streambuf :: getting the data back from a custom stream

For a particular application of mine - I need a simulation of byte
array output stream.

* write data onto a stream
* getback the contiguous content as an array later for network
transport.

My code looks as follows.

#include <iostream>
#include <streambuf>
#include <locale>
#include <cstdio>

using namespace std;
class outbuf : public std::streambuf
{
public:
    virtual ~outbuf()
    {
        sync();
    }
    char * getData() const
    {
        std::cout << "First " << std::hex << (void *)pbase() ;
        std::cout << "Current " << std::hex << (void *)pptr() ;

        return pbase();
    }

    streamsize getSize() const
    {
        return pbase() - pptr();
    }
};

class myostream : public std::basic_ostream<char>
{

public:
    myostream() :
        basic_ostream<char>(new outbuf)
    {
    }
    ~myostream()
    {
        delete rdbuf();
    }
};

int main()
{

    myostream out;

    out << "31 hexadecimal: " << std::hex << 31 << "\n";

    st = out.rdbuf();
    buf = dynamic_cast<outbuf *>(st);
    if (!buf)
    {
        cerr << "error: dynamic_Cast failed";
        return EXIT_FAILURE;
    }

    //TODO: At this point - I need to get the pointer to the beginning
of the buffer and the size of the same.
    buf->getData();

    cerr << "Size: " << buf->getSize() << endl;

    return 0;
}

I had gone about creating a rudimentary derived class implementation
of streambuf and an output stream.
After writing data to the output stream I need to get the number of
bytes written and the pointer to the beginning of the stream. How do I
go about doing the same ??

The above example does not seem to work btw.

Thanks for the help.