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     * 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     * @throws IOException
086     *             if an I/O error occurs.
087     * @since 1.11
088     */
089    public void eof() throws IOException {
090        // Notify encoder of EOF (-1).
091        if (doEncode) {
092            baseNCodec.encode(singleByte, 0, EOF, context);
093        } else {
094            baseNCodec.decode(singleByte, 0, EOF, context);
095        }
096    }
097
098    /**
099     * Flushes this output stream and forces any buffered output bytes to be written out to the stream.
100     *
101     * @throws IOException
102     *             if an I/O error occurs.
103     */
104    @Override
105    public void flush() throws IOException {
106        flush(true);
107    }
108
109    /**
110     * Flushes this output stream and forces any buffered output bytes to be written out to the stream. If propagate is
111     * true, the wrapped stream will also be flushed.
112     *
113     * @param propagate
114     *            boolean flag to indicate whether the wrapped OutputStream should also be flushed.
115     * @throws IOException
116     *             if an I/O error occurs.
117     */
118    private void flush(final boolean propagate) throws IOException {
119        final int avail = baseNCodec.available(context);
120        if (avail > 0) {
121            final byte[] buf = new byte[avail];
122            final int c = baseNCodec.readResults(buf, 0, avail, context);
123            if (c > 0) {
124                out.write(buf, 0, c);
125            }
126        }
127        if (propagate) {
128            out.flush();
129        }
130    }
131
132    /**
133     * Returns true if decoding behavior is strict. Decoding will raise an
134     * {@link IllegalArgumentException} if trailing bits are not part of a valid encoding.
135     *
136     * <p>The default is false for lenient encoding. Decoding will compose trailing bits
137     * into 8-bit bytes and discard the remainder.
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        } else if (offset > array.length || offset + len > array.length) {
170            throw new IndexOutOfBoundsException();
171        } else if (len > 0) {
172            if (doEncode) {
173                baseNCodec.encode(array, offset, len, context);
174            } else {
175                baseNCodec.decode(array, offset, len, context);
176            }
177            flush(false);
178        }
179    }
180
181    /**
182     * Writes the specified {@code byte} to this output stream.
183     *
184     * @param i
185     *            source byte
186     * @throws IOException
187     *             if an I/O error occurs.
188     */
189    @Override
190    public void write(final int i) throws IOException {
191        singleByte[0] = (byte) i;
192        write(singleByte, 0, 1);
193    }
194
195}