Move lru_cache definitions to __init__ (#30)

Using the lru_cache decorators on class methods, the ones that have a reference to `self`,
will also cache self. So we move it to the __init__ of the class

(DIS-2913)

dissect/hypervisor/disk/qcow2.py

@@ -116,6 +116,8 @@ def __init__(self, fh, data_file=None, backing_file=None):
             if backing_file != ALLOW_NO_BACKING_FILE:
                 self.backing_file = backing_file
 
+        self.l2_table = lru_cache(128)(self.l2_table)
+
         super().__init__(self.header.size)
 
     def _read_extensions(self):
@@ -167,7 +169,6 @@ def l1_table(self):
         self.fh.seek(self.header.l1_table_offset)
         return c_qcow2.uint64[self.header.l1_size](self.fh)
 
-    @lru_cache(maxsize=128)
     def l2_table(self, l2_offset):
         return L2Table(self, l2_offset)
 

dissect/hypervisor/disk/vhd.py

@@ -101,7 +101,8 @@ def __init__(self, fh, offset, max_entries):
         self.offset = offset
         self.max_entries = max_entries
 
-    @lru_cache(4096)
+        self.get = lru_cache(4096)(self.get)
+
     def get(self, block):
         # This could be improved by caching the entire BAT (or chunks if too large)
         if block + 1 > self.max_entries:

dissect/hypervisor/disk/vhdx.py

@@ -206,7 +206,8 @@ def __init__(self, vhdx, offset):
         else:
             self.entry_count = self._pb_count + ((self._pb_count - 1) // self.chunk_ratio)
 
-    @lru_cache(4096)
+        self.get = lru_cache(4096)(self.get)
+
     def get(self, entry):
         """Get a BAT entry."""
         if entry + 1 > self.entry_count:

dissect/hypervisor/disk/vmdk.py

@@ -199,7 +199,8 @@ def __init__(self, fh, parent=None, offset=0, sector_offset=0):
         self.size = self.header.capacity * SECTOR_SIZE
         self.sector_count = self.header.capacity
 
-    @lru_cache(128)
+        self._lookup_grain_table = lru_cache(128)(self._lookup_grain_table)
+
     def _lookup_grain_table(self, directory):
         gtbl_offset = self._grain_directory[directory]