From 6455732043f3cdcb95e87df65e6664a919c26cac Mon Sep 17 00:00:00 2001
From: Kevin Hamacher <kevin.hamacher@rub.de>
Date: Sun, 29 May 2016 18:36:40 +0200
Subject: [PATCH] Add support for MBC1.

TODO: Refactor the cartridge code
---
 src/cartridge.rs | 69 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 67 insertions(+), 2 deletions(-)

diff --git a/src/cartridge.rs b/src/cartridge.rs
index b83b054..edfb9f8 100644
--- a/src/cartridge.rs
+++ b/src/cartridge.rs
@@ -25,6 +25,9 @@ pub struct Cartridge {
 
     ram_size: RamSize,
     rom_banks: u16,
+
+    bank_mode: u8,
+    bank_no_high: u8,
 }
 
 impl Cartridge {
@@ -77,15 +80,18 @@ impl Cartridge {
             ram_size: ram_size,
             rom_banks: rom_banks,
 
-            ram: ram
+            ram: ram,
+            bank_mode: 0,
+            bank_no_high: 0,
         }
     }
 
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub fn read_byte_mbc3(&self, addr: u16) -> u8 {
         match addr {
             0x0000 ... 0x3FFF => self.rom[addr as usize],
             0x4000 ... 0x7FFF => {
                 let addr = addr - 0x4000;
+                println!("BankNo: {:02X}", self.bank_no);
                 let abs_addr: usize = addr as usize + self.bank_no as usize * 0x4000;
                 let val: u8 = self.rom[abs_addr];
                 val
@@ -106,6 +112,43 @@ impl Cartridge {
         }
     }
 
+    pub fn read_byte_mbc1(&self, addr: u16) -> u8 {
+        match addr {
+            0x0000 ... 0x3FFF => self.rom[addr as usize],
+            0x4000 ... 0x7FFF => {
+                let addr = addr - 0x4000;
+                let mut bank: u8 = self.bank_no;
+                if self.bank_mode == 0 {
+                    bank |= self.bank_no_high << 5;
+                }
+                println!("BankNo: {:02X}", bank);
+                let abs_addr: usize = addr as usize + bank as usize * 0x4000;
+                let val: u8 = self.rom[abs_addr];
+                val
+            },
+            0xA000 ... 0xBFFF => {
+                // TODO: Safty checks? Or let rust handle this?
+                let addr = addr - 0xA000;
+                let mut bank: u8 = 0;
+                if self.bank_mode == 1 {
+                    bank = self.bank_no_high
+                }
+
+                self.ram[bank as usize * 0x2000 + addr as usize]
+            }
+            _ => {
+                panic!("Cartride: Unable to read from {:04X}", addr);
+            }
+        }
+    }
+    pub fn read_byte(&self, addr: u16) -> u8{
+        match self.mbc_type {
+            MemoryBankControllerType::MBC1 => self.read_byte_mbc1(addr),
+            MemoryBankControllerType::MBC3 | MemoryBankControllerType::None => self.read_byte_mbc3(addr),
+            _ => panic!("MBC not supported.")
+        }
+    }
+
     fn write_byte_none(&mut self, addr: u16, val: u8) {
         match addr {
             0xA000 ... 0xBFFF => {
@@ -116,6 +159,27 @@ impl Cartridge {
         }
     }
 
+    fn write_byte_mbc1(&mut self, addr: u16, val: u8) {
+        match addr {
+            0x2000 ... 0x3FFF => {
+                // Write low bits of addr.
+                self.bank_no &= 0xE0;
+                self.bank_no |= val & 0x1F;
+
+                // Can't select 0x00, 0x20, 0x40, 0x60. Adapt it to 0x01, 0x21, 0x41, 0x61
+                if self.bank_no & 0x1F == 0 {
+                    self.bank_no |= 1;
+                }
+            }
+            0x4000 ... 0x5FFF => {
+                self.bank_no_high = val & 3;
+            }
+            0x6000 ... 0x7FFF => {
+                self.bank_mode = val & 1;
+            }
+            _ => panic!("MBC1 Write {:02X} to {:04X} unsupported", val, addr),
+        }
+    }
     fn write_byte_mbc3(&mut self, addr: u16, val: u8) {
         match addr {
             0x0000 ... 0x1FFF => {
@@ -154,6 +218,7 @@ impl Cartridge {
     pub fn write_byte(&mut self, addr: u16, val: u8) {
         match self.mbc_type {
             MemoryBankControllerType::None => self.write_byte_none(addr, val),
+            MemoryBankControllerType::MBC1 => self.write_byte_mbc1(addr, val),
             MemoryBankControllerType::MBC3 => self.write_byte_mbc3(addr, val),
             _ => panic!("MBC not supported.")
         }