/*
 * 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.net.util;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;



Provides Base64 encoding and decoding as defined by RFC 2045.

This class implements section 6.8. Base64 Content-Transfer-Encoding from RFC 2045 Multipurpose
Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies by Freed and Borenstein.


The class can be parameterized in the following manner with various constructors:

URL-safe mode: Default off.
Line length: Default 76. Line length that aren't multiples of 4 will still essentially end up being multiples of
4 in the encoded data.
Line separator: Default is CRLF ("\r\n")


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).

See Also:
RFC 2045
Since:
2.2
Version:
$Id: Base64.java 1697293 2015-08-24 01:01:00Z sebb $/**
 * Provides Base64 encoding and decoding as defined by RFC 2045.
 *
 * <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>
 * The class can be parameterized in the following manner with various constructors:
 * <ul>
 * <li>URL-safe mode: Default off.</li>
 * <li>Line length: Default 76. Line length that aren't multiples of 4 will still essentially end up being multiples of
 * 4 in the encoded data.
 * <li>Line separator: Default is CRLF ("\r\n")</li>
 * </ul>
 * <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>
 *
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
 * @since 2.2
 * @version $Id: Base64.java 1697293 2015-08-24 01:01:00Z sebb $
 */
public class Base64 {
    private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;

    private static final int DEFAULT_BUFFER_SIZE = 8192;

    
Chunk size per RFC 2045 section 6.8.
 The 76 character limit does not count the trailing CRLF, but counts all other characters, including any equal signs. 
See Also:
RFC 2045 section 6.8/**
     * Chunk size per RFC 2045 section 6.8.
     *
     * <p>
     * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
     * equal signs.
     * </p>
     *
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
     */
    static final int CHUNK_SIZE = 76;

    
Chunk separator per RFC 2045 section 2.1.
See Also:
RFC 2045 section 2.1/**
     * Chunk separator per RFC 2045 section 2.1.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
     */
    private static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};

    private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];

    
This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
equivalents as specified in Table 1 of RFC 2045.
Thanks to "commons" project in ws.apache.org for this code.
http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
/**
     * This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
     * equivalents as specified in Table 1 of RFC 2045.
     *
     * Thanks to "commons" project in ws.apache.org for this code.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     */
    private static final byte[] STANDARD_ENCODE_TABLE = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
    };

    
This is a copy of the STANDARD_ENCODE_TABLE above, but with + and /
changed to - and _ to make the encoded Base64 results more URL-SAFE.
This table is only used when the Base64's mode is set to URL-SAFE.
/**
     * This is a copy of the STANDARD_ENCODE_TABLE above, but with + and /
     * changed to - and _ to make the encoded Base64 results more URL-SAFE.
     * This table is only used when the Base64's mode is set to URL-SAFE.
     */
    private static final byte[] URL_SAFE_ENCODE_TABLE = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_'
    };

    
Byte used to pad output.
/**
     * Byte used to pad output.
     */
    private static final byte PAD = '=';

    
This array is a lookup table that translates Unicode characters drawn from the "Base64 Alphabet" (as specified in
Table 1 of RFC 2045) into their 6-bit positive integer equivalents. Characters that are not in the Base64
alphabet but fall within the bounds of the array are translated to -1.
Note: '+' and '-' both decode to 62. '/' and '_' both decode to 63. This means decoder seamlessly handles both
URL_SAFE and STANDARD base64. (The encoder, on the other hand, needs to know ahead of time what to emit).
Thanks to "commons" project in ws.apache.org for this code.
http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
/**
     * This array is a lookup table that translates Unicode characters drawn from the "Base64 Alphabet" (as specified in
     * Table 1 of RFC 2045) into their 6-bit positive integer equivalents. Characters that are not in the Base64
     * alphabet but fall within the bounds of the array are translated to -1.
     *
     * Note: '+' and '-' both decode to 62. '/' and '_' both decode to 63. This means decoder seamlessly handles both
     * URL_SAFE and STANDARD base64. (The encoder, on the other hand, needs to know ahead of time what to emit).
     *
     * Thanks to "commons" project in ws.apache.org for this code.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     */
    private static final byte[] DECODE_TABLE = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, 62, -1, 63, 52, 53, 54,
            55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
            5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
            24, 25, -1, -1, -1, -1, 63, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34,
            35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
    };

    
Mask used to extract 6 bits, used when encoding /** Mask used to extract 6 bits, used when encoding */
    private static final int MASK_6BITS = 0x3f;

    
Mask used to extract 8 bits, used in decoding base64 bytes /** Mask used to extract 8 bits, used in decoding base64 bytes */
    private static final int MASK_8BITS = 0xff;

    // The static final fields above are used for the original static byte[] methods on Base64.
    // The private member fields below are used with the new streaming approach, which requires
    // some state be preserved between calls of encode() and decode().

    
Encode table to use: either STANDARD or URL_SAFE. Note: the DECODE_TABLE above remains static because it is able
to decode both STANDARD and URL_SAFE streams, but the encodeTable must be a member variable so we can switch
between the two modes.
/**
     * Encode table to use: either STANDARD or URL_SAFE. Note: the DECODE_TABLE above remains static because it is able
     * to decode both STANDARD and URL_SAFE streams, but the encodeTable must be a member variable so we can switch
     * between the two modes.
     */
    private final byte[] encodeTable;

    
Line length for encoding. Not used when decoding. A value of zero or less implies no chunking of the base64
encoded data.
/**
     * Line length for encoding. Not used when decoding. A value of zero or less implies no chunking of the base64
     * encoded data.
     */
    private final int lineLength;

    
Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
/**
     * Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
     */
    private final byte[] lineSeparator;

    
Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
decodeSize = 3 + lineSeparator.length;
/**
     * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
     * <code>decodeSize = 3 + lineSeparator.length;</code>
     */
    private final int decodeSize;

    
Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
encodeSize = 4 + lineSeparator.length;
/**
     * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
     * <code>encodeSize = 4 + lineSeparator.length;</code>
     */
    private final int encodeSize;

    
Buffer for streaming.
/**
     * Buffer for streaming.
     */
    private byte[] buffer;

    
Position where next character should be written in the buffer.
/**
     * Position where next character should be written in the buffer.
     */
    private int pos;

    
Position where next character should be read from the buffer.
/**
     * Position where next character should be read from the buffer.
     */
    private int readPos;

    
Variable tracks how many characters have been written to the current line. Only used when encoding. We use it to
make sure each encoded line never goes beyond lineLength (if lineLength > 0).
/**
     * Variable tracks how many characters have been written to the current line. Only used when encoding. We use it to
     * make sure each encoded line never goes beyond lineLength (if lineLength > 0).
     */
    private int currentLinePos;

    
Writes to the buffer only occur after every 3 reads when encoding, an every 4 reads when decoding. This variable
helps track that.
/**
     * Writes to the buffer only occur after every 3 reads when encoding, an every 4 reads when decoding. This variable
     * helps track that.
     */
    private int modulus;

    
Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this Base64 object becomes useless,
and must be thrown away.
/**
     * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this Base64 object becomes useless,
     * and must be thrown away.
     */
    private boolean eof;

    
Place holder for the 3 bytes we're dealing with for our base64 logic. Bitwise operations store and extract the
base64 encoding or decoding from this variable.
/**
     * Place holder for the 3 bytes we're dealing with for our base64 logic. Bitwise operations store and extract the
     * base64 encoding or decoding from this variable.
     */
    private int x;

    
Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.


When decoding all variants are supported.

/**
     * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
     * <p>
     * When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.
     * </p>
     *
     * <p>
     * When decoding all variants are supported.
     * </p>
     */
    public Base64() {
        this(false);
    }

    
Creates a Base64 codec used for decoding (all modes) and encoding in the given URL-safe mode.

When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.


When decoding all variants are supported.

Params:
urlSafe – 
           if true, URL-safe encoding is used. In most cases this should be set to
           false.
Since:
1.4/**
     * Creates a Base64 codec used for decoding (all modes) and encoding in the given URL-safe mode.
     * <p>
     * When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.
     * </p>
     *
     * <p>
     * When decoding all variants are supported.
     * </p>
     *
     * @param urlSafe
     *            if <code>true</code>, URL-safe encoding is used. In most cases this should be set to
     *            <code>false</code>.
     * @since 1.4
     */
    public Base64(boolean urlSafe) {
        this(CHUNK_SIZE, CHUNK_SEPARATOR, urlSafe);
    }

    
Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

When encoding the line length is given in the constructor, the line separator is CRLF, and the encoding table is
STANDARD_ENCODE_TABLE.


Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.


When decoding all variants are supported.

Params:
lineLength –  Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
Since:
1.4/**
     * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
     * <p>
     * When encoding the line length is given in the constructor, the line separator is CRLF, and the encoding table is
     * STANDARD_ENCODE_TABLE.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
     * </p>
     * <p>
     * When decoding all variants are supported.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
     *            If {@code lineLength <= 0}, then the output will not be divided into lines (chunks). Ignored when decoding.
     * @since 1.4
     */
    public Base64(int lineLength) {
        this(lineLength, CHUNK_SEPARATOR);
    }

    
Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

When encoding the line length and line separator are given in the constructor, and the encoding table is
STANDARD_ENCODE_TABLE.


Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.


When decoding all variants are supported.

Params:
lineLength –  Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
lineSeparator – 
           Each line of encoded data will end with this sequence of bytes.
Throws:
IllegalArgumentException – 
            Thrown when the provided lineSeparator included some base64 characters.
Since:
1.4/**
     * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
     * <p>
     * When encoding the line length and line separator are given in the constructor, and the encoding table is
     * STANDARD_ENCODE_TABLE.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
     * </p>
     * <p>
     * When decoding all variants are supported.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
     *            If {@code lineLength <= 0}, then the output will not be divided into lines (chunks). Ignored when decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @throws IllegalArgumentException
     *             Thrown when the provided lineSeparator included some base64 characters.
     * @since 1.4
     */
    public Base64(int lineLength, byte[] lineSeparator) {
        this(lineLength, lineSeparator, false);
    }

    
Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

When encoding the line length and line separator are given in the constructor, and the encoding table is
STANDARD_ENCODE_TABLE.


Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.


When decoding all variants are supported.

Params:
lineLength –  Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
lineSeparator – 
           Each line of encoded data will end with this sequence of bytes.
urlSafe – 
           Instead of emitting '+' and '/' we emit '-' and '_' respectively. urlSafe is only applied to encode
           operations. Decoding seamlessly handles both modes.
Throws:
IllegalArgumentException – 
            The provided lineSeparator included some base64 characters. That's not going to work!
Since:
1.4/**
     * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
     * <p>
     * When encoding the line length and line separator are given in the constructor, and the encoding table is
     * STANDARD_ENCODE_TABLE.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
     * </p>
     * <p>
     * When decoding all variants are supported.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
     *            If {@code lineLength <= 0}, then the output will not be divided into lines (chunks). Ignored when decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @param urlSafe
     *            Instead of emitting '+' and '/' we emit '-' and '_' respectively. urlSafe is only applied to encode
     *            operations. Decoding seamlessly handles both modes.
     * @throws IllegalArgumentException
     *             The provided lineSeparator included some base64 characters. That's not going to work!
     * @since 1.4
     */
    public Base64(int lineLength, byte[] lineSeparator, boolean urlSafe) {
        if (lineSeparator == null) {
            lineLength = 0;  // disable chunk-separating
            lineSeparator = EMPTY_BYTE_ARRAY;  // this just gets ignored
        }
        this.lineLength = lineLength > 0 ? (lineLength / 4) * 4 : 0;
        this.lineSeparator = new byte[lineSeparator.length];
        System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
        if (lineLength > 0) {
            this.encodeSize = 4 + lineSeparator.length;
        } else {
            this.encodeSize = 4;
        }
        this.decodeSize = this.encodeSize - 1;
        if (containsBase64Byte(lineSeparator)) {
            String sep = newStringUtf8(lineSeparator);
            throw new IllegalArgumentException("lineSeperator must not contain base64 characters: [" + sep + "]");
        }
        this.encodeTable = urlSafe ? URL_SAFE_ENCODE_TABLE : STANDARD_ENCODE_TABLE;
    }

    
Returns our current encode mode. True if we're URL-SAFE, false otherwise.
Returns:
true if we're in URL-SAFE mode, false otherwise.
Since:
1.4/**
     * Returns our current encode mode. True if we're URL-SAFE, false otherwise.
     *
     * @return true if we're in URL-SAFE mode, false otherwise.
     * @since 1.4
     */
    public boolean isUrlSafe() {
        return this.encodeTable == URL_SAFE_ENCODE_TABLE;
    }

    
Returns true if this Base64 object has buffered data for reading.
Returns:
true if there is Base64 object still available for reading./**
     * Returns true if this Base64 object has buffered data for reading.
     *
     * @return true if there is Base64 object still available for reading.
     */
    boolean hasData() {
        return this.buffer != null;
    }

    
Returns the amount of buffered data available for reading.
Returns:
The amount of buffered data available for reading./**
     * Returns the amount of buffered data available for reading.
     *
     * @return The amount of buffered data available for reading.
     */
    int avail() {
        return buffer != null ? pos - readPos : 0;
    }

    
Doubles our buffer. /** Doubles our buffer. */
    private void resizeBuffer() {
        if (buffer == null) {
            buffer = new byte[DEFAULT_BUFFER_SIZE];
            pos = 0;
            readPos = 0;
        } else {
            byte[] b = new byte[buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
            System.arraycopy(buffer, 0, b, 0, buffer.length);
            buffer = b;
        }
    }

    
Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
bytes. Returns how many bytes were actually extracted.
Params:
b – 
           byte[] array to extract the buffered data into.
bPos – 
           position in byte[] array to start extraction at.
bAvail – 
           amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
Returns:
The number of bytes successfully extracted into the provided byte[] array./**
     * Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
     * bytes. Returns how many bytes were actually extracted.
     *
     * @param b
     *            byte[] array to extract the buffered data into.
     * @param bPos
     *            position in byte[] array to start extraction at.
     * @param bAvail
     *            amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
     * @return The number of bytes successfully extracted into the provided byte[] array.
     */
    int readResults(byte[] b, int bPos, int bAvail) {
        if (buffer != null) {
            int len = Math.min(avail(), bAvail);
            if (buffer != b) {
                System.arraycopy(buffer, readPos, b, bPos, len);
                readPos += len;
                if (readPos >= pos) {
                    buffer = null;
                }
            } else {
                // Re-using the original consumer's output array is only
                // allowed for one round.
                buffer = null;
            }
            return len;
        }
        return eof ? -1 : 0;
    }

    
Sets the streaming buffer. This is a small optimization where we try to buffer directly to the consumer's output
array for one round (if the consumer calls this method first) instead of starting our own buffer.
Params:
out – 
           byte[] array to buffer directly to.
outPos – 
           Position to start buffering into.
outAvail – 
           Amount of bytes available for direct buffering./**
     * Sets the streaming buffer. This is a small optimization where we try to buffer directly to the consumer's output
     * array for one round (if the consumer calls this method first) instead of starting our own buffer.
     *
     * @param out
     *            byte[] array to buffer directly to.
     * @param outPos
     *            Position to start buffering into.
     * @param outAvail
     *            Amount of bytes available for direct buffering.
     */
    void setInitialBuffer(byte[] out, int outPos, int outAvail) {
        // We can re-use consumer's original output array under
        // special circumstances, saving on some System.arraycopy().
        if (out != null && out.length == outAvail) {
            buffer = out;
            pos = outPos;
            readPos = outPos;
        }
    }

    

Encodes all of the provided data, starting at inPos, for inAvail bytes. Must be called at least twice: once with
the data to encode, and once with inAvail set to "-1" to alert encoder that EOF has been reached, so flush last
remaining bytes (if not multiple of 3).


Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/

Params:
in – 
           byte[] array of binary data to base64 encode.
inPos – 
           Position to start reading data from.
inAvail – 
           Amount of bytes available from input for encoding./**
     * <p>
     * Encodes all of the provided data, starting at inPos, for inAvail bytes. Must be called at least twice: once with
     * the data to encode, and once with inAvail set to "-1" to alert encoder that EOF has been reached, so flush last
     * remaining bytes (if not multiple of 3).
     * </p>
     * <p>
     * Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     * </p>
     *
     * @param in
     *            byte[] array of binary data to base64 encode.
     * @param inPos
     *            Position to start reading data from.
     * @param inAvail
     *            Amount of bytes available from input for encoding.
     */
    void encode(byte[] in, int inPos, int inAvail) {
        if (eof) {
            return;
        }
        // inAvail < 0 is how we're informed of EOF in the underlying data we're
        // encoding.
        if (inAvail < 0) {
            eof = true;
            if (buffer == null || buffer.length - pos < encodeSize) {
                resizeBuffer();
            }
            switch (modulus) {
                case 1 :
                    buffer[pos++] = encodeTable[(x >> 2) & MASK_6BITS];
                    buffer[pos++] = encodeTable[(x << 4) & MASK_6BITS];
                    // URL-SAFE skips the padding to further reduce size.
                    if (encodeTable == STANDARD_ENCODE_TABLE) {
                        buffer[pos++] = PAD;
                        buffer[pos++] = PAD;
                    }
                    break;

                case 2 :
                    buffer[pos++] = encodeTable[(x >> 10) & MASK_6BITS];
                    buffer[pos++] = encodeTable[(x >> 4) & MASK_6BITS];
                    buffer[pos++] = encodeTable[(x << 2) & MASK_6BITS];
                    // URL-SAFE skips the padding to further reduce size.
                    if (encodeTable == STANDARD_ENCODE_TABLE) {
                        buffer[pos++] = PAD;
                    }
                    break;
                default:
                    break;  // other values ignored
            }
            if (lineLength > 0 && pos > 0) {
                System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
                pos += lineSeparator.length;
            }
        } else {
            for (int i = 0; i < inAvail; i++) {
                if (buffer == null || buffer.length - pos < encodeSize) {
                    resizeBuffer();
                }
                modulus = (++modulus) % 3;
                int b = in[inPos++];
                if (b < 0) {
                    b += 256;
                }
                x = (x << 8) + b;
                if (0 == modulus) {
                    buffer[pos++] = encodeTable[(x >> 18) & MASK_6BITS];
                    buffer[pos++] = encodeTable[(x >> 12) & MASK_6BITS];
                    buffer[pos++] = encodeTable[(x >> 6) & MASK_6BITS];
                    buffer[pos++] = encodeTable[x & MASK_6BITS];
                    currentLinePos += 4;
                    if (lineLength > 0 && lineLength <= currentLinePos) {
                        System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
                        pos += lineSeparator.length;
                        currentLinePos = 0;
                    }
                }
            }
        }
    }

    

Decodes all of the provided data, starting at inPos, for inAvail bytes. Should be called at least twice: once
with the data to decode, and once with inAvail set to "-1" to alert decoder that EOF has been reached. The "-1"
call is not necessary when decoding, but it doesn't hurt, either.


Ignores all non-base64 characters. This is how chunked (e.g. 76 character) data is handled, since CR and LF are
silently ignored, but has implications for other bytes, too. This method subscribes to the garbage-in,
garbage-out philosophy: it will not check the provided data for validity.


Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/

Params:
in – 
           byte[] array of ascii data to base64 decode.
inPos – 
           Position to start reading data from.
inAvail – 
           Amount of bytes available from input for encoding./**
     * <p>
     * Decodes all of the provided data, starting at inPos, for inAvail bytes. Should be called at least twice: once
     * with the data to decode, and once with inAvail set to "-1" to alert decoder that EOF has been reached. The "-1"
     * call is not necessary when decoding, but it doesn't hurt, either.
     * </p>
     * <p>
     * Ignores all non-base64 characters. This is how chunked (e.g. 76 character) data is handled, since CR and LF are
     * silently ignored, but has implications for other bytes, too. This method subscribes to the garbage-in,
     * garbage-out philosophy: it will not check the provided data for validity.
     * </p>
     * <p>
     * Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     * </p>
     *
     * @param in
     *            byte[] array of ascii data to base64 decode.
     * @param inPos
     *            Position to start reading data from.
     * @param inAvail
     *            Amount of bytes available from input for encoding.
     */
    void decode(byte[] in, int inPos, int inAvail) {
        if (eof) {
            return;
        }
        if (inAvail < 0) {
            eof = true;
        }
        for (int i = 0; i < inAvail; i++) {
            if (buffer == null || buffer.length - pos < decodeSize) {
                resizeBuffer();
            }
            byte b = in[inPos++];
            if (b == PAD) {
                // We're done.
                eof = true;
                break;
            } else {
                if (b >= 0 && b < DECODE_TABLE.length) {
                    int result = DECODE_TABLE[b];
                    if (result >= 0) {
                        modulus = (++modulus) % 4;
                        x = (x << 6) + result;
                        if (modulus == 0) {
                            buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
                            buffer[pos++] = (byte) ((x >> 8) & MASK_8BITS);
                            buffer[pos++] = (byte) (x & MASK_8BITS);
                        }
                    }
                }
            }
        }

        // Two forms of EOF as far as base64 decoder is concerned: actual
        // EOF (-1) and first time '=' character is encountered in stream.
        // This approach makes the '=' padding characters completely optional.
        if (eof && modulus != 0) {
            x = x << 6;
            switch (modulus) {
                case 2 :
                    x = x << 6;
                    buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
                    break;
                case 3 :
                    buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
                    buffer[pos++] = (byte) ((x >> 8) & MASK_8BITS);
                    break;
                default:
                    break;  // other values ignored
            }
        }
    }

    
Returns whether or not the octet is in the base 64 alphabet.
Params:
octet – 
           The value to test
Returns:
true if the value is defined in the the base 64 alphabet, false otherwise.
Since:
1.4/**
     * Returns whether or not the <code>octet</code> is in the base 64 alphabet.
     *
     * @param octet
     *            The value to test
     * @return <code>true</code> if the value is defined in the the base 64 alphabet, <code>false</code> otherwise.
     * @since 1.4
     */
    public static boolean isBase64(byte octet) {
        return octet == PAD || (octet >= 0 && octet < DECODE_TABLE.length && DECODE_TABLE[octet] != -1);
    }

    
Tests a given byte array to see if it contains only valid characters within the Base64 alphabet. Currently the
method treats whitespace as valid.
Params:
arrayOctet – 
           byte array to test
Returns:
true if all bytes are valid characters in the Base64 alphabet or if the byte array is empty;
        false, otherwise/**
     * Tests a given byte array to see if it contains only valid characters within the Base64 alphabet. Currently the
     * method treats whitespace as valid.
     *
     * @param arrayOctet
     *            byte array to test
     * @return <code>true</code> if all bytes are valid characters in the Base64 alphabet or if the byte array is empty;
     *         false, otherwise
     */
    public static boolean isArrayByteBase64(byte[] arrayOctet) {
        for (int i = 0; i < arrayOctet.length; i++) {
            if (!isBase64(arrayOctet[i]) && !isWhiteSpace(arrayOctet[i])) {
                return false;
            }
        }
        return true;
    }

    
Tests a given byte array to see if it contains only valid characters within the Base64 alphabet.
Params:
arrayOctet – 
           byte array to test
Returns:
true if any byte is a valid character in the Base64 alphabet; false herwise/**
     * Tests a given byte array to see if it contains only valid characters within the Base64 alphabet.
     *
     * @param arrayOctet
     *            byte array to test
     * @return <code>true</code> if any byte is a valid character in the Base64 alphabet; false herwise
     */
    private static boolean containsBase64Byte(byte[] arrayOctet) {
        for (byte element : arrayOctet)
        {
            if (isBase64(element)) {
                return true;
            }
        }
        return false;
    }

    
Encodes binary data using the base64 algorithm but does not chunk the output.
Params:
binaryData – 
           binary data to encode
Returns:
byte[] containing Base64 characters in their UTF-8 representation./**
     * Encodes binary data using the base64 algorithm but does not chunk the output.
     *
     * @param binaryData
     *            binary data to encode
     * @return byte[] containing Base64 characters in their UTF-8 representation.
     */
    public static byte[] encodeBase64(byte[] binaryData) {
        return encodeBase64(binaryData, false);
    }

    
Encodes binary data using the base64 algorithm into 76 character blocks separated by CRLF.
 For a non-chunking version, see encodeBase64StringUnChunked(byte[]). 
Params:
binaryData – 
           binary data to encode
Returns:
String containing Base64 characters.
Since:
1.4/**
     * Encodes binary data using the base64 algorithm into 76 character blocks separated by CRLF.
     * <p>
     * For a non-chunking version, see {@link #encodeBase64StringUnChunked(byte[])}.
     *
     * @param binaryData
     *            binary data to encode
     * @return String containing Base64 characters.
     * @since 1.4
     */
    public static String encodeBase64String(byte[] binaryData) {
        return newStringUtf8(encodeBase64(binaryData, true));
    }

    
Encodes binary data using the base64 algorithm, without using chunking.
 For a chunking version, see encodeBase64String(byte[]). 
Params:
binaryData – 
           binary data to encode
Returns:
String containing Base64 characters.
Since:
3.2/**
     * Encodes binary data using the base64 algorithm, without using chunking.
     * <p>
     * For a chunking version, see {@link #encodeBase64String(byte[])}.
     *
     * @param binaryData
     *            binary data to encode
     * @return String containing Base64 characters.
     * @since 3.2
     */
    public static String encodeBase64StringUnChunked(byte[] binaryData) {
        return newStringUtf8(encodeBase64(binaryData, false));
    }

    
Encodes binary data using the base64 algorithm.
Params:
binaryData – 
           binary data to encode
useChunking – whether to split the output into chunks
Returns:
String containing Base64 characters.
Since:
3.2/**
     * Encodes binary data using the base64 algorithm.
     *
     * @param binaryData
     *            binary data to encode
     * @param useChunking whether to split the output into chunks
     * @return String containing Base64 characters.
     * @since 3.2
     */
    public static String encodeBase64String(byte[] binaryData, boolean useChunking) {
        return newStringUtf8(encodeBase64(binaryData, useChunking));
    }

    
Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output. The
url-safe variation emits - and _ instead of + and / characters.
Params:
binaryData – 
           binary data to encode
Returns:
byte[] containing Base64 characters in their UTF-8 representation.
Since:
1.4/**
     * Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output. The
     * url-safe variation emits - and _ instead of + and / characters.
     *
     * @param binaryData
     *            binary data to encode
     * @return byte[] containing Base64 characters in their UTF-8 representation.
     * @since 1.4
     */
    public static byte[] encodeBase64URLSafe(byte[] binaryData) {
        return encodeBase64(binaryData, false, true);
    }

    
Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output. The
url-safe variation emits - and _ instead of + and / characters.
Params:
binaryData – 
           binary data to encode
Returns:
String containing Base64 characters
Since:
1.4/**
     * Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output. The
     * url-safe variation emits - and _ instead of + and / characters.
     *
     * @param binaryData
     *            binary data to encode
     * @return String containing Base64 characters
     * @since 1.4
     */
    public static String encodeBase64URLSafeString(byte[] binaryData) {
        return newStringUtf8(encodeBase64(binaryData, false, true));
    }

    
Encodes binary data using the base64 algorithm and chunks the encoded output into 76 character blocks
Params:
binaryData – 
           binary data to encode
Returns:
Base64 characters chunked in 76 character blocks/**
     * Encodes binary data using the base64 algorithm and chunks the encoded output into 76 character blocks
     *
     * @param binaryData
     *            binary data to encode
     * @return Base64 characters chunked in 76 character blocks
     */
    public static byte[] encodeBase64Chunked(byte[] binaryData) {
        return encodeBase64(binaryData, true);
    }

    
Decodes a String containing containing characters in the Base64 alphabet.
Params:
pArray – 
           A String containing Base64 character data
Returns:
a byte array containing binary data
Since:
1.4/**
     * Decodes a String containing containing characters in the Base64 alphabet.
     *
     * @param pArray
     *            A String containing Base64 character data
     * @return a byte array containing binary data
     * @since 1.4
     */
    public byte[] decode(String pArray) {
        return decode(getBytesUtf8(pArray));
    }

    private byte[] getBytesUtf8(String pArray) {
        try {
            return pArray.getBytes("UTF8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
    }

    
Decodes a byte[] containing containing characters in the Base64 alphabet.
Params:
pArray – 
           A byte array containing Base64 character data
Returns:
a byte array containing binary data/**
     * Decodes a byte[] containing containing characters in the Base64 alphabet.
     *
     * @param pArray
     *            A byte array containing Base64 character data
     * @return a byte array containing binary data
     */
    public byte[] decode(byte[] pArray) {
        reset();
        if (pArray == null || pArray.length == 0) {
            return pArray;
        }
        long len = (pArray.length * 3) / 4;
        byte[] buf = new byte[(int) len];
        setInitialBuffer(buf, 0, buf.length);
        decode(pArray, 0, pArray.length);
        decode(pArray, 0, -1); // Notify decoder of EOF.

        // Would be nice to just return buf (like we sometimes do in the encode
        // logic), but we have no idea what the line-length was (could even be
        // variable).  So we cannot determine ahead of time exactly how big an
        // array is necessary.  Hence the need to construct a 2nd byte array to
        // hold the final result:

        byte[] result = new byte[pos];
        readResults(result, 0, result.length);
        return result;
    }

    
Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
Params:
binaryData – 
           Array containing binary data to encode.
isChunked – 
           if true this encoder will chunk the base64 output into 76 character blocks
Throws:
IllegalArgumentException –  Thrown when the input array needs an output array bigger than Integer.MAX_VALUE
Returns:
Base64-encoded data./**
     * Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
     *
     * @param binaryData
     *            Array containing binary data to encode.
     * @param isChunked
     *            if <code>true</code> this encoder will chunk the base64 output into 76 character blocks
     * @return Base64-encoded data.
     * @throws IllegalArgumentException
     *             Thrown when the input array needs an output array bigger than {@link Integer#MAX_VALUE}
     */
    public static byte[] encodeBase64(byte[] binaryData, boolean isChunked) {
        return encodeBase64(binaryData, isChunked, false);
    }

    
Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
Params:
binaryData – 
           Array containing binary data to encode.
isChunked – 
           if true this encoder will chunk the base64 output into 76 character blocks
urlSafe – 
           if true this encoder will emit - and _ instead of the usual + and / characters.
Throws:
IllegalArgumentException –  Thrown when the input array needs an output array bigger than Integer.MAX_VALUE
Returns:
Base64-encoded data.
Since:
1.4/**
     * Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
     *
     * @param binaryData
     *            Array containing binary data to encode.
     * @param isChunked
     *            if <code>true</code> this encoder will chunk the base64 output into 76 character blocks
     * @param urlSafe
     *            if <code>true</code> this encoder will emit - and _ instead of the usual + and / characters.
     * @return Base64-encoded data.
     * @throws IllegalArgumentException
     *             Thrown when the input array needs an output array bigger than {@link Integer#MAX_VALUE}
     * @since 1.4
     */
    public static byte[] encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe) {
        return encodeBase64(binaryData, isChunked, urlSafe, Integer.MAX_VALUE);
    }

    
Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
Params:
binaryData – 
           Array containing binary data to encode.
isChunked – 
           if true this encoder will chunk the base64 output into 76 character blocks
urlSafe – 
           if true this encoder will emit - and _ instead of the usual + and / characters.
maxResultSize – 
           The maximum result size to accept.
Throws:
IllegalArgumentException – 
            Thrown when the input array needs an output array bigger than maxResultSize
Returns:
Base64-encoded data.
Since:
1.4/**
     * Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
     *
     * @param binaryData
     *            Array containing binary data to encode.
     * @param isChunked
     *            if <code>true</code> this encoder will chunk the base64 output into 76 character blocks
     * @param urlSafe
     *            if <code>true</code> this encoder will emit - and _ instead of the usual + and / characters.
     * @param maxResultSize
     *            The maximum result size to accept.
     * @return Base64-encoded data.
     * @throws IllegalArgumentException
     *             Thrown when the input array needs an output array bigger than maxResultSize
     * @since 1.4
     */
    public static byte[] encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe, int maxResultSize) {
        if (binaryData == null || binaryData.length == 0) {
            return binaryData;
        }

        long len = getEncodeLength(binaryData, isChunked ? CHUNK_SIZE : 0, isChunked ? CHUNK_SEPARATOR : EMPTY_BYTE_ARRAY);
        if (len > maxResultSize) {
            throw new IllegalArgumentException("Input array too big, the output array would be bigger (" +
                len +
                ") than the specified maxium size of " +
                maxResultSize);
        }

        Base64 b64 = isChunked ? new Base64(urlSafe) : new Base64(0, CHUNK_SEPARATOR, urlSafe);
        return b64.encode(binaryData);
    }

    
Decodes a Base64 String into octets
Params:
base64String – 
           String containing Base64 data
Returns:
Array containing decoded data.
Since:
1.4/**
     * Decodes a Base64 String into octets
     *
     * @param base64String
     *            String containing Base64 data
     * @return Array containing decoded data.
     * @since 1.4
     */
    public static byte[] decodeBase64(String base64String) {
        return new Base64().decode(base64String);
    }

    
Decodes Base64 data into octets
Params:
base64Data – 
           Byte array containing Base64 data
Returns:
Array containing decoded data./**
     * Decodes Base64 data into octets
     *
     * @param base64Data
     *            Byte array containing Base64 data
     * @return Array containing decoded data.
     */
    public static byte[] decodeBase64(byte[] base64Data) {
        return new Base64().decode(base64Data);
    }



    
Checks if a byte value is whitespace or not.
Params:
byteToCheck – 
           the byte to check
Returns:
true if byte is whitespace, false otherwise/**
     * Checks if a byte value is whitespace or not.
     *
     * @param byteToCheck
     *            the byte to check
     * @return true if byte is whitespace, false otherwise
     */
    private static boolean isWhiteSpace(byte byteToCheck) {
        switch (byteToCheck) {
            case ' ' :
            case '\n' :
            case '\r' :
            case '\t' :
                return true;
            default :
                return false;
        }
    }

    
Encodes a byte[] containing binary data, into a String containing characters in the Base64 alphabet.
Params:
pArray – 
           a byte array containing binary data
Returns:
A String containing only Base64 character data
Since:
1.4/**
     * Encodes a byte[] containing binary data, into a String containing characters in the Base64 alphabet.
     *
     * @param pArray
     *            a byte array containing binary data
     * @return A String containing only Base64 character data
     * @since 1.4
     */
    public String encodeToString(byte[] pArray) {
        return newStringUtf8(encode(pArray));
    }

    private static String newStringUtf8(byte[] encode) {
        String str = null;
        try {
            str = new String(encode, "UTF8");
        } catch (UnsupportedEncodingException ue) {
            throw new RuntimeException(ue);
        }
        return str;
    }

    
Encodes a byte[] containing binary data, into a byte[] containing characters in the Base64 alphabet.
Params:
pArray – 
           a byte array containing binary data
Returns:
A byte array containing only Base64 character data/**
     * Encodes a byte[] containing binary data, into a byte[] containing characters in the Base64 alphabet.
     *
     * @param pArray
     *            a byte array containing binary data
     * @return A byte array containing only Base64 character data
     */
    public byte[] encode(byte[] pArray) {
        reset();
        if (pArray == null || pArray.length == 0) {
            return pArray;
        }
        long len = getEncodeLength(pArray, lineLength, lineSeparator);
        byte[] buf = new byte[(int) len];
        setInitialBuffer(buf, 0, buf.length);
        encode(pArray, 0, pArray.length);
        encode(pArray, 0, -1); // Notify encoder of EOF.
        // Encoder might have resized, even though it was unnecessary.
        if (buffer != buf) {
            readResults(buf, 0, buf.length);
        }
        // In URL-SAFE mode we skip the padding characters, so sometimes our
        // final length is a bit smaller.
        if (isUrlSafe() && pos < buf.length) {
            byte[] smallerBuf = new byte[pos];
            System.arraycopy(buf, 0, smallerBuf, 0, pos);
            buf = smallerBuf;
        }
        return buf;
    }

    
Pre-calculates the amount of space needed to base64-encode the supplied array.
Params:
pArray – byte[] array which will later be encoded
chunkSize – line-length of the output (<= 0 means no chunking) between each
       chunkSeparator (e.g. CRLF).
chunkSeparator – the sequence of bytes used to separate chunks of output (e.g. CRLF).
Returns:
amount of space needed to encoded the supplied array.  Returns
        a long since a max-len array will require Integer.MAX_VALUE + 33%./**
     * Pre-calculates the amount of space needed to base64-encode the supplied array.
     *
     * @param pArray byte[] array which will later be encoded
     * @param chunkSize line-length of the output (<= 0 means no chunking) between each
     *        chunkSeparator (e.g. CRLF).
     * @param chunkSeparator the sequence of bytes used to separate chunks of output (e.g. CRLF).
     *
     * @return amount of space needed to encoded the supplied array.  Returns
     *         a long since a max-len array will require Integer.MAX_VALUE + 33%.
     */
    private static long getEncodeLength(byte[] pArray, int chunkSize, byte[] chunkSeparator) {
        // base64 always encodes to multiples of 4.
        chunkSize = (chunkSize / 4) * 4;

        long len = (pArray.length * 4) / 3;
        long mod = len % 4;
        if (mod != 0) {
            len += 4 - mod;
        }
        if (chunkSize > 0) {
            boolean lenChunksPerfectly = len % chunkSize == 0;
            len += (len / chunkSize) * chunkSeparator.length;
            if (!lenChunksPerfectly) {
                len += chunkSeparator.length;
            }
        }
        return len;
    }

    // Implementation of integer encoding used for crypto
    
Decodes a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
Params:
pArray – 
           a byte array containing base64 character data
Returns:
A BigInteger
Since:
1.4/**
     * Decodes a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
     *
     * @param pArray
     *            a byte array containing base64 character data
     * @return A BigInteger
     * @since 1.4
     */
    public static BigInteger decodeInteger(byte[] pArray) {
        return new BigInteger(1, decodeBase64(pArray));
    }

    
Encodes to a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
Params:
bigInt – 
           a BigInteger
Throws:
NullPointerException – 
            if null is passed in
Returns:
A byte array containing base64 character data
Since:
1.4/**
     * Encodes to a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
     *
     * @param bigInt
     *            a BigInteger
     * @return A byte array containing base64 character data
     * @throws NullPointerException
     *             if null is passed in
     * @since 1.4
     */
    public static byte[] encodeInteger(BigInteger bigInt) {
        if (bigInt == null) {
            throw new NullPointerException("encodeInteger called with null parameter");
        }
        return encodeBase64(toIntegerBytes(bigInt), false);
    }

    
Returns a byte-array representation of a BigInteger without sign bit.
Params:
bigInt – 
           BigInteger to be converted
Returns:
a byte array representation of the BigInteger parameter/**
     * Returns a byte-array representation of a <code>BigInteger</code> without sign bit.
     *
     * @param bigInt
     *            <code>BigInteger</code> to be converted
     * @return a byte array representation of the BigInteger parameter
     */
    static byte[] toIntegerBytes(BigInteger bigInt) {
        int bitlen = bigInt.bitLength();
        // round bitlen
        bitlen = ((bitlen + 7) >> 3) << 3;
        byte[] bigBytes = bigInt.toByteArray();

        if (((bigInt.bitLength() % 8) != 0) && (((bigInt.bitLength() / 8) + 1) == (bitlen / 8))) {
            return bigBytes;
        }
        // set up params for copying everything but sign bit
        int startSrc = 0;
        int len = bigBytes.length;

        // if bigInt is exactly byte-aligned, just skip signbit in copy
        if ((bigInt.bitLength() % 8) == 0) {
            startSrc = 1;
            len--;
        }
        int startDst = bitlen / 8 - len; // to pad w/ nulls as per spec
        byte[] resizedBytes = new byte[bitlen / 8];
        System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, len);
        return resizedBytes;
    }

    
Resets this Base64 object to its initial newly constructed state.
/**
     * Resets this Base64 object to its initial newly constructed state.
     */
    private void reset() {
        buffer = null;
        pos = 0;
        readPos = 0;
        currentLinePos = 0;
        modulus = 0;
        eof = false;
    }

    // Getters for use in testing

    int getLineLength() {
        return lineLength;
    }

    byte[] getLineSeparator() {
        return lineSeparator.clone();
    }
}