Unofficial Portal 2 patch for mac. It fixes the issue that crashes the game when turrets are firing.

portal2patchmac.go

package main

import (
	"bytes"
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"io"
	"os"
	"os/user"
	"path"
)

func main() {
	fmt.Println("\n\nPORTAL2 studiorender.dylib unofficial Mac PATCH")
	fmt.Println("by gabstv")
	fmt.Println("---------")
	usr, _ := user.Current()
	dylp := path.Join(usr.HomeDir, "/Library/Application Support/Steam/SteamApps/common/Portal 2/bin/studiorender.dylib")
	if _, err := os.Stat(dylp); err != nil {
		fmt.Println("Could not apply patch!", err.Error())
		return
	}
	md, _ := MD5(dylp)
	applied := []byte{224, 0, 65, 149, 230, 133, 81, 175, 33, 138, 18, 229, 20, 46, 236, 163}
	pattern := []byte{108, 51, 233, 81, 137, 246, 133, 129, 222, 59, 79, 75, 64, 7, 146, 125}
	if bytes.Compare(applied, md) == 0 {
		fmt.Println("Patch is already applied!")
		return
	}
	if bytes.Compare(pattern, md) != 0 {
		fmt.Printf("Could not apply patch! MD5 checksum mismatch: (studiorender.dylib: %s) != %s\n", hex.EncodeToString(md), hex.EncodeToString(pattern))
		return
	}
	dir, fil := path.Split(dylp)
	// write a backup
	ext := path.Ext(fil)
	backupn := fil[:(len(fil)-len(ext))] + "_backup" + ext
	backupf, err := os.OpenFile(path.Join(dir, backupn), os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0666)
	if err != nil {
		fmt.Println("Could not apply patch!", err.Error())
		return
	}
	defer backupf.Close()
	original, err := os.OpenFile(dylp, os.O_RDWR, 0666)
	if err != nil {
		fmt.Println("Could not apply patch!", err.Error())
		return
	}
	defer original.Close()
	io.Copy(backupf, original)
	fmt.Println("studiorender.dylib backup file written")
	_, err = original.Seek(0x64f0, 0)
	if err != nil {
		fmt.Println("Could not apply patch!", err.Error())
		return
	}
	original.Write([]byte{0xC3})
	fmt.Println("PORTAL2 PATCH APPLIED!\n\n")
}

func MD5(path string) ([]byte, error) {
	h := md5.New()
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	_, err = io.Copy(h, f)
	if err != nil {
		return nil, err
	}
	return h.Sum(nil), nil
}