terminfosreader.h

clucene是c++版的全文检索引擎,完全移植于lucene,采用 stl 编写.

/*------------------------------------------------------------------------------
* 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_index_TermInfosReader_
#define _lucene_index_TermInfosReader_

#if defined(_LUCENE_PRAGMA_ONCE)
# pragma once
#endif

#include "Terms.h"
#include "SegmentTermEnum.h"
#include "CLucene/store/Directory.h"
#include "FieldInfos.h"
#include "TermInfo.h"
#include "TermInfosWriter.h"

CL_NS_DEF(index)
   /** This stores a monotonically increasing set of <Term, TermInfo> pairs in a
	 * Directory.  Pairs are accessed either by Term or by ordinal position the
	 * set.  
	 *
	 * PORT STATUS: 365707 (jlucene 1.9)
	 */
	class TermInfosReader :LUCENE_BASE{
	private:
		CL_NS(store)::Directory* directory;
		const char* segment;
		FieldInfos* fieldInfos;

#ifdef _CL_DISABLE_MULTITHREADING
		SegmentTermEnum* stEnumerator;
#else
		CL_NS(util)::CLSet<_LUCENE_THREADID_TYPE, SegmentTermEnum*, 
			CL_NS(util)::CLuceneThreadIdCompare, 
			CL_NS(util)::Deletor::ConstNullVal<_LUCENE_THREADID_TYPE>, CL_NS(util)::Deletor::Object<SegmentTermEnum> > enumerators;
		DEFINE_MUTEX(enumerators_LOCK)
#endif
		SegmentTermEnum* getEnum();
		SegmentTermEnum* origEnum;
		SegmentTermEnum* indexEnum;
		int64_t _size;

		Term* indexTerms;
        int32_t indexTermsLength;
		TermInfo* indexInfos;
		int64_t* indexPointers;

		DEFINE_MUTEX(THIS_LOCK)
	public:
		//Constructor.
        //Reads the TermInfos file (.tis) and eventually the Term Info Index file (.tii)
		TermInfosReader(CL_NS(store)::Directory* dir, const char* segment, FieldInfos* fis);
		//Destructor
		~TermInfosReader();
		//Close the enumeration of TermInfos
		void close();
		
		//Return the size of the enumeration of TermInfos
		int64_t size() const;

		int32_t getSkipInterval() { return origEnum->skipInterval; }
		
		// Returns an enumeration of terms starting at or after the named term. 
		// If no term is specified, an enumeration of all the Terms 
		// and TermInfos in the set is returned.
		SegmentTermEnum* terms(const Term* term=NULL);
		
		// Returns the TermInfo for a Term in the set
		// synchronized
		TermInfo* get(const Term* term);
	private:
		//Reads the term info index file or .tti file.
		void ensureIndexIsRead();

		// Returns the offset of the greatest index entry which is less than term.
		int32_t getIndexOffset(const Term* term);

		//Reposition the current Term and TermInfo to indexOffset
		void seekEnum(const int32_t indexOffset);  

		//Scans the Enumeration of terms for term and returns the corresponding TermInfo instance if found.
        //The search is started from the current term.
		TermInfo* scanEnum(const Term* term);

        //Scans the enumeration to the requested position and returns the
        //Term located at that position
		Term* scanEnum(const int32_t position);
		
		// Returns the position of a Term in the set
		// synchronized 
		int64_t getPosition(const Term* term);

		// Returns the nth term in the set. 
		// synchronized
		Term* get(const int32_t position);

	};
CL_NS_END
#endif