From c510683d2a64e75a667134ef0b63e9638c474c28 Mon Sep 17 00:00:00 2001
From: madmaxoft <github@xoft.cz>
Date: Thu, 2 Jan 2014 17:33:18 +0100
Subject: [PATCH] Fixed unaligned memory access in FastNBT.

This should fix #420.
---
 src/StringUtils.cpp          | 30 ++++++++++++++++++++++++++++++
 src/StringUtils.h            |  9 +++++++++
 src/WorldStorage/FastNBT.cpp | 10 +++++-----
 3 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/src/StringUtils.cpp b/src/StringUtils.cpp
index f7aeeed26..5c6b99d88 100644
--- a/src/StringUtils.cpp
+++ b/src/StringUtils.cpp
@@ -764,3 +764,33 @@ AString Base64Decode(const AString & a_Base64String)
 
 
 
+
+short GetBEShort(const char * a_Mem)
+{
+	return (((short)a_Mem[0]) << 8) | a_Mem[1];
+}
+
+
+
+
+
+int GetBEInt(const char * a_Mem)
+{
+	return (((int)a_Mem[0]) << 24) | (((int)a_Mem[1]) << 16) | (((int)a_Mem[2]) << 8) | a_Mem[3];
+}
+
+
+
+
+
+void SetBEInt(char * a_Mem, Int32 a_Value)
+{
+	a_Mem[0] = a_Value >> 24;
+	a_Mem[1] = (a_Value >> 16) & 0xff;
+	a_Mem[2] = (a_Value >> 8) & 0xff;
+	a_Mem[3] = a_Value & 0xff;
+}
+
+
+
+
diff --git a/src/StringUtils.h b/src/StringUtils.h
index 3917cc4ec..471e843e4 100644
--- a/src/StringUtils.h
+++ b/src/StringUtils.h
@@ -81,6 +81,15 @@ extern AString ReplaceAllCharOccurrences(const AString & a_String, char a_From,
 /// Decodes a Base64-encoded string into the raw data
 extern AString Base64Decode(const AString & a_Base64String);
 
+/// Reads two bytes from the specified memory location and interprets them as BigEndian short
+extern short GetBEShort(const char * a_Mem);
+
+/// Reads four bytes from the specified memory location and interprets them as BigEndian int
+extern int GetBEInt(const char * a_Mem);
+
+/// Writes four bytes to the specified memory location so that they interpret as BigEndian int
+extern void SetBEInt(char * a_Mem, Int32 a_Value);
+
 // If you have any other string helper functions, declare them here
 
 
diff --git a/src/WorldStorage/FastNBT.cpp b/src/WorldStorage/FastNBT.cpp
index e55011069..64220f09a 100644
--- a/src/WorldStorage/FastNBT.cpp
+++ b/src/WorldStorage/FastNBT.cpp
@@ -80,7 +80,7 @@ bool cParsedNBT::ReadString(int & a_StringStart, int & a_StringLen)
 {
 	NEEDBYTES(2);
 	a_StringStart = m_Pos + 2;
-	a_StringLen = ntohs(*((short *)(m_Data + m_Pos)));
+	a_StringLen = GetBEShort(m_Data + m_Pos);
 	if (a_StringLen < 0)
 	{
 		// Invalid string length
@@ -135,7 +135,7 @@ bool cParsedNBT::ReadList(eTagType a_ChildrenType)
 	
 	// Read the count:
 	NEEDBYTES(4);
-	int Count = ntohl(*((int *)(m_Data + m_Pos)));
+	int Count = GetBEInt(m_Data + m_Pos);
 	m_Pos += 4;
 	if (Count < 0)
 	{
@@ -197,7 +197,7 @@ bool cParsedNBT::ReadTag(void)
 		case TAG_ByteArray:
 		{
 			NEEDBYTES(4);
-			int len = ntohl(*((int *)(m_Data + m_Pos)));
+			int len = GetBEInt(m_Data + m_Pos);
 			m_Pos += 4;
 			if (len < 0)
 			{
@@ -229,7 +229,7 @@ bool cParsedNBT::ReadTag(void)
 		case TAG_IntArray:
 		{
 			NEEDBYTES(4);
-			int len = ntohl(*((int *)(m_Data + m_Pos)));
+			int len = GetBEInt(m_Data + m_Pos);
 			m_Pos += 4;
 			if (len < 0)
 			{
@@ -401,7 +401,7 @@ void cFastNBTWriter::EndList(void)
 	ASSERT(m_Stack[m_CurrentStack].m_Type == TAG_List);
 	
 	// Update the list count:
-	*((int *)(m_Result.c_str() + m_Stack[m_CurrentStack].m_Pos)) = htonl(m_Stack[m_CurrentStack].m_Count);
+	SetBEInt((char *)(m_Result.c_str() + m_Stack[m_CurrentStack].m_Pos), m_Stack[m_CurrentStack].m_Count);
 
 	--m_CurrentStack;
 }