func unmarshalUDT()

in marshal.go [2492:2624]
106 lines of code
31 McCabe index (conditional complexity)

func unmarshalUDT(info TypeInfo, data []byte, value interface{}) error {
	switch v := value.(type) {
	case Unmarshaler:
		return v.UnmarshalCQL(info, data)
	case UDTUnmarshaler:
		udt := info.(UDTTypeInfo)

		for id, e := range udt.Elements {
			if len(data) == 0 {
				return nil
			}
			if len(data) < 4 {
				return unmarshalErrorf("can not unmarshal %s: field [%d]%s: unexpected eof", info, id, e.Name)
			}

			var p []byte
			p, data = readBytes(data)
			if err := v.UnmarshalUDT(e.Name, e.Type, p); err != nil {
				return err
			}
		}

		return nil
	case *map[string]interface{}:
		udt := info.(UDTTypeInfo)

		rv := reflect.ValueOf(value)
		if rv.Kind() != reflect.Ptr {
			return unmarshalErrorf("can not unmarshal into non-pointer %T", value)
		}

		rv = rv.Elem()
		t := rv.Type()
		if t.Kind() != reflect.Map {
			return unmarshalErrorf("can not unmarshal %s into %T. Accepted types: Unmarshaler, UDTUnmarshaler, *map[string]interface{}, struct.", info, value)
		} else if data == nil {
			rv.Set(reflect.Zero(t))
			return nil
		}

		rv.Set(reflect.MakeMap(t))
		m := *v

		for id, e := range udt.Elements {
			if len(data) == 0 {
				return nil
			}
			if len(data) < 4 {
				return unmarshalErrorf("can not unmarshal %s: field [%d]%s: unexpected eof", info, id, e.Name)
			}

			valType, err := goType(e.Type)
			if err != nil {
				return unmarshalErrorf("can not unmarshal %s: %v", info, err)
			}

			val := reflect.New(valType)

			var p []byte
			p, data = readBytes(data)

			if err := Unmarshal(e.Type, p, val.Interface()); err != nil {
				return err
			}

			m[e.Name] = val.Elem().Interface()
		}

		return nil
	}

	rv := reflect.ValueOf(value)
	if rv.Kind() != reflect.Ptr {
		return unmarshalErrorf("can not unmarshal into non-pointer %T", value)
	}
	k := rv.Elem()
	if k.Kind() != reflect.Struct || !k.IsValid() {
		return unmarshalErrorf("cannot unmarshal %s into %T. Accepted types: Unmarshaler, UDTUnmarshaler, *map[string]interface{}, *struct.", info, value)
	}

	if len(data) == 0 {
		if k.CanSet() {
			k.Set(reflect.Zero(k.Type()))
		}

		return nil
	}

	t := k.Type()
	fields := make(map[string]reflect.Value, t.NumField())
	for i := 0; i < t.NumField(); i++ {
		sf := t.Field(i)

		if tag := sf.Tag.Get("cql"); tag != "" {
			fields[tag] = k.Field(i)
		}
	}

	udt := info.(UDTTypeInfo)
	for id, e := range udt.Elements {
		if len(data) == 0 {
			return nil
		}
		if len(data) < 4 {
			// UDT def does not match the column value
			return unmarshalErrorf("can not unmarshal %s: field [%d]%s: unexpected eof", info, id, e.Name)
		}

		var p []byte
		p, data = readBytes(data)

		f, ok := fields[e.Name]
		if !ok {
			f = k.FieldByName(e.Name)
			if f == emptyValue {
				// skip fields which exist in the UDT but not in
				// the struct passed in
				continue
			}
		}

		if !f.IsValid() || !f.CanAddr() {
			return unmarshalErrorf("cannot unmarshal %s into %T: field %v is not valid", info, value, e.Name)
		}

		fk := f.Addr().Interface()
		if err := Unmarshal(e.Type, p, fk); err != nil {
			return err
		}
	}

	return nil
}