Move lru_cache definitions to __init__ (#18)

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)

Author: Miauwkeru

dissect/cim/index.py

@@ -16,10 +16,11 @@ class Index:
     def __init__(self, cim, fh, mapping):
         self.store = Store(cim, fh, mapping)
 
+        self._lookup = lru_cache(1024)(self._lookup)
+
     def lookup(self, key):
         return self._lookup(str(key), self.store.root_page)
 
-    @lru_cache(1024)
     def _lookup(self, key, page):
         matches = []
 
@@ -94,6 +95,8 @@ def __init__(self, store, fh, logical_num, page_num):
 
         self.count = self.page.record_count
 
+        self.key = lru_cache(256)(self.key)
+
     def _string_part(self, idx):
         offset = self.page.string_table[idx]
         return self.data[offset : self.data.find(b"\x00", offset)].decode("utf8")
@@ -108,7 +111,6 @@ def string(self, idx):
 
         return "/".join(parts)
 
-    @lru_cache(256)
     def key(self, idx):
         str_idx = self.page.keys[idx]
         key_idx = self.string(str_idx)

dissect/cim/mappings.py

@@ -16,6 +16,8 @@ def __init__(self, cim, fh):
 
         self._reverse_map = {}
 
+        self.get_entry = lru_cache(256)(self.get_entry)
+
     def __getitem__(self, k):
         if not isinstance(k, int):
             raise ValueError("Invalid type")
@@ -31,7 +33,6 @@ def _generate_reverse_map(self):
 
             self._reverse_map[pnum] = i
 
-    @lru_cache(256)
     def get_entry(self, logical_num):
         if logical_num > self.mapping.mapping_entry_count:
             raise IndexError(logical_num)