Failure of CreateFile()

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Failure of CreateFile()

 
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  #1
Sep 1st, 2007
c Syntax (Toggle Plain Text) 
  1. BOOL setContent( LPSTR szContent )
  2. {    
  3. 	HANDLE hFile;
  4. 	BOOL bSuccess = FALSE;
  5. 	DWORD dwTextLength;
  6.  
  7. 	hFile = CreateFile( "data.txt" , GENERIC_WRITE , 0 , NULL , CREATE_ALWAYS , FILE_ATTRIBUTE_NORMAL , NULL );
  8.  
  9. 	if( hFile != INVALID_HANDLE_VALUE )
  10. 	{
  11.         DWORD dwWritten;
  12.         dwTextLength = strlen( szPassword );
  13.  
  14.         if( WriteFile( hFile , szPassword , dwTextLength , &dwWritten , NULL ) )
  15.             bSuccess = TRUE;
  16.         else
  17. 		    LastErrorMessage( "setPassword()");
  18. 	}
  19. 	else
  20. 	{
  21.         MessageBox(hwnd,"setPassword(): CreateFile failed.",0,0);
  22.         LastErrorMessage( "setPassword()"); // Format and Display GetLastError
  23.     }
  24. 	return bSuccess;     
  25. }

CreateFile API here seems to always return INVALID_HANDLE_VALUE, and GetLastError reports that the operation completed successfully, but I still can't get a handle to the file.

What am I doing wrong?
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Re: Failure of CreateFile()

 
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  #2
Sep 1st, 2007
Do you have a minimally complete snippet that I might try to play along with?
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand
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Re: Failure of CreateFile()

 
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  #3
Sep 1st, 2007
The only thing I can think of is that another process or instance of this application already has the file open, and because you are not sharing the file this would not allow the handle to be created. Other than that, your code is correct.
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Re: Failure of CreateFile()

 
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  #4
Sep 1st, 2007
And don't forget to close the file < CloseFile() > before leaving that function!
Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.
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Re: Failure of CreateFile()

 
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  #5
Sep 1st, 2007
Do you mean CloseHandle()?

Before when I call this function I am using a function to getContent() of a file. Within that function I do make sure to Close the handle to the file after reading the content into memory..

c Syntax (Toggle Plain Text) 
  1. char * getContent( )
  2. {
  3. 	HANDLE hFile;
  4. 	BOOL bSuccess = FALSE;
  5. 	LPSTR pszFileText;
  6.  
  7. 	hFile = CreateFile( PASSWORD_FILE , GENERIC_READ , FILE_SHARE_READ , NULL , OPEN_EXISTING , 0 , NULL );
  8.  
  9. 	if( hFile != INVALID_HANDLE_VALUE )
  10. 	{
  11. 		DWORD dwFileSize;
  12. 		dwFileSize = GetFileSize( hFile , NULL );
  13.  
  14. 		if( dwFileSize != 0xFFFFFFFF )
  15. 		{
  16. 			pszFileText = (LPSTR) GlobalAlloc( GPTR , dwFileSize + 1 );
  17.  
  18. 			if( pszFileText != NULL )
  19. 			{
  20. 				DWORD dwRead;
  21.  
  22. 				if( ReadFile( hFile , pszFileText , dwFileSize , &dwRead , NULL ) )
  23. 				{
  24. 					pszFileText [ dwFileSize ] = 0; // Add null terminator
  25.                     return pszFileText;
  26. 				}
  27. 				GlobalFree( pszFileText );
  28. 			}
  29. 		}
  30. 		CloseHandle( hFile );
  31. 	}
  32. 	return "";  
  33. }

This works fine, but after calling it, the setContent does not work.

Actually after checking, both above functions work correctly by themselves, but its only after calling getContent that setContent does not work.

NOTE: I have modified the original getContent to include CloseHandle( hFile )
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Re: Failure of CreateFile()

 
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  #6
Sep 1st, 2007
Similar to goto statements, I've found multiple return paths are as equally problematic. If line 25 is executed then hFile is still open
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Re: Failure of CreateFile()

 
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  #7
Sep 2nd, 2007
Ooh, Yes I see where its gone wrong now. I'm returning before Closing the Handle to the file. So really I should return pszFileText at the end, and obviously remove GlobalFree( pszFileText )..

Cheers.
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Re: Failure of CreateFile()

 
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  #8
Sep 2nd, 2007
Exactly, keep related stuff in the function or subroutine.
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