From ba28865248c017358bc0ab9c624823eaefebbc89 Mon Sep 17 00:00:00 2001
From: Pau Costa <pau.costa@gibobs.com>
Date: Tue, 23 Jul 2024 20:39:56 +0200
Subject: [PATCH] feat: rom loading, and character map

---
 emulator/chip8.go      |  77 +++++++++++++++++++++++++++++++++++++++++
 emulator/chip8_test.go |  21 +++++++++++
 main.go                |  40 +++++++++++++++++----
 roms/ibm_logo.ch8      | Bin 0 -> 132 bytes
 4 files changed, 132 insertions(+), 6 deletions(-)
 create mode 100644 emulator/chip8.go
 create mode 100644 emulator/chip8_test.go
 create mode 100644 roms/ibm_logo.ch8

diff --git a/emulator/chip8.go b/emulator/chip8.go
new file mode 100644
index 0000000..0dad9c6
--- /dev/null
+++ b/emulator/chip8.go
@@ -0,0 +1,77 @@
+package emulator
+
+import "errors"
+
+type CHIP8 struct {
+	memory     [4096]byte
+	v          [16]byte
+	i          uint16
+	pc         uint16
+	sp         uint16
+	delayTimer uint8
+	soundTimer uint8
+	stack      [16]uint16
+	keypad     [16]bool
+	// To transform the linear Memory to a 2D array for easier drawing,
+	// having a (x,  y) coordinate then (x, y) = graphics[x + (y * 64)]
+	graphics [64 * 32]bool
+	opcode   uint16
+	fonts    [80]byte
+}
+
+func NewChip8() *CHIP8 {
+	chip8 := &CHIP8{
+		memory: [4096]byte{},
+		v:      [16]byte{},
+		i:      0,
+		// The original 0x200 code of the CHIP-8 interpreter was from 0x0 to 0x200,
+		pc:         0x200,
+		sp:         0,
+		delayTimer: 0,
+		soundTimer: 0,
+		stack:      [16]uint16{},
+		keypad:     [16]bool{},
+		graphics:   [64 * 32]bool{},
+		opcode:     0,
+		fonts:      [80]byte{},
+	}
+	chip8.Initialize()
+	return chip8
+}
+
+func (c *CHIP8) Initialize() {
+	charMap := [80]byte{
+		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
+	}
+
+	// Char map goes from 0x050 to 0x9F
+	for i, charByte := range charMap {
+		c.memory[i+0x50] = charByte
+	}
+}
+
+func (c *CHIP8) LoadROMIntoMemory(dat []byte) error {
+	if len(dat) > len(c.memory)-0x200 {
+		return errors.New("ROM is too large to fit into memory")
+	}
+	// Roms start from 0x200
+	for i, datByte := range dat {
+		c.memory[i+0x200] = datByte
+	}
+	return nil
+}
diff --git a/emulator/chip8_test.go b/emulator/chip8_test.go
new file mode 100644
index 0000000..6abb295
--- /dev/null
+++ b/emulator/chip8_test.go
@@ -0,0 +1,21 @@
+package emulator
+
+import (
+	"testing"
+)
+
+func TestLoadRomIntoMemory(t *testing.T) {
+	chip8 := NewChip8()
+	romBytes := []byte{0xDE, 0xAD, 0xBE, 0xEF}
+
+	_ = chip8.LoadROMIntoMemory(romBytes)
+	// We always expect roms to be loaded starting from 0x200
+	ans := chip8.memory[0x200:0x204]
+
+	for i, ansByte := range ans {
+		if romBytes[i] != ansByte {
+			t.Errorf("Expected %x, got %x", romBytes[i], ansByte)
+		}
+	}
+
+}
diff --git a/main.go b/main.go
index 15d70bf..f9a1d15 100644
--- a/main.go
+++ b/main.go
@@ -4,11 +4,17 @@ import (
 	"fmt"
 	"github.com/hajimehoshi/ebiten/v2"
 	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
+	"github.com/micosilent/go_chip8/emulator"
 	"log"
+	"os"
+	"time"
 )
 
 type Game struct {
-	counter int
+	counter       int
+	lastFrameTime time.Time
+	debugText     string
+	emulator      *emulator.CHIP8
 }
 
 func (g *Game) Update() error {
@@ -17,24 +23,46 @@ func (g *Game) Update() error {
 
 func newGame() *Game {
 	return &Game{
-		counter: 1,
+		counter:       1,
+		lastFrameTime: time.Now(),
+		debugText:     "",
+		emulator:      emulator.NewChip8(),
+	}
+}
+
+func check(err error) {
+	if err != nil {
+		log.Fatal(err)
 	}
 }
 
 func (g *Game) Draw(screen *ebiten.Image) {
-	ebitenutil.DebugPrint(screen, fmt.Sprintf("Counter: %d", g.counter))
+	deltaTime := time.Since(g.lastFrameTime)
+	fps := int(1 / deltaTime.Seconds())
+	g.debugText = fmt.Sprintf("Counter: %d, fps: %d", g.counter, fps)
+	ebitenutil.DebugPrint(screen, g.debugText)
 	g.counter++
+	g.lastFrameTime = time.Now()
 }
 
 func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
 	return 320, 240
 }
 
+func (g *Game) LoadROM(path string) {
+	dat, err := os.ReadFile(path)
+	check(err)
+
+	err = g.emulator.LoadROMIntoMemory(dat)
+	check(err)
+}
+
 func main() {
 	game := newGame()
+	game.LoadROM("roms/ibm_logo.ch8")
 	ebiten.SetWindowSize(480, 320)
 	ebiten.SetWindowTitle("Go CHIP8 Emulator")
-	if err := ebiten.RunGame(game); err != nil {
-		log.Fatal(err)
-	}
+
+	err := ebiten.RunGame(game)
+	check(err)
 }
diff --git a/roms/ibm_logo.ch8 b/roms/ibm_logo.ch8
new file mode 100644
index 0000000000000000000000000000000000000000..113338e67097e0a2ad227e5b79b3a5d1a586a660
GIT binary patch
literal 132
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z5Ly6P{~H({0AT|Vg6SU&e;Dk5a@Gu%3_lotFf*_-@H6aZ_|5Q{;W2|VOes`300ZwW
A9{>OV

literal 0
HcmV?d00001