Fix totalLost count error in receiverStream

Fixes #157

pkg/report/receiver_stream.go

@@ -12,6 +12,13 @@ import (
 	"github.com/pion/rtp"
 )
 
+const (
+	// packetsPerHistoryEntry represents how many packets are in the bitmask for
+	// each entry in the `packets` slice in the receiver stream. Because we use
+	// a uint64, we can keep track of 64 packets per entry.
+	packetsPerHistoryEntry = 64
+)
+
 type receiverStream struct {
 	ssrc         uint32
 	receiverSSRC uint32
@@ -86,18 +93,18 @@ func (stream *receiverStream) processRTP(now time.Time, pktHeader *rtp.Header) {
 }
 
 func (stream *receiverStream) setReceived(seq uint16) {
-	pos := seq % stream.size
-	stream.packets[pos/64] |= 1 << (pos % 64)
+	pos := seq % (stream.size * packetsPerHistoryEntry)
+	stream.packets[pos/packetsPerHistoryEntry] |= 1 << (pos % packetsPerHistoryEntry)
 }
 
 func (stream *receiverStream) delReceived(seq uint16) {
-	pos := seq % stream.size
-	stream.packets[pos/64] &^= 1 << (pos % 64)
+	pos := seq % (stream.size * packetsPerHistoryEntry)
+	stream.packets[pos/packetsPerHistoryEntry] &^= 1 << (pos % packetsPerHistoryEntry)
 }
 
 func (stream *receiverStream) getReceived(seq uint16) bool {
-	pos := seq % stream.size
-	return (stream.packets[pos/64] & (1 << (pos % 64))) != 0
+	pos := seq % (stream.size * packetsPerHistoryEntry)
+	return (stream.packets[pos/packetsPerHistoryEntry] & (1 << (pos % packetsPerHistoryEntry))) != 0
 }
 
 func (stream *receiverStream) processSenderReport(now time.Time, sr *rtcp.SenderReport) {

pkg/report/receiver_stream_test.go

@@ -0,0 +1,29 @@
+package report
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestReceiverStream(t *testing.T) {
+	t.Run("can use entire history size", func(t *testing.T) {
+		stream := newReceiverStream(12345, 90000)
+		maxPackets := stream.size * packetsPerHistoryEntry
+
+		// We shouldn't wrap around so long as we only try maxPackets worth.
+		for seq := uint16(0); seq < maxPackets; seq++ {
+			require.False(t, stream.getReceived(seq), "packet with SN %v shouldn't be received yet", seq)
+			stream.setReceived(seq)
+			require.True(t, stream.getReceived(seq), "packet with SN %v should now be received", seq)
+		}
+
+		// Delete should also work.
+		for seq := uint16(0); seq < maxPackets; seq++ {
+			require.True(t, stream.getReceived(seq), "packet with SN %v should still be marked as received", seq)
+			stream.delReceived(seq)
+			require.False(t, stream.getReceived(seq), "packet with SN %v should no longer be received", seq)
+		}
+	})
+
+}