SPUG: pack and unpack

[Ben Reser]

On Wed, Aug 27, 2003 at 04:03:16PM -0700, Richard Wood wrote:
> Right, 
> 
> Got the "Z" working on a machine with a newer version
> of perl (doesn't work on was 5.004_04, does work on
> 5.005_03).  I only have second edition of Camel.  I
> will take a look at third edition tonight.
> 
> All of my LONGs are coming out 808464432 and all of my
> SHORTS are coming out 12336.  I will figure this out
> sooner or later. 
> 
> Sorry I can't send a file.  They belong to a local
> airplane company and I am not at liberty to transmit
> them.
> 
> elsif ($type == 3) {                       # SHORT
>        $decoded_value =unpack "n", $value;
>     } elsif ($type == 4) {                 # LONG
>        $decoded_value = unpack "N", $value;
>     }

I don't know what I was thinking when I wrote that sample code,
This will work better (I hope):

seek(TIF, $offset, 0) or die "Seek $i: $!\n";                                   
read(TIF, $buffer, 8);                                                         
($tag, $type, $count, $value) = unpack "nnN", $buffer;                       
read(TIF, $buffer, 4);
if ($type == 1) {                                                               
  $value = unpack "C", $buffer;                                          
} elsif ($type == 2) {                                                          
  $value = unpack "Z$count", $buffer;                                    
} elsif ($type == 3) {                                                          
  $value =unpack "n", $buffer;                                           
} elsif ($type == 4) {                                                          
  $value = unpack "N", $buffer;                                          
...                                                                             

Can't imagine who that local airplane company might be... :)

-- 
Ben Reser <ben at reser.org>
http://ben.reser.org

"What upsets me is not that you lied to me, but that from now on I can
no longer believe you." -- Nietzsche