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CachingWrapperFilter.h

/*------------------------------------------------------------------------------
* Copyright (C) 2003-2006 Ben van Klinken and the CLucene Team
* 
* Distributable under the terms of either the Apache License (Version 2.0) or 
* the GNU Lesser General Public License, as specified in the COPYING file.
------------------------------------------------------------------------------*/
#ifndef _lucene_search_CachingWrapperFilter_
#define _lucene_search_CachingWrapperFilter_

#include "CLucene/util/BitSet.h"
#include "CLucene/index/IndexReader.h"
#include "Filter.h"

CL_NS_DEF(search)
/**
 * Wraps another filter's result and caches it.  The purpose is to allow
 * filters to implement this and allow itself to be cached. Alternatively,
 * use the CachingWrapperFilter to cache the filter.
 */
00020 class AbstractCachingFilter: public Filter 
{
      class BitSetHolder: LUCENE_BASE{
            bool deleteBs;
      public:
            BitSetHolder(CL_NS(util)::BitSet* bits, bool deleteBs);
            ~BitSetHolder();
            CL_NS(util)::BitSet* bits;
      };
      void closeCallback(CL_NS(index)::IndexReader* reader, void* param);
      typedef CL_NS(util)::CLHashMap<CL_NS(index)::IndexReader*, 
        BitSetHolder*, 
        CL_NS(util)::Compare::Void<CL_NS(index)::IndexReader>,
        CL_NS(util)::Equals::Void<CL_NS(index)::IndexReader>,
        CL_NS(util)::Deletor::Object<CL_NS(index)::IndexReader>, 
        CL_NS(util)::Deletor::Object<BitSetHolder> > CacheType; 

      CacheType cache;

protected:
      AbstractCachingFilter( const AbstractCachingFilter& copy );
      virtual CL_NS(util)::BitSet* doBits( CL_NS(index)::IndexReader* reader ) = 0;
      virtual bool doShouldDeleteBitSet( CL_NS(util)::BitSet* bits ){ return false; }
      AbstractCachingFilter();
public:
      virtual ~AbstractCachingFilter();

      /** Returns a BitSet with true for documents which should be permitted in
      search results, and false for those that should not. */
      CL_NS(util)::BitSet* bits( CL_NS(index)::IndexReader* reader );
      
      virtual Filter *clone() const = 0;
      virtual TCHAR *toString() = 0;
      
      bool shouldDeleteBitSet( const CL_NS(util)::BitSet* bits ) const{ return false; }
};

/**
 * Wraps another filter's result and caches it.  The purpose is to allow
 * filters to simply filter, and then wrap with this class to add
 * caching, keeping the two concerns decoupled yet composable.
 */
00062 class CachingWrapperFilter: public AbstractCachingFilter 
{
private:
      Filter* filter;
      bool deleteFilter;
protected:
      CachingWrapperFilter( const CachingWrapperFilter& copy );
      CL_NS(util)::BitSet* doBits( CL_NS(index)::IndexReader* reader );
      bool doShouldDeleteBitSet( CL_NS(util)::BitSet* bits );
public:
      CachingWrapperFilter( Filter* filter, bool deleteFilter=true );
      ~CachingWrapperFilter();

      Filter *clone() const;
      TCHAR *toString();
};

CL_NS_END
#endif

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