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app/django/utils/checksums.py
author Daniel Bentley <dbentley@google.com>
Sun, 12 Apr 2009 09:06:45 +0000
branchgae-fetch-limitation-fix
changeset 2313 c39a81bce1bd
parent 54 03e267d67478
permissions -rw-r--r--
Use offset_linkid instead of offset to scan >1000 entities. this is a first-cut. It works in all the ways I could make earlier versions fail. It passes link_id as URL parameters. It also has a new class LinkCreator which makes the main body of getListContents even easier to write. I wasn't sure if link_id's could have non alphanumeric characters; if so, they need to be URL encoded/decoded. I also need to go and remove any mention of raw offsets now, because we don't use them. I believe I've talked about this approach with a few of you and it sounded reasonable. Feel free to roll-back/fix/amend/comment-for-me-to-fix. This is my first big-logic-change to Melange. Patch by: Dan Bentley
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03e267d67478 Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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"""
03e267d67478 Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
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Common checksum routines (used in multiple localflavor/ cases, for example).
03e267d67478 Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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     3
 
"""
03e267d67478 Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




     5


__all__ = ['luhn',]













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

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03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




     7


LUHN_ODD_LOOKUP = (0, 2, 4, 6, 8, 1, 3, 5, 7, 9) # sum_of_digits(index * 2)













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




     8














03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




     9


def luhn(candidate):













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

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    """













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




    11


    Checks a candidate number for validity according to the Luhn













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




    12


    algorithm (used in validation of, for example, credit cards).













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




    13


    Both numeric and string candidates are accepted.













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
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    """













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
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    if not isinstance(candidate, basestring):













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




    16


        candidate = str(candidate)













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
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    17


    try:













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
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    18


        evens = sum([int(c) for c in candidate[-1::-2]])













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




    19


        odds = sum([LUHN_ODD_LOOKUP[int(c)] for c in candidate[-2::-2]])













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

diff
changeset




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        return ((evens + odds) % 10 == 0)













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

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    except ValueError:  # Raised if an int conversion fails













03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine



Todd Larsen <tlarsen@google.com>


parents: 

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    22


        return False















py_tasks_melange