cache.py

   1 # -*- coding: utf-8 -*-
   2 #######################################################################################
   3 #   Photo is a part of Plinn - http://plinn.org                                       #
   4 #   Copyright (C) 2008  Benoît PIN <benoit.pin@ensmp.fr>                              #
   5 #                                                                                     #
   6 #   This program is free software; you can redistribute it and/or                     #
   7 #   modify it under the terms of the GNU General Public License                       #
   8 #   as published by the Free Software Foundation; either version 2                    #
   9 #   of the License, or (at your option) any later version.                            #
  10 #                                                                                     #
  11 #   This program is distributed in the hope that it will be useful,                   #
  12 #   but WITHOUT ANY WARRANTY; without even the implied warranty of                    #
  13 #   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the                     #
  14 #   GNU General Public License for more details.                                      #
  15 #                                                                                     #
  16 #   You should have received a copy of the GNU General Public License                 #
  17 #   along with this program; if not, write to the Free Software                       #
  18 #   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.   #
  19 #######################################################################################
  20 """ Memoization utils
  21
  22 $Id: cache.py 400 2008-07-11 10:31:26Z pin $
  23 $URL: http://svn.luxia.fr/svn/labo/projects/zope/Photo/trunk/cache.py $
  24 """
  25
  26 import inspect
  27 from BTrees.OOBTree import OOBTree
  28
  29 def memoizedmethod(*indexes, **options) :
  30         """ Used as decorator, this function stores result
  31                 of method m inside self._methodResultsCache or
  32                 self._v__methodResultsCache if volatile.
  33                 This decorator may be used inside a class which provides
  34                 a mapping object named _methodResultsCache and / or
  35                 _v__methodResultsCache.
  36
  37                 example :
  38
  39                 1 - simple metdhod memoization
  40
  41                 @memoizedmethod()
  42                 def methodWithNoParameters(self): pass
  43
  44                 2 - indexed memoisation:
  45                 Parameters names are passed to memoizedmethod are
  46                 evaluated to construct an indexed cache.
  47                 Names must be a subset of the memoized method signature.
  48
  49                 @memoizedmethod('arg1', 'arg2')
  50                 def methodWithParameters(self, arg1, arg2=None): pass
  51         """
  52         volatile = options.get('volatile', False)
  53         cacheVarName = '_methodResultsCache'
  54         if volatile==True :
  55                 cacheVarName = '_v_%s' % cacheVarName
  56
  57         def makeMemoizedMethod(m) :
  58                 methodname = m.__name__
  59
  60                 if not indexes :
  61                         def memoizedMethod(self) :
  62                                 if not hasattr(self, cacheVarName) :
  63                                         setattr(self, cacheVarName, OOBTree())
  64                                 cache = getattr(self, cacheVarName)
  65                                 if cache.has_key(methodname) :
  66                                         return cache[methodname]
  67                                 else :
  68                                         res = m(self)
  69                                         cache[methodname] = res
  70                                         return res
  71
  72                         memoizedMethod.__name__ = methodname
  73                         memoizedMethod.__doc__ = m.__doc__
  74                         return memoizedMethod
  75
  76                 else :
  77                         args, varargs, varkw, defaults = inspect.getargspec(m)
  78                         args = list(args)
  79                         if defaults is None :
  80                                 defaults = []
  81                         mandatoryargs = args[1:-len(defaults)]
  82                         optargs = args[-len(defaults):]
  83                         defaultValues = dict(zip([name for name in args[-len(defaults):]], [val for val in defaults]))
  84
  85                         indexPositions = []
  86                         for index in indexes :
  87                                 try :
  88                                         indexPositions.append((index, args.index(index)))
  89                                 except ValueError :
  90                                         raise ValueError("%r argument is not in signature of %r" % (index, methodname))
  91
  92                         if indexPositions :
  93                                 indexPositions.sort(lambda a, b : cmp(a[1], b[1]))
  94
  95                         indexPositions = tuple(indexPositions)
  96
  97
  98                         def memoizedMethod(self, *args, **kw) :
  99                                 # test if m if called by ZPublished
 100                                 if len(args) < len(mandatoryargs) and hasattr(self, 'REQUEST') :
 101                                         assert not kw
 102                                         args = list(args)
 103                                         get = lambda name : self.REQUEST[name]
 104                                         for name in mandatoryargs :
 105                                                 try :
 106                                                         args.append(get(name))
 107                                                 except KeyError :
 108                                                         exactOrAtLeast = defaults and 'exactly' or 'at least'
 109                                                         raise TypeError('%(methodname)s takes %(exactOrAtLeast)s %(mandatoryArgsLength)d argument (%(givenArgsLength)s given)' % \
 110                                                                                         { 'methodname': methodname
 111                                                                                         , 'exactOrAtLeast': exactOrAtLeast
 112                                                                                         , 'mandatoryArgsLength': len(mandatoryargs)
 113                                                                                         , 'givenArgsLength': len(args)})
 114
 115                                         for name in optargs :
 116                                                 get = self.REQUEST.get
 117                                                 args.append(get(name, defaultValues[name]))
 118
 119                                         args = tuple(args)
 120
 121                                 if not hasattr(self, cacheVarName) :
 122                                         setattr(self, cacheVarName, OOBTree())
 123                                 cache = getattr(self, cacheVarName)
 124                                 if not cache.has_key(methodname) :
 125                                         cache[methodname] = OOBTree()
 126
 127                                 cache = cache[methodname]
 128                                 index = aggregateIndex(indexPositions, args)
 129
 130                                 if cache.has_key(index) :
 131                                         return cache[index]
 132                                 else :
 133                                         res = m(self, *args, **kw)
 134                                         cache[index] = res
 135                                         return res
 136
 137                         memoizedMethod.__name__ = methodname
 138                         memoizedMethod.__doc__ = m.__doc__
 139                         return memoizedMethod
 140
 141         return makeMemoizedMethod
 142
 143 def aggregateIndex(indexPositions, args):
 144         '''
 145         Returns the index to be used when looking for or inserting
 146         a cache entry.
 147         view_name is a string.
 148         local_keys is a mapping or None.
 149         '''
 150
 151         agg_index = []
 152
 153         for name, pos in indexPositions :
 154                 val = args[pos-1]
 155                 agg_index.append((name, str(val)))
 156
 157         return tuple(agg_index)