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