C / C++ / MFC

Multithreading with databases

1-Jun-06 4:25

Have you single-stepped through the code to find which statement is throwing the exception?

"The largest fire starts but with the smallest spark." - David Crow

sergiuem31-May-06 14:02

sergiuem

31-May-06 14:02

I have to write a clinet/server application with sockets and the client use CODBC classes to conect to a local .mdb file and i don't know what to choose for server implementation .
I have tried CDAO clases but DAO doesn't suport multithreading
Please can anyone tell me what I have to use so i can connect to a db engine o server application and be able to use multithreading?
Eg the server thread
UINT ServerThread (LPVOID pParam)
{
threadstruct* ts = (threadstruct*)pParam;

char buffer[BUFFERSIZE];
int size = BUFFERSIZE;
int blabla=0;
cout << "a new client";
while(1)
{

int sz = ts->pSock->Recv(buffer,size,ts->indice);
if(sz == 0)
{
ts->pSock->ServerClose(ts->indice);
delete ts;
return 0;
}
if (sz>3)
{
CMyMessage msg(buffer);

switch(msg.GetMyMsgType())
{

case 0:
cout << endl;
cout << msg.GetMyMsgComm() << " -> " << msg.GetMyMsgText() << endl;
if (!strcmp(msg.GetMyMsgComm(),".SD4P"))
{
CString strComm;
strComm.Format(".SD4P");
CString strText;
strText.Format("return .SD4P");
CMyMessage msg(strText.GetBuffer(strText.GetLength()),strText.GetLength(),strComm.GetBuffer(strComm.GetLength()),strComm.GetLength(),0);
char buffer1[253];
int size1;
msg.GetMyMsg(buffer1,&size1);
ts->pSock->Send(buffer1,size1,ts->indice);

// here i have to implement a db connection to extract some fields and to send the obtained data to client. CArticolSet is a CDAO inheritance and does not work
/*WaitForSingleObject(hMutex1, INFINITE);
CArticolSet* artset = new CArticolSet();
artset->GetDefaultDBName();
artset->GetDefaultSQL();
artset->Open();
artset->Close();
ReleaseMutex(hMutex1);
delete artset;
*/
}

Re: Multithreading with databases

Peter Weyzen31-May-06 15:31

Peter Weyzen

31-May-06 15:31

I've done this very thing -- with ADO

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
<A HREF="http://www.soonr.com">SoonR Inc.</A>

Re: Multithreading with databases [modified]

John M. Drescher31-May-06 16:07

John M. Drescher

31-May-06 16:07

Use ADO or ODBC for multithreaded database access. It is possible (as I have done this in the past) with DAO but why waste time with technology that microsoft has quit developing 5 years ago...

John

-- modified at 22:07 Wednesday 31st May, 2006

Re: Multithreading with databases

David Crow1-Jun-06 4:26

Replace a part of text from text file

1-Jun-06 4:26

Are the client and the server on the same machine?

"The largest fire starts but with the smallest spark." - David Crow

Immunity1831-May-06 14:01

31-May-06 14:01

CString LString;
CString Win = GetWinampPath();
Win.Replace("Winamp.exe","winamp.ini");
AfxMessageBox(Win);
CStdioFile file;
CString Filepath = Win;
const int sz =100;
char buf[sz];

if (file.Open(Filepath,CFile::modeReadWrite|CFile::modeNoTruncate|CFile::modeCreate))
{ // what i have to add here?
file.ReadString(buf,100);
LString = (LPTSTR)buf;
if ( LString == "minimized=0")
{
file.Remove(LString);
file.WriteString("minimized=1");
}
}
file.Close();

_anil_31-May-06 14:27

_anil_

31-May-06 14:27

Hi I am not able to answer as per your question.
From your code it seems that you want to change the settings of INI file.
Then why not to try the functions ?

GetPrivateProfileInt
SetPrivateProfileInt
GetPrivateProfileString
SetPrivateProfileString etc...

Regards
Anil

Immunity1831-May-06 14:46

31-May-06 14:46

oh ?

I got the winamp.ini file:
...
...
...
...
minimized=0 //the part i want to remove
...
...

Files.ini have different act than .txt etc? Big Grin | :-D

_anil_31-May-06 15:00

_anil_

31-May-06 15:00

In that case the above code seams a lot of things missing Unsure | :~

What I think of is that in stead of using CStdioFile you use CFile.
In CFile you can read the whole file into a CString.
Then use CString remove command to remove the part of the string you want to remove.
Then write the string back to the file.

Other method is use a temporary file and read one line and write to temp file, Except the line you want to remove.
Then copy the temp file to .ini file.

Regards
Anil

Immunity1831-May-06 15:08

31-May-06 15:08

thx

David Crow1-Jun-06 4:32

1-Jun-06 4:32

Immunity18 wrote:
file.ReadString(buf,100);

Why use char here? A CString object (e.g., LString) is a much better choice.

If you are changing the contents of a .ini file, why not use the appropriate functions?

GetPrivateProfileString()
WritePrivateProfileString()

"The largest fire starts but with the smallest spark." - David Crow

Immunity181-Jun-06 4:37

Forcing new to fail [modified]

1-Jun-06 4:37

i'll try that Big Grin | :-D

althought its first time i hear about these functions ( i am a (very) bit newbie Big Grin | :-D

hint_5431-May-06 11:30

hint_54

31-May-06 11:30

Hi all =)

Is there a way of forcing the operator new to fail?? I need to test something...

Best regards [[]]

hint_54

-- modified at 18:06 Wednesday 31st May, 2006

Oh.. and one more thing =D

If I overload the operator new then the class constructors will not be called when memory is allocated for them. How do I make it call the constructor?

Peace =)

hint_54

Re: Forcing new to fail

Jörgen Sigvardsson31-May-06 13:43

Jörgen Sigvardsson

31-May-06 13:43

hint_54 wrote:

If I overload the operator new then the class constructors will not be called when memory is allocated for them. How do I make it call the constructor?

Placement new? new (ptr_to_memory) Class(args)

--
100% natural. No superstitious additives.

Stephen Hewitt31-May-06 13:51

Stephen Hewitt

31-May-06 13:51

Overloading the new should not effect whether the constructor is called.

Steve

hint_541-Jun-06 5:27

hint_54

1-Jun-06 5:27

Yes.. It's working now, but it didn't work at first.. Don't know why..

regards

hint_54

David Crow1-Jun-06 4:36

1-Jun-06 4:36

hint_54 wrote:
If I overload the operator new then the class constructors will not be called when memory is allocated for them.

How are you verifying this?

"The largest fire starts but with the smallest spark." - David Crow

Modeless Dialog Disappearing

hint_541-Jun-06 5:25

hint_54

1-Jun-06 5:25

I add a printf to the constructor.

But I don't get it.. it wasn't calling it and now it is! It must have been something else..

regards

hint_54

aei_totten31-May-06 11:00

aei_totten

31-May-06 11:00

I am using this code to create a modeless dialog.

dlg.Create(CMainDialog.IDD, GetDesktopWindow());
dlg.ShowWindow(SW_SHOW);

However, It closes the modeless dialog as soon as it opens. Why is this? I get the debug message "Warning: calling DestroyWindow in CDialog::~CDialog --OnDestroy or PostNcDestroy in derived class will not be called"

Sorry for another stupid question. I swear I will catch on sooner or later.
Hey Maybe it will give you a chance to feel good about being able to answer an easy question, though make me feel even more stupid Smile | :)

-Brandy

Matt Gullett31-May-06 13:51

Matt Gullett

31-May-06 13:51

Are you istantiating the dlg object inside a class method? If so, the problem is that as soon as the method exits, the dlg object gets destructed and your dialog is gone. The dlg object needs to live as long as you want the dialog to be displayed.

aei_totten1-Jun-06 4:18

aei_totten

1-Jun-06 4:18

So where exactly am I suppose to declare it? I have tried placing it in all differnt locations and it says all of them are illegal.

David Crow1-Jun-06 4:39

1-Jun-06 4:39

Try:

CMainDialog *dlg = new CMainDialog;
// put the call to Create() in CMainDialog's constructor
// dlg.Create(CMainDialog.IDD, GetDesktopWindow());
dlg.ShowWindow(SW_SHOW);

When you are done with it, call dlg->DestroyWindow(). Be sure and override PostNcDestroy() and delete the this pointer.

"The largest fire starts but with the smallest spark." - David Crow