README.md

The functions example

In this example, we demonstrate how to call Rust functions in SSVM from JavaScript.

Set up

$ sudo apt-get update
$ sudo apt-get -y upgrade
$ sudo apt install build-essential curl wget git vim libboost-all-dev

$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
$ source $HOME/.cargo/env

$ curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
$ [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
$ [ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion"

$ nvm install v10.19.0
$ nvm use v10.19.0

$ npm install -g ssvmup # Append --unsafe-perm if permission denied
$ npm install ssvm

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 --nowasi

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]