C / C++ / MFC

20-Oct-09 17:35

Hi all, I ahve 2 questions.
First:
I would like to know how to convert the text from file into the format below.

In my program,
UINT Test_a(LPVOID lParam)
{
CStdioFile f1(_T("C:/abc/t1.txt"), CFile::modeWrite|CFile::OpenFlags::modeCreate|CFile::shareExclusive);
CString f1_txt;
......
f1_txt.Format("%le %le %le\n", x, y, z);
f1.Write(f1_txt, f1_txt.GetLength());
.....
f1.Close();
}

UINT Test_b(LPVOID lParam)
{
CStdioFile f2;
f2.Open((_T("C:/abc/t1.txt"), CFile::modeRead | CFile::shareExclusive);
CString rdtxt;
//how to read the text from the file t1 and convert it to "%le %le %le\n", &x, &y, &z format?
Can i do something like this?
while(f2.ReadString(rdtxt) != NULL)
{
rdtxt.Format("%le %le %le\n", &x, &y, &z);
....
}
f2.Close();
}

Second:
For CFile.Read. When i put CFile::shareExclusive in my f1.Open, i will have error. The error is
Debug Assertion Failed!
Program: c:\Documents and settings\...\GUi.exe
File:f:\dd\vctools\crt_bld\self_x86\crt\src\fscanf.c
Line:52
Expression:(stream != NULL)

When i change shareExclusive to shareDenyNone or shareDenyWrite, then the program work. How can i solve this? I don't other to open the file when i am running/using the file in my C++ program. The file is quite big, about 8M.

My program code:
text.txt file is created above my program using CStdioFile f2(_T("C:/abc/test.txt), CFile::modeWrite|CFile:shareExclusive);

CStdioFile f1;
CString rd;
CString output;
f1.Open(_T(C:/abc/test.txt"), CFile::modeRead | CFile::shareExclusive);
while(f1.ReadString(rd)!= NULL)
{
output += rd;
output.Format("%lf %lf %lf\n", &a, &b, &c);
.......
.......
}
f1.Close();

Thanks for helping out.

modified on Wednesday, October 21, 2009 1:03 AM

Naveen20-Oct-09 17:55

20-Oct-09 17:55

Nicholas Amh wrote:
//how to read the text from the file t1 and convert it to "%le %le %le\n", &x, &y, &z format?
Can i do something like this?
while(f2.ReadString(rdtxt) != NULL)
{

Ya you can use the _tscanf() function.

_tscanf(rdtxt,_T("%lf %lf %lf\n"), &a, &b, &c));

Nicholas Amh20-Oct-09 19:10

20-Oct-09 19:10

Thanks. That work. But my problem still there. With CFile::shareExclusive and program don't work. Please help me out. Need to get it done asap. Thanks

Randor 20-Oct-09 19:23

Randor

20-Oct-09 19:23

Hi Nicholas,

Did you read the documentation for CFile::shareExclusive[^]? You cannot open the same file in two threads using this mode. It is doing exactly what your asking it to do.

What are you trying to achieve?

Best Wishes,
-David Delaune

Nicholas Amh20-Oct-09 19:44

20-Oct-09 19:44

Hi Randor,

I am trying to prevent other user from opening/accessing my file when my program is using/reading the file. Other user will have no access to my files during my process.
Thanks

Randor 20-Oct-09 21:08

Randor

20-Oct-09 21:08

Hi Nicholas,

You could add a CStdioFile member variable and open the file once. You could then pass the FILE* stream pointer to both threads something like:

if(NULL == m_f.m_pStream)
{
	m_f.Open(_T("C:\\t1.txt"), CFile::modeReadWrite|CFile::OpenFlags::modeCreate|CFile::shareExclusive);
}
AfxBeginThread(Test_a,m_f.m_pStream);
AfxBeginThread(Test_b,m_f.m_pStream);

/*
Your thread uses...
CStdioFile f1((FILE *)lParam);
*/

Using two threads to write to a single file stream is generally not recommended. CFile/CStdioFile are not thread-safe. Also keep in mind that reading/writing moves the file pointer. You will need to keep track of this file pointer and synchronize reads/writes and seek to the appropriate position.

Best Wishes,
-David Delaune

Adam Roderick J20-Oct-09 20:23

Adam Roderick J

20-Oct-09 20:23

I smell, something somehwere gone wrong with the code.
1. what happens if Test_b is reading some data and control goes to Test_a, which write some other data and now there is inconsistency in data when Test_b reads data.
Aviod this condition.
While writing to a file, aviod reading. Sniff | :^)

Величие не Бога может быть недооценена.

Nicholas Amh20-Oct-09 20:59

20-Oct-09 20:59

Okay, thanks. The file that i write have already done writing before going for read.

When is a CWnd ready to receive messages

Richard MacCutchan21-Oct-09 2:33

Richard MacCutchan

21-Oct-09 2:33

Nicholas Amh wrote:
Okay, thanks. The file that i write have already done writing before going for read.

Don't use threads for this unless you understand the implications; the code you have shown suggests you are something of a beginner. The best way of approaching this is to open, write, close the file in the first part of the program, then open, read, close in the second part. Also leave out the sharing part until you have the main logic working. Write the data to the file, use notepad or another editor to check the content is correct. Then read back the file and convert your data to its internal format. Also remember that

Format()

is for output and

scanf()

is for input.

ForNow20-Oct-09 16:14

20-Oct-09 16:14

Hi,

Am I correct in assuming that as soon as CWnd is Created or Intantiated that it is ready to receive messages

via SendMessage

My CWnd actually a Cdialog is waiting for Data I plan to Create or instatiate it

When the data arrives via SendMessage

I plan On Creating it (modlesss flavor)

thankx

Naveen20-Oct-09 18:12

20-Oct-09 18:12

ForNow wrote:
Am I correct in assuming that as soon as CWnd is Created or Intantiated that it is ready to receive messages

Yes.

ForNow wrote:
My CWnd actually a Cdialog is waiting for Data I plan to Create or instatiate it
When the data arrives via SendMessage

If the window is not created how it receive message?

ForNow20-Oct-09 18:19

20-Oct-09 18:19

It is my assumption that as Soon as CWnd/CDialog is inntantiated it has message pump

I dont think you need to Create a Window to receive messages

After All UI CWinthreads don't have windows but are Able to Receive messages though

its Not SendWindow rather PostThreadMessage

What I beleive these Objects have in Common is a Message Pump

thankx

Naveen20-Oct-09 18:29

20-Oct-09 18:29

ForNow wrote:
It is my assumption that as Soon as CWnd/CDialog is inntantiated it has message pump

I dont think you need to Create a Window to receive messages

What do you mean by inntantiated? Creating an object of the class? Simply Creating the object of the class doesnt make any difference in message pumping..

ForNow wrote:
its Not SendWindow rather PostThreadMessage

If the PostThreadMessage() is enough for you, you need to create only the window when the data arrive. But note that, you have to create your own message loop to receive messages that are recevied through PostThreadMessage() function.

ForNow20-Oct-09 18:39

20-Oct-09 18:39

I am just a beginner

but do I Have run ::Create to Receive a message Via ::SendMessge

isn't Having CWnd/CDialog Enough ????

Naveen20-Oct-09 18:43

20-Oct-09 18:43

ForNow wrote:
I am just a beginner

Its been very long you been a beginner... Smile | :)

ForNow wrote:
but do I Have run ::Create to Receive a message Via ::SendMessge

isn't Having CWnd/CDialog Enough ????

Ya you have to create a window. The SendMessage() function needs a window handle and the message will be delivered to that windows procedure. If the window is not created, the handle memeber variable of the Cwnd class will be 0.

ForNow20-Oct-09 18:54

20-Oct-09 18:54

I guess my only other option if I want use ::SendMessage to Receive messages is not to have the WS_VISIBLE flag on

and Do A ShowWindow When I receive the Data

I do MFC only a night durning the day I am MainFrame Programmer

Unlike others on the forum who work at this

Thankx for your help ..

Hans Dietrich20-Oct-09 21:59

Hans Dietrich

20-Oct-09 21:59

No problem, everyone here has been where you are.

You might want to take a look at the books by Petzold (Windows) and Prosise (MFC) for further explanations.

Best wishes,
Hans

[Hans Dietrich Software]

ForNow21-Oct-09 14:42

21-Oct-09 14:42

The Petzold Book "Programming Windows" gave me a Good Idea of Windows GDI ...Device Context

Then Bjarne Stroustrup C++ programing Language in Particular Chapters 10,12,15

That all Leads to Windows MFC

thankx for the encourgement