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 */
017package org.apache.commons.text.translate;
018
019import java.io.IOException;
020import java.io.Writer;
021import java.util.Arrays;
022import java.util.EnumSet;
023
024/**
025 * Translate XML numeric entities of the form &#[xX]?\d+;? to
026 * the specific codepoint.
027 *
028 * Note that the semi-colon is optional.
029 *
030 * @since 1.0
031 */
032public class NumericEntityUnescaper extends CharSequenceTranslator {
033
034    /** NumericEntityUnescaper option enum. */
035    public enum OPTION { semiColonRequired, semiColonOptional, errorIfNoSemiColon }
036
037    /** EnumSet of OPTIONS, given from the constructor. */
038    private final EnumSet<OPTION> options;
039
040    /**
041     * Create a UnicodeUnescaper.
042     *
043     * The constructor takes a list of options, only one type of which is currently
044     * available (whether to allow, error or ignore the semi-colon on the end of a
045     * numeric entity to being missing).
046     *
047     * For example, to support numeric entities without a ';':
048     *    new NumericEntityUnescaper(NumericEntityUnescaper.OPTION.semiColonOptional)
049     * and to throw an IllegalArgumentException when they're missing:
050     *    new NumericEntityUnescaper(NumericEntityUnescaper.OPTION.errorIfNoSemiColon)
051     *
052     * Note that the default behaviour is to ignore them.
053     *
054     * @param options to apply to this unescaper
055     */
056    public NumericEntityUnescaper(final OPTION... options) {
057        if (options.length > 0) {
058            this.options = EnumSet.copyOf(Arrays.asList(options));
059        } else {
060            this.options = EnumSet.copyOf(Arrays.asList(new OPTION[] {OPTION.semiColonRequired}));
061        }
062    }
063
064    /**
065     * Whether the passed in option is currently set.
066     *
067     * @param option to check state of
068     * @return whether the option is set
069     */
070    public boolean isSet(final OPTION option) {
071        return options != null && options.contains(option);
072    }
073
074    /**
075     * {@inheritDoc}
076     */
077    @Override
078    public int translate(final CharSequence input, final int index, final Writer out) throws IOException {
079        final int seqEnd = input.length();
080        // Uses -2 to ensure there is something after the &#
081        if (input.charAt(index) == '&' && index < seqEnd - 2 && input.charAt(index + 1) == '#') {
082            int start = index + 2;
083            boolean isHex = false;
084
085            final char firstChar = input.charAt(start);
086            if (firstChar == 'x' || firstChar == 'X') {
087                start++;
088                isHex = true;
089
090                // Check there's more than just an x after the &#
091                if (start == seqEnd) {
092                    return 0;
093                }
094            }
095
096            int end = start;
097            // Note that this supports character codes without a ; on the end
098            while (end < seqEnd && (input.charAt(end) >= '0' && input.charAt(end) <= '9'
099                                    || input.charAt(end) >= 'a' && input.charAt(end) <= 'f'
100                                    || input.charAt(end) >= 'A' && input.charAt(end) <= 'F')) {
101                end++;
102            }
103
104            final boolean semiNext = end != seqEnd && input.charAt(end) == ';';
105
106            if (!semiNext) {
107                if (isSet(OPTION.semiColonRequired)) {
108                    return 0;
109                }
110                if (isSet(OPTION.errorIfNoSemiColon)) {
111                    throw new IllegalArgumentException("Semi-colon required at end of numeric entity");
112                }
113            }
114
115            int entityValue;
116            try {
117                if (isHex) {
118                    entityValue = Integer.parseInt(input.subSequence(start, end).toString(), 16);
119                } else {
120                    entityValue = Integer.parseInt(input.subSequence(start, end).toString(), 10);
121                }
122            } catch (final NumberFormatException nfe) {
123                return 0;
124            }
125
126            if (entityValue > 0xFFFF) {
127                final char[] chrs = Character.toChars(entityValue);
128                out.write(chrs[0]);
129                out.write(chrs[1]);
130            } else {
131                out.write(entityValue);
132            }
133
134            return 2 + end - start + (isHex ? 1 : 0) + (semiNext ? 1 : 0);
135        }
136        return 0;
137    }
138}