packet.cc

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/*
 * Copyright (c) 2005,2006 INRIA
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
 */
#include "packet.h"
 
#include "ns3/assert.h"
#include "ns3/log.h"
#include "ns3/simulator.h"
 
#include <cstdarg>
#include <string>
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("Packet");
 
uint32_t Packet::m_globalUid = 0;
 
TypeId
ByteTagIterator::Item::GetTypeId() const
{
    return m_tid;
}
 
uint32_t
ByteTagIterator::Item::GetStart() const
{
    return m_start;
}
 
uint32_t
ByteTagIterator::Item::GetEnd() const
{
    return m_end;
}
 
void
ByteTagIterator::Item::GetTag(Tag& tag) const
{
    if (tag.GetInstanceTypeId() != GetTypeId())
    {
        NS_FATAL_ERROR("The tag you provided is not of the right type.");
    }
    tag.Deserialize(m_buffer);
}
 
ByteTagIterator::Item::Item(TypeId tid, uint32_t start, uint32_t end, TagBuffer buffer)
    : m_tid(tid),
      m_start(start),
      m_end(end),
      m_buffer(buffer)
{
}
 
bool
ByteTagIterator::HasNext() const
{
    return m_current.HasNext();
}
 
ByteTagIterator::Item
ByteTagIterator::Next()
{
    ByteTagList::Iterator::Item i = m_current.Next();
    return ByteTagIterator::Item(i.tid,
                                 i.start - m_current.GetOffsetStart(),
                                 i.end - m_current.GetOffsetStart(),
                                 i.buf);
}
 
ByteTagIterator::ByteTagIterator(ByteTagList::Iterator i)
    : m_current(i)
{
}
 
PacketTagIterator::PacketTagIterator(const PacketTagList::TagData* head)
    : m_current(head)
{
}
 
bool
PacketTagIterator::HasNext() const
{
    return m_current != nullptr;
}
 
PacketTagIterator::Item
PacketTagIterator::Next()
{
    NS_ASSERT(HasNext());
    const PacketTagList::TagData* prev = m_current;
    m_current = m_current->next;
    return PacketTagIterator::Item(prev);
}
 
PacketTagIterator::Item::Item(const PacketTagList::TagData* data)
    : m_data(data)
{
}
 
TypeId
PacketTagIterator::Item::GetTypeId() const
{
    return m_data->tid;
}
 
void
PacketTagIterator::Item::GetTag(Tag& tag) const
{
    NS_ASSERT(tag.GetInstanceTypeId() == m_data->tid);
    tag.Deserialize(TagBuffer((uint8_t*)m_data->data, (uint8_t*)m_data->data + m_data->size));
}
 
Ptr<Packet>
Packet::Copy() const
{
    // we need to invoke the copy constructor directly
    // rather than calling Create because the copy constructor
    // is private.
    return Ptr<Packet>(new Packet(*this), false);
}
 
Packet::Packet()
    : m_buffer(),
      m_byteTagList(),
      m_packetTagList(),
      /* The upper 32 bits of the packet id in
       * metadata is for the system id. For non-
       * distributed simulations, this is simply
       * zero.  The lower 32 bits are for the
       * global UID
       */
      m_metadata(static_cast<uint64_t>(Simulator::GetSystemId()) << 32 | m_globalUid, 0),
      m_nixVector(nullptr)
{
    m_globalUid++;
}
 
Packet::Packet(const Packet& o)
    : m_buffer(o.m_buffer),
      m_byteTagList(o.m_byteTagList),
      m_packetTagList(o.m_packetTagList),
      m_metadata(o.m_metadata)
{
    o.m_nixVector ? m_nixVector = o.m_nixVector->Copy() : m_nixVector = nullptr;
}
 
Packet&
Packet::operator=(const Packet& o)
{
    if (this == &o)
    {
        return *this;
    }
    m_buffer = o.m_buffer;
    m_byteTagList = o.m_byteTagList;
    m_packetTagList = o.m_packetTagList;
    m_metadata = o.m_metadata;
    o.m_nixVector ? m_nixVector = o.m_nixVector->Copy() : m_nixVector = nullptr;
    return *this;
}
 
Packet::Packet(uint32_t size)
    : m_buffer(size),
      m_byteTagList(),
      m_packetTagList(),
      /* The upper 32 bits of the packet id in
       * metadata is for the system id. For non-
       * distributed simulations, this is simply
       * zero.  The lower 32 bits are for the
       * global UID
       */
      m_metadata(static_cast<uint64_t>(Simulator::GetSystemId()) << 32 | m_globalUid, size),
      m_nixVector(nullptr)
{
    m_globalUid++;
}
 
Packet::Packet(const uint8_t* buffer, uint32_t size, bool magic)
    : m_buffer(0, false),
      m_byteTagList(),
      m_packetTagList(),
      m_metadata(0, 0),
      m_nixVector(nullptr)
{
    NS_ASSERT(magic);
    Deserialize(buffer, size);
}
 
Packet::Packet(const uint8_t* buffer, uint32_t size)
    : m_buffer(),
      m_byteTagList(),
      m_packetTagList(),
      /* The upper 32 bits of the packet id in
       * metadata is for the system id. For non-
       * distributed simulations, this is simply
       * zero.  The lower 32 bits are for the
       * global UID
       */
      m_metadata(static_cast<uint64_t>(Simulator::GetSystemId()) << 32 | m_globalUid, size),
      m_nixVector(nullptr)
{
    m_globalUid++;
    m_buffer.AddAtStart(size);
    Buffer::Iterator i = m_buffer.Begin();
    i.Write(buffer, size);
}
 
Packet::Packet(const Buffer& buffer,
               const ByteTagList& byteTagList,
               const PacketTagList& packetTagList,
               const PacketMetadata& metadata)
    : m_buffer(buffer),
      m_byteTagList(byteTagList),
      m_packetTagList(packetTagList),
      m_metadata(metadata),
      m_nixVector(nullptr)
{
}
 
Ptr<Packet>
Packet::CreateFragment(uint32_t start, uint32_t length) const
{
    NS_LOG_FUNCTION(this << start << length);
    Buffer buffer = m_buffer.CreateFragment(start, length);
    ByteTagList byteTagList = m_byteTagList;
    byteTagList.Adjust(-start);
    NS_ASSERT(m_buffer.GetSize() >= start + length);
    uint32_t end = m_buffer.GetSize() - (start + length);
    PacketMetadata metadata = m_metadata.CreateFragment(start, end);
    // again, call the constructor directly rather than
    // through Create because it is private.
    Ptr<Packet> ret =
        Ptr<Packet>(new Packet(buffer, byteTagList, m_packetTagList, metadata), false);
    ret->SetNixVector(GetNixVector());
    return ret;
}
 
void
Packet::SetNixVector(Ptr<NixVector> nixVector) const
{
    m_nixVector = nixVector;
}
 
Ptr<NixVector>
Packet::GetNixVector() const
{
    return m_nixVector;
}
 
void
Packet::AddHeader(const Header& header)
{
    uint32_t size = header.GetSerializedSize();
    NS_LOG_FUNCTION(this << header.GetInstanceTypeId().GetName() << size);
    m_buffer.AddAtStart(size);
    m_byteTagList.Adjust(size);
    m_byteTagList.AddAtStart(size);
    header.Serialize(m_buffer.Begin());
    m_metadata.AddHeader(header, size);
}
 
uint32_t
Packet::RemoveHeader(Header& header, uint32_t size)
{
    Buffer::Iterator end;
    end = m_buffer.Begin();
    end.Next(size);
    uint32_t deserialized = header.Deserialize(m_buffer.Begin(), end);
    NS_LOG_FUNCTION(this << header.GetInstanceTypeId().GetName() << deserialized);
    m_buffer.RemoveAtStart(deserialized);
    m_byteTagList.Adjust(-deserialized);
    m_metadata.RemoveHeader(header, deserialized);
    return deserialized;
}
 
uint32_t
Packet::RemoveHeader(Header& header)
{
    uint32_t deserialized = header.Deserialize(m_buffer.Begin());
    NS_LOG_FUNCTION(this << header.GetInstanceTypeId().GetName() << deserialized);
    m_buffer.RemoveAtStart(deserialized);
    m_byteTagList.Adjust(-deserialized);
    m_metadata.RemoveHeader(header, deserialized);
    return deserialized;
}
 
uint32_t
Packet::PeekHeader(Header& header) const
{
    uint32_t deserialized = header.Deserialize(m_buffer.Begin());
    NS_LOG_FUNCTION(this << header.GetInstanceTypeId().GetName() << deserialized);
    return deserialized;
}
 
uint32_t
Packet::PeekHeader(Header& header, uint32_t size) const
{
    Buffer::Iterator end;
    end = m_buffer.Begin();
    end.Next(size);
    uint32_t deserialized = header.Deserialize(m_buffer.Begin(), end);
    NS_LOG_FUNCTION(this << header.GetInstanceTypeId().GetName() << deserialized);
    return deserialized;
}
 
void
Packet::AddTrailer(const Trailer& trailer)
{
    uint32_t size = trailer.GetSerializedSize();
    NS_LOG_FUNCTION(this << trailer.GetInstanceTypeId().GetName() << size);
    m_byteTagList.AddAtEnd(GetSize());
    m_buffer.AddAtEnd(size);
    Buffer::Iterator end = m_buffer.End();
    trailer.Serialize(end);
    m_metadata.AddTrailer(trailer, size);
}
 
uint32_t
Packet::RemoveTrailer(Trailer& trailer)
{
    uint32_t deserialized = trailer.Deserialize(m_buffer.End());
    NS_LOG_FUNCTION(this << trailer.GetInstanceTypeId().GetName() << deserialized);
    m_buffer.RemoveAtEnd(deserialized);
    m_metadata.RemoveTrailer(trailer, deserialized);
    return deserialized;
}
 
uint32_t
Packet::PeekTrailer(Trailer& trailer)
{
    uint32_t deserialized = trailer.Deserialize(m_buffer.End());
    NS_LOG_FUNCTION(this << trailer.GetInstanceTypeId().GetName() << deserialized);
    return deserialized;
}
 
void
Packet::AddAtEnd(Ptr<const Packet> packet)
{
    NS_LOG_FUNCTION(this << packet << packet->GetSize());
    m_byteTagList.AddAtEnd(GetSize());
    ByteTagList copy = packet->m_byteTagList;
    copy.AddAtStart(0);
    copy.Adjust(GetSize());
    m_byteTagList.Add(copy);
    m_buffer.AddAtEnd(packet->m_buffer);
    m_metadata.AddAtEnd(packet->m_metadata);
}
 
void
Packet::AddPaddingAtEnd(uint32_t size)
{
    NS_LOG_FUNCTION(this << size);
    m_byteTagList.AddAtEnd(GetSize());
    m_buffer.AddAtEnd(size);
    m_metadata.AddPaddingAtEnd(size);
}
 
void
Packet::RemoveAtEnd(uint32_t size)
{
    NS_LOG_FUNCTION(this << size);
    m_buffer.RemoveAtEnd(size);
    m_metadata.RemoveAtEnd(size);
}
 
void
Packet::RemoveAtStart(uint32_t size)
{
    NS_LOG_FUNCTION(this << size);
    m_buffer.RemoveAtStart(size);
    m_byteTagList.Adjust(-size);
    m_metadata.RemoveAtStart(size);
}
 
void
Packet::RemoveAllByteTags()
{
    NS_LOG_FUNCTION(this);
    m_byteTagList.RemoveAll();
}
 
uint32_t
Packet::CopyData(uint8_t* buffer, uint32_t size) const
{
    return m_buffer.CopyData(buffer, size);
}
 
void
Packet::CopyData(std::ostream* os, uint32_t size) const
{
    return m_buffer.CopyData(os, size);
}
 
uint64_t
Packet::GetUid() const
{
    return m_metadata.GetUid();
}
 
void
Packet::PrintByteTags(std::ostream& os) const
{
    ByteTagIterator i = GetByteTagIterator();
    while (i.HasNext())
    {
        ByteTagIterator::Item item = i.Next();
        os << item.GetTypeId().GetName() << " [" << item.GetStart() << "-" << item.GetEnd() << "]";
        Callback<ObjectBase*> constructor = item.GetTypeId().GetConstructor();
        if (constructor.IsNull())
        {
            if (i.HasNext())
            {
                os << " ";
            }
            continue;
        }
        Tag* tag = dynamic_cast<Tag*>(constructor());
        NS_ASSERT(tag != nullptr);
        os << " ";
        item.GetTag(*tag);
        tag->Print(os);
        if (i.HasNext())
        {
            os << " ";
        }
        delete tag;
    }
}
 
std::string
Packet::ToString() const
{
    std::ostringstream oss;
    Print(oss);
    return oss.str();
}
 
void
Packet::Print(std::ostream& os) const
{
    PacketMetadata::ItemIterator i = m_metadata.BeginItem(m_buffer);
    while (i.HasNext())
    {
        PacketMetadata::Item item = i.Next();
        if (item.isFragment)
        {
            switch (item.type)
            {
            case PacketMetadata::Item::PAYLOAD:
                os << "Payload";
                break;
            case PacketMetadata::Item::HEADER:
            case PacketMetadata::Item::TRAILER:
                os << item.tid.GetName();
                break;
            }
            os << " Fragment [" << item.currentTrimmedFromStart << ":"
               << (item.currentTrimmedFromStart + item.currentSize) << "]";
        }
        else
        {
            switch (item.type)
            {
            case PacketMetadata::Item::PAYLOAD:
                os << "Payload (size=" << item.currentSize << ")";
                break;
            case PacketMetadata::Item::HEADER:
            case PacketMetadata::Item::TRAILER:
                os << item.tid.GetName() << " (";
                {
                    NS_ASSERT(item.tid.HasConstructor());
                    Callback<ObjectBase*> constructor = item.tid.GetConstructor();
                    NS_ASSERT(!constructor.IsNull());
                    ObjectBase* instance = constructor();
                    NS_ASSERT(instance != nullptr);
                    auto chunk = dynamic_cast<Chunk*>(instance);
                    NS_ASSERT(chunk != nullptr);
                    if (item.type == PacketMetadata::Item::HEADER)
                    {
                        Buffer::Iterator end = item.current;
                        end.Next(item.currentSize); // move from start
                        chunk->Deserialize(item.current, end);
                    }
                    else if (item.type == PacketMetadata::Item::TRAILER)
                    {
                        Buffer::Iterator start = item.current;
                        start.Prev(item.currentSize); // move from end
                        chunk->Deserialize(start, item.current);
                    }
                    else
                    {
                        chunk->Deserialize(item.current);
                    }
                    chunk->Print(os);
                    delete chunk;
                }
                os << ")";
                break;
            }
        }
        if (i.HasNext())
        {
            os << " ";
        }
    }
#if 0
  // The code below will work only if headers and trailers
  // define the right attributes which is not the case for
  // now. So, as a temporary measure, we use the
  // headers' and trailers' Print method as shown above.
  PacketMetadata::ItemIterator i = m_metadata.BeginItem (m_buffer);
  while (i.HasNext ())
    {
      PacketMetadata::Item item = i.Next ();
      if (item.isFragment)
        {
          switch (item.type) {
            case PacketMetadata::Item::PAYLOAD:
              os << "Payload";
              break;
            case PacketMetadata::Item::HEADER:
            case PacketMetadata::Item::TRAILER:
              os << item.tid.GetName ();
              break;
            }
          os << " Fragment [" << item.currentTrimmedFromStart<<":"
             << (item.currentTrimmedFromStart + item.currentSize) << "]";
        }
      else
        {
          switch (item.type) {
            case PacketMetadata::Item::PAYLOAD:
              os << "Payload (size=" << item.currentSize << ")";
              break;
            case PacketMetadata::Item::HEADER:
            case PacketMetadata::Item::TRAILER:
              os << item.tid.GetName () << "(";
              {
                NS_ASSERT (item.tid.HasConstructor ());
                Callback<ObjectBase *> constructor = item.tid.GetConstructor ();
                NS_ASSERT (constructor.IsNull ());
                ObjectBase *instance = constructor ();
                NS_ASSERT (instance != 0);
                Chunk *chunk = dynamic_cast<Chunk *> (instance);
                NS_ASSERT (chunk != 0);
                chunk->Deserialize (item.current);
                for (uint32_t j = 0; j < item.tid.GetAttributeN (); j++)
                  {
                    std::string attrName = item.tid.GetAttributeName (j);
                    std::string value;
                    bool ok = chunk->GetAttribute (attrName, value);
                    NS_ASSERT (ok);
                    os << attrName << "=" << value;
                    if ((j + 1) < item.tid.GetAttributeN ())
                      {
                        os << ",";
                      }
                  }
              }
              os << ")";
              break;
            }
        }
      if (i.HasNext ())
        {
          os << " ";
        }
    }
#endif
}
 
PacketMetadata::ItemIterator
Packet::BeginItem() const
{
    return m_metadata.BeginItem(m_buffer);
}
 
void
Packet::EnablePrinting()
{
    NS_LOG_FUNCTION_NOARGS();
    PacketMetadata::Enable();
}
 
void
Packet::EnableChecking()
{
    NS_LOG_FUNCTION_NOARGS();
    PacketMetadata::EnableChecking();
}
 
uint32_t
Packet::GetSerializedSize() const
{
    uint32_t size = 0;
 
    if (m_nixVector)
    {
        // increment total size by the size of the nix-vector
        // ensuring 4-byte boundary
        size += ((m_nixVector->GetSerializedSize() + 3) & (~3));
 
        // add 4-bytes for entry of total length of nix-vector
        size += 4;
    }
    else
    {
        // if no nix-vector, still have to add 4-bytes
        // to account for the entry of total size for
        // nix-vector in the buffer
        size += 4;
    }
 
    // increment total size by size of packet tag list
    // ensuring 4-byte boundary
    size += ((m_packetTagList.GetSerializedSize() + 3) & (~3));
 
    // add 4-bytes for entry of total length of packet tag list
    size += 4;
 
    // increment total size by size of byte tag list
    // ensuring 4-byte boundary
    size += ((m_byteTagList.GetSerializedSize() + 3) & (~3));
 
    // add 4-bytes for entry of total length of byte tag list
    size += 4;
 
    // increment total size by size of meta-data
    // ensuring 4-byte boundary
    size += ((m_metadata.GetSerializedSize() + 3) & (~3));
 
    // add 4-bytes for entry of total length of meta-data
    size += 4;
 
    // increment total size by size of buffer
    // ensuring 4-byte boundary
    size += ((m_buffer.GetSerializedSize() + 3) & (~3));
 
    // add 4-bytes for entry of total length of buffer
    size += 4;
 
    return size;
}
 
uint32_t
Packet::Serialize(uint8_t* buffer, uint32_t maxSize) const
{
    auto p = reinterpret_cast<uint32_t*>(buffer);
    uint32_t size = 0;
 
    // if nix-vector exists, serialize it
    if (m_nixVector)
    {
        uint32_t nixSize = m_nixVector->GetSerializedSize();
        size += nixSize;
        if (size > maxSize)
        {
            return 0;
        }
 
        // put the total length of nix-vector in the
        // buffer. this includes 4-bytes for total
        // length itself
        *p++ = nixSize + 4;
 
        // serialize the nix-vector
        uint32_t serialized = m_nixVector->Serialize(p, nixSize);
        if (!serialized)
        {
            return 0;
        }
 
        // increment p by nixSize bytes
        // ensuring 4-byte boundary
        p += ((nixSize + 3) & (~3)) / 4;
    }
    else
    {
        // no nix vector, set zero length,
        // ie 4-bytes, since it must include
        // length for itself
        size += 4;
        if (size > maxSize)
        {
            return 0;
        }
 
        *p++ = 4;
    }
 
    // Serialize byte tag list
    uint32_t byteTagSize = m_byteTagList.GetSerializedSize();
    size += byteTagSize;
    if (size > maxSize)
    {
        return 0;
    }
 
    // put the total length of byte tag list in the
    // buffer. this includes 4-bytes for total
    // length itself
    *p++ = byteTagSize + 4;
 
    // serialize the byte tag list
    uint32_t serialized = m_byteTagList.Serialize(p, byteTagSize);
    if (!serialized)
    {
        return 0;
    }
 
    // increment p by byteTagSize bytes
    // ensuring 4-byte boundary
    p += ((byteTagSize + 3) & (~3)) / 4;
 
    // Serialize packet tag list
    uint32_t packetTagSize = m_packetTagList.GetSerializedSize();
    size += packetTagSize;
    if (size > maxSize)
    {
        return 0;
    }
 
    // put the total length of packet tag list in the
    // buffer. this includes 4-bytes for total
    // length itself
    *p++ = packetTagSize + 4;
 
    // serialize the packet tag list
    serialized = m_packetTagList.Serialize(p, packetTagSize);
    if (!serialized)
    {
        return 0;
    }
 
    // increment p by packetTagSize bytes
    // ensuring 4-byte boundary
    p += ((packetTagSize + 3) & (~3)) / 4;
 
    // Serialize Metadata
    uint32_t metaSize = m_metadata.GetSerializedSize();
    size += metaSize;
    if (size > maxSize)
    {
        return 0;
    }
 
    // put the total length of metadata in the
    // buffer. this includes 4-bytes for total
    // length itself
    *p++ = metaSize + 4;
 
    // serialize the metadata
    serialized = m_metadata.Serialize(reinterpret_cast<uint8_t*>(p), metaSize);
    if (!serialized)
    {
        return 0;
    }
 
    // increment p by metaSize bytes
    // ensuring 4-byte boundary
    p += ((metaSize + 3) & (~3)) / 4;
 
    // Serialize the packet contents
    uint32_t bufSize = m_buffer.GetSerializedSize();
    size += bufSize;
    if (size > maxSize)
    {
        return 0;
    }
 
    // put the total length of the buffer in the
    // buffer. this includes 4-bytes for total
    // length itself
    *p++ = bufSize + 4;
 
    // serialize the buffer
    serialized = m_buffer.Serialize(reinterpret_cast<uint8_t*>(p), bufSize);
    if (!serialized)
    {
        return 0;
    }
 
    // Serialized successfully
    return 1;
}
 
uint32_t
Packet::Deserialize(const uint8_t* buffer, uint32_t size)
{
    NS_LOG_FUNCTION(this);
 
    auto p = reinterpret_cast<const uint32_t*>(buffer);
 
    // read nix-vector
    NS_ASSERT(!m_nixVector);
    uint32_t nixSize = *p++;
 
    // if size less than nixSize, the buffer
    // will be overrun, assert
    NS_ASSERT(size >= nixSize);
 
    if (nixSize > 4)
    {
        Ptr<NixVector> nix = Create<NixVector>();
        uint32_t nixDeserialized = nix->Deserialize(p, nixSize);
        if (!nixDeserialized)
        {
            // nix-vector not deserialized
            // completely
            return 0;
        }
        m_nixVector = nix;
        // increment p by nixSize ensuring
        // 4-byte boundary
        p += ((((nixSize - 4) + 3) & (~3)) / 4);
    }
    size -= nixSize;
 
    // read byte tags
    uint32_t byteTagSize = *p++;
 
    // if size less than byteTagSize, the buffer
    // will be overrun, assert
    NS_ASSERT(size >= byteTagSize);
 
    uint32_t byteTagDeserialized = m_byteTagList.Deserialize(p, byteTagSize);
    if (!byteTagDeserialized)
    {
        // byte tags not deserialized completely
        return 0;
    }
    // increment p by byteTagSize ensuring
    // 4-byte boundary
    p += ((((byteTagSize - 4) + 3) & (~3)) / 4);
    size -= byteTagSize;
 
    // read packet tags
    uint32_t packetTagSize = *p++;
 
    // if size less than packetTagSize, the buffer
    // will be overrun, assert
    NS_ASSERT(size >= packetTagSize);
 
    uint32_t packetTagDeserialized = m_packetTagList.Deserialize(p, packetTagSize);
    if (!packetTagDeserialized)
    {
        // packet tags not deserialized completely
        return 0;
    }
    // increment p by packetTagSize ensuring
    // 4-byte boundary
    p += ((((packetTagSize - 4) + 3) & (~3)) / 4);
    size -= packetTagSize;
 
    // read metadata
    uint32_t metaSize = *p++;
 
    // if size less than metaSize, the buffer
    // will be overrun, assert
    NS_ASSERT(size >= metaSize);
 
    uint32_t metadataDeserialized =
        m_metadata.Deserialize(reinterpret_cast<const uint8_t*>(p), metaSize);
    if (!metadataDeserialized)
    {
        // meta-data not deserialized
        // completely
        return 0;
    }
    // increment p by metaSize ensuring
    // 4-byte boundary
    p += ((((metaSize - 4) + 3) & (~3)) / 4);
    size -= metaSize;
 
    // read buffer contents
    uint32_t bufSize = *p++;
 
    // if size less than bufSize, the buffer
    // will be overrun, assert
    NS_ASSERT(size >= bufSize);
 
    uint32_t bufferDeserialized =
        m_buffer.Deserialize(reinterpret_cast<const uint8_t*>(p), bufSize);
    if (!bufferDeserialized)
    {
        // buffer not deserialized
        // completely
        return 0;
    }
    size -= bufSize;
 
    // return zero if did not deserialize the
    // number of expected bytes
    return (size == 0);
}
 
void
Packet::AddByteTag(const Tag& tag) const
{
    NS_LOG_FUNCTION(this << tag.GetInstanceTypeId().GetName() << tag.GetSerializedSize());
    auto list = const_cast<ByteTagList*>(&m_byteTagList);
    TagBuffer buffer = list->Add(tag.GetInstanceTypeId(), tag.GetSerializedSize(), 0, GetSize());
    tag.Serialize(buffer);
}
 
void
Packet::AddByteTag(const Tag& tag, uint32_t start, uint32_t end) const
{
    NS_LOG_FUNCTION(this << tag.GetInstanceTypeId().GetName() << tag.GetSerializedSize());
    NS_ABORT_MSG_IF(end < start, "Invalid byte range");
    auto list = const_cast<ByteTagList*>(&m_byteTagList);
    TagBuffer buffer = list->Add(tag.GetInstanceTypeId(),
                                 tag.GetSerializedSize(),
                                 static_cast<int32_t>(start),
                                 static_cast<int32_t>(end));
    tag.Serialize(buffer);
}
 
ByteTagIterator
Packet::GetByteTagIterator() const
{
    return ByteTagIterator(m_byteTagList.Begin(0, GetSize()));
}
 
bool
Packet::FindFirstMatchingByteTag(Tag& tag) const
{
    TypeId tid = tag.GetInstanceTypeId();
    ByteTagIterator i = GetByteTagIterator();
    while (i.HasNext())
    {
        ByteTagIterator::Item item = i.Next();
        if (tid == item.GetTypeId())
        {
            item.GetTag(tag);
            return true;
        }
    }
    return false;
}
 
void
Packet::AddPacketTag(const Tag& tag) const
{
    NS_LOG_FUNCTION(this << tag.GetInstanceTypeId().GetName() << tag.GetSerializedSize());
    m_packetTagList.Add(tag);
}
 
bool
Packet::RemovePacketTag(Tag& tag)
{
    NS_LOG_FUNCTION(this << tag.GetInstanceTypeId().GetName() << tag.GetSerializedSize());
    bool found = m_packetTagList.Remove(tag);
    return found;
}
 
bool
Packet::ReplacePacketTag(Tag& tag)
{
    NS_LOG_FUNCTION(this << tag.GetInstanceTypeId().GetName() << tag.GetSerializedSize());
    bool found = m_packetTagList.Replace(tag);
    return found;
}
 
bool
Packet::PeekPacketTag(Tag& tag) const
{
    bool found = m_packetTagList.Peek(tag);
    return found;
}
 
void
Packet::RemoveAllPacketTags()
{
    NS_LOG_FUNCTION(this);
    m_packetTagList.RemoveAll();
}
 
void
Packet::PrintPacketTags(std::ostream& os) const
{
    PacketTagIterator i = GetPacketTagIterator();
    while (i.HasNext())
    {
        PacketTagIterator::Item item = i.Next();
        NS_ASSERT(item.GetTypeId().HasConstructor());
        Callback<ObjectBase*> constructor = item.GetTypeId().GetConstructor();
        NS_ASSERT(!constructor.IsNull());
        ObjectBase* instance = constructor();
        Tag* tag = dynamic_cast<Tag*>(instance);
        NS_ASSERT(tag != nullptr);
        item.GetTag(*tag);
        tag->Print(os);
        delete tag;
        if (i.HasNext())
        {
            os << " ";
        }
    }
}
 
PacketTagIterator
Packet::GetPacketTagIterator() const
{
    return PacketTagIterator(m_packetTagList.Head());
}
 
std::ostream&
operator<<(std::ostream& os, const Packet& packet)
{
    packet.Print(os);
    return os;
}
 
} // namespace ns3