Re: 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

===================================
This list is hosted by DevelopMentor®  http://www.develop.com

View archives and manage your subscription(s) at http://discuss.develop.com