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;
021
022/**
023 * Translates codepoints to their Unicode escaped value.
024 *
025 * @since 1.0
026 */
027public class UnicodeEscaper extends CodePointTranslator {
028
029    /** int value representing the lowest codepoint boundary. */
030    private final int below;
031    /** int value representing the highest codepoint boundary. */
032    private final int above;
033    /** whether to escape between the boundaries or outside them. */
034    private final boolean between;
035
036    /**
037     * <p>Constructs a {@code UnicodeEscaper} for all characters.
038     * </p>
039     */
040    public UnicodeEscaper() {
041        this(0, Integer.MAX_VALUE, true);
042    }
043
044    /**
045     * <p>Constructs a {@code UnicodeEscaper} for the specified range. This is
046     * the underlying method for the other constructors/builders. The {@code below}
047     * and {@code above} boundaries are inclusive when {@code between} is
048     * {@code true} and exclusive when it is {@code false}.</p>
049     *
050     * @param below int value representing the lowest codepoint boundary
051     * @param above int value representing the highest codepoint boundary
052     * @param between whether to escape between the boundaries or outside them
053     */
054    protected UnicodeEscaper(final int below, final int above, final boolean between) {
055        this.below = below;
056        this.above = above;
057        this.between = between;
058    }
059
060    /**
061     * <p>Constructs a {@code UnicodeEscaper} below the specified value (exclusive).</p>
062     *
063     * @param codepoint below which to escape
064     * @return The newly created {@code UnicodeEscaper} instance
065     */
066    public static UnicodeEscaper below(final int codepoint) {
067        return outsideOf(codepoint, Integer.MAX_VALUE);
068    }
069
070    /**
071     * <p>Constructs a {@code UnicodeEscaper} above the specified value (exclusive).</p>
072     *
073     * @param codepoint above which to escape
074     * @return The newly created {@code UnicodeEscaper} instance
075     */
076    public static UnicodeEscaper above(final int codepoint) {
077        return outsideOf(0, codepoint);
078    }
079
080    /**
081     * <p>Constructs a {@code UnicodeEscaper} outside of the specified values (exclusive).</p>
082     *
083     * @param codepointLow below which to escape
084     * @param codepointHigh above which to escape
085     * @return The newly created {@code UnicodeEscaper} instance
086     */
087    public static UnicodeEscaper outsideOf(final int codepointLow, final int codepointHigh) {
088        return new UnicodeEscaper(codepointLow, codepointHigh, false);
089    }
090
091    /**
092     * <p>Constructs a {@code UnicodeEscaper} between the specified values (inclusive).</p>
093     *
094     * @param codepointLow above which to escape
095     * @param codepointHigh below which to escape
096     * @return The newly created {@code UnicodeEscaper} instance
097     */
098    public static UnicodeEscaper between(final int codepointLow, final int codepointHigh) {
099        return new UnicodeEscaper(codepointLow, codepointHigh, true);
100    }
101
102    /**
103     * {@inheritDoc}
104     */
105    @Override
106    public boolean translate(final int codepoint, final Writer out) throws IOException {
107        if (between) {
108            if (codepoint < below || codepoint > above) {
109                return false;
110            }
111        } else {
112            if (codepoint >= below && codepoint <= above) {
113                return false;
114            }
115        }
116
117        if (codepoint > 0xffff) {
118            out.write(toUtf16Escape(codepoint));
119        } else {
120          out.write("\\u");
121          out.write(HEX_DIGITS[(codepoint >> 12) & 15]);
122          out.write(HEX_DIGITS[(codepoint >> 8) & 15]);
123          out.write(HEX_DIGITS[(codepoint >> 4) & 15]);
124          out.write(HEX_DIGITS[(codepoint) & 15]);
125        }
126        return true;
127    }
128
129    /**
130     * Converts the given codepoint to a hex string of the form {@code "\\uXXXX"}.
131     *
132     * @param codepoint
133     *            a Unicode code point
134     * @return The hex string for the given codepoint
135     *
136     */
137    protected String toUtf16Escape(final int codepoint) {
138        return "\\u" + hex(codepoint);
139    }
140}