Added get last packet duration in decoder ctls

decoder.go

@@ -12,6 +12,12 @@ import (
 /*
 #cgo pkg-config: opus
 #include <opus.h>
+
+int
+bridge_decoder_get_last_packet_duration(OpusDecoder *st, opus_int32 *samples)
+{
+	return opus_decoder_ctl(st, OPUS_GET_LAST_PACKET_DURATION(samples));
+}
 */
 import "C"
 
@@ -105,3 +111,13 @@ func (dec *Decoder) DecodeFloat32(data []byte, pcm []float32) (int, error) {
 	}
 	return n, nil
 }
+
+// Gets the duration (in samples) of the last packet successfully decoded or concealed.
+func (dec *Decoder) LastPacketDuration() (int,error){
+	var samples C.opus_int32
+	res := C.bridge_decoder_get_last_packet_duration(dec.p, &samples)
+	if res != C.OPUS_OK {
+		return 0, Error(res)
+	}
+	return int(samples), nil
+}

decoder_test.go

@@ -30,3 +30,39 @@ func TestDecoderUnitialized(t *testing.T) {
 		t.Errorf("Expected \"unitialized decoder\" error: %v", err)
 	}
 }
+
+func TestDecoder_GetLastPacketDuration(t *testing.T) {
+	const G4 = 391.995
+	const SAMPLE_RATE = 48000
+	const FRAME_SIZE_MS = 60
+	const FRAME_SIZE = SAMPLE_RATE * FRAME_SIZE_MS / 1000
+	pcm := make([]int16, FRAME_SIZE)
+	enc, err := NewEncoder(SAMPLE_RATE, 1, AppVoIP)
+	if err != nil || enc == nil {
+		t.Fatalf("Error creating new encoder: %v", err)
+	}
+	addSine(pcm, SAMPLE_RATE, G4)
+
+	data := make([]byte, 1000)
+	n, err := enc.Encode(pcm, data)
+	if err != nil {
+		t.Fatalf("Couldn't encode data: %v", err)
+	}
+	data = data[:n]
+
+	dec, err := NewDecoder(SAMPLE_RATE, 1)
+	if err != nil || dec == nil {
+		t.Fatalf("Error creating new decoder: %v", err)
+	}
+	n, err = dec.Decode(data, pcm)
+	if err != nil {
+		t.Fatalf("Couldn't decode data: %v", err)
+	}
+	samples, err := dec.LastPacketDuration()
+	if err!=nil{
+		t.Fatalf("Couldn't get last packet duration: %v",err)
+	}
+	if samples!=n{
+		t.Fatalf("Wrong duration length. Expected %d. Got %d", n, samples)
+	}
+}