<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=GB2312"> <META content="MSHTML 6.00.2900.3314" name=GENERATOR> <STYLE>BLOCKQUOTE { MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; MARGIN-LEFT: 2em } OL { MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px } UL { MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px } </STYLE> </HEAD> <BODY style="BORDER-TOP-WIDTH: 0px; BORDER-LEFT-WIDTH: 0px; BORDER-BOTTOM-WIDTH: 0px; BORDER-RIGHT-WIDTH: 0px"> <DIV><FONT face=Verdana><FONT size=2>Integrate Windows I/O Completion Port into Libevent</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>IOCP is true async i/o model, and libevent is event-driven i/o model.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>1. How to emulate event-driven recv/send ?<BR>It is possible to use IOCP to emulate event-driven mode. When you make read or write calls, pass in a zero-byte buffer (ie, you can manage your i/o buffers using event driven semantics). So if you issue a read passing in a zero-byte length buffer, your will get notified when there is data to read.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>2. How to emulate event-driven accept ?<BR>The WSAEventSelect API provides an event-driven accept mechanism.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>3. How to integrate these two mechanism ?<BR>When we issue a WSARecv or WSASend, we need to pass a OVERLAPPED structure. This structure has a hEvent member.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2><A href="http://msdn.microsoft.com/en-us/library/ms742203(VS.85).aspx">http://msdn.microsoft.com/en-us/library/ms742203(VS.85).aspx</A><BR>If the lpCompletionRoutine parameter is NULL, the hEvent parameter of lpOverlapped is signaled when the overlapped operation completes if it contains a valid event object handle. An application can use WSAWaitForMultipleEvents or WSAGetOverlappedResult to wait or poll on the event object.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>We could use one event for all WSARecv/WSASend.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2><A href="http://msdn.microsoft.com/en-us/library/ms686211(VS.85).aspx">http://msdn.microsoft.com/en-us/library/ms686211(VS.85).aspx</A><BR>Setting an event that is already set has no effect.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>So it is possible to use WSAWaitForMultipleEvents to integrate IOCP and WSAEventSelect.</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>4. Solution</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>/* objects[0] for iocp operations, object[1..63] for accept */<BR>HANDLE objects[64];<BR>struct event * accepts[64];</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>struct win32iocp_event event1;<BR>event1.overlapped.hEvent = objects[0];<BR>WSARecv( ..., &event1.overlapped, ... );<BR>....</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>struct win32iocp_event event2;<BR>event2.overlapped.hEvent = objects[0];<BR>WSASend( ..., &event2.overlapped, ... );<BR>...</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>WSAEventSelect( ev1->ev_fd, objects[1], FD_ACCEPT );<BR>accepts[1] = ev1;<BR>...</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>WSAEventSelect( ev2->ev_fd, objects[2], FD_ACCEPT );<BR>accepts[2] = ev2;<BR>...</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>int index = WSAWaitForMultipleEvents( 64, objects, FALSE, timeout, FALSE );<BR>index = index - WSA_WAIT_EVENT_0;</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>if( index > 0 ) {<BR> struct event * event = win32iocp_op->accepts[index];<BR> event_active (event, EV_READ | EV_ACCEPT, 1);<BR>}</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>if( index == 0 ) {<BR> for( ; ; ) {<BR>  GetQueuedCompletionPort( ...... );<BR> }<BR>}</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2>5. Limitation<BR>It can only support 63 accept fds.</FONT></FONT></DIV> <DIV> </DIV> <DIV>6. Source code</DIV> <DIV><A href="http://spserver.googlecode.com/files/libevent-1.4.4-iocp.zip">http://spserver.googlecode.com/files/libevent-1.4.4-iocp.zip</A></DIV> <DIV>diff file : libevent-1.4.4-iocp\libevent-iocp\diff.txt</DIV> <DIV>add file : libevent-1.4.4-iocp\WIN32-Code\win32iocp.cpp</DIV> <DIV> </DIV> <DIV><FONT face=Verdana><FONT size=2></FONT> </DIV> <DIV><FONT size=2></FONT> </DIV> <DIV align=left><FONT size=2> <HR style="WIDTH: 122px; HEIGHT: 2px" SIZE=2> </FONT></DIV> <DIV><FONT color=#c0c0c0><FONT size=2><SPAN>liusifan</SPAN></FONT></DIV> <DIV><FONT size=2>2008-06-01</FONT></FONT></DIV></FONT></BODY></HTML>