From 93a839f52a1748c7768c80968571a9d42ef8fbec Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Sat, 27 Feb 2016 01:12:23 -0800
Subject: [PATCH] GB Memory: Clean up MBC1

---
 src/gb/memory.c | 20 ++++++++++++++++++--
 src/gb/memory.h |  5 +++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/gb/memory.c b/src/gb/memory.c
index dde742bc8..1e65a558d 100644
--- a/src/gb/memory.c
+++ b/src/gb/memory.c
@@ -438,8 +438,8 @@ static void _switchBank(struct GBMemory* memory, int bank) {
 	size_t bankStart = bank * GB_SIZE_CART_BANK0;
 	if (bankStart + GB_SIZE_CART_BANK0 > memory->romSize) {
 		mLOG(GB_MBC, GAME_ERROR, "Attempting to switch to an invalid ROM bank: %0X", bank);
-		bankStart &= (GB_SIZE_CART_BANK0 - 1);
-		bank /= GB_SIZE_CART_BANK0;
+		bankStart &= (memory->romSize - 1);
+		bank = bankStart / GB_SIZE_CART_BANK0;
 	}
 	memory->romBank = &memory->rom[bankStart];
 	memory->currentBank = bank;
@@ -496,6 +496,22 @@ void _GBMBC1(struct GBMemory* memory, uint16_t address, uint8_t value) {
 		}
 		_switchBank(memory, bank | (memory->currentBank & 0x60));
 		break;
+	case 0x2:
+		bank &= 3;
+		if (!memory->mbcState.mbc1.mode) {
+			_switchBank(memory, (bank << 5) | (memory->currentBank & 0x1F));
+		} else {
+			_switchSramBank(memory, bank);
+		}
+		break;
+	case 0x3:
+		memory->mbcState.mbc1.mode = value & 1;
+		if (memory->mbcState.mbc1.mode) {
+			_switchBank(memory, memory->currentBank & 0x1F);
+		} else {
+			_switchSramBank(memory, 0);
+		}
+		break;
 	default:
 		// TODO
 		mLOG(GB_MBC, STUB, "MBC1 unknown address: %04X:%02X", address, value);
diff --git a/src/gb/memory.h b/src/gb/memory.h
index f3b25a162..ac8c09124 100644
--- a/src/gb/memory.h
+++ b/src/gb/memory.h
@@ -90,6 +90,10 @@ enum GBMBC7MachineState {
 	GBMBC7_STATE_WRITE = 8,
 };
 
+struct GBMBC1State {
+	int mode;
+};
+
 struct GBMBC7State {
 	enum GBMBC7MachineState state;
 	uint32_t sr;
@@ -101,6 +105,7 @@ struct GBMBC7State {
 };
 
 union GBMBCState {
+	struct GBMBC1State mbc1;
 	struct GBMBC7State mbc7;
 };