feat: support for tile set storage

src/mmu.rs

@@ -113,6 +113,9 @@ impl Mmu {
             0x8000 | 0x9000 => {
                 println!("WRITING TO VRAM");
                 self.ppu.vram[(addr & 0x1fff) as usize] = value;
+                if addr < 0x9800 {
+                    self.ppu.update_tile(addr, value);
+                }
             }
             // External RAM (8k)
             0xa000 | 0xb000 => {

src/ppu.rs

@@ -2,7 +2,15 @@ pub const VRAM_SIZE: usize = 8192;
 pub const HRAM_SIZE: usize = 128;
 pub const PALETTE_SIZE: usize = 4;
 pub const RGBA_SIZE: usize = 4;
+
+/// The number of tiles that can be store in Game Boy's
+/// VRAM memory according to specifications.
+pub const TILE_COUNT: usize = 384;
+
+/// The width of the Game Boy screen in pixels.
 pub const SCREEN_WIDTH: usize = 160;
+
+/// The height of the Game Boy screen in pixels.
 pub const SCREEN_HEIGHT: usize = 154;
 
 /// Represents the Game Boy PPU (Pixel Processing Unit) and controls
@@ -24,6 +32,10 @@ pub struct Ppu {
     /// the sprites are going to be stored.
     pub vram: [u8; VRAM_SIZE],
     pub hram: [u8; HRAM_SIZE],
+    /// The current set of processed tiles that are store in the
+    /// PPU related structures.
+    tiles: [[[u8; 8]; 8]; TILE_COUNT],
+    /// The palette of colors that is currently loaded in Game Boy.
     palette: [[u8; RGBA_SIZE]; PALETTE_SIZE],
     /// The scroll Y register that controls the Y offset
     /// of the background.
@@ -60,6 +72,7 @@ impl Ppu {
             frame_buffer: [0u8; SCREEN_WIDTH * SCREEN_HEIGHT],
             vram: [0u8; VRAM_SIZE],
             hram: [0u8; HRAM_SIZE],
+            tiles: [[[0u8; 8]; 8]; TILE_COUNT],
             palette: [[0u8; RGBA_SIZE]; PALETTE_SIZE],
             scy: 0x0,
             scx: 0x0,
@@ -165,6 +178,28 @@ impl Ppu {
         }
     }
 
+    pub fn update_tile(&mut self, addr: u16, _value: u8) {
+        let addr = addr & 0x1ffe;
+        let tile_index = (addr >> 4) & 0x01ff;
+        let y = (addr >> 1) & 0x0007;
+
+        let mut mask;
+
+        for x in 0..8 {
+            mask = 1 << (7 - x);
+            self.tiles[tile_index as usize][y as usize][x as usize] =
+                if self.vram[addr as usize] & mask > 0 {
+                    0x1
+                } else {
+                    0x0
+                } | if self.vram[(addr + 1) as usize] & mask > 0 {
+                    0x2
+                } else {
+                    0x0
+                }
+        }
+    }
+
     fn render_line(&self) {
         //@todo implement the rendering of a line
     }