Marshalling auto_ptr/unique_ptr objects

From:
Brian <coal@mailvault.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 7 Mar 2010 02:29:27 CST
Message-ID:
<17aca3ba-45ee-423b-80b4-1f8dce40d40f@b30g2000yqd.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::unique_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/build_integration.html --
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

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