Function ExampleMemory

example_test.go:312–436

An example of working with the Memory type to read/write wasm memory.

()

// An example of working with the Memory type to read/write wasm memory.
func ExampleMemory() {
	// Create our `Store` context and then compile a module and create an
	// instance from the compiled module all in one go.
	store := wasmtime.NewStore(wasmtime.NewEngine())
	wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (memory (export "memory") 2 3)

	  (func (export "size") (result i32) (memory.size))
	  (func (export "load") (param i32) (result i32)
	    (i32.load8_s (local.get 0))
	  )
	  (func (export "store") (param i32 i32)
	    (i32.store8 (local.get 0) (local.get 1))
	  )

	  (data (i32.const 0x1000) "\01\02\03\04")
	)
	`)
	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)
	}

	// Load up our exports from the instance
	memory := instance.GetExport(store, "memory").Memory()
	sizeFn := instance.GetFunc(store, "size")
	loadFn := instance.GetFunc(store, "load")
	storeFn := instance.GetFunc(store, "store")

	// some helper functions we'll use below
	call32 := func(f *wasmtime.Func, args ...interface{}) int32 {
		ret, err := f.Call(store, args...)
		if err != nil {
			log.Fatal(err)
		}
		return ret.(int32)
	}
	call := func(f *wasmtime.Func, args ...interface{}) {
		_, err := f.Call(store, args...)
		if err != nil {
			log.Fatal(err)
		}
	}
	assertTraps := func(f *wasmtime.Func, args ...interface{}) {
		_, err := f.Call(store, args...)
		_, ok := err.(*wasmtime.Trap)
		if !ok {
			log.Fatal("expected a trap")
		}
	}