src/main/java/org/apache/commons/codec/binary/Base64InputStream.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.codec.binary;

import java.io.InputStream;

import org.apache.commons.codec.CodecPolicy;

/**
 * Provides Base64 encoding and decoding in a streaming fashion (unlimited size). When encoding the default lineLength
 * is 76 characters and the default lineEnding is CRLF, but these can be overridden by using the appropriate
 * constructor.
 * <p>
 * The default behavior of the Base64InputStream is to DECODE, whereas the default behavior of the Base64OutputStream
 * is to ENCODE, but this behavior can be overridden by using a different constructor.
 * </p>
 * <p>
 * This class implements section <cite>6.8. Base64 Content-Transfer-Encoding</cite> from RFC 2045 <cite>Multipurpose
 * Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</cite> by Freed and Borenstein.
 * </p>
 * <p>
 * Since this class operates directly on byte streams, and not character streams, it is hard-coded to only encode/decode
 * character encodings which are compatible with the lower 127 ASCII chart (ISO-8859-1, Windows-1252, UTF-8, etc).
 * </p>
 * <p>
 * You can set the decoding behavior when the input bytes contain leftover trailing bits that cannot be created by a
 * valid encoding. These can be bits that are unused from the final character or entire characters. The default mode is
 * lenient decoding.
 * </p>
 * <ul>
 * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
 * <li>Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid
 * encoding. Any unused bits from the final character must be zero. Impossible counts of entire final characters are not
 * allowed.
 * </ul>
 * <p>
 * When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches
 * the original, i.e. no changes occur on the final character. This requires that the input bytes use the same padding
 * and alphabet as the encoder.
 * </p>
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
 * @since 1.4
 */
public class Base64InputStream extends BaseNCodecInputStream {

    /**
     * Creates a Base64InputStream such that all data read is Base64-decoded from the original provided InputStream.
     *
     * @param in
     *            InputStream to wrap.
     */
    public Base64InputStream(final InputStream in) {
        this(in, false);
    }

    /**
     * Creates a Base64InputStream such that all data read is either Base64-encoded or Base64-decoded from the original
     * provided InputStream.
     *
     * @param in
     *            InputStream to wrap.
     * @param doEncode
     *            true if we should encode all data read from us, false if we should decode.
     */
    public Base64InputStream(final InputStream in, final boolean doEncode) {
        super(in, new Base64(false), doEncode);
    }

    /**
     * Creates a Base64InputStream such that all data read is either Base64-encoded or Base64-decoded from the original
     * provided InputStream.
     *
     * @param in
     *            InputStream to wrap.
     * @param doEncode
     *            true if we should encode all data read from us, false if we should decode.
     * @param lineLength
     *            If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to
     *            nearest multiple of 4). If lineLength &lt;= 0, the encoded data is not divided into lines. If doEncode
     *            is false, lineLength is ignored.
     * @param lineSeparator
     *            If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n).
     *            If lineLength &lt;= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored.
     */
    public Base64InputStream(final InputStream in, final boolean doEncode,
                             final int lineLength, final byte[] lineSeparator) {
        super(in, new Base64(lineLength, lineSeparator), doEncode);
    }

    /**
     * Creates a Base64InputStream such that all data read is either Base64-encoded or Base64-decoded from the original
     * provided InputStream.
     *
     * @param in
     *            InputStream to wrap.
     * @param doEncode
     *            true if we should encode all data read from us, false if we should decode.
     * @param lineLength
     *            If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to
     *            nearest multiple of 4). If lineLength &lt;= 0, the encoded data is not divided into lines. If doEncode
     *            is false, lineLength is ignored.
     * @param lineSeparator
     *            If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n).
     *            If lineLength &lt;= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored.
     * @param decodingPolicy The decoding policy.
     * @since 1.15
     */
    public Base64InputStream(final InputStream in, final boolean doEncode,
                             final int lineLength, final byte[] lineSeparator, final CodecPolicy decodingPolicy) {
        super(in, new Base64(lineLength, lineSeparator, false, decodingPolicy), doEncode);
    }
}