From b6d479c59502ca758008f63faa7d099ce3d13a03 Mon Sep 17 00:00:00 2001
From: Hojun-Cho <ghwns6743@gmail.com>
Date: Tue, 16 Jul 2024 21:19:27 +0900
Subject: [PATCH] add mbc1

---
 gb.c  | 29 +++++++++++++++++++++++++----
 gb.h  |  2 +-
 mem.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 68 insertions(+), 6 deletions(-)

diff --git a/gb.c b/gb.c
index f3925dd..fcf722e 100644
--- a/gb.c
+++ b/gb.c
@@ -4,6 +4,7 @@
 
 int cpuhalt;
 int backup;
+int savefd = -1;
 u64 clock;
 u8 mbc, feat, mode;
 
@@ -14,7 +15,13 @@ loadrom(const char* file)
   long sz;
   static u8 mbctab[31] = { 0, 1, 1, 1, -1, 2, 2, -1, 0,  0, -1, 6, 6, 6, -1, 3,
                            3, 3, 3, 3, -1, 4, 4, 4,  -1, 5, 5,  5, 5, 5, 5 };
-
+	static u8 feattab[31] = {
+		0, 0, FEATRAM, FEATRAM|FEATBAT, 0, FEATRAM, FEATRAM|FEATBAT, 0,
+		FEATRAM, FEATRAM|FEATBAT, 0, 0, FEATRAM, FEATRAM|FEATBAT, 0, FEATTIM|FEATBAT,
+		FEATTIM|FEATRAM|FEATBAT, 0, FEATRAM, FEATRAM|FEATBAT, 0, 0, FEATRAM, FEATRAM|FEATBAT,
+		0, 0, FEATRAM, FEATRAM|FEATBAT, 0, FEATRAM, FEATRAM|FEATBAT,
+	};
+	
   f = fopen(file, "r");
   if (f == nil)
     panic("can't open %s", file);
@@ -31,11 +38,25 @@ loadrom(const char* file)
   if (rom[0x147] > 0x1F)
     panic("bad cartidge type %d\n", rom[0x147]);
   mbc = mbctab[rom[0x147]];
+	feat = feattab[rom[0x147]];
+	if((feat & FEATRAM) != 0){
+		switch(rom[0x149]){
+		case 0: feat &= ~FEATRAM; break;
+		case 1: nback = 2048; break;
+		case 2: nback = 8192; break;
+		case 3: nback = 32768; break;
+		default: panic("Unkown Ram size %d\n", rom[0x149]);
+		}
+	}
+	back = xalloc(nback);
+	if(nback == 0)
+		nbackbank = 1;
+	else
+		nbackbank = (nback + 8191) / 8192; 
   switch (mbc) {
-    case 0:
+		case 0: case 1:
       break;
-    default:
-      panic("unsupported mbc %d", mbc);
+    default: panic("unsupported mbc %d", mbc);
   }
   if ((rom[0x143] & 0x80) != 0 && (mode & FORCEDMG) == 0)
     mode = CGB | COL;
diff --git a/gb.h b/gb.h
index 1c377e4..b408d20 100644
--- a/gb.h
+++ b/gb.h
@@ -147,7 +147,7 @@ struct Event
 
 extern u8 *rom, *back, reg[256], oam[256];
 extern u8 vram[16384];
-extern int nrom;
+extern int nrom, nback, nbackbank;
 extern u32 pal[64];
 extern u8 dma;
 extern u32 divclock;
diff --git a/mem.c b/mem.c
index f0e20bf..3967f55 100644
--- a/mem.c
+++ b/mem.c
@@ -2,6 +2,8 @@
 
 static int
 mbc0(int a, int _);
+static int
+mbc1(int a, int _);
 
 u8* rom;
 u8 *romb, *vramb, *wramb, *eramb;
@@ -15,7 +17,7 @@ int prish;
 u8 dma;
 u32 moncols[4];
 u32 white;
-int (*mappers[])(int, int) = { mbc0 };
+int (*mappers[])(int, int) = { mbc0, mbc1 };
 int (*mapper)(int, int);
 
 static u8
@@ -192,6 +194,45 @@ mbc0(int a, int _)
   return 0;
 }
 
+static int
+mbc1(int a, int v)
+{
+	static u8 ramen, b0, b1, romram;
+	u16 b;
+
+	if (a < 0) {
+		switch(a) {
+		case INIT: return 0;
+		case SAVE:
+		case RSTR:
+			break;
+		case READ:
+			return -1;
+		default: panic("MBC1 does not have function of %d", a);
+		}
+	}
+	switch (a >> 13) {
+	case 0: ramen = (v & 0xF) == 0xA; break;
+	case 1: v &= 0x1F; b0 = v != 0 ? v : 1; break;
+	case 2: b1 = v & 3; b1 % nbackbank; break;
+	case 3: romram = v & 1; break;
+	}
+	b = b0;
+	if (romram == 0)
+		b |= b1 << 5;
+	b %= nrom >> 14; /* 32KB => 2bank */
+	romb = rom + (b << 14);
+	if (ramen) {
+		if (romram)
+			eramb = back + (b1 << 13);
+		else
+			eramb = back;
+	} else {
+		eramb = nil;
+	}
+	return 0;
+}
+
 void
 meminit(void)
 {