cartridge.go

@@ -3,7 +3,8 @@ package main
 import (
 	"bytes"
 	"encoding/binary"
-	"fmt"
+	"io"
+	"log"
 	"os"
 )
 
@@ -214,7 +215,6 @@ var oldLicensees = map[byte]string{
 }
 
 type ROMHeader struct {
-	_          [256]byte
 	EntryPoint [4]byte
 	Logo       [48]byte
 	// NOTE(m): Assuming "old" cartridges here. This may cause problems with newer cartridges.
@@ -228,7 +228,7 @@ type ROMHeader struct {
 	DestinationCode      byte
 	OldLicenseeCode      byte
 	MaskROMVersionNumber byte
-	Checksum             byte
+	HeaderChecksum       byte
 	GlobalChecksum       [2]byte
 }
 
@@ -242,23 +242,32 @@ type Cartridge struct {
 	RAMSize     string
 	Destination string
 	Version     int
-	Checksum    byte
 }
 
-func Insert(filename string) (Cartridge, error) {
-	cartridge := Cartridge{Filename: filename}
-
-	rom, err := os.ReadFile(filename)
+func Insert(filename string) Cartridge {
+	file, err := os.Open(filename)
 	if err != nil {
-		return cartridge, err
+		log.Fatal(err)
+	}
+	defer file.Close()
+	cartridge := Cartridge{Filename: file.Name()}
+
+	// Jump to start of header
+	_, err = file.Seek(0x0100, io.SeekStart)
+	if err != nil {
+		log.Fatal(err)
 	}
 
 	// Read header
 	var header ROMHeader
-	buffer := bytes.NewReader(rom)
-	err = binary.Read(buffer, binary.LittleEndian, &header)
+	err = binary.Read(file, binary.LittleEndian, &header)
 	if err != nil {
-		return cartridge, nil
+		log.Fatal(err)
+	}
+
+	// Validate the ROM by checking presence of the Nintendo logo
+	if header.Logo != expectedLogo {
+		log.Fatal("Invalid ROM file: No valid logo found!")
 	}
 
 	// Convert some header values
@@ -283,16 +292,10 @@ func Insert(filename string) (Cartridge, error) {
 	}
 	cartridge.Version = int(header.MaskROMVersionNumber)
 
-	// Calculate and verify checksum
-	for address := uint16(0x0134); address <= uint16(0x014C); address++ {
-		cartridge.Checksum = cartridge.Checksum - rom[address] - 1
-	}
-	if cartridge.Checksum != header.Checksum {
-		return cartridge, fmt.Errorf("ROM checksum failed: %X does not equal %X", cartridge.Checksum, header.Checksum)
-	}
+	// TODO(m): Verify header checksum
 
 	// NOTE(m): Ignoring global checksum which is not used, except by one emulator.
 	// See https://gbdev.io/pandocs/The_Cartridge_Header.html#014e-014f--global-checksum
 
-	return cartridge, nil
+	return cartridge
 }

cartridge_test.go

@@ -6,26 +6,16 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestInsert(t *testing.T) {
-	cartridge, err := Insert("./roms/dmg-acid2.gb")
-
+func TestInsertCartridge(t *testing.T) {
+	cartridge := Insert("rom.gb")
 	assert := assert.New(t)
 
-	assert.Nil(err)
-	assert.Equal(cartridge.Filename, "./roms/dmg-acid2.gb")
-	assert.Equal(cartridge.Title, "DMG-ACID2")
-	assert.Equal(cartridge.Mapper, "ROM ONLY")
-	assert.Equal(cartridge.Licensee, "None")
+	assert.Equal(cartridge.Title, "SEIKEN DENSETSU")
+	assert.Equal(cartridge.Mapper, "MBC2+BATTERY")
+	assert.Equal(cartridge.Licensee, "Square")
 	assert.False(cartridge.SGBSupport, "SGB support should be false")
-	assert.Equal(cartridge.ROMSize, 32)
+	assert.Equal(cartridge.ROMSize, 256)
 	assert.Equal(cartridge.RAMSize, "0 - No RAM")
-	assert.Equal(cartridge.Destination, "Japan (and possibly overseas)")
+	assert.Equal(cartridge.Destination, "Overseas only")
 	assert.Equal(cartridge.Version, 0)
-	assert.Equal(cartridge.Checksum, byte(0x9F))
-}
-
-func TestFailedChecksum(t *testing.T) {
-	_, err := Insert("./roms/failed-checksum.gb")
-
-	assert.EqualError(t, err, "ROM checksum failed: 9F does not equal 41")
 }

main.go

@@ -10,7 +10,7 @@ func main() {
 	// 	log.Fatalln("No rom file specified")
 	// }
 	// romPath := os.Args[1]
-	romPath := "./roms/dmg-acid2.gb"
+	romPath := "rom.gb"
 
 	ui.Run(romPath)
 }

ui/controller.go

@@ -51,15 +51,10 @@ func (c *Controller) Run() {
 	running := true
 	for running {
 		for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
-			switch e := event.(type) {
+			switch event.(type) {
 			case *sdl.QuitEvent:
+				println("Quit")
 				running = false
-			case *sdl.KeyboardEvent:
-				if e.Type == sdl.KEYDOWN {
-					if e.Keysym.Sym == sdl.K_ESCAPE {
-						running = false
-					}
-				}
 			}
 		}