Golang MapleStory Exepatch/MapleStory(t).exe version identifier

main.go

package main

import (
	"encoding/hex"
	"flag"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
)

func main() {
	var input string
	flag.StringVar(&input, "input", "", "Input file")
	flag.Parse()

	fmt.Println("MapleStory ExePatch.dat Identifier and Mover v1.3.3.7-patch2-alpha")

	file, err := os.Open(input)
	if err != nil {
		panic(err)
	}

	// Read from back to front, 2048 bytes at a time

	size := 2048
	buffer := make([]byte, size)
	magicValue1 := [8]byte{0xBD, 0x04, 0xEF, 0xFE, 0x00, 0x00, 0x01, 0x00}
	/*
		  magicValue2 := [...]byte{
			0x56, 0x00, 0x53, 0x00, 0x5F, 0x00, 0x56, 0x00, 0x45, 0x00, 0x52, 0x00, 0x53, 0x00, 0x49, 0x00,
			0x4F, 0x00, 0x4E, 0x00, 0x5F, 0x00, 0x49, 0x00, 0x4E, 0x00, 0x46, 0x00, 0x4F, 0x00} // VS_VERSION_INFO
	*/
	offset := 0

	for {
		offset += len(buffer)
		_, err := file.Seek(int64(offset), os.SEEK_SET)
		if err != nil {
			fmt.Println("File seek error", err)
			break
		}

		amount, err := file.Read(buffer)
		if err != nil {
			fmt.Println("File read error", err)
			break
		}

		matching := true
		idx := 0
		for ; idx < amount; idx++ {
			matching = true
			for idx2, b2 := range magicValue1 {
				bufferOffset := idx + idx2
				if bufferOffset >= amount {
					// No more data to compare
					matching = false
					break
				}

				b := buffer[bufferOffset]

				if b2 != b {
					// We don't have a match
					matching = false
				}
			}

			if matching {
				break
			}
		}

		if !matching {
			continue
		}

		// Cool. Now check the version info
		file.Seek(int64(offset+idx+8), os.SEEK_SET)
		buffer = make([]byte, 8)
		file.Read(buffer)

		version := uint16(buffer[0] | buffer[1]<<8)
		//locale := uint16(buffer[2] | buffer[3] << 8)
		subversion := uint16(buffer[6] | buffer[7]<<8)
		fmt.Println(hex.Dump(buffer))

		fmt.Println("Found version:", version, "subversion", subversion)

		fileInfo, err := file.Stat()
		if err != nil {
			panic(err)
		}

		outputFilename := filepath.Join(filepath.Dir(input), fmt.Sprintf("MapleStory-v%d.%d.exe", version, subversion))
		fmt.Println("Writing to", outputFilename)

		// Time to copy

		b, err := ioutil.ReadFile(input)
		if err != nil {
			panic(err)
		}

		// write whole the body
		err = ioutil.WriteFile(outputFilename, b, 0644)
		if err != nil {
			panic(err)
		}

		modTime := fileInfo.ModTime()
		timeString := fmt.Sprintf("%04d%02d%02d%02d%02d.%02d", modTime.Year(), modTime.Month(), modTime.Day(), modTime.Hour(), modTime.Minute(), modTime.Second())

		// Copy modification time
		cmd := exec.Command("touch", "-t", timeString, outputFilename)
		cmd.Run()
		break
	}
	file.Close()
}