[Jprogramming] 128!:3

[Raul Miller]

It's probably worthwhile starting from a "known" starting point.

So I selected CRC32 (which pre-filled a lot of fields), and gave it the text:

The quick brown fox jumps over the lazy dog

"Calculate" with that setup gave me the result 414FA339.

This matches http://rosettacode.org/wiki/CRC#J

So I would assume that the underlying implementations match.

Reading out the tweakable settings for this case, I see:

CRC Order: 32
CRC Polynom: 4C11DB7
Initial value: FFFFFFFF
(checked) direct
Final XOR value: FFFFFFFF
(checked) reverse data bytes
(checked) reverse CRC result before Final XOR

I hope this helps,

--
Raul


On Thu, Apr 16, 2015 at 9:50 AM, 'Pascal Jasmin' via Programming
<programming at jsoftware.com> wrote:
> for say this calculator,
> http://www.bobtech.ro/tutoriale/porturi-si-interfete/51-crc-calculator
>
> what x value will provide the same result to the result box, for data sequence '123456789'?
>
> The values that I am trying (which don't match):
>
> CRC order         32
>
> CRC polynom       4C11DB7
>
> Initial value     FFFFFFFF
>
> Final XOR value   FFFFFFFF (or 0)
>
>   hfd  (16b04c11db7;_1)&(128!:3) '123456789'
> c4f2be9
>
>
>
>
>
> ----- Original Message -----
> From: Raul Miller <rauldmiller at gmail.com>
> To: Programming forum <programming at jsoftware.com>
> Cc:
> Sent: Thursday, April 16, 2015 2:49 AM
> Subject: Re: [Jprogramming] 128!:3
>
> What do you mean by "not match"?
>
> (Specifically.)
>
> Thanks,
>
> --
> Raul
>
> On Wed, Apr 15, 2015 at 11:34 PM, 'Pascal Jasmin' via Programming
> <programming at jsoftware.com> wrote:
>> that helped,
>>
>> 128!:3 can do any of the functions here:
>>
>> http://en.wikipedia.org/wiki/Polynomial_representations_of_cyclic_redundancy_checks
>>
>>
>> The default x value
>>
>>   hfd _306674912
>> edb88320
>>
>>
>> and is "reverse crc-32"
>>
>> 16b04c11db7 is "normal crc 32"
>>
>> This does not seem to match online crc 32 calculators though.
>>
>>
>> ----- Original Message -----
>> From: Raul Miller <rauldmiller at gmail.com>
>> To: Programming forum <programming at jsoftware.com>
>> Cc:
>> Sent: Wednesday, April 15, 2015 6:19 PM
>> Subject: Re: [Jprogramming] 128!:3
>>
>> 128!:3 has width=32 and init=16ffffffff
>>
>> Here's the CRC32 checksum (which has poly 0x04c11db7) using 128!:3:
>>
>>    (#.|.(32#:2)#:016b04c11db7)&(128!:3)
>>
>> That said,, I don't see any examples (starting text, ending checksum)
>> so it would be tedious to determine whether the default 128!:3
>> polynomial has an exact equivalence.
>>
>> Thanks,
>>
>> --
>> Raul
>>
>> On Wed, Apr 15, 2015 at 5:28 PM, 'Pascal Jasmin' via Programming
>> <programming at jsoftware.com> wrote:
>>> is there a named algorithm equivalence of 128!:3 to one in this list ?
>>>
>>>
>>> http://reveng.sourceforge.net/crc-catalogue/all.htm
>>>
>>> I understand its crc32, but there are several.
>>>
>>> Also I note that to get the documentation's result I need to take the 2s complement
>>>
>>>   ]&.(2&#. inv) 128!:3 'assiduously avoid any and all asinine alliterations'
>>> 1439575093
>>>
>>> (j8.02 64 and j6.01 32)
>>> ----------------------------------------------------------------------
>>> For information about J forums see http://www.jsoftware.com/forums.htm
>
>>
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