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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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.jboss.netty.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.
 */
public final class CharsetUtil {

    /**
     * 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");

    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.
     */
    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.
     */
    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;
    }

    private CharsetUtil() {
        // Unused
    }
}