Added GPU "skeleton"

src/cpu.rs

@@ -1,4 +1,4 @@
-use crate::common::{merge_two_u8s_into_u16, Operator, split_u16_into_two_u8s};
+use crate::common::{merge_two_u8s_into_u16, split_u16_into_two_u8s, Operator};
 use crate::consts::bus::IO_START;
 use crate::registers::OneByteRegister;
 use crate::GameBoy;
@@ -28,12 +28,7 @@ type Cycles = u8;
 
 // INC/DEC function
 impl GameBoy {
-    fn increment_r(
-        &mut self,
-        register: OneByteRegister,
-        operator: Operator,
-        amount: u8,
-    ) {
+    fn increment_r(&mut self, register: OneByteRegister, operator: Operator, amount: u8) {
         let register = self.registers.get_r(register);
 
         *register = match operator {
@@ -48,11 +43,7 @@ impl GameBoy {
 
 // LD functions
 impl GameBoy {
-    fn load_r_into_r(
-        &mut self,
-        register_to_be_loaded: OneByteRegister,
-        register: OneByteRegister,
-    ) {
+    fn load_r_into_r(&mut self, register_to_be_loaded: OneByteRegister, register: OneByteRegister) {
         let register_to_be_loaded = *self.registers.get_r(register_to_be_loaded);
         let register = self.registers.get_r(register);
 
@@ -68,7 +59,8 @@ impl GameBoy {
 
     fn load_r_into_io(&mut self, register: OneByteRegister) {
         let register = *self.registers.get_r(register);
-        self.bus.write_byte((IO_START + self.next(1) as usize) as u16, register);
+        self.bus
+            .write_byte((IO_START + self.next(1) as usize) as u16, register);
     }
 
     fn load_io_into_r(&mut self, register: OneByteRegister) {
@@ -82,17 +74,20 @@ impl GameBoy {
 // CP functions
 impl GameBoy {
     fn compare_ra_to_i(&mut self) {
-        self.flags.update_zero_flag(self.registers.a.wrapping_sub(self.next(1)));
+        self.flags
+            .update_zero_flag(self.registers.a.wrapping_sub(self.next(1)));
     }
 
     fn compare_ra_to_r(&mut self, register: OneByteRegister) {
         let register = *self.registers.get_r(register);
-        self.flags.update_zero_flag(self.registers.a.wrapping_sub(register));
+        self.flags
+            .update_zero_flag(self.registers.a.wrapping_sub(register));
     }
 
     fn compare_ra_to_ram(&mut self, address: u16) {
         let ram = self.bus.read(address);
-        self.flags.update_zero_flag(self.registers.a.wrapping_sub(ram));
+        self.flags
+            .update_zero_flag(self.registers.a.wrapping_sub(ram));
     }
 }
 

src/gpu.rs

@@ -0,0 +1,86 @@
+#![allow(unused)]
+
+use std::marker::Copy;
+
+use crate::GameBoy;
+
+#[derive(PartialEq)]
+enum GPUState {
+    OAMSearch,
+    PixelTransfer,
+    HBlank,
+    VBlank,
+}
+
+#[derive(Clone, Copy)]
+enum Source {
+    Background,
+    Window,
+}
+
+#[derive(Clone, Copy)]
+enum Color {
+    One,
+    Two,
+    Three,
+    Four,
+}
+
+#[derive(Clone, Copy)]
+struct PixelData {
+    source: Source,
+    color: Color,
+}
+
+pub struct GPU {
+    state: GPUState,
+
+    /// The buffer of the pixels to push
+    fifo: [Option<PixelData>; 8],
+}
+
+impl GPU {
+    pub(crate) fn new() -> Self {
+        Self {
+            state: GPUState::OAMSearch,
+            fifo: [None; 8],
+        }
+    }
+}
+
+// TODO: During pixel transfer mode, the vram should not be accessible
+// TODO: During pixel transfer mode and oam search mode, the oam should not be accessible
+
+impl GameBoy {
+    /// We need to search in the Object Attribute Memory the sprites that are actually
+    /// visible in the current line
+    fn oam_search(&mut self) {
+        // TODO
+        self.gpu.state = GPUState::PixelTransfer;
+    }
+
+    fn pixel_transfer(&mut self) {
+        // TODO
+        self.gpu.state = GPUState::HBlank;
+    }
+
+    fn hblank(&mut self) {
+        // TODO
+        self.gpu.state = GPUState::VBlank;
+    }
+
+    fn vblank(&mut self) {
+        // TODO
+        self.gpu.state = GPUState::OAMSearch;
+    }
+
+    #[rustfmt::skip]
+    pub(crate) fn gpu_step(&mut self) {
+        match self.gpu.state {
+            GPUState::OAMSearch => self.oam_search(),
+            GPUState::PixelTransfer => self.pixel_transfer(),
+            GPUState::HBlank => self.hblank(),
+            GPUState::VBlank => self.vblank(),
+        }
+    }
+}

src/lib.rs

@@ -5,6 +5,7 @@ use common::merge_two_u8s_into_u16;
 use consts::bus::ROM_SIZE;
 use errors::EmuError;
 use flags::Flags;
+use gpu::GPU;
 use registers::Registers;
 use screen::Screen;
 
@@ -14,6 +15,7 @@ mod consts;
 mod cpu;
 mod errors;
 mod flags;
+mod gpu;
 mod interrupts;
 mod registers;
 mod screen;
@@ -26,6 +28,7 @@ pub struct GameBoy {
     pub screen: Screen,
     pub registers: Registers,
     pub flags: Flags,
+    pub gpu: GPU,
 
     /// Some gameboy opcodes have a prefix `0xCB`
     pub is_cb: bool,
@@ -41,6 +44,7 @@ impl GameBoy {
             screen: Screen::new(),
             registers: Registers::new(),
             flags: Flags::new(),
+            gpu: GPU::new(),
             is_cb: false,
             current_opcode: None,
         })
@@ -52,6 +56,7 @@ impl GameBoy {
             screen: Screen::new(),
             registers: Registers::new(),
             flags: Flags::new(),
+            gpu: GPU::new(),
             is_cb: false,
             current_opcode: None,
         }
@@ -78,7 +83,10 @@ impl GameBoy {
         self.is_cb = false;
 
         // CPU - Interrupts
-        self.execute_interrupts()
+        self.execute_interrupts();
+
+        // GPU
+        self.gpu_step();
     }
 }