Move the selection between the native and Python implementations of l…

…zo and lz4 to dissect.util (#27)

README.md

@@ -17,7 +17,17 @@ Information on the supported Python versions can be found in the Getting Started
 pip install dissect.squashfs
 ```
 
-This module is also automatically installed if you install the `dissect` package.
+This project decompresses lzo and lz4 compressed file systems and can use the faster, native (C-based) lz4 and lzo
+implementations when installed, instead of the slower pure Python implementation provided by `dissect.util`. To use
+these faster implementations, install the package with the lzo and lz4 extras:
+
+```bash
+pip install "dissect.squashfs[lz4,lzo]"
+```
+
+Unfortunately there is no binary `python-lzo` wheel for PyPy installations on Windows, so it won't be installed there
+
+This module including the lz4 and lzo extras is also automatically installed if you install the `dissect` package.
 
 ## Build and test instructions
 

dissect/squashfs/compression.py

@@ -11,9 +11,9 @@ def initialize(id: int, options: Optional[bytes]) -> Compression:
     modules = {
         c_squashfs.ZLIB_COMPRESSION: (NativeZlib,),
         c_squashfs.LZMA_COMPRESSION: (NativeLZMA,),
-        c_squashfs.LZO_COMPRESSION: (NativeLZO, PythonLZO),
+        c_squashfs.LZO_COMPRESSION: (AvailableLZO,),
         c_squashfs.XZ_COMPRESSION: (NativeXZ,),
-        c_squashfs.LZ4_COMPRESSION: (NativeLZ4, PythonLZ4),
+        c_squashfs.LZ4_COMPRESSION: (AvailableLZ4,),
         c_squashfs.ZSTD_COMPRESSION: (NativeZSTD,),
     }
 
@@ -60,14 +60,7 @@ def decompress(self, data: bytes, expected: int) -> bytes:
         return self._module.decompress(data)
 
 
-class NativeLZO(Compression):
-    module = "lzo"
-
-    def decompress(self, data: bytes, expected: int) -> bytes:
-        return self._module.decompress(data, False, expected)
-
-
-class PythonLZO(Compression):
+class AvailableLZO(Compression):
     module = "dissect.util.compression.lzo"
 
     def decompress(self, data: bytes, expected: int) -> bytes:
@@ -81,18 +74,11 @@ def decompress(self, data: bytes, expected: int) -> bytes:
         return self._module.decompress(data)
 
 
-class NativeLZ4(Compression):
-    module = "lz4.block"
-
-    def decompress(self, data: bytes, expected: int) -> bytes:
-        return self._module.decompress(data, expected)
-
-
-class PythonLZ4(Compression):
+class AvailableLZ4(Compression):
     module = "dissect.util.compression.lz4"
 
     def decompress(self, data: bytes, expected: int) -> bytes:
-        return self._module.decompress(data)
+        return self._module.decompress(data, uncompressed_size=expected)
 
 
 class NativeZSTD(Compression):

pyproject.toml

@@ -37,11 +37,15 @@ repository = "https://github.com/fox-it/dissect.squashfs"
 
 [project.optional-dependencies]
 full = [
-    "lz4",
+    "zstandard",
+]
+lzo = [
     # There are no Windows PyPy wheels available for python-lzo
     # So we use a pure python fallback for it.
     "python-lzo; platform_system != 'Windows' or platform_python_implementation != 'PyPy'",
-    "zstandard",
+]
+lz4 = [
+    "lz4",
 ]
 dev = [
     "dissect.squashfs[full]",