Create unit tests for RtpDemuxer

webrtc/call/rtp_demuxer.cc

 /*
  *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/base/checks.h"
 #include "webrtc/call/rtp_demuxer.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_packet_received.h"
 
 namespace webrtc {
 
+namespace {
+
+template <typename Key, typename Value>
+bool MultimapAssociationExists(const std::multimap<Key, Value>& multimap,
+                               Key key,
+                               Value val) {
+  auto it_range = multimap.equal_range(key);
+  using Reference = typename std::multimap<Key, Value>::const_reference;
+  return std::any_of(it_range.first, it_range.second,
+                     [val](Reference elem) { return elem.second == val; });
+}
+
+}  // namespace
+
 RtpDemuxer::RtpDemuxer() {}
 
 RtpDemuxer::~RtpDemuxer() {
   RTC_DCHECK(sinks_.empty());
 }
 
 void RtpDemuxer::AddSink(uint32_t ssrc, RtpPacketSinkInterface* sink) {
   RTC_DCHECK(sink);
+  RTC_DCHECK(!MultimapAssociationExists(sinks_, ssrc, sink));
   sinks_.emplace(ssrc, sink);
 }
 
 size_t RtpDemuxer::RemoveSink(const RtpPacketSinkInterface* sink) {
   RTC_DCHECK(sink);
   size_t count = 0;
   for (auto it = sinks_.begin(); it != sinks_.end(); ) {
     if (it->second == sink) {
       it = sinks_.erase(it);
       ++count;
     } else {
       ++it;
     }
   }
   return count;
 }
 
 bool RtpDemuxer::OnRtpPacket(const RtpPacketReceived& packet) {
   bool found = false;
   auto it_range = sinks_.equal_range(packet.Ssrc());
   for (auto it = it_range.first; it != it_range.second; ++it) {
     found = true;
     it->second->OnRtpPacket(packet);
   }
   return found;
 }
 
 }  // namespace webrtc