Re: streambuf :: getting the data back from a custom stream

From:
"Jim Langston" <tazmaster@rocketmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 9 Nov 2007 22:39:52 -0800
Message-ID:
<mlcZi.301$Z%4.272@newsfe05.lga>
<rakesh.usenet@gmail.com> wrote in message
news:1194658122.677196.174070@e9g2000prf.googlegroups.com...

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.


I may be missing something, but why don't you just use stringstream?

#include <sstream>
#include <iostream>
#include <string>

int main()
{

    std::stringstream out;

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

    std::cout << "Size: " << out.str().size() << std::endl;
    std::cout << "Data: " << out.str() << std::endl;

    return 0;
}

Output:
Size: 19
Data: 31 hexadecimal: 1f

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