[ENH][VM][TEST] Adler32 crc primitive

Andreas Raab andreas.raab at gmx.de
Wed Feb 18 20:41:54 UTC 2004


See RFC1950:

ADLER32 (Adler-32 checksum)
         This contains a checksum value of the uncompressed data
         (excluding any dictionary data) computed according to Adler-32
         algorithm. This algorithm is a 32-bit extension and improvement
         of the Fletcher algorithm, used in the ITU-T X.224 / ISO 8073
         standard. See references [4] and [5] in Chapter 3, below)

         Adler-32 is composed of two sums accumulated per byte: s1 is
         the sum of all bytes, s2 is the sum of all s1 values. Both sums
         are done modulo 65521. s1 is initialized to 1, s2 to zero.  The
         Adler-32 checksum is stored as s2*65536 + s1 in most-
         significant-byte first (network) order.
  - Andreas----- Original Message ----- 
From: "ducasse" <ducasse at iam.unibe.ch>
To: "The general-purpose Squeak developers list"
<squeak-dev at lists.squeakfoundation.org>
Sent: Wednesday, February 18, 2004 9:35 PM
Subject: Re: [ENH][VM][TEST] Adler32 crc primitive


hi andreas

just for fun I was reading your changeset and the tests. Because I
wanted to know if I could understand something
from the tests. In 2 min this is not enough but this gives a really
good impression.

By curiosity what means adler?

Stef

On 18 févr. 04, at 21:19, Andreas Raab wrote:

> Looks like we need this ... at this point we're spending nearly half
> of the
> overall time for ZLibStream's compression/decompression in crc
> computations.
> The attached primitive should fix the problem and the tests should
> make sure
> it actually works :-)
> <Adler32Primitive.1.cs>





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