# `wasmer` [![Build Status](https://github.com/wasmerio/wasmer/workflows/build/badge.svg?style=flat-square)](https://github.com/wasmerio/wasmer/actions?query=workflow%3Abuild) [![Join Wasmer Slack](https://img.shields.io/static/v1?label=Slack&message=join%20chat&color=brighgreen&style=flat-square)](https://slack.wasmer.io) [![MIT License](https://img.shields.io/github/license/wasmerio/wasmer.svg?style=flat-square)](https://github.com/wasmerio/wasmer/blob/master/LICENSE) [![crates.io](https://img.shields.io/crates/v/wasmer.svg)](https://crates.io/crates/wasmer)

[`Wasmer`](https://wasmer.io/) is the most popular
[WebAssembly](https://webassembly.org/) runtime for Rust (...and also
the fastest). It supports JIT (Just in Time) and AOT (Ahead of time)
compilation as well as pluggable compilers suited to your needs.

It's designed to be safe and secure, and runnable in any kind of environment.

## Usage

```rust
use wasmer::{Store, Module, Instance, Value, imports};

fn main() -> anyhow::Result<()> {
    let module_wat = r#"
    (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))
    "#;

    let store = Store::default();
    let module = Module::new(&store, &module_wat)?;
    // The module doesn't import anything, so we create an empty import object.
    let import_object = imports! {};
    let instance = Instance::new(&module, &import_object)?;

    let add_one = instance.exports.get_function("add_one")?;
    let result = add_one.call(&[Value::I32(42)])?;
    assert_eq!(result[0], Value::I32(43));

    Ok(())
}
```

## Features

Wasmer is not only fast, but also designed to be *highly customizable*:
* **Pluggable Engines**: do you have a fancy `dlopen` implementation? This is for you!
* **Pluggable Compilers**: you want to emit code with DynASM or other compiler? We got you!
* **Headless mode**: that means that no compilers will be required
  to run a `serialized` Module (via `Module::deserialize()`).
* **Cross-compilation**: You can pre-compile a module and serialize it
  to then run it in other platform (via `Module::serialize()`).

## Config flags

Wasmer has the following configuration flags:
* `wat` (enabled by default): It allows to read WebAssembly files in their text format.
  *This feature is normally used only in development environments*
* Compilers (mutually exclusive):
  - `singlepass`: it will use `wasmer-compiler-singlepass` as the default
     compiler (ideal for **blockchains**).
  - `cranelift`: it will use `wasmer-compiler-cranelift` as the default
     compiler (ideal for **development**).
  - `llvm`: it will use `wasmer-compiler-llvm` as the default
     compiler (ideal for **production**).

Wasmer ships by default with the `cranelift` compiler as its great for development proposes.
However, we strongly encourage to use the `llvm` backend in production as it performs
about 50% faster, achieving near-native speeds.

> Note: if you want to use multiple compilers at the same time, it's also possible!
> You will need to import them directly via each of the compiler crates.

---

Made with ❤️ by the Wasmer team, for the community