base64.java

java for RS232

	 */
	public final static byte[] decode(byte[] sArr)
	{
		// Check special case
		int sLen = sArr.length;

		// Count illegal characters (including '\r', '\n') to know what size the returned array will be,
		// so we don't have to reallocate & copy it later.
		int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)
		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.
			if (IA[sArr[i] & 0xff] < 0)
				sepCnt++;

		// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.
		if ((sLen - sepCnt) % 4 != 0)
			return null;

		int pad = 0;
		for (int i = sLen; i > 1 && IA[sArr[--i] & 0xff] <= 0;)
			if (sArr[i] == '=')
				pad++;

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

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

		for (int s = 0, d = 0; d < len;) {
			// Assemble three bytes into an int from four "valid" characters.
			int i = 0;
			for (int j = 0; j < 4; j++) {   // j only increased if a valid char was found.
				int c = IA[sArr[s++] & 0xff];
				if (c >= 0)
				    i |= c << (18 - j * 6);
				else
					j--;
			}

			// Add the bytes
			dArr[d++] = (byte) (i >> 16);
			if (d < len) {
				dArr[d++]= (byte) (i >> 8);
				if (d < len)
					dArr[d++] = (byte) i;
			}
		}

		return dArr;
	}


	/** Decodes a BASE64 encoded byte array that is known to be resonably well formatted. The method is about twice as
	 * fast as {@link #decode(byte[])}. The preconditions are:<br>
	 * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>
	 * + Line separator must be "\r\n", as specified in RFC 2045
	 * + The array must not contain illegal characters within the encoded string<br>
	 * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>
	 * @param sArr The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.
	 * @return The decoded array of bytes. May be of length 0.
	 */
	public final static byte[] decodeFast(byte[] sArr)
	{
		// Check special case
		int sLen = sArr.length;
		if (sLen == 0)
			return new byte[0];

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

		// Trim illegal chars from start
		while (sIx < eIx && IA[sArr[sIx] & 0xff] < 0)
			sIx++;

		// Trim illegal chars from end
		while (eIx > 0 && IA[sArr[eIx] & 0xff] < 0)
			eIx--;

		// get the padding count (=) (0, 1 or 2)
		int pad = sArr[eIx] == '=' ? (sArr[eIx - 1] == '=' ? 2 : 1) : 0;  // Count '=' at end.
		int cCnt = eIx - sIx + 1;   // Content count including possible separators
		int sepCnt = sLen > 76 ? (sArr[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;

		int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

		// Decode all but the last 0 - 2 bytes.
		int d = 0;
		for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
			// Assemble three bytes into an int from four "valid" characters.
			int i = IA[sArr[sIx++]] << 18 | IA[sArr[sIx++]] << 12 | IA[sArr[sIx++]] << 6 | IA[sArr[sIx++]];

			// Add the bytes
			dArr[d++] = (byte) (i >> 16);
			dArr[d++] = (byte) (i >> 8);
			dArr[d++] = (byte) i;

			// If line separator, jump over it.
			if (sepCnt > 0 && ++cc == 19) {
				sIx += 2;
				cc = 0;
			}
		}

		if (d < len) {
			// Decode last 1-3 bytes (incl '=') into 1-3 bytes
			int i = 0;
			for (int j = 0; sIx <= eIx - pad; j++)
				i |= IA[sArr[sIx++]] << (18 - j * 6);

			for (int r = 16; d < len; r -= 8)
				dArr[d++] = (byte) (i >> r);
		}

		return dArr;
	}

	// ****************************************************************************************
	// * String version
	// ****************************************************************************************

	/** Encodes a raw byte array into a BASE64 <code>String</code> representation i accordance with RFC 2045.
	 * @param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.
	 * @param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>
	 * No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a
	 * little faster.
	 * @return A BASE64 encoded array. Never <code>null</code>.
	 */
	public final static String encodeToString(byte[] sArr, boolean lineSep)
	{
		// Reuse char[] since we can't create a String incrementally anyway and StringBuffer/Builder would be slower.
		return new String(encodeToChar(sArr, lineSep));
	}

	/** Decodes a BASE64 encoded <code>String</code>. All illegal characters will be ignored and can handle both strings with
	 * and without line separators.<br>
	 * <b>Note!</b> It can be up to about 2x the speed to call <code>decode(str.toCharArray())</code> instead. That
	 * will create a temporary array though. This version will use <code>str.charAt(i)</code> to iterate the string.
	 * @param str The source string. <code>null</code> or length 0 will return an empty array.
	 * @return The decoded array of bytes. May be of length 0. Will be <code>null</code> if the legal characters
	 * (including '=') isn't divideable by 4.  (I.e. definitely corrupted).
	 */
	public final static byte[] decode(String str)
	{
		// Check special case
		int sLen = str != null ? str.length() : 0;
		if (sLen == 0)
			return new byte[0];

		// Count illegal characters (including '\r', '\n') to know what size the returned array will be,
		// so we don't have to reallocate & copy it later.
		int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)
		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.
			if (IA[str.charAt(i)] < 0)
				sepCnt++;

		// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.
		if ((sLen - sepCnt) % 4 != 0)
			return null;

		// Count '=' at end
		int pad = 0;
		for (int i = sLen; i > 1 && IA[str.charAt(--i)] <= 0;)
			if (str.charAt(i) == '=')
				pad++;

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

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

		for (int s = 0, d = 0; d < len;) {
			// Assemble three bytes into an int from four "valid" characters.
			int i = 0;
			for (int j = 0; j < 4; j++) {   // j only increased if a valid char was found.
				int c = IA[str.charAt(s++)];
				if (c >= 0)
				    i |= c << (18 - j * 6);
				else
					j--;
			}
			// Add the bytes
			dArr[d++] = (byte) (i >> 16);
			if (d < len) {
				dArr[d++]= (byte) (i >> 8);
				if (d < len)
					dArr[d++] = (byte) i;
			}
		}
		return dArr;
	}

	/** Decodes a BASE64 encoded string that is known to be resonably well formatted. The method is about twice as
	 * fast as {@link #decode(String)}. The preconditions are:<br>
	 * + The array must have a line length of 76 chars OR no line separators at all (one line).<br>
	 * + Line separator must be "\r\n", as specified in RFC 2045
	 * + The array must not contain illegal characters within the encoded string<br>
	 * + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>
	 * @param s The source string. Length 0 will return an empty array. <code>null</code> will throw an exception.
	 * @return The decoded array of bytes. May be of length 0.
	 */
	public final static byte[] decodeFast(String s)
	{
		// Check special case
		int sLen = s.length();
		if (sLen == 0)
			return new byte[0];

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

		// Trim illegal chars from start
		while (sIx < eIx && IA[s.charAt(sIx) & 0xff] < 0)
			sIx++;

		// Trim illegal chars from end
		while (eIx > 0 && IA[s.charAt(eIx) & 0xff] < 0)
			eIx--;

		// get the padding count (=) (0, 1 or 2)
		int pad = s.charAt(eIx) == '=' ? (s.charAt(eIx - 1) == '=' ? 2 : 1) : 0;  // Count '=' at end.
		int cCnt = eIx - sIx + 1;   // Content count including possible separators
		int sepCnt = sLen > 76 ? (s.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;

		int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
		byte[] dArr = new byte[len];       // Preallocate byte[] of exact length

		// Decode all but the last 0 - 2 bytes.
		int d = 0;
		for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
			// Assemble three bytes into an int from four "valid" characters.
			int i = IA[s.charAt(sIx++)] << 18 | IA[s.charAt(sIx++)] << 12 | IA[s.charAt(sIx++)] << 6 | IA[s.charAt(sIx++)];

			// Add the bytes
			dArr[d++] = (byte) (i >> 16);
			dArr[d++] = (byte) (i >> 8);
			dArr[d++] = (byte) i;

			// If line separator, jump over it.
			if (sepCnt > 0 && ++cc == 19) {
				sIx += 2;
				cc = 0;
			}
		}

		if (d < len) {
			// Decode last 1-3 bytes (incl '=') into 1-3 bytes
			int i = 0;
			for (int j = 0; sIx <= eIx - pad; j++)
				i |= IA[s.charAt(sIx++)] << (18 - j * 6);

			for (int r = 16; d < len; r -= 8)
				dArr[d++] = (byte) (i >> r);
		}

		return dArr;
	}
}