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AssemblyScript WASM - Add Numbers

This example package demonstrates compiling a simple AssemblyScript program, add.ts which adds two numbers to WASM, executing it in a host environment, and accessing it's methods.

This package additionally demonstrates running WASM using both the AssemblyScript loader, which provides convenience functionality and compatibility, and native WebAssembly framework.

Project Structure

Dependencies

  • NodeJS & NPM is required to build the project dependencies, run the WASM compile, and run tests. NPM comes installed with NodeJS by default

Before running the project, you must also install the project's dependencies. From the project root, run:

npm install

Directories & files

  • src/ - Contains the AssemblyScript (.ts) source code to be compiled into the WASM module, for example add.ts
  • build/ - Contains the compiled output WASM file resulting from the build process
  • test/ - Contains NodeJS test code demonstrating and unit testing the functionality contained in and exposed by the compiled WASM module in build
  • package.json - Contains the dependency declarations and NPM build & test scripts. Controls WASM & AssemblyScript compiler options

Development Workflow

  1. Write AssemblyScript code with exported functions
  2. Compile the AssemblyScript code to WASM
  3. Modify tests in test/ to test functions exported from AssemblyScript code
  4. Run tests
  5. Repeat!

Compiling AssemblyScript to WASM

To compile the add.ts code to a WASM binary:

npm run build

A add.wasm file will be produced in the build directory

Testing

Test the module outside of the context of the blockchain:

npm test

Module Usage Example

How to access and use AssemblyScript WASM modules from NodeJS, from test/add.unit.spec.js:

const util = require('../../../../src/util');

const imports = util.getDefaultImports();

const buffer = fs.readFileSync(path.resolve(__dirname, '../build/add.wasm'));
module = await loader.instantiateBuffer(buffer, imports);

//use module.<function name> to access functions!
console.log(module.add(3, 99)); // => 102

API

add(i32 x, i32 y) - i32

Add two integers together and return the resulting sum

addRunning(i32 x) - i32

Add an integer to a running total and return the resulting running total