use maps for compression and decompression functionality

Author: K0lb3

UnityPy/files/BundleFile.py

@@ -1,7 +1,7 @@
 # TODO: implement encryption for saving files
 import re
 from collections import namedtuple
-from typing import Optional, Tuple, Union
+from typing import Optional, Tuple, Union, cast
 
 from .. import config
 from ..enums import ArchiveFlags, ArchiveFlagsOld, CompressionFlags
@@ -351,12 +351,12 @@ def save_fs(self, writer: EndianBinaryWriter, data_flag: int, block_info_flag: i
         uncompressed_block_data_size = len(block_data)
 
         switch = data_flag & 0x3F
-        if switch == 1:  # LZMA
-            block_data = CompressionHelper.compress_lzma(block_data)
-        elif switch in [2, 3]:  # LZ4, LZ4HC
-            block_data = CompressionHelper.compress_lz4(block_data)
-        elif switch == 4:  # LZHAM
-            raise NotImplementedError
+        if switch in CompressionHelper.COMPRESSION_MAP:
+            block_data = CompressionHelper.COMPRESSION_MAP[switch](block_data)
+        else:
+            raise NotImplementedError(
+                f"No compression function in the CompressionHelper.COMPRESSION_MAP for {switch}"
+            )
 
         compressed_block_data_size = len(block_data)
 
@@ -525,16 +525,20 @@ def decompress_data(
             The decompressed data."""
         comp_flag = CompressionFlags(flags & ArchiveFlags.CompressionTypeMask)
 
-        if comp_flag == CompressionFlags.LZMA:  # LZMA
-            return CompressionHelper.decompress_lzma(compressed_data)
-        elif comp_flag in [CompressionFlags.LZ4, CompressionFlags.LZ4HC]:  # LZ4, LZ4HC
-            if self.decryptor is not None and flags & 0x100:
-                compressed_data = self.decryptor.decrypt_block(compressed_data, index)
-            return CompressionHelper.decompress_lz4(compressed_data, uncompressed_size)
-        elif comp_flag == CompressionFlags.LZHAM:  # LZHAM
-            raise NotImplementedError("LZHAM decompression not implemented")
+        if self.decryptor is not None and flags & 0x100:
+            compressed_data = self.decryptor.decrypt_block(compressed_data, index)
+
+        if comp_flag in CompressionHelper.DECOMPRESSION_MAP:
+            return cast(
+                bytes,
+                CompressionHelper.DECOMPRESSION_MAP[comp_flag](
+                    compressed_data, uncompressed_size
+                ),
+            )
         else:
-            return compressed_data
+            raise ValueError(
+                f"Unknown compression! flag: {flags}, compression flag: {comp_flag.value}"
+            )
 
     def get_version_tuple(self) -> Tuple[int, int, int]:
         """Returns the version as a tuple."""

UnityPy/helpers/CompressionHelper.py

@@ -1,21 +1,25 @@
 import gzip
 import lzma
 import struct
-from typing import Tuple
+from typing import Tuple, Union, Callable, Dict
 
 import brotli
 import lz4.block
 
+from ..enums.BundleFile import CompressionFlags
+
+
+ByteString = Union[bytes, bytearray, memoryview]
 GZIP_MAGIC: bytes = b"\x1f\x8b"
 BROTLI_MAGIC: bytes = b"brotli"
 
 
 # LZMA
-def decompress_lzma(data: bytes, read_decompressed_size: bool = False) -> bytes:
+def decompress_lzma(data: ByteString, read_decompressed_size: bool = False) -> bytes:
     """decompresses lzma-compressed data
 
     :param data: compressed data
-    :type data: bytes
+    :type data: ByteString
     :raises _lzma.LZMAError: Compressed data ended before the end-of-stream marker was reached
     :return: uncompressed data
     :rtype: bytes
@@ -41,13 +45,13 @@ def decompress_lzma(data: bytes, read_decompressed_size: bool = False) -> bytes:
     return dec.decompress(data[data_offset:])
 
 
-def compress_lzma(data: bytes, write_decompressed_size: bool = False) -> bytes:
+def compress_lzma(data: ByteString, write_decompressed_size: bool = False) -> 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
+    :type data: ByteString
     :return: compressed data
     :rtype: bytes
     """
@@ -77,11 +81,11 @@ def compress_lzma(data: bytes, write_decompressed_size: bool = False) -> bytes:
 
 
 # LZ4
-def decompress_lz4(data: bytes, uncompressed_size: int) -> bytes:  # LZ4M/LZ4HC
+def decompress_lz4(data: ByteString, uncompressed_size: int) -> bytes:  # LZ4M/LZ4HC
     """decompresses lz4-compressed data
 
     :param data: compressed data
-    :type data: bytes
+    :type data: ByteString
     :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.
@@ -91,11 +95,11 @@ def decompress_lz4(data: bytes, uncompressed_size: int) -> bytes:  # LZ4M/LZ4HC
     return lz4.block.decompress(data, uncompressed_size)
 
 
-def compress_lz4(data: bytes) -> bytes:  # LZ4M/LZ4HC
+def compress_lz4(data: ByteString) -> bytes:  # LZ4M/LZ4HC
     """compresses data via lz4.block
 
     :param data: uncompressed data
-    :type data: bytes
+    :type data: ByteString
     :return: compressed data
     :rtype: bytes
     """
@@ -105,77 +109,88 @@ def compress_lz4(data: bytes) -> bytes:  # LZ4M/LZ4HC
 
 
 # Brotli
-def decompress_brotli(data: bytes) -> bytes:
+def decompress_brotli(data: ByteString) -> bytes:
     """decompresses brotli-compressed data
 
     :param data: compressed data
-    :type data: bytes
+    :type data: ByteString
     :raises brotli.error: BrotliDecompress failed
     :return: uncompressed data
     :rtype: bytes
     """
     return brotli.decompress(data)
 
 
-def compress_brotli(data: bytes) -> bytes:
+def compress_brotli(data: ByteString) -> bytes:
     """compresses data via brotli
 
     :param data: uncompressed data
-    :type data: bytes
+    :type data: ByteString
     :return: compressed data
     :rtype: bytes
     """
     return brotli.compress(data)
 
 
 # GZIP
-def decompress_gzip(data: bytes) -> bytes:
+def decompress_gzip(data: ByteString) -> bytes:
     """decompresses gzip-compressed data
 
     :param data: compressed data
-    :type data: bytes
+    :type data: ByteString
     :raises OSError: Not a gzipped file
     :return: uncompressed data
     :rtype: bytes
     """
     return gzip.decompress(data)
 
 
-def compress_gzip(data: bytes) -> bytes:
+def compress_gzip(data: ByteString) -> 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
+    :type data: ByteString
     :return: compressed data
     :rtype: bytes
     """
     return gzip.compress(data)
 
 
-def chunk_based_compress(data: bytes, block_info_flag: int) -> Tuple[bytes, list]:
+def chunk_based_compress(
+    data: ByteString, block_info_flag: int
+) -> Tuple[ByteString, list]:
     """compresses AssetBundle data based on the block_info_flag
     LZ4/LZ4HC will be chunk-based compression
 
     :param data: uncompressed data
-    :type data: bytes
+    :type data: ByteString
     :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
+    chunk_size = None
+    compress_func = None
     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
+
+    if switch in COMPRESSION_MAP:
+        compress_func = COMPRESSION_MAP[switch]
+    else:
+        raise NotImplementedError(
+            f"No compression function in the CompressionHelper.COMPRESSION_MAP for {switch}"
+        )
+
+    if switch in COMPRESSION_CHUNK_SIZE_MAP:
+        chunk_size = COMPRESSION_CHUNK_SIZE_MAP[switch]
+    else:
+        raise NotImplementedError(
+            f"No chunk size in the CompressionHelper.COMPRESSION_CHUNK_SIZE_MAP for {switch}"
+        )
+
     block_info = []
     uncompressed_data_size = len(data)
     compressed_file_data = bytearray()
@@ -184,34 +199,92 @@ def chunk_based_compress(data: bytes, block_info_flag: int) -> Tuple[bytes, list
         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,
-            ))
+            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,
-            ))
+            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,
-            ))
+            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,
-            ))
+            block_info.append(
+                (
+                    uncompressed_data_size,
+                    len(compressed_data),
+                    block_info_flag,
+                )
+            )
     return bytes(compressed_file_data), block_info
+
+
+def decompress_lzham(data: ByteString, uncompressed_size: int) -> bytes:
+    raise NotImplementedError(
+        "Custom compression or unimplemented LZHAM (removed by Unity) encountered!"
+    )
+
+
+DECOMPRESSION_MAP: Dict[
+    Union[int, CompressionFlags], Callable[[ByteString, int], ByteString]
+] = {
+    CompressionFlags.NONE: lambda cd, _ucs: cd,
+    CompressionFlags.LZMA: lambda cd, _ucs: decompress_lzma(cd),
+    CompressionFlags.LZ4: lambda cd, ucs: decompress_lz4(cd, ucs),
+    CompressionFlags.LZ4HC: lambda cd, ucs: decompress_lz4(cd, ucs),
+    CompressionFlags.LZHAM: lambda cd, ucs: decompress_lzham(cd, ucs),
+}
+
+COMPRESSION_MAP: Dict[
+    Union[int, CompressionFlags], Callable[[ByteString], ByteString]
+] = {
+    CompressionFlags.NONE: lambda cd: cd,
+    CompressionFlags.LZMA: lambda cd: compress_lzma(cd),
+    CompressionFlags.LZ4: lambda cd: compress_lz4(cd),
+    CompressionFlags.LZ4HC: lambda cd: compress_lz4(cd),
+}
+
+COMPRESSION_CHUNK_SIZE_MAP: Dict[Union[int, CompressionFlags], int] = {
+    CompressionFlags.NONE: 0xFFFFFFFF,
+    CompressionFlags.LZMA: 0xFFFFFFFF,
+    CompressionFlags.LZ4: 0x00020000,
+    CompressionFlags.LZ4HC: 0x00020000,
+}
+
+
+__all__ = (
+    "compress_brotli",
+    "compress_gzip",
+    "compress_lz4",
+    "compress_lzma",
+    "decompress_brotli",
+    "decompress_gzip",
+    "decompress_lz4",
+    "decompress_lzma",
+    "decompress_lzham",
+    "chunk_based_compress",
+    "COMPRESSION_MAP",
+    "DECOMPRESSION_MAP",
+    "COMPRESSION_CHUNK_SIZE_MAP",
+)