Re: Read a file on click event - C / C++ / MFC Discussion Boards

Re: Read a file on click event

CodingLover16-Oct-07 1:46

CodingLover

16-Oct-07 1:46

I think it is possible using CFile::GetLength(). Wait, I'll test it now.

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

chandu00416-Oct-07 2:05

chandu004

16-Oct-07 2:05

did u get it?
hope so.

Re: Read a file on click event

chandu00415-Oct-07 21:15

chandu004

15-Oct-07 21:15

forward me your application i shall see it.

Re: Read a file on click event

CodingLover15-Oct-07 21:22

CodingLover

15-Oct-07 21:22

Sure.

But how can I attach them. I can't see your mail address. If I past on the mail-body here in the forum it can be a real mess.

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen15-Oct-07 21:12

Naveen

15-Oct-07 21:12

Eranga Thennakoon wrote:
void CSRFToolDlg::OnBnClickedRead()
{
char tempBuffer[256] ;

I think _UNICODE is defined your project so you are writing some wchar and trying to read some multi byte cahracters. try changing the following way

void CSRFToolDlg::OnBnClickedRead()<br />
{<br />
TCHAR tempBuffer[256] ;<br />
UINT readText = 0;<br />
readText = openFile.Read(tempBuffer, 256 ) ;<br />
SetDlgItemText(IDC_S_READ, readText) ;<br />
}

nave

[OpenedFileFinder]

Re: Read a file on click event

CodingLover15-Oct-07 21:18

CodingLover

15-Oct-07 21:18

I think the issue is on UINT. Is says that cannot convert parameters of SetDlgItemText() from 'UINT' to 'LPCTSTR'

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen15-Oct-07 21:27

Naveen

15-Oct-07 21:27

I just noticed you are trying to set the number of bytes returned by the read() function. If you want to set the read text change the readText with tempBuffer.

SetDlgItemText(IDC_S_READ, tempBuffer) ;

nave

[OpenedFileFinder]

Re: Read a file on click event

CodingLover15-Oct-07 21:33

CodingLover

15-Oct-07 21:33

I want to print the text which is write to the file. No need to find the number of bytes. Initially I've tried this one also. What happened is print some annoying text on the edit control. It is true, because the buffer is size of 256 which I've defined.

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen15-Oct-07 22:50

Naveen

15-Oct-07 22:50

did u try after changing the char tempBuffer to TCHAR tempBuffer?

nave

[OpenedFileFinder]

Re: Read a file on click event

CodingLover15-Oct-07 22:55

CodingLover

15-Oct-07 22:55

Yes I've tried it.

<br />
UINT readText = 0;<br />
readText = openFile.Read(tempBuffer, strlen(tempBuffer)) ;<br />

It's gives the error on above code. Gives an error on UINT and LPCTSTR. But I can't find any such conversions.

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen15-Oct-07 22:59

Naveen

15-Oct-07 22:59

Eranga Thennakoon wrote:
UINT readText = 0;
readText = openFile.Read(tempBuffer, strlen(tempBuffer)) ;

This is not the code I suggested you earlier

void CSRFToolDlg::OnBnClickedRead()
{
TCHAR tempBuffer[256] ;
UINT readText = 0;
readText = openFile.Read(tempBuffer, 256 ) ;
SetDlgItemText(IDC_S_READ, tempBuffer ) ;
}

The readtext is having the number og bytes read by the read function. And you are trying to set that UINT value to the edit box???? the tempBuffer containes the data actaully read from the file.

nave

[OpenedFileFinder]

Re: Read a file on click event

CodingLover15-Oct-07 23:05

CodingLover

15-Oct-07 23:05

No dear, I'm talking about the same code as you say. I check all your suggestions, as I said earlier post it print some annoying characters except the text on the file. Until it fill-up 256 characters.

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen15-Oct-07 23:08

Naveen

15-Oct-07 23:08

Eranga Thennakoon wrote:
it print some annoying characters except the text on the file

ok. that makes sense.

Now can you read the text in the file you open it in notepad?

nave

[OpenedFileFinder]

Re: Read a file on click event

CodingLover15-Oct-07 23:13

CodingLover

15-Oct-07 23:13

I think you are still not clear on my question. can write anything to a file. But I can't read it still. When I click the read button, by using your above suggestion, it print some annoying(bunch of slashes actually) characters, except the string(letters) on the file. Frown | :(

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen15-Oct-07 23:20

Naveen

15-Oct-07 23:20

Eranga Thennakoon wrote:
it print some annoying(bunch of slashes actually) characters

Ok. But i just want to ensure that your writing to file is proper. thats why i asked whether you can read the file in the notepad.

Also by the time try setting the tempBuffer as follows. This will set the intial content of the array to 0.
TCHAR tempBuffer[256] = {0};

nave

[OpenedFileFinder]

Re: Read a file on click event

CodingLover15-Oct-07 23:28

CodingLover

15-Oct-07 23:28

Oops, you asking that I can read the text file on my naked eyes. Sure I can, that mean my application write text properly.

At the time you know what is the funny thing. When I use an empty buffer, nothing print on the edit control.

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen15-Oct-07 23:33

Naveen

15-Oct-07 23:33

ok i think i got the problem. Update the function by calling the SeekToBegin() as follows

void CSRFToolDlg::OnBnClickedRead()<br />
{<br />
TCHAR tempBuffer[256] ;<br />
UINT readText = 0;<br />
openFile.SeekToBegin();<br />
readText = openFile.Read(tempBuffer, 256 ) ;<br />
SetDlgItemText(IDC_S_READ, tempBuffer ) ;<br />
}

nave

[OpenedFileFinder]

Re: Read a file on click event

CodingLover16-Oct-07 0:46

CodingLover

16-Oct-07 0:46

Seems this is working fine. But one issue is there, if the string length is more than 256 characters. Can I set it to the length of the string which I've already written in the file.

Thanks

I appreciate your help all the time...
Eranga Smile | :)

Re: Read a file on click event

Naveen16-Oct-07 3:32

Naveen

16-Oct-07 3:32

ya... Either you can read the full text in one read( this will not be possible is the file is too big. because memeory allocation will fail for big length of data ) or read the text in a loop.

// For reading the complete text in single read

void CSRFToolDlg::OnBnClickedRead()<br />
{<br />
<br />
ULONGLONG nLength = openFile.GetLength();// returns the current size of the file<br />
TCHAR* ptempBuffer = new TCHAR[nLength];<br />
UINT readText = 0;<br />
openFile.SeekToBegin();<br />
readText = openFile.Read(tempBuffer, 256 ) ;<br />
SetDlgItemText(IDC_S_READ, ptempBuffer ) ;<br />
delete[] ptempBuffer;<br />
}

nave

[OpenedFileFinder]

Re: Read a file on click event

chandu00416-Oct-07 1:36

chandu004

16-Oct-07 1:36

it seems that, naveen has entered the board means, the problem is solved.
good.

Re: Read a file on click event

Naveen16-Oct-07 3:35

Naveen

16-Oct-07 3:35

chandu004 wrote:
it seems that, naveen has entered the board means, the problem is solved.

Thanks for the comment. But its not working always Big Grin | :-D

nave

[OpenedFileFinder]

Re: Read a file on click event

chandu00416-Oct-07 4:12

chandu004

16-Oct-07 4:12

but i like the way you tackle the problems.
really i appreciate you.
where are you locally from.
ap?
hyderabad?

Re: Read a file on click event

Naveen16-Oct-07 5:12

Naveen

16-Oct-07 5:12

No I am from kerala. But currently in Japan. Where r u from?

nave

[OpenedFileFinder]

Re: Read a file on click event

chandu00416-Oct-07 20:49

chandu004

16-Oct-07 20:49

iam in hyderabad and working here since 2004.
my platform is vc++ 6.0,
and embedded software development in c.
these days, i have worked in communications and only communications.

Re: Read a file on click event

Roger Broomfield15-Oct-07 21:36

Roger Broomfield

15-Oct-07 21:36

In My Humble Opinion your basic understanding of Read() is incorrect. Read() will always read the number of characters given by the second argument or the total number of characters in the file, whichever is the smaller. What you really want is to do something like this.

CStdioFile fileOpen;
OnBnClickedOpen() can stay the same

void CSRFToolDlg::OnBnClickedWrite()
{ 
GetDlgItemText(IDC_S_WRITE, readString) ;
// ensure the string is terminated with a newline
// so that ReadString will know when to stop reading
if (readString.Right(1) != _T("\n"))
    readString += _T("\n");
AfxMessageBox("Data write to the file successfully", MB_OK) ;
openFile.WriteString(readString) ;
}

void CSRFToolDlg::OnBnClickedRead()
{
CString readText;
openFile.ReadString(readText) ;
// the trailing newline character that we appended before the WriteString
// is always removed by ReadString
SetDlgItemText(IDC_S_READ, readText) ;
}

Ohh and there is another potential problem, if you click Open, Write, Read then the result will not be what you expect because the OnBnClickedRead is not returning the filepointer to the start of the file

openFile.SeekToBegin();

you may also nead to call openFile.Flush() to ensure that buffers are flushed to disk before seeking to the begining of the file.

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