Indexing Revisited

• Where did the offset information come from?

        sub make_index {
          my ($fh, $dbm, $key_function) = @_;
          seek $fh, 0, SEEK_SET;
          %$dbm = (); 
          my $pos = 0;
          while (<$fh>) {
            chomp;
            my $key = $key_function->($_);
            $dbm->{$key} = $pos;
            $pos = tell $fh;
          }
        }

• $fh and $dbm are as before

• $key_function takes a record from the file and says what the key should be

• If the DBM eats the index, your homework is still intact

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Copyright © 2003 M. J. Dominus