VIDROBOT-3415 Encode/Decode Shaka-Packager Comment

mpd/fixtures/comment.mpd

@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--Generated with https://github.com/shaka-project/shaka-packager version 288eddc863-release-->
+<MPD xmlns="urn:mpeg:dash:schema:mpd:2011" profiles="urn:mpeg:dash:profile:isoff-live:2011" type="dynamic" availabilityStartTime="1970-01-01T00:00:00Z" minimumUpdatePeriod="PT5S" publishTime="1970-01-01T00:00:00Z"></MPD>

mpd/fixtures/segment_list.mpd

@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!--Generated with https://github.com/shaka-project/shaka-packager version 288eddc863-release-->
 <MPD xmlns="urn:mpeg:dash:schema:mpd:2011" profiles="urn:mpeg:dash:profile:isoff-live:2011" type="static" mediaPresentationDuration="PT30.016S" minBufferTime="PT2.000S">
   <Period>
     <BaseURL>http://localhost:8002/dash/</BaseURL>

mpd/fixtures/truncate.mpd

@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!--Generated with https://github.com/shaka-project/shaka-packager version 288eddc863-release-->
 <MPD xmlns="urn:mpeg:dash:schema:mpd:2011" profiles="urn:mpeg:dash:profile:isoff-live:2011" type="dynamic" minBufferTime="PT2S" availabilityStartTime="2019-12-03T20:57:14Z" minimumUpdatePeriod="PT5S" publishTime="2019-12-03T21:05:05Z" timeShiftBufferDepth="PT120S">
   <Period id="0">
     <AdaptationSet frameRate="90000/3000" id="0" segmentAlignment="true" maxWidth="720" contentType="video">

mpd/mpd.go

@@ -88,6 +88,7 @@ type MPD struct {
 	Periods                    []*Period       `xml:"Period,omitempty"`
 	UTCTiming                  *DescriptorType `xml:"UTCTiming,omitempty"`
 	ID                         string          `xml:"id,attr,omitempty"`
+	Comment                    string          `xml:"-"`
 }
 
 type XsiNS struct {

mpd/mpd_read_write.go

@@ -32,7 +32,24 @@ func ReadFromString(xmlStr string) (*MPD, error) {
 func Read(r io.Reader) (*MPD, error) {
 	var mpd MPD
 	d := xml.NewDecoder(r)
-	err := d.Decode(&mpd)
+	var start *xml.StartElement
+	for {
+		token, err := d.Token()
+		if err != nil {
+			return nil, err
+		}
+		switch token := token.(type) {
+		case xml.Comment:
+			mpd.Comment = string(token.Copy())
+		case xml.StartElement:
+			start = &token
+		default:
+		}
+		if start != nil {
+			break
+		}
+	}
+	err := d.DecodeElement(&mpd, start)
 	if err != nil {
 		return nil, err
 	}
@@ -75,13 +92,26 @@ func (m *MPD) WriteToString() (string, error) {
 // Writes an MPD object to an io.Writer interface
 // w - Must implement the io.Writer interface.
 func (m *MPD) Write(w io.Writer) error {
-	b, err := xml.MarshalIndent(m, "", "  ")
+	_, err := w.Write([]byte(xml.Header))
 	if err != nil {
 		return err
 	}
-
-	_, _ = w.Write([]byte(xml.Header))
-	_, _ = w.Write(b)
-	_, _ = w.Write([]byte("\n"))
-	return nil
+	e := xml.NewEncoder(w)
+	e.Indent("", "  ")
+	if string(m.Comment) != "" {
+		if err := e.EncodeToken(xml.Comment(m.Comment)); err != nil {
+			return err
+		}
+		if err := e.Flush(); err != nil {
+			return err
+		}
+		if _, err := w.Write([]byte("\n")); err != nil {
+			return err
+		}
+	}
+	if err := e.Encode(m); err != nil {
+		return err
+	}
+	_, err = w.Write([]byte("\n"))
+	return err
 }

mpd/mpd_read_write_test.go

@@ -489,3 +489,20 @@ func TestWriteToFileTruncate(t *testing.T) {
 	xmlStr = testfixtures.LoadFixture(out)
 	testfixtures.CompareFixture(t, "fixtures/truncate_short.mpd", xmlStr)
 }
+
+func TestReadComment(t *testing.T) {
+	m, err := ReadFromFile("fixtures/comment.mpd")
+	require.NoError(t, err)
+	require.EqualString(t, "Generated with https://github.com/shaka-project/shaka-packager version 288eddc863-release", string(m.Comment))
+}
+
+func TestWriteComment(t *testing.T) {
+	m := MPD{Comment: "Leading Comment"}
+	s, err := m.WriteToString()
+	require.NoError(t, err)
+	answer := `<?xml version="1.0" encoding="UTF-8"?>
+<!--Leading Comment-->
+<MPD></MPD>
+`
+	require.EqualString(t, answer, s)
+}

mpd/segment_list_test.go

@@ -22,7 +22,7 @@ func TestSegmentListDeserialization(t *testing.T) {
 	require.NoError(t, err)
 	if err == nil {
 		expected := getSegmentListMPD()
-
+		require.EqualString(t, m.Comment, "Generated with https://github.com/shaka-project/shaka-packager version 288eddc863-release")
 		require.EqualString(t, expected.Periods[0].BaseURL, m.Periods[0].BaseURL)
 
 		expectedAudioSegList := expected.Periods[0].AdaptationSets[0].Representations[0].SegmentList
@@ -59,6 +59,7 @@ func TestSegmentListDeserialization(t *testing.T) {
 
 func getSegmentListMPD() *MPD {
 	m := NewMPD(DASH_PROFILE_LIVE, "PT30.016S", "PT2.000S")
+	m.Comment = "Generated with https://github.com/shaka-project/shaka-packager version 288eddc863-release"
 	m.period.BaseURL = "http://localhost:8002/dash/"
 
 	aas, _ := m.AddNewAdaptationSetAudioWithID("1", "audio/mp4", true, 1, "English")