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135 lines
2.4 KiB
135 lines
2.4 KiB
//
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// QueryParser.cc
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//
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// QueryParser: (abstract) root of the family of classes that create
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// Query trees by analyzing query strings.
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// The main public interface consists on Parse(),
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// which does the job.
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// The subclasses must provide a lexer.
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// This class implements also the common behaviour needed to
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// parse single words and phrases.
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//
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// Part of the ht://Dig package <http://www.htdig.org/>
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// Copyright (c) 1995-2004 The ht://Dig Group
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// For copyright details, see the file COPYING in your distribution
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// or the GNU Library General Public License (LGPL) version 2 or later
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// <http://www.gnu.org/copyleft/lgpl.html>
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//
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// $Id: QueryParser.cc,v 1.4 2004/05/28 13:15:24 lha Exp $
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//
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#include "QueryParser.h"
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#include "Query.h"
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#include "htString.h"
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#include "ExactWordQuery.h"
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#include "PhraseQuery.h"
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#include "FuzzyExpander.h"
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extern int debug;
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FuzzyExpander *
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QueryParser::expander = 0;
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//
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// parse a query string
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//
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//
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Query *
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QueryParser::Parse(const String &query_string)
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{
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error = "";
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Token().Set(query_string);
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Query *result = ParseExpression();
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if(result && !Token().IsEnd())
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{
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Expected("end of query");
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// delete result;
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result = 0;
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}
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return result;
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}
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// parse one word
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// return a fuzzy word query
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//
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Query *
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QueryParser::ParseWord()
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{
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Query *result = 0;
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if(expander)
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{
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result = expander->MakeQuery(Token().Value());
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}
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else
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{
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result = new ExactWordQuery(Token().Value());
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}
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Token().Next();
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return result;
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}
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//
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// parse one word
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// return an exact query
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//
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Query *
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QueryParser::ParseExactWord()
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{
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Query *result = new ExactWordQuery(Token().Value());
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Token().Next();
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return result;
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}
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//
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// phrase == word { word }
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//
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Query *
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QueryParser::ParsePhrase()
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{
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Query *result = 0;
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Query *word = 0;
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if(!Token().IsEnd() && !Token().IsQuote())
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{
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word = ParseExactWord();
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}
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if(word)
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{
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result = new PhraseQuery;
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result->Add(word);
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while(word && !Token().IsEnd() && !Token().IsQuote())
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{
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word = ParseExactWord();
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if(word)
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{
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result->Add(word);
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}
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}
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}
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if(!word && result)
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{
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delete result;
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result = 0;
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}
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if(!result)
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{
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Expected("at least one word after \"");
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}
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return result;
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}
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void
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QueryParser::Expected(const String &what)
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{
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error << "Expected " << what;
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if(Token().IsEnd())
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{
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error << " at the end";
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}
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else
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{
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error << " instead of '" << Token().Value() << "'";
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}
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}
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