On Sat, Dec 28, 2002 at 11:24:36PM -0800, R. Joseph Newton wrote:
> I'd say don't bother pack()ing. At the moment, I think the function
> pretty much s**ks. use eval() instead. The following doesn't have
pack and unpack are good for what they are good at. If you need their
functionality, use them - if not don't. Like regular expressions, they
are almost a little language in their own right.
I would suggest not using string eval if you can avoid it. It saves up
all your problems till runtime, and then adds a few.
> that one-liner compactness of the others, but it shows you what is
> going on. The bitwise & does a real cute little trick with its
> operands, evaluating them in hex context or digit-by-digit (I can't
> tell which, and the two may be functionally indistinguishable.)
> Therefore I got results like 192 & 255 = 010 [the nine and five match
> on the 0 bit, no other digits match any bits with their corresponding
> digit in the other number.
These are called bitstrings. The operands are converted to bits using
your native encoding (probably ASCII), and the operator works on those
strings.
> That doesn't quite get us there. Here is my approach:
>
> #!/usr/bin/perl
>
> my ($IP_String, $MaskString) = split(/ +/, $ARGV[0]);
> @IP_Address = ExtractBytes($IP_String);
> @Mask = ExtractBytes($MaskString);
> @NetworkAddress = AND_MaskArray(4, \@IP_Address, \@Mask, $ARGV);
> print
> "$NetworkAddress[0]\.$NetworkAddress[1]\.$NetworkAddress[2]\.$NetworkAddress[3]";
>
> sub ExtractBytes {
> my $DottedString = $_[0];
> @AddressBytes = split (/\./, $DottedString);
> return @AddressBytes;
> }
>
> sub AND_MaskArray {
> $limit = $_[0];
> my @result;
> for (my $i = 0; $i < $limit; $i++) {
> $Temp = eval($IP_Address[$i]) & eval($Mask[$i]);
I suspect you can remove the evals with 0+$IP_Address[$i] & 0+$Mask[$i]
Ugly? Yup.
> $result[$i] = $Temp;
> }
> return @result;
> }
--
Paul Johnson - [EMAIL PROTECTED]
http://www.pjcj.net
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