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Hallo, i have the following function in SDI-application:
void CMyClass::Myfunction()
{
CString strOutput;
LPMSG *pmsg = NULL;
for(int i = 0; i < 3000; i++)
{
::PeekMessage(NULL,NULL,0,0,PM_NOYIELD | PM_REMOVE);
strOutput.Format ("%d",i);
m_ptrOutput->SetWindowTextA (strOutput);
}
}
as you see the for-loop goes 3000 times and should print the value of i, what happens when this function starts
is the appliction FREEZ. I do not have any idea why this happens and how to solve this problem.Please help.
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What is that magic number 3000?
Why do you want to loop 3000 times?
«_Superman_»
I love work. It gives me something to do between weekends.
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loop 3000 to get the rows from a database :
select * from DB;
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susanne1 wrote: LPMSG *pmsg = NULL;
What is the purpose of this pointer variable? You aren't using it anywhere in your code. Not to mention LPMSG is already a pointer to a MSG structure. 
void Func()
{
CString szOutput;
MSG msg;
for(int i=0; i<3000; i++)
{
PeekMessage(&msg, NULL, 0, 0, PM_REMOVE);
szOutput.Format(_T("%d"), i);
OutputDebugString(szOutput);
}
Why would you do something like this? Are you trying to understand how PeekMessage works or ... ?
It is a crappy thing, but it's life -^ Carlo Pallini
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i must do it because i have over 40000 rows in the database(wher can i find a tutorial that explain how peekmessgae works??)
do not i need to intialize the msg before i use it?
i used the PeekMessage(&msg, NULL, 0, 0, PM_REMOVE);in the loop that retrives the rows but nothing changed positively??
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You actually are in need of a good book. For book recommendations, see here[^].
Here[^] is a good tutorial on threading. But, that can hardly help you if you don't get a good grip of the basics at first.
It is a crappy thing, but it's life -^ Carlo Pallini
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okay thanks but for now how can i solve this problem?
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You cannot solve this problem until you understand the basics. If I start to tell why you should not use PeekMessage there, I'll have to explain what a worker thread is, thread synchronization, applying everything together in your program, etc., Too much of stuff to be discussed in a thread like this. You are desperately in need of a book and go buy one or two. Your program can wait until you're good enough to solve it.
And no pal, I do not feel like providing you a quick-fix. Sorry about that.
It is a crappy thing, but it's life -^ Carlo Pallini
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You should sometimes (e.g. after reading of 100 data) call a function like this.
If you remove the message from the queue, you should dispatch the message. You can call PeekMessage with other filters too (e.g. for a special window or other messages). But the last call should not use any filters!
void PeekMessages()
{
MSG msg;
// check for paint-messages ...
while ( PeekMessage(&msg, NULL, WM_PAINT, WM_PAINT, PM_REMOVE) )
{ // ... and dispatch these
TranslateMessage(&msg);
DispatchMessage(&msg);
}
// only to prevent ghost-window on vista!
// we dont use the result and let the message
// in the queue (PM_NOREMOVE)
PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE);
}
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Hallo,
I need to start a timer like the following to measure the time that my appliction requires to do someting:
void CMiniClass :: DoSomething()
{
theApp.m_pMainWnd ->SetTimer (MY_TIMER,1000,NULL);
while (i > 0)
{
DoStuff();
}
//theApp.m_pMainWnd ->KillTimer (MY_TIMER);
}
in the CMainFrame.cpp i overrode the OnTimer() from the baseclass:
void CMainFrame::OnTimer(UINT nIDEvent)
{
m_bFlagStartTimer = true;
CFrameWnd::OnTimer(nIDEvent);
CString strTimer(_T(""));
m_nSeconds++;
if(m_nSeconds == 60)
{
m_nMinutes++;
m_nSeconds = 0;
}
if(m_nMinutes == 60)
{
m_nHours++;
m_nMinutes = 0;
}
if(m_nHours == 24)
{
m_nHours = 0;
}
strTimer.Format("%d:%d:%d", m_nHours, m_nMinutes, m_nSeconds);
MessageBox(strTimer,0,0);
}
the problem is the application starts the Timer(in the Messagebox) after he finished the while-loop,so i can not know how long
my appliction was BUSY with this loop, and if i activate theApp.m_pMainWnd ->KillTimer (MY_TIMER);
the Timer would be KILLED and then the while-llop starts, i need to do this without using Thread.
Please help to fix this problem. Thanks.
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You shouldn't be using a timer here.
You should ideally get the time first, start your job, get the time again after you're job completes and then compare the first and second time.
«_Superman_»
I love work. It gives me something to do between weekends.
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i used this code but the problem it starts first when the appliction has finished the job.
CFrameWnd::OnTimer(nIDEvent);
CTime timer;
CString strTimer (_T(""));
timer = CTime::GetCurrentTime ();
if(((m_nSeconds = timer.GetSecond ()) == 0) && (m_bFlagTimer == true))
{
m_nMinutes++;
}
if(((timer.GetMinute ()) == 0) && (m_bFlagTimer == true))
{
m_nHours++;
}
wsprintf((LPTSTR)strTimer.GetString (),"%02i:%02i:%02i",m_nHours, m_nMinutes, m_nSeconds);
m_wndStatusBar.SetPaneText(5,LPCSTR(strTimer.GetString ()),true
i need to count parallel to the task when it runs.
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susanne1 wrote: I need to start a timer like the following to measure the time that my appliction requires to do someting
You're using the wrong sort of timer - the windows timer sends one of your windows a WM_TIMER message when the time you wanted has expired.
You imply you want to measure how long something took to run. They way to do that is to find the time when the activity starts, the time when it ends and determine the difference between them. I generally use the high-resolution counter[^] for that.
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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i used this code but the problem it starts first when the appliction has finished the job.
CFrameWnd::OnTimer(nIDEvent);
CTime timer;
CString strTimer (_T(""));
timer = CTime::GetCurrentTime ();
if(((m_nSeconds = timer.GetSecond ()) == 0) && (m_bFlagTimer == true))
{
m_nMinutes++;
}
if(((timer.GetMinute ()) == 0) && (m_bFlagTimer == true))
{
m_nHours++;
}
wsprintf((LPTSTR)strTimer.GetString (),"%02i:%02i:%02i",m_nHours, m_nMinutes, m_nSeconds);
m_wndStatusBar.SetPaneText(5,LPCSTR(strTimer.GetString ()),true
i need to count parallel to the task when it runs.
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There is no point reposting the same code. there was an answer given by somebody. try that out. if you get stuck as again. you will get assistance
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What you want to do is something like this (using code from you original post):
void CMiniClass :: DoSomething()
{
LARGE_INTEGER startTime, endTime;
QueryPerformanceCounter(&startTime);
while (i > 0)
{
DoStuff();
}
QueryPerformanceCounter(&endTime);
LARGE_INTEGER elapsedTime;
elapsedTime.QuadPart = endTime.QuadPart - startTime.QuadPart;
LARGE_INTEGER timerFreq;
QueryPerformanceFrequency(&timerFreq);
const double elapsedTimeInSeconds = (double)elapsedTime.QuadPart / (double)timerFreq.QuadPart;
}
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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hello all ,
I am writing student info on file by following way..
Struct Student
{
int Marks;
int RollNo;
};
Student Sobj;
int main()
{
//then i create file using ,CreateFile( ....);
//I store data for 10 student
for(int i=0;i<10;i++)
{
Sobj.Marks=10*i;
Sobj.RollNo=i;
WriteFile ( HandleFile , &sobj , sizeof ( struct Student ) ,...,...);
}
CloseHandle( ..) ;
}
--------------------------
This code work proper .
Then I read that data using ReadFile(Handle,&sobj,....) it also work
-----------------------------------
Now My problem is I am reading that file on some condition i want to change data of students eg. for roll no 3 marks 80;
how should i do this .
means i am reading and on some condition i have to Use WrteFile()
i try using SetFilePointer But i was not able to do that ,,how to go back in file.
Thanks All
Ashish P.
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ashish8patil wrote: means i am reading and on some condition i have to Use WrteFile()
i try using SetFilePointer But i was not able to do that ,,how to go back in file.
Don't do this. A much better (and probably easier) way is to write the full file once again. The problem is that when writing you are not able to insert new characters. Which means that if your entry was 9 (1 character) before and has to be overwritten by 10 (2 characters), this is not possible.
So, when open the file for reading, specifying that the contents should be cleared and then write your full structure again.
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Thanks for your reply
I just give you student as example ,but my data is very large and it may be very long way ,store that data in buffer n all..
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SetFilePointer is the correct way to do it.
Before that you must open the file as GENERIC_READ|GENERIC_WRITE since you want to do both.
Each record in your case will take up sizeof(Student) bytes.
So it is just a matter of multiplication to find the offset of the record to modify.
So do a SetFilePointer to that offset with move method as FILE_BEGIN.
Then do a WriteFile with the new record.
«_Superman_»
I love work. It gives me something to do between weekends.
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i also try to do same but it was not write there plz see code
ServerHandle = CreateFile ( L"server.dat" ,
GENERIC_READ | GENERIC_WRITE ,
FILE_SHARE_WRITE ,
NULL ,
OPEN_EXISTING ,
0 ,
NULL ) ;
if ( ServerHandle == INVALID_HANDLE_VALUE )
{
return ( 1 ) ;
}
ReadFile ( ServerHandle , & finfo , sizeof ( struct ServerFileInfo ) , &BytesRead , NULL ) ;
FilePointer.QuadPart =-sizeof(UpdateInfoOnServer);
for (i=0;i<finfo.NoUpdates ;i++)
{
ReadFile ( ServerHandle , & UpdateInfo , sizeof ( struct UpdateInfoOnServer ) , &BytesRead , NULL ) ;
if((UpdateInfo.IsApproved==1)&&(UpdateInfo.IsDownloaded==0) )
{
for(j=0;j<UpdateInfo.NumberOfPatches ;j++)
{
PatchFileID=UpdateInfo.PatchFileID[j] ;
iTmp=DownloadByPatchFileID();
if(iTmp==1)
{
return 1;
}
}
UpdateInfo.IsDownloaded=1;
SetFilePointerEx ( ServerHandle , FilePointer, NULL , FILE_CURRENT ) ;
WriteFile ( ServerHandle , & UpdateInfo , sizeof ( struct UpdateInfoOnServer ) , &BytesWritten , NULL ) ;
}
}
/////////////////////////////////////////////
where i make mistake..plz tell
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You should be using your debugger here.
Set a breakpoint and single step through the code.
You'll surely catch the error.
And also you need to check return values of those APIs that you're calling.
«_Superman_»
I love work. It gives me something to do between weekends.
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but logically are this things correct?
LARGE_INTEGER FilePointer ;
FilePointer.QuadPart =-sizeof(UpdateInfoOnServer);
SetFilePointerEx ( ServerHandle , FilePointer, NULL , FILE_CURRENT ) ;
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as Cedrice said, unless you are going to have many people modifying the data at once; in which case you should store all the data in a database, and not worry about files at all.
Luc Pattyn [Forum Guidelines] [My Articles]
DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.
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ashish8patil wrote: SetFilePointer
That sounds about right. Maybe you can tell us why you weren't able to use that? Because the following program, based on your (syntactically incorrect) code fragments, compiles and runs successfully. Here's a hint - check function returns values and GetLastError[^].
#include <Windows.h>
struct Student
{
int Marks;
int RollNo;
};
struct Student sobj;
int main()
{
HANDLE hFile = CreateFile("a.a", GENERIC_READ|GENERIC_WRITE, 0, 0, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);
for(int i=0;i<10;i++)
{
sobj.Marks=10*i;
sobj.RollNo=i;
DWORD written;
WriteFile ( hFile , &sobj , sizeof ( sobj ) , &written, 0);
}
int i = 3;
sobj.Marks=5*i;
sobj.RollNo=i;
SetFilePointer(hFile, sizeof(sobj)*i, 0, FILE_BEGIN);
DWORD written;
WriteFile ( hFile , &sobj , sizeof ( sobj ) , &written, 0);
CloseHandle(hFile) ;
}
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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