/*
 * Copyright (c) 2010-2020 Nathan Rajlich
 *
 *  Permission is hereby granted, free of charge, to any person
 *  obtaining a copy of this software and associated documentation
 *  files (the "Software"), to deal in the Software without
 *  restriction, including without limitation the rights to use,
 *  copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the
 *  Software is furnished to do so, subject to the following
 *  conditions:
 *
 *  The above copyright notice and this permission notice shall be
 *  included in all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *  OTHER DEALINGS IN THE SOFTWARE.
 */

package org.java_websocket.util;

/**
 * <p>Encodes and decodes to and from Base64 notation.</p>
 * <p>Homepage: <a href="http://iharder.net/base64">http://iharder.net/base64</a>.</p>
 *
 * <p>Example:</p>
 *
 * <code>String encoded = Base64.encode( myByteArray );</code>
 * <br>
 * <code>byte[] myByteArray = Base64.decode( encoded );</code>
 *
 * <p>The <tt>options</tt> parameter, which appears in a few places, is used to pass
 * several pieces of information to the encoder. In the "higher level" methods such as encodeBytes(
 * bytes, options ) the options parameter can be used to indicate such things as first gzipping the
 * bytes before encoding them, not inserting linefeeds, and encoding using the URL-safe and Ordered
 * dialects.</p>
 *
 * <p>Note, according to <a href="http://www.faqs.org/rfcs/rfc3548.html">RFC3548</a>,
 * Section 2.1, implementations should not add line feeds unless explicitly told to do so. I've got
 * Base64 set to this behavior now, although earlier versions broke lines by default.</p>
 *
 * <p>The constants defined in Base64 can be OR-ed together to combine options, so you
 * might make a call like this:</p>
 *
 * <code>String encoded = Base64.encodeBytes( mybytes, Base64.GZIP | Base64.DO_BREAK_LINES
 * );</code>
 * <p>to compress the data before encoding it and then making the output have newline
 * characters.</p>
 * <p>Also...</p>
 * <code>String encoded = Base64.encodeBytes( crazyString.getBytes() );</code>
 *
 *
 *
 * <p>
 * Change Log:
 * </p>
 * <ul>
 *  <li>v2.3.7 - Fixed subtle bug when base 64 input stream contained the
 *   value 01111111, which is an invalid base 64 character but should not
 *   throw an ArrayIndexOutOfBoundsException either. Led to discovery of
 *   mishandling (or potential for better handling) of other bad input
 *   characters. You should now get an IOException if you try decoding
 *   something that has bad characters in it.</li>
 *  <li>v2.3.6 - Fixed bug when breaking lines and the final byte of the encoded
 *   string ended in the last column; the buffer was not properly shrunk and
 *   contained an extra (null) byte that made it into the string.</li>
 *  <li>v2.3.4 - Fixed bug when working with gzipped streams whereby flushing
 *   the Base64.OutputStream closed the Base64 encoding (by padding with equals
 *   signs) too soon. Also added an option to suppress the automatic decoding
 *   of gzipped streams. Also added experimental support for specifying a
 *   class loader when using the method.</li>
 *  <li>v2.3.3 - Changed default char encoding to US-ASCII which reduces the internal Java
 *   footprint with its CharEncoders and so forth. Fixed some javadocs that were
 *   inconsistent. Removed imports and specified things like java.io.IOException
 *   explicitly inline.</li>
 *  <li>v2.3.2 - Reduced memory footprint! Finally refined the "guessing" of how big the
 *   final encoded data will be so that the code doesn't have to create two output
 *   arrays: an oversized initial one and then a final, exact-sized one. Big win
 *   when using the family of methods (and not
 *   using the gzip options which uses a different mechanism with streams and stuff).</li>
 *  <li>v2.3.1 - Added {@link #encodeBytesToBytes(byte[], int, int, int)} and some
 *   similar helper methods to be more efficient with memory by not returning a
 *   String but just a byte array.</li>
 *  <li>v2.3 - <strong>This is not a drop-in replacement!</strong> This is two years of comments
 *   and bug fixes queued up and finally executed. Thanks to everyone who sent
 *   me stuff, and I'm sorry I wasn't able to distribute your fixes to everyone else.
 *   Much bad coding was cleaned up including throwing exceptions where necessary
 *   instead of returning null values or something similar. Here are some changes
 *   that may affect you:
 *   <ul>
 *    <li><em>Does not break lines, by default.</em> This is to keep in compliance with
 *      <a href="http://www.faqs.org/rfcs/rfc3548.html">RFC3548</a>.</li>
 *    <li><em>Throws exceptions instead of returning null values.</em> Because some operations
 *      (especially those that may permit the GZIP option) use IO streams, there
 *      is a possibility of an java.io.IOException being thrown. After some discussion and
 *      thought, I've changed the behavior of the methods to throw java.io.IOExceptions
 *      rather than return null if ever there's an error. I think this is more
 *      appropriate, though it will require some changes to your code. Sorry,
 *      it should have been done this way to begin with.</li>
 *    <li><em>Removed all references to System.out, System.err, and the like.</em>
 *      Shame on me. All I can say is sorry they were ever there.</li>
 *    <li><em>Throws IllegalArgumentExceptions</em> as needed
 *      such as when passed arrays are null or offsets are invalid.</li>
 *    <li>Cleaned up as much javadoc as I could to avoid any javadoc warnings.
 *      This was especially annoying before for people who were thorough in their
 *      own projects and then had gobs of javadoc warnings on this file.</li>
 *   </ul>
 *  <li>v2.2.1 - Fixed bug using URL_SAFE and ORDERED encodings. Fixed bug
 *   when using very small files (~&lt; 40 bytes).</li>
 *  <li>v2.2 - Added some helper methods for encoding/decoding directly from
 *   one file to the next. Also added a main() method to support command line
 *   encoding/decoding from one file to the next. Also added these Base64 dialects:
 *   <ol>
 *   <li>The default is RFC3548 format.</li>
 *   <li>Calling Base64.setFormat(Base64.BASE64_FORMAT.URLSAFE_FORMAT) generates
 *   URL and file name friendly format as described in Section 4 of RFC3548.
 *   http://www.faqs.org/rfcs/rfc3548.html</li>
 *   <li>Calling Base64.setFormat(Base64.BASE64_FORMAT.ORDERED_FORMAT) generates
 *   URL and file name friendly format that preserves lexical ordering as described
 *   in http://www.faqs.org/qa/rfcc-1940.html</li>
 *   </ol>
 *   Special thanks to Jim Kellerman at <a href="http://www.powerset.com/">http://www.powerset.com/</a>
 *   for contributing the new Base64 dialects.
 *  </li>
 *
 *  <li>v2.1 - Cleaned up javadoc comments and unused variables and methods. Added
 *   some convenience methods for reading and writing to and from files.</li>
 *  <li>v2.0.2 - Now specifies UTF-8 encoding in places where the code fails on systems
 *   with other encodings (like EBCDIC).</li>
 *  <li>v2.0.1 - Fixed an error when decoding a single byte, that is, when the
 *   encoded data was a single byte.</li>
 *  <li>v2.0 - I got rid of methods that used booleans to set options.
 *   Now everything is more consolidated and cleaner. The code now detects
 *   when data that's being decoded is gzip-compressed and will decompress it
 *   automatically. Generally things are cleaner. You'll probably have to
 *   change some method calls that you were making to support the new
 *   options format (<tt>int</tt>s that you "OR" together).</li>
 *  <li>v1.5.1 - Fixed bug when decompressing and decoding to a
 *   byte[] using <tt>decode( String s, boolean gzipCompressed )</tt>.
 *   Added the ability to "suspend" encoding in the Output Stream so
 *   you can turn on and off the encoding if you need to embed base64
 *   data in an otherwise "normal" stream (like an XML file).</li>
 *  <li>v1.5 - Output stream pases on flush() command but doesn't do anything itself.
 *      This helps when using GZIP streams.
 *      Added the ability to GZip-compress objects before encoding them.</li>
 *  <li>v1.4 - Added helper methods to read/write files.</li>
 *  <li>v1.3.6 - Fixed OutputStream.flush() so that 'position' is reset.</li>
 *  <li>v1.3.5 - Added flag to turn on and off line breaks. Fixed bug in input stream
 *      where last buffer being read, if not completely full, was not returned.</li>
 *  <li>v1.3.4 - Fixed when "improperly padded stream" error was thrown at the wrong time.</li>
 *  <li>v1.3.3 - Fixed I/O streams which were totally messed up.</li>
 * </ul>
 *
 * <p>
 * I am placing this code in the Public Domain. Do with it as you will.
 * This software comes with no guarantees or warranties but with
 * plenty of well-wishing instead!
 * Please visit <a href="http://iharder.net/base64">http://iharder.net/base64</a>
 * periodically to check for updates or to contribute improvements.
 * </p>
 *
 * @author Robert Harder
 * @author rob@iharder.net
 * @version 2.3.7
 */
public class Base64 {

  /* ********  P U B L I C   F I E L D S  ******** */


  /**
   * No options specified. Value is zero.
   */
  public static final int NO_OPTIONS = 0;

  /**
   * Specify encoding in first bit. Value is one.
   */
  public static final int ENCODE = 1;

  /**
   * Specify that data should be gzip-compressed in second bit. Value is two.
   */
  public static final int GZIP = 2;

  /**
   * Do break lines when encoding. Value is 8.
   */
  public static final int DO_BREAK_LINES = 8;

  /**
   * Encode using Base64-like encoding that is URL- and Filename-safe as described in Section 4 of
   * RFC3548:
   * <a href="http://www.faqs.org/rfcs/rfc3548.html">http://www.faqs.org/rfcs/rfc3548.html</a>.
   * It is important to note that data encoded this way is <em>not</em> officially valid Base64, or
   * at the very least should not be called Base64 without also specifying that is was encoded using
   * the URL- and Filename-safe dialect.
   */
  public static final int URL_SAFE = 16;


  /**
   * Encode using the special "ordered" dialect of Base64 described here:
   * <a href="http://www.faqs.org/qa/rfcc-1940.html">http://www.faqs.org/qa/rfcc-1940.html</a>.
   */
  public static final int ORDERED = 32;


  /* ********  P R I V A T E   F I E L D S  ******** */


  /**
   * Maximum line length (76) of Base64 output.
   */
  private static final int MAX_LINE_LENGTH = 76;


  /**
   * The equals sign (=) as a byte.
   */
  private static final byte EQUALS_SIGN = (byte) '=';


  /**
   * The new line character (\n) as a byte.
   */
  private static final byte NEW_LINE = (byte) '\n';


  /**
   * Preferred encoding.
   */
  private static final String PREFERRED_ENCODING = "US-ASCII";


  private static final byte WHITE_SPACE_ENC = -5; // Indicates white space in encoding


  /* ********  S T A N D A R D   B A S E 6 4   A L P H A B E T  ******** */

  /**
   * The 64 valid Base64 values.
   */
  /* Host platform me be something funny like EBCDIC, so we hardcode these values. */
  private static final byte[] _STANDARD_ALPHABET = {
      (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
      (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
      (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
      (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
      (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
      (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
      (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
      (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
      (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5',
      (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '+', (byte) '/'
  };


  /**
   * Translates a Base64 value to either its 6-bit reconstruction value or a negative number
   * indicating some other meaning.
   **/
  private static final byte[] _STANDARD_DECODABET = {
      -9, -9, -9, -9, -9, -9, -9, -9, -9,                     // Decimal  0 -  8
      -5, -5,                                                 // Whitespace: Tab and Linefeed
      -9, -9,                                                 // Decimal 11 - 12
      -5,                                                     // Whitespace: Carriage Return
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 14 - 26
      -9, -9, -9, -9, -9,                                     // Decimal 27 - 31
      -5,                                                     // Whitespace: Space
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,                 // Decimal 33 - 42
      62,                                                     // Plus sign at decimal 43
      -9, -9, -9,                                             // Decimal 44 - 46
      63,                                                     // Slash at decimal 47
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61,                 // Numbers zero through nine
      -9, -9, -9,                                             // Decimal 58 - 60
      -1,                                                     // Equals sign at decimal 61
      -9, -9, -9,                                             // Decimal 62 - 64
      0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,           // Letters 'A' through 'N'
      14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,         // Letters 'O' through 'Z'
      -9, -9, -9, -9, -9, -9,                                 // Decimal 91 - 96
      26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,     // Letters 'a' through 'm'
      39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,     // Letters 'n' through 'z'
      -9, -9, -9, -9, -9,                                     // Decimal 123 - 127
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,         // Decimal 128 - 139
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 140 - 152
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 153 - 165
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 166 - 178
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 179 - 191
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 192 - 204
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 205 - 217
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 218 - 230
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 231 - 243
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9          // Decimal 244 - 255
  };


  /* ********  U R L   S A F E   B A S E 6 4   A L P H A B E T  ******** */

  /**
   * Used in the URL- and Filename-safe dialect described in Section 4 of RFC3548:
   * <a href="http://www.faqs.org/rfcs/rfc3548.html">http://www.faqs.org/rfcs/rfc3548.html</a>.
   * Notice that the last two bytes become "hyphen" and "underscore" instead of "plus" and "slash."
   */
  private static final byte[] _URL_SAFE_ALPHABET = {
      (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
      (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
      (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
      (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
      (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
      (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
      (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
      (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
      (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5',
      (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '-', (byte) '_'
  };

  /**
   * Used in decoding URL- and Filename-safe dialects of Base64.
   */
  private static final byte[] _URL_SAFE_DECODABET = {
      -9, -9, -9, -9, -9, -9, -9, -9, -9,                     // Decimal  0 -  8
      -5, -5,                                                 // Whitespace: Tab and Linefeed
      -9, -9,                                                 // Decimal 11 - 12
      -5,                                                     // Whitespace: Carriage Return
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 14 - 26
      -9, -9, -9, -9, -9,                                     // Decimal 27 - 31
      -5,                                                     // Whitespace: Space
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,                 // Decimal 33 - 42
      -9,                                                     // Plus sign at decimal 43
      -9,                                                     // Decimal 44
      62,                                                     // Minus sign at decimal 45
      -9,                                                     // Decimal 46
      -9,                                                     // Slash at decimal 47
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61,                 // Numbers zero through nine
      -9, -9, -9,                                             // Decimal 58 - 60
      -1,                                                     // Equals sign at decimal 61
      -9, -9, -9,                                             // Decimal 62 - 64
      0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,           // Letters 'A' through 'N'
      14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,         // Letters 'O' through 'Z'
      -9, -9, -9, -9,                                         // Decimal 91 - 94
      63,                                                     // Underscore at decimal 95
      -9,                                                     // Decimal 96
      26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,     // Letters 'a' through 'm'
      39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,     // Letters 'n' through 'z'
      -9, -9, -9, -9, -9,                                     // Decimal 123 - 127
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,         // Decimal 128 - 139
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 140 - 152
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 153 - 165
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 166 - 178
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 179 - 191
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 192 - 204
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 205 - 217
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 218 - 230
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 231 - 243
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9          // Decimal 244 - 255
  };



  /* ********  O R D E R E D   B A S E 6 4   A L P H A B E T  ******** */

  /**
   * I don't get the point of this technique, but someone requested it, and it is described here:
   * <a href="http://www.faqs.org/qa/rfcc-1940.html">http://www.faqs.org/qa/rfcc-1940.html</a>.
   */
  private static final byte[] _ORDERED_ALPHABET = {
      (byte) '-',
      (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4',
      (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9',
      (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
      (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
      (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
      (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
      (byte) '_',
      (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
      (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
      (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
      (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z'
  };

  /**
   * Used in decoding the "ordered" dialect of Base64.
   */
  private static final byte[] _ORDERED_DECODABET = {
      -9, -9, -9, -9, -9, -9, -9, -9, -9,                     // Decimal  0 -  8
      -5, -5,                                                 // Whitespace: Tab and Linefeed
      -9, -9,                                                 // Decimal 11 - 12
      -5,                                                     // Whitespace: Carriage Return
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 14 - 26
      -9, -9, -9, -9, -9,                                     // Decimal 27 - 31
      -5,                                                     // Whitespace: Space
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,                 // Decimal 33 - 42
      -9,                                                     // Plus sign at decimal 43
      -9,                                                     // Decimal 44
      0,                                                      // Minus sign at decimal 45
      -9,                                                     // Decimal 46
      -9,                                                     // Slash at decimal 47
      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,                          // Numbers zero through nine
      -9, -9, -9,                                             // Decimal 58 - 60
      -1,                                                     // Equals sign at decimal 61
      -9, -9, -9,                                             // Decimal 62 - 64
      11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,     // Letters 'A' through 'M'
      24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,     // Letters 'N' through 'Z'
      -9, -9, -9, -9,                                         // Decimal 91 - 94
      37,                                                     // Underscore at decimal 95
      -9,                                                     // Decimal 96
      38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,     // Letters 'a' through 'm'
      51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,     // Letters 'n' through 'z'
      -9, -9, -9, -9, -9,                                     // Decimal 123 - 127
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 128 - 139
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 140 - 152
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 153 - 165
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 166 - 178
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 179 - 191
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 192 - 204
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 205 - 217
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 218 - 230
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9,     // Decimal 231 - 243
      -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9          // Decimal 244 - 255
  };


  /* ********  D E T E R M I N E   W H I C H   A L H A B E T  ******** */


  /**
   * Returns one of the _SOMETHING_ALPHABET byte arrays depending on the options specified. It's
   * possible, though silly, to specify ORDERED <b>and</b> URLSAFE in which case one of them will be
   * picked, though there is no guarantee as to which one will be picked.
   */
  private static final byte[] getAlphabet(int options) {
    if ((options & URL_SAFE) == URL_SAFE) {
      return _URL_SAFE_ALPHABET;
    } else if ((options & ORDERED) == ORDERED) {
      return _ORDERED_ALPHABET;
    } else {
      return _STANDARD_ALPHABET;
    }
  }  // end getAlphabet


  /**
   * Returns one of the _SOMETHING_DECODABET byte arrays depending on the options specified. It's
   * possible, though silly, to specify ORDERED and URL_SAFE in which case one of them will be
   * picked, though there is no guarantee as to which one will be picked.
   */
  private static final byte[] getDecodabet(int options) {
    if ((options & URL_SAFE) == URL_SAFE) {
      return _URL_SAFE_DECODABET;
    } else if ((options & ORDERED) == ORDERED) {
      return _ORDERED_DECODABET;
    } else {
      return _STANDARD_DECODABET;
    }
  }  // end getAlphabet


  /**
   * Defeats instantiation.
   */
  private Base64() {
  }




  /* ********  E N C O D I N G   M E T H O D S  ******** */


  /**
   * Encodes up to the first three bytes of array <var>threeBytes</var> and returns a four-byte
   * array in Base64 notation. The actual number of significant bytes in your array is given by
   * <var>numSigBytes</var>. The array <var>threeBytes</var> needs only be as big as
   * <var>numSigBytes</var>.
   * Code can reuse a byte array by passing a four-byte array as <var>b4</var>.
   *
   * @param b4          A reusable byte array to reduce array instantiation
   * @param threeBytes  the array to convert
   * @param numSigBytes the number of significant bytes in your array
   * @return four byte array in Base64 notation.
   * @since 1.5.1
   */
  private static byte[] encode3to4(byte[] b4, byte[] threeBytes, int numSigBytes, int options) {
    encode3to4(threeBytes, 0, numSigBytes, b4, 0, options);
    return b4;
  }   // end encode3to4


  /**
   * <p>Encodes up to three bytes of the array <var>source</var>
   * and writes the resulting four Base64 bytes to <var>destination</var>. The source and
   * destination arrays can be manipulated anywhere along their length by specifying
   * <var>srcOffset</var> and <var>destOffset</var>.
   * This method does not check to make sure your arrays are large enough to accommodate
   * <var>srcOffset</var> + 3 for the <var>source</var> array or <var>destOffset</var> + 4 for the
   * <var>destination</var> array. The actual number of significant bytes in your array is given by
   * <var>numSigBytes</var>.</p>
   * <p>This is the lowest level of the encoding methods with
   * all possible parameters.</p>
   *
   * @param source      the array to convert
   * @param srcOffset   the index where conversion begins
   * @param numSigBytes the number of significant bytes in your array
   * @param destination the array to hold the conversion
   * @param destOffset  the index where output will be put
   * @return the <var>destination</var> array
   * @since 1.3
   */
  private static byte[] encode3to4(
      byte[] source, int srcOffset, int numSigBytes,
      byte[] destination, int destOffset, int options) {

    final byte[] ALPHABET = getAlphabet(options);

    //           1         2         3
    // 01234567890123456789012345678901 Bit position
    // --------000000001111111122222222 Array position from threeBytes
    // --------|    ||    ||    ||    | Six bit groups to index ALPHABET
    //          >>18  >>12  >> 6  >> 0  Right shift necessary
    //                0x3f  0x3f  0x3f  Additional AND

    // Create buffer with zero-padding if there are only one or two
    // significant bytes passed in the array.
    // We have to shift left 24 in order to flush out the 1's that appear
    // when Java treats a value as negative that is cast from a byte to an int.
    int inBuff = (numSigBytes > 0 ? ((source[srcOffset] << 24) >>> 8) : 0)
        | (numSigBytes > 1 ? ((source[srcOffset + 1] << 24) >>> 16) : 0)
        | (numSigBytes > 2 ? ((source[srcOffset + 2] << 24) >>> 24) : 0);

    switch (numSigBytes) {
      case 3:
        destination[destOffset] = ALPHABET[(inBuff >>> 18)];
        destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
        destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
        destination[destOffset + 3] = ALPHABET[(inBuff) & 0x3f];
        return destination;

      case 2:
        destination[destOffset] = ALPHABET[(inBuff >>> 18)];
        destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
        destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
        destination[destOffset + 3] = EQUALS_SIGN;
        return destination;

      case 1:
        destination[destOffset] = ALPHABET[(inBuff >>> 18)];
        destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
        destination[destOffset + 2] = EQUALS_SIGN;
        destination[destOffset + 3] = EQUALS_SIGN;
        return destination;

      default:
        return destination;
    }   // end switch
  }   // end encode3to4


  /**
   * Encodes a byte array into Base64 notation. Does not GZip-compress data.
   *
   * @param source The data to convert
   * @return The data in Base64-encoded form
   * @throws IllegalArgumentException if source array is null
   * @since 1.4
   */
  public static String encodeBytes(byte[] source) {
    // Since we're not going to have the GZIP encoding turned on,
    // we're not going to have an java.io.IOException thrown, so
    // we should not force the user to have to catch it.
    String encoded = null;
    try {
      encoded = encodeBytes(source, 0, source.length, NO_OPTIONS);
    } catch (java.io.IOException ex) {
      assert false : ex.getMessage();
    }   // end catch
    assert encoded != null;
    return encoded;
  }   // end encodeBytes


  /**
   * Encodes a byte array into Base64 notation.
   * <p>
   * Example options:<pre>
   *   GZIP: gzip-compresses object before encoding it.
   *   DO_BREAK_LINES: break lines at 76 characters
   *     <i>Note: Technically, this makes your encoding non-compliant.</i>
   * </pre>
   * <p>
   * Example: <code>encodeBytes( myData, Base64.GZIP )</code> or
   * <p>
   * Example: <code>encodeBytes( myData, Base64.GZIP | Base64.DO_BREAK_LINES )</code>
   *
   *
   * <p>As of v 2.3, if there is an error with the GZIP stream,
   * the method will throw an java.io.IOException. <b>This is new to v2.3!</b> In earlier versions,
   * it just returned a null value, but in retrospect that's a pretty poor way to handle it.</p>
   *
   * @param source  The data to convert
   * @param off     Offset in array where conversion should begin
   * @param len     Length of data to convert
   * @param options Specified options
   * @return The Base64-encoded data as a String
   * @throws java.io.IOException      if there is an error
   * @throws IllegalArgumentException if source array is null, if source array, offset, or length
   *                                  are invalid
   * @see Base64#GZIP
   * @see Base64#DO_BREAK_LINES
   * @since 2.0
   */
  public static String encodeBytes(byte[] source, int off, int len, int options)
      throws java.io.IOException {
    byte[] encoded = encodeBytesToBytes(source, off, len, options);

    // Return value according to relevant encoding.
    try {
      return new String(encoded, PREFERRED_ENCODING);
    } catch (java.io.UnsupportedEncodingException uue) {
      return new String(encoded);
    }   // end catch

  }   // end encodeBytes

  /**
   * Similar to {@link #encodeBytes(byte[], int, int, int)} but returns a byte array instead of
   * instantiating a String. This is more efficient if you're working with I/O streams and have
   * large data sets to encode.
   *
   * @param source  The data to convert
   * @param off     Offset in array where conversion should begin
   * @param len     Length of data to convert
   * @param options Specified options
   * @return The Base64-encoded data as a String
   * @throws java.io.IOException      if there is an error
   * @throws IllegalArgumentException if source array is null, if source array, offset, or length
   *                                  are invalid
   * @see Base64#GZIP
   * @see Base64#DO_BREAK_LINES
   * @since 2.3.1
   */
  public static byte[] encodeBytesToBytes(byte[] source, int off, int len, int options)
      throws java.io.IOException {

    if (source == null) {
      throw new IllegalArgumentException("Cannot serialize a null array.");
    }   // end if: null

    if (off < 0) {
      throw new IllegalArgumentException("Cannot have negative offset: " + off);
    }   // end if: off < 0

    if (len < 0) {
      throw new IllegalArgumentException("Cannot have length offset: " + len);
    }   // end if: len < 0

    if (off + len > source.length) {
      throw new IllegalArgumentException(
          String
              .format("Cannot have offset of %d and length of %d with array of length %d", off, len,
                  source.length));
    }   // end if: off < 0

    // Compress?
    if ((options & GZIP) != 0) {
      java.io.ByteArrayOutputStream baos = null;
      java.util.zip.GZIPOutputStream gzos = null;
      Base64.OutputStream b64os = null;

      try {
        // GZip -> Base64 -> ByteArray
        baos = new java.io.ByteArrayOutputStream();
        b64os = new Base64.OutputStream(baos, ENCODE | options);
        gzos = new java.util.zip.GZIPOutputStream(b64os);

        gzos.write(source, off, len);
        gzos.close();
      } catch (java.io.IOException e) {
        // Catch it and then throw it immediately so that
        // the finally{} block is called for cleanup.
        throw e;
      } finally {
        try {
          if (gzos != null) {
            gzos.close();
          }
        } catch (Exception e) {
          // do nothing
        }
        try {
          if (b64os != null) {
            b64os.close();
          }
        } catch (Exception e) {
          // do nothing
        }
        try {
          if (baos != null) {
            baos.close();
          }
        } catch (Exception e) {
          // do nothing
        }
      }   // end finally

      return baos.toByteArray();
    }   // end if: compress

    // Else, don't compress. Better not to use streams at all then.
    else {
      boolean breakLines = (options & DO_BREAK_LINES) != 0;

      //int    len43   = len * 4 / 3;
      //byte[] outBuff = new byte[   ( len43 )                      // Main 4:3
      //                           + ( (len % 3) > 0 ? 4 : 0 )      // Account for padding
      //                           + (breakLines ? ( len43 / MAX_LINE_LENGTH ) : 0) ]; // New lines

      // Try to determine more precisely how big the array needs to be.
      // If we get it right, we don't have to do an array copy, and
      // we save a bunch of memory.
      int encLen = (len / 3) * 4 + (len % 3 > 0 ? 4 : 0); // Bytes needed for actual encoding
      if (breakLines) {
        encLen += encLen / MAX_LINE_LENGTH; // Plus extra newline characters
      }
      byte[] outBuff = new byte[encLen];

      int d = 0;
      int e = 0;
      int len2 = len - 2;
      int lineLength = 0;
      for (; d < len2; d += 3, e += 4) {
        encode3to4(source, d + off, 3, outBuff, e, options);

        lineLength += 4;
        if (breakLines && lineLength >= MAX_LINE_LENGTH) {
          outBuff[e + 4] = NEW_LINE;
          e++;
          lineLength = 0;
        }   // end if: end of line
      }   // end for: each piece of array

      if (d < len) {
        encode3to4(source, d + off, len - d, outBuff, e, options);
        e += 4;
      }   // end if: some padding needed

      // Only resize array if we didn't guess it right.
      if (e <= outBuff.length - 1) {
        // If breaking lines and the last byte falls right at
        // the line length (76 bytes per line), there will be
        // one extra byte, and the array will need to be resized.
        // Not too bad of an estimate on array size, I'd say.
        byte[] finalOut = new byte[e];
        System.arraycopy(outBuff, 0, finalOut, 0, e);
        //System.err.println("Having to resize array from " + outBuff.length + " to " + e );
        return finalOut;
      } else {
        //System.err.println("No need to resize array.");
        return outBuff;
      }

    }   // end else: don't compress

  }   // end encodeBytesToBytes





  /* ********  D E C O D I N G   M E T H O D S  ******** */


  /**
   * Decodes four bytes from array <var>source</var> and writes the resulting bytes (up to three of
   * them) to <var>destination</var>. The source and destination arrays can be manipulated anywhere
   * along their length by specifying
   * <var>srcOffset</var> and <var>destOffset</var>.
   * This method does not check to make sure your arrays are large enough to accommodate
   * <var>srcOffset</var> + 4 for the <var>source</var> array or <var>destOffset</var> + 3 for the
   * <var>destination</var> array. This method returns the actual number of bytes that were
   * converted from the Base64 encoding.
   * <p>This is the lowest level of the decoding methods with
   * all possible parameters.</p>
   *
   * @param source      the array to convert
   * @param srcOffset   the index where conversion begins
   * @param destination the array to hold the conversion
   * @param destOffset  the index where output will be put
   * @param options     alphabet type is pulled from this (standard, url-safe, ordered)
   * @return the number of decoded bytes converted
   * @throws IllegalArgumentException if source or destination arrays are null, if srcOffset or
   *                                  destOffset are invalid or there is not enough room in the
   *                                  array.
   * @since 1.3
   */
  private static int decode4to3(
      byte[] source, int srcOffset,
      byte[] destination, int destOffset, int options) {

    // Lots of error checking and exception throwing
    if (source == null) {
      throw new IllegalArgumentException("Source array was null.");
    }   // end if
    if (destination == null) {
      throw new IllegalArgumentException("Destination array was null.");
    }   // end if
    if (srcOffset < 0 || srcOffset + 3 >= source.length) {
      throw new IllegalArgumentException(String.format(
          "Source array with length %d cannot have offset of %d and still process four bytes.",
          source.length, srcOffset));
    }   // end if
    if (destOffset < 0 || destOffset + 2 >= destination.length) {
      throw new IllegalArgumentException(String.format(
          "Destination array with length %d cannot have offset of %d and still store three bytes.",
          destination.length, destOffset));
    }   // end if

    final byte[] DECODABET = getDecodabet(options);

    // Example: Dk==
    if (source[srcOffset + 2] == EQUALS_SIGN) {
      // Two ways to do the same thing. Don't know which way I like best.
      //int outBuff =   ( ( DECODABET[ source[ srcOffset    ] ] << 24 ) >>>  6 )
      //              | ( ( DECODABET[ source[ srcOffset + 1] ] << 24 ) >>> 12 );
      int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
          | ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12);

      destination[destOffset] = (byte) (outBuff >>> 16);
      return 1;
    }

    // Example: DkL=
    else if (source[srcOffset + 3] == EQUALS_SIGN) {
      // Two ways to do the same thing. Don't know which way I like best.
      //int outBuff =   ( ( DECODABET[ source[ srcOffset     ] ] << 24 ) >>>  6 )
      //              | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
      //              | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 );
      int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
          | ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12)
          | ((DECODABET[source[srcOffset + 2]] & 0xFF) << 6);

      destination[destOffset] = (byte) (outBuff >>> 16);
      destination[destOffset + 1] = (byte) (outBuff >>> 8);
      return 2;
    }

    // Example: DkLE
    else {
      // Two ways to do the same thing. Don't know which way I like best.
      //int outBuff =   ( ( DECODABET[ source[ srcOffset     ] ] << 24 ) >>>  6 )
      //              | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
      //              | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 )
      //              | ( ( DECODABET[ source[ srcOffset + 3 ] ] << 24 ) >>> 24 );
      int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
          | ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12)
          | ((DECODABET[source[srcOffset + 2]] & 0xFF) << 6)
          | ((DECODABET[source[srcOffset + 3]] & 0xFF));

      destination[destOffset] = (byte) (outBuff >> 16);
      destination[destOffset + 1] = (byte) (outBuff >> 8);
      destination[destOffset + 2] = (byte) (outBuff);

      return 3;
    }
  }   // end decodeToBytes


  /**
   * A {@link Base64.OutputStream} will write data to another
   * <tt>java.io.OutputStream</tt>, given in the constructor,
   * and encode/decode to/from Base64 notation on the fly.
   *
   * @see Base64
   * @since 1.3
   */
  public static class OutputStream extends java.io.FilterOutputStream {

    private boolean encode;
    private int position;
    private byte[] buffer;
    private int bufferLength;
    private int lineLength;
    private boolean breakLines;
    private byte[] b4;         // Scratch used in a few places
    private boolean suspendEncoding;
    private int options;    // Record for later
    private byte[] decodabet;  // Local copies to avoid extra method calls

    /**
     * Constructs a {@link Base64.OutputStream} in ENCODE mode.
     *
     * @param out the <tt>java.io.OutputStream</tt> to which data will be written.
     * @since 1.3
     */
    public OutputStream(java.io.OutputStream out) {
      this(out, ENCODE);
    }   // end constructor


    /**
     * Constructs a {@link Base64.OutputStream} in either ENCODE or DECODE mode.
     * <p>
     * Valid options:<pre>
     *   ENCODE or DECODE: Encode or Decode as data is read.
     *   DO_BREAK_LINES: don't break lines at 76 characters
     *     <i>(only meaningful when encoding)</i>
     * </pre>
     * <p>
     * Example: <code>new Base64.OutputStream( out, Base64.ENCODE )</code>
     *
     * @param out     the <tt>java.io.OutputStream</tt> to which data will be written.
     * @param options Specified options.
     * @see Base64#ENCODE
     * @see Base64#DO_BREAK_LINES
     * @since 1.3
     */
    public OutputStream(java.io.OutputStream out, int options) {
      super(out);
      this.breakLines = (options & DO_BREAK_LINES) != 0;
      this.encode = (options & ENCODE) != 0;
      this.bufferLength = encode ? 3 : 4;
      this.buffer = new byte[bufferLength];
      this.position = 0;
      this.lineLength = 0;
      this.suspendEncoding = false;
      this.b4 = new byte[4];
      this.options = options;
      this.decodabet = getDecodabet(options);
    }   // end constructor


    /**
     * Writes the byte to the output stream after converting to/from Base64 notation. When encoding,
     * bytes are buffered three at a time before the output stream actually gets a write() call.
     * When decoding, bytes are buffered four at a time.
     *
     * @param theByte the byte to write
     * @since 1.3
     */
    @Override
    public void write(int theByte)
        throws java.io.IOException {
      // Encoding suspended?
      if (suspendEncoding) {
        this.out.write(theByte);
        return;
      }   // end if: suspended

      // Encode?
      if (encode) {
        buffer[position++] = (byte) theByte;
        if (position >= bufferLength) { // Enough to encode.

          this.out.write(encode3to4(b4, buffer, bufferLength, options));

          lineLength += 4;
          if (breakLines && lineLength >= MAX_LINE_LENGTH) {
            this.out.write(NEW_LINE);
            lineLength = 0;
          }   // end if: end of line

          position = 0;
        }   // end if: enough to output
      }   // end if: encoding

      // Else, Decoding
      else {
        // Meaningful Base64 character?
        if (decodabet[theByte & 0x7f] > WHITE_SPACE_ENC) {
          buffer[position++] = (byte) theByte;
          if (position >= bufferLength) { // Enough to output.

            int len = Base64.decode4to3(buffer, 0, b4, 0, options);
            out.write(b4, 0, len);
            position = 0;
          }   // end if: enough to output
        }   // end if: meaningful base64 character
        else if (decodabet[theByte & 0x7f] != WHITE_SPACE_ENC) {
          throw new java.io.IOException("Invalid character in Base64 data.");
        }   // end else: not white space either
      }   // end else: decoding
    }   // end write

    /**
     * Calls {@link #write(int)} repeatedly until <var>len</var> bytes are written.
     *
     * @param theBytes array from which to read bytes
     * @param off      offset for array
     * @param len      max number of bytes to read into array
     * @since 1.3
     */
    @Override
    public void write(byte[] theBytes, int off, int len)
        throws java.io.IOException {
      // Encoding suspended?
      if (suspendEncoding) {
        this.out.write(theBytes, off, len);
        return;
      }   // end if: suspended

      for (int i = 0; i < len; i++) {
        write(theBytes[off + i]);
      }   // end for: each byte written

    }   // end write

    /**
     * Method added by PHIL. [Thanks, PHIL. -Rob] This pads the buffer without closing the stream.
     *
     * @throws java.io.IOException if there's an error.
     */
    public void flushBase64() throws java.io.IOException {
      if (position > 0) {
        if (encode) {
          out.write(encode3to4(b4, buffer, position, options));
          position = 0;
        }   // end if: encoding
        else {
          throw new java.io.IOException("Base64 input not properly padded.");
        }   // end else: decoding
      }   // end if: buffer partially full

    }   // end flush

    /**
     * Flushes and closes (I think, in the superclass) the stream.
     *
     * @since 1.3
     */
    @Override
    public void close() throws java.io.IOException {
      // 1. Ensure that pending characters are written
      flushBase64();

      // 2. Actually close the stream
      // Base class both flushes and closes.
      super.close();

      buffer = null;
      out = null;
    }   // end close
  }   // end inner class OutputStream
}   // end class Base64
