[fpc-pascal] Fast CRC functions?

Tony Whyman tony.whyman at mccallumwhyman.com
Mon Sep 1 11:49:32 CEST 2014

Certainly true, but doesn't necessarily invalidate my comment.

The zip format is an interesting case and it would be of (academic)
interest to know if Phil Katz used a 32 bit CRC after researching
alternatives - or simply because CRCs are widely used.

On the other hand, if you get a bit error in compressed data then the
Deflate algorithm will tend to replicate and magnify the error as it
decompresses the message resulting in a very different outcome to the
original message. Hence any half decent checksum whether CRC or
otherwise should pick up the error.

On 01/09/14 10:29, Michael Schnell wrote:
> On 09/01/2014 10:12 AM, Tony Whyman wrote:
>> CRCs only
>> really have the edge with communications because the error pattern is
>> typically known for a given communications medium and the CRC can be
>> tuned to the media in order to give better performance.
> Even in software-only applications, CRCs are used rather ubiquitously.
> e.g. ZIP uses CRC 32.
> -Michael
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