pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / analyzers / common / src / java / org / apache / lucene / analysis / snowball / SnowballFilter.java

diff --git a/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/snowball/SnowballFilter.java b/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/snowball/SnowballFilter.java
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+++ b/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/snowball/SnowballFilter.java
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+package org.apache.lucene.analysis.snowball;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+
+import org.apache.lucene.analysis.TokenFilter;
+import org.apache.lucene.analysis.TokenStream;
+import org.apache.lucene.analysis.tokenattributes.KeywordAttribute;
+import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
+import org.apache.lucene.analysis.tr.TurkishLowerCaseFilter; // javadoc @link
+import org.apache.lucene.analysis.LowerCaseFilter; // javadoc @link
+import org.tartarus.snowball.SnowballProgram;
+
+/**
+ * A filter that stems words using a Snowball-generated stemmer.
+ *
+ * Available stemmers are listed in {@link org.tartarus.snowball.ext}.
+ * <p><b>NOTE</b>: SnowballFilter expects lowercased text.
+ * <ul>
+ *  <li>For the Turkish language, see {@link TurkishLowerCaseFilter}.
+ *  <li>For other languages, see {@link LowerCaseFilter}.
+ * </ul>
+ * </p>
+ */
+public final class SnowballFilter extends TokenFilter {
+
+  private final SnowballProgram stemmer;
+
+  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
+  private final KeywordAttribute keywordAttr = addAttribute(KeywordAttribute.class);
+  
+  public SnowballFilter(TokenStream input, SnowballProgram stemmer) {
+    super(input);
+    this.stemmer = stemmer;
+  }
+
+  /**
+   * Construct the named stemming filter.
+   *
+   * Available stemmers are listed in {@link org.tartarus.snowball.ext}.
+   * The name of a stemmer is the part of the class name before "Stemmer",
+   * e.g., the stemmer in {@link org.tartarus.snowball.ext.EnglishStemmer} is named "English".
+   *
+   * @param in the input tokens to stem
+   * @param name the name of a stemmer
+   */
+  public SnowballFilter(TokenStream in, String name) {
+    super(in);
+    try {      
+      Class<?> stemClass = Class.forName("org.tartarus.snowball.ext." + name + "Stemmer");
+      stemmer = (SnowballProgram) stemClass.newInstance();
+    } catch (Exception e) {
+      throw new RuntimeException(e.toString());
+    }
+  }
+
+  /** Returns the next input Token, after being stemmed */
+  @Override
+  public final boolean incrementToken() throws IOException {
+    if (input.incrementToken()) {
+      if (!keywordAttr.isKeyword()) {
+        char termBuffer[] = termAtt.buffer();
+        final int length = termAtt.length();
+        stemmer.setCurrent(termBuffer, length);
+        stemmer.stem();
+        final char finalTerm[] = stemmer.getCurrentBuffer();
+        final int newLength = stemmer.getCurrentBufferLength();
+        if (finalTerm != termBuffer)
+          termAtt.copyBuffer(finalTerm, 0, newLength);
+        else
+          termAtt.setLength(newLength);
+      }
+      return true;
+    } else {
+      return false;
+    }
+  }
+}