From 35c9b5330960ddcd50544a1f3fb03b8971ade1d3 Mon Sep 17 00:00:00 2001
From: Sjoerd van der Berg <harekiet@users.sourceforge.net>
Date: Wed, 14 Aug 2002 22:13:31 +0000
Subject: [PATCH] Extra empty buffer test.

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@151
---
 src/hardware/keyboard.cpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/hardware/keyboard.cpp b/src/hardware/keyboard.cpp
index f29cc65e..cc9c85b3 100644
--- a/src/hardware/keyboard.cpp
+++ b/src/hardware/keyboard.cpp
@@ -63,10 +63,12 @@ static Bit8u read_p61(Bit32u port) {
 static void write_p61(Bit32u port,Bit8u val) {
 //TODO Enable spreaker through here :)	
 	if ((val&128)) {					/* Keyboard acknowledge */
-		kbuf_used--;
-		kbuf_pos++;
-		if (kbuf_pos>=KEYBUFSIZE) kbuf_pos=0;
-		if (kbuf_used>0) PIC_ActivateIRQ(1);
+		if (kbuf_used) {
+			kbuf_used--;
+			kbuf_pos++;
+			if (kbuf_pos>=KEYBUFSIZE) kbuf_pos=0;
+			if (kbuf_used) PIC_ActivateIRQ(1);
+		}
 	}
 	port_61_data=val;
 	if ((val & 3)==3) {