From 9c62fe8db26ee9fe834d44691de8a72298739550 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Strohh=C3=A4cker?=
 <c2woody@users.sourceforge.net>
Date: Wed, 20 Jul 2005 19:20:23 +0000
Subject: [PATCH] bug when dos mem resize is used to shrink memory blocks
 (QuickBasic, fixes Shard of Spring)

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@2244
---
 src/dos/dos_memory.cpp | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/dos/dos_memory.cpp b/src/dos/dos_memory.cpp
index 55972ac3..8ffc6926 100644
--- a/src/dos/dos_memory.cpp
+++ b/src/dos/dos_memory.cpp
@@ -138,6 +138,24 @@ bool DOS_ResizeMemory(Bit16u segment,Bit16u * blocks) {
 	DOS_MCB mcb(segment-1);
 	Bit16u total=mcb.GetSize();
 	DOS_MCB	mcb_next(segment+total);
+	if (*blocks<=total) {
+		if (GCC_UNLIKELY(*blocks==total)) {
+			/* Nothing to do */
+			return true;
+		}
+		/* Shrinking MCB */
+		DOS_MCB	mcb_new_next(segment+(*blocks));
+		mcb.SetSize(*blocks);
+		mcb_new_next.SetType(mcb.GetType());
+		if (mcb.GetType()==0x5a) {
+			/* Further blocks follow */
+			mcb.SetType(0x4d);
+		}
+
+		mcb_new_next.SetSize(total-*blocks-1);
+		mcb_new_next.SetPSPSeg(MCB_FREE);
+		return true;
+	}
 	if (mcb.GetType()!=0x5a) {
 		if (mcb_next.GetPSPSeg()==MCB_FREE) {
 			total+=mcb_next.GetSize()+1;