Marshalling auto_ptr/unique_ptr objects

From:

Brian <coal@mailvault.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 5 Mar 2010 17:35:49 -0800 (PST)

Message-ID:

<f5c80c08-b360-4f86-b312-4312b457af7e@z4g2000yqa.googlegroups.com>

I'm adding support for auto_ptr/unique_ptr to the C++
Middleware Writer. In the past I've gotten a few pointers
on implementations here and since I'm not an expert on
either of those classes, I would like to get some
feedback on what I have so far. There are two pieces
of input:

class mytype
{
  std::complex<float> c_;
  std::auto_ptr<uint32_t> a_;

  void SendTypeNum(SendCompressedBuffer*) const;
  void SendMemberData(SendCompressedBuffer*) const;

public:
  template <typename B>
  explicit mytype(B* buf);

  void
  Send(SendCompressedBuffer* buf, bool = false) const
  {
    SendMemberData(buf);
  }

  void CalculateMarshallingSize(Counter& cntr) const;
};

And the Middle file is:

tst_shepherd
  (auto_ptr<vector<mytype> >, auto_ptr<uint32_t>, auto_ptr<mytype>)
}

The output is:

// Generated by the C++ Middleware Writer version 1.11

#include <memory>
#include <vector>
#include <tst.hh>
#include <MarshallingFunctions.hh>
#include <ReceiveCompressedBuffer.hh>
#include <SendCompressedBuffer.hh>

extern uint32_t msg_length_max;

struct tst_shepherd
{

void
Send(SendCompressedBuffer* buf, const auto_ptr<vector<mytype> >& abt1,
const auto_ptr<uint32_t>& abt2, const auto_ptr<mytype>& abt3)
{
  Counter cntr(msg_length_max);
  cntr.Add(sizeof(uint32_t));
  groupCount(cntr, false, sizeof(uint16_t), *abt1.get());
  cntr.Add(sizeof(uint32_t));
  abt3->CalculateMarshallingSize(cntr);
  buf->Receive(&msg_id_direct, sizeof(msg_id_direct));
  buf->Receive(&cntr.value_, sizeof(cntr.value_));

  groupSend(buf, false, *abt1.get());

  buf->Receive(abt2.get(), sizeof(uint32_t));

  abt3->Send(buf, false);
  buf->Flush();
}

template <typename B>
void
Receive(B* buf, auto_ptr<vector<mytype> >& abt1, auto_ptr<uint32_t>&
abt2, auto_ptr<mytype>& abt3)
{
  uint32_t headCount[1];
  vector<mytype>* raw1 = new vector<mytype>;
  buf->Give(headCount[0]);
  raw1->reserve(raw1->size() + headCount[0]);
  while (headCount[0] > 0) {
    --headCount[0];
    mytype rep3(buf);
    raw1->push_back(rep3);
  }
  abt1.reset(raw1);

  uint32_t* raw3 = new uint32_t;
  buf->Give(*raw3);
  abt2.reset(raw3);

  mytype* raw4 = new mytype(buf);
  abt3.reset(raw4);
}

};

uint16_t const mytype_num = 7001;

template <typename B>
inline
mytype::mytype(B* buf)
{
  buf->Give(c_);
  uint32_t* raw5 = new uint32_t;
  buf->Give(*raw5);
  a_.reset(raw5);
}

inline void
mytype::CalculateMarshallingSize(Counter& cntr) const
{
  cntr.Add(sizeof(c_));
  cntr.Add(sizeof(uint32_t));
}

inline void
mytype::SendTypeNum(SendCompressedBuffer* buf) const
{
  buf->Receive(&mytype_num, sizeof(mytype_num));
}

inline void
mytype::SendMemberData(SendCompressedBuffer* buf) const
{
  complexSend(buf, c_);
  buf->Receive(a_.get(), sizeof(uint32_t));
}

-----------------------------------------------------------------------

I've only confirmed that the output compiles correctly
on g++ 4.4.2. I'd like to hear ideas on what could be
done to improve the implementation. In particular, I
wonder if the Receive function and mytype's stream
constructor are correct and efficient. If you want to
dig into the details, there's an archive here --
http://webEbenezer.net/misc/direct.tar.bz2 --
that has everything needed to compile the above
code. The implementation for unique_ptr is the
same, except it pulls in the file "utility" rather than
"memory." Thanks in advance.

Brian Wood
http://webEbenezer.net
(651) 251-9384