Merge branch 'feature/readonly' into develop

id3.go

@@ -29,6 +29,7 @@ type Tagger interface {
 	DeleteFrames(string) []v2.Framer
 	AddFrames(...v2.Framer)
 	Bytes() []byte
+	Dirty() bool
 	Padding() uint
 	Size() int
 	Version() string
@@ -66,6 +67,10 @@ func Open(name string) (*File, error) {
 func (f *File) Close() error {
 	defer f.file.Close()
 
+	if !f.Dirty() {
+		return nil
+	}
+
 	switch f.Tagger.(type) {
 	case (*v1.Tag):
 		if _, err := f.file.Seek(-v1.TagSize, os.SEEK_END); err != nil {

id3_test.go

@@ -74,6 +74,38 @@ func TestClose(t *testing.T) {
 	}
 }
 
+func TestReadonly(t *testing.T) {
+	before, err := ioutil.ReadFile(testFile)
+	if err != nil {
+		t.Errorf("test file error")
+	}
+
+	file, err := Open(testFile)
+	if err != nil {
+		t.Errorf("Readonly: unable to open file")
+	}
+
+	file.Title()
+	file.Artist()
+	file.Album()
+	file.Year()
+	file.Genre()
+	file.Comments()
+
+	if err := file.Close(); err != nil {
+		t.Errorf("Readonly: unable to close file")
+	}
+
+	after, err := ioutil.ReadFile(testFile)
+	if err != nil {
+		t.Errorf("Readonly: unable to reopen file")
+	}
+
+	if !bytes.Equal(before, after) {
+		t.Errorf("Readonly: tag data modified without set")
+	}
+}
+
 func TestUnsynchTextFrame_RoundTrip(t *testing.T) {
 	var (
 		err              error

v1/id3v1.go

@@ -42,6 +42,7 @@ var (
 type Tag struct {
 	title, artist, album, year, comment string
 	genre                               byte
+	dirty                               bool
 }
 
 func ParseTag(readSeeker io.ReadSeeker) *Tag {
@@ -60,9 +61,14 @@ func ParseTag(readSeeker io.ReadSeeker) *Tag {
 		year:    string(data[93:97]),
 		comment: string(data[97:127]),
 		genre:   data[127],
+		dirty:   false,
 	}
 }
 
+func (t Tag) Dirty() bool {
+	return t.dirty
+}
+
 func (t Tag) Title() string  { return t.title }
 func (t Tag) Artist() string { return t.artist }
 func (t Tag) Album() string  { return t.album }
@@ -82,18 +88,22 @@ func (t Tag) Comments() []string {
 
 func (t *Tag) SetTitle(text string) {
 	t.title = text
+	t.dirty = true
 }
 
 func (t *Tag) SetArtist(text string) {
 	t.artist = text
+	t.dirty = true
 }
 
 func (t *Tag) SetAlbum(text string) {
 	t.album = text
+	t.dirty = true
 }
 
 func (t *Tag) SetYear(text string) {
 	t.year = text
+	t.dirty = true
 }
 
 func (t *Tag) SetGenre(text string) {
@@ -104,6 +114,7 @@ func (t *Tag) SetGenre(text string) {
 			break
 		}
 	}
+	t.dirty = true
 }
 
 func (t Tag) Bytes() []byte {

v2/frame.go

@@ -443,6 +443,7 @@ func (f *UnsynchTextFrame) SetLanguage(language string) error {
 	}
 
 	f.language = language
+	f.changeSize(0)
 	return nil
 }
 

v2/id3v2.go

@@ -23,6 +23,7 @@ type Tag struct {
 	frameHeaderSize       int
 	frameConstructor      func(io.Reader) Framer
 	frameBytesConstructor func(Framer) []byte
+	dirty                 bool
 }
 
 // Creates a new tag
@@ -32,6 +33,7 @@ func NewTag(version byte) *Tag {
 	t := &Tag{
 		Header: header,
 		frames: make(map[string][]Framer),
+		dirty:  false,
 	}
 
 	switch t.version {
@@ -103,6 +105,13 @@ func (t *Tag) changeSize(diff int) {
 	} else {
 		t.padding = uint(d)
 	}
+
+	t.dirty = true
+}
+
+// Modified status of the tag
+func (t Tag) Dirty() bool {
+	return t.dirty
 }
 
 func (t Tag) Bytes() []byte {