Cartridge: added support for switchable mirroring

- properly handled the mirroring flags in INES header

cartridge/src/cartridge.rs

@@ -1,5 +1,5 @@
 use super::{error::CartridgeError, mapper::Mapper, mappers::*};
-use common::{Bus, Device};
+use common::{Bus, Device, MirroringMode, MirroringProvider};
 use std::{
     fs::File,
     io::{Read, Seek, SeekFrom},
@@ -13,7 +13,7 @@ pub struct Cartridge {
     mirroring_vertical: bool,
     contain_sram: bool,
     contain_trainer: bool,
-    ignore_mirroring: bool,
+    use_4_screen_mirroring: bool,
     vs_unisystem: bool,        // don't know what is this (flag 7)
     _playchoice_10_hint: bool, // not used
     is_nes_2: bool,
@@ -43,7 +43,7 @@ impl Cartridge {
         header[6] >>= 1;
         let contain_trainer = header[6] & 1 != 0;
         header[6] >>= 1;
-        let ignore_mirroring = header[6] & 1 != 0;
+        let use_4_screen_mirroring = header[6] & 1 != 0;
         header[6] >>= 1;
         let lower_mapper = header[6]; // the rest
 
@@ -104,7 +104,7 @@ impl Cartridge {
                 mirroring_vertical,
                 contain_sram,
                 contain_trainer,
-                ignore_mirroring,
+                use_4_screen_mirroring,
                 vs_unisystem,
                 _playchoice_10_hint,
                 is_nes_2,
@@ -188,3 +188,21 @@ impl Bus for Cartridge {
         }
     }
 }
+
+impl MirroringProvider for Cartridge {
+    fn mirroring_mode(&self) -> MirroringMode {
+        if self.use_4_screen_mirroring {
+            MirroringMode::FourScreen
+        } else {
+            if self.mapper.is_hardwired_mirrored() {
+                if self.mirroring_vertical {
+                    MirroringMode::Vertical
+                } else {
+                    MirroringMode::Horizontal
+                }
+            } else {
+                self.mapper.nametable_mirroring()
+            }
+        }
+    }
+}

cartridge/src/mapper.rs

@@ -1,7 +1,9 @@
-use common::Device;
+use common::{Device, MirroringMode};
 
 pub trait Mapper {
     fn init(&mut self, pgr_count: u8, chr_count: u8);
     fn map_read(&self, address: u16, device: Device) -> usize;
     fn map_write(&mut self, address: u16, data: u8, device: Device);
+    fn is_hardwired_mirrored(&self) -> bool;
+    fn nametable_mirroring(&self) -> MirroringMode;
 }

cartridge/src/mappers/mapper0.rs

@@ -1,5 +1,5 @@
 use crate::mapper::Mapper;
-use common::Device;
+use common::{Device, MirroringMode};
 
 pub struct Mapper0 {
     has_32kb_prg_rom: bool,
@@ -60,4 +60,12 @@ impl Mapper for Mapper0 {
     fn map_write(&mut self, _: u16, _: u8, _: Device) {
         // nothing
     }
+
+    fn is_hardwired_mirrored(&self) -> bool {
+        true
+    }
+
+    fn nametable_mirroring(&self) -> MirroringMode {
+        unreachable!()
+    }
 }

cartridge/src/mappers/mapper1.rs

@@ -1,5 +1,5 @@
 use crate::mapper::Mapper;
-use common::Device;
+use common::{Device, MirroringMode};
 
 // FIXME: add support for 512kb as now only support 256kb
 pub struct Mapper1 {
@@ -66,7 +66,6 @@ impl Mapper1 {
         self.writing_shift_register = 0b10000;
     }
 
-    // FIXME: handle mirroring from here, and add support to switchable mirroring modes
     fn get_mirroring(&self) -> u8 {
         self.control_register & 0b00011
     }
@@ -216,4 +215,17 @@ impl Mapper for Mapper1 {
             }
         }
     }
+
+    fn is_hardwired_mirrored(&self) -> bool {
+        false
+    }
+
+    fn nametable_mirroring(&self) -> MirroringMode {
+        [
+            MirroringMode::SingleScreenLowBank,
+            MirroringMode::Horizontal,
+            MirroringMode::Vertical,
+            MirroringMode::Horizontal,
+        ][self.get_mirroring() as usize]
+    }
 }

cartridge/src/mappers/mapper2.rs

@@ -1,5 +1,5 @@
 use crate::mapper::Mapper;
-use common::Device;
+use common::{Device, MirroringMode};
 
 pub struct Mapper2 {
     prg_top_bank: u8,
@@ -65,4 +65,12 @@ impl Mapper for Mapper2 {
             }
         }
     }
+
+    fn is_hardwired_mirrored(&self) -> bool {
+        true
+    }
+
+    fn nametable_mirroring(&self) -> MirroringMode {
+        unreachable!()
+    }
 }

cartridge/src/mappers/mapper3.rs

@@ -1,5 +1,5 @@
 use crate::mapper::Mapper;
-use common::Device;
+use common::{Device, MirroringMode};
 
 pub struct Mapper3 {
     has_32kb_prg_rom: bool,
@@ -82,4 +82,12 @@ impl Mapper for Mapper3 {
             }
         }
     }
+
+    fn is_hardwired_mirrored(&self) -> bool {
+        true
+    }
+
+    fn nametable_mirroring(&self) -> MirroringMode {
+        unreachable!()
+    }
 }

cartridge/src/mappers/mapper4.rs

@@ -1,5 +1,5 @@
 use crate::mapper::Mapper;
-use common::Device;
+use common::{Device, MirroringMode};
 
 pub struct Mapper4 {
     /// ($8000-$9FFE, even)
@@ -239,4 +239,16 @@ impl Mapper for Mapper4 {
             }
         }
     }
+
+    fn is_hardwired_mirrored(&self) -> bool {
+        false
+    }
+
+    fn nametable_mirroring(&self) -> MirroringMode {
+        if self.mirroring_vertical {
+            MirroringMode::Vertical
+        } else {
+            MirroringMode::Horizontal
+        }
+    }
 }

common/src/lib.rs

@@ -1,4 +1,7 @@
 mod bus;
+mod mirroring;
+
 pub mod interconnection;
 
 pub use bus::{Bus, Device};
+pub use mirroring::{MirroringMode, MirroringProvider};

common/src/mirroring.rs

@@ -0,0 +1,12 @@
+#[derive(Debug, Copy, Clone)]
+pub enum MirroringMode {
+    Vertical,
+    Horizontal,
+    SingleScreenLowBank,
+    SingleScreenHighBank,
+    FourScreen,
+}
+
+pub trait MirroringProvider {
+    fn mirroring_mode(&self) -> MirroringMode;
+}

nes_test/src/nes.rs

@@ -56,10 +56,10 @@ impl CPUBus {
 }
 
 impl PPUBus {
-    pub fn new(cartridge: Rc<RefCell<Cartridge>>, is_vertical_mirroring: bool) -> Self {
+    pub fn new(cartridge: Rc<RefCell<Cartridge>>) -> Self {
         PPUBus {
-            cartridge,
-            vram: VRam::new(is_vertical_mirroring),
+            cartridge: cartridge.clone(),
+            vram: VRam::new(cartridge.clone()),
             palettes: Palette::new(),
         }
     }
@@ -137,10 +137,7 @@ impl NES {
     pub fn new(filename: &str) -> Result<Self, CartridgeError> {
         let cartridge = Cartridge::from_file(File::open(filename)?)?;
         let cartridge = Rc::new(RefCell::new(cartridge));
-        let ppubus = PPUBus::new(
-            cartridge.clone(),
-            cartridge.borrow().is_vertical_mirroring(),
-        );
+        let ppubus = PPUBus::new(cartridge.clone());
 
         let tv = TV::new(TV_WIDTH, TV_HEIGHT);
         let image = tv.get_image_clone();

ppu2c02/src/tests.rs

@@ -77,10 +77,10 @@ mod ppu_tests {
     }
 
     impl PPUBus {
-        pub fn new(cartridge: Rc<RefCell<Cartridge>>, is_vertical_mirroring: bool) -> Self {
+        pub fn new(cartridge: Rc<RefCell<Cartridge>>) -> Self {
             PPUBus {
-                cartridge,
-                vram: VRam::new(is_vertical_mirroring),
+                cartridge: cartridge.clone(),
+                vram: VRam::new(cartridge.clone()),
                 palettes: Palette::new(),
             }
         }
@@ -153,10 +153,7 @@ mod ppu_tests {
         fn new(filename: &str) -> Result<Self, CartridgeError> {
             let cartridge = Rc::new(RefCell::new(Cartridge::from_file(File::open(filename)?)?));
 
-            let ppubus = PPUBus::new(
-                cartridge.clone(),
-                cartridge.borrow().is_vertical_mirroring(),
-            );
+            let ppubus = PPUBus::new(cartridge.clone());
 
             let tv = TV::new(TV_WIDTH, TV_HEIGHT);
             let tv_image = tv.get_image_clone();

ppu2c02/src/vram.rs

@@ -1,26 +1,17 @@
-use common::{Bus, Device};
-
-enum MirroringMode {
-    Vertical,
-    Horizontal,
-    // TODO: add other strange mirroring modes
-}
+use common::{Bus, Device, MirroringMode, MirroringProvider};
+use std::{cell::RefCell, rc::Rc};
 
 pub struct VRam {
     // half of this memory (or depending on mirroring mode) is unused
     vram_data: [u8; 0x1000],
-    mirroring_mode: MirroringMode,
+    mirroring_provider: Rc<RefCell<dyn MirroringProvider>>,
 }
 
 impl VRam {
-    pub fn new(is_vertical_mirroring: bool) -> Self {
+    pub fn new(mirroring_provider: Rc<RefCell<dyn MirroringProvider>>) -> Self {
         Self {
             vram_data: [0; 0x1000],
-            mirroring_mode: if is_vertical_mirroring {
-                MirroringMode::Vertical
-            } else {
-                MirroringMode::Horizontal
-            },
+            mirroring_provider,
         }
     }
 
@@ -40,9 +31,13 @@ impl VRam {
     fn map_address(&self, address: u16) -> u16 {
         assert!(address >= 0x2000 && address < 0x3000);
 
-        match self.mirroring_mode {
+        match self.mirroring_provider.borrow().mirroring_mode() {
             MirroringMode::Vertical => address & 0x7FF,
             MirroringMode::Horizontal => address & 0xBFF,
+            _ => unimplemented!(
+                "mirroring mode {:?}",
+                self.mirroring_provider.borrow().mirroring_mode()
+            ),
         }
     }
 }