/*
* Copyright (C) 2010 The Android Open Source Project
*
* 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 java.lang;
import java.util.Locale;
/**
* Performs case operations as described by http://unicode.org/reports/tr21/tr21-5.html.
*/
class CaseMapper {
// Intention-revealing constants for various important characters.
private static final char LATIN_CAPITAL_I = 'I';
private static final char LATIN_SMALL_I = 'i';
private static final char LATIN_CAPITAL_I_WITH_DOT = '\u0130';
private static final char LATIN_SMALL_DOTLESS_I = '\u0131';
private static final char COMBINING_DOT_ABOVE = '\u0307';
private static final char GREEK_CAPITAL_SIGMA = '\u03a3';
private static final char GREEK_SMALL_FINAL_SIGMA = '\u03c2';
/**
* Our current GC makes short-lived objects more expensive than we'd like. When that's fixed,
* this class should be changed so that you instantiate it with the String and its value,
* offset, and count fields.
*/
private CaseMapper() {
}
/**
* Implements String.toLowerCase. We need 's' so that we can return the original String instance
* if nothing changes. We need 'value', 'offset', and 'count' because they're not otherwise
* accessible.
*/
public static String toLowerCase(Locale locale, String s, char[] value, int offset, int count) {
String languageCode = locale.getLanguage();
boolean turkishOrAzeri = languageCode.equals("tr") || languageCode.equals("az");
char[] newValue = null;
int newCount = 0;
for (int i = offset, end = offset + count; i < end; ++i) {
char ch = value[i];
char newCh = ch;
if (turkishOrAzeri && ch == LATIN_CAPITAL_I_WITH_DOT) {
newCh = LATIN_SMALL_I;
} else if (turkishOrAzeri && ch == LATIN_CAPITAL_I && !followedBy(value, offset, count, i, COMBINING_DOT_ABOVE)) {
newCh = LATIN_SMALL_DOTLESS_I;
} else if (turkishOrAzeri && ch == COMBINING_DOT_ABOVE && precededBy(value, offset, count, i, LATIN_CAPITAL_I)) {
continue; // (We've already converted the preceding I, so we don't need to create newValue.)
} else if (ch == GREEK_CAPITAL_SIGMA && isFinalSigma(value, offset, count, i)) {
newCh = GREEK_SMALL_FINAL_SIGMA;
} else {
newCh = Character.toLowerCase(ch);
}
if (newValue == null && ch != newCh) {
newValue = new char[count]; // The result can't be longer than the input.
newCount = i - offset;
System.arraycopy(value, offset, newValue, 0, newCount);
}
if (newValue != null) {
newValue[newCount++] = newCh;
}
}
return newValue != null ? new String(0, newCount, newValue) : s;
}
private static boolean followedBy(char[] value, int offset, int count, int index, char ch) {
return index + 1 < offset + count && value[index + 1] == ch;
}
private static boolean precededBy(char[] value, int offset, int count, int index, char ch) {
return index > offset && value[index - 1] == ch;
}
/**
* True if 'index' is preceded by a sequence consisting of a cased letter and a case-ignorable
* sequence, and 'index' is not followed by a sequence consisting of an ignorable sequence and
* then a cased letter.
*/
private static boolean isFinalSigma(char[] value, int offset, int count, int index) {
// TODO: we don't skip case-ignorable sequences like we should.
// TODO: we should add a more direct way to test for a cased letter.
if (index <= offset) {
return false;
}
char previous = value[index - 1];
if (!(Character.isLowerCase(previous) || Character.isUpperCase(previous) || Character.isTitleCase(previous))) {
return false;
}
if (index + 1 >= offset + count) {
return true;
}
char next = value[index + 1];
if (Character.isLowerCase(next) || Character.isUpperCase(next) || Character.isTitleCase(next)) {
return false;
}
return true;
}
}