    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 */
    018
    019package org.apache.commons.compress.utils;
    020
    021import java.nio.charset.Charset;
    022
    023/**
    024 * Charsets required of every implementation of the Java platform.
    025 *
    026 * From the Java documentation <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard
    027 * charsets</a>:
    028 * <p>
    029 * <cite>Every implementation of the Java platform is required to support the following character encodings. Consult the
    030 * release documentation for your implementation to see if any other encodings are supported. Consult the release
    031 * documentation for your implementation to see if any other encodings are supported. </cite>
    032 * </p>
    033 *
    034 * <dl>
    035 * <dt><code>US-ASCII</code></dt>
    036 * <dd>Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set.</dd>
    037 * <dt><code>ISO-8859-1</code></dt>
    038 * <dd>ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.</dd>
    039 * <dt><code>UTF-8</code></dt>
    040 * <dd>Eight-bit Unicode Transformation Format.</dd>
    041 * <dt><code>UTF-16BE</code></dt>
    042 * <dd>Sixteen-bit Unicode Transformation Format, big-endian byte order.</dd>
    043 * <dt><code>UTF-16LE</code></dt>
    044 * <dd>Sixteen-bit Unicode Transformation Format, little-endian byte order.</dd>
    045 * <dt><code>UTF-16</code></dt>
    046 * <dd>Sixteen-bit Unicode Transformation Format, byte order specified by a mandatory initial byte-order mark (either order
    047 * accepted on input, big-endian used on output.)</dd>
    048 * </dl>
    049 *
    050 * <p>This class best belongs in the Commons Lang or IO project. Even if a similar class is defined in another Commons
    051 * component, it is not foreseen that Commons Compress would be made to depend on another Commons component.</p>
    052 *
    053 * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    054 * @since 1.4
    055 * @version $Id$
    056 */
    057public class Charsets {
    058
    059    //
    060    // This class should only contain Charset instances for required encodings. This guarantees that it will load correctly and
    061    // without delay on all Java platforms.
    062    //
    063
    064    /**
    065     * Returns the given Charset or the default Charset if the given Charset is null.
    066     *
    067     * @param charset
    068     *            A charset or null.
    069     * @return the given Charset or the default Charset if the given Charset is null
    070     */
    071    public static Charset toCharset(final Charset charset) {
    072        return charset == null ? Charset.defaultCharset() : charset;
    073    }
    074
    075    /**
    076     * Returns a Charset for the named charset. If the name is null, return the default Charset.
    077     *
    078     * @param charset
    079     *            The name of the requested charset, may be null.
    080     * @return a Charset for the named charset
    081     * @throws java.nio.charset.UnsupportedCharsetException
    082     *             If the named charset is unavailable
    083     * @throws java.nio.charset.IllegalCharsetNameException
    084     *             If the given charset name is illegal
    085     */
    086    public static Charset toCharset(final String charset) {
    087        return charset == null ? Charset.defaultCharset() : Charset.forName(charset);
    088    }
    089
    090    /**
    091     * CharsetNamesISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
    092     * <p>
    093     * Every implementation of the Java platform is required to support this character encoding.
    094     * </p>
    095     *
    096     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    097     */
    098    public static final Charset ISO_8859_1 = Charset.forName(CharsetNames.ISO_8859_1);
    099
    100    /**
    101     * <p>
    102     * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.
    103     * </p>
    104     * <p>
    105     * Every implementation of the Java platform is required to support this character encoding.
    106     * </p>
    107     *
    108     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    109     */
    110    public static final Charset US_ASCII = Charset.forName(CharsetNames.US_ASCII);
    111
    112    /**
    113     * <p>
    114     * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark
    115     * (either order accepted on input, big-endian used on output)
    116     * </p>
    117     * <p>
    118     * Every implementation of the Java platform is required to support this character encoding.
    119     * </p>
    120     *
    121     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    122     */
    123    public static final Charset UTF_16 = Charset.forName(CharsetNames.UTF_16);
    124
    125    /**
    126     * <p>
    127     * Sixteen-bit Unicode Transformation Format, big-endian byte order.
    128     * </p>
    129     * <p>
    130     * Every implementation of the Java platform is required to support this character encoding.
    131     * </p>
    132     *
    133     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    134     */
    135    public static final Charset UTF_16BE = Charset.forName(CharsetNames.UTF_16BE);
    136
    137    /**
    138     * <p>
    139     * Sixteen-bit Unicode Transformation Format, little-endian byte order.
    140     * </p>
    141     * <p>
    142     * Every implementation of the Java platform is required to support this character encoding.
    143     * </p>
    144     *
    145     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    146     */
    147    public static final Charset UTF_16LE = Charset.forName(CharsetNames.UTF_16LE);
    148
    149    /**
    150     * <p>
    151     * Eight-bit Unicode Transformation Format.
    152     * </p>
    153     * <p>
    154     * Every implementation of the Java platform is required to support this character encoding.
    155     * </p>
    156     *
    157     * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
    158     */
    159    public static final Charset UTF_8 = Charset.forName(CharsetNames.UTF_8);
    160}