Commit f566950d authored by hayato@chromium.org's avatar hayato@chromium.org

Provides a simple LRU cache class in Python.

https://bugs.webkit.org/show_bug.cgi?id=67823

Patch by Ai Makabi <makabi@google.com> on 2011-09-21
Reviewed by Tony Chang.

* Scripts/webkitpy/common/lru_cache.py:
* Scripts/webkitpy/common/lru_cache_unittest.py:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95928 268f45cc-cd09-0410-ab3c-d52691b4dbfc
parent 400be5f9
2011-09-21 Ai Makabi <makabi@google.com>
Provides a simple LRU cache class in Python.
https://bugs.webkit.org/show_bug.cgi?id=67823
Reviewed by Tony Chang.
* Scripts/webkitpy/common/lru_cache.py:
* Scripts/webkitpy/common/lru_cache_unittest.py:
2011-09-25 Adam Barth <abarth@webkit.org>
Remove PLATFORM(HAIKU) and associated code
#!/usr/bin/env python
# Copyright (C) 2011 Google Inc. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
class Node():
def __init__(self, key, value):
self.key = key
self.value = value
self.prev = None
self.next = None
class LRUCache():
"""An implementation of Least Recently Used (LRU) Cache."""
def __init__(self, capacity):
"""Initializes a lru cache with the given capacity.
Args:
capacity: The capacity of the cache.
"""
assert capacity > 0, "capacity (%s) must be greater than zero." % capacity
self._first = None
self._last = None
self._dict = {}
self._capacity = capacity
def __setitem__(self, key, value):
if key in self._dict:
self.__delitem__(key)
if not self._first:
self._one_node(key, value)
return
if len(self._dict) >= self._capacity:
del self._dict[self._last.key]
if self._capacity == 1:
self._one_node(key, value)
return
self._last = self._last.next
self._last.prev = None
node = Node(key, value)
node.prev = self._first
self._first.next = node
self._first = node
self._dict[key] = node
def _one_node(self, key, value):
node = Node(key, value)
self._dict[key] = node
self._first = node
self._last = node
def __getitem__(self, key):
if not self._first:
raise KeyError(str(key))
if self._first.key == key:
return self._first.value
if self._last.key == key:
next_last = self._last.next
next_last.prev = None
next_first = self._last
next_first.prev = self._first
next_first.next = None
self._first.next = next_first
self._first = next_first
self._last = next_last
return self._first.value
node = self._dict[key]
node.next.prev = node.prev
node.prev.next = node.next
node.prev = self._first
node.next = None
self._first.next = node
self._first = node
return self._first.value
def __delitem__(self, key):
node = self._dict[key]
del self._dict[key]
if self._first is self._last:
self._last = None
self._first = None
return
if self._first is node:
self._first = node.prev
self._first.next = None
return
if self._last is node:
self._last = node.next
self._last.prev = None
return
node.next.prev = node.prev
node.prev.next = node.next
def __len__(self):
return len(self._dict)
def __contains__(self, key):
return key in self._dict
def __iter__(self):
return iter(self._dict)
def items(self):
return [(key, node.value) for key, node in self._dict.items()]
def values(self):
return [node.value for node in self._dict.values()]
def keys(self):
return self._dict.keys()
#!/usr/bin/env python
# Copyright (C) 2011 Google Inc. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
import unittest
from webkitpy.common import lru_cache
class LRUCacheTest(unittest.TestCase):
def setUp(self):
self.lru = lru_cache.LRUCache(3)
self.lru['key_1'] = 'item_1'
self.lru['key_2'] = 'item_2'
self.lru['key_3'] = 'item_3'
self.lru2 = lru_cache.LRUCache(1)
self.lru2['key_1'] = 'item_1'
def test_items(self):
self.assertEqual(set(self.lru.items()), set([('key_1', 'item_1'), ('key_3', 'item_3'), ('key_2', 'item_2')]))
def test_put(self):
self.lru['key_4'] = 'item_4'
self.assertEqual(set(self.lru.items()), set([('key_4', 'item_4'), ('key_3', 'item_3'), ('key_2', 'item_2')]))
def test_update(self):
self.lru['key_1']
self.lru['key_5'] = 'item_5'
self.assertEqual(set(self.lru.items()), set([('key_1', 'item_1'), ('key_3', 'item_3'), ('key_5', 'item_5')]))
def test_keys(self):
self.assertEqual(set(self.lru.keys()), set(['key_1', 'key_2', 'key_3']))
def test_delete(self):
del self.lru['key_1']
self.assertFalse('key_1' in self.lru)
def test_contain(self):
self.assertTrue('key_1' in self.lru)
self.assertFalse('key_4' in self.lru)
def test_values(self):
self.assertEqual(set(self.lru.values()), set(['item_1', 'item_2', 'item_3']))
def test_len(self):
self.assertEqual(len(self.lru), 3)
def test_size_one_pop(self):
self.lru2['key_2'] = 'item_2'
self.assertEqual(self.lru2.keys(), ['key_2'])
def test_size_one_delete(self):
del self.lru2['key_1']
self.assertFalse('key_1' in self.lru2)
def test_pop_error(self):
self.assertRaises(KeyError, self.lru2.__getitem__, 'key_2')
del self.lru2['key_1']
self.assertRaises(KeyError, self.lru2.__getitem__, 'key_2')
def test_get_middle_item(self):
self.lru['key_2']
self.lru['key_4'] = 'item_4'
self.lru['key_5'] = 'item_5'
self.assertEqual(set(self.lru.keys()), set(['key_2', 'key_4', 'key_5']))
def test_set_again(self):
self.lru['key_1'] = 'item_4'
self.assertEqual(set(self.lru.items()), set([('key_1', 'item_4'), ('key_3', 'item_3'), ('key_2', 'item_2')]))
if __name__ == "__main__":
unittest.main()
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