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 output 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 output, final BaseNCodec basedCodec, final boolean doEncode) {
058        super(output);
059        this.baseNCodec = basedCodec;
060        this.doEncode = doEncode;
061    }
062
063    /**
064     * Writes the specified {@code byte} to this output stream.
065     *
066     * @param i
067     *            source byte
068     * @throws IOException
069     *             if an I/O error occurs.
070     */
071    @Override
072    public void write(final int i) throws IOException {
073        singleByte[0] = (byte) i;
074        write(singleByte, 0, 1);
075    }
076
077    /**
078     * Writes {@code len} bytes from the specified {@code b} array starting at {@code offset} to this
079     * output stream.
080     *
081     * @param array
082     *            source byte array
083     * @param offset
084     *            where to start reading the bytes
085     * @param len
086     *            maximum number of bytes to write
087     *
088     * @throws IOException
089     *             if an I/O error occurs.
090     * @throws NullPointerException
091     *             if the byte array parameter is null
092     * @throws IndexOutOfBoundsException
093     *             if offset, len or buffer size are invalid
094     */
095    @Override
096    public void write(final byte array[], final int offset, final int len) throws IOException {
097        Objects.requireNonNull(array, "array");
098        if (offset < 0 || len < 0) {
099            throw new IndexOutOfBoundsException();
100        } else if (offset > array.length || offset + len > array.length) {
101            throw new IndexOutOfBoundsException();
102        } else if (len > 0) {
103            if (doEncode) {
104                baseNCodec.encode(array, offset, len, context);
105            } else {
106                baseNCodec.decode(array, offset, len, context);
107            }
108            flush(false);
109        }
110    }
111
112    /**
113     * Flushes this output stream and forces any buffered output bytes to be written out to the stream. If propagate is
114     * true, the wrapped stream will also be flushed.
115     *
116     * @param propagate
117     *            boolean flag to indicate whether the wrapped OutputStream should also be flushed.
118     * @throws IOException
119     *             if an I/O error occurs.
120     */
121    private void flush(final boolean propagate) throws IOException {
122        final int avail = baseNCodec.available(context);
123        if (avail > 0) {
124            final byte[] buf = new byte[avail];
125            final int c = baseNCodec.readResults(buf, 0, avail, context);
126            if (c > 0) {
127                out.write(buf, 0, c);
128            }
129        }
130        if (propagate) {
131            out.flush();
132        }
133    }
134
135    /**
136     * Flushes this output stream and forces any buffered output bytes to be written out to the stream.
137     *
138     * @throws IOException
139     *             if an I/O error occurs.
140     */
141    @Override
142    public void flush() throws IOException {
143        flush(true);
144    }
145
146    /**
147     * Closes this output stream and releases any system resources associated with the stream.
148     * <p>
149     * To write the EOF marker without closing the stream, call {@link #eof()} or use an
150     * <a href="https://commons.apache.org/proper/commons-io/">Apache Commons IO</a> <a href=
151     * "https://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/output/CloseShieldOutputStream.html"
152     * >CloseShieldOutputStream</a>.
153     * </p>
154     *
155     * @throws IOException
156     *             if an I/O error occurs.
157     */
158    @Override
159    public void close() throws IOException {
160        eof();
161        flush();
162        out.close();
163    }
164
165    /**
166     * Writes EOF.
167     *
168     * @throws IOException
169     *             if an I/O error occurs.
170     * @since 1.11
171     */
172    public void eof() throws IOException {
173        // Notify encoder of EOF (-1).
174        if (doEncode) {
175            baseNCodec.encode(singleByte, 0, EOF, context);
176        } else {
177            baseNCodec.decode(singleByte, 0, EOF, context);
178        }
179    }
180
181}