CRC16 in erlang

[Thomas Lindgren]

--- Rudolph van Graan <rvg@REDACTED> wrote:

> Hi Joe,
> 
> Here is one which I wrote some time ago. It does
> work, but there  
> might be some issues. (No guarantees on speed!)

Here is an easy speedup:

-define(CRC16Def, {...}).

crc_index(N) -> element(N+1, ?CRC16Def).

This is O(1) time rather than O(N) and 1/2 the space
of the original definition. Pretty good, but there's
more.

Even better: pass around CRC_tab as a parameter and
you save allocating 256 words (+ up to 256 bignums; I
can't find the size of a bignum at the moment, but
perhaps a further 2 words/bignum?) per indexing
operation :-)

Best,
Thomas


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