root/galaxy-central/eggs/Cheetah-2.2.2-py2.6-macosx-10.6-universal-ucs2.egg/Cheetah/CacheRegion.py

リビジョン 3, 4.3 KB (コミッタ: kohda, 14 年 前)

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1# $Id: CacheRegion.py,v 1.3 2006/01/28 04:19:30 tavis_rudd Exp $
2'''
3Cache holder classes for Cheetah:
4
5Cache regions are defined using the #cache Cheetah directive. Each
6cache region can be viewed as a dictionary (keyed by cacheRegionID)
7handling at least one cache item (the default one). It's possible to add
8cacheItems in a region by using the `varyBy` #cache directive parameter as
9in the following example::
10   #def getArticle
11      this is the article content.
12   #end def
13
14   #cache varyBy=$getArticleID()
15      $getArticle($getArticleID())
16   #end cache
17
18The code above will generate a CacheRegion and add new cacheItem for each value
19of $getArticleID().
20'''
21
22try:
23    from hashlib import md5
24except ImportError:
25    from md5 import md5
26
27import time
28import Cheetah.CacheStore
29
30class CacheItem(object):
31    '''
32    A CacheItem is a container storing:
33
34        - cacheID (string)
35        - refreshTime (timestamp or None) : last time the cache was refreshed
36        - data (string) : the content of the cache
37    '''
38   
39    def __init__(self, cacheItemID, cacheStore):
40        self._cacheItemID = cacheItemID
41        self._cacheStore = cacheStore
42        self._refreshTime = None
43        self._expiryTime = 0
44
45    def hasExpired(self):
46        return (self._expiryTime and time.time() > self._expiryTime)
47   
48    def setExpiryTime(self, time):
49        self._expiryTime = time
50
51    def getExpiryTime(self):
52        return self._expiryTime
53
54    def setData(self, data):
55        self._refreshTime = time.time()
56        self._cacheStore.set(self._cacheItemID, data, self._expiryTime)
57
58    def getRefreshTime(self):
59        return self._refreshTime
60
61    def getData(self):
62        assert self._refreshTime
63        return self._cacheStore.get(self._cacheItemID)
64
65    def renderOutput(self):
66        """Can be overridden to implement edge-caching"""
67        return self.getData() or ""
68
69    def clear(self):
70        self._cacheStore.delete(self._cacheItemID)
71        self._refreshTime = None
72
73class _CacheDataStoreWrapper(object):
74    def __init__(self, dataStore, keyPrefix):
75        self._dataStore = dataStore
76        self._keyPrefix = keyPrefix
77       
78    def get(self, key):
79        return self._dataStore.get(self._keyPrefix+key)
80
81    def delete(self, key):
82        self._dataStore.delete(self._keyPrefix+key)
83
84    def set(self, key, val, time=0):       
85        self._dataStore.set(self._keyPrefix+key, val, time=time)
86
87class CacheRegion(object):
88    '''
89    A `CacheRegion` stores some `CacheItem` instances.
90
91    This implementation stores the data in the memory of the current process.
92    If you need a more advanced data store, create a cacheStore class that works
93    with Cheetah's CacheStore protocol and provide it as the cacheStore argument
94    to __init__.  For example you could use
95    Cheetah.CacheStore.MemcachedCacheStore, a wrapper around the Python
96    memcached API (http://www.danga.com/memcached).
97    '''
98    _cacheItemClass = CacheItem
99   
100    def __init__(self, regionID, templateCacheIdPrefix='', cacheStore=None):
101        self._isNew = True
102        self._regionID = regionID
103        self._templateCacheIdPrefix = templateCacheIdPrefix
104        if not cacheStore:
105            cacheStore = Cheetah.CacheStore.MemoryCacheStore()
106        self._cacheStore = cacheStore
107        self._wrappedCacheDataStore = _CacheDataStoreWrapper(
108            cacheStore, keyPrefix=templateCacheIdPrefix+':'+regionID+':')
109        self._cacheItems = {}
110
111    def isNew(self):
112        return self._isNew
113       
114    def clear(self):
115        " drop all the caches stored in this cache region "
116        for cacheItemId in self._cacheItems.keys():
117            cacheItem = self._cacheItems[cacheItemId]
118            cacheItem.clear()
119            del self._cacheItems[cacheItemId]
120       
121    def getCacheItem(self, cacheItemID):
122        """ Lazy access to a cacheItem
123
124            Try to find a cache in the stored caches. If it doesn't
125            exist, it's created.
126           
127            Returns a `CacheItem` instance.
128        """
129        cacheItemID = md5(str(cacheItemID)).hexdigest()
130       
131        if not self._cacheItems.has_key(cacheItemID):
132            cacheItem = self._cacheItemClass(
133                cacheItemID=cacheItemID, cacheStore=self._wrappedCacheDataStore)
134            self._cacheItems[cacheItemID] = cacheItem
135            self._isNew = False
136        return self._cacheItems[cacheItemID]
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