Function ExampleVal_Externref

example_test.go:506–580

Small example of how to use `externref`s.

()

// Small example of how to use `externref`s.
func ExampleVal_Externref() {
	config := wasmtime.NewConfig()
	config.SetWasmReferenceTypes(true)
	store := wasmtime.NewStore(wasmtime.NewEngineWithConfig(config))
	wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (table $table (export "table") 10 externref)

	  (global $global (export "global") (mut externref) (ref.null extern))

	  (func (export "func") (param externref) (result externref)
	    local.get 0
	  )
	)
	`)
	if err != nil {
		log.Fatal(err)
	}
	module, err := wasmtime.NewModule(store.Engine, wasm)
	if err != nil {
		log.Fatal(err)
	}
	instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{})
	if err != nil {
		log.Fatal(err)
	}
	// Create a new `externref` value.
	value := wasmtime.ValExternref("Hello, World!")
	// The `externref`'s wrapped data should be the string "Hello, World!".
	externRef := value.Externref()
	if externRef != "Hello, World!" {
		log.Fatal("unexpected value")
	}
	// Lookup the `table` export.
	table := instance.GetExport(store, "table").Table()
	// Set `table[3]` to our `externref`.
	err = table.Set(store, 3, value)
	if err != nil {
		log.Fatal(err)
	}
	// `table[3]` should now be our `externref`.
	tableValue, err := table.Get(store, 3)
	if err != nil {
		log.Fatal(err)
	}
	if tableValue.Externref() != externRef {
		log.Fatal("unexpected value in table")
	}
	// Lookup the `global` export.
	global := instance.GetExport(store, "global").Global()
	// Set the global to our `externref`.
	err = global.Set(store, value)
	if err != nil {
		log.Fatal(err)
	}
	// Get the global, and it should return our `externref` again.
	globalValue := global.Get(store)
	if globalValue.Externref() != externRef {