Golang Value.SetBytes方法代碼示例

// Indirectly this tests that the transaction remembers the NodeID of the node
// being read from correctly, at least in this simple case. Not remembering the
// node would lead to thousands of transaction restarts and almost certainly a
// test timeout.
func TestUncertaintyRestarts(t *testing.T) {
	defer leaktest.AfterTest(t)
	s := createTestDB(t)
	disableOwnNodeCertain(s)
	defer s.Stop()
	// Set a large offset so that a busy restart-loop
	// really shows. Also makes sure that the values
	// we write in the future below don't actually
	// wind up in the past.
	offset := 4000 * time.Millisecond
	s.Clock.SetMaxOffset(offset)
	key := roachpb.Key("key")
	value := roachpb.Value{}
	// With the correct restart behaviour, we see only one restart
	// and the value read is the very first one (as nothing else
	// has been written)
	wantedBytes := []byte("value-0")

	i := -1
	tErr := s.DB.Txn(func(txn *client.Txn) *roachpb.Error {
		i++
		s.Manual.Increment(1)
		futureTS := s.Clock.Now()
		futureTS.WallTime++
		value.SetBytes([]byte(fmt.Sprintf("value-%d", i)))
		if err := engine.MVCCPut(s.Eng, nil, key, futureTS, value, nil); err != nil {
			t.Fatal(err)
		}
		gr, pErr := txn.Get(key)
		if pErr != nil {
			return pErr
		}
		if !gr.Exists() || !bytes.Equal(gr.ValueBytes(), wantedBytes) {
			t.Fatalf("%d: read wrong value: %v, wanted %q", i, gr.Value, wantedBytes)
		}
		return nil
	})
	if i != 1 {
		t.Errorf("txn restarted %d times, expected only one restart", i)
	}
	if tErr != nil {
		t.Fatal(tErr)
	}
}

// marshalValue returns a roachpb.Value initialized from the source
// interface{}, returning an error if the types are not compatible.
func marshalValue(v interface{}) (roachpb.Value, error) {
	var r roachpb.Value

	// Handle a few common types via a type switch.
	switch t := v.(type) {
	case *roachpb.Value:
		return *t, nil

	case nil:
		return r, nil

	case bool:
		i := int64(0)
		if t {
			i = 1
		}
		r.SetInt(i)
		return r, nil

	case string:
		r.SetBytes([]byte(t))
		return r, nil

	case []byte:
		r.SetBytes(t)
		return r, nil

	case inf.Dec:
		err := r.SetDecimal(&t)
		return r, err

	case roachpb.Key:
		r.SetBytes([]byte(t))
		return r, nil

	case time.Time:
		r.SetTime(t)
		return r, nil

	case duration.Duration:
		err := r.SetDuration(t)
		return r, err

	case proto.Message:
		err := r.SetProto(t)
		return r, err
	}

	// Handle all of the Go primitive types besides struct and pointers. This
	// switch also handles types based on a primitive type (e.g. "type MyInt
	// int").
	switch v := reflect.ValueOf(v); v.Kind() {
	case reflect.Bool:
		i := int64(0)
		if v.Bool() {
			i = 1
		}
		r.SetInt(i)
		return r, nil

	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		r.SetInt(v.Int())
		return r, nil

	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		r.SetInt(int64(v.Uint()))
		return r, nil

	case reflect.Float32, reflect.Float64:
		r.SetFloat(v.Float())
		return r, nil

	case reflect.String:
		r.SetBytes([]byte(v.String()))
		return r, nil
	}

	return r, fmt.Errorf("unable to marshal %T: %v", v, v)
}