ffi.dart works and how to support both Native and Web platforms, please refer to the main wasm_ffi README.