NAME
    CHI::Memoize - Make functions faster with memoization, via CHI

VERSION
    version 0.03

SYNOPSIS
        use CHI::Memoize qw(:all);
    
        # Straight memoization in memory
        memoize('func');
        memoize('Some::Package::func');
    
        # Memoize an anonymous function
        $anon = memoize($anon);
    
        # Memoize based on the second and third argument to func
        memoize('func', key => sub { $_[1], $_[2] });
    
        # Memoize only in certain cases
        memoize('func', key => sub { $_[0] eq 'variable' ? NO_MEMOIZE : @_ });
    
        # Expire after one hour
        memoize('func', expires_in => '1h');
    
        # Store a maximum of 10 results with LRU discard
        memoize('func', max_size => 10);
    
        # Store raw references instead of serializing/deserializing (faster, more risky)
        memoize('func', driver => 'RawMemory');
    
        # Store in memcached instead of memory
        memoize('func', driver => 'Memcached', servers => ["127.0.0.1:11211"]);
    
        # See what's been memoized for a function
        my @keys = memoized('func')->cache->get_keys;
    
        # Clear memoize results for a function
        my @keys = memoized('func')->cache->clear;
    
        # Use an explicit cache instead of autocreating one
        my $cache = CHI->new(driver => 'Memcached', servers => ["127.0.0.1:11211"]);
        memoize('func', cache => $cache);
    
        # Unmemoize function, restoring it to its original state
        unmemoize('func');

DESCRIPTION
    "`Memoizing' a function makes it faster by trading space for time. It
    does this by caching the return values of the function in a table. If
    you call the function again with the same arguments, `memoize' jumps in
    and gives you the value out of the table, instead of letting the
    function compute the value all over again." -- quoted from the original
    Memoize

    `CHI::Memoize' provides the same facility as Memoize, but backed by CHI.
    This means, among other things, that you can

    *   specify expiration times (expires_in) and conditions (expire_if)

    *   memoize to different backends, e.g. File, Memcached, DBI, or to
        multilevel caches

    *   handle arbitrarily complex function arguments (via CHI key
        serialization)

  FUNCTIONS
    All of these are importable; only `memoize' is imported by default. `use
    Memoize qw(:all)' will import them all as well as the `NO_MEMOIZE'
    constant.

    memoize ($func, option => value, ...)
        Creates a new function wrapped around *$func* that caches results
        based on passed arguments.

        *$func* can be a function name (with or without a package prefix) or
        an anonymous function. In the former case, the name is rebound to
        the new function. In either case a code ref to the new wrapper
        function is returned.

        By default, the cache key is formed from combining the full function
        name, the calling context ("L" or "S"), and all the function
        arguments with canonical JSON (sorted hash keys). e.g. these
        arguments will generate the same cache key:

            memoized_function(a => 5, b => 6, c => { d => 7, e => 8 });
            memoized_function(b => 6, c => { e => 8, d => 7 }, a => 5);

        but these will use a different cache key because of context:

             my $scalar = memoized_function(5);
             my @list = memoized_function(5);

        By default, the cache namespace is formed from the full function
        name or the stringified code reference. This allows you to
        introspect and clear the memoized results for a particular function.

        `memoize' throws an error if *$func* is already memoized.

    memoized ($func)
        Returns a CHI::Memoize::Info object if *$func* has been memoized, or
        undef if it has not been memoized.

            # The CHI cache where memoize results are stored
            #
            my $cache = memoized($func)->cache;
            $cache->clear;

            # Code references to the original function and to the new wrapped function
            #
            my $orig = memoized($func)->orig;
            my $wrapped = memoized($func)->wrapped;

    unmemoize ($func)
        Removes the wrapper around *$func*, restoring it to its original
        unmemoized state. Also clears the memoize cache if possible (not
        supported by all drivers, particularly memcached). Throws an error
        if *$func* has not been memoized.

  OPTIONS
    The following options can be passed to memoize.

    key Specifies a code reference that takes arguments passed to the
        function and returns a cache key. The key may be returned as a list,
        list reference or hash reference; it will automatically be
        serialized to JSON in canonical mode (sorted hash keys). e.g. this
        uses the second and third argument to the function as a key:

            memoize('func', key => sub { @_[1..2] });

        Regardless of what key you specify, it will automatically be
        prefixed with the full function name and the calling context ("L" or
        "S").

        If the function returns `CHI::Memoize::NO_MEMOIZE' (or `NO_MEMOIZE'
        if you import it), this call won't be memoized. This is useful if
        you have a cache of limited size or if you know certain arguments
        will yield nondeterministic results.

    set and get options
        You can pass any of CHI's set options (e.g. expires_in,
        expires_variance) or get options (e.g. expire_if, busy_lock). e.g.

            # Expire after one hour
            memoize('func', expires_in => '1h');
    
            # Expire when a particular condition occurs
            memoize('func', expire_if => sub { ... });

    cache options
        Any remaining options will be passed to the CHI constructor to
        generate the cache:

            # Store in memcached instead of memory
            memoize('func', driver => 'Memcached', servers => ["127.0.0.1:11211"]);

        Unless specified, the namespace is generated from the full name of
        the function being memoized.

        You can also specify an existing cache object:

            # Store in memcached instead of memory
            my $cache = CHI->new(driver => 'Memcached', servers => ["127.0.0.1:11211"]);
            memoize('func', cache => $cache);

CLONED VS RAW REFERENCES
    By default `CHI', and thus `CHI::Memoize', returns a deep clone of the
    stored value. e.g. in this code

        # func returns a list reference
        memoize('func');
        my $ref1 = func();
        my $ref2 = func();

    `$ref1' and `$ref2' will be references to two completely different lists
    which have the same contained values. More specifically, the value is
    serialized by Storable on `set' and deserialized (hence cloned) on
    `get'.

    The advantage here is that it is safe to modify a reference returned
    from a memoized function; your modifications won't affect the cached
    value.

        my $ref1 = func();
        push(@$ref1, 3, 4, 5);
        my $ref2 = func();
        # $ref2 does not have 3, 4, 5

    The disadvantage is that it takes extra time to serialize and
    deserialize the value, and that some values like code references may be
    more difficult to store. And cloning may not be what you want at all,
    e.g. if you are returning objects.

    Alternatively you can use CHI::Driver::RawMemory, which will store raw
    references the way `Memoize' does. Now, however, any modifications to
    the contents of a returned reference will affect the cached value.

        memoize('func', driver => 'RawMemory');
        my $ref1 = func();
        push(@$ref1, 3, 4, 5);
        my $ref2 = func();
        # $ref1 eq $ref2
        # $ref2 has 3, 4, 5

CAVEATS
    The caveats of Memoize apply here as well. To summarize:

    *   Do not memoize a function whose behavior depends on program state
        other than its own arguments, unless you explicitly capture that
        state in your computed key.

    *   Do not memoize a function with side effects, as the side effects
        won't happen on a cache hit.

    *   Do not memoize a very simple function, as the costs of caching will
        outweigh the costs of the function itself.

KNOWN BUGS
    *   Memoizing a function will affect its call stack and its prototype.

RELATED MODULES
    A number of modules address a subset of the problems addressed by this
    module, including:

    *   Memoize::Expire - pluggable expiration of memoized values

    *   Memoize::ExpireLRU - provides LRU expiration for Memoize

    *   Memoize::Memcached - use a memcached cache to memoize functions

SUPPORT
    Questions and feedback are welcome, and should be directed to the
    perl-cache mailing list:

        http://groups.google.com/group/perl-cache-discuss

    Bugs and feature requests will be tracked at RT:

        http://rt.cpan.org/NoAuth/Bugs.html?Dist=CHI-Memoize
        bug-chi-memoize@rt.cpan.org

    The latest source code can be browsed and fetched at:

        http://github.com/jonswar/perl-chi-memoize
        git clone git://github.com/jonswar/perl-chi-memoize.git

SEE ALSO
    CHI, Memoize

AUTHOR
    Jonathan Swartz <swartz@pobox.com>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2011 by Jonathan Swartz.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.