C / C++ / MFC

Re: idispatch concepts not understood

13-Nov-07 7:57

For C++ developers to understand COM I highly recommend the book Inside Com - Dale Rogerson[^]

This is one of the best books I ever read, period.

bob1697213-Nov-07 16:16

bob16972

13-Nov-07 16:16

led mike wrote:
This is one of the best books I ever read

I never thought I'd ever hear anyone ever say that about a COM book.;P

Anyone who can chew up COM (in C++) and still laugh... I'm speechless.

Sending data - TCP connection

bigdenny20013-Nov-07 7:00

13-Nov-07 7:00

Hey all,

I have implemented a simple TCP server/client class from the following web-site
(http://www.codeproject.com/internet/winsockintro02.asp). Which shows us how
to send raw char* data over the TCP connection.

My problem is that I want to be able to send a whole instance of a class, for example
ClassFoo objectFoo; i.e. I want to be able to send the object:

<br />
objectFoo

, instead of just text, i.e. "hello".

Can anyone help me, by hinting how to achieve this ?

Thanks

Jim Crafton13-Nov-07 7:10

Jim Crafton

13-Nov-07 7:10

You need to do what is frequently referred to as "Marshalling", in other words, you need to convert an instance of your class into a byte stream, and then, when you recv this byte stream from a source, you need to be able to "reconstitute" it. Look up marshalling for ideas on how to do this. COM supports this and performs it automatically (as well as allowing you to customize the process if you're crazy enough). I think .Net supports this as well. There are C++ frameworks that also support this, you can look for them.

led mike13-Nov-07 7:16

13-Nov-07 7:16

Jim Crafton wrote:
You need to do what is frequently referred to as "Marshalling"

Isn't marshalling used in terms of memory where reconstituting objects is referred to as serialization?

Jim Crafton13-Nov-07 7:22

Jim Crafton

13-Nov-07 7:22

Actually I was going to ask you the same question! I was going to say "serialization" but then I *thought* (always a dangerous idea) that serialization was just a way to store object data, not necessarily create a new object from scratch. Whereas marshalling was actually the ability to send the object across the wire with all the info needed to completely recreate it from scratch on the other side.

Now that I think about it, I suspect I'm getting my "definition" from how COM does things, which may or may not be the way most other OO frameworks/libraries do things.

led mike13-Nov-07 8:24

13-Nov-07 8:24

Jim Crafton wrote:
Now that I think about it, I suspect I'm getting my "definition" from how COM does things, which may or may not be the way most other OO frameworks/libraries do things.

Well I just checked an according to the Wikipedia they are interchangeable. From my experience I learned about marshalling way back in Remote Procedure Calls and Serialization came later in terms of Objects so I made the connection that way. Learn something new everyday.

led mike13-Nov-07 7:11

13-Nov-07 7:11

bigdenny200 wrote:
Can anyone help me, by hinting how to achieve this ?

It's called "Serialization". You might want to use it as a keyword in Google and read some material to gain a basic understanding of it.

bigdenny20013-Nov-07 8:01

13-Nov-07 8:01

Dear led,

thanks for reply. I found a tutorial, which should have done a serialization, as you suggested.
Below is the code (with my object, instead the one from tutorial):

  // Serialize the object
  std::vector<std::string> word_list;
word_list.push_back(_T("HI"));
ofstream ofs("c:\\fifthgrade.ros", ios::binary);
ofs.write((char *)&word_list, sizeof(word_list));

// Deserialize it
std::vector<std::string> word_list2;
ifstream ifs("c:\\fifthgrade.ros", ios::binary);
ifs.read((char *)&word_list2, sizeof(word_list)); // last line

The problem is that this code (the last line) doesnt work. And I think this is
because I am using not simple Class instances, but a vector object.

Do you have any idea, what could be other reason for it not to work ?

thanks

led mike13-Nov-07 8:20

13-Nov-07 8:20

bigdenny200 wrote:
I found a tutorial

Please provide a link. Either it is not adequate or you have not understood it correctly. I would think most people would take longer than a single hour of studying to understand serialization. You are trying to understand it right? Not just trying to reproduce the tutorial source code for your purposes, that's not going to go well. You need to study it with the goal of understanding it.

bigdenny20013-Nov-07 8:39

13-Nov-07 8:39

I agree with what you are saying, but the problem is that I am working on a project which
is due soon. And I cant devote too much time to serialization only. But, in this case, I really thought that using the tutorial was supposed to work and would suffice.

Here it is: http://www.functionx.com/cpp/articles/serialization.htm,

and it seemed pretty easy for me from here.

Thanks

led mike13-Nov-07 9:17

13-Nov-07 9:17

Yeah, I would not recommend that tutorial. The example "class" used is not a class, it is a simple 'C' data structure and there has been intrinsic support for reading and writing 'C' data structures since.... well 'C'. That is not the same thing as 'Serialization' of complex C++ classes that may contain pointers which are memory addresses.

You cannot serialize a memory address. You must serialize/deserialize the data at the memory address which requires knowledge of the data structure. Knowledge of the data structure is something that only the developer has meaning you cannot rely on the compiler to properly serialize your class.

bigdenny200 wrote:
but the problem is that I am working on a project which
is due soon. And I cant devote too much time to serialization only.

I can't help the fact that poor project management and planning conflicts with reality. I am only a software developer not a magician that can bend time and warp reality. Perhaps your situation now calls for the Post Agile Manifesto approach to software development[^]. I don't recommend it, but if that's what you must do.... whatever.

bigdenny20013-Nov-07 10:36

13-Nov-07 10:36

> I can't help the fact that poor project management and planning conflicts with reality. I am >only a software developer not a magician that can bend time and warp reality. Perhaps your >situation now calls for the Post Agile Manifesto approach to software development[^]. I don't >recommend it, but if that's what you must do.... whatever.

There is no project management, its a University project. Had a lazy life before Wink | ;)

So now, I am tight in my deadlines.

Mark Salsbery13-Nov-07 11:59

Mark Salsbery

13-Nov-07 11:59

bigdenny200 wrote:
So now, I am tight in my deadlines.

Hmm....in the 5 hours this thread has been around, you probably could have researched and implemented serialization for
a class Poke tongue | ;-P

Whether or not you use MFC, I would take a look at Serialization (MFC)[^]
This is an example of a fairly robust, generic, serialization solution.

On the other (easy) end of the solution spectrum, you could simply add a serialize method and
an unserialize method to your class, both of which take a socket as a parameter.
The serialize method would write (binary) all the class' data, one at a time, to the socket.
The unserialize method would read the binary data into the class' members, in the same order it
was serialized. That's a simple, socket-only class serialization solution.

led mike...sorry for posting in your thread Smile | :)

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Bram van Kampen13-Nov-07 13:58

Bram van Kampen

13-Nov-07 13:58

Mark Salsbery wrote:
On the other (easy) end of the solution spectrum, you could simply add a serialize method and
an unserialize method to your class, both of which take a socket as a parameter.

But that will ofcourse only work if the class contains no pointers or virtual functions. If you have already a successful way to save and retrieve to and from a file, your're nearly there if you have no virtual functions. Just use the same code to write to and retrieve from the socket.

Hope you get it together in time Smile | :)

Bram van Kampen

link error

josip cagalj13-Nov-07 6:12

13-Nov-07 6:12

I'm trying to re-build my app and Im getting this error:

<br />
Linking...<br />
uuid.lib(oaidl_i.obj) : fatal error LNK1103: debugging information corrupt; recompile module<br />
Error executing link.exe.

???
I cant get why this is happening?

toxcct13-Nov-07 6:15

toxcct

13-Nov-07 6:15

have you by any chance an instance of your application/dll still loaded in memory ?

also, have you tried a clean all/rebuild all ?

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josip cagalj13-Nov-07 6:24

13-Nov-07 6:24

I'm using VC++ 6.0 I tried 'Build->Clean' and than 'Build->Rebuild All' but still the same error!
How can I checked if I have instance of my app still loaded. I tried using TaskManager but did not found under applications or processes tab.
Thanks for help!

toxcct13-Nov-07 6:28

toxcct

13-Nov-07 6:28

are you building the application in the wrong order ? (not taking care of the interdependencies ?)

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josip cagalj14-Nov-07 3:40

14-Nov-07 3:40

In my app I need 'imapi2.h' so I add d:\vistaSDK\include in my Tools->Options->Directory tab under include files and compile again about mising 'sal.h', I locate it (d:\vistaSDK\vc\include) and include it also.
Now when I try to compile I get:

<br />
uuid.lib(oaidl_i.obj) : fatal error LNK1103: debugging information corrupt; recompile module

???
Thanks for helping me!

josip cagalj14-Nov-07 22:10