/*
 * 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.tomcat.util.codec.binary;

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")


The URL-safe parameter is only applied to encode operations. Decoding only handles standard mode.


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).


This class is thread-safe.

See Also:
RFC 2045
Since:
1.0/**
 * Provides Base64 encoding and decoding as defined by <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>.
 *
 * <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:
 * </p>
 * <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>
 * The URL-safe parameter is only applied to encode operations. Decoding only handles standard mode.
 * </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>
 * This class is thread-safe.
 * </p>
 *
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
 * @since 1.0
 */
public class Base64 extends BaseNCodec {

    
BASE32 characters are 6 bits in length.
They are formed by taking a block of 3 octets to form a 24-bit string,
which is converted into 4 BASE64 characters.
/**
     * BASE32 characters are 6 bits in length.
     * They are formed by taking a block of 3 octets to form a 24-bit string,
     * which is converted into 4 BASE64 characters.
     */
    private static final int BITS_PER_ENCODED_BYTE = 6;
    private static final int BYTES_PER_UNENCODED_BLOCK = 3;
    private static final int BYTES_PER_ENCODED_BLOCK = 4;

    
Chunk separator per RFC 2045 section 2.1.

N.B. The next major release may break compatibility and make this field private.

See Also:
RFC 2045 section 2.1/**
     * Chunk separator per RFC 2045 section 2.1.
     *
     * <p>
     * N.B. The next major release may break compatibility and make this field private.
     * </p>
     *
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
     */
    static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};

    
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.
https://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.
     * https://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', '-', '_'
    };

    
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: The seamless decoding of URL safe values has been disabled because Tomcat doesn't use it.
Thanks to "commons" project in ws.apache.org for this code.
https://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: The seamless decoding of URL safe values has been disabled because Tomcat doesn't use it.
     *
     * Thanks to "commons" project in ws.apache.org for this code.
     * https://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     */
    private static final byte[] DECODE_TABLE = {
        //   0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, // 20-2f + /
            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, // 30-3f 0-9
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, // 40-4f A-O
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, // 50-5f P-Z
            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, // 60-6f a-o
            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51                      // 70-7a p-z
    };

    /**
     * Base64 uses 6-bit fields.
     */
    
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;

    // 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;

    // Only one decode table currently; keep for consistency with Base32 code
    private final byte[] decodeTable = DECODE_TABLE;

    
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 &gt; 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;

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

When encoding the line length is 0 (no chunking), 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 0 (no chunking), and the encoding table is STANDARD_ENCODE_TABLE.
     * </p>
     *
     * <p>
     * When decoding all variants are supported.
     * </p>
     */
    public Base64() {
        this(0);
    }

    
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(final boolean urlSafe) {
        this(MIME_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 lineLength &lt;= 0, then the output will not be divided into lines (chunks). Ignored when
     *            decoding.
     * @since 1.4
     */
    public Base64(final 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 lineLength &lt;= 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(final int lineLength, final 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 only handles standard mode.
           Note: no padding is added when using the URL-safe alphabet.
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 lineLength &lt;= 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 only handles standard mode.
     *            <b>Note: no padding is added when using the URL-safe alphabet.</b>
     * @throws IllegalArgumentException
     *             The provided lineSeparator included some base64 characters. That's not going to work!
     * @since 1.4
     */
    public Base64(final int lineLength, final byte[] lineSeparator, final boolean urlSafe) {
        super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK,
                lineLength,
                lineSeparator == null ? 0 : lineSeparator.length);
        // TODO could be simplified if there is no requirement to reject invalid line sep when length <=0
        // @see test case Base64Test.testConstructors()
        if (lineSeparator != null) {
            if (containsAlphabetOrPad(lineSeparator)) {
                final String sep = StringUtils.newStringUtf8(lineSeparator);
                throw new IllegalArgumentException(sm.getString("base64.lineSeparator", sep));
            }
            if (lineLength > 0){ // null line-sep forces no chunking rather than throwing IAE
                this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
                this.lineSeparator = new byte[lineSeparator.length];
                System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
            } else {
                this.encodeSize = BYTES_PER_ENCODED_BLOCK;
                this.lineSeparator = null;
            }
        } else {
            this.encodeSize = BYTES_PER_ENCODED_BLOCK;
            this.lineSeparator = null;
        }
        this.decodeSize = this.encodeSize - 1;
        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;
    }

    

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, to flush last
remaining bytes (if not multiple of 3).

Note: no padding is added when encoding using the URL-safe alphabet.

Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
https://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.
context – 
           the context to be used/**
     * <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, to flush last
     * remaining bytes (if not multiple of 3).
     * </p>
     * <p><b>Note: no padding is added when encoding using the URL-safe alphabet.</b></p>
     * <p>
     * Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
     * https://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.
     * @param context
     *            the context to be used
     */
    @Override
    void encode(final byte[] in, int inPos, final int inAvail, final Context context) {
        if (context.eof) {
            return;
        }
        // inAvail < 0 is how we're informed of EOF in the underlying data we're
        // encoding.
        if (inAvail < 0) {
            context.eof = true;
            if (0 == context.modulus && lineLength == 0) {
                return; // no leftovers to process and not using chunking
            }
            final byte[] buffer = ensureBufferSize(encodeSize, context);
            final int savedPos = context.pos;
            switch (context.modulus) { // 0-2
                case 0 : // nothing to do here
                    break;
                case 1 : // 8 bits = 6 + 2
                    // top 6 bits:
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 2) & MASK_6BITS];
                    // remaining 2:
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea << 4) & MASK_6BITS];
                    // URL-SAFE skips the padding to further reduce size.
                    if (encodeTable == STANDARD_ENCODE_TABLE) {
                        buffer[context.pos++] = pad;
                        buffer[context.pos++] = pad;
                    }
                    break;

                case 2 : // 16 bits = 6 + 6 + 4
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 10) & MASK_6BITS];
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 4) & MASK_6BITS];
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea << 2) & MASK_6BITS];
                    // URL-SAFE skips the padding to further reduce size.
                    if (encodeTable == STANDARD_ENCODE_TABLE) {
                        buffer[context.pos++] = pad;
                    }
                    break;
                default:
                    throw new IllegalStateException(sm.getString(
                            "base64.impossibleModulus", Integer.valueOf(context.modulus)));
            }
            context.currentLinePos += context.pos - savedPos; // keep track of current line position
            // if currentPos == 0 we are at the start of a line, so don't add CRLF
            if (lineLength > 0 && context.currentLinePos > 0) {
                System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
                context.pos += lineSeparator.length;
            }
        } else {
            for (int i = 0; i < inAvail; i++) {
                final byte[] buffer = ensureBufferSize(encodeSize, context);
                context.modulus = (context.modulus+1) % BYTES_PER_UNENCODED_BLOCK;
                int b = in[inPos++];
                if (b < 0) {
                    b += 256;
                }
                context.ibitWorkArea = (context.ibitWorkArea << 8) + b; //  BITS_PER_BYTE
                if (0 == context.modulus) { // 3 bytes = 24 bits = 4 * 6 bits to extract
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 18) & MASK_6BITS];
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 12) & MASK_6BITS];
                    buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 6) & MASK_6BITS];
                    buffer[context.pos++] = encodeTable[context.ibitWorkArea & MASK_6BITS];
                    context.currentLinePos += BYTES_PER_ENCODED_BLOCK;
                    if (lineLength > 0 && lineLength <= context.currentLinePos) {
                        System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
                        context.pos += lineSeparator.length;
                        context.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.
https://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 decoding.
context – 
           the context to be used/**
     * <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.
     * https://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 decoding.
     * @param context
     *            the context to be used
     */
    @Override
    void decode(final byte[] in, int inPos, final int inAvail, final Context context) {
        if (context.eof) {
            return;
        }
        if (inAvail < 0) {
            context.eof = true;
        }
        for (int i = 0; i < inAvail; i++) {
            final byte[] buffer = ensureBufferSize(decodeSize, context);
            final byte b = in[inPos++];
            if (b == pad) {
                // We're done.
                context.eof = true;
                break;
            }
            if (b >= 0 && b < DECODE_TABLE.length) {
                final int result = DECODE_TABLE[b];
                if (result >= 0) {
                    context.modulus = (context.modulus+1) % BYTES_PER_ENCODED_BLOCK;
                    context.ibitWorkArea = (context.ibitWorkArea << BITS_PER_ENCODED_BYTE) + result;
                    if (context.modulus == 0) {
                        buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 16) & MASK_8BITS);
                        buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
                        buffer[context.pos++] = (byte) (context.ibitWorkArea & 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 (context.eof && context.modulus != 0) {
            final byte[] buffer = ensureBufferSize(decodeSize, context);

            // We have some spare bits remaining
            // Output all whole multiples of 8 bits and ignore the rest
            switch (context.modulus) {
//              case 0 : // impossible, as excluded above
                case 1 : // 6 bits - ignore entirely
                    // TODO not currently tested; perhaps it is impossible?
                    break;
                case 2 : // 12 bits = 8 + 4
                    validateCharacter(4, context);
                    context.ibitWorkArea = context.ibitWorkArea >> 4; // dump the extra 4 bits
                    buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
                    break;
                case 3 : // 18 bits = 8 + 8 + 2
                    validateCharacter(2, context);
                    context.ibitWorkArea = context.ibitWorkArea >> 2; // dump 2 bits
                    buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
                    break;
                default:
                    throw new IllegalStateException(sm.getString(
                            "base64.impossibleModulus", Integer.valueOf(context.modulus)));
            }
        }
    }

    
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(final byte octet) {
        return octet == PAD_DEFAULT || (octet >= 0 && octet < DECODE_TABLE.length && DECODE_TABLE[octet] != -1);
    }

    
Tests a given String to see if it contains only valid characters within the Base64 alphabet. Currently the
method treats whitespace as valid.
Params:
base64 – 
           String to test
Returns:
true if all characters in the String are valid characters in the Base64 alphabet or if
        the String is empty; false, otherwise
 @since 1.5/**
     * Tests a given String to see if it contains only valid characters within the Base64 alphabet. Currently the
     * method treats whitespace as valid.
     *
     * @param base64
     *            String to test
     * @return <code>true</code> if all characters in the String are valid characters in the Base64 alphabet or if
     *         the String is empty; <code>false</code>, otherwise
     *  @since 1.5
     */
    public static boolean isBase64(final String base64) {
        return isBase64(StringUtils.getBytesUtf8(base64));
    }

    
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
Since:
1.5/**
     * 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;
     *         <code>false</code>, otherwise
     * @since 1.5
     */
    public static boolean isBase64(final byte[] arrayOctet) {
        for (int i = 0; i < arrayOctet.length; i++) {
            if (!isBase64(arrayOctet[i]) && !isWhiteSpace(arrayOctet[i])) {
                return false;
            }
        }
        return true;
    }

    
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(final byte[] binaryData) {
        return encodeBase64(binaryData, false);
    }

    
Encodes binary data using the base64 algorithm but does not chunk the output.
NOTE:  We changed the behaviour of this method from multi-line chunking (commons-codec-1.4) to
single-line non-chunking (commons-codec-1.5).
Params:
binaryData – 
           binary data to encode
Returns:
String containing Base64 characters.
Since:
1.4 (NOTE:  1.4 chunked the output, whereas 1.5 does not)./**
     * Encodes binary data using the base64 algorithm but does not chunk the output.
     *
     * NOTE:  We changed the behaviour of this method from multi-line chunking (commons-codec-1.4) to
     * single-line non-chunking (commons-codec-1.5).
     *
     * @param binaryData
     *            binary data to encode
     * @return String containing Base64 characters.
     * @since 1.4 (NOTE:  1.4 chunked the output, whereas 1.5 does not).
     */
    public static String encodeBase64String(final byte[] binaryData) {
        return StringUtils.newStringUsAscii(encodeBase64(binaryData, false));
    }

    
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.
Note: no padding is added.
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.
     * <b>Note: no padding is added.</b>
     * @param binaryData
     *            binary data to encode
     * @return byte[] containing Base64 characters in their UTF-8 representation.
     * @since 1.4
     */
    public static byte[] encodeBase64URLSafe(final 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.
Note: no padding is added.
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.
     * <b>Note: no padding is added.</b>
     * @param binaryData
     *            binary data to encode
     * @return String containing Base64 characters
     * @since 1.4
     */
    public static String encodeBase64URLSafeString(final byte[] binaryData) {
        return StringUtils.newStringUsAscii(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(final byte[] binaryData) {
        return encodeBase64(binaryData, true);
    }

    
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(final byte[] binaryData, final 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.
           Note: no padding is added when encoding using the URL-safe alphabet.
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.
     *            <b>Note: no padding is added when encoding using the URL-safe alphabet.</b>
     * @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(final byte[] binaryData, final boolean isChunked, final 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.
           Note: no padding is added when encoding using the URL-safe alphabet.
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.
     *            <b>Note: no padding is added when encoding using the URL-safe alphabet.</b>
     * @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(final byte[] binaryData, final boolean isChunked,
                                      final boolean urlSafe, final int maxResultSize) {
        if (binaryData == null || binaryData.length == 0) {
            return binaryData;
        }

        // Create this so can use the super-class method
        // Also ensures that the same roundings are performed by the ctor and the code
        final Base64 b64 = isChunked ? new Base64(urlSafe) : new Base64(0, CHUNK_SEPARATOR, urlSafe);
        final long len = b64.getEncodedLength(binaryData);
        if (len > maxResultSize) {
            throw new IllegalArgumentException(sm.getString(
                    "base64.inputTooLarge", Long.valueOf(len), Integer.valueOf(maxResultSize)));
        }

        return b64.encode(binaryData);
    }

    
Decodes a Base64 String into octets.

Note: this method only handles data encoded in standard mode.

Params:
base64String – 
           String containing Base64 data
Returns:
Array containing decoded data.
Since:
1.4/**
     * Decodes a Base64 String into octets.
     * <p>
     * <b>Note:</b> this method only handles data encoded in standard mode.
     * </p>
     *
     * @param base64String
     *            String containing Base64 data
     * @return Array containing decoded data.
     * @since 1.4
     */
    public static byte[] decodeBase64(final String base64String) {
        return new Base64().decode(base64String);
    }

    
Decodes Base64 data into octets.

Note: this method only handles data encoded in standard mode.

Params:
base64Data – 
           Byte array containing Base64 data
Returns:
Array containing decoded data./**
     * Decodes Base64 data into octets.
     * <p>
     * <b>Note:</b> this method only handles data encoded in standard mode.
     * </p>
     *
     * @param base64Data
     *            Byte array containing Base64 data
     * @return Array containing decoded data.
     */
    public static byte[] decodeBase64(final byte[] base64Data) {
        return decodeBase64(base64Data, 0, base64Data.length);
    }

    public  static byte[] decodeBase64(
            final byte[] base64Data, final int off, final int len) {
        return new Base64().decode(base64Data, off, len);
    }

    // Implementation of the Encoder Interface

    // 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(final 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(final BigInteger bigInt) {
        if (bigInt == null) {
            throw new NullPointerException(sm.getString("base64.nullEncodeParameter"));
        }
        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(final BigInteger bigInt) {
        int bitlen = bigInt.bitLength();
        // round bitlen
        bitlen = ((bitlen + 7) >> 3) << 3;
        final 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--;
        }
        final int startDst = bitlen / 8 - len; // to pad w/ nulls as per spec
        final byte[] resizedBytes = new byte[bitlen / 8];
        System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, len);
        return resizedBytes;
    }

    
Returns whether or not the octet is in the Base64 alphabet.
Params:
octet – 
           The value to test
Returns:
true if the value is defined in the the Base64 alphabet false otherwise./**
     * Returns whether or not the <code>octet</code> is in the Base64 alphabet.
     *
     * @param octet
     *            The value to test
     * @return <code>true</code> if the value is defined in the the Base64 alphabet <code>false</code> otherwise.
     */
    @Override
    protected boolean isInAlphabet(final byte octet) {
        return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
    }


    

Validates whether the character is possible in the context of the set of possible base 64 values.

Params:
numBitsToDrop – number of least significant bits to check
context – the context to be used
Throws:
IllegalArgumentException – if the bits being checked contain any non-zero value/**
     * <p>
     * Validates whether the character is possible in the context of the set of possible base 64 values.
     * </p>
     *
     * @param numBitsToDrop number of least significant bits to check
     * @param context the context to be used
     *
     * @throws IllegalArgumentException if the bits being checked contain any non-zero value
     */
    private long validateCharacter(final int numBitsToDrop, final Context context) {
        if ((context.ibitWorkArea & numBitsToDrop) != 0) {
        throw new IllegalArgumentException(
            "Last encoded character (before the paddings if any) is a valid base 64 alphabet but not a possible value");
        }
        return context.ibitWorkArea >> numBitsToDrop;
    }
}