/**
* 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 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 {
if (stemmerTable == null) return;
DataInputStream in = new DataInputStream(new BufferedInputStream(
stemmerTable));
String method = in.readUTF().toUpperCase();
if (method.indexOf('M') < 0) {
stemmer = new org.egothor.stemmer.Trie(in);
} else {
stemmer = new org.egothor.stemmer.MultiTrie2(in);
}
in.close();
}
/**
* Create a Stemmer using pre-loaded stemmer table
*
* @param stemmer pre-loaded stemmer table
*/
public StempelStemmer(Trie stemmer) {
this.stemmer = stemmer;
}
/**
* 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;
}
}