net.freeutils.charset.CharsetProvider Maven / Gradle / Ivy

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/*
 *  Copyright © 2005-2015 Amichai Rothman
 *
 *  This file is part of JCharset - the Java Charset package.
 *
 *  JCharset is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  JCharset is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with JCharset.  If not, see .
 *
 *  For additional info see http://www.freeutils.net/source/jcharset/
 */

package net.freeutils.charset;

import java.nio.charset.Charset;
import java.util.*;

/**
 * The CharsetProvider class is a Charset Provider implementation.
 *
 * @author  Amichai Rothman
 * @since   2005-06-10
 */
public class CharsetProvider extends java.nio.charset.spi.CharsetProvider {

    static Map name2charset;
    static Collection charsets;

    /**
     * Retrieves a charset for the given charset name.
     *
     * @param charsetName the name of the requested charset;
     *        may be either a canonical name or an alias
     *
     * @return a charset object for the named charset,
     *         or null if the named charset
     *         is not supported by this provider
     */
    public Charset charsetForName(String charsetName) {
        if (name2charset == null)
            init();

        // get charset instance for given name (case insensitive)
        Charset c = (Charset)name2charset.get(charsetName.toLowerCase());
        if (c != null) {
            try {
                return c.getClass().newInstance();
            } catch (Exception ignore) {
                // if we can't create an instance, we don't
            }
        }
        return null;
    }

    /**
     * Creates an iterator that iterates over the charsets supported by this
     * provider.  This method is used in the implementation of the {@link
     * java.nio.charset.Charset#availableCharsets Charset.availableCharsets}
     * method.
     *
     * @return the new iterator
     */
    public Iterator charsets() {
        if (charsets == null)
            init();

        return charsets.iterator();
    }

    /**
     * Initializes this charset provider's data.
     */
    void init() {
        // prepare supported charsets
        Charset[] cs = {
            new UTF7Charset(), new UTF7OptionalCharset(),
            new SCGSMCharset(), new CCGSMCharset(),
            new SCPackedGSMCharset(), new CCPackedGSMCharset(),
            new HPRoman8Charset(), new KOI8UCharset(),
            new ISO88598Charset(), new ISO88596Charset(),
            new MIKCharset()
        };

        // initialize charset collection
        charsets = Collections.unmodifiableCollection(Arrays.asList(cs));

        // initialize name to charset map
        Map n2c = new HashMap();
        for (int i = 0; i < cs.length; i++) {
            Charset c = cs[i];
            n2c.put(c.name().toLowerCase(), c);
            for (Iterator a = c.aliases().iterator(); a.hasNext();)
                n2c.put(((String)a.next()).toLowerCase(), c);
        }
        name2charset = n2c;
    }

}