    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.codec.binary;
    019
    020import static org.apache.commons.codec.binary.BaseNCodec.EOF;
    021
    022import java.io.FilterOutputStream;
    023import java.io.IOException;
    024import java.io.OutputStream;
    025import java.util.Objects;
    026
    027import org.apache.commons.codec.binary.BaseNCodec.Context;
    028
    029/**
    030 * Abstract superclass for Base-N output streams.
    031 * <p>
    032 * To write the EOF marker without closing the stream, call {@link #eof()} or use an <a
    033 * href="https://commons.apache.org/proper/commons-io/">Apache Commons IO</a> <a href=
    034 * "https://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/output/CloseShieldOutputStream.html"
    035 * >CloseShieldOutputStream</a>.
    036 * </p>
    037 *
    038 * @since 1.5
    039 */
    040public class BaseNCodecOutputStream extends FilterOutputStream {
    041
    042    private final boolean doEncode;
    043
    044    private final BaseNCodec baseNCodec;
    045
    046    private final byte[] singleByte = new byte[1];
    047
    048    private final Context context = new Context();
    049
    050    /**
    051     * TODO should this be protected?
    052     *
    053     * @param outputStream the underlying output or null.
    054     * @param basedCodec a BaseNCodec.
    055     * @param doEncode true to encode, false to decode, TODO should be an enum?
    056     */
    057    public BaseNCodecOutputStream(final OutputStream outputStream, final BaseNCodec basedCodec, final boolean doEncode) {
    058        super(outputStream);
    059        this.baseNCodec = basedCodec;
    060        this.doEncode = doEncode;
    061    }
    062
    063    /**
    064     * Closes this output stream and releases any system resources associated with the stream.
    065     * <p>
    066     * To write the EOF marker without closing the stream, call {@link #eof()} or use an
    067     * <a href="https://commons.apache.org/proper/commons-io/">Apache Commons IO</a> <a href=
    068     * "https://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/output/CloseShieldOutputStream.html"
    069     * >CloseShieldOutputStream</a>.
    070     * </p>
    071     *
    072     * @throws IOException
    073     *             if an I/O error occurs.
    074     */
    075    @Override
    076    public void close() throws IOException {
    077        eof();
    078        flush();
    079        out.close();
    080    }
    081
    082    /**
    083     * Writes EOF.
    084     *
    085     * @since 1.11
    086     */
    087    public void eof() {
    088        // Notify encoder of EOF (-1).
    089        if (doEncode) {
    090            baseNCodec.encode(singleByte, 0, EOF, context);
    091        } else {
    092            baseNCodec.decode(singleByte, 0, EOF, context);
    093        }
    094    }
    095
    096    /**
    097     * Flushes this output stream and forces any buffered output bytes to be written out to the stream.
    098     *
    099     * @throws IOException
    100     *             if an I/O error occurs.
    101     */
    102    @Override
    103    public void flush() throws IOException {
    104        flush(true);
    105    }
    106
    107    /**
    108     * Flushes this output stream and forces any buffered output bytes to be written out to the stream. If propagate is
    109     * true, the wrapped stream will also be flushed.
    110     *
    111     * @param propagate
    112     *            boolean flag to indicate whether the wrapped OutputStream should also be flushed.
    113     * @throws IOException
    114     *             if an I/O error occurs.
    115     */
    116    private void flush(final boolean propagate) throws IOException {
    117        final int avail = baseNCodec.available(context);
    118        if (avail > 0) {
    119            final byte[] buf = new byte[avail];
    120            final int c = baseNCodec.readResults(buf, 0, avail, context);
    121            if (c > 0) {
    122                out.write(buf, 0, c);
    123            }
    124        }
    125        if (propagate) {
    126            out.flush();
    127        }
    128    }
    129
    130    /**
    131     * Returns true if decoding behavior is strict. Decoding will raise an
    132     * {@link IllegalArgumentException} if trailing bits are not part of a valid encoding.
    133     *
    134     * <p>
    135     * The default is false for lenient encoding. Decoding will compose trailing bits
    136     * into 8-bit bytes and discard the remainder.
    137     * </p>
    138     *
    139     * @return true if using strict decoding
    140     * @since 1.15
    141     */
    142    public boolean isStrictDecoding() {
    143        return baseNCodec.isStrictDecoding();
    144    }
    145
    146    /**
    147     * Writes {@code len} bytes from the specified {@code b} array starting at {@code offset} to this
    148     * output stream.
    149     *
    150     * @param array
    151     *            source byte array
    152     * @param offset
    153     *            where to start reading the bytes
    154     * @param len
    155     *            maximum number of bytes to write
    156     *
    157     * @throws IOException
    158     *             if an I/O error occurs.
    159     * @throws NullPointerException
    160     *             if the byte array parameter is null
    161     * @throws IndexOutOfBoundsException
    162     *             if offset, len or buffer size are invalid
    163     */
    164    @Override
    165    public void write(final byte[] array, final int offset, final int len) throws IOException {
    166        Objects.requireNonNull(array, "array");
    167        if (offset < 0 || len < 0) {
    168            throw new IndexOutOfBoundsException();
    169        }
    170        if (offset > array.length || offset + len > array.length) {
    171            throw new IndexOutOfBoundsException();
    172        }
    173        if (len > 0) {
    174            if (doEncode) {
    175                baseNCodec.encode(array, offset, len, context);
    176            } else {
    177                baseNCodec.decode(array, offset, len, context);
    178            }
    179            flush(false);
    180        }
    181    }
    182
    183    /**
    184     * Writes the specified {@code byte} to this output stream.
    185     *
    186     * @param i
    187     *            source byte
    188     * @throws IOException
    189     *             if an I/O error occurs.
    190     */
    191    @Override
    192    public void write(final int i) throws IOException {
    193        singleByte[0] = (byte) i;
    194        write(singleByte, 0, 1);
    195    }
    196
    197}