import brotli import gzip import lzma import lz4.block import struct from typing import Tuple GZIP_MAGIC: bytes = b"\x1f\x8b" BROTLI_MAGIC: bytes = b"brotli" # LZMA def decompress_lzma(data: bytes, read_decompressed_size: bool = False) -> bytes: """decompresses lzma-compressed data :param data: compressed data :type data: bytes :raises _lzma.LZMAError: Compressed data ended before the end-of-stream marker was reached :return: uncompressed data :rtype: bytes """ props, dict_size = struct.unpack(" bytes: """compresses data via lzma (unity specific) The current static settings may not be the best solution, but they are the most commonly used values and should therefore be enough for the time being. :param data: uncompressed data :type data: bytes :return: compressed data :rtype: bytes """ dict_size = 0x800000 # 1 << 23 compressor = lzma.LZMACompressor( format=lzma.FORMAT_RAW, filters=[ { "id": lzma.FILTER_LZMA1, "dict_size": dict_size, "lc": 3, "lp": 0, "pb": 2, "mode": lzma.MODE_NORMAL, "mf": lzma.MF_BT4, "nice_len": 123, } ], ) compressed_data = compressor.compress(data) + compressor.flush() cdl = len(compressed_data) if write_decompressed_size: return struct.pack(f" bytes: # LZ4M/LZ4HC """decompresses lz4-compressed data :param data: compressed data :type data: bytes :param uncompressed_size: size of the uncompressed data :type uncompressed_size: int :raises _block.LZ4BlockError: Decompression failed: corrupt input or insufficient space in destination buffer. :return: uncompressed data :rtype: bytes """ return lz4.block.decompress(data, uncompressed_size) def compress_lz4(data: bytes) -> bytes: # LZ4M/LZ4HC """compresses data via lz4.block :param data: uncompressed data :type data: bytes :return: compressed data :rtype: bytes """ return lz4.block.compress( data, mode="high_compression", compression=9, store_size=False ) # Brotli def decompress_brotli(data: bytes) -> bytes: """decompresses brotli-compressed data :param data: compressed data :type data: bytes :raises brotli.error: BrotliDecompress failed :return: uncompressed data :rtype: bytes """ return brotli.decompress(data) def compress_brotli(data: bytes) -> bytes: """compresses data via brotli :param data: uncompressed data :type data: bytes :return: compressed data :rtype: bytes """ return brotli.compress(data) # GZIP def decompress_gzip(data: bytes) -> bytes: """decompresses gzip-compressed data :param data: compressed data :type data: bytes :raises OSError: Not a gzipped file :return: uncompressed data :rtype: bytes """ return gzip.decompress(data) def compress_gzip(data: bytes) -> bytes: """compresses data via gzip The current static settings may not be the best solution, but they are the most commonly used values and should therefore be enough for the time being. :param data: uncompressed data :type data: bytes :return: compressed data :rtype: bytes """ return gzip.compress(data) def chunk_based_compress(data: bytes, block_info_flag: int) -> Tuple[bytes, list]: """compresses AssetBundle data based on the block_info_flag LZ4/LZ4HC will be chunk-based compression :param data: uncompressed data :type data: bytes :param block_info_flag: block info flag :type block_info_flag: int :return: compressed data and block info :rtype: tuple """ switch = block_info_flag & 0x3F if switch == 0: # NONE return data, [(len(data), len(data), block_info_flag)] elif switch == 1: # LZMA chunk_size = 0xFFFFFFFF compress_func = compress_lzma elif switch in [2, 3]: # LZ4 chunk_size = 0x00020000 compress_func = compress_lz4 elif switch == 4: # LZHAM raise NotImplementedError block_info = [] uncompressed_data_size = len(data) compressed_file_data = bytearray() p = 0 while uncompressed_data_size > chunk_size: compressed_data = compress_func(data[p : p + chunk_size]) if len(compressed_data) > chunk_size: compressed_file_data.extend(data[p : p + chunk_size]) block_info.append( ( chunk_size, chunk_size, block_info_flag ^ switch, ) ) else: compressed_file_data.extend(compressed_data) block_info.append( ( chunk_size, len(compressed_data), block_info_flag, ) ) p += chunk_size uncompressed_data_size -= chunk_size if uncompressed_data_size > 0: compressed_data = compress_func(data[p:]) if len(compressed_data) > uncompressed_data_size: compressed_file_data.extend(data[p:]) block_info.append( ( uncompressed_data_size, uncompressed_data_size, block_info_flag ^ switch, ) ) else: compressed_file_data.extend(compressed_data) block_info.append( ( uncompressed_data_size, len(compressed_data), block_info_flag, ) ) return bytes(compressed_file_data), block_info