C / C++ / MFC

15-May-02 18:20

I have created a new stream, which looks like this:

template <class charT, class traits>
class basic_osLogFile : public std::basic_streambuf<charT, traits>
{
...
}

What I want to do is create a class that encapsulates this, so I can easily go:

osLogFile f("c:\\Errors");
f << "error number " << nError << endl;
f.close();

I've tried this:

class osLogFile : public std::ostream
{
public:
osLogFile() : ostream(&msb),ios(0) {}
virtual ~osLogFile() { msb.pubsync(); }

private:
basic_osLogFile<char, std::char_traits<char> > msb;
};

but the errors are:

c:\my code\iostreams\testapp\debugstr\\debugstream.h(68) : error C2512: 'basic_ostream<char,struct std::char_traits<char> >' : no appropriate default constructor available
c:\my code\iostreams\testapp\debugstr\\debugstream.h(68) : error C2614: 'osLogFile' : illegal member initialization: 'ios' is not a base or member
c:\my code\iostreams\testapp\debugstr\\debugstream.h(68) : error C2614: 'osLogFile' : illegal member initialization: 'ostream' is not a base or member

Does anyone have any suggestions ?

Thanks.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

<i>And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned.</i> - <b>Christopher Duncan - 18/04/2002</b>

Maxwell Chen15-May-02 18:59

Maxwell Chen

15-May-02 18:59

Hi CG,

This compiles fine on my PC:

#include <iostreamᡊe9ac73-238b-46be-991d-0f050c37248d

using namespace std;

template<class charT, class T = char_traits<charT> ᡊe9ac73-238b-46be-991d-0f050c37248dclass basic_osLogFile : public std::basic_streambuf<charT, Tᡊe9ac73-238b-46be-991d-0f050c37248d{
};

void main()
{
	basic_osLogFile<char> t;
}

Maxwell Chen

Lets make bugs better!

Christian Graus15-May-02 19:16

15-May-02 19:16

*just rewording this so it does not sound rude* While that works, if you try operator <<, you'll find it is undefined, the stream object is useless.

I need to derived my stream from basic_streambuf, but to create an instance of it, I need to derive from ostream. I can do this:

basic_osLogFile<char> t;
ostream s(t);

but I'd prefer something a little less ugly, which means creating an ostream that can be instantiated as easily as ofstream, but which uses my streambuf.

Do you have any ideas ?

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned. - Christopher Duncan - 18/04/2002

Maxwell Chen15-May-02 20:03

Maxwell Chen

15-May-02 20:03

Christian Graus wrote:
*just rewording this so it does not sound rude* While that works, if you try operator <<, you'll find it is undefined, the stream object is useless.

That's OK, I like step-by-step! Smile | :)

I don't know the details about stream and the hierarchy (haven't pay time to read it), I tried to read your msgs again, this compiles fine:

#include <iostreamᡊe9ac73-238b-46be-991d-0f050c37248d#include <fstreamᡊe9ac73-238b-46be-991d-0f050c37248d
using namespace std;

template<class charT, class T = char_traits<charT> ᡊe9ac73-238b-46be-991d-0f050c37248dclass basic_osLogFile : public std::basic_streambuf<charT, Tᡊe9ac73-238b-46be-991d-0f050c37248d{
};

class osLogFile : public std::ostream 
{
public: 
	osLogFile() : ostream(&msb),ios(0) {} 
	virtual ~osLogFile() { msb.pubsync(); }
	
private: 
	basic_osLogFile<char> msb; 
};



void main()
{
	osLogFile s;

	s << "Hello";
}

Maxwell Chen

Lets make bugs better!

Christian Graus15-May-02 20:32

15-May-02 20:32

You're right - but it only works if I use 'using namespace std' ( which I never do ).

I think if I use std within my own namespace, that might solve my problem somewhat....

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned. - Christopher Duncan - 18/04/2002

Joaquín M López Muñoz15-May-02 20:47

15-May-02 20:47

Try this:

class osLogFile : public std::ostream 
{
        typedef std::ostream ostream;
        typedef std::ios     ios;
public: 
	osLogFile() : ostream(&msb),ios(0) {} 
...

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Christian Graus15-May-02 21:02

Re: iostream problems [edited]

15-May-02 21:02

I did, I get this:

c:\my code\iostreams\testapp\debugstr\\debugstream.h(83) : error C2629: unexpected 'class osLogFile ('
c:\my code\iostreams\testapp\debugstr\\debugstream.h(83) : error C2334: unexpected token(s) preceding ':'; skipping apparent function body

I've made no other changes. replacing the two new lines with a global using namespace std will compile just fine. Obviously I would never do that, but I'm toying with doing it within a namespace I define, and then using mynamespace::osLogFile. would koenig lookup mean that this would pull all of std into the global namespace ?

Obviously if we can get your initial suggestion to work, then that won't matter either way. Smile | :)

Thanks for the help.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned. - Christopher Duncan - 18/04/2002

Joaquín M López Muñoz15-May-02 21:08

15-May-02 21:08

Hmmm... this little pesky compiler isn't behaving, I guess. My suggestion comes from a very similar problem I had in the past. My final solution was like this:

namespace sockiostr{

class socketstream: public std::iostream, noncopyable
{
  private:
    typedef std::iostream super;

  public:
    socketstream():
      super(&sockbuf),
      sockbuf()
    {}
...

and it indeed works.

PS. Of course, in your case the compliant syntax would be

class osLogFile : public std::ostream 
{ 
    public: 
        osLogFile() : std::ostream(&msb),std::ios(0) {}
...

but this won't work in VC++ 5.0 --have you given it a try in VC++ 6.0?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Christian Graus15-May-02 21:11

15-May-02 21:11

noncopyable ? Is that another base ?

Anyhow, it accepts the typedef syntax IF I use namespace std as well, but without using namespace std, it blows up. I guess I'll put it in a namespace and experiment to see if namespace std remains in place when I use it.

Thanks for the help though.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned. - Christopher Duncan - 18/04/2002

Joaquín M López Muñoz15-May-02 21:17

15-May-02 21:17

noncopyable ? Is that another base ?

Yes it is. I copied and pasted from the original source without any modification. I guess the purpose of this base class is obvious, anyway.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Joaquín M López Muñoz15-May-02 21:19

15-May-02 21:19

Off-topic, your explicit construction ios(0) clashes with (and takes precedence over) ostream(&msb). I guess you should omit it.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Christian Graus15-May-02 22:49

15-May-02 22:49

Thanks for the tip. I'm still pretty new at this... Actually I'm writing this to prove to some people at work that doing it with iostreams will be better than using C style string handling, so any tips that make it 'right' are very much appreciated.

Thanks again

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned. - Christopher Duncan - 18/04/2002

C++ Components Question

Nick Parker15-May-02 17:40

15-May-02 17:40

Does anyone know of any articles regarding the creation of a compiled component that I can call from regular ASP through this method:

dim obj
Set obj = Server.CreateObject("...")
obj.CreateGraphics(...)
set obj = nothing

I would like to write a graphics function that I will be able to call within ASP. Any help would be great. Thanks in advance.

Nick Parker

Christian Graus15-May-02 18:17

15-May-02 18:17

Yes, it's a COM component, almost always created with ATL.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

And you don't spend much time with the opposite sex working day and night, unless the pizza delivery person happens to be young, cute, single and female. I can assure you, I've consumed more than a programmer's allotment of pizza, and these conditions have never aligned. - Christopher Duncan - 18/04/2002

Nick Parker15-May-02 18:46

15-May-02 18:46

Thanks Christian, I have been looking for something online but it looks like I may need to create something myself. I haven't been able to find a damn bit about Polar charts in OWC. I think I found an article on CodeGuru for this[ATL Components], but thought I would get everyone else's opinions first. Thanks agian.

Nick Parker

Nish Nishant15-May-02 18:55

Nish Nishant

15-May-02 18:55

If you don't have time to learn ATL, you can use VB 6 to create COM DLLs. I haven't done that, but I do believe it should be an easy process.

Nish

Regards,
Nish
Native CPian.
Born and brought up on CP.
With the CP blood in him.

Nick Parker16-May-02 1:14

16-May-02 1:14

I would like to learn ATL, really, I need to create graphics and we don't have the GDI available in VB 6. Any other ideas Nish? Thanks

Specs:

I only need to be able to draw one line, the direction the line points will be given in degrees, and I also need to label the endpoints to the line. Once this is done, I just need to save it as an image.

Nick Parker

Nish Nishant16-May-02 1:34

Nish Nishant

16-May-02 1:34

Nick Parker wrote:
would like to learn ATL, really, I need to create graphics and we don't have the GDI available in VB 6. Any other ideas Nish? Thanks

Specs:

I only need to be able to draw one line, the direction the line points will be given in degrees, and I also need to label the endpoints to the line. Once this is done, I just need to save it as an image.

Well, ATL is not easy to start with. I mean unlike C# or VB you can't start coding in 2 days time. It takes time to dig in.

And if all you want to do is draw a line, I am sure VB has some line drawing functions.

But then ATL is sorta fun once you get the hang of it. I am still a sorta ATL newbie. I keep trying to find some time for learning it well, but never got the chance and then I am also lazy Smile | :)

Nish

Regards,
Nish
Native CPian.
Born and brought up on CP.
With the CP blood in him.

Nick Parker16-May-02 8:28