[Libevent-users] Integrate Windows I/O Completion Port into Libevent

[liusifan]

Hi,

>>3. How to integrate these two mechanism ?
>>When we issue a WSARecv or WSASend, we need to pass a OVERLAPPED structure. This structure has a hEvent member.
>>We could use one event for all WSARecv/WSASend.

http://msdn.microsoft.com/en-us/library/ms686358(VS.85).aspx
Synchronization and Overlapped Input and Output

If an event is used, the hEvent member of the OVERLAPPED structure specifies a 
handle to the allocated event object. The system sets the state of the event object 
to nonsignaled when a call to the I/O function returns before the operation has been completed.


The integrate strategy for IOCP and WSAEventSelect is not safe.
Because WSARecv/WSASend will sets the state of the event object to nonsignaled.
This can lead to a race condition:
1.the first WSARecv/WSASend operations have completed, hEvent is signaled
2.the second WSARecv/WSASend has been called, hEvent has been reseted
3.WSAWaitForMultipleEvents will block until the second operations have completed

It need to try other way to integrate IOCP and WSAEventSelect.

Best Regards,

Stephen Liu