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 java.io.OutputStream;
021
022import org.apache.commons.codec.CodecPolicy;
023
024/**
025 * Provides Base64 encoding and decoding in a streaming fashion (unlimited size). When encoding the default lineLength
026 * is 76 characters and the default lineEnding is CRLF, but these can be overridden by using the appropriate
027 * constructor.
028 * <p>
029 * The default behavior of the Base64OutputStream is to ENCODE, whereas the default behavior of the Base64InputStream
030 * is to DECODE. But this behavior can be overridden by using a different constructor.
031 * </p>
032 * <p>
033 * This class implements section <cite>6.8. Base64 Content-Transfer-Encoding</cite> from RFC 2045 <cite>Multipurpose
034 * Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</cite> by Freed and Borenstein.
035 * </p>
036 * <p>
037 * Since this class operates directly on byte streams, and not character streams, it is hard-coded to only encode/decode
038 * character encodings which are compatible with the lower 127 ASCII chart (ISO-8859-1, Windows-1252, UTF-8, etc).
039 * </p>
040 * <p>
041 * <b>Note:</b> It is mandatory to close the stream after the last byte has been written to it, otherwise the
042 * final padding will be omitted and the resulting data will be incomplete/inconsistent.
043 * </p>
044 * <p>
045 * You can set the decoding behavior when the input bytes contain leftover trailing bits that cannot be created by a
046 * valid encoding. These can be bits that are unused from the final character or entire characters. The default mode is
047 * lenient decoding.
048 * </p>
049 * <ul>
050 * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
051 * <li>Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid
052 * encoding. Any unused bits from the final character must be zero. Impossible counts of entire final characters are not
053 * allowed.
054 * </ul>
055 * <p>
056 * When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches
057 * the original, i.e. no changes occur on the final character. This requires that the input bytes use the same padding
058 * and alphabet as the encoder.
059 * </p>
060 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
061 * @since 1.4
062 */
063public class Base64OutputStream extends BaseNCodecOutputStream {
064
065    /**
066     * Constructs a Base64OutputStream such that all data written is Base64-encoded to the original provided OutputStream.
067     *
068     * @param outputStream
069     *            OutputStream to wrap.
070     */
071    public Base64OutputStream(final OutputStream outputStream) {
072        this(outputStream, true);
073    }
074
075    /**
076     * Constructs a Base64OutputStream such that all data written is either Base64-encoded or Base64-decoded to the
077     * original provided OutputStream.
078     *
079     * @param outputStream
080     *            OutputStream to wrap.
081     * @param doEncode
082     *            true if we should encode all data written to us, false if we should decode.
083     */
084    public Base64OutputStream(final OutputStream outputStream, final boolean doEncode) {
085        super(outputStream, new Base64(false), doEncode);
086    }
087
088    /**
089     * Constructs a Base64OutputStream such that all data written is either Base64-encoded or Base64-decoded to the
090     * original provided OutputStream.
091     *
092     * @param outputStream
093     *            OutputStream to wrap.
094     * @param doEncode
095     *            true if we should encode all data written to us, false if we should decode.
096     * @param lineLength
097     *            If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to
098     *            the nearest multiple of 4). If lineLength &lt;= 0, the encoded data is not divided into lines. If
099     *            doEncode is false, lineLength is ignored.
100     * @param lineSeparator
101     *            If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n).
102     *            If lineLength &lt;= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored.
103     */
104    public Base64OutputStream(final OutputStream outputStream, final boolean doEncode, final int lineLength, final byte[] lineSeparator) {
105        super(outputStream, new Base64(lineLength, lineSeparator), doEncode);
106    }
107
108    /**
109     * Constructs a Base64OutputStream such that all data written is either Base64-encoded or Base64-decoded to the
110     * original provided OutputStream.
111     *
112     * @param outputStream
113     *            OutputStream to wrap.
114     * @param doEncode
115     *            true if we should encode all data written to us, false if we should decode.
116     * @param lineLength
117     *            If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to
118     *            the nearest multiple of 4). If lineLength &lt;= 0, the encoded data is not divided into lines. If
119     *            doEncode is false, lineLength is ignored.
120     * @param lineSeparator
121     *            If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n).
122     *            If lineLength &lt;= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored.
123     * @param decodingPolicy The decoding policy.
124     * @since 1.15
125     */
126    public Base64OutputStream(final OutputStream outputStream, final boolean doEncode, final int lineLength, final byte[] lineSeparator,
127        final CodecPolicy decodingPolicy) {
128        super(outputStream, new Base64(lineLength, lineSeparator, false, decodingPolicy), doEncode);
129    }
130}