| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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. |
| */ |
| package org.apache.solr.analysis; |
| import java.io.IOException; |
| |
| import org.apache.lucene.analysis.TokenFilter; |
| import org.apache.lucene.analysis.TokenStream; |
| import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute; |
| import org.apache.lucene.analysis.tokenattributes.CharTermAttribute; |
| |
| /** |
| * This class produces a special form of reversed tokens, suitable for |
| * better handling of leading wildcards. Tokens from the input TokenStream |
| * are reversed and prepended with a special "reversed" marker character. |
| * If <code>withOriginal</code> argument is <code>true</code> then first the |
| * original token is returned, and then the reversed token (with |
| * <code>positionIncrement == 0</code>) is returned. Otherwise only reversed |
| * tokens are returned. |
| * <p>Note: this filter doubles the number of tokens in the input stream when |
| * <code>withOriginal == true</code>, which proportionally increases the size |
| * of postings and term dictionary in the index. |
| */ |
| public final class ReversedWildcardFilter extends TokenFilter { |
| |
| private final boolean withOriginal; |
| private final char markerChar; |
| private final CharTermAttribute termAtt; |
| private final PositionIncrementAttribute posAtt; |
| private State save = null; |
| |
| protected ReversedWildcardFilter(TokenStream input, boolean withOriginal, char markerChar) { |
| super(input); |
| this.termAtt = addAttribute(CharTermAttribute.class); |
| this.posAtt = addAttribute(PositionIncrementAttribute.class); |
| this.withOriginal = withOriginal; |
| this.markerChar = markerChar; |
| } |
| |
| @Override |
| public boolean incrementToken() throws IOException { |
| if( save != null ) { |
| // clearAttributes(); // not currently necessary |
| restoreState(save); |
| save = null; |
| return true; |
| } |
| |
| if (!input.incrementToken()) return false; |
| |
| // pass through zero-length terms |
| int oldLen = termAtt.length(); |
| if (oldLen ==0) return true; |
| int origOffset = posAtt.getPositionIncrement(); |
| if (withOriginal == true){ |
| posAtt.setPositionIncrement(0); |
| save = captureState(); |
| } |
| char [] buffer = termAtt.resizeBuffer(oldLen + 1); |
| buffer[oldLen] = markerChar; |
| reverse(buffer, 0, oldLen + 1); |
| |
| posAtt.setPositionIncrement(origOffset); |
| termAtt.copyBuffer(buffer, 0, oldLen +1); |
| return true; |
| } |
| |
| |
| /** |
| * Partially reverses the given input buffer in-place from the given offset |
| * up to the given length, keeping surrogate pairs in the correct (non-reversed) order. |
| * @param buffer the input char array to reverse |
| * @param start the offset from where to reverse the buffer |
| * @param len the length in the buffer up to where the |
| * buffer should be reversed |
| */ |
| public static void reverse(final char[] buffer, final int start, final int len) { |
| /* modified version of Apache Harmony AbstractStringBuilder reverse0() */ |
| if (len < 2) |
| return; |
| int end = (start + len) - 1; |
| char frontHigh = buffer[start]; |
| char endLow = buffer[end]; |
| boolean allowFrontSur = true, allowEndSur = true; |
| final int mid = start + (len >> 1); |
| for (int i = start; i < mid; ++i, --end) { |
| final char frontLow = buffer[i + 1]; |
| final char endHigh = buffer[end - 1]; |
| final boolean surAtFront = allowFrontSur |
| && Character.isSurrogatePair(frontHigh, frontLow); |
| if (surAtFront && (len < 3)) { |
| // nothing to do since surAtFront is allowed and 1 char left |
| return; |
| } |
| final boolean surAtEnd = allowEndSur |
| && Character.isSurrogatePair(endHigh, endLow); |
| allowFrontSur = allowEndSur = true; |
| if (surAtFront == surAtEnd) { |
| if (surAtFront) { |
| // both surrogates |
| buffer[end] = frontLow; |
| buffer[--end] = frontHigh; |
| buffer[i] = endHigh; |
| buffer[++i] = endLow; |
| frontHigh = buffer[i + 1]; |
| endLow = buffer[end - 1]; |
| } else { |
| // neither surrogates |
| buffer[end] = frontHigh; |
| buffer[i] = endLow; |
| frontHigh = frontLow; |
| endLow = endHigh; |
| } |
| } else { |
| if (surAtFront) { |
| // surrogate only at the front |
| buffer[end] = frontLow; |
| buffer[i] = endLow; |
| endLow = endHigh; |
| allowFrontSur = false; |
| } else { |
| // surrogate only at the end |
| buffer[end] = frontHigh; |
| buffer[i] = endHigh; |
| frontHigh = frontLow; |
| allowEndSur = false; |
| } |
| } |
| } |
| if ((len & 0x01) == 1 && !(allowFrontSur && allowEndSur)) { |
| // only if odd length |
| buffer[end] = allowFrontSur ? endLow : frontHigh; |
| } |
| } |
| |
| @Override |
| public void reset() throws IOException { |
| super.reset(); |
| save = null; |
| } |
| |
| } |