RE: base64 byte-length formula

[pat_thaler@agilent.com]

Julian,

 

I was using the formula in 12-97 as I stated. The formulas on 12-96 page 70, 12-97 page 71 and 12-98 page 71 all look the same to me. Changing to Martin's formula will solve the problem as would removing the formula altogether.

 

Regards,

Pat

 

 -----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Thursday, June 13, 2002 5:57 AM
To: pat_thaler@agilent.com
Cc: ips@ece.cmu.edu; mkrikis@yahoo.com; owner-ips@ece.cmu.edu
Subject: RE: base64 byte-length formula

Pat, 

I think you are talking 
about the formula in 12-96 and I am talking about the one in 12-98. 
Martins formula and mine are equivalent for 
good encodings. 
As I said I made it up 
only to account for encodings that are in fact impossible - like 1, 4 ... 4*n+1 
base 64 digits. 
And I will  put in 
Martins formula with a note about the impossible numbers. 
Can we stop this thread? 

Julo

pat_thaler@agilent.com 06/13/2002 03:33 AM Please respond to pat_thaler

To:        Julian Satran/Haifa/IBM@IBMIL, mkrikis@yahoo.com         cc:        ips@ece.cmu.edu, owner-ips@ece.cmu.edu         Subject:        RE: base64 byte-length formula

Julian,

The formula in 12-97 is: 
((the integer part 
of)((n+3)*3/4) - m)

Martins formula 3*3/4 where / indictates integer 
divide.

The encoding of 1 octet in base64 results in 2 characters plus 2 
equal
signs. 
n=2, m=2.

Martins formula = 2 *3/4 = 1 (truncated to 
an integer)  right answer

integer part of ((2+3)*3/4)-1 = (integer 
part of 15/4) - 2 = 3 - 2 = 1 right
answer


The encoding of 2 
octets in base64 results in 3 characters plus one equal
sign. 
n=3, 
m=1.

Martins formula = 3 *3/4 = 2 (truncated to an integer)  right 
answer

integer part of ((3+3)*3/4)-1 = (integer part of 18/4) -1 = 4 - 1 
= 3 wrong
answer

The encoding of 3 octets in base64 results in 4 
characters plus no equal
sign. 
n=4, m=0.

Martins formula = 4 *3/4 
= 3 (truncated to an integer)  right answer

integer part of 
((4+3)*3/4)-1 = (integer part of 21/4) -0 = 5 - 1 = 4 
wrong
answer

Pat

-----Original Message-----
From: Julian 
Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Wednesday, June 12, 2002 4:56 
PM
To: Martins Krikis
Cc: ips@ece.cmu.edu; 
owner-ips@ece.cmu.edu
Subject: Re: base64 byte-length 
formula



I said already that your formula is correct. 
I do not 
understand why you say that the 2 formulas are not equivalent for
all the 
lengths (good aor bad)? 
I would appreciate if you respond although you don't 
have to. 

Julo 


Martins Krikis <mkrikis@yahoo.com> 
Sent by: owner-ips@ece.cmu.edu 
06/13/2002 02:34 AM 
Please respond to 
Martins Krikis 
       
       To: 
       Julian Satran/Haifa/IBM@IBMIL 
    
   cc:        ips@ece.cmu.edu 
    
   Subject:        Re: base64 byte-length formula 

      



--- Julian Satran 
<Julian_Satran@il.ibm.com> wrote:

> The difference between our 
formulas is that I
> (mistakenly) took 1 digit as 
> a possible 
string (or 5, 9 etc.)
> For those you need the +3 TERM.
> 
> 
For all the good length 2,3,4 6,7,8 etc the two
> formulas are 
equivalent.

No they are not. They are only equivalent for
n = 0 (mod 
4). So I'm still insisting that
n * 3 / 4 is the simplest right 
formula.

Martins Krikis, Intel Corp.

Disclaimer: these are my 
opinions and
          may not be 
Intel's.


__________________________________________________
Do You 
Yahoo!?
Yahoo! - Official partner of 2002 FIFA World 
Cup
http://fifaworldcup.yahoo.com