pakExtractor.py

from io import BufferedReader, BufferedWriter
import json
import os
import struct
import sys
import pathlib
from typing import List
import zlib
from yaxToXml import yaxToXml

def read_uint32(file: BufferedWriter) -> int:
	entry = file.read(4)
	return struct.unpack('<I', entry)[0]

class HeaderEntry:
	type: int
	uncompressedSize: int
	offset: int

	pakSize: int

	def __init__(self, file: BufferedReader):
		self.type = read_uint32(file)
		self.uncompressedSize = read_uint32(file)
		self.offset = read_uint32(file)

class FilEntry:
	data: bytes

	isCompressed: bool

	def __init__(self, file: BufferedReader, entrySize: int, uncompressedSize: int, isCompressed: bool):
		self.isCompressed = isCompressed
		
		if isCompressed:
			compressedSize = read_uint32(file)
			paddingEndLength = entrySize - compressedSize - 4
		else:
			paddingEndLength = (4 - (uncompressedSize % 4)) % 4

		self.data = file.read(entrySize - paddingEndLength)

def extractPakFile(pakFile: str, convertYaxToXml: bool = False, updateInfoOnly: bool = False):
	with open(pakFile, "rb") as f:
		fileSize = os.fstat(f.fileno()).st_size
		f.seek(0x8)
		firstOffset = read_uint32(f)
		fileCount = (firstOffset - 0x4) // 12
		
		f.seek(0)
		# gather entries
		headerEntries: List[HeaderEntry] = []
		for i in range(fileCount):
			headerEntries.append(HeaderEntry(f))
		
		# calculate files sizes
		lastOffset = firstOffset
		for i in range(1, fileCount):
			headerEntries[i - 1].pakSize = headerEntries[i].offset - lastOffset
			lastOffset = headerEntries[i].offset
		headerEntries[fileCount - 1].pakSize = fileSize - lastOffset

		# read files
		files: List[FilEntry] = []
		for i in range(fileCount):
			f.seek(headerEntries[i].offset)
			isCompressed = headerEntries[i].uncompressedSize > headerEntries[i].pakSize
			files.append(FilEntry(f, headerEntries[i].pakSize, headerEntries[i].uncompressedSize, isCompressed))

		# write files
		extractionFolder = os.path.join(os.path.dirname(pakFile), "pakExtracted", os.path.basename(pakFile))
		pathlib.Path(extractionFolder).mkdir(parents=True, exist_ok=True)

		pakInfoJson = {
			"files": [
				{
					"name": f"{i}.yax",	# yax, cause Yet Another Xml encoding
					"type": headerEntries[i].type,
				}
				for i in range(fileCount)
			]
		}
		with open(os.path.join(extractionFolder, "pakInfo.json"), "w") as f:
			f.write(json.dumps(pakInfoJson, indent=4))
		
		if updateInfoOnly:
			print("Info updated")
			return
		
		for i in range(fileCount):
			data: bytes
			if files[i].isCompressed:
				data = zlib.decompress(files[i].data)
			else:
				data = files[i].data

			with open(os.path.join(extractionFolder, f"{i}.yax"), "wb") as f:
				f.write(data)

		print(f"Extracted {fileCount} files")

		if convertYaxToXml:
			for i in range(fileCount):
				yaxToXml(os.path.join(extractionFolder, f"{i}.yax"))

if __name__ == "__main__":
	pakFiles = [f for f in sys.argv[1:] if f.endswith(".pak")]
	updateInfoOnly = "-u" in sys.argv
	
	for pakFile in pakFiles:
		extractPakFile(pakFile, updateInfoOnly=updateInfoOnly)