/ 
Tie-PerfectHash-0.01
/ Tie::PerfectHash

NAME

Tie::PerfectHash - Minimal Perfect Hash

SYNOPSIS

  use Tie::PerfectHash;

  == OO Interface ==

    @k = qw/heaven earth wind lake thunder mountain fire water/;

    $ph = Tie::PerfectHash->new({ KEYSET => \@k,
			    MAX_KEYLEN => 16,
			    MAPSIZE => 23});
    $ph->store('heaven', 'sign');
    $ph->fetch('earth');


  == Tie Interface ==

    tie %PH, 'Tie::PerfectHash',{ KEYSET => \@k,
      			    MAX_KEYLEN => 16,
			    MAPSIZE => 23
			  };
    $PH{heaven} = 'sign';
    print $PH{earth};

DESCRIPTION

    * Tie::PerfectHash implements "Minimal Perfect Hashing Algorithm".

    * It improves hash performance under some conditions.
      E.g. Accessing a full-text search dictionary

    * OO and tie interface are available

    * Options for initialization

        KEYSET         := Reference to an array of keys

        MAX_KEYLEN     := Maximal length of keys. Default is 128

        MAPSIZE        := Mapping table size for creating minimal
                          perfect hash
                          Default is 1.9 times the size of KEYSET

        MAX_CHARWEIGHT := Maximal weight of a character in a key.
                          It is for generating random hash function.
                          Default is 64.

    * Usage and Public Methods

      == OO Interface ==

       @k = qw/heaven earth wind lake thunder mountain fire water/;

       # Tie::PerfectHash allocates space for the keyset,
       # and make it perfect.

       $ph = Tie::PerfectHash->new({	   KEYSET         => \@k, 
					   MAX_KEYLEN     => 16,
					   MAX_CHARWEIGHT => 64,
					   MAPSIZE        => 23,
				       });

       $ph->store('heaven', 'sign');  # assign value to a key

       print $ph->fetch('earth');     # get a key's value

       print $ph->getkeys();          # returns an array of keyset, 
                                      # without duplications

       print $ph->getidx('wind');     # get a key's internal serial


      == Tie Interface ==

       tie %PH, 'Tie::PerfectHash',{
	         KEYSET         => \@k, 
		 MAX_KEYLEN     => 16,
 		 MAX_CHARWEIGHT => 64,
		 MAPSIZE        => 23,
		 };

        # then you can treat it like an ordinary hash,
          except its limited vocabulary

        $PH{heaven} = 'sign';

        print $PH{earth};

	print "$_ => $PH{$_}\n" for keys %PH;

        %PH = ();

        untie %PH;

AUTHOR

xern <xern@cpan.org>

REFERENCE

Ian H. Witten, Alistair Moffat, Timothy C. Bell.
 Managing Gigabytes 2nd. ed. : Morgan Kaufman

COPYRIGHT

Copyright 2002 by xern <xern@cpan.org>

This program is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.