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.InputStream;
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 Base64InputStream is to DECODE, whereas the default behavior of the Base64OutputStream
030 * is to ENCODE, 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 * You can set the decoding behavior when the input bytes contain leftover trailing bits that cannot be created by a
042 * valid encoding. These can be bits that are unused from the final character or entire characters. The default mode is
043 * lenient decoding.
044 * </p>
045 * <ul>
046 * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
047 * <li>Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid
048 * encoding. Any unused bits from the final character must be zero. Impossible counts of entire final characters are not
049 * allowed.
050 * </ul>
051 * <p>
052 * When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches
053 * the original, i.e. no changes occur on the final character. This requires that the input bytes use the same padding
054 * and alphabet as the encoder.
055 * </p>
056 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
057 * @since 1.4
058 */
059public class Base64InputStream extends BaseNCodecInputStream {
060
061    /**
062     * Constructs a Base64InputStream such that all data read is Base64-decoded from the original provided InputStream.
063     *
064     * @param inputStream
065     *            InputStream to wrap.
066     */
067    public Base64InputStream(final InputStream inputStream) {
068        this(inputStream, false);
069    }
070
071    /**
072     * Constructs a Base64InputStream such that all data read is either Base64-encoded or Base64-decoded from the original
073     * provided InputStream.
074     *
075     * @param inputStream
076     *            InputStream to wrap.
077     * @param doEncode
078     *            true if we should encode all data read from us, false if we should decode.
079     */
080    public Base64InputStream(final InputStream inputStream, final boolean doEncode) {
081        super(inputStream, new Base64(false), doEncode);
082    }
083
084    /**
085     * Constructs a Base64InputStream such that all data read is either Base64-encoded or Base64-decoded from the original
086     * provided InputStream.
087     *
088     * @param inputStream
089     *            InputStream to wrap.
090     * @param doEncode
091     *            true if we should encode all data read from us, false if we should decode.
092     * @param lineLength
093     *            If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to
094     *            the nearest multiple of 4). If lineLength &lt;= 0, the encoded data is not divided into lines. If
095     *            doEncode is false, lineLength is ignored.
096     * @param lineSeparator
097     *            If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n).
098     *            If lineLength &lt;= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored.
099     */
100    public Base64InputStream(final InputStream inputStream, final boolean doEncode, final int lineLength, final byte[] lineSeparator) {
101        super(inputStream, new Base64(lineLength, lineSeparator), doEncode);
102    }
103
104    /**
105     * Constructs a Base64InputStream such that all data read is either Base64-encoded or Base64-decoded from the original
106     * provided InputStream.
107     *
108     * @param inputStream
109     *            InputStream to wrap.
110     * @param doEncode
111     *            true if we should encode all data read from us, false if we should decode.
112     * @param lineLength
113     *            If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to
114     *            the nearest multiple of 4). If lineLength &lt;= 0, the encoded data is not divided into lines. If
115     *            doEncode is false, lineLength is ignored.
116     * @param lineSeparator
117     *            If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n).
118     *            If lineLength &lt;= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored.
119     * @param decodingPolicy The decoding policy.
120     * @since 1.15
121     */
122    public Base64InputStream(final InputStream inputStream, final boolean doEncode, final int lineLength, final byte[] lineSeparator,
123        final CodecPolicy decodingPolicy) {
124        super(inputStream, new Base64(lineLength, lineSeparator, false, decodingPolicy), doEncode);
125    }
126}