[C++] How do I know FILE_FLAG_OVERLAPPED has been set in the file handle ?

Hello Experts,

I want to know FILE_FLAG_OVERLAPPED flag has been set in the file handle.

I got a file handle from DuplicateHandle() and that is HANDLE_TYPE_FILE and
my target file name.
I want to read that file by using duplicated handle, but I don't know
FILE_FLAG_OVERLAPPED flag has been set or not into that file handle.

If I know that flag information, I can call ReadFile() with/without OVERLAPPED
structure pointer.

Any hints welcome.

Windows 7 32bit
C++Builder

Nobuo Miwa
Nobuo MiwaSecurity EngineerAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

 
jkrCommented:
>>I want to read that file by using duplicated handle, but I don't know
>>FILE_FLAG_OVERLAPPED flag has been set or not into that file handle.

>>If I know that flag information, I can call ReadFile() with/without OVERLAPPED
>>structure pointer.

It's actually quite easy: Even though there is no documented means to find out if that flag has been set, you can deal with this in both ways

- just don't pass an OVERLAPPED pointer, use NULL instead. The operation will be carried out synchronously (setting that flag does not mean you have to use the HANDLE in any async calls)

- pass an OVERLAPPED pointer anyway. If the flag was not set, the operation will be carried out synchronously. If it was set, use the means of async I/O.

A little more here: http://blogs.msdn.com/b/oldnewthing/archive/2012/04/05/10290954.aspx ("You can use an OVERLAPPED structure with synchronous I/O, too")
0

Experts Exchange Solution brought to you by ConnectWise

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
 
Nobuo MiwaSecurity EngineerAuthor Commented:
Great thanks !
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.