Add read support of RtpStreamId/RepairedRtpStreamId header extensions.

webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
index 1b311e64190cd80eb146ddba3628ac67a503d30d..aebe80253da232043a026a476bcae2fbe6595d86 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
@@ -215,4 +215,44 @@ bool PlayoutDelayLimits::Write(uint8_t* data,
   return true;
 }
 
+// RtpStreamId.
+constexpr RTPExtensionType RtpStreamId::kId;
+constexpr uint8_t RtpStreamId::kValueSizeBytes;
+constexpr const char* RtpStreamId::kUri;
+
+bool RtpStreamId::Parse(rtc::ArrayView<const uint8_t> data, StreamId* rsid) {
+  if (data.empty() || data[0] == 0)  // Valid rsid can't be empty.
+    return false;
+  rsid->Set(data);
+  RTC_DCHECK(!rsid->empty());
+  return true;
+}
+
+bool RtpStreamId::Parse(rtc::ArrayView<const uint8_t> data, std::string* rsid) {

[nisse-webrtc, 2017/04/11 10:42:53]

Are the Parse methods with a std::string result for tests only?

I think it would be better to use the same Parse method in tests as in the
non-test code.

[danilchap, 2017/04/11 12:51:26]

no, std::string is for users of the rtp::Packet,
StreamId - for users of the RTPHeader.
One alternative way - move StreamId parse to rtp_utility, but would prefer to
keep two parsing versions closer to each other to be more sure they are same.
Another alternative way - parse to StreamId, then convert it to a std::string,
but that would involve extra memcpy.

[nisse-webrtc, 2017/04/11 13:34:49]

Ok.

+  if (data.empty() || data[0] == 0)  // Valid rsid can't be empty.
+    return false;
+  const char* str = reinterpret_cast<const char*>(data.data());
+  // If there is a \0 character in the middle of the |data|, treat it as end of
+  // the string. Well-formed rsid shouldn't contain it.
+  rsid->assign(str, strnlen(str, data.size()));
+  RTC_DCHECK(!rsid->empty());
+  return true;
+}
+
+// RepairedRtpStreamId.
+constexpr RTPExtensionType RepairedRtpStreamId::kId;
+constexpr uint8_t RepairedRtpStreamId::kValueSizeBytes;
+constexpr const char* RepairedRtpStreamId::kUri;
+
+// RtpStreamId and RepairedRtpStreamId use the same format to store rsid.
+bool RepairedRtpStreamId::Parse(rtc::ArrayView<const uint8_t> data,
+                                StreamId* rsid) {
+  return RtpStreamId::Parse(data, rsid);
+}
+
+bool RepairedRtpStreamId::Parse(rtc::ArrayView<const uint8_t> data,
+                                std::string* rsid) {
+  return RtpStreamId::Parse(data, rsid);
+}
+
 }  // namespace webrtc