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Tie::FileLRUCache(3)  User Contributed Perl Documentation Tie::FileLRUCache(3)

NAME
       Tie::FileLRUCache - A lightweight but robust filesystem based
       persistent LRU cache

CHANGES
       1.06 2020.10.08	- Changed license to MIT License. Updated maintainer
       info.
			  Updated build	files. Added GitHub repo meta to
       build.
			  Changed minimum supported version of Perl to 5.6.

       1.05 2005.09.13	- Changes to pod tests to make them more CPANTS
       friendly.
			  No functional	changes.

       1.04 2005.09.13	- Removed use of lexical warnings pragma to fix
       compatibility
			  with Perl 5.005.

			  Fixed	minor typographical errors in documentation.

       1.03 2005.09.10 - Changed build test to handle difference in treatment
       of hashes
			 in scalar context between 5.6.x and 5.8.x versions of
       Perl that
			 caused	a test failure under Perl 5.6.x.

       1.02 2005.09.08 - Added build tests. Major code cleanup.	Improved
       platform	portability.
			 Added and documented 'cache_dir', 'keep_last' and
       'number_of_entries'
			 methods. Added	Module::Build support.

       1.01 1999.12.09 - Added detainting in internal cache maintaining
			 functions to evade Taint's tainting
			 of filenames read via readdir().

SYNOPSIS
   OBJECT INTERFACE
	use Tie::FileLRUCache;
	my $cache = Tie::FileLRUCache->new({ -cache_dir	=> $directory, -keep_last => 100 });

	# Inserting value into LRU cache using '-key'
	$cache->update({ -key => $key, -value => $value	});

	# Inserting value into LRU cache using '-cache_key'
	my $cache_key =	$cache->make_cache_key({ -key => $key });
	$cache->update({ -cache_key => $cache_key, -value => $value });

	# Checking LRU cache
	my ($in_cache,$value) =	$cache->check({	-key =>	$key });
	if ($in_cache) {
	    return $value;
	}
	# Not in cache - do something else

	# Checking LRU cache with speed	up hack	for objects, hashes, arrays etc	used as	keys
	my $cache_key =	$cache->make_cache_key({ -key => $something });
	my ($in_cache,$value) =	$cache->check({	-cache_key => $cache_key });
	if ($in_cache) {
	    return $value;
	}
	# Not in cache - do something else

	# Deleting a key and its value from the	cache
	$cache->delete({ -key => $key });

	# Clearing LRU cache
	$cache->clear;

   TIED	INTERFACE
	use Tie::FileLRUCache;

	[$X =] tie %hash,  'Tie::FileLRUCache',	$cache_dir, $keep_last_n;

	# Adding a key/value to	the cache
	$hash{$key} = $value;

	# Checking the cache
	if (not	exists $hash{$key}) {;
	    # No match
	      .
	      .
	      .

	} else {
	    my $value =	$hash{$key};
	      .
	      .
	      .

	}

	# Removing a value from	the cache;
	delete $hash{$key};

	# Clearing the cache
	%hash =	();

       Note: Iteration over the	cache (each, keys, values) is _NOT_ supported.

DESCRIPTION
       Provides	a lightweight persistent filesystem based LRU cache.

       It uses the 'last accessed' timestamp generated by the file system to
       determine the 'oldest' cache entry and discards the oldest cache
       entries when needed to stay under the -keep_last	limit.

       If you store thing very fast (such that many entries receive the	same
       time stamp), it is essentially a	coin toss which	entry within a single
       timestamped second gets purged from the cache to	make room for new
       ones.

       It is not designed to handle huge numbers of cached items. It is
       probably	unwise to set the 'keep_last' higher than around 100.

OBJECT METHODS
       new({[ -cache_dir => $cache_directory] [, -keep_last => $keep_last_n ]
       });
	   Creates and optionally initializes a	Tie::FileLRUCache object:

	   Example:

	     my	$cache = Tie::FileLRUCache->new({
				  -cache_dir =>	'/tmp/testing',
				  -keep_last =>	100,
				});

	   The default cache size is 100 entries unless	specified.

       check({ -key => $key });
	   Reads the cache for the key.

	   Returns two values: $cache_hit (true	if a hit was found, false if
	   not)
			       $value	  (the cached value, undef if no hit)

	   Examples:

	      my ($cache_hit,$value) = $cache->check({ -key => $key });

	      my ($cache_hit,$value) = $cache->check({ -cache_key => $cache_key	});

	   The '-key' form is used when	you just want to use a raw key.	It can
	   use blessed objects,	hash refs, scalars, or array refs as keys. The
	   more	complex	structures take	a speed	penalty	for computing a
	   canonical form.  You	can minimize this penalty by using the
	   '-cache_key'	form instead.

	   The '-cache_key' form is used for performance reasons when using
	   keys	such as	complex	blessed	objects	or hashes as a key. The
	   -cache_key is obtained with a call to 'make_cache_key'. It is legal
	   to mix -cache_key and -key based calls - they are cross-compatible.

       make_cache_key({	-key =>	$key });
	   Generates a cache key by canonicalizing a passed key	as a network
	   ordered canonical Storable string.

	   Example:

	    my $cache_key = $cache->make_cache_key({ -key => $key });

       clear;
	   Completely clears the cache of all cache entries.

       update({	[-key => $key,]	[-cache_key => $cache_key, ], -value =>	$value
       [, -keep_last =>	$keep_last_n ] });
	   Updates the Least Recently Used (LRU) cache for the specified key
	   with	the passed value.  '-keep_last'	is optional after the first
	   access to a dataset.	It will	use the	most recent 'keep_last'	used
	   if not specified.

	   It is legal to use ordinary scalars,	hash references, or array
	   references as keys as well as objects as -keys or -values.
	   Basically, anything that Storable can reproducibly serialize	can be
	   used.

	   Examples:

	    $cache->update({ -key => $key, -value => $value });

	    $cache->update({ -key => $key, -value => $value, -keep_last	=> 100});

	    my $cache_key = $cache->make_cache_key({ -key => $key });
	    $cache->update({ -cache_key	=> $cache_key, -value => $value	});

	    my $cache_key = $cache->make_cache_key({ -key => $key });
	    $cache->update({ -cache_key	=> $cache_key, -value => $value, -keep_last => 50 });

	    -cache_key is assumed to be	a simple scalar	value for use as a key.

	    -key can be	pretty much anything Storable can successfully and reproducibly	serialize.

	   One or the other must be passed.

       delete({	-key =>	$key });
	   Forces the deletion of a specific key from the cache.

	   Example:

	    $cache->delete({ -key => $key });

       cache_dir([$cache_directory_path]);
	   Get/Set accessor for	the cache directory path.

	   Ex.

	     my	$cache_directory = $cache->cache_dir;

	     $cache->cache_dir($cache_directory);

       keep_last([$keep_last_n]);
	   Get/Set accessor for	the keep last N	setting.

	   Ex.

	     my	$n_last	= $cache->keep_last;

	     $cache->keep_last(20);

       number_of_entries;
	   Returns the current number of entries in the	cache.

COPYRIGHT
       Copyright 1999, 2020 Jerilyn Franz and FreeRun Technologies, Inc. All
       Rights Reserved.

VERSION
	1.06 released 2020.10.08

LICENSE
       MIT License

       Copyright (c) 2020 Jerilyn Franz

       Permission is hereby granted, free of charge, to	any person obtaining a
       copy of this software and associated documentation files	(the
       "Software"), to deal in the Software without restriction, including
       without limitation the rights to	use, copy, modify, merge, publish,
       distribute, sublicense, and/or sell copies of the Software, and to
       permit persons to whom the Software is furnished	to do so, subject to
       the following conditions:

       The above copyright notice and this permission notice shall be included
       in all copies or	substantial portions of	the Software.

       THE SOFTWARE IS PROVIDED	"AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
       OR IMPLIED, INCLUDING BUT NOT LIMITED TO	THE WARRANTIES OF
       MERCHANTABILITY,	FITNESS	FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
       IN NO EVENT SHALL THE AUTHORS OR	COPYRIGHT HOLDERS BE LIABLE FOR	ANY
       CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN	ACTION OF CONTRACT,
       TORT OR OTHERWISE, ARISING FROM,	OUT OF OR IN CONNECTION	WITH THE
       SOFTWARE	OR THE USE OR OTHER DEALINGS IN	THE SOFTWARE.

DISCLAIMER
       THIS SOFTWARE IS	PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
       WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
       MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

       Use of this software in any way or in any form, source or binary, is
       not allowed in any country which	prohibits disclaimers of any implied
       warranties of merchantability or	fitness	for a particular purpose or
       any disclaimers of a similar nature.

       IN NO EVENT SHALL I BE LIABLE TO	ANY PARTY FOR DIRECT, INDIRECT,
       SPECIAL,	INCIDENTAL,  OR	CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE
       OF THIS SOFTWARE	AND ITS	DOCUMENTATION (INCLUDING, BUT NOT LIMITED TO,
       LOST PROFITS) EVEN IF I HAVE BEEN ADVISED OF THE	POSSIBILITY OF SUCH
       DAMAGE

AUTHOR
       Jerilyn Franz

TODO
       Nothing.

perl v5.32.1			  2020-10-08		  Tie::FileLRUCache(3)

NAME | CHANGES | SYNOPSIS | DESCRIPTION | OBJECT METHODS | COPYRIGHT | VERSION | LICENSE | DISCLAIMER | AUTHOR | TODO

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