WebAssembly Text Format (*.wat
)
While not necessarily a full-blown language you might be curious how Wasmtime
interacts with the *.wat
text format! The wasmtime
CLI and Rust
embedding API both support the *.wat
text format by default.
"Hello, World!" is pretty nontrivial in the *.wat
format since it's
assembly-like and not really intended to be a primary programming language. That
being said we can create a simple add function to call it!
For example if you have a file add.wat
like so:
(module
(func (export "add") (param i32 i32) (result i32)
local.get 0
local.get 1
i32.add))
Then you can execute this on the CLI with:
$ wasmtime add.wat --invoke add 1 2
warning: ...
warning: ...
3
And we can see that we're already adding numbers!
You can also see how this works in the Rust API like so:
extern crate wasmtime; extern crate anyhow; use wasmtime::*; fn main() -> anyhow::Result<()> { let mut store = Store::<()>::default(); let wat = r#" (module (func (export "add") (param i32 i32) (result i32) local.get 0 local.get 1 i32.add)) "#; let module = Module::new(store.engine(), wat)?; let instance = Instance::new(&mut store, &module, &[])?; let add = instance.get_typed_func::<(i32, i32), i32>(&mut store, "add")?; println!("1 + 2 = {}", add.call(&mut store, (1, 2))?); Ok(()) }