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