wasm-learning

The functions example

In this example, we demonstrate how to call Rust functions in SSVM from JavaScript. Read about Getting started with Rust functions in Node.js.

Prerequisites

If you have not done so already, follow these simple instructions to install Rust, Node.js, SSVM, and ssvmup.

Create new project

$ cargo new --lib functions
$ cd functions

Change the cargo config file

The Cargo.toml file shows the dependencies. Note the dependency for wasm-bindgen, which is required for invoking these Rust functions from JavaScript. The dependency for serde and serde-json allows us to work with JSON strings to represent complex data types.

Write Rust code

The supported data types are:

• Call parameters can be any combo of i32, String, &str, Vec, and &[u8]
• Return value can be i32 or String or Vec
• For complex data types, such as structs, you could return a JSON string

The src/lib.rs file contains a few Rust functions that showcase different combinations of input / output parameters, including using JSON strings to serialize and deserialize complex data types.

Build the WASM bytecode

$ ssvmup build --enable-aot

Node.js app

The node/app.js file shows how to call the Rust functions, running inside the Second State VM (SSVM), from JavaScript inside Node.js.

Test

node app.js

Result

hello SSVM
...
246
Uint8Array [87, ... 203]
Uint8Array [126, ... 27]