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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "cast/streaming/packet_util.h"
#include "cast/streaming/rtcp_common.h"
#include "cast/streaming/rtp_defines.h"
namespace openscreen {
namespace cast {
std::pair<ApparentPacketType, Ssrc> InspectPacketForRouting(
absl::Span<const uint8_t> packet) {
// Check for RTP packets first, since they are more frequent.
if (packet.size() >= kRtpPacketMinValidSize &&
packet[0] == kRtpRequiredFirstByte &&
IsRtpPayloadType(packet[1] & kRtpPayloadTypeMask)) {
constexpr int kOffsetToSsrcField = 8;
return std::make_pair(
ApparentPacketType::RTP,
Ssrc{ReadBigEndian<uint32_t>(packet.data() + kOffsetToSsrcField)});
}
// While RTCP packets are valid if they consist of just the RTCP Common
// Header, all the RTCP packet types processed by this implementation will
// also have a SSRC field immediately following the header. This is important
// for routing the packet to the correct parser instance.
constexpr int kRtcpPacketMinAcceptableSize =
kRtcpCommonHeaderSize + sizeof(uint32_t);
if (packet.size() >= kRtcpPacketMinAcceptableSize &&
RtcpCommonHeader::Parse(packet).has_value()) {
return std::make_pair(
ApparentPacketType::RTCP,
Ssrc{ReadBigEndian<uint32_t>(packet.data() + kRtcpCommonHeaderSize)});
}
return std::make_pair(ApparentPacketType::UNKNOWN, Ssrc{0});
}
} // namespace cast
} // namespace openscreen
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