From 3398ce7e50f1c269e8221df04e1eefb52d54c820 Mon Sep 17 00:00:00 2001
From: systocrat <systocrat@outlook.com>
Date: Tue, 2 Jan 2018 01:01:00 +0200
Subject: Improve performance under load of OnDataReady and remove C-isms.

Re-use variables initialized within loop, const-ify config variables
accessed repeatedly, remove eol_found label.

Merges #1451.
---
 src/users.cpp | 53 ++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 38 insertions(+), 15 deletions(-)

(limited to 'src/users.cpp')

diff --git a/src/users.cpp b/src/users.cpp
index 5ddd98def..7f56994d4 100644
--- a/src/users.cpp
+++ b/src/users.cpp
@@ -227,37 +227,56 @@ void UserIOHandler::OnDataReady()
 			user->nick.c_str(), (unsigned long)recvq.length(), user->MyClass->GetRecvqMax());
 		return;
 	}
+
 	unsigned long sendqmax = ULONG_MAX;
 	if (!user->HasPrivPermission("users/flood/increased-buffers"))
 		sendqmax = user->MyClass->GetSendqSoftMax();
+
 	unsigned long penaltymax = ULONG_MAX;
 	if (!user->HasPrivPermission("users/flood/no-fakelag"))
 		penaltymax = user->MyClass->GetPenaltyThreshold() * 1000;
 
+	// The maximum size of an IRC message minus the terminating CR+LF.
+	const size_t maxmessage = ServerInstance->Config->Limits.MaxLine - 2;
+	std::string line;
+	line.reserve(maxmessage);
+
+	bool eol_found;
+	std::string::size_type qpos;
+
 	while (user->CommandFloodPenalty < penaltymax && getSendQSize() < sendqmax)
 	{
-		std::string line;
-		line.reserve(ServerInstance->Config->Limits.MaxLine);
-		std::string::size_type qpos = 0;
-		while (qpos < recvq.length())
+		qpos = 0;
+		eol_found = false;
+
+		const size_t qlen = recvq.length();
+		while (qpos < qlen)
 		{
 			char c = recvq[qpos++];
 			switch (c)
 			{
-			case '\0':
-				c = ' ';
-				break;
-			case '\r':
-				continue;
-			case '\n':
-				goto eol_found;
+				case '\0':
+					c = ' ';
+					break;
+				case '\r':
+					continue;
+				case '\n':
+					eol_found = true;
+					break;
 			}
-			if (line.length() < ServerInstance->Config->Limits.MaxLine - 2)
+
+			if (eol_found)
+				break;
+
+			if (line.length() < maxmessage)
 				line.push_back(c);
 		}
-		// if we got here, the recvq ran out before we found a newline
-		return;
-eol_found:
+
+		// if we return here, we haven't found a newline and make no modifications to recvq
+		// so we can wait for more data
+		if (!eol_found)
+			return;
+
 		// just found a newline. Terminate the string, and pull it out of recvq
 		recvq.erase(0, qpos);
 
@@ -269,7 +288,11 @@ eol_found:
 		ServerInstance->Parser.ProcessBuffer(line, user);
 		if (user->quitting)
 			return;
+
+		// clear() does not reclaim memory associated with the string, so our .reserve() call is safe
+		line.clear();
 	}
+
 	if (user->CommandFloodPenalty >= penaltymax && !user->MyClass->fakelag)
 		ServerInstance->Users->QuitUser(user, "Excess Flood");
 }
-- 
cgit v1.2.3