Re: Mac Addr to bin

From: Aric Bills (aricb_at_u.wwashingtonn.edu)
Date: 11/04/03 

Date: Tue, 4 Nov 2003 12:54:47 -0800

Hi Jaspal,

> A) If there's only one character in a pair e.g. [A0 0b c 34 7a 9], the
> solution would work better if I can before "join", make each a 2 character
> pair. (How do I?)

There are two things you could do here. The first would be to loop through
the octets to format them correctly:

set hexString ""
foreach octet $macAddr {
    append hexString [ format "%02s" $octet ]
}
set addr [ binary format H12 $hexString ]

The other option is to alter the "formatString" argument to [binary format]
and to use [eval] to break up $macAddr into a set of component arguments:

set addr [ eval binary format H2H2H2H2H2H2 $macAddr ]

If I understand correctly, beginning in Tcl 8.5 it should be possible to use
a leading {expand} instead of [eval] to accomplish the same thing:

set addr [ binary format H2H2H2H2H2H2 {expand}$macAddr ]

> B) In a mac-address, its perfectly legal to have a 00 as any octet i.e.
[00
> 0A 0 b 78 90] and in that case, the string "addr" stops as soon as it
> encounters the first NULL (0x00) - how do I ensure that "addr" is a
variable
> which is independent of the presence of NULL in its value and is always a
6
> character response?

I'm unable to reproduce this error for the test case you provide. [string
length $addr] tells me the binary string is six characters long.

Regards,
Aric