Indexing with Tie::File

• You can use an in-memory hash as an index into a Tie::File file

• Here, %index maps usernames to record numbers:

        my %index;
        my $NEXT_UNREAD = 0;
        sub find_user {
          my ($file, $user) = @_;
          my $rec;

          until (exists $index{$user}) {
            $rec = $file->[$NEXT_UNREAD];
            return unless defined $rec;
            my ($u) = unpack "A8", $rec;
            $index{$u} = $NEXT_UNREAD;
            $NEXT_UNREAD++;
          }
          return unpack "A8 A5 A13 A20 A18", $file->[$index{$user}];
        }

• Each time this is called, it checks the index for the user you asked for

  • If the user is there, it uses Tie::File to retrieve the data quickly

  • If not, it scans the file until it finds what you wanted

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Copyright © 2003 M. J. Dominus