term.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_Term_
#define _lucene_index_Term_

#if defined(_LUCENE_PRAGMA_ONCE)
# pragma once
#endif

#include "CLucene/util/Misc.h"
#include "CLucene/util/StringIntern.h"

CL_NS_DEF(index)

/**
	A Term represents a word from text.  This is the unit of search.  It is
    composed of two elements, the text of the word, as a string, and the name of
    the field that the text occured in, an interned string.

	Note that terms may represent more than words from text fields, but also
    things like dates, email addresses, urls, etc.  

	IMPORTANT NOTE:
    Term inherits from the template class IGCollectable<Term> which tries to do
	some garbage collection by counting the references an instance has. As a result
	of this construction you MUST USE THE finalize() method of the parent class IGCollectable<Term>
	when you want to delete an instance of Term!	


    ABOUT intrn 

	intrn indicates if field and text are interned or not. Interning of Strings is the process of
	converting duplicated strings to shared ones. 

*/
    class Term:LUCENE_REFBASE {
	  private:
	    size_t cachedHashCode;
		const TCHAR* _field;
		//CLStringIntern::iterator fielditr;
#ifdef LUCENE_TERM_TEXT_LENGTH
		TCHAR _text[LUCENE_TERM_TEXT_LENGTH+1];
#else
		TCHAR* _text;
		size_t textLenBuf; //a cache of text len, this allows for a preliminary comparison of text lengths
		//bool    dupT;    //Indicates if Term Text is duplicated (and therefore must be deleted). 
#endif
		size_t textLen; //a cache of text len, this allows for a preliminary comparison of text lengths
		bool    internF; //Indicates if Term Field is interned(and therefore must be uninternd). 
		
	  public:
		
		//todo: these need to be private, but a few other things need to be changed first...
		Term(const TCHAR* fld, const TCHAR* txt, bool internField);
		void set(const TCHAR* fld, const TCHAR* txt, const bool internField);
			
		///Constructs a blank term
		Term();

		/**
		* Constructor. Constructs a Term with the given field and text. Field and text are not copied
		* Field and text are deleted in destructor only if intern is false. 
		*/
		Term(const TCHAR* fld, const TCHAR* txt);
		
		///Destructor.
		~Term();

		///Returns the field of this term, an interned string. The field indicates
		///the part of a document which this term came from. 
		const TCHAR* field() const; ///<returns reference

		///Returns the text of this term.  In the case of words, this is simply the
		///text of the word.  In the case of dates and other types, this is an
		///encoding of the object as a string.
		const TCHAR* text() const; ///<returns reference
		
		///Resets the field and text of a Term.
		inline void set(const TCHAR* fld, const TCHAR* txt){
			set(fld,txt,true);
		}
		
		/**
		* Optimized set of Term by reusing same field as this Term
		* - avoids field.intern() overhead
		* @param text The text of the new term (field is implicitly same as this Term instance)
		*/
		void set(Term* term, const TCHAR* txt);

		/** Compares two terms, returning a negative integer if this
		term belongs before the argument, zero if this term is equal to the
		argument, and a positive integer if this term belongs after the argument.
		
		The ordering of terms is first by field, then by text.*/
		int32_t compareTo(const Term* other) const;

		bool equals(const Term* other) const;

		size_t textLength() const { return textLen; }

		///Forms the contents of Field and term in some kind of tuple notation
		///<field:text>
		TCHAR* toString() const;

		size_t hashCode();


		
		class Equals:public CL_NS_STD(binary_function)<const Term*,const Term*,bool>
		{
		public:
			bool operator()( const Term* val1, const Term* val2 ) const{
				return val1->equals(val2);
			}
		};
		
		class Compare:LUCENE_BASE, public CL_NS(util)::Compare::_base //<Term*>
		{
		public:
			bool operator()( Term* t1, Term* t2 ) const{
				return ( t1->compareTo(t2) < 0 );
			}
			size_t operator()( Term* t ) const{
				return t->hashCode();
			}
		};
	};

CL_NS_END
#endif