pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / analyzers / stempel / src / java / org / apache / lucene / analysis / stempel / StempelStemmer.java

diff --git a/lucene-java-3.5.0/lucene/contrib/analyzers/stempel/src/java/org/apache/lucene/analysis/stempel/StempelStemmer.java b/lucene-java-3.5.0/lucene/contrib/analyzers/stempel/src/java/org/apache/lucene/analysis/stempel/StempelStemmer.java
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+/**
+ * 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.
+ */
+
+package org.apache.lucene.analysis.stempel;
+
+import java.io.BufferedInputStream;
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Locale;
+
+import org.egothor.stemmer.Diff;
+import org.egothor.stemmer.Trie;
+
+/**
+ * <p>
+ * Stemmer class is a convenient facade for other stemmer-related classes. The
+ * core stemming algorithm and its implementation is taken verbatim from the
+ * Egothor project ( <a href="http://www.egothor.org">www.egothor.org </a>).
+ * </p>
+ * <p>
+ * Even though the stemmer tables supplied in the distribution package are built
+ * for Polish language, there is nothing language-specific here.
+ * </p>
+ */
+public class StempelStemmer {
+  private Trie stemmer = null;
+  private StringBuilder buffer = new StringBuilder();
+
+  /**
+   * Create a Stemmer using selected stemmer table
+   * 
+   * @param stemmerTable stemmer table.
+   */
+  public StempelStemmer(InputStream stemmerTable) throws IOException {
+    this(load(stemmerTable));
+  }
+
+  /**
+   * Create a Stemmer using pre-loaded stemmer table
+   * 
+   * @param stemmer pre-loaded stemmer table
+   */
+  public StempelStemmer(Trie stemmer) {
+    this.stemmer = stemmer;
+  }
+  
+  /**
+   * Load a stemmer table from an inputstream.
+   */
+  public static Trie load(InputStream stemmerTable) throws IOException {
+    DataInputStream in = null;
+    try {
+      in = new DataInputStream(new BufferedInputStream(stemmerTable));
+      String method = in.readUTF().toUpperCase(Locale.ENGLISH);
+      if (method.indexOf('M') < 0) {
+        return new org.egothor.stemmer.Trie(in);
+      } else {
+        return new org.egothor.stemmer.MultiTrie2(in);
+      }
+    } finally {
+      in.close();
+    }
+  }
+
+  /**
+   * Stem a word. 
+   * 
+   * @param word input word to be stemmed.
+   * @return stemmed word, or null if the stem could not be generated.
+   */
+  public StringBuilder stem(CharSequence word) {
+    CharSequence cmd = stemmer.getLastOnPath(word);
+    
+    if (cmd == null)
+        return null;
+    
+    buffer.setLength(0);
+    buffer.append(word);
+
+    Diff.apply(buffer, cmd);
+    
+    if (buffer.length() > 0)
+      return buffer;
+    else
+      return null;
+  }
+}