Remove hardcoded kValueSizeBytes values from variable-length header extensions.

webrtc/modules/rtp_rtcp/source/rtp_sender.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
index 6fdac6f63fb08507ec68781c4bff1e59b6ca693e..5803e7bfefdadedf50512eb28b74b4ad839eba69 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
@@ -45,6 +45,14 @@ constexpr int kBitrateStatisticsWindowMs = 1000;
 
 constexpr size_t kMinFlexfecPacketsToStoreForPacing = 50;
 
+// Size info for header extensions that might be used in padding or FEC packets.
+constexpr RtpExtensionSize kExtensionSizes[] = {
+    CreateExtensionSize<AbsoluteSendTime>(),
+    CreateExtensionSize<TransmissionOffset>(),
+    CreateExtensionSize<TransportSequenceNumber>(),
+    CreateExtensionSize<PlayoutDelayLimits>(),
+};
+
 const char* FrameTypeToString(FrameType frame_type) {
   switch (frame_type) {
     case kEmptyFrame:
@@ -157,6 +165,10 @@ RTPSender::~RTPSender() {
   }
 }
 
+rtc::ArrayView<const RtpExtensionSize> RTPSender::FecExtensionSizes() {
+  return kExtensionSizes;
+}
+
 uint16_t RTPSender::ActualSendBitrateKbit() const {
   rtc::CritScope cs(&statistics_crit_);
   return static_cast<uint16_t>(
@@ -277,12 +289,13 @@ void RTPSender::SetMaxRtpPacketSize(size_t max_packet_size) {
   max_packet_size_ = max_packet_size;
 }
 
-size_t RTPSender::MaxPayloadSize() const {
+size_t RTPSender::MaxPayloadSize(

[danilchap, 2017/05/09 12:33:49]

if you agree to remove MaxPayloadSize from rtp_rtcp interface, then this
function can be removed too and it's body incorporated into SendPadData
function.
It will be easier to reason about extension_sizes argument then.

[erikvarga1, 2017/05/09 13:30:30]

Done.

+    rtc::ArrayView<const RtpExtensionSize> extension_sizes) const {
   if (audio_configured_) {
-    return max_packet_size_ - RtpHeaderLength();
+    return max_packet_size_ - RtpHeaderLength(extension_sizes);
   } else {
-    return max_packet_size_ - RtpHeaderLength()   // RTP overhead.
-           - video_->FecPacketOverhead()          // FEC/ULP/RED overhead.
+    return max_packet_size_ - RtpHeaderLength(extension_sizes)  // RTP overhead.
+           - video_->FecPacketOverhead()  // FEC/ULP/RED overhead.
            - (RtxStatus() ? kRtxHeaderSize : 0);  // RTX overhead.
   }
 }
@@ -459,7 +472,8 @@ size_t RTPSender::SendPadData(size_t bytes,
   if (audio_configured_) {
     // Allow smaller padding packets for audio.
     padding_bytes_in_packet =
-        std::min(std::max(bytes, kMinAudioPaddingLength), MaxPayloadSize());
+        std::min(std::max(bytes, kMinAudioPaddingLength),
+                 MaxPayloadSize(kExtensionSizes));
     if (padding_bytes_in_packet > kMaxPaddingLength)
       padding_bytes_in_packet = kMaxPaddingLength;
   } else {
@@ -467,7 +481,8 @@ size_t RTPSender::SendPadData(size_t bytes,
     // RtpPacketSender, which will make sure we don't send too much padding even
     // if a single packet is larger than requested.
     // We do this to avoid frequently sending small packets on higher bitrates.
-    padding_bytes_in_packet = std::min(MaxPayloadSize(), kMaxPaddingLength);
+    padding_bytes_in_packet = std::min(MaxPayloadSize(kExtensionSizes),
+                                       kMaxPaddingLength);
   }
   size_t bytes_sent = 0;
   while (bytes_sent < bytes) {
@@ -957,11 +972,13 @@ void RTPSender::ProcessBitrate() {
                             nack_bitrate_sent_.Rate(now_ms).value_or(0), ssrc);
 }
 
-size_t RTPSender::RtpHeaderLength() const {
+size_t RTPSender::RtpHeaderLength(
+    rtc::ArrayView<const RtpExtensionSize> extension_sizes) const {
   rtc::CritScope lock(&send_critsect_);
   size_t rtp_header_length = kRtpHeaderLength;
   rtp_header_length += sizeof(uint32_t) * csrcs_.size();
-  rtp_header_length += rtp_header_extension_map_.GetTotalLengthInBytes();
+  rtp_header_length +=
+      rtp_header_extension_map_.GetTotalLengthInBytes(extension_sizes);
   return rtp_header_length;
 }