Adding data writer

pkg/storage/donut/data/data_v1/data.go

@@ -1,6 +1,11 @@
 package data_v1
 
-import "errors"
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/gob"
+	"io"
+)
 
 type DataHeader struct {
 	Key           string
@@ -23,6 +28,22 @@ type EncoderParams struct {
 	Technique EncoderTechnique
 }
 
-func Write() error {
+func Write(target io.Writer, header DataHeader, data io.Reader) error {
-	return errors.New("Not Implemented")
+	var headerBuffer bytes.Buffer
+	// encode header
+	encoder := gob.NewEncoder(&headerBuffer)
+	encoder.Encode(header)
+	// write length of header
+	if err := binary.Write(target, binary.LittleEndian, headerBuffer.Len()); err != nil {
+		return err
+	}
+	// write encoded header
+	if _, err := io.Copy(target, &headerBuffer); err != nil {
+		return err
+	}
+	// write data
+	if _, err := io.Copy(target, data); err != nil {
+		return err
+	}
+	return nil
 }