/*
 *  Copyright (c) 2016 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.
 */

#include "webrtc/modules/rtp_rtcp/source/rtcp_packet/common_header.h"

#include "webrtc/base/logging.h"
#include "webrtc/modules/rtp_rtcp/source/byte_io.h"

namespace webrtc {
namespace rtcp {
//    0                   1           1       2                   3
//    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 0 |V=2|P|   C/F   |
//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 1                 |  Packet Type  |
//   ----------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 2                                 |             length            |
//   --------------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//
// Common header for all RTCP packets, 4 octets.
bool CommonHeader::Parse(const uint8_t* buffer, size_t size_bytes) {
  const size_t kHeaderSizeBytes = 4;
  const uint8_t kVersion = 2;

  if (size_bytes < kHeaderSizeBytes) {
    LOG(LS_WARNING) << "Too little data (" << size_bytes << " byte"
                    << (size_bytes != 1 ? "s" : "")
                    << ") remaining in buffer to parse RTCP header (4 bytes).";
    return false;
  }

  uint8_t version = buffer[0] >> 6;
  if (version != kVersion) {
    LOG(LS_WARNING) << "Invalid RTCP header: Version must be "
                    << static_cast<int>(kVersion) << " but was "
                    << static_cast<int>(version);
    return false;
  }

  bool has_padding = (buffer[0] & 0x20) != 0;
  count_or_format_ = buffer[0] & 0x1F;
  packet_type_ = buffer[1];
  payload_size_ = ByteReader<uint16_t>::ReadBigEndian(&buffer[2]) * 4;
  payload_ = buffer + kHeaderSizeBytes;
  padding_size_ = 0;

  if (size_bytes < kHeaderSizeBytes + payload_size_) {
    LOG(LS_WARNING) << "Buffer too small (" << size_bytes
                    << " bytes) to fit an RtcpPacket with a header and "
                    << payload_size_ << " bytes.";
    return false;
  }

  if (has_padding) {
    if (payload_size_ == 0) {
      LOG(LS_WARNING) << "Invalid RTCP header: Padding bit set but 0 payload "
                         "size specified.";
      return false;
    }

    padding_size_ = payload_[payload_size_ - 1];
    if (padding_size_ == 0) {
      LOG(LS_WARNING) << "Invalid RTCP header: Padding bit set but 0 padding "
                         "size specified.";
      return false;
    }
    if (padding_size_ > payload_size_) {
      LOG(LS_WARNING) << "Invalid RTCP header: Too many padding bytes ("
                      << padding_size_ << ") for a packet payload size of "
                      << payload_size_ << " bytes.";
      return false;
    }
    payload_size_ -= padding_size_;
  }
  return true;
}
}  // namespace rtcp
}  // namespace webrtc