wasmtime / PR #175 Add `wasmtime-hostmodule` DSL crate · git-wasmtime

This adds a crate defining a DSL for creating host modules. I debated whether to include this in wasmtime proper or whether to define an external crate, but I could definitely imagine that most people using wasmtime will want something like this in order to define host functions etc. I haven't added any code that reexports this from the wasmtime root crate but I could imagine that that would be helpful (plus, it would mean we can remove the workspace glob that I added in 1a59141).

use wasmtime_hostmodule::{
    exports,
    BindArgType,
    Func,
    Global,
    Instantiate,
    Memory,
    Table,
    TableElementType
};

fn hello_world() {
    println!("Hello, world!");
}

fn print_and_return(val: i32) -> i32 {
    println!("{}", val);
    val
}

let mut counter = 100;
let my_closure = move |inc: u32| -> u32 {
    counter += inc;
    counter
};

let my_module = exports! {
    do_thing: Func(hello_world.bind::<()>()),
    print_and_return: Func(print_and_return.bind::<(i32,)>()),
    counting_func: Func(my_closure.bind::<(u32,)>()),
    my_glob: Global(100u64, Default::default()),
    memory: Memory {
        minimum: 1,
        maximum: Some(2),
        shared: false,
    },
    table: Table {
        ty: TableElementType::Func,
        minimum: 10,
        maximum: Some(20),
    },
};

my_module.instantiate().unwrap();

Run cargo doc from the crate root for more info. This isn't a proc macro, the macro does almost nothing at all. All the magic is done in the type system, as God intended.

Stream: git-wasmtime

Topic: wasmtime / PR #175 Add `wasmtime-hostmodule` DSL crate

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