find_form_version.py

# coding=utf-8

import io
import os
import regex
import sys

DEBUG = False


def read_int32(data):
	return int.from_bytes(data.read(4), byteorder=sys.byteorder, signed=True)


def read_short(data):
	return int.from_bytes(data.read(2), byteorder=sys.byteorder, signed=True)


def read_signature(data):
	return data.read(4).decode('utf-8')


def main():
	file = r'E:\SteamLibrary\Skyrim Special Edition\Data\HearthFires.esm'
	# file = r'E:\SteamLibrary\Skyrim Special Edition\Data\test.esp'

	re = regex.compile('^[A-Z_]{4}')
	blocks = []

	with open(file, mode='rb') as f:
		file_extension = os.path.splitext(os.path.basename(file))[1]
		if file_extension not in ['.esp', '.esm']:
			raise ValueError('File extension did not match expected value: .esp, or .esm', file_extension)

		signature = read_signature(f)
		if signature != 'TES4':
			raise ValueError('File magic did not match expected value: TES4', signature)
		else:
			# skip file header
			if file_extension == '.esp':
				f.seek(read_int32(f) + 2, 1)
			elif file_extension == '.esm':
				f.seek(read_int32(f) + 16, 1)

		# ESPs and ESMs have slightly different headers
		if file_extension == '.esp':
			signature = read_signature(f)
			if signature != 'DATA':
				raise ValueError('Signature did not match expected value: DATA', signature)
			else:
				# skip DATA to first GRUP
				data_size = read_short(f)
				f.seek(data_size, 1)

		signature = read_signature(f)
		if signature != 'GRUP':
			raise ValueError('Signature did not match expected value: GRUP', signature)
		else:
			f.seek(-4, 1)

			while True:
				if f.tell() >= os.path.getsize(file):
					break

				signature = read_signature(f)
				data_size = read_int32(f)
				f.seek(-8, 1)

				data_block = f.read(data_size)
				group = io.BytesIO(data_block)
				blocks.append(group)

				# print(f'{f.tell()}/{os.path.getsize(file)} = {signature}:{data_size}')

	# iterate through blocks
	for block in blocks:
		# GRUP
		block_signature = read_signature(block)

		# [GRUP] Data Size
		block_size = read_int32(block)

		# Signature of records in GRUP
		group_signature = read_signature(block)
		if group_signature in ['CELL', 'WRLD', 'DIAL']:
			# CELL, WRLD, and DIAL groups have groups within groups within groups - skipping for now
			# TODO: Validate block data to ensure no data loss from blocks[] generation
			# TODO: Iterate through groups, perhaps recursively?
			continue

		if re.match(group_signature) is None:
			raise ValueError('Group signature did not match expected pattern: ^[A-Z]{4}', group_signature)

		if DEBUG:
			print('[Block] {} ({}): {}'.format(block_signature, block_size, group_signature))

		# unknown and irrelevant data
		block.seek(12, 1)

		# iterate through records in group and output some record header data
		while True:
			if block.tell() >= block_size:
				break

			# [Field] Signature
			record_signature = read_signature(block)

			# [Field] Data Size
			data_size = read_int32(block)

			# [Field] Record Flags
			block.seek(4, 1)

			# [Field] Form ID
			form_id = '{:08x}'.format(read_int32(block))

			# [Field] Version Control Info 1
			block.seek(4, 1)

			# [Field] Form Version
			form_version = read_short(block)

			# [Field] Version Control Info 2
			block.seek(2, 1)

			# skip to next record
			block.seek(data_size, 1)

			print(f'[Record] [{record_signature}:{form_id.upper()}] Form Version: {form_version}')


if __name__ == '__main__':
	main()