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Michael Smith 2025-08-04 13:56:54 +02:00
parent c312e77318
commit 06b23a5b7c
4 changed files with 384 additions and 0 deletions
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rom.gb

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package main
import (
"bytes"
"fmt"
"io"
"log"
"os"
)
func main() {
var count int
// See https://gbdev.io/pandocs/The_Cartridge_Header.html#0104-0133--nintendo-logo
expected_logo := []byte{
0xCE, 0xED, 0x66, 0x66, 0xCC, 0x0D, 0x00, 0x0B,
0x03, 0x73, 0x00, 0x83, 0x00, 0x0C, 0x00, 0x0D,
0x00, 0x08, 0x11, 0x1F, 0x88, 0x89, 0x00, 0x0E,
0xDC, 0xCC, 0x6E, 0xE6, 0xDD, 0xDD, 0xD9, 0x99,
0xBB, 0xBB, 0x67, 0x63, 0x6E, 0x0E, 0xEC, 0xCC,
0xDD, 0xDC, 0x99, 0x9F, 0xBB, 0xB9, 0x33, 0x3E,
}
// Cartridge types
// See https://gbdev.io/pandocs/The_Cartridge_Header.html#0147--cartridge-type
cartridge_types := map[byte]string{
0x00: "ROM ONLY",
0x01: "MBC1",
0x02: "MBC1+RAM",
0x03: "MBC1+RAM+BATTERY",
0x05: "MBC2",
0x06: "MBC2+BATTERY",
0x08: "ROM+RAM 9",
0x09: "ROM+RAM+BATTERY 9",
0x0B: "MMM01",
0x0C: "MMM01+RAM",
0x0D: "MMM01+RAM+BATTERY",
0x0F: "MBC3+TIMER+BATTERY",
0x10: "MBC3+TIMER+RAM+BATTERY 10",
0x11: "MBC3",
0x12: "MBC3+RAM 10",
0x13: "MBC3+RAM+BATTERY 10",
0x19: "MBC5",
0x1A: "MBC5+RAM",
0x1B: "MBC5+RAM+BATTERY",
0x1C: "MBC5+RUMBLE",
0x1D: "MBC5+RUMBLE+RAM",
0x1E: "MBC5+RUMBLE+RAM+BATTERY",
0x20: "MBC6",
0x22: "MBC7+SENSOR+RUMBLE+RAM+BATTERY",
0xFC: "POCKET CAMERA",
0xFD: "BANDAI TAMA5",
0xFE: "HuC3",
0xFF: "HuC1+RAM+BATTERY",
}
// RAM sizes
// https://gbdev.io/pandocs/The_Cartridge_Header.html#0149--ram-size
ram_sizes := map[byte]string{
0x00: "0 - No RAM ",
0x01: "UNUSED VALUE",
0x02: "8 KiB - 1 bank",
0x03: "32 KiB - 4 banks of 8 KiB each",
0x04: "128 KiB 16 banks of 8 KiB each",
0x05: "64 KiB 8 banks of 8 KiB each",
}
// Old licensees
// https://gbdev.io/pandocs/The_Cartridge_Header.html#014b--old-licensee-code
old_licensees := map[byte]string{
0x00: "None",
0x01: "Nintendo",
0x08: "Capcom",
0x09: "HOT-B",
0x0A: "Jaleco",
0x0B: "Coconuts Japan",
0x0C: "Elite Systems",
0x13: "EA (Electronic Arts)",
0x18: "Hudson Soft",
0x19: "ITC Entertainment",
0x1A: "Yanoman",
0x1D: "Japan Clary",
0x1F: "Virgin Games Ltd.3",
0x24: "PCM Complete",
0x25: "San-X",
0x28: "Kemco",
0x29: "SETA Corporation",
0x30: "Infogrames5",
0x31: "Nintendo",
0x32: "Bandai",
0x33: "Indicates that the New licensee code should be used instead.",
0x34: "Konami",
0x35: "HectorSoft",
0x38: "Capcom",
0x39: "Banpresto",
0x3C: "Entertainment Interactive (stub)",
0x3E: "Gremlin",
0x41: "Ubi Soft1",
0x42: "Atlus",
0x44: "Malibu Interactive",
0x46: "Angel",
0x47: "Spectrum HoloByte",
0x49: "Irem",
0x4A: "Virgin Games Ltd.3",
0x4D: "Malibu Interactive",
0x4F: "U.S. Gold",
0x50: "Absolute",
0x51: "Acclaim Entertainment",
0x52: "Activision",
0x53: "Sammy USA Corporation",
0x54: "GameTek",
0x55: "Park Place13",
0x56: "LJN",
0x57: "Matchbox",
0x59: "Milton Bradley Company",
0x5A: "Mindscape",
0x5B: "Romstar",
0x5C: "Naxat Soft14",
0x5D: "Tradewest",
0x60: "Titus Interactive",
0x61: "Virgin Games Ltd.3",
0x67: "Ocean Software",
0x69: "EA (Electronic Arts)",
0x6E: "Elite Systems",
0x6F: "Electro Brain",
0x70: "Infogrames5",
0x71: "Interplay Entertainment",
0x72: "Broderbund",
0x73: "Sculptured Software6",
0x75: "The Sales Curve Limited7",
0x78: "THQ",
0x79: "Accolade15",
0x7A: "Triffix Entertainment",
0x7C: "MicroProse",
0x7F: "Kemco",
0x80: "Misawa Entertainment",
0x83: "LOZC G.",
0x86: "Tokuma Shoten",
0x8B: "Bullet-Proof Software2",
0x8C: "Vic Tokai Corp.16",
0x8E: "Ape Inc.17",
0x8F: "I'Max18",
0x91: "Chunsoft Co.8",
0x92: "Video System",
0x93: "Tsubaraya Productions",
0x95: "Varie",
0x96: "Yonezawa19/S'Pal",
0x97: "Kemco",
0x99: "Arc",
0x9A: "Nihon Bussan",
0x9B: "Tecmo",
0x9C: "Imagineer",
0x9D: "Banpresto",
0x9F: "Nova",
0xA1: "Hori Electric",
0xA2: "Bandai",
0xA4: "Konami",
0xA6: "Kawada",
0xA7: "Takara",
0xA9: "Technos Japan",
0xAA: "Broderbund",
0xAC: "Toei Animation",
0xAD: "Toho",
0xAF: "Namco",
0xB0: "Acclaim Entertainment",
0xB1: "ASCII Corporation or Nexsoft",
0xB2: "Bandai",
0xB4: "Square Enix",
0xB6: "HAL Laboratory",
0xB7: "SNK",
0xB9: "Pony Canyon",
0xBA: "Culture Brain",
0xBB: "Sunsoft",
0xBD: "Sony Imagesoft",
0xBF: "Sammy Corporation",
0xC0: "Taito",
0xC2: "Kemco",
0xC3: "Square",
0xC4: "Tokuma Shoten",
0xC5: "Data East",
0xC6: "Tonkin House",
0xC8: "Koei",
0xC9: "UFL",
0xCA: "Ultra Games",
0xCB: "VAP, Inc.",
0xCC: "Use Corporation",
0xCD: "Meldac",
0xCE: "Pony Canyon",
0xCF: "Angel",
0xD0: "Taito",
0xD1: "SOFEL (Software Engineering Lab)",
0xD2: "Quest",
0xD3: "Sigma Enterprises",
0xD4: "ASK Kodansha Co.",
0xD6: "Naxat Soft14",
0xD7: "Copya System",
0xD9: "Banpresto",
0xDA: "Tomy",
0xDB: "LJN",
0xDD: "Nippon Computer Systems",
0xDE: "Human Ent.",
0xDF: "Altron",
0xE0: "Jaleco",
0xE1: "Towa Chiki",
0xE2: "Yutaka # Needs more info",
0xE3: "Varie",
0xE5: "Epoch",
0xE7: "Athena",
0xE8: "Asmik Ace Entertainment",
0xE9: "Natsume",
0xEA: "King Records",
0xEB: "Atlus",
0xEC: "Epic/Sony Records",
0xEE: "IGS",
0xF0: "A Wave",
0xF3: "Extreme Entertainment",
0xFF: "LJN",
}
file, err := os.Open("rom.gb")
if err != nil {
log.Fatal(err)
}
defer file.Close()
fmt.Printf("Loading ROM file \"%s\"\n", file.Name())
_, err = file.Seek(0X100, 0)
if err != nil {
log.Fatal(err)
}
entrypoint := make([]byte, 4)
count, err = file.Read(entrypoint)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Read entrypoint instructions: %X\n\n", entrypoint[:count])
fmt.Println("Reading header")
logo := make([]byte, 48)
count, err = file.Read(logo)
if err != nil {
log.Fatal(err)
}
if bytes.Equal(logo, expected_logo) {
fmt.Println("Valid logo found")
} else {
log.Fatal("Invalid ROM file: No valid logo found!")
}
// NOTE(m): Assuming "old" cartridges here. This may cause problems with newer cartridges.
// See https://gbdev.io/pandocs/The_Cartridge_Header.html#0134-0143--title
raw_title := make([]byte, 16)
count, err = file.Read(raw_title)
if err != nil {
log.Fatal(err)
}
// Strip padding bytes
title := bytes.ReplaceAll(raw_title, []byte{0x00}, nil)
fmt.Printf("Read title: %s\n", title)
new_licensee := make([]byte, 2)
count, err = file.Read(new_licensee)
if err != nil {
log.Fatal(err)
}
if bytes.Equal(new_licensee, []byte{0x00, 0x00}) {
fmt.Println("Read new licensee: N/A")
} else {
fmt.Printf("Read new licensee: %q\n", new_licensee[:count])
}
sgb_flag := make([]byte, 1)
count, err = file.Read(sgb_flag)
if err != nil {
log.Fatal(err)
}
if bytes.Equal(sgb_flag, []byte{0x03}) {
fmt.Println("Read SGB flag: SGB support")
} else {
fmt.Println("Read SGB flag: No SGB support")
}
cartridge_type := make([]byte, 1)
count, err = file.Read(cartridge_type)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Read cartridge type: %s\n", cartridge_types[cartridge_type[0]])
raw_rom_size := make([]byte, 1)
count, err = file.Read(raw_rom_size)
if err != nil {
log.Fatal(err)
}
rom_size := 32 * (1 << raw_rom_size[0])
fmt.Printf("Read ROM size: %d bytes\n", rom_size)
ram_size := make([]byte, 1)
count, err = file.Read(ram_size)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Read RAM size: %s\n", ram_sizes[ram_size[0]])
destination_code := make([]byte, 1)
count, err = file.Read(destination_code)
if err != nil {
log.Fatal(err)
}
if bytes.Equal(destination_code, []byte{0x00}) {
fmt.Println("Read destination code: Japan (and possibly overseas)")
} else if bytes.Equal(destination_code, []byte{0x01}) {
fmt.Println("Read destination code: Overseas only")
} else {
fmt.Println("Read destination code: Invalid value")
}
old_licensee := make([]byte, 1)
count, err = file.Read(old_licensee)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Read old licensee: %s\n", old_licensees[old_licensee[0]])
rom_version := make([]byte, 1)
count, err = file.Read(rom_version)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Read Mask ROM version number: %X\n", rom_version[:count])
header_checksum := make([]byte, 1)
count, err = file.Read(header_checksum)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Read header checksum: %X\n", header_checksum[:count])
// FIXME(m): Calculate and validate checksum!
global_checksum := make([]byte, 2)
count, err = file.Read(global_checksum)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Read global checksum: %X\n", global_checksum[:count])
// NOTE(m): Not used, except by one emulator.
// See https://gbdev.io/pandocs/The_Cartridge_Header.html#014e-014f--global-checksum
fmt.Printf("Finished reading header\n\n")
printCurrentPosition(file)
}
func printCurrentPosition(file *os.File) {
pos, err := file.Seek(0, io.SeekCurrent)
if err != nil {
panic(err)
}
fmt.Printf("Current position: 0x%X\n", pos)
}

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module example/gb-player
go 1.24.5

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