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.lang3.text.translate;
018
019import java.io.IOException;
020import java.io.Writer;
021
022/**
023 * Translates codepoints to their Unicode escaped value.
024 *
025 * @since 3.0
026 * @version $Id: UnicodeEscaper.java 1666535 2015-03-13 18:18:59Z britter $
027 */
028public class UnicodeEscaper extends CodePointTranslator {
029
030    private final int below;
031    private final int above;
032    private final boolean between;
033
034    /**
035     * <p>Constructs a <code>UnicodeEscaper</code> for all characters. </p>
036     */
037    public UnicodeEscaper(){
038        this(0, Integer.MAX_VALUE, true);
039    }
040
041    /**
042     * <p>Constructs a <code>UnicodeEscaper</code> for the specified range. This is
043     * the underlying method for the other constructors/builders. The <code>below</code>
044     * and <code>above</code> boundaries are inclusive when <code>between</code> is
045     * <code>true</code> and exclusive when it is <code>false</code>. </p>
046     *
047     * @param below int value representing the lowest codepoint boundary
048     * @param above int value representing the highest codepoint boundary
049     * @param between whether to escape between the boundaries or outside them
050     */
051    protected UnicodeEscaper(final int below, final int above, final boolean between) {
052        this.below = below;
053        this.above = above;
054        this.between = between;
055    }
056
057    /**
058     * <p>Constructs a <code>UnicodeEscaper</code> below the specified value (exclusive). </p>
059     *
060     * @param codepoint below which to escape
061     * @return the newly created {@code UnicodeEscaper} instance
062     */
063    public static UnicodeEscaper below(final int codepoint) {
064        return outsideOf(codepoint, Integer.MAX_VALUE);
065    }
066
067    /**
068     * <p>Constructs a <code>UnicodeEscaper</code> above the specified value (exclusive). </p>
069     *
070     * @param codepoint above which to escape
071     * @return the newly created {@code UnicodeEscaper} instance
072     */
073    public static UnicodeEscaper above(final int codepoint) {
074        return outsideOf(0, codepoint);
075    }
076
077    /**
078     * <p>Constructs a <code>UnicodeEscaper</code> outside of the specified values (exclusive). </p>
079     *
080     * @param codepointLow below which to escape
081     * @param codepointHigh above which to escape
082     * @return the newly created {@code UnicodeEscaper} instance
083     */
084    public static UnicodeEscaper outsideOf(final int codepointLow, final int codepointHigh) {
085        return new UnicodeEscaper(codepointLow, codepointHigh, false);
086    }
087
088    /**
089     * <p>Constructs a <code>UnicodeEscaper</code> between the specified values (inclusive). </p>
090     *
091     * @param codepointLow above which to escape
092     * @param codepointHigh below which to escape
093     * @return the newly created {@code UnicodeEscaper} instance
094     */
095    public static UnicodeEscaper between(final int codepointLow, final int codepointHigh) {
096        return new UnicodeEscaper(codepointLow, codepointHigh, true);
097    }
098
099    /**
100     * {@inheritDoc}
101     */
102    @Override
103    public boolean translate(final int codepoint, final Writer out) throws IOException {
104        if (between) {
105            if (codepoint < below || codepoint > above) {
106                return false;
107            }
108        } else {
109            if (codepoint >= below && codepoint <= above) {
110                return false;
111            }
112        }
113
114        // TODO: Handle potential + sign per various Unicode escape implementations
115        if (codepoint > 0xffff) {
116            out.write(toUtf16Escape(codepoint));
117        } else {
118          out.write("\\u");
119          out.write(HEX_DIGITS[(codepoint >> 12) & 15]);
120          out.write(HEX_DIGITS[(codepoint >> 8) & 15]);
121          out.write(HEX_DIGITS[(codepoint >> 4) & 15]);
122          out.write(HEX_DIGITS[(codepoint) & 15]);
123        }
124        return true;
125    }
126
127    /**
128     * Converts the given codepoint to a hex string of the form {@code "\\uXXXX"}
129     * 
130     * @param codepoint
131     *            a Unicode code point
132     * @return the hex string for the given codepoint
133     *
134     * @since 3.2
135     */
136    protected String toUtf16Escape(final int codepoint) {
137        return "\\u" + hex(codepoint);
138    }
139}