text: /*
   *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #ifndef WEBRTC_MEDIA_BASE_RTPUTILS_H_
  #define WEBRTC_MEDIA_BASE_RTPUTILS_H_
  
  #include "webrtc/rtc_base/byteorder.h"
  
  namespace rtc {
  struct PacketTimeUpdateParams;
  }  // namespace rtc
  
  namespace cricket {
  
  const size_t kMinRtpPacketLen = 12;
  const size_t kMaxRtpPacketLen = 2048;
  const size_t kMinRtcpPacketLen = 4;
  
  struct RtpHeader {
    int payload_type;
    int seq_num;
    uint32_t timestamp;
    uint32_t ssrc;
  };
  
  enum RtcpTypes {
    kRtcpTypeSR = 200,      // Sender report payload type.
    kRtcpTypeRR = 201,      // Receiver report payload type.
    kRtcpTypeSDES = 202,    // SDES payload type.
    kRtcpTypeBye = 203,     // BYE payload type.
    kRtcpTypeApp = 204,     // APP payload type.
    kRtcpTypeRTPFB = 205,   // Transport layer Feedback message payload type.
    kRtcpTypePSFB = 206,    // Payload-specific Feedback message payload type.
  };
  
  bool GetRtpPayloadType(const void* data, size_t len, int* value);
  bool GetRtpSeqNum(const void* data, size_t len, int* value);
  bool GetRtpTimestamp(const void* data, size_t len, uint32_t* value);
  bool GetRtpSsrc(const void* data, size_t len, uint32_t* value);
  bool GetRtpHeaderLen(const void* data, size_t len, size_t* value);
  bool GetRtcpType(const void* data, size_t len, int* value);
  bool GetRtcpSsrc(const void* data, size_t len, uint32_t* value);
  bool GetRtpHeader(const void* data, size_t len, RtpHeader* header);
  
  bool SetRtpSsrc(void* data, size_t len, uint32_t value);
  // Assumes version 2, no padding, no extensions, no csrcs.
  bool SetRtpHeader(void* data, size_t len, const RtpHeader& header);
  
  bool IsRtpPacket(const void* data, size_t len);
  
  // True if |payload type| is 0-127.
  bool IsValidRtpPayloadType(int payload_type);
  
  // True if |size| is appropriate for the indicated packet type.
  bool IsValidRtpRtcpPacketSize(bool rtcp, size_t size);
  
  // TODO(zstein): Consider using an enum instead of a bool to differentiate
  // between RTP and RTCP.
  // Returns "RTCP" or "RTP" according to |rtcp|.
  const char* RtpRtcpStringLiteral(bool rtcp);
  
  // Verifies that a packet has a valid RTP header.
  bool ValidateRtpHeader(const uint8_t* rtp,
                         size_t length,
                         size_t* header_length);
  
  // Helper method which updates the absolute send time extension if present.
  bool UpdateRtpAbsSendTimeExtension(uint8_t* rtp,
                                     size_t length,
                                     int extension_id,
                                     uint64_t time_us);
  
  // Applies specified |options| to the packet. It updates the absolute send time
  // extension header if it is present present then updates HMAC.
  bool ApplyPacketOptions(uint8_t* data,
                          size_t length,
                          const rtc::PacketTimeUpdateParams& packet_time_params,
                          uint64_t time_us);
  
  
  }  // namespace cricket
  
  #endif  // WEBRTC_MEDIA_BASE_RTPUTILS_H_
  