C / C++ / MFC Discussion Boards

Re: writing a string to a text file

Mark Salsbery25-Jul-07 14:23

Mark Salsbery

25-Jul-07 14:23

Holy cow, that's 2 errors? Smile | :)

Try

results << all_errors[0].c_str() << "\n";

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

Re: writing a string to a text file

Stephen Hewitt25-Jul-07 18:03

Stephen Hewitt

25-Jul-07 18:03

You shouldn't have to do this.

Steve

Re: writing a string to a text file

Mark Salsbery25-Jul-07 18:41

Mark Salsbery

25-Jul-07 18:41

Strike that Smile | :)

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

Re: writing a string to a text file

User 58385225-Jul-07 19:00

User 583852

25-Jul-07 19:00

Compiles fine for me with VS 2005 and no service pack;

I'd try changing "\n" to std::endl

Re: writing a string to a text file

cp987625-Jul-07 19:16

cp9876

25-Jul-07 19:16

Josh Gray wrote:
I'd try changing "\n" to std::endl

This is not related to the OP, but I think there is a tendency to overuse std::endl, I suspect that somehow people think it is more C++ish. The big difference is that std::endl, as well as outputting a new line character, flushes the stream's buffer. For a few random output lines this doesn't matter, but for writing normal files use '\n' and let the stream's buffer do what it is supposed to do. The exception is when you use file-based debugging - here endl is essential as it ensures that in the case of a crash the last line of the file is actually written to disk.

Peter
"Until the invention of the computer, the machine gun was the device that enabled humans to make the most mistakes in the smallest amount of time."

Re: writing a string to a text file

User 58385225-Jul-07 19:37

User 583852

25-Jul-07 19:37

cp9876 wrote:
This is not related to the OP, but I think there is a tendency to overuse std::endl, I suspect that somehow people think it is more C++ish. The big difference is that std::endl, as well as outputting a new line character, flushes the stream's buffer. For a few random output lines this doesn't matter, but for writing normal files use '\n' and let the stream's buffer do what it is supposed to do. The exception is when you use file-based debugging - here endl is essential as it ensures that in the case of a crash the last line of the file is actually written to disk.

Thanks I didnt know that. I always thought the advantage was that it would put the correct line ending for the platform you are running on.

passing vars in PostMessage (wParam, lParam)

john john mackey25-Jul-07 14:08

john john mackey

25-Jul-07 14:08

I am having a more-than-momentary lapse of reason... I want to use the PostMessage( ) function to pass a window handle (CWnd) from one app to another.

In the caller, i have something like this:

   CWnd   hWnd;
// assign hWnd to current window handle (dialog app/dialog-based app window)

   static CWnd *pWnd;
   pWnd = FindWindow("RecvApp",0);
   pWnd->PostMessage(WM_CONNECT_APP, hWnd, 1);

In the receiver application ("RecvApp"):

   // in a header definition file
   CWnd   *pWnd_Caller;

// in MainFrame.cpp - main frame for "RecvApp"

   ON_MESSAGE(WM_CONNECT_APP, OnMakeConnection)

   LRESULT CMainFrame::OnMakeConnect(WPARAM wParam, LPARAM lParam)
   {
      // wParam is the handle to the caller's window/dialog-window

      if (lParam == 1)
         m_View->PostMessage(WM_CONNECT_APP, wParam, lParam);

   }

// in "RecvAppView.cpp" - view frame for "RecvApp"
   // somewhere in a message mapped function, I want to use wParam (hWnd) as
         wParam->PostMessage(WM_ADD_ENTITY, 0, 0);

I want to use the window handle of the caller to post a message back to itself based upon parameters gathered in the receiver app...

(caller) PostMessage (to receiver)

(receiver) assign values, do its stuff...
(receiver) PostMessage (to caller - new values)

In short, I need to know how to pass and use/dereference (etc...) the CWnd handle I am passing around.

Thanks.
Johnny

Re: passing vars in PostMessage (wParam, lParam)

Mark Salsbery25-Jul-07 14:20

Mark Salsbery

25-Jul-07 14:20

You can't pass a CWnd object or a pointer to one. You can pass the HWND that is wrapped by the CWnd
object though.

To obtain the HWND from a CWnd you can use

The HWND cast operator
HWND hWnd = (HWND)MyCWnd;
Use CWd::GetSafeHwnd()
HWND hWnd = pMyCWnd->GetSafeHwnd();

On the receiving end, to get a CWnd from an HWND you can

Create a temporary CWnd object using CWnd::FromHandle()
CWnd *pCWnd = CWnd::FromHandle(hWnd);
For an object that needs to persist, use CWnd::Attach()

pCWnd = new CWnd(); <br />
pCWnd->Attach(hWnd);

Cast an HWND to (WPARAM) or (LPARAM) when passing with PostMessage().

Mark

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

Re: passing vars in PostMessage (wParam, lParam)

ThatsAlok25-Jul-07 20:07

ThatsAlok

25-Jul-07 20:07

john john mackey wrote:
wParam->PostMessage(WM_ADD_ENTITY, 0, 0);

instead of CWnd* send actual HWND by using CWnd::GetSafeHwnd() method and on Receieving end using CWnd::Attach attach that Hwnd to CWnd Pointer!
sending CWnd* is creating problem because the Pointer Address can't be accesible two application!

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief

buffer

dellthinker25-Jul-07 13:51

dellthinker

25-Jul-07 13:51

Hi all, quick question. I dont know how to save to a buffer in C++ only in C with sprintf().

Can anyone tell me how to print to a buf with C++? Thanx in advance!

Re: buffer

Mark Salsbery25-Jul-07 14:09

Mark Salsbery

25-Jul-07 14:09

dellthinker wrote:
I dont know how to save to a buffer in C++

dellthinker wrote:
tell me how to print to a buf with C++

Save...print... what to what kind of buffer?

Mark

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

Re: buffer

ThatsAlok25-Jul-07 20:09

ThatsAlok

25-Jul-07 20:09

dellthinker wrote:
Hi all, quick question. I dont know how to save to a buffer in C++ only in C with sprintf().

sprintf also available in c++ too. are talking abt std::string class

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief

Re: buffer

Karismatic25-Jul-07 20:59

Karismatic

25-Jul-07 20:59

Equivalent to sprintf() you have to use stringstream of STL

for this you can find help from this link
http://msdn2.microsoft.com/en-us/library/7d0zt0ws(VS.80).aspx[^]

when i used i think i have used the "<<" operator to do so

Regards,
Pankaj Sachdeva

Conversion to hexa

AAKAra25-Jul-07 8:33

AAKAra

25-Jul-07 8:33

Hello,
I am storing a card number 9999999999 in the database as hexa format 0x09090909090909090909,
i have to send it to the controller in a pack of 5 binary (in hexa Format), meaning 0x02540BE3FF
any sample code appreciated.
With Rgds,
Anil

Re: Conversion to hexa

Mark Salsbery25-Jul-07 9:47

Mark Salsbery

25-Jul-07 9:47

__int64 llValue = _tstoi64(_T("9999999999"));

Send low-order 5 bytes of llValue

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

Re: Conversion to hexa

Mark Salsbery25-Jul-07 19:02

Mark Salsbery

25-Jul-07 19:02

Wait, I missed half of this earlier...

AnilUnni wrote:
I am storing a card number 9999999999 in the database as hexa format 0x09090909090909090909

Wouldn't ASCII have been easier? Smile | :)

I guess you need to convert those "hexa format" (why the "0x"??) digits to ascii then convert to binary.

Is this homework?

Mark

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

ODBC connection going bad -- what to do?

Robin Hilliard25-Jul-07 7:21

Robin Hilliard

25-Jul-07 7:21

hi -

I've been working on a large multi-threaded VC++ 6.0/MFC application for some years and use ODBC as the main database service provider to a backend database in SQL Server 2000.

For one client's application, though, we notice that the ODBC connection disappears from time to time (their database generally resides on a different machine) and the application crashes when it makes a database request over a handle that's gone bad. As the application has recently started transporting real money, this is unacceptable and I need to know the answers to two questions:

1. Is it possible for the ODBC driver to alert me when it determines that a connection has died, rather than leaving me find out the hard way? The application is idle perhaps 98% of the time and a temporary outage caused by a resurrect-on-connection-death is going to affect the performance far less than a system crash.

2. If there is no answer to (1), is there an alternative to ODBC that will give me this functionality - either something (a) that is stateless and which will allow me to query, read and write the database without requiring handles or (b) or which has a fast connect, so that I can make a connection every time that I need to do something or (c) something that doesn't crash when the connection is lost? You can assume that I'm going to continue using VC++ 6.0/MFC for the foreseeable future.

thanks folks,

- robin.

Re: ODBC connection going bad -- what to do?

cmk25-Jul-07 13:04

cmk

25-Jul-07 13:04

1) I don't think so, i don't recall any callback functionality, nor do i believe the connection is 'live', i think it is like (is?) a TCP/IP connection.

2)
a)
i)Rewrite the app as a client-server system that can handle caching data while the server is offline.
ii) See if any of the SQL server replication (pub-sub) services can help you.

b) You say that a reconnect would be acceptable, in that case i would suggest turning on connection pooling and reconnecting each time. If there are a lot of requests in a short period then a connect request will receive an existing connection from the pool (fast), if not then a full connect will happen (slower).

c) Why not test the connection before you use it ? If bad reconnect. There shouldn't be any reason for the app to crash.

...cmk

Save the whales - collect the whole set

Re: ODBC connection going bad -- what to do?

Robin Hilliard25-Jul-07 13:53

Robin Hilliard

25-Jul-07 13:53

cmk wrote:
c) Why not test the connection before you use it ? If bad reconnect. There shouldn't be any reason for the app to crash.

I've done this in another module for this application, but it's unreliable because (AFAIR) the code which checks if the database handle is alive (it does a "SELECT GETDATE()") generally crashes if the HDBC is dead. Doesn't do it all the time, which is why I've written it this way. Catching 25% of problems is better than catching none at all.

I might try the connection pooling method and see how I get on with that. It's certainly goin to give better results than I've been getting to date.

Thanks for your help

Why does not Command Prompt window have WndProc ?

Ky Nam25-Jul-07 7:04

Ky Nam

25-Jul-07 7:04

Hi I need to subclass Command Prompt window but CP window's WndProc is Zero , therefore i can not call DefWndProc
I do subclassing window using global hook
Thanks for your ideas

Re: Why does not Command Prompt window have WndProc ?

Jonathan [Darka]25-Jul-07 7:08

Jonathan [Darka]

25-Jul-07 7:08

There is no windows message loop for command prompt applications, so no message queue and no routing of messages to a WndProc.

You could use a hidden window though.

What are you trying to do ?

Jonathan Wilkes
Darka[Xanya.net]

Re: Why does not Command Prompt window have WndProc ?

Ky Nam25-Jul-07 15:02

Ky Nam

25-Jul-07 15:02

I mean window of CMD.exe , i think CMD.exe is a window application , it has window handle , window class , ... , an program can use most of window related functions with Command Prompt window
I use global hook to subclass all top-level windows , in their subclassed WndProc i will send useful messages to main program written in .NET , main program will do something such as : adding title button + system menu , managing window . Would you like to try it ?

Video via Positional Data

Andy20225-Jul-07 5:17

Andy202

25-Jul-07 5:17

In a new MFC application, I obtain positional data from an eternal source, but would like to generate a Google Earth type image with this data. Perhaps updated a few times per second.
I have looked at Global Majic ActiveX controls (Digital Map), but are they any others that are out there?

I did think of Microsoft's Flight Simulator, it that an option?

Many thanks,

Andy.

Is there any built in separator control in MFC?

Mushtaque Nizamani25-Jul-07 4:23

Mushtaque Nizamani

25-Jul-07 4:23

Hi,
Is there any built in separator control in MFC?

Best Regards,
Mushq

Mushtaque Ahmed Nizamani
Software Engineer
Ultimus Pakistan

"English is my second language; please excuse any grammatical or spelling mistakes"

Re: Is there any built in separator control in MFC?

Iain Clarke, Warrior Programmer25-Jul-07 4:35

Iain Clarke, Warrior Programmer

25-Jul-07 4:35

pDC->MoveTo (100,0);
pDC->LineTo (100,100);

will draw a line, separating two parts of a DC....?

I feel fairly sure that's not what you are after though. Can you explain your question differently?

If it's for putting a line in a dialog box, I just use a static control, with the sunken flag, and make its width (or height) equal to zero.

Iain.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.