67 lines
1.9 KiB
Python
67 lines
1.9 KiB
Python
class Node(object):
|
|
|
|
def __init__(self, results):
|
|
self.results = results
|
|
self.next = next
|
|
|
|
|
|
class LinkedList(object):
|
|
|
|
def __init__(self):
|
|
self.head = None
|
|
self.tail = None
|
|
|
|
def move_to_front(self, node):
|
|
pass
|
|
|
|
def append_to_front(self, node):
|
|
pass
|
|
|
|
def remove_from_tail(self):
|
|
pass
|
|
|
|
|
|
class Cache(object):
|
|
|
|
def __init__(self, MAX_SIZE):
|
|
self.MAX_SIZE = MAX_SIZE
|
|
self.size = 0
|
|
self.lookup = {} # key: query, value: node
|
|
self.linked_list = LinkedList()
|
|
|
|
def get(self, query)
|
|
"""Get the stored query result from the cache.
|
|
|
|
Accessing a node updates its position to the front of the LRU list.
|
|
"""
|
|
node = self.lookup[query]
|
|
if node is None:
|
|
return None
|
|
self.linked_list.move_to_front(node)
|
|
return node.results
|
|
|
|
def set(self, results, query):
|
|
"""Set the result for the given query key in the cache.
|
|
|
|
When updating an entry, updates its position to the front of the LRU list.
|
|
If the entry is new and the cache is at capacity, removes the oldest entry
|
|
before the new entry is added.
|
|
"""
|
|
node = self.lookup[query]
|
|
if node is not None:
|
|
# Key exists in cache, update the value
|
|
node.results = results
|
|
self.linked_list.move_to_front(node)
|
|
else:
|
|
# Key does not exist in cache
|
|
if self.size == self.MAX_SIZE:
|
|
# Remove the oldest entry from the linked list and lookup
|
|
self.lookup.pop(self.linked_list.tail.query, None)
|
|
self.linked_list.remove_from_tail()
|
|
else:
|
|
self.size += 1
|
|
# Add the new key and value
|
|
new_node = Node(results)
|
|
self.linked_list.append_to_front(new_node)
|
|
self.lookup[query] = new_node
|