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The Apache Commons Codec component contains encoders and decoders for various formats such as Base16, Base32, Base64, digest, and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities. This is a port for GWT, which enables program, to use Apache Commons Codec also in the frontend compiled by the gwt compiler to java-script.

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/*
 * 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.codec.binary;

import static org.apache.commons.codec.binary.BaseNCodec.EOF;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import org.apache.commons.codec.binary.BaseNCodec.Context;

import com.google.gwt.core.shared.GwtIncompatible;

/**
 * Abstract superclass for Base-N output streams.
 *
 * @since 1.5
 * @version $Id: BaseNCodecOutputStream.java 1544347 2013-11-21 22:30:31Z ggregory $
 */
@GwtIncompatible("incompatible class")
public class BaseNCodecOutputStream extends FilterOutputStream {

    private final boolean doEncode;

    private final BaseNCodec baseNCodec;

    private final byte[] singleByte = new byte[1];

    private final Context context = new Context();

    // TODO should this be protected?
    public BaseNCodecOutputStream(final OutputStream out, final BaseNCodec basedCodec, final boolean doEncode) {
        super(out);
        this.baseNCodec = basedCodec;
        this.doEncode = doEncode;
    }

    /**
     * Writes the specified byte to this output stream.
     *
     * @param i
     *            source byte
     * @throws IOException
     *             if an I/O error occurs.
     */
    @Override
    public void write(final int i) throws IOException {
        singleByte[0] = (byte) i;
        write(singleByte, 0, 1);
    }

    /**
     * Writes len bytes from the specified b array starting at offset to this
     * output stream.
     *
     * @param b
     *            source byte array
     * @param offset
     *            where to start reading the bytes
     * @param len
     *            maximum number of bytes to write
     *
     * @throws IOException
     *             if an I/O error occurs.
     * @throws NullPointerException
     *             if the byte array parameter is null
     * @throws IndexOutOfBoundsException
     *             if offset, len or buffer size are invalid
     */
    @Override
    public void write(final byte b[], final int offset, final int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        } else if (offset < 0 || len < 0) {
            throw new IndexOutOfBoundsException();
        } else if (offset > b.length || offset + len > b.length) {
            throw new IndexOutOfBoundsException();
        } else if (len > 0) {
            if (doEncode) {
                baseNCodec.encode(b, offset, len, context);
            } else {
                baseNCodec.decode(b, offset, len, context);
            }
            flush(false);
        }
    }

    /**
     * Flushes this output stream and forces any buffered output bytes to be written out to the stream. If propagate is
     * true, the wrapped stream will also be flushed.
     *
     * @param propagate
     *            boolean flag to indicate whether the wrapped OutputStream should also be flushed.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void flush(final boolean propagate) throws IOException {
        final int avail = baseNCodec.available(context);
        if (avail > 0) {
            final byte[] buf = new byte[avail];
            final int c = baseNCodec.readResults(buf, 0, avail, context);
            if (c > 0) {
                out.write(buf, 0, c);
            }
        }
        if (propagate) {
            out.flush();
        }
    }

    /**
     * Flushes this output stream and forces any buffered output bytes to be written out to the stream.
     *
     * @throws IOException
     *             if an I/O error occurs.
     */
    @Override
    public void flush() throws IOException {
        flush(true);
    }

    /**
     * Closes this output stream and releases any system resources associated with the stream.
     *
     * @throws IOException
     *             if an I/O error occurs.
     */
    @Override
    public void close() throws IOException {
        // Notify encoder of EOF (-1).
        if (doEncode) {
            baseNCodec.encode(singleByte, 0, EOF, context);
        } else {
            baseNCodec.decode(singleByte, 0, EOF, context);
        }
        flush();
        out.close();
    }

}