From fac82c2ca11dd9326f58ef0e2d110927e73c7c10 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Tue, 6 Jan 2015 23:07:59 -0800
Subject: [PATCH] GBA BIOS: Implement Diff8bitUnFilterWram and
 Diff16bitUnFilter

---
 CHANGES            |  1 +
 src/gba/gba-bios.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/CHANGES b/CHANGES
index 1397b8f68..74bb16aa2 100644
--- a/CHANGES
+++ b/CHANGES
@@ -14,6 +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
 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 ee7b95533..5227123a4 100644
--- a/src/gba/gba-bios.c
+++ b/src/gba/gba-bios.c
@@ -15,6 +15,7 @@ const uint32_t GBA_DS_BIOS_CHECKSUM = 0xBAAE1880;
 static void _unLz77(struct GBA* gba, uint32_t source, uint32_t dest, int width);
 static void _unHuffman(struct GBA* gba, uint32_t source, uint32_t dest);
 static void _unRl(struct GBA* gba, uint32_t source, uint32_t dest, int width);
+static void _unFilter(struct GBA* gba, uint32_t source, uint32_t dest, int inwidth, int outwidth);
 
 static void _RegisterRamReset(struct GBA* gba) {
 	uint32_t registers = gba->cpu->gprs[0];
@@ -212,6 +213,22 @@ void GBASwi16(struct ARMCore* cpu, int immediate) {
 				break;
 		}
 		break;
+	case 0x16:
+	case 0x17:
+	case 0x18:
+		if (cpu->gprs[0] < BASE_WORKING_RAM) {
+			GBALog(gba, GBA_LOG_GAME_ERROR, "Bad UnFilter source");
+		}
+		switch (cpu->gprs[1] >> BASE_OFFSET) {
+			default:
+				GBALog(gba, GBA_LOG_GAME_ERROR, "Bad UnFilter destination");
+			case REGION_WORKING_RAM:
+			case REGION_WORKING_IRAM:
+			case REGION_VRAM:
+				_unFilter(gba, cpu->gprs[0], cpu->gprs[1], immediate == 0x18 ? 2 : 1, immediate == 0x16 ? 1 : 2);
+				break;
+		}
+		break;
 	case 0x1F:
 		_MidiKey2Freq(gba);
 		break;
@@ -438,3 +455,36 @@ static void _unRl(struct GBA* gba, uint32_t source, uint32_t dest, int width) {
 		}
 	}
 }
+
+static void _unFilter(struct GBA* gba, uint32_t source, uint32_t dest, int inwidth, int outwidth) {
+	struct ARMCore* cpu = gba->cpu;
+	source = source & 0xFFFFFFFC;
+	uint32_t header = cpu->memory.load32(cpu, source, 0);
+	int remaining = header >> 8;
+	// We assume the signature nybble (0x8) is correct
+	uint16_t halfword = 0;
+	uint16_t old = 0;
+	source += 4;
+	while (remaining > 0) {
+		if (inwidth == 1) {
+			halfword = cpu->memory.loadU8(cpu, source, 0);
+		} else {
+			halfword = cpu->memory.loadU16(cpu, source, 0);
+		}
+		halfword += 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 {
+				cpu->memory.store16(cpu, dest, halfword, 0);
+			}
+			old = halfword;
+			dest += outwidth;
+		}
+		source += inwidth;
+		--remaining;
+	}
+}