binary file compare...

Martin martin at marcher.name
Wed Apr 15 15:25:27 CEST 2009


On Wed, Apr 15, 2009 at 11:03 AM, Steven D'Aprano
<steven at remove.this.cybersource.com.au> wrote:
> The checksum does look at every byte in each file. Checksumming isn't a
> way to avoid looking at each byte of the two files, it is a way of
> mapping all the bytes to a single number.

My understanding of the original question was a way to determine
wether 2 files are equal or not. Creating a checksum of 1-n files and
comparing those checksums IMHO is a valid way to do that. I know it's
a (one way) mapping between a (possibly) longer byte sequence and
another one, how does checksumming not take each byte in the original
sequence into account.

I'd still say rather burn CPU cycles than development hours (if I got
the question right), if not then with binary files you will have to
find some way of representing differences between the 2 files in a
readable manner anyway.

> Hashing is a *lot* more work than just comparing two bytes. The MD5
> checksum has been specifically designed to be fast and compact, and the
> algorithm is still complicated:

I know that the various checksum algorithms aren't exactly cheap, but
I do think that just to know wether 2 files are different a solution
which takes 5mins to implement wins against a lengthy discussion which
optimizes too early wins hands down.

regards,
martin

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