@Override
            public void addCharacters(char[] buf, int start, int len) {
                if (codepoint == -1) {
                    return;
                } else {
                    for (int i = start; i < start + len; i++) {
                        addCharacter(buf[i]);
                    }
                }
            }
@see nu.validator.datatype.AbstractDatatype#createStreamingValidator(org.relaxng.datatype.ValidationContext)
src/nu/validator/datatype/AbstractUnicodeClassCharacter.java