diff --git a/tests/lux_data_test.go b/tests/lux_data_test.go
new file mode 100644
index 0000000..c2cff75
--- /dev/null
+++ b/tests/lux_data_test.go
@@ -0,0 +1,23 @@
+package tests
+
+import (
+	"bytes"
+	"lux/types"
+	"testing"
+)
+
+func TestWriteGrow(t *testing.T) {
+	first, second := []byte{1, 2, 3, 4}, []byte{5, 6, 7, 8}
+	must := []byte{1, 2, 3, 4, 5, 6, 7, 8}
+
+	buf := types.NewLuxBuffer(4)
+	buf.WriteBytes(first)
+	t.Log(buf.AllBytes())
+
+	buf.WriteBytes(second)
+	t.Log(buf.AllBytes())
+
+	if !bytes.Equal(must, buf.AllBytes()) {
+		t.Fail()
+	}
+}
diff --git a/types/lux_data.go b/types/lux_data.go
new file mode 100644
index 0000000..f6b9967
--- /dev/null
+++ b/types/lux_data.go
@@ -0,0 +1,76 @@
+package types
+
+import (
+	"encoding/binary"
+)
+
+var NO = binary.BigEndian
+
+const MIN_BUFFER_SIZE = 256
+
+type LuxBuffer struct {
+	data   []byte
+	offset int
+	len    int
+}
+
+func NewLuxBuffer(cap int) *LuxBuffer {
+	return &LuxBuffer{
+		data:   make([]byte, cap),
+		offset: 0,
+		len:    0,
+	}
+}
+
+func FromSlice(bytes []byte) *LuxBuffer {
+	return &LuxBuffer{
+		data:   bytes,
+		offset: 0,
+		len:    len(bytes),
+	}
+}
+
+func (buf *LuxBuffer) Capacity() int {
+	return len(buf.data)
+}
+
+func (buf *LuxBuffer) Offset() int {
+	return buf.offset
+}
+
+func (buf *LuxBuffer) Length() int {
+	return buf.len
+}
+
+func (buf *LuxBuffer) Available() int {
+	return buf.Capacity() - buf.Length()
+}
+
+func (buf *LuxBuffer) Grow(grow int) {
+	ocap, ncap := buf.Capacity(), (buf.Capacity()*2 + grow)
+	odata := buf.data
+
+	buf.data = make([]byte, ncap)
+	copy(buf.data[:ocap], odata[:])
+}
+
+// will return byte buffer, sliced to real length
+func (buf *LuxBuffer) AllBytes() []byte {
+	return buf.data[:buf.len]
+}
+
+// ensure capacity for new write, return slice pointing to a place of a new write
+func (buf *LuxBuffer) WriteNext(size int) []byte {
+	if buf.Available() < size {
+		buf.Grow(size)
+	}
+
+	next := buf.data[buf.len : buf.len+size]
+	buf.len += size
+
+	return next
+}
+
+func (buf *LuxBuffer) WriteBytes(bytes []byte) {
+	copy(buf.WriteNext(len(bytes)), bytes)
+}