1 package com.isode.stroke.stringcodecs;

     2 

     3 import java.util.Arrays;

     4 

     5 /** A very fast and memory efficient class to encode and decode to and from BASE64 in full accordance

     6  * with RFC 2045.<br><br>

     7  * On Windows XP sp1 with 1.4.2_04 and later ;), this encoder and decoder is about 10 times faster

     8  * on small arrays (10 - 1000 bytes) and 2-3 times as fast on larger arrays (10000 - 1000000 bytes)

     9  * compared to <code>sun.misc.Encoder()/Decoder()</code>.<br><br>

    10  *

    11  * On byte arrays the encoder is about 20% faster than Jakarta Commons Base64 Codec for encode and

    12  * about 50% faster for decoding large arrays. This implementation is about twice as fast on very small

    13  * arrays (&lt 30 bytes). If source/destination is a <code>String</code> this

    14  * version is about three times as fast due to the fact that the Commons Codec result has to be recoded

    15  * to a <code>String</code> from <code>byte[]</code>, which is very expensive.<br><br>

    16  *

    17  * This encode/decode algorithm doesn't create any temporary arrays as many other codecs do, it only

    18  * allocates the resulting array. This produces less garbage and it is possible to handle arrays twice

    19  * as large as algorithms that create a temporary array. (E.g. Jakarta Commons Codec). It is unknown

    20  * whether Sun's <code>sun.misc.Encoder()/Decoder()</code> produce temporary arrays but since performance

    21  * is quite low it probably does.<br><br>

    22  *

    23  * The encoder produces the same output as the Sun one except that the Sun's encoder appends

    24  * a trailing line separator if the last character isn't a pad. Unclear why but it only adds to the

    25  * length and is probably a side effect. Both are in conformance with RFC 2045 though.<br>

    26  * Commons codec seem to always att a trailing line separator.<br><br>

    27  *

    28  * <b>Note!</b>

    29  * The encode/decode method pairs (types) come in three versions with the <b>exact</b> same algorithm and

    30  * thus a lot of code redundancy. This is to not create any temporary arrays for transcoding to/from different

    31  * format types. The methods not used can simply be commented out.<br><br>

    32  *

    33  * There is also a "fast" version of all decode methods that works the same way as the normal ones, but

    34  * har a few demands on the decoded input. Normally though, these fast verions should be used if the source if

    35  * the input is known and it hasn't bee tampered with.<br><br>

    36  *

    37  * If you find the code useful or you find a bug, please send me a note at base64 @ miginfocom . com.

    38  *

    39  * Licence (BSD):

    40  * ==============

    41  *

    42  * Copyright (c) 2004, Mikael Grev, MiG InfoCom AB. (base64 @ miginfocom . com)

    43  * All rights reserved.

    44  *

    45  * Redistribution and use in source and binary forms, with or without modification,

    46  * are permitted provided that the following conditions are met:

    47  * Redistributions of source code must retain the above copyright notice, this list

    48  * of conditions and the following disclaimer.

    49  * Redistributions in binary form must reproduce the above copyright notice, this

    50  * list of conditions and the following disclaimer in the documentation and/or other

    51  * materials provided with the distribution.

    52  * Neither the name of the MiG InfoCom AB nor the names of its contributors may be

    53  * used to endorse or promote products derived from this software without specific

    54  * prior written permission.

    55  *

    56  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

    57  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

    58  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

    59  * IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

    60  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,

    61  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,

    62  * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

    63  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

    64  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY

    65  * OF SUCH DAMAGE.

    66  *

    67  * @version 2.2

    68  * @author Mikael Grev

    69  *         Date: 2004-aug-02

    70  *         Time: 11:31:11

    71  */

    72 

    73 public class Base64BSD

    74 {

    75 	private static final char[] CA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

    76 	private static final int[] IA = new int[256];

    77 	static {

    78 		Arrays.fill(IA, -1);

    79 		for (int i = 0, iS = CA.length; i < iS; i++)

    80 			IA[CA[i]] = i;

    81 		IA['='] = 0;

    82 	}

    83 

    84 	// ****************************************************************************************

    85 	// *  char[] version

    86 	// ****************************************************************************************

    87 

    88 	/** Encodes a raw byte array into a BASE64 <code>char[]</code> representation i accordance with RFC 2045.

    89 	 * @param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.

    90 	 * @param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>

    91 	 * No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a

    92 	 * little faster.

    93 	 * @return A BASE64 encoded array. Never <code>null</code>.

    94 	 */

    95 	public final static char[] encodeToChar(byte[] sArr, boolean lineSep)

    96 	{

    97 		// Check special case

    98 		int sLen = sArr != null ? sArr.length : 0;

    99 		if (sLen == 0)

   100 			return new char[0];

   101 

   102 		int eLen = (sLen / 3) * 3;              // Length of even 24-bits.

   103 		int cCnt = ((sLen - 1) / 3 + 1) << 2;   // Returned character count

   104 		int dLen = cCnt + (lineSep ? (cCnt - 1) / 76 << 1 : 0); // Length of returned array

   105 		char[] dArr = new char[dLen];

   106 

   107 		// Encode even 24-bits

   108 		for (int s = 0, d = 0, cc = 0; s < eLen;) {

   109 			// Copy next three bytes into lower 24 bits of int, paying attension to sign.

   110 			int i = (sArr[s++] & 0xff) << 16 | (sArr[s++] & 0xff) << 8 | (sArr[s++] & 0xff);

   111 

   112 			// Encode the int into four chars

   113 			dArr[d++] = CA[(i >>> 18) & 0x3f];

   114 			dArr[d++] = CA[(i >>> 12) & 0x3f];

   115 			dArr[d++] = CA[(i >>> 6) & 0x3f];

   116 			dArr[d++] = CA[i & 0x3f];

   117 

   118 			// Add optional line separator

   119 			if (lineSep && ++cc == 19 && d < dLen - 2) {

   120 				dArr[d++] = '\r';

   121 				dArr[d++] = '\n';

   122 				cc = 0;

   123 			}

   124 		}

   125 

   126 		// Pad and encode last bits if source isn't even 24 bits.

   127 		int left = sLen - eLen; // 0 - 2.

   128 		if (left > 0) {

   129 			// Prepare the int

   130 			int i = ((sArr[eLen] & 0xff) << 10) | (left == 2 ? ((sArr[sLen - 1] & 0xff) << 2) : 0);

   131 

   132 			// Set last four chars

   133 			dArr[dLen - 4] = CA[i >> 12];

   134 			dArr[dLen - 3] = CA[(i >>> 6) & 0x3f];

   135 			dArr[dLen - 2] = left == 2 ? CA[i & 0x3f] : '=';

   136 			dArr[dLen - 1] = '=';

   137 		}

   138 		return dArr;

   139 	}

   140 

   141 	/** Decodes a BASE64 encoded char array. All illegal characters will be ignored and can handle both arrays with

   142 	 * and without line separators.

   143 	 * @param sArr The source array. <code>null</code> or length 0 will return an empty array.

   144 	 * @return The decoded array of bytes. May be of length 0. Will be <code>null</code> if the legal characters

   145 	 * (including '=') isn't divideable by 4.  (I.e. definitely corrupted).

   146 	 */

   147 	public final static byte[] decode(char[] sArr)

   148 	{

   149 		// Check special case

   150 		int sLen = sArr != null ? sArr.length : 0;

   151 		if (sLen == 0)

   152 			return new byte[0];

   153 

   154 		// Count illegal characters (including '\r', '\n') to know what size the returned array will be,

   155 		// so we don't have to reallocate & copy it later.

   156 		int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)

   157 		for (int i = 0; i < sLen; i++)  // If input is "pure" (I.e. no line separators or illegal chars) base64 this loop can be commented out.

   158 			if (IA[sArr[i]] < 0)

   159 				sepCnt++;

   160 

   161 		// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.

   162 		if ((sLen - sepCnt) % 4 != 0)

   163 			return null;

   164 

   165 		int pad = 0;

   166 		for (int i = sLen; i > 1 && IA[sArr[--i]] <= 0;)

   167 			if (sArr[i] == '=')

   168 				pad++;

   169 

   170 		int len = ((sLen - sepCnt) * 6 >> 3) - pad;

   171 

   172 		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

   173 

   174 		for (int s = 0, d = 0; d < len;) {

   175 			// Assemble three bytes into an int from four "valid" characters.

   176 			int i = 0;

   177 			for (int j = 0; j < 4; j++) {   // j only increased if a valid char was found.

   178 				int c = IA[sArr[s++]];

   179 				if (c >= 0)

   180 				    i |= c << (18 - j * 6);

   181 				else

   182 					j--;

   183 			}

   184 			// Add the bytes

   185 			dArr[d++] = (byte) (i >> 16);

   186 			if (d < len) {

   187 				dArr[d++]= (byte) (i >> 8);

   188 				if (d < len)

   189 					dArr[d++] = (byte) i;

   190 			}

   191 		}

   192 		return dArr;

   193 	}

   194 

   195 	/** Decodes a BASE64 encoded char array that is known to be resonably well formatted. The method is about twice as

   196 	 * fast as {@link #decode(char[])}. The preconditions are:<br>

   197 	 * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>

   198 	 * + Line separator must be "\r\n", as specified in RFC 2045

   199 	 * + The array must not contain illegal characters within the encoded string<br>

   200 	 * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>

   201 	 * @param sArr The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.

   202 	 * @return The decoded array of bytes. May be of length 0.

   203 	 */

   204 	public final static byte[] decodeFast(char[] sArr)

   205 	{

   206 		// Check special case

   207 		int sLen = sArr.length;

   208 		if (sLen == 0)

   209 			return new byte[0];

   210 

   211 		int sIx = 0, eIx = sLen - 1;    // Start and end index after trimming.

   212 

   213 		// Trim illegal chars from start

   214 		while (sIx < eIx && IA[sArr[sIx]] < 0)

   215 			sIx++;

   216 

   217 		// Trim illegal chars from end

   218 		while (eIx > 0 && IA[sArr[eIx]] < 0)

   219 			eIx--;

   220 

   221 		// get the padding count (=) (0, 1 or 2)

   222 		int pad = sArr[eIx] == '=' ? (sArr[eIx - 1] == '=' ? 2 : 1) : 0;  // Count '=' at end.

   223 		int cCnt = eIx - sIx + 1;   // Content count including possible separators

   224 		int sepCnt = sLen > 76 ? (sArr[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;

   225 

   226 		int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes

   227 		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

   228 

   229 		// Decode all but the last 0 - 2 bytes.

   230 		int d = 0;

   231 		for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {

   232 			// Assemble three bytes into an int from four "valid" characters.

   233 			int i = IA[sArr[sIx++]] << 18 | IA[sArr[sIx++]] << 12 | IA[sArr[sIx++]] << 6 | IA[sArr[sIx++]];

   234 

   235 			// Add the bytes

   236 			dArr[d++] = (byte) (i >> 16);

   237 			dArr[d++] = (byte) (i >> 8);

   238 			dArr[d++] = (byte) i;

   239 

   240 			// If line separator, jump over it.

   241 			if (sepCnt > 0 && ++cc == 19) {

   242 				sIx += 2;

   243 				cc = 0;

   244 			}

   245 		}

   246 

   247 		if (d < len) {

   248 			// Decode last 1-3 bytes (incl '=') into 1-3 bytes

   249 			int i = 0;

   250 			for (int j = 0; sIx <= eIx - pad; j++)

   251 				i |= IA[sArr[sIx++]] << (18 - j * 6);

   252 

   253 			for (int r = 16; d < len; r -= 8)

   254 				dArr[d++] = (byte) (i >> r);

   255 		}

   256 

   257 		return dArr;

   258 	}

   259 

   260 	// ****************************************************************************************

   261 	// *  byte[] version

   262 	// ****************************************************************************************

   263 

   264 	/** Encodes a raw byte array into a BASE64 <code>byte[]</code> representation i accordance with RFC 2045.

   265 	 * @param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.

   266 	 * @param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>

   267 	 * No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a

   268 	 * little faster.

   269 	 * @return A BASE64 encoded array. Never <code>null</code>.

   270 	 */

   271 	public final static byte[] encodeToByte(byte[] sArr, boolean lineSep)

   272 	{

   273 		// Check special case

   274 		int sLen = sArr != null ? sArr.length : 0;

   275 		if (sLen == 0)

   276 			return new byte[0];

   277 

   278 		int eLen = (sLen / 3) * 3;                              // Length of even 24-bits.

   279 		int cCnt = ((sLen - 1) / 3 + 1) << 2;                   // Returned character count

   280 		int dLen = cCnt + (lineSep ? (cCnt - 1) / 76 << 1 : 0); // Length of returned array

   281 		byte[] dArr = new byte[dLen];

   282 

   283 		// Encode even 24-bits

   284 		for (int s = 0, d = 0, cc = 0; s < eLen;) {

   285 			// Copy next three bytes into lower 24 bits of int, paying attension to sign.

   286 			int i = (sArr[s++] & 0xff) << 16 | (sArr[s++] & 0xff) << 8 | (sArr[s++] & 0xff);

   287 

   288 			// Encode the int into four chars

   289 			dArr[d++] = (byte) CA[(i >>> 18) & 0x3f];

   290 			dArr[d++] = (byte) CA[(i >>> 12) & 0x3f];

   291 			dArr[d++] = (byte) CA[(i >>> 6) & 0x3f];

   292 			dArr[d++] = (byte) CA[i & 0x3f];

   293 

   294 			// Add optional line separator

   295 			if (lineSep && ++cc == 19 && d < dLen - 2) {

   296 				dArr[d++] = '\r';

   297 				dArr[d++] = '\n';

   298 				cc = 0;

   299 			}

   300 		}

   301 

   302 		// Pad and encode last bits if source isn't an even 24 bits.

   303 		int left = sLen - eLen; // 0 - 2.

   304 		if (left > 0) {

   305 			// Prepare the int

   306 			int i = ((sArr[eLen] & 0xff) << 10) | (left == 2 ? ((sArr[sLen - 1] & 0xff) << 2) : 0);

   307 

   308 			// Set last four chars

   309 			dArr[dLen - 4] = (byte) CA[i >> 12];

   310 			dArr[dLen - 3] = (byte) CA[(i >>> 6) & 0x3f];

   311 			dArr[dLen - 2] = left == 2 ? (byte) CA[i & 0x3f] : (byte) '=';

   312 			dArr[dLen - 1] = '=';

   313 		}

   314 		return dArr;

   315 	}

   316 

   317 	/** Decodes a BASE64 encoded byte array. All illegal characters will be ignored and can handle both arrays with

   318 	 * and without line separators.

   319 	 * @param sArr The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.

   320 	 * @return The decoded array of bytes. May be of length 0. Will be <code>null</code> if the legal characters

   321 	 * (including '=') isn't divideable by 4. (I.e. definitely corrupted).

   322 	 */

   323 	public final static byte[] decode(byte[] sArr)

   324 	{

   325 		// Check special case

   326 		int sLen = sArr.length;

   327 

   328 		// Count illegal characters (including '\r', '\n') to know what size the returned array will be,

   329 		// so we don't have to reallocate & copy it later.

   330 		int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)

   331 		for (int i = 0; i < sLen; i++)      // If input is "pure" (I.e. no line separators or illegal chars) base64 this loop can be commented out.

   332 			if (IA[sArr[i] & 0xff] < 0)

   333 				sepCnt++;

   334 

   335 		// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.

   336 		if ((sLen - sepCnt) % 4 != 0)

   337 			return null;

   338 

   339 		int pad = 0;

   340 		for (int i = sLen; i > 1 && IA[sArr[--i] & 0xff] <= 0;)

   341 			if (sArr[i] == '=')

   342 				pad++;

   343 

   344 		int len = ((sLen - sepCnt) * 6 >> 3) - pad;

   345 

   346 		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

   347 

   348 		for (int s = 0, d = 0; d < len;) {

   349 			// Assemble three bytes into an int from four "valid" characters.

   350 			int i = 0;

   351 			for (int j = 0; j < 4; j++) {   // j only increased if a valid char was found.

   352 				int c = IA[sArr[s++] & 0xff];

   353 				if (c >= 0)

   354 				    i |= c << (18 - j * 6);

   355 				else

   356 					j--;

   357 			}

   358 

   359 			// Add the bytes

   360 			dArr[d++] = (byte) (i >> 16);

   361 			if (d < len) {

   362 				dArr[d++]= (byte) (i >> 8);

   363 				if (d < len)

   364 					dArr[d++] = (byte) i;

   365 			}

   366 		}

   367 

   368 		return dArr;

   369 	}

   370 

   371 

   372 	/** Decodes a BASE64 encoded byte array that is known to be resonably well formatted. The method is about twice as

   373 	 * fast as {@link #decode(byte[])}. The preconditions are:<br>

   374 	 * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>

   375 	 * + Line separator must be "\r\n", as specified in RFC 2045

   376 	 * + The array must not contain illegal characters within the encoded string<br>

   377 	 * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>

   378 	 * @param sArr The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.

   379 	 * @return The decoded array of bytes. May be of length 0.

   380 	 */

   381 	public final static byte[] decodeFast(byte[] sArr)

   382 	{

   383 		// Check special case

   384 		int sLen = sArr.length;

   385 		if (sLen == 0)

   386 			return new byte[0];

   387 

   388 		int sIx = 0, eIx = sLen - 1;    // Start and end index after trimming.

   389 

   390 		// Trim illegal chars from start

   391 		while (sIx < eIx && IA[sArr[sIx] & 0xff] < 0)

   392 			sIx++;

   393 

   394 		// Trim illegal chars from end

   395 		while (eIx > 0 && IA[sArr[eIx] & 0xff] < 0)

   396 			eIx--;

   397 

   398 		// get the padding count (=) (0, 1 or 2)

   399 		int pad = sArr[eIx] == '=' ? (sArr[eIx - 1] == '=' ? 2 : 1) : 0;  // Count '=' at end.

   400 		int cCnt = eIx - sIx + 1;   // Content count including possible separators

   401 		int sepCnt = sLen > 76 ? (sArr[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;

   402 

   403 		int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes

   404 		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

   405 

   406 		// Decode all but the last 0 - 2 bytes.

   407 		int d = 0;

   408 		for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {

   409 			// Assemble three bytes into an int from four "valid" characters.

   410 			int i = IA[sArr[sIx++]] << 18 | IA[sArr[sIx++]] << 12 | IA[sArr[sIx++]] << 6 | IA[sArr[sIx++]];

   411 

   412 			// Add the bytes

   413 			dArr[d++] = (byte) (i >> 16);

   414 			dArr[d++] = (byte) (i >> 8);

   415 			dArr[d++] = (byte) i;

   416 

   417 			// If line separator, jump over it.

   418 			if (sepCnt > 0 && ++cc == 19) {

   419 				sIx += 2;

   420 				cc = 0;

   421 			}

   422 		}

   423 

   424 		if (d < len) {

   425 			// Decode last 1-3 bytes (incl '=') into 1-3 bytes

   426 			int i = 0;

   427 			for (int j = 0; sIx <= eIx - pad; j++)

   428 				i |= IA[sArr[sIx++]] << (18 - j * 6);

   429 

   430 			for (int r = 16; d < len; r -= 8)

   431 				dArr[d++] = (byte) (i >> r);

   432 		}

   433 

   434 		return dArr;

   435 	}

   436 

   437 	// ****************************************************************************************

   438 	// * String version

   439 	// ****************************************************************************************

   440 

   441 	/** Encodes a raw byte array into a BASE64 <code>String</code> representation i accordance with RFC 2045.

   442 	 * @param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.

   443 	 * @param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>

   444 	 * No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a

   445 	 * little faster.

   446 	 * @return A BASE64 encoded array. Never <code>null</code>.

   447 	 */

   448 	public final static String encodeToString(byte[] sArr, boolean lineSep)

   449 	{

   450 		// Reuse char[] since we can't create a String incrementally anyway and StringBuffer/Builder would be slower.

   451 		return new String(encodeToChar(sArr, lineSep));

   452 	}

   453 

   454 	/** Decodes a BASE64 encoded <code>String</code>. All illegal characters will be ignored and can handle both strings with

   455 	 * and without line separators.<br>

   456 	 * <b>Note!</b> It can be up to about 2x the speed to call <code>decode(str.toCharArray())</code> instead. That

   457 	 * will create a temporary array though. This version will use <code>str.charAt(i)</code> to iterate the string.

   458 	 * @param str The source string. <code>null</code> or length 0 will return an empty array.

   459 	 * @return The decoded array of bytes. May be of length 0. Will be <code>null</code> if the legal characters

   460 	 * (including '=') isn't divideable by 4.  (I.e. definitely corrupted).

   461 	 */

   462 	public final static byte[] decode(String str)

   463 	{

   464 		// Check special case

   465 		int sLen = str != null ? str.length() : 0;

   466 		if (sLen == 0)

   467 			return new byte[0];

   468 

   469 		// Count illegal characters (including '\r', '\n') to know what size the returned array will be,

   470 		// so we don't have to reallocate & copy it later.

   471 		int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)

   472 		for (int i = 0; i < sLen; i++)  // If input is "pure" (I.e. no line separators or illegal chars) base64 this loop can be commented out.

   473 			if (IA[str.charAt(i)] < 0)

   474 				sepCnt++;

   475 

   476 		// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.

   477 		if ((sLen - sepCnt) % 4 != 0)

   478 			return null;

   479 

   480 		// Count '=' at end

   481 		int pad = 0;

   482 		for (int i = sLen; i > 1 && IA[str.charAt(--i)] <= 0;)

   483 			if (str.charAt(i) == '=')

   484 				pad++;

   485 

   486 		int len = ((sLen - sepCnt) * 6 >> 3) - pad;

   487 

   488 		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

   489 

   490 		for (int s = 0, d = 0; d < len;) {

   491 			// Assemble three bytes into an int from four "valid" characters.

   492 			int i = 0;

   493 			for (int j = 0; j < 4; j++) {   // j only increased if a valid char was found.

   494 				int c = IA[str.charAt(s++)];

   495 				if (c >= 0)

   496 				    i |= c << (18 - j * 6);

   497 				else

   498 					j--;

   499 			}

   500 			// Add the bytes

   501 			dArr[d++] = (byte) (i >> 16);

   502 			if (d < len) {

   503 				dArr[d++]= (byte) (i >> 8);

   504 				if (d < len)

   505 					dArr[d++] = (byte) i;

   506 			}

   507 		}

   508 		return dArr;

   509 	}

   510 

   511 	/** Decodes a BASE64 encoded string that is known to be resonably well formatted. The method is about twice as

   512 	 * fast as {@link #decode(String)}. The preconditions are:<br>

   513 	 * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>

   514 	 * + Line separator must be "\r\n", as specified in RFC 2045

   515 	 * + The array must not contain illegal characters within the encoded string<br>

   516 	 * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>

   517 	 * @param s The source string. Length 0 will return an empty array. <code>null</code> will throw an exception.

   518 	 * @return The decoded array of bytes. May be of length 0.

   519 	 */

   520 	public final static byte[] decodeFast(String s)

   521 	{

   522 		// Check special case

   523 		int sLen = s.length();

   524 		if (sLen == 0)

   525 			return new byte[0];

   526 

   527 		int sIx = 0, eIx = sLen - 1;    // Start and end index after trimming.

   528 

   529 		// Trim illegal chars from start

   530 		while (sIx < eIx && IA[s.charAt(sIx) & 0xff] < 0)

   531 			sIx++;

   532 

   533 		// Trim illegal chars from end

   534 		while (eIx > 0 && IA[s.charAt(eIx) & 0xff] < 0)

   535 			eIx--;

   536 

   537 		// get the padding count (=) (0, 1 or 2)

   538 		int pad = s.charAt(eIx) == '=' ? (s.charAt(eIx - 1) == '=' ? 2 : 1) : 0;  // Count '=' at end.

   539 		int cCnt = eIx - sIx + 1;   // Content count including possible separators

   540 		int sepCnt = sLen > 76 ? (s.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;

   541 

   542 		int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes

   543 		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

   544 

   545 		// Decode all but the last 0 - 2 bytes.

   546 		int d = 0;

   547 		for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {

   548 			// Assemble three bytes into an int from four "valid" characters.

   549 			int i = IA[s.charAt(sIx++)] << 18 | IA[s.charAt(sIx++)] << 12 | IA[s.charAt(sIx++)] << 6 | IA[s.charAt(sIx++)];

   550 

   551 			// Add the bytes

   552 			dArr[d++] = (byte) (i >> 16);

   553 			dArr[d++] = (byte) (i >> 8);

   554 			dArr[d++] = (byte) i;

   555 

   556 			// If line separator, jump over it.

   557 			if (sepCnt > 0 && ++cc == 19) {

   558 				sIx += 2;

   559 				cc = 0;

   560 			}

   561 		}

   562 

   563 		if (d < len) {

   564 			// Decode last 1-3 bytes (incl '=') into 1-3 bytes

   565 			int i = 0;

   566 			for (int j = 0; sIx <= eIx - pad; j++)

   567 				i |= IA[s.charAt(sIx++)] << (18 - j * 6);

   568 

   569 			for (int r = 16; d < len; r -= 8)

   570 				dArr[d++] = (byte) (i >> r);

   571 		}

   572 

   573 		return dArr;

   574 	}

   575 }