From 49a185bf9798e56336a2df8aa3da49a0d6238b1a Mon Sep 17 00:00:00 2001
From: brain <brain@e03df62e-2008-0410-955e-edbf42e46eb7>
Date: Tue, 15 Apr 2008 22:38:20 +0000
Subject: the select socket engine went on the assumption that a socket may
 remove itself from the socket engine in the middle of the loop. Cull lists
 did away with this late 1.0, early 1.1, so there is now no need to keep this
 archaic system in here and we can halve the number of loops per cycle down to
 half what they used to be.

git-svn-id: http://svn.inspircd.org/repository/trunk/inspircd@9512 e03df62e-2008-0410-955e-edbf42e46eb7
---
 src/socketengines/socketengine_select.cpp | 65 +++++++++++++------------------
 1 file changed, 28 insertions(+), 37 deletions(-)

(limited to 'src/socketengines/socketengine_select.cpp')

diff --git a/src/socketengines/socketengine_select.cpp b/src/socketengines/socketengine_select.cpp
index 3f5210f3c..5c61ff0ae 100644
--- a/src/socketengines/socketengine_select.cpp
+++ b/src/socketengines/socketengine_select.cpp
@@ -92,84 +92,75 @@ int SelectEngine::GetRemainingFds()
 
 int SelectEngine::DispatchEvents()
 {
-	int result = 0;
 	timeval tval;
 	int sresult = 0;
 	socklen_t codesize;
-	int errcode;
+	int errcode = 0;
 
 	FD_ZERO(&wfdset);
 	FD_ZERO(&rfdset);
 	FD_ZERO(&errfdset);
 
+	/* Populate the select FD set (this is why select sucks compared to epoll, kqueue, IOCP) */
 	for (std::map<int,int>::iterator a = fds.begin(); a != fds.end(); a++)
 	{
 		if (ref[a->second]->Readable())
+			/* Read notifications */
 			FD_SET (a->second, &rfdset);
 		else
+			/* Write notifications */
 			FD_SET (a->second, &wfdset);
+
+		/* Explicitly one-time writeable */
 		if (writeable[a->second])
 			FD_SET (a->second, &wfdset);
 
+		/* All sockets must receive error notifications regardless */
 		FD_SET (a->second, &errfdset);
 	}
 
+	/* One second waits */
 	tval.tv_sec = 1;
 	tval.tv_usec = 0;
 
 	sresult = select(FD_SETSIZE, &rfdset, &wfdset, &errfdset, &tval);
 
-	if (sresult > 0)
-	{
-		for (std::map<int,int>::iterator a = fds.begin(); a != fds.end(); a++)
-		{
-			if ((FD_ISSET (a->second, &rfdset)) || (FD_ISSET (a->second, &wfdset)) || FD_ISSET (a->second, &errfdset))
-			{
-				ev[result++] = ref[a->second];
-			}
-		}
-	}
+	/* Nothing to process this time around */
+	if (sresult < 1)
+		return 0;
 
-	/** An event handler may remove its own descriptor from the list, therefore it is not
-	 * safe to directly iterate over the list and dispatch events there with STL iterators.
-	 * Thats a shame because it makes this code slower and more resource intensive, but maybe
-	 * the user should stop using select(), as select() smells anyway.
-	 */
-	for (int i = 0; i < result; i++)
+	/* Safe assumption (as of 1.1 anyway) that a socket can't remove itself from the list in the middle of the loop */
+	for (std::map<int,int>::iterator a = fds.begin(); a != fds.end(); a++)
 	{
-		if (ev[i])
+		EventHandler* ev = ref[a->second];
+		if (ev)
 		{
-			if (FD_ISSET (ev[i]->GetFd(), &errfdset))
+			if (FD_ISSET (ev->GetFd(), &errfdset))
 			{
 				ErrorEvents++;
-
-				if (getsockopt(ev[i]->GetFd(), SOL_SOCKET, SO_ERROR, (char*)&errcode, &codesize) < 0)
+				if (getsockopt(ev->GetFd(), SOL_SOCKET, SO_ERROR, (char*)&errcode, &codesize) < 0)
 					errcode = errno;
 
-				ev[i]->HandleEvent(EVENT_ERROR, errcode);
-
+				ev->HandleEvent(EVENT_ERROR, errcode);
 				continue;
 			}
 			else
 			{
-				if (writeable[ev[i]->GetFd()])
+				/* NOTE: This is a pair of seperate if statements as the socket
+				 * may be in both read and writeable state at the same time.
+				 * If an error event occurs above it is not worth processing the
+				 * read and write states even if set.
+				 */
+				if (FD_ISSET (ev->GetFd(), &wfdset))
 				{
 					WriteEvents++;
-					writeable[ev[i]->GetFd()] = false;
-					ev[i]->HandleEvent(EVENT_WRITE);
+					writeable[ev->GetFd()] = false;
+					ev->HandleEvent(EVENT_WRITE);
 				}
-				else
+				if (FD_ISSET (ev->GetFd(), &rfdset))
 				{
-					if (ev[i]->Readable())
-					{
 						ReadEvents++;
-						ev[i]->HandleEvent(EVENT_READ);
-					}
-					else
-					{
-						WriteEvents++;
-						ev[i]->HandleEvent(EVENT_WRITE);
-					}
+						ev->HandleEvent(EVENT_READ);
 				}
 			}
 		}
-- 
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