Handles (#22)

* test coverage: make sure aliases to builtins get tested

* trivial support for handles

* add tests for handles

tests/handles.rs

@@ -0,0 +1,76 @@
+use proptest::prelude::*;
+use wiggle_runtime::{GuestError, GuestType};
+use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
+
+const FD_VAL: u32 = 123;
+
+wiggle_generate::from_witx!({
+    witx: ["tests/handles.witx"],
+    ctx: WasiCtx,
+});
+
+impl_errno!(types::Errno);
+
+impl handle_examples::HandleExamples for WasiCtx {
+    fn fd_create(&mut self) -> Result<types::Fd, types::Errno> {
+        Ok(types::Fd::from(FD_VAL))
+    }
+    fn fd_consume(&mut self, fd: types::Fd) -> Result<(), types::Errno> {
+        println!("FD_CONSUME {}", fd);
+        if fd == types::Fd::from(FD_VAL) {
+            Ok(())
+        } else {
+            Err(types::Errno::InvalidArg)
+        }
+    }
+}
+
+#[derive(Debug)]
+struct HandleExercise {
+    pub return_loc: MemArea,
+}
+
+impl HandleExercise {
+    pub fn test(&self) {
+        let mut ctx = WasiCtx::new();
+        let mut host_memory = HostMemory::new();
+        let mut guest_memory = host_memory.guest_memory();
+
+        let e = handle_examples::fd_create(&mut ctx, &mut guest_memory, self.return_loc.ptr as i32);
+
+        assert_eq!(e, types::Errno::Ok.into(), "fd_create error");
+
+        let h_got: u32 = *guest_memory
+            .ptr(self.return_loc.ptr)
+            .expect("return ptr")
+            .as_ref()
+            .expect("return ref_mut");
+
+        assert_eq!(h_got, 123, "fd_create return val");
+
+        let e = handle_examples::fd_consume(&mut ctx, &mut guest_memory, h_got as i32);
+
+        assert_eq!(e, types::Errno::Ok.into(), "fd_consume error");
+
+        let e = handle_examples::fd_consume(&mut ctx, &mut guest_memory, h_got as i32 + 1);
+
+        assert_eq!(
+            e,
+            types::Errno::InvalidArg.into(),
+            "fd_consume invalid error"
+        );
+    }
+
+    pub fn strat() -> BoxedStrategy<Self> {
+        (HostMemory::mem_area_strat(types::Fd::size()))
+            .prop_map(|return_loc| HandleExercise { return_loc })
+            .boxed()
+    }
+}
+
+proptest! {
+    #[test]
+    fn handle_exercise(e in HandleExercise::strat()) {
+        e.test()
+    }
+}