test snake game

Sources/CPU.swift

@@ -1,3 +1,6 @@
+import Foundation
+import SDL
+
 enum AddressingMode {
    case Immediate
    case ZeroPage
@@ -61,7 +64,6 @@ class CPU {
             return base &+ UInt16(register_y)
         case .Indirect_X:
             let base = memRead(programCounter)
-
             let ptr = UInt8(base) &+ register_x
             let lo = memRead(UInt16(ptr))
             let hi = memRead(UInt16(ptr &+ 1))
@@ -101,21 +103,24 @@ class CPU {
     }
 
     func run() {
-        run {
-
-        }
+        run {}
     }
 
-    func run(callback: () -> ()) {
+    func run(callback: @escaping () -> ()) {
         let opcodes = OPCODES_MAP
+        Timer.scheduledTimer(withTimeInterval: 0.00007, repeats: true) { [self] timer in
+            processOpcodes(callback: callback, opcodes: opcodes, timer: timer)
+        }
+    }
 
-        while true {
+    func processOpcodes(callback: () -> (), opcodes: [UInt8: OpCode], timer: Timer) {
         callback()
         let code = memRead(programCounter)
         programCounter += 1
 
         let programCounterState = programCounter
         guard let opcode = opcodes[code] else {fatalError("OpCode \(code) not recgonized!")}
+        // print(programCounter, opcode.mnemonic)
 
         switch code {
         /// LDA
@@ -249,7 +254,7 @@ class CPU {
         case 0xa0, 0xa4, 0xb4, 0xac, 0xbc:
             ldy(opcode.mode)
         case 0xea:
-                continue
+            return
         case 0xa8:
             register_y = register_x
             updateZeroAndNegativeFlags(register_y)
@@ -272,7 +277,10 @@ class CPU {
             inx()
         /// BRK
         case 0x00:
-                return
+            timer.invalidate()
+            SDL_DestroyWindow(window)
+            SDL_Quit()
+            exit(0)
         default: fatalError("TODO!")
         }
 
@@ -280,7 +288,6 @@ class CPU {
             programCounter += UInt16(opcode.len - 1)
         }
     }
-    }
 
     func updateZeroAndNegativeFlags(_ result: UInt8) {
         if result == 0 {
@@ -323,7 +330,7 @@ class CPU {
             status.remove(.carry)
         }
 
-        let result = UInt8(sum)
+        let result = UInt8(truncatingIfNeeded: sum)
 
         if (data ^ result) & (result ^ register_a) & 0x80 != 0 {
             status.insert(.overflow)
@@ -373,7 +380,6 @@ class CPU {
     func branch(_ condition: Bool) {
         if condition {
             let addr = memRead(programCounter)
-            // print(addr)
             let jump: Int8 = Int8(bitPattern: addr)
             let jump_addr = programCounter &+ 1 &+ UInt16(bitPattern: Int16(jump))
 

Sources/CPU_Instructions.swift

@@ -61,8 +61,8 @@ extension CPU {
     func sbc(_ mode: AddressingMode) {
         let addr = getOpperandAddress(mode)
         let data = memRead(addr)
-        let res = Int8(data) &* -1
-        addToRegisterA(UInt8(res &- 1))
+        let res = Int8(bitPattern: data) &* -1
+        addToRegisterA(UInt8(bitPattern: res &- 1))
     }
 
     func adc(_ mode: AddressingMode) {

Sources/main.swift

@@ -2,6 +2,7 @@
 // https://docs.swift.org/swift-book
 
 import SDL
+import Foundation
 
 guard SDL_Init(SDL_INIT_VIDEO) == 0 else {
     fatalError("SDL could not initialize! SDL_Error: \(String(cString: SDL_GetError()))")
@@ -17,6 +18,81 @@ let canvas = SDL_CreateRenderer(window, -1, SDL_RENDERER_PRESENTVSYNC.rawValue)
 
 SDL_RenderSetScale(canvas, 10.0, 10.0)
 
+var texture = SDL_CreateTexture(canvas, SDL_PIXELFORMAT_RGB24.rawValue, Int32(SDL_TEXTUREACCESS_TARGET.rawValue), 32, 32)
+
+var event = SDL_Event()
+var quit = false
+
+func handleUserInput(_ cpu: CPU, event: inout SDL_Event) {
+    while SDL_PollEvent(&event) > 0 {
+        if event.type == SDL_QUIT.rawValue {
+            SDL_DestroyWindow(window)
+            SDL_Quit()
+            exit(0)
+        }
+        if event.type == SDL_KEYDOWN.rawValue {
+            switch SDL_KeyCode(UInt32(event.key.keysym.sym)) {
+            case SDLK_ESCAPE:
+                SDL_DestroyWindow(window)
+                SDL_Quit()
+                exit(0)
+            case SDLK_w:
+                cpu.memWrite(0xff, data: 0x77)
+            case SDLK_a:
+                cpu.memWrite(0xff, data: 0x61)
+            case SDLK_s:
+                cpu.memWrite(0xff, data: 0x73)
+            case SDLK_d:
+                cpu.memWrite(0xff, data: 0x64)
+            default:
+                continue
+            }
+        }
+    }
+}
+
+func color(_ byte: UInt8) -> SDL_Color {
+    switch byte{
+    case 0:
+        return SDL_Color(r: 0, g: 0, b: 0, a: 255)
+    case 1:
+        return SDL_Color(r: 255, g: 255, b: 255, a: 255)
+    case 2, 9:
+        return SDL_Color(r: 128, g: 128, b: 128, a: 255)
+    case 3, 10:
+        return SDL_Color(r: 255, g: 0, b: 0, a: 255)
+    case 4, 11:
+        return SDL_Color(r: 0, g: 255, b: 0, a: 255)
+    case 5, 12:
+        return SDL_Color(r: 0, g: 0, b: 255, a: 255)
+    case 6, 13:
+        return SDL_Color(r: 255, g: 0, b: 255, a: 255)
+    case 7, 14:
+        return SDL_Color(r: 255, g: 255, b: 0, a: 255)
+    default:
+        return SDL_Color(r: 0, g: 255, b: 255, a: 255)
+
+    }
+}
+
+func readScreenState(_ cpu: CPU, frame: inout [UInt8]) -> Bool {
+
+    var frame_idx = 0
+    var update = false
+    for i in 0x0200..<0x600 {
+        let color_idx = cpu.memRead(UInt16(i))
+        let color = color(color_idx)
+        let (b1, b2, b3) = (color.r, color.b, color.g)
+        if frame[frame_idx] != b1 || frame[frame_idx + 1] != b2 || frame[frame_idx + 2] != b3 {
+           frame[frame_idx] = b1;
+           frame[frame_idx + 1] = b2;
+           frame[frame_idx + 2] = b3;
+           update = true;
+       }
+        frame_idx += 3
+    }
+    return update
+}
 
 let gameCode: [UInt8] = [
     0x20, 0x06, 0x06, 0x20, 0x38, 0x06, 0x20, 0x0d, 0x06, 0x20, 0x2a, 0x06, 0x60, 0xa9, 0x02, 0x85,
@@ -41,19 +117,23 @@ let gameCode: [UInt8] = [
     0xea, 0xca, 0xd0, 0xfb, 0x60
 ]
 
-print(gameCode[32])
-
-
 var cpu = CPU()
 cpu.load(gameCode)
 cpu.reset()
 
-cpu.run {
-    // TODO:
-    // read user input and write it to mem[0xFF]
-    // update mem[0xFE] with new Random Number
-    // read mem mapped screen state
-    // render screen state
+var screenState = [UInt8](repeating: 0, count: 32 * 3 * 32)
+var rng = SystemRandomNumberGenerator()
 
+cpu.run() {
+    handleUserInput(cpu, event: &event)
+    cpu.memWrite(0xfe, data: UInt8.random(in: 1...16, using: &rng))
 
+    if readScreenState(cpu, frame: &screenState) {
+        SDL_UpdateTexture(texture, nil, screenState, 32 * 3)
+        SDL_RenderCopy(canvas, texture, nil, nil)
+        SDL_RenderPresent(canvas)
     }
+}
+
+// Infinite loop otherwise the program will exit prematurely
+RunLoop.main.run()