# Wasmer Runtime Wasmer is a standalone JIT WebAssembly runtime, aiming to be fully compatible with Emscripten, Rust and Go. [Learn more](https://github.com/wasmerio/wasmer). This crate represents the high-level runtime API, making 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`][func.call] to call an exported function safely. [`instantiate`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/fn.instantiate.html [`Instance`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Instance.html [`call`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Instance.html#method.call [`func`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Instance.html#method.func [func.call]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/struct.Function.html#method.call ## Example Given this WebAssembly: ```wat (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: ```rust 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, DynFunc, Value, imports, error, }; fn main() -> error::Result<()> { // We're not importing anything, so make an empty import object. let import_object = imports! {}; let instance = instantiate(WASM, &import_object)?; let values = instance .exports .get::("add_one")? .call(&[Value::I32(42)])?; assert_eq!(values[0], Value::I32(43)); Ok(()) } ``` ## Additional Notes The `wasmer-runtime` crate is built to support multiple compiler backends. We support having a [Cranelift] backend in the [`wasmer-clif-backend`] crate, a [LLVM] backend in the [`wasmer-llvm-backend`] crate, and the [Singlepass] backend in the [`wasmer-singlepass-backend`] crate. Currently, the Cranelift backend is the default. You can specify the compiler you wish to use with the [`compile_with`] function. [Cranelift]: https://github.com/CraneStation/cranelift [LLVM]: https://llvm.org [Singlepass]: https://github.com/wasmerio/wasmer/tree/master/lib/singlepass-backend [`wasmer-clif-backend`]: https://crates.io/crates/wasmer-clif-backend [`compile_with`]: https://docs.rs/wasmer-runtime/*/wasmer_runtime/fn.compile_with.html