Re: Re: Re: Re: 64 bit pointer to string

Thanks for helping!
Your code does the right thing and works. I think Perl5/OpenBSD 64bit does not like this pointer for its IOCTLs ...
BTW this is the whole code:

  my $tocentry;
  my $toc="";
  my $size=0;
  for(@tracks) {
    $toc.="        ";
    $size+=8;
  }

  if($os =~ /BSD/) {
    my $size_hi=int($size / 256);
    my $size_lo=$size & 255;

    if($BIG_ENDIAN) {
      # in 32bit: $tocentry=pack "CCCCP8l", $CDROM_MSF,0,$size_hi,$siz
+e_lo,$toc;
      $tocentry=pack "CCCCP", $CDROM_MSF,0,$size_hi,$size_lo,$toc; # c
+urrent version
    } else {
      $tocentry=pack "CCCCP8l", $CDROM_MSF,0,$size_lo,$size_hi,$toc;
    }
    ioctl(CD, $CDROMREADTOCENTRY, $tocentry) or die "cannot read track
+ info [$!] [$device]";
  }
[download]

Should I post in p5p?

Comment on Re: Re: Re: Re: 64 bit pointer to string Download Code

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Re: Re: Re: Re: Re: 64 bit pointer to string by BrowserUk (Patriarch) on Sep 06, 2003 at 11:35 UTC
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.	[reply] [d/l]
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!	[reply] [d/l]