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The source code

package org.apache.lucene.search;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;

/**
 * Subclass of FilteredTermEnum for enumerating all terms that match the
 * specified wildcard filter term.
 * 

* Term enumerations are always ordered by Term.compareTo(). Each term in * the enumeration is greater than all that precede it. * * @version $Id: WildcardTermEnum.java,v 1.8 2004/05/11 17:23:21 otis Exp $ */ public class WildcardTermEnum extends FilteredTermEnum { Term searchTerm; String field = ""; String text = ""; String pre = ""; int preLen = 0; boolean fieldMatch = false; boolean endEnum = false; /** * Creates a new WildcardTermEnum. Passing in a * {@link org.apache.lucene.index.Term Term} that does not contain a * WILDCARD_CHAR will cause an exception to be thrown. */ public WildcardTermEnum(IndexReader reader, Term term) throws IOException { super(); searchTerm = term; field = searchTerm.field(); text = searchTerm.text(); int sidx = text.indexOf(WILDCARD_STRING); int cidx = text.indexOf(WILDCARD_CHAR); int idx = sidx; if (idx == -1) { idx = cidx; } else if (cidx >= 0) { idx = Math.min(idx, cidx); } pre = searchTerm.text().substring(0,idx); preLen = pre.length(); text = text.substring(preLen); setEnum(reader.terms(new Term(searchTerm.field(), pre))); } protected final boolean termCompare(Term term) { if (field == term.field()) { String searchText = term.text(); if (searchText.startsWith(pre)) { return wildcardEquals(text, 0, searchText, preLen); } } endEnum = true; return false; } public final float difference() { return 1.0f; } public final boolean endEnum() { return endEnum; } /******************************************** * String equality with support for wildcards ********************************************/ public static final char WILDCARD_STRING = '*'; public static final char WILDCARD_CHAR = '?'; /** * Determines if a word matches a wildcard pattern. * Work released by Granta Design Ltd after originally being done on * company time. */ public static final boolean wildcardEquals(String pattern, int patternIdx, String string, int stringIdx) { for (int p = patternIdx; ; ++p) { for (int s = stringIdx; ; ++p, ++s) { // End of string yet? boolean sEnd = (s >= string.length()); // End of pattern yet? boolean pEnd = (p >= pattern.length()); // If we're looking at the end of the string... if (sEnd) { // Assume the only thing left on the pattern is/are wildcards boolean justWildcardsLeft = true; // Current wildcard position int wildcardSearchPos = p; // While we haven't found the end of the pattern, // and haven't encountered any non-wildcard characters while (wildcardSearchPos < pattern.length() && justWildcardsLeft) { // Check the character at the current position char wildchar = pattern.charAt(wildcardSearchPos); // If it's not a wildcard character, then there is more // pattern information after this/these wildcards. if (wildchar != WILDCARD_CHAR && wildchar != WILDCARD_STRING) { justWildcardsLeft = false; } else { // Look at the next character wildcardSearchPos++; } } // This was a prefix wildcard search, and we've matched, so // return true. if (justWildcardsLeft) { return true; } } // If we've gone past the end of the string, or the pattern, // return false. if (sEnd || pEnd) { break; } // Match a single character, so continue. if (pattern.charAt(p) == WILDCARD_CHAR) { continue; } // if (pattern.charAt(p) == WILDCARD_STRING) { // Look at the character beyond the '*'. ++p; // Examine the string, starting at the last character. for (int i = string.length(); i >= s; --i) { if (wildcardEquals(pattern, p, string, i)) { return true; } } break; } if (pattern.charAt(p) != string.charAt(s)) { break; } } return false; } } public void close() throws IOException { super.close(); searchTerm = null; field = null; text = null; } }

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