feat: implement cartridge saving

Implemented for MBC1, MBC2, MBC3 and MBC5

Cargo.lock

@@ -592,6 +592,27 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "directories-next"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "339ee130d97a610ea5a5872d2bbb130fdf68884ff09d3028b81bec8a1ac23bbc"
+dependencies = [
+ "cfg-if 1.0.0",
+ "dirs-sys-next",
+]
+
+[[package]]
+name = "dirs-sys-next"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ebda144c4fe02d1f7ea1a7d9641b6fc6b580adcfa024ae48797ecdeb6825b4d"
+dependencies = [
+ "libc",
+ "redox_users",
+ "winapi",
+]
+
 [[package]]
 name = "discard"
 version = "1.0.4"
@@ -671,6 +692,7 @@ dependencies = [
  "anyhow",
  "bitfield",
  "clap",
+ "directories-next",
  "gilrs",
  "pixels",
  "rodio",
@@ -679,6 +701,17 @@ dependencies = [
  "winit_input_helper",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcd999463524c52659517fe2cea98493cfe485d10565e7b0fb07dbba7ad2753"
+dependencies = [
+ "cfg-if 1.0.0",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "gilrs"
 version = "0.8.1"
@@ -1493,6 +1526,16 @@ dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "redox_users"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "528532f3d801c87aec9def2add9ca802fe569e44a544afe633765267840abe64"
+dependencies = [
+ "getrandom",
+ "redox_syscall",
+]
+
 [[package]]
 name = "regex"
 version = "1.5.4"
@@ -1916,6 +1959,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.10.2+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6"
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.77"

Cargo.toml

@@ -17,6 +17,7 @@ winit = "^0.25"
 winit_input_helper = "^0.10"
 rodio = "^0.14"
 rtrb = "^0.1.4"
+directories-next = "2.0.0"
 
 [profile.release]
 debug = true

src/bus.rs

@@ -90,6 +90,16 @@ impl Bus {
     pub(crate) fn joyp_mut(&mut self) -> &mut Joypad {
         &mut self.joypad
     }
+
+    #[inline]
+    pub(crate) fn cart(&self) -> Option<&Cartridge> {
+        self.cart.as_ref()
+    }
+
+    #[inline]
+    pub(crate) fn cart_mut(&mut self) -> Option<&mut Cartridge> {
+        self.cart.as_mut()
+    }
 }
 
 impl Bus {

src/cartridge.rs

@@ -24,6 +24,14 @@ impl Cartridge {
         }
     }
 
+    pub(crate) fn ext_ram(&self) -> Option<&[u8]> {
+        self.mbc.ext_ram()
+    }
+
+    pub(crate) fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        self.mbc.write_ext_ram(memory)
+    }
+
     fn detect_mbc(memory: &[u8]) -> Box<dyn MBCIo> {
         let ram_size = Self::detect_ram_info(memory);
         let rom_size = Self::detect_rom_info(memory);
@@ -38,13 +46,13 @@ impl Cartridge {
         match mbc_kind {
             MBCKind::None => Box::new(NoMBC),
             MBCKind::MBC1 => Box::new(MBC1::new(ram_size, rom_size)),
-            MBCKind::MBC1WithBattery => Box::new(MBC1::new(ram_size, rom_size)), // TODO: Implement Saving
+            MBCKind::MBC1WithBattery => Box::new(MBC1::with_battery(ram_size, rom_size)), // TODO: Implement Saving
             MBCKind::MBC2 => Box::new(MBC2::new(rom_cap)),
-            MBCKind::MBC2WithBattery => Box::new(MBC2::new(rom_cap)), // TODO: Implement Saving
+            MBCKind::MBC2WithBattery => Box::new(MBC2::with_battery(rom_cap)), // TODO: Implement Saving
             MBCKind::MBC3 => Box::new(MBC3::new(ram_cap)),
-            MBCKind::MBC3WithBattery => Box::new(MBC3::new(ram_cap)), // TODO: Implement Saving
+            MBCKind::MBC3WithBattery => Box::new(MBC3::with_battery(ram_cap)), // TODO: Implement Saving
             MBCKind::MBC5 => Box::new(MBC5::new(ram_cap, rom_cap)),
-            MBCKind::MBC5WithBattery => Box::new(MBC5::new(ram_cap, rom_cap)), // TDO: Implement Saving
+            MBCKind::MBC5WithBattery => Box::new(MBC5::with_battery(ram_cap, rom_cap)), // TDO: Implement Saving
         }
     }
 
@@ -117,6 +125,8 @@ struct MBC1 {
     memory: Vec<u8>,
     rom_size: RomSize,
     mem_enabled: bool,
+
+    has_battery: bool,
 }
 
 impl MBC1 {
@@ -129,6 +139,20 @@ impl MBC1 {
             ram_bank: Default::default(),
             mode: Default::default(),
             mem_enabled: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(ram_size: RamSize, rom_size: RomSize) -> Self {
+        Self {
+            rom_bank: 0x01,
+            memory: vec![0; ram_size.capacity() as usize],
+            ram_size,
+            rom_size,
+            ram_bank: Default::default(),
+            mode: Default::default(),
+            mem_enabled: Default::default(),
+            has_battery: true,
         }
     }
 
@@ -197,6 +221,21 @@ impl MBC1 {
     }
 }
 
+impl Savable for MBC1 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(&self.memory),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
+        }
+    }
+}
+
 impl MBCIo for MBC1 {
     fn handle_read(&self, addr: u16) -> MBCResult {
         use MBCResult::*;
@@ -256,6 +295,8 @@ struct MBC3 {
 
     // RTC Data Latch Previous Write
     prev_latch_write: Option<u8>,
+
+    has_battery: bool,
 }
 
 impl MBC3 {
@@ -267,6 +308,34 @@ impl MBC3 {
             devs_enabled: Default::default(),
             mapped: Default::default(),
             prev_latch_write: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(ram_cap: usize) -> Self {
+        Self {
+            memory: vec![0; ram_cap],
+            rom_bank: Default::default(),
+            ram_bank: Default::default(),
+            devs_enabled: Default::default(),
+            mapped: Default::default(),
+            prev_latch_write: Default::default(),
+            has_battery: true,
+        }
+    }
+}
+
+impl Savable for MBC3 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(&self.memory),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
         }
     }
 }
@@ -342,9 +411,10 @@ struct MBC5 {
     ram_bank: u8,
 
     rom_cap: usize,
-
     memory: Vec<u8>,
     mem_enabled: bool,
+
+    has_battery: bool,
 }
 
 impl MBC5 {
@@ -355,6 +425,18 @@ impl MBC5 {
             rom_cap,
             ram_bank: Default::default(),
             mem_enabled: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(ram_cap: usize, rom_cap: usize) -> Self {
+        Self {
+            rom_bank: 0x01,
+            memory: vec![0; ram_cap],
+            rom_cap,
+            ram_bank: Default::default(),
+            mem_enabled: Default::default(),
+            has_battery: true,
         }
     }
 
@@ -363,6 +445,21 @@ impl MBC5 {
     }
 }
 
+impl Savable for MBC5 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(&self.memory),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
+        }
+    }
+}
+
 impl MBCIo for MBC5 {
     fn handle_read(&self, addr: u16) -> MBCResult {
         use MBCResult::*;
@@ -401,6 +498,7 @@ struct MBC2 {
     mem_enabled: bool,
 
     rom_cap: usize,
+    has_battery: bool,
 }
 
 impl MBC2 {
@@ -410,8 +508,19 @@ impl MBC2 {
         Self {
             rom_bank: 0x01,
             memory: Box::new([0; Self::RAM_SIZE]),
-            mem_enabled: Default::default(),
             rom_cap,
+            mem_enabled: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(rom_cap: usize) -> Self {
+        Self {
+            rom_bank: 0x01,
+            memory: Box::new([0; Self::RAM_SIZE]),
+            rom_cap,
+            mem_enabled: Default::default(),
+            has_battery: true,
         }
     }
 
@@ -420,6 +529,21 @@ impl MBC2 {
     }
 }
 
+impl Savable for MBC2 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(self.memory.as_ref()),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
+        }
+    }
+}
+
 impl MBCIo for MBC2 {
     fn handle_read(&self, addr: u16) -> MBCResult {
         use MBCResult::*;
@@ -457,6 +581,16 @@ impl MBCIo for MBC2 {
 #[derive(Debug)]
 struct NoMBC;
 
+impl Savable for NoMBC {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        None
+    }
+
+    fn write_ext_ram(&mut self, _memory: Vec<u8>) {
+        // Nothing Happens Here
+    }
+}
+
 impl MBCIo for NoMBC {
     fn handle_read(&self, addr: u16) -> MBCResult {
         MBCResult::Address(addr as usize)
@@ -467,7 +601,7 @@ impl MBCIo for NoMBC {
     }
 }
 
-trait MBCIo {
+trait MBCIo: Savable {
     fn handle_read(&self, addr: u16) -> MBCResult;
     fn handle_write(&mut self, addr: u16, byte: u8);
 }
@@ -607,3 +741,8 @@ impl Default for Box<dyn MBCIo> {
         Box::new(NoMBC)
     }
 }
+
+trait Savable {
+    fn ext_ram(&self) -> Option<&[u8]>;
+    fn write_ext_ram(&mut self, memory: Vec<u8>);
+}

src/emu.rs

@@ -2,7 +2,11 @@ use crate::apu::gen::SampleProducer;
 use crate::cpu::Cpu;
 use crate::joypad::{self, Joypad};
 use crate::{Cycle, GB_HEIGHT, GB_WIDTH};
+use clap::crate_name;
 use gilrs::Gilrs;
+use std::fs::File;
+use std::io::{Read, Write};
+use std::path::PathBuf;
 use std::time::Duration;
 use winit_input_helper::WinitInputHelper;
 
@@ -50,7 +54,7 @@ impl Emulator {
     }
 
     fn load_cart(&mut self, rom: Vec<u8>) {
-        self.cpu.bus_mut().load_cart(rom)
+        self.cpu.bus_mut().load_cart(rom);
     }
 
     #[inline]
@@ -65,6 +69,51 @@ impl Emulator {
     pub fn title(&self) -> &str {
         self.cpu.bus().cart_title().unwrap_or(DEFAULT_TITLE)
     }
+
+    pub fn try_write_sav(&self) -> std::io::Result<()> {
+        if let Some(ext_ram) = self.cpu.bus().cart().map(|c| c.ext_ram()).flatten() {
+            if let Some(title) = self.cpu.bus().cart_title() {
+                let mut save_path = Self::data_path().unwrap_or_else(|| PathBuf::from("."));
+                save_path.push(title);
+                save_path.set_extension("sav");
+
+                let mut file = File::create(save_path)?;
+                file.write_all(ext_ram)?;
+            }
+        }
+
+        Ok(())
+    }
+
+    pub fn try_load_sav(&mut self) -> std::io::Result<()> {
+        if let Some(cart) = self.cpu.bus_mut().cart_mut() {
+            if let Some(title) = cart.title() {
+                let mut save_path = Self::data_path().unwrap_or_else(|| PathBuf::from("."));
+                save_path.push(title);
+                save_path.set_extension("sav");
+
+                if let Ok(mut file) = File::open(save_path) {
+                    let mut memory = Vec::new();
+                    file.read_to_end(&mut memory)?;
+
+                    cart.write_ext_ram(memory);
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    fn data_path() -> Option<PathBuf> {
+        match directories_next::ProjectDirs::from("dev", "musuka", crate_name!()) {
+            Some(dirs) => {
+                let data_local = dirs.data_local_dir();
+                std::fs::create_dir_all(data_local).ok()?;
+                Some(data_local.to_path_buf())
+            }
+            None => None,
+        }
+    }
 }
 
 pub mod build {

src/main.rs

@@ -49,6 +49,9 @@ fn main() -> Result<()> {
     }
 
     let mut emu = emu_build.finish();
+
+    // Load Save file if it exists
+    emu.try_load_sav().expect("Load save if exists");
     let rom_title = emu.title();
 
     let mut gamepad = Gilrs::new().expect("Initialize Controller Support");
@@ -96,6 +99,8 @@ fn main() -> Result<()> {
                 .map_err(|e| anyhow!("pixels.render() failed: {}", e))
                 .is_err()
             {
+                emu.try_write_sav().expect("Write game save if need be");
+
                 *control_flow = ControlFlow::Exit;
                 return;
             }
@@ -103,6 +108,8 @@ fn main() -> Result<()> {
 
         if input.update(&event) {
             if input.key_pressed(VirtualKeyCode::Escape) || input.quit() {
+                emu.try_write_sav().expect("Write game save if need be");
+
                 *control_flow = ControlFlow::Exit;
                 return;
             }