pkg/chip8/chip8.go

@@ -9,19 +9,19 @@ type Chip8 struct {
 	beep_timer       uint16
 	draw_required    bool
 	delay_timer      uint16
-	graphics         [graphicsBufferSize]uint8
-	keys             [16]uint8
-	memory           [4096]uint8
+	graphics         [graphicsBufferSize]byte
+	keys             [16]byte
+	memory           [4096]byte
 	opcode           uint16
 	pc               uint16
-	registers        [16]uint8 // an array - has a fixed length
-	stack            []uint16  // a slice - basically a c++ vector
+	registers        [16]byte // an array - has a fixed length
+	stack            []uint16 // a slice - basically a c++ vector
 }
 
 // we can't have const arrays in go
 // This is a good a solution as any
-func getLetters() []uint8 {
-	return []uint8{
+func getLetters() []byte {
+	return []byte{
 		0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
 		0x20, 0x60, 0x20, 0x20, 0x70, // 1
 		0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
@@ -40,7 +40,7 @@ func getLetters() []uint8 {
 		0xF0, 0x80, 0xF0, 0x80, 0x80} // F
 }
 
-func NewCHIP8(prog []uint8) *Chip8 {
+func NewCHIP8(prog []byte) *Chip8 {
 	cpu := Chip8{pc: 0x200}
 	memory_slice := cpu.memory[:80]
 	copy(memory_slice, getLetters())
@@ -53,13 +53,13 @@ func NewCHIP8(prog []uint8) *Chip8 {
 	return &cpu
 }
 
-func (cpu *Chip8) GetGraphicsBuffer() [graphicsBufferSize]uint8 {
+func (cpu *Chip8) GetGraphicsBuffer() [graphicsBufferSize]byte {
 	return cpu.graphics
 }
 
 func (cpu *Chip8) clearDisplay() {
 	// fuck it the gc can do the hard work for us
-	cpu.graphics = [64 * 32]uint8{}
+	cpu.graphics = [64 * 32]byte{}
 	cpu.draw_required = true
 }
 
@@ -82,14 +82,14 @@ func (cpu *Chip8) callSubroutine() {
 
 func (cpu *Chip8) skipIfRegisterEqual() {
 	r := (cpu.opcode) >> 8 & 0x0F
-	if cpu.registers[r] == uint8(cpu.opcode&0xFF) {
+	if cpu.registers[r] == byte(cpu.opcode&0xFF) {
 		cpu.pc += 2
 	}
 }
 
 func (cpu *Chip8) skipIfRegisterNotEqual() {
 	r := (cpu.opcode) >> 8 & 0x0F
-	if cpu.registers[r] != uint8(cpu.opcode&0xFF) {
+	if cpu.registers[r] != byte(cpu.opcode&0xFF) {
 		cpu.pc += 2
 	}
 }
@@ -103,14 +103,62 @@ func (cpu *Chip8) skipIfRegistersEqual() {
 
 func (cpu *Chip8) setRegisterTo() {
 	r := (cpu.opcode >> 8) & 0x0F
-	cpu.registers[r] = uint8(cpu.opcode & 0xFF)
+	cpu.registers[r] = byte(cpu.opcode & 0xFF)
 }
 
 func (cpu *Chip8) RegisterPlusEqualsNN() {} // QUESTION HERE - WHAT DO IF IT WOULD WRAP ROUND?
 
+func (cpu *Chip8) BitOpsAndMath() {
+	instruction := cpu.opcode & 0x0F
+	regX, regY := cpu.opcode>>8&0x0F, cpu.opcode>>4&0x0F
+	switch instruction {
+	case 0:
+		// 8XY0
+		// Assign value of register Y to register X
+		cpu.registers[regX] = cpu.registers[regY]
+	case 1:
+		// 8XY1
+		// Set register X to x|Y
+		cpu.registers[regX] = cpu.registers[regX] | cpu.registers[regY]
+	case 2:
+		// 8XY2
+		// Set register x to X&Y
+		cpu.registers[regX] = cpu.registers[regX] & cpu.registers[regY]
+	case 3:
+		// 8XY3
+		// Set register x to X^Y
+		cpu.registers[regX] = cpu.registers[regX] ^ cpu.registers[regY]
+	case 4:
+		// 8XY4
+		// Set register x to X+=Y (Set VF to 1 when there's a carry and 0 if not)
+		res := cpu.registers[regX] + cpu.registers[regY]
+		if res > 0xFF {
+			cpu.registers[0x0F] = 1
+		} else {
+			cpu.registers[0x0F] = 0
+		}
+		cpu.registers[regX] = res & 0xFF
+	case 5:
+		// 8XY5
+		// Set register x to X-=Y (Set VF to 1 when there's a carry and 0 if not)
+		res := cpu.registers[regX] - cpu.registers[regY]
+		if res > 0xFF {
+			cpu.registers[0x0F] = 1
+		} else {
+			cpu.registers[0x0F] = 0
+		}
+		cpu.registers[regX] = res & 0xFF
+	case 6:
+		// BXY6
+		// Store lsb of reg X in reg F and then shift reg X >> 1
+		cpu.registers[0x0F] = cpu.registers[regX] & 0x01
+		cpu.registers[regX] >>= 1
+	}
+}
+
 func main() {
 	fmt.Printf("Hello world!\n")
-	prog := []uint8{1, 2, 3, 4}
+	prog := []byte{1, 2, 3, 4}
 	new_cpu := NewCHIP8(prog)
 	fmt.Printf("%d\n", new_cpu.opcode)
 }

pkg/chip8/chip8_test.go

@@ -5,7 +5,7 @@ import (
 	"testing"
 )
 
-func slicesEqual(x, y []uint8) bool {
+func slicesEqual(x, y []byte) bool {
 	if len(x) != len(y) {
 		return false
 	}
@@ -20,7 +20,7 @@ func slicesEqual(x, y []uint8) bool {
 // This test is kinda shit, there's so much stuff we ain't testing
 // Maybe fix
 func TestCreateCPU(t *testing.T) {
-	prog := []uint8{1, 2, 3, 4}
+	prog := []byte{1, 2, 3, 4}
 	new_cpu := NewCHIP8(prog)
 	if !slicesEqual(new_cpu.memory[200:204], prog) {
 		t.Errorf("CPU not initalized properly")
@@ -30,12 +30,12 @@ func TestCreateCPU(t *testing.T) {
 func TestClearDisplay(t *testing.T) {
 	cpu := Chip8{}
 	for i := range cpu.graphics {
-		cpu.graphics[i] = uint8(i % 255)
+		cpu.graphics[i] = byte(i % 255)
 	}
 	cpu.clearDisplay()
 	graphics_array := cpu.GetGraphicsBuffer()
 	graphics_slice := graphics_array[:]
-	empty_slice := make([]uint8, len(cpu.graphics))
+	empty_slice := make([]byte, len(cpu.graphics))
 	if !slicesEqual(graphics_slice, empty_slice) {
 		t.Errorf("Graphics buffer not cleared properly")
 	}
@@ -68,7 +68,7 @@ func TestCallSubroutine(t *testing.T) {
 
 func TestSkipIfRegisterEqual(t *testing.T) {
 	var tests = []struct {
-		register, regValue uint8
+		register, regValue byte
 		compValue, want    uint16
 	}{
 		{0, 2, 4, 0},
@@ -92,7 +92,7 @@ func TestSkipIfRegisterEqual(t *testing.T) {
 
 func TestSkipIfRegisterNotEqual(t *testing.T) {
 	var tests = []struct {
-		register, regValue uint8
+		register, regValue byte
 		compValue, want    uint16
 	}{
 		{0, 2, 4, 2},
@@ -116,7 +116,7 @@ func TestSkipIfRegisterNotEqual(t *testing.T) {
 
 func TestSkipIfRegistersEqual(t *testing.T) {
 	var tests = []struct {
-		reg1, reg2, val1, val2 uint8
+		reg1, reg2, val1, val2 byte
 	}{
 		{0, 2, 4, 2},
 		{0, 2, 2, 2},