in reply to Re: Re: Re: Re: 64 bit pointer to string
in thread 64 bit pointer to string

I wouldn't run off to p5p just yet...but that's me, you may get better and/or quicker answers there from someone who has a 64-bit system to play with. That said, of you go there, do so via the perl5porters@perl.com list rather than perlbug as what my snippet did prove is that this isn't a perlbug. Your just using it wrong:)

One thing I notice is that you are attempting to pack a 16-bit numeric value by splitting it into two 8-bit values and using 'CC' and switching the bytes around to account for the endianess of the current system.

A) I think that you are doing this wrongly.

B) There is no need for you to do this sort of thing yourself. pack already has that smarts built-in, although it requires you to pass along some clue bats to enable it.

pack has format specifiers 'n' and 'v' which will pack a 16-bit unsigned value from a number in a perl scalar, in either big-endian or little-endian format respectively.

Also, you don't show where or how your $BIG_ENDIAN variable is being set, but you should take a look at the Config package which is a part of the standard distribution. In particular 

use Config;

print $Config{ byteorder };

[download]

will tell you the order of the bytes on the current system. It will probably return somethng like '12345678' or '78563412' on your system.

Hope this helps.

Update: You might also want to check out perlpacktut. It's about the best tutorial i've seen on pack. You may have a local copy, but it is fairly recent addition to the doc set,so the link above may help.

Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller
If I understand your problem, I can solve it! Of course, the same can be said for you.

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Re: 64 bit pointer to string
by Anonymous Monk on Sep 06, 2003 at 17:29 UTC
    ok I may be using it wrongly with 64bit but it works flawlessly witth 32bit big and little endian. however it MAY be a perl bug considering the 'ioctl' command not the packing itself.

    ad A) it works ;-)
    ad B) I know that, but I had more problems with that than without
    I'm using: 

    my $BIG_ENDIAN = unpack("h*", pack("s", 1)) =~ /01/;

if($BIG_ENDIAN) {
  print STDERR "[big endian]\n" if $debug;
} else {
  print STDERR "[little endian]\n" if $debug;
}

    [download]
    never failed so far.
    Thanks for the pointer to perlpacktut, I'll try a bit more before mailing anyone. But I definitely don't see why 64bit should not work like 32bit in this regard. Maybe I'm doing it wrong all the time, and it works on 32bit big/little endian by chance. Well I don't think that either ;-)

    Thanks!

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