packet.cpp

Go to the documentation of this file.

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013-2023 Regents of the University of California.
 *
 * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
 *
 * ndn-cxx library is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later version.
 *
 * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
 *
 * You should have received copies of the GNU General Public License and GNU Lesser
 * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
 */
 
#include "ndn-cxx/lp/packet.hpp"
#include "ndn-cxx/lp/fields.hpp"
 
#include <boost/mp11/algorithm.hpp>
 
namespace ndn::lp {
 
namespace {
 
template<typename Tag>
constexpr int8_t
getLocationSortOrder() noexcept
{
  if constexpr (std::is_same_v<Tag, field_location_tags::Header>)
    return 1;
  if constexpr (std::is_same_v<Tag, field_location_tags::Fragment>)
    return 2;
}
 
struct FieldInfo
{
  constexpr
  FieldInfo() noexcept = default;
 
  explicit
  FieldInfo(uint32_t type) noexcept;
 
  uint32_t tlvType = 0;       
  bool isRecognized = false;  
  bool canIgnore = false;     
  bool isRepeatable = false;  
  int8_t locationSortOrder = getLocationSortOrder<field_location_tags::Header>(); 
};
 
FieldInfo::FieldInfo(uint32_t type) noexcept
  : tlvType(type)
{
  boost::mp11::mp_for_each<FieldSet>([this] (auto fieldDecl) {
    if (tlvType == decltype(fieldDecl)::TlvType::value) {
      isRecognized = true;
      isRepeatable = decltype(fieldDecl)::IsRepeatable::value;
      locationSortOrder = getLocationSortOrder<typename decltype(fieldDecl)::FieldLocation>();
    }
  });
 
  if (!isRecognized) {
    canIgnore = tlv::HEADER3_MIN <= tlvType &&
                tlvType <= tlv::HEADER3_MAX &&
                (tlvType & 0x03) == 0x00;
  }
}
 
constexpr bool
compareFieldSortOrder(const FieldInfo& first, const FieldInfo& second) noexcept
{
  return (first.locationSortOrder < second.locationSortOrder) ||
         (first.locationSortOrder == second.locationSortOrder && first.tlvType < second.tlvType);
}
 
} // namespace
 
Packet::Packet() = default;
 
Packet::Packet(const Block& wire)
{
  wireDecode(wire);
}
 
Block
Packet::wireEncode() const
{
  // If no header or trailer, return bare network packet
  auto elements = m_wire.elements();
  if (elements.size() == 1 && elements.front().type() == FragmentField::TlvType::value) {
    elements.front().parse();
    return elements.front().elements().front();
  }
 
  m_wire.encode();
  return m_wire;
}
 
void
Packet::wireDecode(const Block& wire)
{
  if (wire.type() == ndn::tlv::Interest || wire.type() == ndn::tlv::Data) {
    m_wire = Block(tlv::LpPacket);
    add<FragmentField>({wire.begin(), wire.end()});
    return;
  }
 
  if (wire.type() != tlv::LpPacket) {
    NDN_THROW(Error("LpPacket", wire.type()));
  }
 
  wire.parse();
 
  bool isFirst = true;
  FieldInfo prev;
  for (const Block& element : wire.elements()) {
    FieldInfo info(element.type());
 
    if (!info.isRecognized && !info.canIgnore) {
      NDN_THROW(Error("unrecognized field " + to_string(element.type()) + " cannot be ignored"));
    }
 
    if (!isFirst) {
      if (info.tlvType == prev.tlvType && !info.isRepeatable) {
        NDN_THROW(Error("non-repeatable field " + to_string(element.type()) + " cannot be repeated"));
      }
 
      else if (info.tlvType != prev.tlvType && !compareFieldSortOrder(prev, info)) {
        NDN_THROW(Error("fields are not in correct sort order"));
      }
    }
 
    isFirst = false;
    prev = info;
  }
 
  m_wire = wire;
}
 
bool
Packet::comparePos(uint32_t first, const Block& second) noexcept
{
  return compareFieldSortOrder(FieldInfo(first), FieldInfo(second.type()));
}
 
} // namespace ndn::lp