From 50ba57db74cef215a2090d56934388575d130324 Mon Sep 17 00:00:00 2001
From: Steins7 <steinsset@gmail.com>
Date: Sat, 21 May 2022 17:45:38 +0200
Subject: [PATCH] Implemented NROM mapper

---
 src/main.rs                    |  4 +-
 src/peripherals/mapper.rs      | 31 ++-------------
 src/peripherals/mapper/nrom.rs | 71 ++++++++++++++++++++++++++++++++++
 3 files changed, 76 insertions(+), 30 deletions(-)
 create mode 100644 src/peripherals/mapper/nrom.rs

diff --git a/src/main.rs b/src/main.rs
index 3dde190..dac5ef1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,7 +6,6 @@ use cpu::Cpu;
 
 mod bus;
 mod peripherals;
-use peripherals::mapper::Nrom;
 mod utils;
 
 fn main() -> Result<(), &'static str> {
@@ -21,6 +20,7 @@ fn main() -> Result<(), &'static str> {
         rc::Rc,
         cell::RefCell,
     };
+    use peripherals::mapper::Nrom128;
 
     // setup
     setup_logger().map_err(|_| "Failed to setup logger")?;
@@ -36,7 +36,7 @@ fn main() -> Result<(), &'static str> {
     let mut renderer = FontRenderer::new(20.0, [0u8, 0, 0]);
 
     // first image
-    let mapper = Rc::new(RefCell::new(Nrom::new()));
+    let mapper = Rc::new(RefCell::new(Nrom128::new(false)));
     let mut cpu = Cpu::new(mapper);
     let mut debug_str = String::new();
     write!(debug_str, "{:#?}", cpu).unwrap();
diff --git a/src/peripherals/mapper.rs b/src/peripherals/mapper.rs
index a25a5a2..c92200b 100644
--- a/src/peripherals/mapper.rs
+++ b/src/peripherals/mapper.rs
@@ -1,5 +1,8 @@
 use super::Peripheral;
 
+mod nrom;
+pub use nrom::Nrom128;
+
 //--Mapper struct-----------------------------------------------------------------------------------
 ///A trait used as API for the different implementations of mappers in cartridges
 ///
@@ -11,32 +14,4 @@ pub trait Mapper: Peripheral {
     fn ppu_read_addr(&self, addr: u16) -> u8;
 }
 
-pub struct Nrom {
-
-}
-
-impl Peripheral for Nrom {
-
-    fn read_addr(&self, _addr: u16) -> u8 {
-        unimplemented!();
-    }
-
-    fn write_addr(&mut self, _addr: u16, _data: u8) {
-        unimplemented!();
-    } 
-}
-
-impl Mapper for Nrom {
-
-    fn ppu_read_addr(&self, _addr: u16) -> u8 {
-        unimplemented!();
-    }
-}
-
-impl Nrom {
-
-    pub fn new() -> Self {
-        unimplemented!();
-    }
-}
 
diff --git a/src/peripherals/mapper/nrom.rs b/src/peripherals/mapper/nrom.rs
new file mode 100644
index 0000000..c638afb
--- /dev/null
+++ b/src/peripherals/mapper/nrom.rs
@@ -0,0 +1,71 @@
+use super::{
+    Mapper,
+    super::{
+        Peripheral,
+        Ram,
+    },
+};
+
+pub struct Nrom128 {
+    prg_rom: Ram<0x4000>,   //16KiB
+    prg_ram: Ram<0x2000>,   //8KiB
+    chr_rom: Ram<0x2000>,   //8KiB
+    v_ram: Ram<0x0800>,     //2KiB
+    vertical: bool,
+}
+
+impl Peripheral for Nrom128 {
+
+    fn read_addr(&self, addr: u16) -> u8 {
+
+        match addr {
+            0x6000..=0x7FFF => self.prg_ram.read_addr(addr - 0x6000),
+            0x8000..=0xBFFF => self.prg_rom.read_addr((addr - 0x6000) % 0x4000), 
+            //mirrored every 16KiB
+            _ => panic!("{}: Invalid address", addr),
+        }
+    }
+
+    fn write_addr(&mut self, addr: u16, data: u8) {
+        
+        match addr {
+            0x6000..=0x7FFF => self.prg_ram.write_addr(addr - 0x6000, data),
+            _ => (), //writes are ignored for rom or invald addresses
+        }
+    } 
+}
+
+impl Mapper for Nrom128 {
+
+    fn ppu_read_addr(&self, addr: u16) -> u8 {
+       
+        match addr {
+            0x0000..=0x1FFF => self.chr_rom.read_addr(addr),
+            0x2000..=0x3EFF => {
+                match self.vertical {
+                    false => match (addr - 0x2000) % 0x0FFF {
+                        0x0000..=0x07FF => self.v_ram.read_addr(addr % 0x0400),
+                        0x0800..=0x0FFF => self.v_ram.read_addr((addr % 0x0400) + 0x0800), 
+                        _ => panic!("Unexpected behaviour"),
+                    },
+                    true => self.v_ram.read_addr(addr % 0x0800),
+                }},
+            _ => panic!("{}: Invalid ppu address", addr),
+        }
+    }
+}
+
+impl Nrom128 {
+
+    pub fn new(vertical: bool) -> Self {
+        
+        Self {
+            prg_rom: Ram::<0x4000>::new(),
+            prg_ram: Ram::<0x2000>::new(),
+            chr_rom: Ram::<0x2000>::new(),
+            v_ram: Ram::<0x0800>::new(),
+            vertical,
+        }
+    }
+}
+