ReadFile function returns 1 but number of bytes read is returning 0 - C / C++ / MFC Discussion Boards

Richard MacCutchan9-Jun-10 2:32

9-Jun-10 2:32

I have to say your answer is one of the most informative and useful I have seen for a long time. I've learned two new patterns and got some suggestions for further reading.

It's time for a new signature.

handle of parent window containing windowless content

rakesh54548-Jun-10 21:20

rakesh5454

8-Jun-10 21:20

Dear All,

I want to find the handle of parent window containing windowless content. Example of web page containing windowless content is http://www.metacafe.com. On this site video files is getting played in windowless mode i.e. the player is not a window but just an content embedded in some other window (host/parent window). I want to determine handle of this parent window. contrary to this on youtube, the area on which video runs, is in itself a window.

Using spy++, I can determine the hierarchy of window in the IE window and If i will follow this hierarchy I can reach to the host/parent window on metacafe. But I believe it would only be applicable to metacafe. There must be some site which will host windowless content in different windows hierarchy.

So, please let me know if anyone knows how to get window handle of parent/host window containing/hosting windowless content.

Regards

truncating file size using _chsize in C

Nikesh Jagtap8-Jun-10 21:12

Nikesh Jagtap

8-Jun-10 21:12

For trancating file size using:
int _chsize( int fd, long size);
require to provide parameter "int fd" i.e. file descriptor.
How to provide file descriptor?

Re: truncating file size using _chsize in C

Cedric Moonen8-Jun-10 21:54

Cedric Moonen

8-Jun-10 21:54

What's wrong with the previous replies ? Are you too lazy to follow a link and read some documentation ?

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Truncating size of file using _chsize()

Nikesh Jagtap8-Jun-10 20:40

Nikesh Jagtap

8-Jun-10 20:40

For trancating file size using:
int _chsize( int fd, long size);
require to provide parameter "int fd" i.e. file descriptor.
How to provide file descriptor?

Re: Truncating size of file using _chsize()

Cedric Moonen8-Jun-10 20:41

Cedric Moonen

8-Jun-10 20:41

There's a complete example in the documentation[^]

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Re: Truncating size of file using _chsize()

«_Superman_»8-Jun-10 20:48

«_Superman_»

8-Jun-10 20:48

If you have a handle to a file, you can do the same using the SetFilePointer and SetEndOfFile APIs.

«_Superman_»

I love work. It gives me something to do between weekends.

Microsoft MVP (Visual C++)

Polymorphism in C

ReadFile function returns 1 but number of bytes read is returning 0

learningvisualc8-Jun-10 20:35

learningvisualc

8-Jun-10 20:35

Hi all,

I am trying to read a serial port using this code

DCB dcb;
	HANDLE hCom;
	BOOL fSuccess;
	char *pcCommPort = "COM6";
	COMMTIMEOUTS cto;
	
	hCom = CreateFile(pcCommPort,
                    GENERIC_READ | GENERIC_WRITE,
                    0,    // must be opened with exclusive-access
                    NULL, // no security attributes
                    OPEN_EXISTING, // must use OPEN_EXISTING
                    0,    // not overlapped I/O
                    NULL  // hTemplate must be NULL for comm devices
                    );
	
	if (hCom == INVALID_HANDLE_VALUE) 
	{
		// Handle the error.
		AfxMessageBox("CreateFile failed with error %d.\n");
		// return (1);
	}
	
	fSuccess = GetCommState(hCom, &dcb);
	
	dcb.BaudRate = CBR_19200;     // set the baud rate
	dcb.ByteSize = 8;             // data size, xmit, and rcv
	dcb.Parity = NOPARITY;        // no parity bit
	dcb.StopBits = ONESTOPBIT;    // one stop bit
	
	fSuccess = SetCommState(hCom, &dcb);
	if (!fSuccess) 
	{
		// Handle the error.
		AfxMessageBox("SetCommState failed with error %d.\n");
		// return (3);
	}
int n = ReadFile(hCom, buff, 128, &readed, 0);

my problem is ReadFile is returning 1 but in bytes read field its returning 0.

Is there anythingthat i am missing

Re: ReadFile function returns 1 but number of bytes read is returning 0

Cedric Moonen8-Jun-10 20:40

Cedric Moonen

8-Jun-10 20:40

You didn't set the communication time-out. It is possible that you don't receive any data but the communication times-out without having read anything. Use the SetCommTimeouts in order to specify appropriate timeout values.

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Tab control

john56328-Jun-10 19:53

john5632

8-Jun-10 19:53

Hi,

I want complete new look and feel with tab control as I desinged. So I want to place my own formatted text along with image on tab control.

How can I do this?
Please suggest any link to do...

Re: Tab control

Niklas L8-Jun-10 23:16

Niklas L

8-Jun-10 23:16

Have a look how this TabCtrl[^] is done.

home

Reg Excel Automation in SDI

hellogany8-Jun-10 19:22

hellogany

8-Jun-10 19:22

Hi

I am using SDI in windows explorer style.

The right view contains a formview and left view consits of treeview.

In formview i m tryin to transfer the list control data to Excel sheet.

Im using excel automation ...

But its throwing run time error.

Can Anyone Help me...

Re: Reg Excel Automation in SDI

«_Superman_»8-Jun-10 19:28

«_Superman_»

8-Jun-10 19:28

You need to give more information.
What is the error message and when this happens.
Try to debug the application.

«_Superman_»

I love work. It gives me something to do between weekends.

Microsoft MVP (Visual C++)

Polymorphism in C

Re: Reg Excel Automation in SDI

hellogany9-Jun-10 0:23

hellogany

9-Jun-10 0:23

I m gettin type redefinition error,

Problem while using excel.h and excel.cpp file.

MoreOver These two files are not generated automatically, i used in VC6 and get that files and copied these files to my current project in vs2005.

The file supports in dialog based projects but not in SDI

Regards
Gany

Failure in SendMessage in Retail Verrsion only, has me baffled.

Bram van Kampen8-Jun-10 14:16

Bram van Kampen

8-Jun-10 14:16

Hi,

I am using the following code for years without any complaints. It is used by me in many apps, and included in libs, too many to count.
Always worked a dream.

It concerns an MFC Type CProgressDlg Base Class. A User would derrive his own class thereof, Set a Workerthread function, and the thing takes off as expected.

Here is the Header

<br />
#if !defined(AFX_PROGRESSDLG_H__07E71F2A_E348_47C9_B150_F02855B96859__INCLUDED_)<br />
#define AFX_PROGRESSDLG_H__07E71F2A_E348_47C9_B150_F02855B96859__INCLUDED_<br />
<br />
#if _MSC_VER >= 1000<br />
#pragma once<br />
#endif // _MSC_VER >= 1000<br />
// ProgressDlg.h : header file<br />
//<br />
<br />
enum{	<br />
	WM_ENDDIALOG=WM_USER+1,<br />
	WM_UPDATE_DATA,<br />
	WM_SHOULD_TERMINATE,<br />
};<br />
<br />
<br />
class CProgressDlg;<br />
typedef DWORD (CProgressDlg::*PFN_PROGRESS_DLG_THREADPROC)(void);<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
<br />
// Advance Declaration of the Thread Proc that calls the Worker Function<br />
// We need to make it a friend, so that it has access to the Private Members<br />
static int (ProgressDlgThread)(void*);<br />
<br />
<br />
////////////////////////////////////////////<br />
// CProgressDlg dialog<br />
class CProgressDlg : public CDialog<br />
{<br />
	friend ProgressDlgThread(void*);<br />
<br />
	DECLARE_DYNAMIC( CProgressDlg )<br />
<br />
public:<br />
	DWORD GetThreadResult();<br />
	PFN_PROGRESS_DLG_THREADPROC SetWorkerThreadProcedure(PFN_PROGRESS_DLG_THREADPROC pFn);<br />
	void EndDialog(int ExitCode);<br />
	BOOL ShouldTerminate(DWORD* pdwReason=NULL);<br />
	CProgressDlg(UINT nIDTemplate,CWnd* pParent =NULL);   <br />
<br />
protected:<br />
	CRITICAL_SECTION m_cs;<br />
	virtual void DoDataExchange(CDataExchange* pDX);    <br />
	virtual BOOL UpdateData(BOOL bSaveAndValidate = TRUE);<br />
	virtual void OnOK();<br />
	virtual void OnCancel();<br />
	virtual BOOL OnInitDialog();<br />
<br />
	DECLARE_MESSAGE_MAP()<br />
private:<br />
	// Private Implementation Functions<br />
	// If you compile this into a DLL, just remove the following:<br />
	// two lines in the Public DLL Header<br />
<br />
	void _OnEndDialog(int ExitCode);<br />
	void _OnUpdateData(BOOL bSaveAndValidate,BOOL*pbRes);<br />
	// Private Implementation Data<br />
	// If you compile this into a DLL, replace the following section with:<br />
	// DWORD Reserved[5] in the Public DLL Header<br />
	PFN_PROGRESS_DLG_THREADPROC m_pFnThreadProc;<br />
	BOOL m_bShouldTerminate;<br />
	int m_nDlgStatus;<br />
	DWORD m_dwDlgResult;<br />
	DWORD m_dwThreadResult;<br />
	CWinThread* m_pWinThread;<br />
<br />
<br />
<br />
};<br />
<br />
<br />
#endif // !defined(AFX_PROGRESSDLG_H__07E71F2A_E348_47C9_B150_F02855B96859__INCLUDED_)<br />

and Implementation.

<br />
// ProgressDlg.cpp : implementation file<br />
//<br />
<br />
#include "stdafx.h"<br />
#include "ProgressDlg.h"<br />
<br />
#ifdef _DEBUG<br />
#define new DEBUG_NEW<br />
#undef THIS_FILE<br />
static char THIS_FILE[] = __FILE__;<br />
#endif<br />
<br />
<br />
enum{<br />
	THREADSTATE_NOT_STARTED=0,<br />
	THREADSTATE_RUNNING,<br />
	THREADSTATE_COMPLETED,<br />
}; <br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CProgressDlg dialog<br />
IMPLEMENT_DYNAMIC( CProgressDlg, CDialog )<br />
<br />
CProgressDlg::CProgressDlg(UINT nIDTemplate,CWnd* pParent /*=NULL*/)<br />
	: CDialog(nIDTemplate, pParent)<br />
{<br />
<br />
	//{{AFX_DATA_INIT(CProgressDlg)<br />
		// NOTE: the ClassWizard will add member initialization here<br />
	//}}AFX_DATA_INIT<br />
	InitializeCriticalSection(&m_cs);<br />
<br />
	m_pFnThreadProc=NULL;<br />
	m_nDlgStatus=THREADSTATE_NOT_STARTED;<br />
	m_dwDlgResult=IDOK;<br />
	m_dwThreadResult=0;<br />
	m_bShouldTerminate=0;<br />
	m_pWinThread=NULL;<br />
<br />
}<br />
<br />
<br />
void CProgressDlg::DoDataExchange(CDataExchange* pDX)<br />
{<br />
	EnterCriticalSection(&m_cs);<br />
	CDialog::DoDataExchange(pDX);<br />
	LeaveCriticalSection(&m_cs);<br />
<br />
	//{{AFX_DATA_MAP(CProgressDlg)<br />
		// NOTE: the ClassWizard will add DDX and DDV calls here<br />
	//}}AFX_DATA_MAP<br />
}<br />
<br />
<br />
BEGIN_MESSAGE_MAP(CProgressDlg, CDialog)<br />
	//{{AFX_MSG_MAP(CProgressDlg)<br />
	ON_MESSAGE(WM_ENDDIALOG,_OnEndDialog)<br />
	ON_MESSAGE(WM_UPDATE_DATA,_OnUpdateData)<br />
	//}}AFX_MSG_MAP<br />
END_MESSAGE_MAP()<br />
<br />
<br />
<br />
//////////////////////////////////////////////////<br />
// This function runs as a Seperate Worker Thread<br />
static int ProgressDlgThread(void* P){<br />
<br />
	ASSERT(P);<br />
	CProgressDlg* pDlg=(CProgressDlg*)P;<br />
	ASSERT(pDlg->IsKindOf(RUNTIME_CLASS(CProgressDlg)));<br />
<br />
	ASSERT(pDlg->m_pFnThreadProc);<br />
	pDlg->m_nDlgStatus=THREADSTATE_RUNNING;<br />
<br />
	//Fire the User Callback<br />
	pDlg->m_dwThreadResult=(pDlg->*pDlg->m_pFnThreadProc)();<br />
<br />
	// Done<br />
	pDlg->m_nDlgStatus=THREADSTATE_COMPLETED;<br />
	pDlg->EndDialog(pDlg->m_dwDlgResult);<br />
	return 0;<br />
<br />
<br />
}<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CProgressDlg message handlers<br />
<br />
BOOL CProgressDlg::OnInitDialog() <br />
{<br />
	CDialog::OnInitDialog();<br />
<br />
	ASSERT(m_pFnThreadProc);<br />
	m_dwDlgResult=IDOK;<br />
<br />
	m_pWinThread=AfxBeginThread((AFX_THREADPROC)ProgressDlgThread,this);<br />
	<br />
	return TRUE;  // return TRUE unless you set the focus to a control<br />
	              // EXCEPTION: OCX Property Pages should return FALSE<br />
}<br />
<br />
// Function to be Called by Workerthread ONLY<br />
// to See if the Workerthread ShouldTerminate <br />
//<br />
// bShouldTerminate can ONLY be set by EndDialog(nResult)<br />
// m_dwDlgResult is <br />
BOOL CProgressDlg::ShouldTerminate(DWORD* pdwReason)<br />
{<br />
	BOOL bShouldTerminate;<br />
<br />
	EnterCriticalSection(&m_cs);<br />
		if(pdwReason)*pdwReason=m_dwDlgResult;<br />
		bShouldTerminate=m_bShouldTerminate;<br />
	LeaveCriticalSection(&m_cs);<br />
<br />
	return bShouldTerminate;<br />
}<br />
<br />
<br />
void CProgressDlg::OnCancel()<br />
{<br />
	EndDialog(IDCANCEL);<br />
}<br />
<br />
void CProgressDlg::OnOK()<br />
{<br />
	UpdateData();<br />
	EndDialog(IDOK);<br />
}<br />
BOOL CProgressDlg::UpdateData(BOOL bSaveAndValidate)<br />
{<br />
	ASSERT(m_hWnd);<br />
	BOOL bRes=TRUE;<br />
	::SendMessage(m_hWnd,WM_UPDATE_DATA,bSaveAndValidate,(DWORD)&bRes);<br />
	return bRes;<br />
}<br />
<br />
void CProgressDlg::_OnUpdateData(BOOL bSaveAndValidate,BOOL* pbRes)<br />
{<br />
	BOOL bRes=CDialog::UpdateData(bSaveAndValidate);<br />
	if(pbRes)*pbRes=bRes;<br />
}<br />
<br />
PFN_PROGRESS_DLG_THREADPROC CProgressDlg::SetWorkerThreadProcedure(PFN_PROGRESS_DLG_THREADPROC pFn)<br />
{<br />
	// Do not change horses halfway diown the race!<br />
	ASSERT(m_nDlgStatus==THREADSTATE_NOT_STARTED);<br />
<br />
	PFN_PROGRESS_DLG_THREADPROC pfnOld=m_pFnThreadProc;<br />
	m_pFnThreadProc=pFn;<br />
	return pfnOld;<br />
}<br />
<br />
<br />
//////////////////////////////////////////////<br />
// This Function may be called by Both Threads.<br />
void CProgressDlg::EndDialog(int ExitCode)<br />
{<br />
	// Called before OnInitDialog??<br />
	ASSERT(m_hWnd);<br />
<br />
	// If the thread is running, set the Termination Flag.<br />
	// The Users Thread Function's Response to 'ShouldTerminate' should terminate<br />
	// the thread by Calling EndDialog again, and returning from the WorkerThhead<br />
	// User Function.<br />
	EnterCriticalSection(&m_cs);<br />
	if(m_nDlgStatus==THREADSTATE_RUNNING){<br />
<br />
		m_dwDlgResult=ExitCode;<br />
		m_bShouldTerminate=TRUE;<br />
		LeaveCriticalSection(&m_cs);<br />
<br />
		return;		<br />
	}<br />
	LeaveCriticalSection(&m_cs);<br />
<br />
	ASSERT(m_dwDlgResult==ExitCode);<br />
<br />
	try{<br />
	::SendMessage(m_hWnd,WM_ENDDIALOG,m_dwDlgResult,0);<br />
	}<br />
	catch(...){<br />
		return;<br />
	}<br />
<br />
}<br />
////////////////////////////////////////////////<br />
// This is the Target of SendMsg(WM_ENDDIALOG)<br />
void CProgressDlg::_OnEndDialog(int ExitCode)<br />
{<br />
	try{<br />
	m_pWinThread;<br />
	m_dwDlgResult=ExitCode;<br />
	ASSERT(::IsWindow(m_hWnd));<br />
<br />
	if (m_nFlags & (WF_MODALLOOP|WF_CONTINUEMODAL))<br />
		EndModalLoop(ExitCode);<br />
<br />
	::EndDialog(m_hWnd, ExitCode);<br />
	}<br />
	catch(...){<br />
		return;<br />
	}<br />
<br />
}<br />
<br />
DWORD CProgressDlg::GetThreadResult()<br />
{<br />
	return m_dwThreadResult;<br />
}<br />
<br />

Now, all works well in my latest App, until I want to End the Dialog.

All goes well,
CProgressDlg::EndDialog(int ExitCode)
is called, SendMessage calls OnEndDialog(...), which terminates successfully, and then the App terminates with an Exception.

In case you ask, why not trace and debug, the App behaves as expected in Debug Mode, I get this behaviuor only in the Retail version.

I got this far by setting 'StillAlive' traps in the retail version, and do not know how to get further.

Regards,

Smile | :)

Bram van Kampen

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

Stephen Hewitt8-Jun-10 18:18

Stephen Hewitt

8-Jun-10 18:18

Debug the retail version. Build it with debug information and proceed as normal. Debug don't really care if it's a release or debug build.

Steve

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

Bram van Kampen8-Jun-10 21:53

Bram van Kampen

8-Jun-10 21:53

Did that.

It bombs somewhere in the bowels of USER32.DLL (for which I have NO code) as soon as I link with the MFC Retail Libs. It does this in One App only. I rebuilt another 5 Apps using Identical Code and Calling sequence, and it works fine.

Regards,

Smile | :)

Bram van Kampen

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

ThatsAlok8-Jun-10 19:06

ThatsAlok

8-Jun-10 19:06

Using SendMessage api thrown from same thread to same thread is problem in itself because SendMessage api is blocking call, better use PostMessage.

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
Never mind - my own stupidity is the source of every "problem" - Mixture

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

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

Stephen Hewitt8-Jun-10 19:50

Stephen Hewitt

8-Jun-10 19:50

I'm not sure what you mean exactly, but using SendMessage to send a message to the same thread as the sender is fine (in fact it's the most common case).

Steve

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

Bram van Kampen8-Jun-10 21:40

Bram van Kampen

8-Jun-10 21:40

ThatsAlok Using SendMessage api thrown from same thread to same thread is problem in itself because SendMessage api is blocking call

No!
The Doccumentation states clearly that SendMessage calls the WinProc immediately when called from the same thread.

This is what Windows itself does the whole time in a Single Threaded App.

Smile | :)

Bram van Kampen

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

SandipG 8-Jun-10 20:04

SandipG

8-Jun-10 20:04

Bram van Kampen wrote:
void CProgressDlg::_OnEndDialog(int ExitCode)

I doubt about this line. You will probably need to handle both the params from SendMessage. i.e. WPARAM, LPARAM.

Also

Bram van Kampen wrote:
WM_ENDDIALOG=WM_USER+1,

Not recommended as these values are already used by windows for some other messages. But I don't think it will cause the problem you are facing.

Regards,
Sandip.

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

Bram van Kampen8-Jun-10 21:46

Bram van Kampen

8-Jun-10 21:46

SandipG wrote:
Bram van Kampen wrote:
void CProgressDlg::_OnEndDialog(int ExitCode)

I doubt about this line. You will probably need to handle both the params from SendMessage. i.e. WPARAM, LPARAM.

No, The use of the Params is optional. At Any rate, SendMessage lands safely at the handler. It trashes when SendMessage returns.

SandipG wrote:
Bram van Kampen wrote:
WM_ENDDIALOG=WM_USER+1,

Not recommended as these values are already used by windows for some other messages. But I don't think it will cause the problem you are facing.

Well, what would you reccommend instead. It could not be the problem, because SendMessage lands at the correct Handler.

Thanks

Smile | :)

Bram van Kampen

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

SandipG 8-Jun-10 22:03

SandipG

8-Jun-10 22:03

Bram van Kampen wrote:
No, The use of the Params is optional. At Any rate, SendMessage lands safely at the handler. It trashes when SendMessage returns.

Yes, that is why i feel its the parameter issue. You can read more about it here[^] in the parameter counts section.

Bram van Kampen wrote:
Well, what would you reccommend instead. It could not be the problem, because SendMessage lands at the correct Handler.

Also i said it is not the problem just not recommended. About this you can read here[^]

I hope it helps.

Regards,
Sandip.

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.

Kelly Herald9-Jun-10 7:03

Kelly Herald

9-Jun-10 7:03

SandipG wrote:
Yes, that is why i feel its the parameter issue. You can read more about it here[^] in the parameter counts section.

Joe's essays saved my butt many times.

Kelly Herald
Software Developer

Re: Failure in SendMessage in Retail Verrsion only, has me baffled.(SOLVED)

Bram van Kampen9-Jun-10 10:38

Bram van Kampen

9-Jun-10 10:38

Humble Pie is being eaten here.

It was a Parameter issue. Entered a dummy int, and problem is gone.

It baffles me however that this does not seem to affect the Debug Mode.

Thanks to everybody for their invaluable help and Comments.

Regards,
Dead | X|

Bram van Kampen

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