[plt-scheme] BitField

From: Paulo Jorge O. C. Matos (pocm at mega.ist.utl.pt)
Date: Sat Nov 2 09:41:48 EST 2002


I have to check out your references. No, I saw the bitwise operations 
but I also tried to implemented SHA-1 hashing algorithm that uses alot 
of shifts, etc. How do you manage to do a shift with the bitwise 
operations available?

Best regards,


Jens Axel Søgaard wrote:
>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> Paulo Jorge O. C. Matos wrote:
>> Last week I was in need to control bits to implement RC4 private key 
>> algorithm in 
>> PLTScheme and I was not able to find something that would allow me to 
>> check 
>> bits and move them around, etc so I created a little module of 
>> bitfield operations.
>> Unfortunately I think it could be better but had no better idea. The 
>> library is at:
>> http://mega.ist.utl.pt/~pocm/bitfield.ss
> I think you missed the bitwise operations. At first I overlooked them 
> too, when
> I implemented the md5 algorithm:
>    http://www.scheme.dk/md5/md5.html
> If you try it, then use time to see the difference between the builtin 
> operations
> and the userdefined. There is a world of difference.
> Take also a look at Olin Shivers proposal for an integer bitwise-operation
> library:
>    http://srfi.schemers.org/srfi-33/srfi-33.txt
> This looks very nice.

Paulo J. Matos : pocm(_at_)mega.ist.utl.pt
Instituto Superior Tecnico - Lisbon
Software & Computer Engineering - A.I.
  - > http://mega.ist.utl.pt/~pocm
	Yes, God had a deadline...
		So, He wrote it all in Lisp!

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