    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017    package org.apache.commons.lang3.text.translate;
    018
    019    import java.io.IOException;
    020    import java.io.Writer;
    021
    022    /**
    023     * Translates escaped Unicode values of the form \\u+\d\d\d\d back to
    024     * Unicode. It supports multiple 'u' characters and will work with or
    025     * without the +.
    026     *
    027     * @since 3.0
    028     * @version $Id: UnicodeUnescaper.java 1199894 2011-11-09 17:53:59Z ggregory $
    029     */
    030    public class UnicodeUnescaper extends CharSequenceTranslator {
    031
    032        /**
    033         * {@inheritDoc}
    034         */
    035        @Override
    036        public int translate(CharSequence input, int index, Writer out) throws IOException {
    037            if (input.charAt(index) == '\\' && index + 1 < input.length() && input.charAt(index + 1) == 'u') {
    038                // consume optional additional 'u' chars
    039                int i = 2;
    040                while (index + i < input.length() && input.charAt(index + i) == 'u') {
    041                    i++;
    042                }
    043
    044                if (index + i < input.length() && input.charAt(index + i) == '+') {
    045                    i++;
    046                }
    047
    048                if (index + i + 4 <= input.length()) {
    049                    // Get 4 hex digits
    050                    CharSequence unicode = input.subSequence(index + i, index + i + 4);
    051
    052                    try {
    053                        int value = Integer.parseInt(unicode.toString(), 16);
    054                        out.write((char) value);
    055                    } catch (NumberFormatException nfe) {
    056                        throw new IllegalArgumentException("Unable to parse unicode value: " + unicode, nfe);
    057                    }
    058                    return i + 4;
    059                } else {
    060                    throw new IllegalArgumentException("Less than 4 hex digits in unicode value: '" + input.subSequence(index, input.length())
    061                            + "' due to end of CharSequence");
    062                }
    063            }
    064            return 0;
    065        }
    066    }