Add examples; refactor HostRef

wasmtime-api/examples/hello.rs

@@ -0,0 +1,72 @@
+//! Translation of hello example
+
+use failure::{bail, format_err, Error};
+use std::cell::Ref;
+use std::fs::read;
+use std::rc::Rc;
+use wasmtime_api::*;
+
+struct HelloCallback;
+
+impl Callable for HelloCallback {
+    fn call(&self, _params: &[Val], _results: &mut [Val]) -> Result<(), HostRef<Trap>> {
+        println!("Calling back...");
+        println!("> Hello World!");
+        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/hello.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 hello_type = FuncType::new(Box::new([]), Box::new([]));
+    let hello_func = HostRef::new(Func::new(store.clone(), hello_type, Rc::new(HelloCallback)));
+
+    // Instantiate.
+    println!("Instantiating module...");
+    let imports = vec![hello_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...");
+    if let Err(_) = run_func.borrow().call(&[]) {
+        bail!("> Error calling function!");
+    }
+
+    // Shut down.
+    println!("Shutting down...");
+    drop(store);
+
+    // All done.
+    println!("Done.");
+    Ok(())
+}