Re: Do Storable and IO::Zlib like to play together?

Solving this is going to take some effort. Here is a small piece of code that reproduces the error:

#!/usr/bin/perl

use Storable qw(nstore_fd fd_retrieve);
use IO::Zlib;
use Data::Dumper;

my $test = { foo => "bar" };

my $fh = IO::Zlib->new("out.gz", "wb");
nstore_fd($test, $fh);
$fh->close;

my $fh2 = IO::Zlib->new("out.gz", "rb");
my $href = fd_retrieve($fh2);
$fh2->close;

print Dumper $href;
[download]

The error (message) is the same but I'm not positive the error itself is. In particular, $AUTOLOAD in this instance is IO::Zlib::FILENO (not READ) and it is being called from Storable::_store_fd (which is in _store_fd.al) which is in turn being called by Storable::nstore_fd (in nstore_fd.al)... But, going back and printing the argument when in each of those functions shows it to be IO::Zlib=GLOB(0x81242f8) which is a glob ref as desired. It is only when we get to Zlib's AUTOLOAD that it prints as IO::Zlib=HASH(0x81b84b8). So, it looks like the call to fileno() in _store_fd() is where things are breaking.

And, sure enough...

perl -MIO::Zlib -e '$fh = IO::Zlib->new("test.gz", "wb"); print fileno
+($fh)'
[download]

That's a minimal demonstration of the problem. (So, you can stop looking at Storable as the real problem, anyway.)

Adding some quick prints to see what's going on...

sub AUTOLOAD
{ print "AUTOLOAD(@_)\n";
    my $self = shift;
print $self, " $AUTOLOAD\n@{[caller]}\n";
    $AUTOLOAD =~ s/.*:://;
    $AUTOLOAD =~ tr/a-z/A-Z/;

    return tied(*{$self})->$AUTOLOAD(@_);
}
[download]

And running that:

$ perl -MIO::Zlib -e '$fh = IO::Zlib->new("test.gz", "wb"); print file
+no($fh)'
AUTOLOAD(IO::Zlib=HASH(0x81e8b30))
IO::Zlib=HASH(0x81e8b30) IO::Zlib::FILENO 
main -e 1
Not a GLOB reference at /usr/lib/perl5/site_perl/5.8.0/IO/Zlib.pm line
+ 566.
[download]

Changing fileno($fh) to $fh->fileno results in:

$ perl -MIO::Zlib -e '$fh = IO::Zlib->new("test.gz", "wb"); print $fh-
+>fileno'
AUTOLOAD(IO::Zlib=GLOB(0x8124538))
IO::Zlib=GLOB(0x8124538) IO::Zlib::fileno
main -e 1
AUTOLOAD(IO::Zlib=HASH(0x81e8b3c))
IO::Zlib=HASH(0x81e8b3c) IO::Zlib::ILENO
IO::Zlib /usr/lib/perl5/site_perl/5.8.0/IO/Zlib.pm 566
Not a GLOB reference at /usr/lib/perl5/site_perl/5.8.0/IO/Zlib.pm line
+ 566.
[download]

Ick! Where's that "IO::Zlib::ILENO" coming from?

Oh well, that's where I'm at now. I've got to set it down for a bit as I have real paying work to do. :-) Maybe you or someone else would like to pick up there. I'll look deeper later on if no one else nails it.

-sauoq
"My two cents aren't worth a dime.";

Comment on Re: Do Storable and IO::Zlib like to play together? Select or Download Code

Replies are listed 'Best First'.
Re^2: Do Storable and IO::Zlib like to play together? by fokat (Deacon) on Nov 03, 2005 at 19:52 UTC
Thanks sauoq. That's a minimal demonstration of the problem. Yep. I guess we arrived to the problem quite close. IO::Zlib does not seem to implement `fileno`. But even after faking it (as shown in my Updated node), there is something else going bad. (So, you can stop looking at Storable as the real problem, anyway.) Well, I don't understand why Storable wants to verify that it got a real handle. It should try to do its thing with whatever it got as an argument. But in this case, this does not look like the cause. Best regards -lem, but some call me fokat	[reply]
Re^3: Do Storable and IO::Zlib like to play together? by sauoq (Abbot) on Nov 03, 2005 at 19:58 UTC
IO::Zlib does not seem to implement fileno. That's not really the problem, I don't think. At least, not the first one. We are never getting out of AUTOLOAD routine (and not because a method is missing.) The problem is that a call to fileno() doesn't play well with the tied handle provided by IO::Zlib. It should try to do its thing with whatever it got as an argument. That's debatable. I'd be inclined to do it Storable's way. -sauoq "My two cents aren't worth a dime.";	[reply]


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