NAME
    Tie::Hash::LRU - LRU hashes for Perl (XS implementation)

SYNOPSIS
        use Tie::Hash::LRU;

        $tied = tie %h, 'Tie::Hash::LRU', 100; # will hold only 100 entries

        $h{'bar'} = 'foo';
        $h{'foo'} = 'bar'; 
    
        print "foo = $h{'foo'}\n"; # puts 'foo' in front of the queue

        ...
    
        # simple LRU cache

        $foo = $h{'foo'};
        if (!defined $foo) {
            # fetch foo from somewhere 
            $foo = get('foo');
            $h{'foo'} = $foo;
        }

        # Iterating over entries without any impact on LRU queue

        (tied %h)->autohit(0); # disables LRU

        foreach (keys %h) {
            $h{$_} = ...
        }

        while (my ($k, $v) = each %h) { # this one actually won't even work
                                        # with autohit
            ...
        }

        (tied %h)->autohit(1); # enables LRU back on

        # Accessing LRU hash without tied overhead (significantly faster)

        $tied->STORE('foo', 'bar');
        $foo = $tied->FETCH('foo');

        # And the fastest way would be to also avoid looking into @ISA 
        # as with previous example: 

        Tie::Hash::LRU::STORE($tied, 'foo', 'bar');
        $foo = Tie::Hash::LRU::FETCH($tied, 'foo');

DESCRIPTION
    This module provides XS implementation of the LRU algorithm. It merely
    puts hash entry in front of the queue each time this entry accessed.

    Tied hashes have significant overhead and cannot perform as fast as a
    simple subroutine call. So you might want to lower your expectations.
    But the benefits of linked lists are still there, i.e. writes are almost
    as fast as reads, which is not the case for pure-perl implementations.

    Additionally, you can use this module without any tied overhead.

METHODS
    $tied = tie %h, 'Tie::Hash::LRU', 100;
            Create tied LRU hash that will hold 100 entries.

    $tied->autohit(1), (tied %h)->autohit(1)
            Enables/disables LRU for tied hash. LRU is enabled by default.

    $tied->STORE('foo', 'bar')
            Store key into tied object directly.

    $foo = $tied->FETCH('foo')
            Fetch entry from tied object directly.

AUTHOR
    Alexandr Gomoliako <zzz@zzz.org.ua>

LICENSE
    This module is based on Marcus Holland-Moritz's Tie::Hash::Indexed.
    Copyright 2003 Marcus Holland-Moritz.

    Copyright 2011 Alexandr Gomoliako. All rights reserved.

    This module is free software. It may be used, redistributed and/or
    modified under the same terms as Perl itself.