/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You under the Apache License, Version 2.0

  * (the "License"); you may not use this file except in compliance with

  * the License.  You may obtain a copy of the License at

  * 

  *      http://www.apache.org/licenses/LICENSE-2.0

  * 

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.apache.commons.io;

 import java.nio.charset.Charset;

 import java.nio.charset.UnsupportedCharsetException;

 import java.util.Collections;

 import java.util.SortedMap;

 import java.util.TreeMap;

 /**

  * Charsets required of every implementation of the Java platform.

  * 

  * From the Java documentation <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">

  * Standard charsets</a>:

  * <p>

  * <cite>Every implementation of the Java platform is required to support the following character encodings. Consult

  * the release documentation for your implementation to see if any other encodings are supported. Consult the release

  * documentation for your implementation to see if any other encodings are supported. </cite>

  * </p>

  * 

  * <ul>

  * <li><code>US-ASCII</code><br/>

  * Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set.</li>

  * <li><code>ISO-8859-1</code><br/>

  * ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.</li>

  * <li><code>UTF-8</code><br/>

  * Eight-bit Unicode Transformation Format.</li>

  * <li><code>UTF-16BE</code><br/>

  * Sixteen-bit Unicode Transformation Format, big-endian byte order.</li>

  * <li><code>UTF-16LE</code><br/>

  * Sixteen-bit Unicode Transformation Format, little-endian byte order.</li>

  * <li><code>UTF-16</code><br/>

  * Sixteen-bit Unicode Transformation Format, byte order specified by a mandatory initial byte-order mark (either order

  * accepted on input, big-endian used on output.)</li>

  * </ul>

  * 

  * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

  * @since 2.3

  * @version $Id: Charsets.java 1415850 2012-11-30 20:51:39Z ggregory $

  */

 public class Charsets {

     //

     // This class should only contain Charset instances for required encodings. This guarantees that it will load

     // correctly and without delay on all Java platforms.

     //

     /**

      * Constructs a sorted map from canonical charset names to charset objects required of every implementation of the

      * Java platform.

      * <p>

      * From the Java documentation <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">

      * Standard charsets</a>:

      * </p>

      * 

      * @return An immutable, case-insensitive map from canonical charset names to charset objects.

      * @see Charset#availableCharsets()

      * @since 2.5

      */

     public static SortedMap<String, Charset> requiredCharsets() {

         // maybe cache?

         final TreeMap<String, Charset> m = new TreeMap<String, Charset>(String.CASE_INSENSITIVE_ORDER);

         m.put(ISO_8859_1.name(), ISO_8859_1);

         m.put(US_ASCII.name(), US_ASCII);

         m.put(UTF_16.name(), UTF_16);

         m.put(UTF_16BE.name(), UTF_16BE);

         m.put(UTF_16LE.name(), UTF_16LE);

         m.put(UTF_8.name(), UTF_8);

         return Collections.unmodifiableSortedMap(m);

     }

     /**

      * Returns the given Charset or the default Charset if the given Charset is null.

      * 

      * @param charset

      *            A charset or null.

      * @return the given Charset or the default Charset if the given Charset is null

      */

     public static Charset toCharset(final Charset charset) {

         return charset == null ? Charset.defaultCharset() : charset;

     }

     /**

      * Returns a Charset for the named charset. If the name is null, return the default Charset.

      * 

      * @param charset

      *            The name of the requested charset, may be null.

      * @return a Charset for the named charset

      * @throws UnsupportedCharsetException

      *             If the named charset is unavailable

      */

     public static Charset toCharset(final String charset) {

         return charset == null ? Charset.defaultCharset() : Charset.forName(charset);

     }

     /**

      * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1. </p>

      * <p>

      * Every implementation of the Java platform is required to support this character encoding.

      * </p>

      * 

      * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      */

     public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");

     /**

      * <p>

      * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of the Unicode character set.

      * </p>

      * <p>

      * Every implementation of the Java platform is required to support this character encoding.

      * </p>

      * 

      * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      */

     public static final Charset US_ASCII = Charset.forName("US-ASCII");

     /**

      * <p>

      * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory initial byte-order mark

      * (either order accepted on input, big-endian used on output)

      * </p>

      * <p>

      * Every implementation of the Java platform is required to support this character encoding.

      * </p>

      * 

      * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      */

     public static final Charset UTF_16 = Charset.forName("UTF-16");

     /**

      * <p>

      * Sixteen-bit Unicode Transformation Format, big-endian byte order.

      * </p>

      * <p>

      * Every implementation of the Java platform is required to support this character encoding.

      * </p>

      * 

      * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      */

     public static final Charset UTF_16BE = Charset.forName("UTF-16BE");

     /**

      * <p>

      * Sixteen-bit Unicode Transformation Format, little-endian byte order.

      * </p>

      * <p>

      * Every implementation of the Java platform is required to support this character encoding.

      * </p>

      * 

      * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      */

     public static final Charset UTF_16LE = Charset.forName("UTF-16LE");

     /**

      * <p>

      * Eight-bit Unicode Transformation Format.

      * </p>

      * <p>

      * Every implementation of the Java platform is required to support this character encoding.

      * </p>

      * 

      * @see <a href="http://docs.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      */

     public static final Charset UTF_8 = Charset.forName("UTF-8");

 }