Checksum routine - new to Python

[Dale Strickland-Clark]

Thanks for the replies.

MD5 looks interesting.

--
Dale Strickland-Clark
Out-Think Ltd, UK

Dale Strickland-Clark <dale at out-think.NOSPAMco.uk> wrote in message
news:8g1no6$8uc$1 at supernews.com...
> I need a little checksum routine as part of a larger project. I've written
> the one below, which basically works, but it only produces a 32 bit
> checksum. I'd prefer a 64 bit checksum but don't know how to code it in
> Python. I can't get 'logical and' with >31 bits to work.
>
> This code might look unusual but some of the files I'm checksumming have
> long strings of binary zeros at the end which were having the effect of
> clearing out the checksum. Also this code will handle files that are all
> zeros and still yield a useful result.
>
> If there is a Python library with something suitable, I'll happily use
that
> instead.
>
> Thanks for any advice/help.
>
> def CheckSum(filepath):
>
>     file = open(filepath, "rb")
>
>     chksum = 0L
>     toggle = 0
>
>     allfile = file.read()
>     i = 0
>     while i < len(allfile):
>         ch = allfile[i]
>         if ord(ch) > 0:
>             if toggle: chksum = chksum << 1
>             chksum = chksum + ord(ch)
>             chksum = chksum & 0X7fffffff
>             toggle = not toggle
>         else:
>             chksum = chksum + 1
>         i = i + 1
>
>     return chksum
>
>
> --
> Dale Strickland-Clark
> Out-Think Ltd, UK
>
>
>