stager.py

   1 # Module:       stager.py
   2 # Author:       Eric von Bayer
   3 # Contact:
   4 # Date:         August 18, 2009
   5 # Description:
   6 #     Module to handle deferred callbacks in stages.
   7 #
   8 # Copyright (c) 2009, Eric von Bayer
   9 # All rights reserved.
  10 #
  11 # Redistribution and use in source and binary forms, with or without
  12 # modification, are permitted provided that the following conditions are met:
  13 #
  14 #    * Redistributions of source code must retain the above copyright notice,
  15 #      this list of conditions and the following disclaimer.
  16 #    * Redistributions in binary form must reproduce the above copyright notice,
  17 #      this list of conditions and the following disclaimer in the documentation
  18 #      and/or other materials provided with the distribution.
  19 #    * The names of the contributors may not be used to endorse or promote
  20 #      products derived from this software without specific prior written
  21 #      permission.
  22 #
  23 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  24 # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  26 # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  27 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  29 # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  30 # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  31 # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  32 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  33
  34 # Class to hold a stage
  35 class Stage(object):
  36     """An individual stage to be executed at a later time"""
  37
  38     # Initialize the stage
  39     def __init__(self):
  40         self.__callbacks = list()
  41         self.__done = False
  42
  43     # Execute all the callbacks in the stage
  44     def Execute(self):
  45         if self.__done == False:
  46             self.__done = True
  47             for call in self.__callbacks:
  48                 call()
  49             del self.__callbacks
  50
  51     # Add a callback to the stage
  52     def AddCallback(self, call):
  53         if self.__done == True:
  54             call()
  55         else:
  56             self.__callbacks.append( call )
  57
  58 # Internal storage for the stages
  59 stager_stages = dict()
  60
  61 # Execute the named stage
  62 def Execute(name):
  63     if name in stager_stages:
  64         stager_stages[name].Execute()
  65
  66 # Add a callback to the named stage
  67 def AddCallback(name, call):
  68     if not name in stager_stages:
  69         stager_stages[name] = Stage()
  70
  71     stager_stages[name].AddCallback( call )