Re: Overlapped file IO

Definitely.


-----Original Message-----
From: Discussion of development on the .NET platform using any managed language [mailto:[email protected]] On Behalf Of Peter Obiefuna
Sent: Wednesday, November 21, 2007 21:53
To: [email protected]
Subject: Re: [DOTNET-CLR] Overlapped file IO

Alex,
Could you let us share your work when you're done.
P

--------------------------------------------------
From: "Alex Ivanoff" <[email protected]>
Sent: Monday, November 19, 2007 8:43 PM
To: <[email protected]>
Subject: Re: [DOTNET-CLR] Overlapped file IO

> .NET async file IO is a subset of Win32 overlapped IO.
>
> Looks like I am going to have to implement it myself.
>
> ________________________________
>
> From: Discussion of development on the .NET platform using any managed
> language on behalf of Dan Farino
> Sent: Mon 11/19/2007 18:18
> To: [email protected]
> Subject: Re: [DOTNET-CLR] Overlapped file IO
>
>
>
> Hmm...sounds like our definitions of "overlapped" are a bit different
> here.
>
> I interpreted it as just meaning passing in the flag
> FILE_FLAG_OVERLAPPED (which is the same numeric value as
> FileOptions.Asynchronous) to CreateFile and using the OVERLAPPED
> structure for performing async I/O with ReadFile and WriteFile.
>
> So while you can't touch the fields of the OVERLAPPED struct yourself,
> FileStream is using it under the covers to accomplish the async I/O.
>
> -----Original Message-----
> From: Discussion of development on the .NET platform using any managed
> language [mailto:[email protected]] On Behalf Of Alex
> Ivanoff
> Sent: Monday, November 19, 2007 3:56 PM
> To: [email protected]
> Subject: Re: [DOTNET-CLR] Overlapped file IO
>
> FileStream.BeginXXX/EndXXX methods are asynchronous, but not overlapped.
> You cannot specify where to start reading/writing (Win32
> OVERLAPPED.Offset/OffsetHigh members) nor can you issue multiple
> read/write operations against the same file handle at the same time.
> From MSDN:
>
> "EndRead must be called exactly for every call to BeginRead. Failing to
> end a read process before beginning another read can cause undesirable
> behavior such as deadlock."
>
> This is not overlapped at all.
>
>
> -----Original Message-----
> From: Discussion of development on the .NET platform using any managed
> language [mailto:[email protected]] On Behalf Of Dan Farino
> Sent: Monday, November 19, 2007 17:42
> To: [email protected]
> Subject: Re: [DOTNET-CLR] Overlapped file IO
>
> Yes it does (except on Windows 9x). For FileStream, use the constructor:
>
> public FileStream(string path, FileMode mode, FileSystemRights rights,
> FileShare share, int bufferSize, FileOptions options)
>
> Make sure you pass in FileOptions.Asynchronous. Then, use
> BeginRead/Write and EndRead/Write. This uses overlapped I/O. (The only
> part that is still synchronous is the constructor since there is no
> async version of the underlying CreateFile Win32 call.)
>
> Other classes such as Socket also use overlapped I/O when you use
> BeginXXX/EndXXX. In the case of Socket and others, you don't need to
> pass any special flags in like you have to with FileStream's
> FileOptions.
>
> -----Original Message-----
> From: Discussion of development on the .NET platform using any managed
> language [mailto:[email protected]] On Behalf Of Alex
> Ivanoff
> Sent: Monday, November 19, 2007 2:44 PM
> To: [email protected]
> Subject: [DOTNET-CLR] Overlapped file IO
>
> Does .NET 2.0 have support for overlapped IO or do I need to implement
> one myself?
>
> Alex
>
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