From 8a14552e56c4ddffeb01f5042ce55e1dc92c10f6 Mon Sep 17 00:00:00 2001
From: TheLastRar <TheLastRar@users.noreply.github.com>
Date: Sat, 6 Apr 2024 19:16:32 +0100
Subject: [PATCH] DEV9: Move and fix GetDelta Function

---
 .../DEV9/Sessions/TCP_Session/TCP_Session.cpp  | 18 ++++++++++++++++++
 pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.h  |  2 +-
 .../Sessions/TCP_Session/TCP_Session_Out.cpp   | 13 ++-----------
 3 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.cpp b/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.cpp
index ee57d04867..2185ab9a14 100644
--- a/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.cpp
+++ b/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.cpp
@@ -68,6 +68,24 @@ namespace Sessions
 	{
 	}
 
+	s32 TCP_Session::GetDelta(u32 a, u32 b)
+	{
+		s64 delta = static_cast<s64>(a) - static_cast<s64>(b);
+		if (delta > 0.5 * UINT_MAX)
+		{
+			delta = -static_cast<s64>(UINT_MAX) + a - b - 1;
+			Console.Error("DEV9: TCP: [PS2] SequenceNumber Overflow Detected");
+			Console.Error("DEV9: TCP: [PS2] New Data Offset: %d bytes", delta);
+		}
+		if (delta < -0.5 * UINT_MAX)
+		{
+			delta = UINT_MAX - b + a + 1;
+			Console.Error("DEV9: TCP: [PS2] SequenceNumber Overflow Detected");
+			Console.Error("DEV9: TCP: [PS2] New Data Offset: %d bytes", delta);
+		}
+		return delta;
+	}
+
 	TCP_Packet* TCP_Session::CreateBasePacket(PayloadData* data)
 	{
 		//DevCon.WriteLn("Creating Base Packet");
diff --git a/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.h b/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.h
index 1437e50356..765574fdca 100644
--- a/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.h
+++ b/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session.h
@@ -95,7 +95,7 @@ namespace Sessions
 
 		NumCheckResult CheckRepeatSYNNumbers(PacketReader::IP::TCP::TCP_Packet* tcp);
 		NumCheckResult CheckNumbers(PacketReader::IP::TCP::TCP_Packet* tcp);
-		u32 GetDelta(u32 parExpectedSeq, u32 parGotSeq);
+		s32 GetDelta(u32 a, u32 b); //Returns a - b
 		//Returns true if errored
 		bool ErrorOnNonEmptyPacket(PacketReader::IP::TCP::TCP_Packet* tcp);
 
diff --git a/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session_Out.cpp b/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session_Out.cpp
index db1fce3168..9eed93ca27 100644
--- a/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session_Out.cpp
+++ b/pcsx2/DEV9/Sessions/TCP_Session/TCP_Session_Out.cpp
@@ -308,7 +308,9 @@ namespace Sessions
 		windowSize.store(tcp->windowSize << windowScale);
 
 		const NumCheckResult Result = CheckNumbers(tcp);
+		//Check if we already have some of the data sent
 		const uint delta = GetDelta(expectedSeqNumber, tcp->sequenceNumber);
+		pxAssert(delta >= 0);
 		//if (Result == NumCheckResult::GotOldData)
 		//{
 		//	DevCon.WriteLn("[PS2] New Data Offset: %d bytes", delta);
@@ -464,17 +466,6 @@ namespace Sessions
 
 		return NumCheckResult::OK;
 	}
-	u32 TCP_Session::GetDelta(u32 parExpectedSeq, u32 parGotSeq)
-	{
-		u32 delta = parExpectedSeq - parGotSeq;
-		if (delta > 0.5 * UINT_MAX)
-		{
-			delta = UINT_MAX - parExpectedSeq + parGotSeq;
-			Console.Error("DEV9: TCP: [PS2] SequenceNumber Overflow Detected");
-			Console.Error("DEV9: TCP: [PS2] New Data Offset: %d bytes", delta);
-		}
-		return delta;
-	}
 	bool TCP_Session::ErrorOnNonEmptyPacket(TCP_Packet* tcp)
 	{
 		NumCheckResult ResultFIN = CheckNumbers(tcp);