feat: update examples

__wasm/wasmtime/examples/example1.rs

@@ -28,7 +28,7 @@ fn main() -> Result<()> {
     // this case we're using `4` for.
     let mut store = Store::new(&engine, 4);
     let instance = linker.instantiate(&mut store, &module)?;
-    let hello = instance.get_typed_func::<(), (), _>(&mut store, "hello")?;
+    let hello = instance.get_typed_func::<(), ()>(&mut store, "hello")?;
 
     // And finally we can call the wasm!
     hello.call(&mut store, ())?;

__wasm/wasmtime/examples/example2.rs

@@ -38,11 +38,11 @@ fn main() -> Result<()> {
     // println!("memory size: {}", memory.size(&store));
 
     let msg = "hatter".as_bytes();
-    let malloc_fn = instance.get_typed_func::<i32, i32, _>(&mut store, "__wbindgen_malloc")?;
+    let malloc_fn = instance.get_typed_func::<i32, i32>(&mut store, "__wbindgen_malloc")?;
     let msg_ptr = malloc_fn.call(&mut store, msg.len() as i32)?;
     memory.write(&mut store, msg_ptr as usize, msg)?;
 
-    let greet_fn = instance.get_typed_func::<(i32, i32), (), _>(&mut store, "greet")?;
+    let greet_fn = instance.get_typed_func::<(i32, i32), ()>(&mut store, "greet")?;
     greet_fn.call(&mut store, (msg_ptr, msg.len() as i32))?;
 
     Ok(())

__wasm/wasmtime/examples/example3.rs

@@ -1,37 +1,63 @@
 use anyhow::Result;
 use wasmtime::*;
 
+struct MyState {
+    name: String,
+    count: usize,
+}
+
 fn main() -> Result<()> {
-    // Modules can be compiled through either the text or binary format
+    // First the wasm module needs to be compiled. This is done with a global
+    // "compilation environment" within an `Engine`. Note that engines can be
+    // further configured through `Config` if desired instead of using the
+    // default like this is here.
+    println!("Compiling module...");
     let engine = Engine::default();
-    let wat = r#"
+    let module = Module::new(&engine, r#"
     (module
-            (import "host" "hello" (func $host_hello (param i32)))
+        (func $hello (import "" "hello"))
+        (func (export "run") (call $hello))
+    )"#).unwrap();
 
-            (func (export "hello")
-                i32.const 3
-                call $host_hello)
-        )
-    "#;
-    let module = Module::new(&engine, wat)?;
+    // After a module is compiled we create a `Store` which will contain
+    // instantiated modules and other items like host functions. A Store
+    // contains an arbitrary piece of host information, and we use `MyState`
+    // here.
+    println!("Initializing...");
+    let mut store = Store::new(
+        &engine,
+        MyState {
+            name: "hello, world!".to_string(),
+            count: 0,
+        },
+    );
 
-    // Create a `Linker` which will be later used to instantiate this module.
-    // Host functionality is defined by name within the `Linker`.
-    let mut linker = Linker::new(&engine);
-    linker.func_wrap("host", "hello", |caller: Caller<'_, u32>, param: i32| {
-        println!("Got {} from WebAssembly", param);
-        println!("my host state is: {}", caller.data());
-    })?;
+    // Our wasm module we'll be instantiating requires one imported function.
+    // the function takes no parameters and returns no results. We create a host
+    // implementation of that function here, and the `caller` parameter here is
+    // used to get access to our original `MyState` value.
+    println!("Creating callback...");
+    let hello_func = Func::wrap(&mut store, |mut caller: Caller<'_, MyState>| {
+        println!("Calling back...");
+        println!("> {}", caller.data().name);
+        caller.data_mut().count += 1;
+    });
 
-    // All wasm objects operate within the context of a "store". Each
-    // `Store` has a type parameter to store host-specific data, which in
-    // this case we're using `4` for.
-    let mut store = Store::new(&engine, 4);
-    let instance = linker.instantiate(&mut store, &module)?;
-    let hello = instance.get_typed_func::<(), ()>(&mut store, "hello")?;
+    // Once we've got that all set up we can then move to the instantiation
+    // phase, pairing together a compiled module as well as a set of imports.
+    // Note that this is where the wasm `start` function, if any, would run.
+    println!("Instantiating module...");
+    let imports = [hello_func.into()];
+    let instance = Instance::new(&mut store, &module, &imports)?;
 
-    // And finally we can call the wasm!
-    hello.call(&mut store, ())?;
+    // Next we poke around a bit to extract the `run` function from the module.
+    println!("Extracting export...");
+    let run = instance.get_typed_func::<(), ()>(&mut store, "run")?;
 
+    // And last but not least we can call it!
+    println!("Calling export...");
+    run.call(&mut store, ())?;
+
+    println!("Done.");
     Ok(())
 }