Solved

How do I get the access mode that was used to obtain a pariticular file (or file handle)?

Posted on 2004-07-31
2
344 Views
Last Modified: 2010-04-17
I am trying to write a generic file read programe that accept either a CFile or a file handle.
However, when testing it, I sometimes get error because the file was open in an unexpected mode (like write only etc), hence, I would like to examine the CFile or file handle that is passed to the me and see if it is open appropriately. However, I find that there is NO way to examine the way the file was opened (like with 'r' or 'w' etc).
Can any one tell me if there is a way ( as easy as possible) to examine the mode that was used to open this particular file? to avoid errors.

Thank you
0
Comment
Question by:hshliang
2 Comments
 
LVL 55

Expert Comment

by:Jaime Olivares
ID: 11685759
As you said, there is no way, notice that CFile is an encapsulation of a WinAPI's HANDLE to a file, so both are identical.
WinAPI function GetFileInformationByHandle() doesn't tell you about file access mode, and CFile doesn't save extra information about it, even in its protected members.
0
 
LVL 8

Accepted Solution

by:
adg080898 earned 125 total points
ID: 11692170
You could subclass CFile to intercept the information you desire and store it in your subclass members. This would require a search-and-replace for CFile to whatever you name the subclass, but actual code would not need to be touched.

Something like this:

class MyCFile : public CFile {
protected:
    UINT nMyOpenFlags;
public:
    MyCFile(LPCTSTR pFilename, UINT nOpenFlags);
    BOOL Open(LPCTSTR lpszFileName, UINT nOpenFlags, CFileException* pError = NULL);

    UINT GetOpenFlags() { return nMyOpenFlags; }
};

MyCFile::MyCFile(LPCTSTR pFilename, UINT nOpenFlags) : CFile(pFilename, nOpenFlags)
{
    nMyOpenFlags = nOpenFlags;
}

BOOL MyCFile::Open(LPCTSTR lpszFileName, UINT nOpenFlags, CFileException* pError = NULL)
{
    nMyOpenFlags = nOpenFlags;

    return ((CFile*)this)->Open(lpszFileName, nOpenFlags, pError);
}

0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article will show, step by step, how to integrate R code into a R Sweave document
In this post we will learn how to make Android Gesture Tutorial and give different functionality whenever a user Touch or Scroll android screen.

696 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question