1 package org.apache.lucene.analysis.tr;
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20 import java.io.IOException;
22 import org.apache.lucene.analysis.TokenFilter;
23 import org.apache.lucene.analysis.TokenStream;
24 import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
27 * Normalizes Turkish token text to lower case.
29 * Turkish and Azeri have unique casing behavior for some characters. This
30 * filter applies Turkish lowercase rules. For more information, see <a
31 * href="http://en.wikipedia.org/wiki/Turkish_dotted_and_dotless_I"
32 * >http://en.wikipedia.org/wiki/Turkish_dotted_and_dotless_I</a>
35 public final class TurkishLowerCaseFilter extends TokenFilter {
36 private static final int LATIN_CAPITAL_LETTER_I = '\u0049';
37 private static final int LATIN_SMALL_LETTER_I = '\u0069';
38 private static final int LATIN_SMALL_LETTER_DOTLESS_I = '\u0131';
39 private static final int COMBINING_DOT_ABOVE = '\u0307';
40 private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
43 * Create a new TurkishLowerCaseFilter, that normalizes Turkish token text
46 * @param in TokenStream to filter
48 public TurkishLowerCaseFilter(TokenStream in) {
53 public final boolean incrementToken() throws IOException {
54 boolean iOrAfter = false;
56 if (input.incrementToken()) {
57 final char[] buffer = termAtt.buffer();
58 int length = termAtt.length();
59 for (int i = 0; i < length;) {
60 final int ch = Character.codePointAt(buffer, i);
62 iOrAfter = (ch == LATIN_CAPITAL_LETTER_I ||
63 (iOrAfter && Character.getType(ch) == Character.NON_SPACING_MARK));
65 if (iOrAfter) { // all the special I turkish handling happens here.
67 // remove COMBINING_DOT_ABOVE to mimic composed lowercase
68 case COMBINING_DOT_ABOVE:
69 length = delete(buffer, i, length);
71 // i itself, it depends if it is followed by COMBINING_DOT_ABOVE
72 // if it is, we will make it small i and later remove the dot
73 case LATIN_CAPITAL_LETTER_I:
74 if (isBeforeDot(buffer, i + 1, length)) {
75 buffer[i] = LATIN_SMALL_LETTER_I;
77 buffer[i] = LATIN_SMALL_LETTER_DOTLESS_I;
78 // below is an optimization. no COMBINING_DOT_ABOVE follows,
79 // so don't waste time calculating Character.getType(), etc
87 i += Character.toChars(Character.toLowerCase(ch), buffer, i);
90 termAtt.setLength(length);
98 * lookahead for a combining dot above.
99 * other NSMs may be in between.
101 private boolean isBeforeDot(char s[], int pos, int len) {
102 for (int i = pos; i < len;) {
103 final int ch = Character.codePointAt(s, i);
104 if (Character.getType(ch) != Character.NON_SPACING_MARK)
106 if (ch == COMBINING_DOT_ABOVE)
108 i += Character.charCount(ch);
115 * delete a character in-place.
116 * rarely happens, only if COMBINING_DOT_ABOVE is found after an i
118 private int delete(char s[], int pos, int len) {
120 System.arraycopy(s, pos + 1, s, pos, len - pos - 1);