feat: add example multi value

__wasm/wasmtime/examples/multi_value.rs

@@ -0,0 +1,79 @@
+use anyhow::Result;
+
+//https://docs.wasmtime.dev/examples-rust-multi-value.html
+fn main() -> Result<()> {
+    use wasmtime::*;
+
+    println!("Initializing...");
+    let engine = Engine::default();
+    let mut store = Store::new(&engine, ());
+
+    // Compile.
+    println!("Compiling module...");
+    let module = Module::new(&engine, r#"
+    (module
+      (func $f (import "" "f") (param i32 i64) (result i64 i32))
+
+      (func $g (export "g") (param i32 i64) (result i64 i32)
+        (call $f (local.get 0) (local.get 1))
+      )
+
+      (func $round_trip_many
+        (export "round_trip_many")
+        (param i64 i64 i64 i64 i64 i64 i64 i64 i64 i64)
+        (result i64 i64 i64 i64 i64 i64 i64 i64 i64 i64)
+
+        local.get 0
+        local.get 1
+        local.get 2
+        local.get 3
+        local.get 4
+        local.get 5
+        local.get 6
+        local.get 7
+        local.get 8
+        local.get 9)
+    )
+    "#)?;
+
+    // Create a host function which takes multiple parameters and returns
+    // multiple results.
+    println!("Creating callback...");
+    let callback_func = Func::wrap(&mut store, |a: i32, b: i64| -> (i64, i32) {
+        (b + 1, a + 1)
+    });
+
+    // Instantiate.
+    println!("Instantiating module...");
+    let instance = Instance::new(&mut store, &module, &[callback_func.into()])?;
+
+    // Extract exports.
+    println!("Extracting export...");
+    let g = instance.get_typed_func::<(i32, i64), (i64, i32)>(&mut store, "g")?;
+
+    // Call `$g`.
+    println!("Calling export \"g\"...");
+    let (a, b) = g.call(&mut store, (1, 3))?;
+
+    println!("Printing result...");
+    println!("> {} {}", a, b);
+
+    assert_eq!(a, 4);
+    assert_eq!(b, 2);
+
+    // Call `$round_trip_many`.
+    println!("Calling export \"round_trip_many\"...");
+    let round_trip_many = instance
+        .get_typed_func::<
+            (i64, i64, i64, i64, i64, i64, i64, i64, i64, i64),
+            (i64, i64, i64, i64, i64, i64, i64, i64, i64, i64),
+        >
+        (&mut store, "round_trip_many")?;
+    let results = round_trip_many.call(&mut store, (0, 1, 2, 3, 4, 5, 6, 7, 8, 9))?;
+
+    println!("Printing result...");
+    println!("> {:?}", results);
+    assert_eq!(results, (0, 1, 2, 3, 4, 5, 6, 7, 8, 9));
+
+    Ok(())
+}