calculate number of imported funcs

* calculate number of imported funcs

* add a test to check function's name

wasm/index.go

@@ -82,7 +82,17 @@ func (m *Module) populateFunctions() error {
 	}
 
 	// Add the functions from the wasm itself to the function list
-	numImports := len(m.FunctionIndexSpace)
+
+	// when imported module not provided, len(m.FunctionIndecSpace) == 0
+	// so must calculate number of imported funcs
+	var numImports int
+	if m.Import != nil {
+		for _, importEntry := range m.Import.Entries {
+			if importEntry.Type.Kind() == ExternalFunction {
+				numImports++
+			}
+		}
+	}
 	for codeIndex, typeIndex := range m.Function.Types {
 		if int(typeIndex) >= len(m.Types.Entries) {
 			return InvalidFunctionIndexError(typeIndex)

wasm/module_test.go

@@ -264,3 +264,50 @@ func TestGetFuntionSig(t *testing.T) {
 	}
 
 }
+
+func TestFunctionName(t *testing.T) {
+	f, err := os.Open("testdata/hello-world-tinygo.wasm")
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+
+	defer f.Close()
+	m, err := wasm.ReadModule(f, nil)
+	if err != nil {
+		t.Fatalf("error reading module %v", err)
+	}
+
+	var names wasm.NameMap
+	if s := m.Custom(wasm.CustomSectionName); s != nil {
+		var nSec wasm.NameSection
+		err := nSec.UnmarshalWASM(bytes.NewReader(s.Data))
+		if err != nil {
+			t.Fatalf("error Unmarhsal NameSection %v", err)
+		}
+		if len(nSec.Types[wasm.NameFunction]) > 0 {
+			sub, err := nSec.Decode(wasm.NameFunction)
+			if err != nil {
+				t.Fatalf("error Decode NameFunction %v", err)
+			}
+			funcs, ok := sub.(*wasm.FunctionNames)
+			if ok {
+				names = funcs.Names
+			}
+		}
+	}
+
+	var numImports int
+	if m.Import != nil {
+		for _, importEntry := range m.Import.Entries {
+			if importEntry.Type.Kind() == wasm.ExternalFunction {
+				numImports++
+			}
+		}
+	}
+
+	for index, function := range m.FunctionIndexSpace {
+		if function.Name != names[uint32(index+numImports)] {
+			t.Fatalf("Err:function name expect %s, got %s", names[uint32(index+numImports)], function.Name)
+		}
+	}
+}