# phpman > man > Cache::CacheMetaData(3pm)

## NAME
    [Cache::CacheMetaData](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACacheMetaData/markdown) -- data about objects in the cache

## DESCRIPTION
    The CacheMetaData object is used by size aware caches to keep track of the state of the cache
    and efficiently return information such as an objects size or an ordered list of identifiers to
    be removed when a cache size is being limited. End users will not normally use CacheMetaData
    directly.

## SYNOPSIS
     use [Cache::CacheMetaData](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACacheMetaData/markdown);

     my $cache_meta_data = new [Cache::CacheMetaData](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACacheMetaData/markdown)( );

     foreach my $key ( $cache->get_keys( ) )
     {
        my $object = $cache->get_object( $key ) or
          next;

        $cache_meta_data->insert( $object );
      }

     my $current_size = $cache_meta_data->get_cache_size( );

     my @removal_list = $cache_meta_data->build_removal_list( );

## METHODS
### new
        Construct a new [Cache::CacheMetaData](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACacheMetaData/markdown) object

### insert
        Inform the CacheMetaData about the object *$object* in the cache.

### remove
        Inform the CacheMetaData that the object specified by *$key* is no longer in the cache.

### build_removal_list
        Create a list of the keys in the cache, ordered as follows:

        1) objects that expire now

        2) objects expiring at a particular time, with ties broken by the time at which they were
        least recently accessed

        3) objects that never expire, sub ordered by the time at which they were least recently
        accessed

        NOTE: This could be improved further by taking the size into account on accessed_at ties.
        However, this type of tie is unlikely in normal usage.

### build_object_size
        Return the size of an object specified by *$key*.

## PROPERTIES
    get_cache_size
        The total size of the objects in the cache

## SEE ALSO
    [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown), [Cache::CacheSizer](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACacheSizer/markdown), [Cache::SizeAwareCache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ASizeAwareCache/markdown)

## AUTHOR
    Original author: DeWitt Clinton <<dewitt@unto.net>>

    Last author: $Author: dclinton $

    Copyright (C) 2001-2003 DeWitt Clinton