Add read support of RtpStreamId/RepairedRtpStreamId header extensions.

webrtc/common_types.h

Index: webrtc/common_types.h
diff --git a/webrtc/common_types.h b/webrtc/common_types.h
index e1a4c77d37adf184bb43b0fd87070d635f54d917..1c16199cb1a1c9aa33fbfffca701c50feb35039c 100644
--- a/webrtc/common_types.h
+++ b/webrtc/common_types.h
@@ -19,6 +19,7 @@
 #include <vector>
 
 #include "webrtc/api/video/video_rotation.h"
+#include "webrtc/base/array_view.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/optional.h"
 #include "webrtc/typedefs.h"
@@ -694,6 +695,33 @@ struct PlayoutDelay {
   int max_ms;
 };
 
+class StreamId {
+ public:
+  // Stream id is limited to 16 bytes because it is the maximum length
+  // that can be encoded with one-byte header extensions.
+  static constexpr size_t kMaxSize = 16;
+
+  StreamId() { value_[0] = 0; }
+  explicit StreamId(rtc::ArrayView<const char> value) {
+    Set(value.data(), value.size());
+  }
+  StreamId(const StreamId&) = default;
+  StreamId& operator=(const StreamId&) = default;
+
+  bool empty() const { return value_[0] == 0; }
+  void Set(rtc::ArrayView<const uint8_t> value) {
+    Set(value.data(), value.size());
+  }
+  void Set(const void* data, size_t size);

[nisse-webrtc, 2017/04/10 12:25:00]

I would have expected const char* or const uint8_t* here. Now, there's a
conversion between uint8_t (used by the parsing functions) and char (used for
the supposedly ascii only |value_|). Which is going to be a bit ugly in one way
or the other. But I'm not sure it's the right way to introduce void* in the
interface.

[danilchap, 2017/04/10 13:27:05]

changed to const char* and made the cast explicit.
There still inconsistency between constructor and one-parameter Set function.
But I'm not sure how to remove it without adding conversion to code outside
StreamId.
[tried overloading - it make it worse because blocks implicit conversion from
char[N] parameter]

+
+  friend bool operator==(const StreamId& lhs, const StreamId& rhs) {
+    return strncmp(lhs.value_, rhs.value_, kMaxSize) == 0;
+  }
+
+ private:
+  char value_[kMaxSize];
+};
+
 struct RTPHeaderExtension {
   RTPHeaderExtension();
 
@@ -717,6 +745,12 @@ struct RTPHeaderExtension {
   VideoRotation videoRotation;
 
   PlayoutDelay playout_delay = {-1, -1};
+
+  // For identification of a stream when ssrc is not signaled. See
+  // https://tools.ietf.org/html/draft-ietf-avtext-rid-09
+  // TODO(danilchap): Update url from draft to release version.
+  StreamId stream_id;
+  StreamId repaired_stream_id;
 };
 
 struct RTPHeader {