wasmtime-ex

💧Elixir WebAssembly runtime powered by Wasmtime 🦀

Docs

Installation

You can add wasmtime to your list of dependencies in mix.exs:

def deps do
  [
    {:wasmtime, "~> 0.3.0"}
  ]
end

Usage

In this example, the Wasm module is compiled, instantiated and a host function is called and imported from Elixir:

mod = ~S/
    (module
      (import "" "" (func $compute (param i32) (result i32)))
      (func (export "run") (param i32) (result i32) (call $compute (local.get 0)))
    )
    /

{:ok, pid} =
  Wasmtime.load(%Wasmtime.FromBytes{
    bytes: mod,
    func_imports: [
      {fn x ->
         "Hello from Elixir! Got #{x}. Returning an i32 value" |> IO.inspect()
         20 + x
       end, [:i32], [:i32]}
    ]
  })

{:ok, [200]} = Wasmtime.call_func(pid, "run", [180])

This next example loads a Wasm module from this rust lib.rs file that's been built with wasm-pack:

{:ok, pid} = Wasmtime.load(%Wasmtime.FromFile{file_path: "test/data/wasmapp/wasmapp_bg.wasm"})
{:ok, {[:i32, :i32], [:i32]}} = Wasmtime.get_func(pid, "add")
{:ok, {[:i32], [:i32]}} = Wasmtime.get_func(pid, "plus_10")
{:ok, {[:i32, :i32], [:i32]}} = Wasmtime.get_func(pid, "min")

{:ok, [20]} = Wasmtime.call_func(pid, "add", [11, 9])
{:ok, [30]} = Wasmtime.call_func(pid, "plus_10", [20])
{:ok, [-10]} = Wasmtime.call_func(pid, "min", [-10, 3])

If you want to see more usage examples, check this test file out.

Supported Wasm types

• Functions are supported with the four value types i32, i64, f32 and f64
• Memory will be supported soon
• Globals and Tables will be considered in the future

Benchmark

Wasmtime is fast. Here's a benchmark with these simple functions, running on my computer, for a reference:

Compiling NIF crate :wasmtime_ex (native/wasmtime_ex)...
    Finished release [optimized] target(s) in 0.07s
Operating System: Linux
CPU Information: Intel(R) Core(TM) i7-4720HQ CPU @ 2.60GHz
Number of Available Cores: 8
Available memory: 31.25 GB
Elixir 1.11.0
Erlang 23.1.1

Benchmark suite executing with the following configuration:
warmup: 20 s
time: 1 min
memory time: 0 ns
parallel: 1
inputs: none specified
Estimated total run time: 6.67 min

Name                 ips        average  deviation         median         99th %
add_xt          140.22 K        7.13 μs   ±461.08%        6.94 μs       11.20 μs
plus_10_xt      134.72 K        7.42 μs   ±443.67%        7.21 μs       11.29 μs
add              21.75 K       45.98 μs    ±52.83%       42.90 μs       83.64 μs
plus_10          19.78 K       50.55 μs    ±47.20%       46.26 μs       91.51 μs
imports           4.28 K      233.76 μs    ±20.80%      230.13 μs      332.01 μs