1 //! This is an example of working with multi-value modules and dealing with
2 //! multi-value functions.
3 //!
4 //! Note that the `Func::wrap*` interfaces cannot be used to return multiple
5 //! values just yet, so we need to use the more dynamic `Func::new` and
6 //! `Func::call` methods.
7
8 // You can execute this example with `cargo run --example multi`
9
10 use wasmtime::Result;
11
main() -> Result<()>12 fn main() -> Result<()> {
13 use wasmtime::*;
14
15 println!("Initializing...");
16 let engine = Engine::default();
17 let mut store = Store::new(&engine, ());
18
19 // Compile.
20 println!("Compiling module...");
21 let module = Module::from_file(&engine, "examples/multi.wat")?;
22
23 // Create a host function which takes multiple parameters and returns
24 // multiple results.
25 println!("Creating callback...");
26 let callback_func = Func::wrap(&mut store, |a: i32, b: i64| -> (i64, i32) {
27 (b + 1, a + 1)
28 });
29
30 // Instantiate.
31 println!("Instantiating module...");
32 let instance = Instance::new(&mut store, &module, &[callback_func.into()])?;
33
34 // Extract exports.
35 println!("Extracting export...");
36 let g = instance.get_typed_func::<(i32, i64), (i64, i32)>(&mut store, "g")?;
37
38 // Call `$g`.
39 println!("Calling export \"g\"...");
40 let (a, b) = g.call(&mut store, (1, 3))?;
41
42 println!("Printing result...");
43 println!("> {a} {b}");
44
45 assert_eq!(a, 4);
46 assert_eq!(b, 2);
47
48 // Call `$round_trip_many`.
49 println!("Calling export \"round_trip_many\"...");
50 let round_trip_many = instance
51 .get_typed_func::<
52 (i64, i64, i64, i64, i64, i64, i64, i64, i64, i64),
53 (i64, i64, i64, i64, i64, i64, i64, i64, i64, i64),
54 >
55 (&mut store, "round_trip_many")?;
56 let results = round_trip_many.call(&mut store, (0, 1, 2, 3, 4, 5, 6, 7, 8, 9))?;
57
58 println!("Printing result...");
59 println!("> {results:?}");
60 assert_eq!(results, (0, 1, 2, 3, 4, 5, 6, 7, 8, 9));
61
62 Ok(())
63 }
64