Charsets.java

/*
 * Copyright (c) 2013-2014 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 io.werval.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;

/**
 * Utilities to work with charsets.
 */
public final class Charsets
{
    /**
     * 8-bit UTF (UCS Transformation Format).
     */
    public static final Charset UTF_8 = Charset.forName( "UTF-8" );

    /**
     * ISO Latin Alphabet No 1, as known as <tt>ISO-LATIN-1</tt>.
     */
    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<Map<Charset, CharsetEncoder>> ENCODERS;
    private static final ThreadLocal<Map<Charset, CharsetDecoder>> DECODERS;

    static
    {
        ENCODERS = new ThreadLocal<Map<Charset, CharsetEncoder>>()
        {
            @Override
            protected Map<Charset, CharsetEncoder> initialValue()
            {
                return new IdentityHashMap<>( 4 );
            }
        };
        DECODERS = new ThreadLocal<Map<Charset, CharsetDecoder>>()
        {
            @Override
            protected Map<Charset, CharsetDecoder> initialValue()
            {
                return new IdentityHashMap<>( 4 );
            }
        };
    }

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

        Map<Charset, CharsetEncoder> map = ENCODERS.get();
        CharsetEncoder encoder = map.get( charset );
        if( encoder != null )
        {
            encoder.reset();
            encoder.onMalformedInput( CodingErrorAction.REPLACE );
            encoder.onUnmappableCharacter( CodingErrorAction.REPLACE );
            return encoder;
        }

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

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

        Map<Charset, CharsetDecoder> map = DECODERS.get();
        CharsetDecoder decoder = map.get( charset );
        if( decoder != null )
        {
            decoder.reset();
            decoder.onMalformedInput( CodingErrorAction.REPLACE );
            decoder.onUnmappableCharacter( CodingErrorAction.REPLACE );
            return decoder;
        }

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

    private Charsets()
    {
    }
}