Implement RFC 11: Redesigning Wasmtime's APIs (#2897)

Implement Wasmtime's new API as designed by RFC 11. This is quite a large commit which has had lots of discussion externally, so for more information it's best to read the RFC thread and the PR thread.

crates/wiggle/tests/wasmtime_async.rs

@@ -0,0 +1,160 @@
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+use wasmtime::{Config, Engine, Linker, Module, Store};
+
+wiggle::from_witx!({
+    witx: ["$CARGO_MANIFEST_DIR/tests/atoms.witx"],
+    async: {
+        atoms::{double_int_return_float}
+    }
+});
+
+pub struct Ctx;
+impl wiggle::GuestErrorType for types::Errno {
+    fn success() -> Self {
+        types::Errno::Ok
+    }
+}
+
+#[wiggle::async_trait]
+impl atoms::Atoms for Ctx {
+    fn int_float_args(&mut self, an_int: u32, an_float: f32) -> Result<(), types::Errno> {
+        println!("INT FLOAT ARGS: {} {}", an_int, an_float);
+        Ok(())
+    }
+    async fn double_int_return_float(
+        &mut self,
+        an_int: u32,
+    ) -> Result<types::AliasToFloat, types::Errno> {
+        Ok((an_int as f32) * 2.0)
+    }
+}
+
+#[test]
+fn test_sync_host_func() {
+    let mut store = async_store();
+    let mut linker = Linker::new(store.engine());
+    atoms::add_to_linker(&mut linker, |cx| cx).unwrap();
+    let shim_mod = shim_module(linker.engine());
+    let shim_inst = run(linker.instantiate_async(&mut store, &shim_mod)).unwrap();
+
+    let results = run(shim_inst
+        .get_func(&mut store, "int_float_args_shim")
+        .unwrap()
+        .call_async(&mut store, &[0i32.into(), 123.45f32.into()]))
+    .unwrap();
+
+    assert_eq!(results.len(), 1, "one return value");
+    assert_eq!(
+        results[0].unwrap_i32(),
+        types::Errno::Ok as i32,
+        "int_float_args errno"
+    );
+}
+
+#[test]
+fn test_async_host_func() {
+    let mut store = async_store();
+    let mut linker = Linker::new(store.engine());
+    atoms::add_to_linker(&mut linker, |cx| cx).unwrap();
+
+    let shim_mod = shim_module(linker.engine());
+    let shim_inst = run(linker.instantiate_async(&mut store, &shim_mod)).unwrap();
+
+    let input: i32 = 123;
+    let result_location: i32 = 0;
+
+    let results = run(shim_inst
+        .get_func(&mut store, "double_int_return_float_shim")
+        .unwrap()
+        .call_async(&mut store, &[input.into(), result_location.into()]))
+    .unwrap();
+
+    assert_eq!(results.len(), 1, "one return value");
+    assert_eq!(
+        results[0].unwrap_i32(),
+        types::Errno::Ok as i32,
+        "double_int_return_float errno"
+    );
+
+    // The actual result is in memory:
+    let mem = shim_inst.get_memory(&mut store, "memory").unwrap();
+    let mut result_bytes: [u8; 4] = [0, 0, 0, 0];
+    mem.read(&store, result_location as usize, &mut result_bytes)
+        .unwrap();
+    let result = f32::from_le_bytes(result_bytes);
+    assert_eq!((input * 2) as f32, result);
+}
+
+fn run<F: Future>(future: F) -> F::Output {
+    let mut f = Pin::from(Box::new(future));
+    let waker = dummy_waker();
+    let mut cx = Context::from_waker(&waker);
+    loop {
+        match f.as_mut().poll(&mut cx) {
+            Poll::Ready(val) => break val,
+            Poll::Pending => {}
+        }
+    }
+}
+
+fn dummy_waker() -> Waker {
+    return unsafe { Waker::from_raw(clone(5 as *const _)) };
+
+    unsafe fn clone(ptr: *const ()) -> RawWaker {
+        assert_eq!(ptr as usize, 5);
+        const VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake_by_ref, drop);
+        RawWaker::new(ptr, &VTABLE)
+    }
+
+    unsafe fn wake(ptr: *const ()) {
+        assert_eq!(ptr as usize, 5);
+    }
+
+    unsafe fn wake_by_ref(ptr: *const ()) {
+        assert_eq!(ptr as usize, 5);
+    }
+
+    unsafe fn drop(ptr: *const ()) {
+        assert_eq!(ptr as usize, 5);
+    }
+}
+
+fn async_store() -> Store<Ctx> {
+    Store::new(
+        &Engine::new(Config::new().async_support(true)).unwrap(),
+        Ctx,
+    )
+}
+
+// Wiggle expects the caller to have an exported memory. Wasmtime can only
+// provide this if the caller is a WebAssembly module, so we need to write
+// a shim module:
+fn shim_module(engine: &Engine) -> Module {
+    Module::new(
+        engine,
+        r#"
+        (module
+            (memory 1)
+            (export "memory" (memory 0))
+            (import "atoms" "int_float_args" (func $int_float_args (param i32 f32) (result i32)))
+            (import "atoms" "double_int_return_float" (func $double_int_return_float (param i32 i32) (result i32)))
+
+            (func $int_float_args_shim (param i32 f32) (result i32)
+                local.get 0
+                local.get 1
+                call $int_float_args
+            )
+            (func $double_int_return_float_shim (param i32 i32) (result i32)
+                local.get 0
+                local.get 1
+                call $double_int_return_float
+            )
+            (export "int_float_args_shim" (func $int_float_args_shim))
+            (export "double_int_return_float_shim" (func $double_int_return_float_shim))
+        )
+    "#,
+    )
+    .unwrap()
+}