pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/tr/TurkishLowerCaseFilter.java b/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/tr/TurkishLowerCaseFilter.java
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+++ b/lucene-java-3.5.0/lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/tr/TurkishLowerCaseFilter.java
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+package org.apache.lucene.analysis.tr;
+
+/**
+ * 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.CharTermAttribute;
+
+/**
+ * Normalizes Turkish token text to lower case.
+ * <p>
+ * Turkish and Azeri have unique casing behavior for some characters. This
+ * filter applies Turkish lowercase rules. For more information, see <a
+ * href="http://en.wikipedia.org/wiki/Turkish_dotted_and_dotless_I"
+ * >http://en.wikipedia.org/wiki/Turkish_dotted_and_dotless_I</a>
+ * </p>
+ */
+public final class TurkishLowerCaseFilter extends TokenFilter {
+  private static final int LATIN_CAPITAL_LETTER_I = '\u0049';
+  private static final int LATIN_SMALL_LETTER_I = '\u0069';
+  private static final int LATIN_SMALL_LETTER_DOTLESS_I = '\u0131';
+  private static final int COMBINING_DOT_ABOVE = '\u0307';
+  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
+  
+  /**
+   * Create a new TurkishLowerCaseFilter, that normalizes Turkish token text 
+   * to lower case.
+   * 
+   * @param in TokenStream to filter
+   */
+  public TurkishLowerCaseFilter(TokenStream in) {
+    super(in);
+  }
+  
+  @Override
+  public final boolean incrementToken() throws IOException {
+    boolean iOrAfter = false;
+    
+    if (input.incrementToken()) {
+      final char[] buffer = termAtt.buffer();
+      int length = termAtt.length();
+      for (int i = 0; i < length;) {
+        final int ch = Character.codePointAt(buffer, i);
+    
+        iOrAfter = (ch == LATIN_CAPITAL_LETTER_I || 
+            (iOrAfter && Character.getType(ch) == Character.NON_SPACING_MARK));
+        
+        if (iOrAfter) { // all the special I turkish handling happens here.
+          switch(ch) {
+            // remove COMBINING_DOT_ABOVE to mimic composed lowercase
+            case COMBINING_DOT_ABOVE:
+              length = delete(buffer, i, length);
+              continue;
+            // i itself, it depends if it is followed by COMBINING_DOT_ABOVE
+            // if it is, we will make it small i and later remove the dot
+            case LATIN_CAPITAL_LETTER_I:
+              if (isBeforeDot(buffer, i + 1, length)) {
+                buffer[i] = LATIN_SMALL_LETTER_I;
+              } else {
+                buffer[i] = LATIN_SMALL_LETTER_DOTLESS_I;
+                // below is an optimization. no COMBINING_DOT_ABOVE follows,
+                // so don't waste time calculating Character.getType(), etc
+                iOrAfter = false;
+              }
+              i++;
+              continue;
+          }
+        }
+        
+        i += Character.toChars(Character.toLowerCase(ch), buffer, i);
+      }
+      
+      termAtt.setLength(length);
+      return true;
+    } else
+      return false;
+  }
+  
+  
+  /**
+   * lookahead for a combining dot above.
+   * other NSMs may be in between.
+   */
+  private boolean isBeforeDot(char s[], int pos, int len) {
+    for (int i = pos; i < len;) {
+      final int ch = Character.codePointAt(s, i);
+      if (Character.getType(ch) != Character.NON_SPACING_MARK)
+        return false;
+      if (ch == COMBINING_DOT_ABOVE)
+        return true;
+      i += Character.charCount(ch);
+    }
+    
+    return false;
+  }
+  
+  /**
+   * delete a character in-place.
+   * rarely happens, only if COMBINING_DOT_ABOVE is found after an i
+   */
+  private int delete(char s[], int pos, int len) {
+    if (pos < len) 
+      System.arraycopy(s, pos + 1, s, pos, len - pos - 1);
+    
+    return len - 1;
+  }
+}