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Commons lib for java,some wrapper functions.
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/*
 * Copyright 2014 the original author or authors.
 *
 * Licensed 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 com.rockagen.commons.util;

import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CodingErrorAction;
import java.util.IdentityHashMap;
import java.util.Map;

/**
 * A utility class that provides various common operations and constants
 * related with {@link Charset} and its relevant classes.
 * @author netty
 * @since JDK1.6
 */
public class CharsetUtil {

	
    //~ Instance fields ==================================================
    
    /**
     * 16-bit UTF (UCS Transformation Format) whose byte order is identified by
     * an optional byte-order mark
     */
    public static final Charset UTF_16 = Charset.forName("UTF-16");

    /**
     * 16-bit UTF (UCS Transformation Format) whose byte order is big-endian
     */
    public static final Charset UTF_16BE = Charset.forName("UTF-16BE");

    /**
     * 16-bit UTF (UCS Transformation Format) whose byte order is little-endian
     */
    public static final Charset UTF_16LE = Charset.forName("UTF-16LE");

    /**
     * 8-bit UTF (UCS Transformation Format)
     */
    public static final Charset UTF_8 = Charset.forName("UTF-8");

    /**
     * ISO Latin Alphabet No. 1, as known as ISO-LATIN-1
     */
    public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");

    /**
     * 7-bit ASCII, as known as ISO646-US or the Basic Latin block of the
     * Unicode character set
     */
    public static final Charset US_ASCII = Charset.forName("US-ASCII");
    
    
    
    //~ Constructors ==================================================
    
    /**
     */
    private CharsetUtil() {
    }

    private static final ThreadLocal> encoders =
        new ThreadLocal>() {
            @Override
            protected Map initialValue() {
                return new IdentityHashMap();
            }
        };

    private static final ThreadLocal> decoders =
        new ThreadLocal>() {
            @Override
            protected Map initialValue() {
                return new IdentityHashMap();
            }
        };

    /**
     * Returns a cached thread-local {@link CharsetEncoder} for the specified charset.
     * @param charset {@link java.nio.charset.Charset}
     * @return {@link java.nio.charset.CharsetEncoder}
     */
    public static CharsetEncoder getEncoder(Charset charset) {
        if (charset == null) {
            throw new NullPointerException("charset");
        }

        Map map = encoders.get();
        CharsetEncoder e = map.get(charset);
        if (e != null) {
            e.reset();
            e.onMalformedInput(CodingErrorAction.REPLACE);
            e.onUnmappableCharacter(CodingErrorAction.REPLACE);
            return e;
        }

        e = charset.newEncoder();
        e.onMalformedInput(CodingErrorAction.REPLACE);
        e.onUnmappableCharacter(CodingErrorAction.REPLACE);
        map.put(charset, e);
        return e;
    }

    /**
     * Returns a cached thread-local {@link CharsetDecoder} for the specified charset.
     * @param charset {@link java.nio.charset.Charset}
     * @return {@link CharsetDecoder}
     */
    public static CharsetDecoder getDecoder(Charset charset) {
        if (charset == null) {
            throw new NullPointerException("charset");
        }

        Map map = decoders.get();
        CharsetDecoder d = map.get(charset);
        if (d != null) {
            d.reset();
            d.onMalformedInput(CodingErrorAction.REPLACE);
            d.onUnmappableCharacter(CodingErrorAction.REPLACE);
            return d;
        }

        d = charset.newDecoder();
        d.onMalformedInput(CodingErrorAction.REPLACE);
        d.onUnmappableCharacter(CodingErrorAction.REPLACE);
        map.put(charset, d);
        return d;
    }

}