Package pyxmpp :: Module expdict |
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# Source Code for Module pyxmpp.expdict

      1  #
      2  # (C) Copyright 2003-2010 Jacek Konieczny <jajcus@jajcus.net>
      3  #
      4  # This program is free software; you can redistribute it and/or modify
      5  # it under the terms of the GNU Lesser General Public License Version
      6  # 2.1 as published by the Free Software Foundation.
      7  #
      8  # This program is distributed in the hope that it will be useful,
      9  # but WITHOUT ANY WARRANTY; without even the implied warranty of
     10  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     11  # GNU Lesser General Public License for more details.
     12  #
     13  # You should have received a copy of the GNU Lesser General Public
     14  # License along with this program; if not, write to the Free Software
     15  # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
     16  #
     17
     18  """Dictionary with item expiration."""
     19
     20  __docformat__="restructuredtext en"
     21
     22  import time
     23  import threading
     24
     25  __all__ = ['ExpiringDictionary']
     26
     27  sentinel = object()
     28
     29 -class ExpiringDictionary(dict):
     30      """An extension to standard Python dictionary objects which implements item
     31      expiration.
     32
     33      Each item in ExpiringDictionary has its expiration time assigned, after
     34      which the item is removed from the mapping.
     35
     36      :Ivariables:
     37          - `_timeouts`: a dictionary with timeout values and timeout callback for
     38            stored objects.
     39          - `_default_timeout`: the default timeout value (in seconds from now).
     40          - `_lock`: access synchronization lock.
     41      :Types:
     42          - `_timeouts`: `dict`
     43          - `_default_timeout`: `int`
     44          - `_lock`: `threading.RLock`"""
     45
     46      __slots__=['_timeouts','_default_timeout','_lock']
     47
     48 -    def __init__(self,default_timeout=300):
     49          """Initialize an `ExpiringDictionary` object.
     50
     51          :Parameters:
     52              - `default_timeout`: default timeout value for stored objects.
     53          :Types:
     54              - `default_timeout`: `int`"""
     55          dict.__init__(self)
     56          self._timeouts={}
     57          self._default_timeout=default_timeout
     58          self._lock=threading.RLock()
     59
     60 -    def __delitem__(self,key):
     61          self._lock.acquire()
     62          try:
     63              del self._timeouts[key]
     64              return dict.__delitem__(self,key)
     65          finally:
     66              self._lock.release()
     67
     68 -    def __getitem__(self,key):
     69          self._lock.acquire()
     70          try:
     71              self._expire_item(key)
     72              return dict.__getitem__(self,key)
     73          finally:
     74              self._lock.release()
     75
     76 -    def pop(self,key,default=sentinel):
     77          self._lock.acquire()
     78          try:
     79              self._expire_item(key)
     80              del self._timeouts[key]
     81              if default is not sentinel:
     82                  return dict.pop(self,key,default)
     83              else:
     84                  return dict.pop(self,key)
     85          finally:
     86              self._lock.release()
     87
     88 -    def __setitem__(self,key,value):
     89          return self.set_item(key,value)
     90
     91 -    def set_item(self,key,value,timeout=None,timeout_callback=None):
     92          """Set item of the dictionary.
     93
     94          :Parameters:
     95              - `key`: the key.
     96              - `value`: the object to store.
     97              - `timeout`: timeout value for the object (in seconds from now).
     98              - `timeout_callback`: function to be called when the item expires.
     99                The callback should accept none, one (the key) or two (the key
    100                and the value) arguments.
    101          :Types:
    102              - `key`: any hashable value
    103              - `value`: any python object
    104              - `timeout`: `int`
    105              - `timeout_callback`: callable"""
    106          self._lock.acquire()
    107          try:
    108              if not timeout:
    109                  timeout=self._default_timeout
    110              self._timeouts[key]=(time.time()+timeout,timeout_callback)
    111              return dict.__setitem__(self,key,value)
    112          finally:
    113              self._lock.release()
    114
    115 -    def expire(self):
    116          """Do the expiration of dictionary items.
    117
    118          Remove items that expired by now from the dictionary."""
    119          self._lock.acquire()
    120          try:
    121              for k in self._timeouts.keys():
    122                  self._expire_item(k)
    123          finally:
    124              self._lock.release()
    125
    126 -    def _expire_item(self,key):
    127          """Do the expiration of a dictionary item.
    128
    129          Remove the item if it has expired by now.
    130
    131          :Parameters:
    132              - `key`: key to the object.
    133          :Types:
    134              - `key`: any hashable value"""
    135          (timeout,callback)=self._timeouts[key]
    136          if timeout<=time.time():
    137              item = dict.pop(self, key)
    138              del self._timeouts[key]
    139              if callback:
    140                  try:
    141                      callback(key,item)
    142                  except TypeError:
    143                      try:
    144                          callback(key)
    145                      except TypeError:
    146                          callback()
    147
    148  # vi: sts=4 et sw=4
    149