Reland of Create RtcpDemuxer

webrtc/call/rtp_rtcp_demuxer_helper.h

Index: webrtc/call/rtp_rtcp_demuxer_helper.h
diff --git a/webrtc/call/rtp_rtcp_demuxer_helper.h b/webrtc/call/rtp_rtcp_demuxer_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..19bd60324445477e843f923f25d8d3dbe756efc2
--- /dev/null
+++ b/webrtc/call/rtp_rtcp_demuxer_helper.h
@@ -0,0 +1,67 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_CALL_RTP_RTCP_DEMUXER_HELPER_H_
+#define WEBRTC_CALL_RTP_RTCP_DEMUXER_HELPER_H_
+
+#include <algorithm>
+#include <map>
+#include <utility>
+
+#include "webrtc/base/array_view.h"
+#include "webrtc/base/basictypes.h"
+#include "webrtc/base/optional.h"
+
+namespace webrtc {
+
+template <typename Container>
+bool MultimapAssociationExists(const Container& multimap,
+                               const typename Container::key_type& key,
+                               const typename Container::mapped_type& val) {
+  auto it_range = multimap.equal_range(key);
+  using Reference = typename Container::const_reference;
+  return std::any_of(it_range.first, it_range.second,
+                     [val](Reference elem) { return elem.second == val; });
+}
+
+template <typename Container, typename Value>
+size_t RemoveFromMultimapByValue(Container* multimap, const Value& value) {
+  size_t count = 0;
+  for (auto it = multimap->begin(); it != multimap->end();) {
+    if (it->second == value) {
+      it = multimap->erase(it);
+      ++count;
+    } else {
+      ++it;
+    }
+  }
+  return count;
+}
+
+template <typename Container, typename Key>
+bool ContainerHasKey(const Container& c, const Key& k) {
+  return std::find(c.cbegin(), c.cend(), k) != c.cend();
+}
+
+template <typename Container>
+bool MultimapHasValue(const Container& c,
+                      const typename Container::mapped_type& v) {
+  auto predicate = [v](const typename Container::value_type& it) {
+    return it.second == v;
+  };
+  return std::any_of(c.cbegin(), c.cend(), predicate);
+}
+
+rtc::Optional<uint32_t> ParseRtcpPacketSenderSsrc(
+    rtc::ArrayView<const uint8_t> packet);
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_CALL_RTP_RTCP_DEMUXER_HELPER_H_