From 600080ba0c3286dc7d3cf5e3dce65afe344674d9 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Wed, 7 Jan 2015 21:43:21 -0800
Subject: [PATCH] GBA BIOS: Implement Diff8bitUnFilterVram

---
 CHANGES            |  2 +-
 src/gba/gba-bios.c | 28 +++++++++++++++++-----------
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/CHANGES b/CHANGES
index e39dc2171..57080449d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -14,7 +14,7 @@ Features:
  - Support for games using the tilt sensor
  - Remappable shortcuts for keyboard and gamepad
  - Rewinding of emulation
- - Implemented BIOS routines Diff8bitUnFilterWram, and Diff16bitUnFilter
+ - Implemented BIOS routines Diff8bitUnFilterWram, Diff8bitUnFilterVram, and Diff16bitUnFilter
 Bugfixes:
  - Qt: Fix issue with set frame sizes being the wrong height
  - Qt: Fix emulator crashing when full screen if a game is not running
diff --git a/src/gba/gba-bios.c b/src/gba/gba-bios.c
index 765fb8105..5f3ad806d 100644
--- a/src/gba/gba-bios.c
+++ b/src/gba/gba-bios.c
@@ -477,26 +477,32 @@ static void _unFilter(struct GBA* gba, int inwidth, int outwidth) {
 	uint16_t old = 0;
 	source += 4;
 	while (remaining > 0) {
+		uint16_t new;
 		if (inwidth == 1) {
-			halfword = cpu->memory.loadU8(cpu, source, 0);
+			new = cpu->memory.loadU8(cpu, source, 0);
 		} else {
-			halfword = cpu->memory.loadU16(cpu, source, 0);
+			new = cpu->memory.loadU16(cpu, source, 0);
 		}
-		halfword += old;
+		new += old;
 		if (outwidth > inwidth) {
-			GBALog(gba, GBA_LOG_STUB, "Unimplemented Diff8bitUnFilterVram");
-		} else {
-			if (outwidth == 1) {
-				halfword &= 0xFF;
-				cpu->memory.store8(cpu, dest, halfword, 0);
-			} else {
+			halfword >>= 8;
+			halfword |= (new << 8);
+			if (source & 1) {
 				cpu->memory.store16(cpu, dest, halfword, 0);
+				dest += outwidth;
+				remaining -= outwidth;
 			}
-			old = halfword;
+		} else if (outwidth == 1) {
+			cpu->memory.store8(cpu, dest, new, 0);
 			dest += outwidth;
+			remaining -= outwidth;
+		} else {
+			cpu->memory.store16(cpu, dest, new, 0);
+			dest += outwidth;
+			remaining -= outwidth;
 		}
+		old = new;
 		source += inwidth;
-		remaining -= outwidth;
 	}
 	cpu->gprs[0] = source;
 	cpu->gprs[1] = dest;