in reply to Tie-ing hashes clobbers data

Your problem is in the last line of the _read() method: 
return \%data;
this returns a reference to the GLOBAL %FileHash::data that is set by the do $file, so you are using the same hash for all FileHash objects.

The quickest way to solve this is to change the offending line with: 

return {%data};
which returns a reference to a COPY of %data, leaving %FileHash::data free to be clobbered by a new do $file

anyway, this will still leave your race conditions intact :-)

Joost.

Replies are listed 'Best First'.
Re: Referencing globals clobbers data
by demerphq (Chancellor) on Apr 08, 2002 at 15:23 UTC
    The quickest way to solve this is to change the offending line with: 
    return {%data};

    [download]
     Hmm, so now he makes a copy of a copy of a copy.... I dont think this is the best call. Do away with the glob semantics and this all becomes very straightforward...

    Yves / DeMerphq
    ---
    Writing a good benchmark isnt as easy as it might look.

[reply]
[d/l]
      That's why it's called the quick fix :-)

      How about... 

      package FileHash;
use strict;
use warnings;
use Tie::Hash;
use Data::Dumper;
our @ISA = ("Tie::Hash");

sub TIEHASH {
   my ($class, $file) = @_;
   my $s = bless {
        FILE => $file,
        DATA => {},
    },$class;
   $s->_read();
   return $s;
}


sub STORE    { $_[0]->{DATA}->{$_[1]} = $_[2] }
sub CLEAR    { $_[0]->{DATA} = () }
sub FETCH    { $_[0]->{DATA}->{$_[1]} }
sub FIRSTKEY { my $a = scalar keys %{$_[0]}; each %{$_[0]->{DATA}} }
sub NEXTKEY  { each %{$_[0]->{DATA}} }
sub EXISTS   { exists $_[0]->{DATA}->{$_[1]} }
sub DELETE   { delete $_[0]->{DATA}->{$_[1]} }
sub DESTROY  { $_[0]->_write }

# ----- private subs -----
sub _write { # still need to deal with race conditions
   my $file =   $_[0]->{FILE} ;
   open (FH, "> $file") or die "Can't open $file for FileHash _write: 
+$!";
   print FH Dumper($_[0]->{DATA});  # writes out as $VAR1 = { ..... }
   close FH or die "Can't close $file for FileHash _write: $!";
}

sub _read { # still need to deal with race conditions
   my $self = shift;
   return unless -f $self->{FILE};
   $self->{DATA} = do $self->{FILE};

}


1;

      [download]
[reply]
[d/l]
        Yup. Thats much better....

        ;-)

        Yves / DeMerphq
        ---
        Writing a good benchmark isnt as easy as it might look.

[reply]

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