[wasmtime-api] Multi value api support (#448)

wasmtime-api/examples/multi.rs

@@ -0,0 +1,89 @@
+//! Translation of multi example
+
+extern crate alloc;
+
+use alloc::rc::Rc;
+use core::cell::Ref;
+use failure::{bail, format_err, Error};
+use std::fs::read;
+use wasmtime_api::*;
+
+struct Callback;
+
+impl Callable for Callback {
+    fn call(&self, args: &[Val], results: &mut [Val]) -> Result<(), HostRef<Trap>> {
+        println!("Calling back...");
+        println!("> {} {}", args[0].i32(), args[1].i64());
+
+        results[0] = Val::I64(args[1].i64() + 1);
+        results[1] = Val::I32(args[0].i32() + 1);
+        Ok(())
+    }
+}
+
+fn main() -> Result<(), Error> {
+    // Initialize.
+    println!("Initializing...");
+    let engine = HostRef::new(Engine::new(Config::default()));
+    let store = HostRef::new(Store::new(engine));
+
+    // Load binary.
+    println!("Loading binary...");
+    let binary = read("examples/multi.wasm")?;
+
+    // Compile.
+    println!("Compiling module...");
+    let module = HostRef::new(
+        Module::new(store.clone(), &binary)
+            .map_err(|_| format_err!("> Error compiling module!"))?,
+    );
+
+    // Create external print functions.
+    println!("Creating callback...");
+    let callback_type = FuncType::new(
+        Box::new([ValType::I32, ValType::I64]),
+        Box::new([ValType::I64, ValType::I32]),
+    );
+    let callback_func = HostRef::new(Func::new(store.clone(), callback_type, Rc::new(Callback)));
+
+    // Instantiate.
+    println!("Instantiating module...");
+    let imports = vec![callback_func.into()];
+    let instance = HostRef::new(
+        Instance::new(store.clone(), module, imports.as_slice())
+            .map_err(|_| format_err!("> Error instantiating module!"))?,
+    );
+
+    // Extract export.
+    println!("Extracting export...");
+    let exports = Ref::map(instance.borrow(), |instance| instance.exports());
+    if exports.len() == 0 {
+        bail!("> Error accessing exports!");
+    }
+    let run_func = exports[0]
+        .func()
+        .ok_or_else(|| format_err!("> Error accessing exports!"))?;
+
+    // Call.
+    println!("Calling export...");
+    let args = vec![Val::I32(1), Val::I64(3)];
+    let results = run_func.borrow().call(&args);
+    if let Err(_) = results {
+        bail!("> Error calling function!");
+    }
+
+    let results = results.unwrap();
+    println!("Printing result...");
+    println!("> {} {}", results[0].i64(), results[1].i32());
+
+    debug_assert!(results[0].i64() == 4);
+    debug_assert!(results[1].i32() == 2);
+
+    // Shut down.
+    println!("Shutting down...");
+    drop(store);
+
+    // All done.
+    println!("Done.");
+    Ok(())
+}