Tie::File Internals

• Inside, Tie::File uses a combination of several of the techniques we've seen

• It maintains an offset table internally

        $z = $FILE[57];

• This checks the offsets table for $offsets[57]

  • If it's already present, Tie::File seeks to the right location and reads the record

  • If not, Tie::File scans from the last known position up to line 57

     sub _fetch {
       my ($self, $n) = @_;
       ...

       if ($#{$self->{offsets}} < $n) {
         return if $self->{eof};
         my $o = $self->_fill_offsets_to($n);
         # If it's still undefined, there is no such record,
         # so return 'undef'
         return unless defined $o;
       }

       my $fh = $self->{FH};
       # we can do this now that offsets is populated
       $self->_seek($n);
       my $rec = $self->_read_record;
       ...

       $rec;
     }

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Copyright © 2003 M. J. Dominus