wasmer/lib/runtime

Wasmer-Runtime

Wasmer-runtime is a library that makes embedding WebAssembly in your application easy, efficient, and safe.

How to use Wasmer-Runtime

The easiest way is to use the instantiate function to create an Instance. Then you can use call or func and then call to call an exported function safely.

Here's an example:

Given this WebAssembly:

(module
  (type $t0 (func (param i32) (result i32)))
  (func $add_one (export "add_one") (type $t0) (param $p0 i32) (result i32)
    get_local $p0
    i32.const 1
    i32.add))

compiled into wasm bytecode, we can call the exported "add_one" function:

static WASM: &'static [u8] = &[
    // The module above compiled to bytecode goes here.
    0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x06, 0x01, 0x60,
    0x01, 0x7f, 0x01, 0x7f, 0x03, 0x02, 0x01, 0x00, 0x07, 0x0b, 0x01, 0x07,
    0x61, 0x64, 0x64, 0x5f, 0x6f, 0x6e, 0x65, 0x00, 0x00, 0x0a, 0x09, 0x01,
    0x07, 0x00, 0x20, 0x00, 0x41, 0x01, 0x6a, 0x0b, 0x00, 0x1a, 0x04, 0x6e,
    0x61, 0x6d, 0x65, 0x01, 0x0a, 0x01, 0x00, 0x07, 0x61, 0x64, 0x64, 0x5f,
    0x6f, 0x6e, 0x65, 0x02, 0x07, 0x01, 0x00, 0x01, 0x00, 0x02, 0x70, 0x30,
];

use wasmer_runtime::{
    instantiate,
    Value,
    imports,
    error,
};

fn main() -> error::Result<()> {
    // We're not importing anything, so make an empty import object.
    let import_object = imports! {};

    let mut instance = instantiate(WASM, &import_object)?;

    let values = instance
        .func("add_one")?
        .call(&[Value::I32(42)])?;

    assert_eq!(values[0], Value::I32(43));
    
    Ok(())
}

Additional Notes:

The wasmer-runtime is build to support compiler multiple backends. Currently, we support the Cranelift compiler with the wasmer-clif-backend crate.

You can specify the compiler you wish to use with the compile_with function.