/**
 * <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>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>
 * Change Log:
 * </p>
 * <ul>
 *  <li>v3.0.0 - Major cleanup by Danilo to remove unused code like GZIP
 *  or URL safe alphabets</li>
 *  <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>v2.3.5 - Fixed bug in {@link #encodeFromFile} where estimated buffer size
 *   was wrong for files of size 31, 34, and 37 bytes.</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
 *   {@link #decodeToObject(java.lang.String, int, java.lang.ClassLoader)}
 *   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 {@link #encodeBytesToBytes(byte[])} 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 possiblity 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 NullPointerExceptions and 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 3.0.0
 */
package ch.threema.client;

import java.nio.charset.StandardCharsets;
import java.util.Locale;

public class Base64 {
	/** The equals sign (=) as a byte. */
	private final static byte EQUALS_SIGN = (byte)'=';

	private final static byte WHITE_SPACE_ENC = -5; // Indicates white space in encoding
	private final static byte EQUALS_SIGN_ENC = -1; // Indicates equals sign in encoding

	/** The 64 valid Base64 values. */
	/* Host platform might be something funny like EBCDIC, so we hardcode these values. */
	private final static byte[] 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 final static byte[] 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
	};

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

	/**
	 * <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 accomodate <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
	 * @since 1.3
	 */
	private static void encode3to4(
		byte[] source,
		int srcOffset,
		int numSigBytes,
		byte[] destination,
		int destOffset
	) {
		//           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 ];
				break;
			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;
				break;
			case 1:
				destination[ destOffset     ] = ALPHABET[ (inBuff >>> 18)        ];
				destination[ destOffset + 1 ] = ALPHABET[ (inBuff >>> 12) & 0x3f ];
				destination[ destOffset + 2 ] = EQUALS_SIGN;
				destination[ destOffset + 3 ] = EQUALS_SIGN;
				break;
			default:
				break;
		}
	}

	/**
	 * Encodes a byte array into Base64 notation.
	 *
	 * @param source The data to convert
	 * @return The data in Base64-encoded form
	 * @throws NullPointerException if source array is null
	 * @since 1.4
	 */
	public static String encodeBytes(byte[] source) {
		return encodeBytes(source, 0, source.length);
	}

	/**
	 * Encodes a byte array into Base64 notation.
	 *
	 * @param source The data to convert
	 * @param off Offset in array where conversion should begin
	 * @param len Length of data to convert
	 * @return The Base64-encoded data as a String
	 * @throws NullPointerException if source array is null
	 * @throws IllegalArgumentException if source array, offset, or length are invalid
	 * @since 1.4
	 */
	private static String encodeBytes(byte[] source, int off, int len) {
		byte[] encoded = encodeBytesToBytes(source, off, len);
		return new String(encoded, StandardCharsets.US_ASCII);
	}

	/**
	 * Similar to {@link #encodeBytes(byte[], 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
	 * @return The Base64-encoded data as a String
	 * @throws NullPointerException if source array is null
	 * @throws IllegalArgumentException if source array, offset, or length are invalid
	 * @since 2.3.1
	 */
	private static byte[] encodeBytesToBytes(byte[] source, int off, int len) {
		if( source == null ){
			throw new NullPointerException( "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(Locale.US, "Cannot have offset of %d and length of %d with array of length %d", off,len,source.length));
		}   // end if: off < 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

		byte[] outBuff = new byte[ encLen ];


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

		if( d < len ) {
			encode3to4( source, d+off, len - d, outBuff, e );
			e += 4;
		}

		// 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);
			return finalOut;
		} else {
			return outBuff;
		}
	}

	/**
	 * 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 accomodate <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
	 * @return the number of decoded bytes converted
	 * @throws NullPointerException if source or destination arrays are null
	 * @throws IllegalArgumentException 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
	) {
		// Lots of error checking and exception throwing
		if( source == null ){
			throw new NullPointerException( "Source array was null." );
		}
		if( destination == null ){
			throw new NullPointerException( "Destination array was null." );
		}
		if( srcOffset < 0 || srcOffset + 3 >= source.length ){
			throw new IllegalArgumentException( String.format(Locale.US,
			"Source array with length %d cannot have offset of %d and still process four bytes.", source.length, srcOffset ) );
		}
		if( destOffset < 0 || destOffset +2 >= destination.length ){
			throw new IllegalArgumentException( String.format(Locale.US,
			"Destination array with length %d cannot have offset of %d and still store three bytes.", destination.length, destOffset ) );
		}

		// Example: Dk==
		if( source[ srcOffset + 2] == EQUALS_SIGN ) {
			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 ) {
			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 {
			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

	/**
	 * Low-level access to decoding ASCII characters in
	 * the form of a byte array. <strong>Ignores GUNZIP option, if
	 * it's set.</strong> This is not generally a recommended method,
	 * although it is used internally as part of the decoding process.
	 * Special case: if len = 0, an empty array is returned. Still,
	 * if you need more speed and reduced memory footprint, consider this method.
	 *
	 * @param source The Base64 encoded data
	 * @param off    The offset of where to begin decoding
	 * @param len    The length of characters to decode
	 * @return decoded data
	 * @throws java.io.IOException If bogus characters exist in source data
	 * @since 1.3
	 */
	private static byte[] decode(byte[] source, int off, int len) throws java.io.IOException {
		// Lots of error checking and exception throwing
		if( source == null ){
			throw new NullPointerException( "Cannot decode null source array." );
		}   // end if
		if( off < 0 || off + len > source.length ){
			throw new IllegalArgumentException( String.format(Locale.US,
			"Source array with length %d cannot have offset of %d and process %d bytes.", source.length, off, len ) );
		}

		if( len == 0 ){
			return new byte[0];
		}else if( len < 4 ){
			throw new IllegalArgumentException(
			"Base64-encoded string must have at least four characters, but length specified was " + len );
		}

		int    len34   = len * 3 / 4;       // Estimate on array size
		byte[] outBuff = new byte[ len34 ]; // Upper limit on size of output
		int    outBuffPosn = 0;             // Keep track of where we're writing

		byte[] b4        = new byte[4];     // Four byte buffer from source, eliminating white space
		int    b4Posn    = 0;               // Keep track of four byte input buffer

		for(int i = off; i < off+len; i++) {  // Loop through source
			int sbiDecode = DECODABET[ source[i]&0xFF ];

			// White space, Equals sign, or legit Base64 character
			// Note the values such as -5 and -9 in the
			// DECODABETs at the top of the file.
			if( sbiDecode >= WHITE_SPACE_ENC )  {
				if( sbiDecode >= EQUALS_SIGN_ENC ) {
					b4[ b4Posn++ ] = source[i];         // Save non-whitespace
					if( b4Posn > 3 ) {                  // Time to decode?
						outBuffPosn += decode4to3( b4, 0, outBuff, outBuffPosn);
						b4Posn = 0;

						// If that was the equals sign, break out of 'for' loop
						if( source[i] == EQUALS_SIGN ) {
							break;
						}
					}
				}
			}
			else {
				// There's a bad input character in the Base64 stream.
				throw new java.io.IOException( String.format(Locale.US,
				"Bad Base64 input character decimal %d in array position %d", ((int)source[i])&0xFF, i ) );
			}
		}

		byte[] out = new byte[ outBuffPosn ];
		System.arraycopy( outBuff, 0, out, 0, outBuffPosn );
		return out;
	}

	/**
	 * Decodes data from Base64 notation.
	 *
	 * @param s the string to decode
	 * @return the decoded data
	 * @throws java.io.IOException if there is an error
	 * @throws NullPointerException if <tt>s</tt> is null
	 * @since 1.4
	 */
	public static byte[] decode(String s) throws java.io.IOException {
		if(s == null){
			throw new NullPointerException("Input string was null.");
		}

		byte[] bytes = s.getBytes(StandardCharsets.US_ASCII);

		// Decode
		return decode(bytes, 0, bytes.length);
	}

}
