diff --git a/common/buf/reader.go b/common/buf/reader.go
index 833fcda51..7f74e76a0 100644
--- a/common/buf/reader.go
+++ b/common/buf/reader.go
@@ -98,27 +98,17 @@ func (r *BufferedReader) ReadAtMost(size int32) (MultiBuffer, error) {
 
 func (r *BufferedReader) writeToInternal(writer io.Writer) (int64, error) {
 	mbWriter := NewWriter(writer)
-	totalBytes := int64(0)
+	var sc SizeCounter
 	if r.Buffer != nil {
-		totalBytes += int64(r.Buffer.Len())
+		sc.Size = int64(r.Buffer.Len())
 		if err := mbWriter.WriteMultiBuffer(r.Buffer); err != nil {
 			return 0, err
 		}
 		r.Buffer = nil
 	}
 
-	for {
-		mb, err := r.Reader.ReadMultiBuffer()
-		if mb != nil {
-			totalBytes += int64(mb.Len())
-			if werr := mbWriter.WriteMultiBuffer(mb); werr != nil {
-				return totalBytes, err
-			}
-		}
-		if err != nil {
-			return totalBytes, err
-		}
-	}
+	err := Copy(r.Reader, mbWriter, CountSize(&sc))
+	return sc.Size, err
 }
 
 // WriteTo implements io.WriterTo.
diff --git a/common/buf/reader_test.go b/common/buf/reader_test.go
index 836df4e52..9e3458423 100644
--- a/common/buf/reader_test.go
+++ b/common/buf/reader_test.go
@@ -2,8 +2,10 @@ package buf_test
 
 import (
 	"io"
+	"strings"
 	"testing"
 
+	"v2ray.com/core/common"
 	. "v2ray.com/core/common/buf"
 	"v2ray.com/core/transport/pipe"
 	. "v2ray.com/ext/assert"
@@ -56,6 +58,25 @@ func TestBytesReaderMultiBuffer(t *testing.T) {
 	assert(mb[1].String(), Equals, "efg")
 }
 
+func TestReadByte(t *testing.T) {
+	sr := strings.NewReader("abcd")
+	reader := &BufferedReader{
+		Reader: NewReader(sr),
+	}
+	b, err := reader.ReadByte()
+	common.Must(err)
+	if b != 'a' {
+		t.Error("unexpected byte: ", b, " want a")
+	}
+
+	var mb MultiBuffer
+	nBytes, err := reader.WriteTo(&mb)
+	common.Must(err)
+	if nBytes != 3 {
+		t.Error("unexpect bytes written: ", nBytes)
+	}
+}
+
 func TestReaderInterface(t *testing.T) {
 	_ = (io.Reader)(new(ReadVReader))
 	_ = (Reader)(new(ReadVReader))