func unmarshalMap()

in marshal.go [1949:2020]
66 lines of code
16 McCabe index (conditional complexity)

func unmarshalMap(info TypeInfo, data []byte, value interface{}) error {
	mapInfo, ok := info.(CollectionType)
	if !ok {
		return unmarshalErrorf("unmarshal: can not unmarshal none collection type into map")
	}

	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", info, value)
	}
	if data == nil {
		rv.Set(reflect.Zero(t))
		return nil
	}
	n, p, err := readCollectionSize(mapInfo, data)
	if err != nil {
		return err
	}
	if n < 0 {
		return unmarshalErrorf("negative map size %d", n)
	}
	rv.Set(reflect.MakeMapWithSize(t, n))
	data = data[p:]
	for i := 0; i < n; i++ {
		m, p, err := readCollectionSize(mapInfo, data)
		if err != nil {
			return err
		}
		data = data[p:]
		key := reflect.New(t.Key())
		// In case m < 0, the key is null, and unmarshalData should be nil.
		var unmarshalData []byte
		if m >= 0 {
			if len(data) < m {
				return unmarshalErrorf("unmarshal map: unexpected eof")
			}
			unmarshalData = data[:m]
			data = data[m:]
		}
		if err := Unmarshal(mapInfo.Key, unmarshalData, key.Interface()); err != nil {
			return err
		}

		m, p, err = readCollectionSize(mapInfo, data)
		if err != nil {
			return err
		}
		data = data[p:]
		val := reflect.New(t.Elem())

		// In case m < 0, the value is null, and unmarshalData should be nil.
		unmarshalData = nil
		if m >= 0 {
			if len(data) < m {
				return unmarshalErrorf("unmarshal map: unexpected eof")
			}
			unmarshalData = data[:m]
			data = data[m:]
		}
		if err := Unmarshal(mapInfo.Elem, unmarshalData, val.Interface()); err != nil {
			return err
		}

		rv.SetMapIndex(key.Elem(), val.Elem())
	}
	return nil
}