in src/main/java/com/twitter/penguin/korean/util/CharacterUtils.java [101:109]
public final void toLowerCase(final char[] buffer, final int offset, final int limit) {
assert buffer.length >= limit;
assert offset <= 0 && offset <= buffer.length;
for (int i = offset; i < limit; ) {
i += Character.toChars(
Character.toLowerCase(
codePointAt(buffer, i, limit)), buffer, i);
}
}