Added parsing of values from inner fields of the structure. Close #7

binstruct_test.go

@@ -901,3 +901,19 @@ func Test_sliceSkipWithoutPanic(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, int32(0x02030405), v.I)
 }
+
+func Test_InnerSubField(t *testing.T) {
+	type child struct {
+		Len int8
+	}
+
+	var v struct {
+		Child child
+		S     []byte `bin:"len:Child.Len"`
+	}
+
+	err := UnmarshalBE([]byte{0x05, 0x01, 0x02, 0x03, 0x04, 0x05}, &v)
+	require.NoError(t, err)
+	require.Equal(t, int8(5), v.Child.Len)
+	require.Equal(t, []byte{0x01, 0x02, 0x03, 0x04, 0x05}, v.S)
+}

tag.go

@@ -198,14 +198,24 @@ func parseValue(structValue reflect.Value, v string) (int64, error) {
 	// parse value or get from field
 	l, err := strconv.ParseInt(v, 10, 0)
 	if err != nil {
-		lenVal := structValue.FieldByName(v)
+		sv := structValue
+
+		split := strings.Split(v, ".")
+		for _, s := range split {
+			sv = sv.FieldByName(s)
+			if sv.Kind() != reflect.Struct {
+				break
+			}
+		}
+
+		lenVal := sv
 		switch lenVal.Kind() {
 		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 			l = lenVal.Int()
 		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
 			l = int64(lenVal.Uint())
 		default:
-			return 0, errors.New("can't get field len from " + v + " field")
+			return 0, errors.New("can't get field len from \"" + v + "\" field")
 		}
 	}
 	return l, nil