add support for deleting a single frame

id3.go

@@ -30,6 +30,7 @@ type Tagger interface {
 	AllFrames() []v2.Framer
 	Frames(string) []v2.Framer
 	Frame(string) v2.Framer
+	DeleteFrame(v2.Framer) []v2.Framer
 	DeleteFrames(string) []v2.Framer
 	AddFrames(...v2.Framer)
 	Bytes() []byte

v1/id3v1.go

@@ -140,9 +140,10 @@ func (t Tag) Version() string {
 }
 
 // Dummy methods to satisfy Tagger interface
-func (t Tag) Padding() uint                      { return 0 }
-func (t Tag) AllFrames() []v2.Framer             { return []v2.Framer{} }
-func (t Tag) Frame(id string) v2.Framer          { return nil }
-func (t Tag) Frames(id string) []v2.Framer       { return []v2.Framer{} }
-func (t Tag) DeleteFrames(id string) []v2.Framer { return []v2.Framer{} }
-func (t Tag) AddFrames(f ...v2.Framer)           {}
+func (t Tag) Padding() uint                       { return 0 }
+func (t Tag) AllFrames() []v2.Framer              { return []v2.Framer{} }
+func (t Tag) Frame(id string) v2.Framer           { return nil }
+func (t Tag) Frames(id string) []v2.Framer        { return []v2.Framer{} }
+func (t Tag) DeleteFrames(id string) []v2.Framer  { return []v2.Framer{} }
+func (t Tag) DeleteFrame(f v2.Framer) []v2.Framer { return []v2.Framer{} }
+func (t Tag) AddFrames(f ...v2.Framer)            {}

v2/id3v2.go

@@ -189,6 +189,30 @@ func (t *Tag) DeleteFrames(id string) []Framer {
 	return frames
 }
 
+// Delete the specified frame
+func (t *Tag) DeleteFrame(delFrame Framer) []Framer {
+	frames := t.AllFrames()
+	if frames == nil {
+		return nil
+	}
+
+	diff := 0
+	i := 0
+	for i < len(t.frames) {
+		frame := t.frames[i]
+		if frame == delFrame {
+			frame.setOwner(nil)
+			diff += t.frameHeaderSize + int(frame.Size())
+			t.frames = append(t.frames[:i], t.frames[i+1:]...)
+		} else {
+			i++
+		}
+	}
+	t.changeSize(-diff)
+
+	return frames
+}
+
 // Add frames
 func (t *Tag) AddFrames(frames ...Framer) {
 	for _, frame := range frames {