counter.py

# Copyright (c) Charl P. Botha, TU Delft.
# All rights reserved.
# See COPYRIGHT for details.

# I could have done this with just a module variable, but I found this
# Borg thingy too nice not to use.  See:
# http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66531

class CounterBorg:
    """Borg-pattern (similar to a Singleton) for maintaining a
    monotonically increasing counter.

    Instantiate this anywhere, and call get() to return and increment
    the increasing counter.  DeVIDE uses this to stamp modified and
    execute times of modules.
    """

    # we start with 1, so that client code can init to 0 and guarantee
    # an initial invalid state.  The counter is explicitly long, this
    # gives us unlimited precision (up to your memory limits, YEAH!)
    __shared_state = {'counter' : 1L}

    def __init__(self):
        self.__dict__ = self.__shared_state

    def get(self):
        c = self.counter
        self.counter += 1
        return c

def counter():
    return CounterBorg().get()