first few functions and unit tests

.drone.yml

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+kind: pipeline
+type: docker
+name: default
+
+steps:
+- name : test
+  image: golang:latest
+  commands:
+  - go test
+- name : build
+  image: golang:latest
+  commands
+  - go build

pkg/chip8/chip8.go

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+package chip8
+
+import "fmt"
+
+const graphicsBufferSize = 64 * 32
+
+type Chip8 struct {
+	address_register uint16
+	beep_timer       uint16
+	draw_required    bool
+	delay_timer      uint16
+	graphics         [graphicsBufferSize]uint8
+	keys             [16]uint8
+	memory           [4096]uint8
+	opcode           uint16
+	pc               uint16
+	registers        [16]uint8 // 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{
+		0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
+		0x20, 0x60, 0x20, 0x20, 0x70, // 1
+		0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
+		0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
+		0x90, 0x90, 0xF0, 0x10, 0x10, // 4
+		0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
+		0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
+		0xF0, 0x10, 0x20, 0x40, 0x40, // 7
+		0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
+		0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
+		0xF0, 0x90, 0xF0, 0x90, 0x90, // A
+		0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
+		0xF0, 0x80, 0x80, 0x80, 0xF0, // C
+		0xE0, 0x90, 0x90, 0x90, 0xE0, // D
+		0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
+		0xF0, 0x80, 0xF0, 0x80, 0x80} // F
+}
+
+func NewCHIP8(prog []uint8) *Chip8 {
+	cpu := Chip8{pc: 0x200}
+	memory_slice := cpu.memory[:80]
+	copy(memory_slice, getLetters())
+	memory_slice = cpu.memory[200:]
+	copy(memory_slice, prog)
+
+	// Do some extra checking to ensure the right
+	// Stuff is copied
+
+	return &cpu
+}
+
+func (cpu *Chip8) GetGraphicsBuffer() [graphicsBufferSize]uint8 {
+	return cpu.graphics
+}
+
+func (cpu *Chip8) clearDisplay() {
+	// fuck it the gc can do the hard work for us
+	cpu.graphics = [64 * 32]uint8{}
+	cpu.draw_required = true
+}
+
+// what if there's nothing in the stack?
+// return something sensible
+func (cpu *Chip8) leaveFunction() {
+	cpu.pc = cpu.stack[len(cpu.stack)-1]
+	cpu.stack[len(cpu.stack)-1] = 0
+	cpu.stack = cpu.stack[:len(cpu.stack)-1]
+}
+
+func (cpu *Chip8) goTo() {
+	cpu.pc = cpu.opcode & 0x0FFF
+}
+
+func (cpu *Chip8) callSubroutine() {
+	cpu.stack = append(cpu.stack, cpu.pc)
+	cpu.pc = cpu.opcode & 0x0FFF
+}
+
+func (cpu *Chip8) skipIfRegisterEqual() {
+	r := (cpu.opcode) >> 8 & 0x0F
+	if cpu.registers[r] == uint8(cpu.opcode&0xFF) {
+		cpu.pc += 2
+	}
+}
+
+func (cpu *Chip8) skipIfRegisterNotEqual() {
+	r := (cpu.opcode) >> 8 & 0x0F
+	if cpu.registers[r] != uint8(cpu.opcode&0xFF) {
+		cpu.pc += 2
+	}
+}
+
+func (cpu *Chip8) skipIfRegistersEqual() {
+	x, y := (cpu.opcode>>8)&0x0F, (cpu.opcode>>4)&0x0F
+	if cpu.registers[x] == cpu.registers[y] {
+		cpu.pc += 2
+	}
+}
+
+func (cpu *Chip8) setRegisterToNN() {
+	r := (cpu.opcode >> 8) & 0x0F
+	cpu.registers[r] = uint8(cpu.opcode & 0xFF)
+}
+
+func (cpu *Chip8) RegisterPlusEqualsNN() {} // QUESTION HERE - WHAT DO IF IT WOULD WRAP ROUND?
+
+func main() {
+	fmt.Printf("Hello world!\n")
+	prog := []uint8{1, 2, 3, 4}
+	new_cpu := NewCHIP8(prog)
+	fmt.Printf("%d\n", new_cpu.opcode)
+}

pkg/chip8/chip8_test.go

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+package chip8
+
+import (
+	"testing"
+)
+
+func slicesEqual(x, y []uint8) bool {
+	if len(x) != len(y) {
+		return false
+	}
+	for i, xi := range x {
+		if xi != y[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// 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}
+	new_cpu := NewCHIP8(prog)
+	if !slicesEqual(new_cpu.memory[200:204], prog) {
+		t.Errorf("CPU not initalized properly")
+	}
+}
+
+func TestClearDisplay(t *testing.T) {
+	cpu := Chip8{}
+	for i := range cpu.graphics {
+		cpu.graphics[i] = uint8(i % 255)
+	}
+	cpu.clearDisplay()
+	graphics_array := cpu.GetGraphicsBuffer()
+	graphics_slice := graphics_array[:]
+	empty_slice := make([]uint8, len(cpu.graphics))
+	if !slicesEqual(graphics_slice, empty_slice) {
+		t.Errorf("Graphics buffer not cleared properly")
+	}
+}
+
+func TestLeaveFunction(t *testing.T) {
+	cpu := Chip8{pc: 50}
+	cpu.stack = append(cpu.stack, 1, 2, 3, 4, 5)
+	cpu.leaveFunction()
+	if cpu.pc != 4 && len(cpu.stack) != 4 {
+		t.Errorf("TestLeaveFunction not in expected state")
+	}
+}
+
+func TestPasses(t *testing.T) {
+	if 1 != 1 {
+		t.Errorf("We should never get this!")
+	}
+}