spoof mmap result with a spooky mixin

refinery/lib/structures.py

@@ -65,7 +65,7 @@ def __exit__(self, *args):
  self.stream.seek(self.cursor, io.SEEK_SET)
 
 
-class MemoryFile(Generic[T], io.IOBase):
+class MemoryFile(Generic[T]):
  """
  A thin wrapper around (potentially mutable) byte sequences which gives it the
  features of a file-like object.

refinery/lib/vfs.py

@@ -54,10 +54,18 @@ def mmap(self, length: int = 0, offset: int = 0) -> MemoryFile:
  Emulate the result of an `mmap` call to the virtual file.
  """
  view = memoryview(self.data)
+ node = self.node
  if length:
  view = view[offset:offset + length]
- fd = MemoryFile(view, read_as_bytes=True, fileno=self.node)
- return fd
+
+ class _MappedView(bytearray, MemoryFile):
+ def __init__(self):
+ MemoryFile.__init__(self, self, True, node)
+
+ mapped = _MappedView()
+ mapped[:] = view
+
+ return mapped
 
  def open(self, mode: str) -> MemoryFile:
  """