From f7ceadf6dcde43e4539a81ff6d0ce65c0bb52dcd Mon Sep 17 00:00:00 2001
From: Nam Nguyen <namn@berkeley.edu>
Date: Mon, 9 Sep 2019 05:52:31 +0000
Subject: [PATCH] pack the TMegaPkt struct. define TMEGAPKT_SIZE.

memcpy((char *)&packeta[1] - packeta->dwSpaceLeft, packet, dwSize);

Source/msg.cpp does this calculation, which will be wrong if any padding is
added. To get this to work correctly, pack the structures, as suggested by
@AJenbo.

Also, define TMEGAPKT_SIZE because pNext can be 4 or 8 bytes.
---
 Source/msg.cpp | 2 +-
 structs.h      | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/Source/msg.cpp b/Source/msg.cpp
index a6f68f9d6..662f3855c 100644
--- a/Source/msg.cpp
+++ b/Source/msg.cpp
@@ -55,7 +55,7 @@ TMegaPkt *msg_get_next_packet()
 {
 	TMegaPkt *result;
 
-	sgpCurrPkt = (TMegaPkt *)DiabloAllocPtr(32008);
+	sgpCurrPkt = (TMegaPkt *)DiabloAllocPtr(TMEGAPKT_SIZE);
 	sgpCurrPkt->pNext = NULL;
 	sgpCurrPkt->dwSpaceLeft = 32000;
 
diff --git a/structs.h b/structs.h
index 622e2085f..0191eb723 100644
--- a/structs.h
+++ b/structs.h
@@ -955,11 +955,14 @@ typedef struct DJunk {
 } DJunk;
 #pragma pack(pop)
 
+#pragma pack(push, 1)
 typedef struct TMegaPkt {
 	struct TMegaPkt *pNext;
 	DWORD dwSpaceLeft;
 	BYTE data[32000];
 } TMegaPkt;
+#pragma pack(pop)
+#define TMEGAPKT_SIZE sizeof(TMegaPkt)
 
 typedef struct TBuffer {
 	DWORD dwNextWriteOffset;