chore: Add test to JB receiver interceptor read

Ensure reads only use length returned from upstream

pkg/jitterbuffer/receiver_interceptor.go

@@ -64,8 +64,8 @@ func NewInterceptor(opts ...ReceiverInterceptorOption) (*InterceptorFactory, err
 	return &InterceptorFactory{opts}, nil
 }
 
-// BindRemoteStream lets you modify any incoming RTP packets. It is called once for per RemoteStream. The returned method
-// will be called once per rtp packet.
+// BindRemoteStream lets you modify any incoming RTP packets. It is called once per
+// RemoteStream. The returned method will be called once per rtp packet.
 func (i *ReceiverInterceptor) BindRemoteStream(_ *interceptor.StreamInfo, reader interceptor.RTPReader) interceptor.RTPReader {
 	return interceptor.RTPReaderFunc(func(b []byte, a interceptor.Attributes) (int, interceptor.Attributes, error) {
 		buf := make([]byte, len(b))

pkg/jitterbuffer/receiver_interceptor_test.go

@@ -5,6 +5,7 @@ package jitterbuffer
 
 import (
 	"bytes"
+	"errors"
 	"testing"
 	"time"
 
@@ -17,8 +18,6 @@ import (
 )
 
 func TestBufferStart(t *testing.T) {
-	buf := bytes.Buffer{}
-
 	factory, err := NewInterceptor(
 		Log(logging.NewDefaultLoggerFactory().NewLogger("test")),
 	)
@@ -27,8 +26,6 @@ func TestBufferStart(t *testing.T) {
 	i, err := factory.NewInterceptor("")
 	assert.NoError(t, err)
 
-	assert.Zero(t, buf.Len())
-
 	stream := test.NewMockStream(&interceptor.StreamInfo{
 		SSRC:      123456,
 		ClockRate: 90000,
@@ -55,7 +52,6 @@ func TestBufferStart(t *testing.T) {
 	}
 	err = i.Close()
 	assert.NoError(t, err)
-	assert.Zero(t, buf.Len())
 }
 
 func TestReceiverBuffersAndPlaysout(t *testing.T) {
@@ -96,3 +92,51 @@ func TestReceiverBuffersAndPlaysout(t *testing.T) {
 	err = i.Close()
 	assert.NoError(t, err)
 }
+
+type MockRTPReader struct {
+	readFunc func([]byte, interceptor.Attributes) (int, interceptor.Attributes, error)
+}
+
+func (m *MockRTPReader) Read(data []byte, attrs interceptor.Attributes) (int, interceptor.Attributes, error) {
+	if m.readFunc != nil {
+		return m.readFunc(data, attrs)
+	}
+	return 0, nil, errors.New("mock function not implemented")
+}
+
+func NewMockRTPReader(readFunc func([]byte, interceptor.Attributes) (int, interceptor.Attributes, error)) *MockRTPReader {
+	return &MockRTPReader{
+		readFunc: readFunc,
+	}
+}
+
+func TestReceiverInterceptorHonorsBufferLength(t *testing.T) {
+	buf := []byte{0x80, 0x88, 0xe6, 0xfd, 0x01, 0x01, 0x01, 0x01, 0x01,
+		0xde, 0xad, 0xbe, 0xef, 0x01, 0x01, 0x01, 0x01, 0x01}
+	readBuf := make([]byte, 2048)
+	copy(readBuf[0:], buf)
+	copy(readBuf[17:], buf)
+	factory, err := NewInterceptor(
+		Log(logging.NewDefaultLoggerFactory().NewLogger("test")),
+	)
+	assert.NoError(t, err)
+
+	i, err := factory.NewInterceptor("")
+
+	rtpReadFn := NewMockRTPReader(func(data []byte, attrs interceptor.Attributes) (int, interceptor.Attributes, error) {
+		copy(data, readBuf)
+		return 7, attrs, nil
+	})
+	reader := i.BindRemoteStream(&interceptor.StreamInfo{
+		SSRC:      123456,
+		ClockRate: 90000,
+	}, rtpReadFn)
+
+	bufLen, _, err := reader.Read(readBuf, interceptor.Attributes{})
+	assert.Contains(t, err.Error(), "7 < 12")
+	assert.Equal(t, 0, bufLen)
+
+	err = i.Close()
+	assert.NoError(t, err)
+
+}