Subversion Repositories programming

#!/usr/bin/env python

#
# Copyright 2006, Ira W. Snyder (devel@irasnyder.com)
# License: GNU GPL v2 (or, at your option, any later version)
#

# Print structure description:
# ===============================================
# desc = { TYPE1 : func1, TYPE2 : func2, ... }
#
# Each type will be a unique key (enforced by the dict)
# Each func will be a pointer to a function.

import errno

class PrintSystem (object):
        """A very generic printing system. This class allows you to specify a
           structure that describes your printing system, and it will handle
           any further messages sent to it."""

        def __init__ (self, description):
                self.__description = description

        def __default_action (self, mytype, mydata):
                print 'ERROR: no action for: type=%s data=%s' % (str(mytype), str(mydata))

        def mprint (self, message):
                """Print a message according to our description.

                   It should be in the form (TYPE, ...)"""

                # If there is no type in the message, it must be invalid
                if len(message) < 1:
                        return -errno.EINVAL

                mytype = message[0]  # the first element is the type
                mydata = message[1:] # the rest is the data

                # If we don't have a valid function to use, this message
                # must be invalid
                if mytype not in self.__description.keys():
                        self.__default_action (mytype, mydata)
                        return -errno.EINVAL

                # Looks like we're good, call the correct function
                # with the data given
                try:
                        self.__description[mytype](mydata)
                except:
                        print 'Had an exception while trying to print what appeared to'
                        print 'be a valid message. The message was:'
                        self.__default_action (mytype, mydata)
                        return -errno.EINVAL

                # We got here, so we completed successfully!
                return 0


################################################################################
# Test material is below
################################################################################


def f1 (data):
        (a, b, c) = data
        print 'in f1 a=%d b=%d c=%d' % (a, b, c)

def f2 (data):
        (a, b) = data
        print 'in f2 a=%s b=%s' % (a, b)

def f3 (data):
        print 'no data for f3'

def main():
        ( TYPE1, TYPE2, TYPE3 ) = range(3)
        mystruct = { TYPE1 : f1, TYPE2 : f2, TYPE3 : f3 }

        ps = PrintSystem (mystruct)

        print 'All here should succeed:'
        ps.mprint ((TYPE1, 1, 2, 3))
        ps.mprint ((TYPE2, 'hello', 'world'))
        ps.mprint ((TYPE3,))
        ps.mprint ((TYPE1, 2, 3, 4))

        print '\nShould fail here:'
        ps.mprint ((20, 'a', 'b', 'c'))

if __name__ == '__main__':
        # Run test code
        main ()