text: package wang.imchao.plugin.alipay;
  
  public final class Base64 {
  
  	private static final int BASELENGTH = 128;
  	private static final int LOOKUPLENGTH = 64;
  	private static final int TWENTYFOURBITGROUP = 24;
  	private static final int EIGHTBIT = 8;
  	private static final int SIXTEENBIT = 16;
  	private static final int FOURBYTE = 4;
  	private static final int SIGN = -128;
  	private static char PAD = '=';
  	private static byte[] base64Alphabet = new byte[BASELENGTH];
  	private static char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];
  
  	static {
  		for (int i = 0; i < BASELENGTH; ++i) {
  			base64Alphabet[i] = -1;
  		}
  		for (int i = 'Z'; i >= 'A'; i--) {
  			base64Alphabet[i] = (byte) (i - 'A');
  		}
  		for (int i = 'z'; i >= 'a'; i--) {
  			base64Alphabet[i] = (byte) (i - 'a' + 26);
  		}
  
  		for (int i = '9'; i >= '0'; i--) {
  			base64Alphabet[i] = (byte) (i - '0' + 52);
  		}
  
  		base64Alphabet['+'] = 62;
  		base64Alphabet['/'] = 63;
  
  		for (int i = 0; i <= 25; i++) {
  			lookUpBase64Alphabet[i] = (char) ('A' + i);
  		}
  
  		for (int i = 26, j = 0; i <= 51; i++, j++) {
  			lookUpBase64Alphabet[i] = (char) ('a' + j);
  		}
  
  		for (int i = 52, j = 0; i <= 61; i++, j++) {
  			lookUpBase64Alphabet[i] = (char) ('0' + j);
  		}
  		lookUpBase64Alphabet[62] = (char) '+';
  		lookUpBase64Alphabet[63] = (char) '/';
  
  	}
  
  	private static boolean isWhiteSpace(char octect) {
  		return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
  	}
  
  	private static boolean isPad(char octect) {
  		return (octect == PAD);
  	}
  
  	private static boolean isData(char octect) {
  		return (octect < BASELENGTH && base64Alphabet[octect] != -1);
  	}
  
  	/**
  	 * Encodes hex octects into Base64
  	 * 
  	 * @param binaryData
  	 *            Array containing binaryData
  	 * @return Encoded Base64 array
  	 */
  	public static String encode(byte[] binaryData) {
  
  		if (binaryData == null) {
  			return null;
  		}
  
  		int lengthDataBits = binaryData.length * EIGHTBIT;
  		if (lengthDataBits == 0) {
  			return "";
  		}
  
  		int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
  		int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
  		int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1
  				: numberTriplets;
  		char encodedData[] = null;
  
  		encodedData = new char[numberQuartet * 4];
  
  		byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;
  
  		int encodedIndex = 0;
  		int dataIndex = 0;
  
  		for (int i = 0; i < numberTriplets; i++) {
  			b1 = binaryData[dataIndex++];
  			b2 = binaryData[dataIndex++];
  			b3 = binaryData[dataIndex++];
  
  			l = (byte) (b2 & 0x0f);
  			k = (byte) (b1 & 0x03);
  
  			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2)
  					: (byte) ((b1) >> 2 ^ 0xc0);
  			byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4)
  					: (byte) ((b2) >> 4 ^ 0xf0);
  			byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6)
  					: (byte) ((b3) >> 6 ^ 0xfc);
  
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
  		}
  
  		// form integral number of 6-bit groups
  		if (fewerThan24bits == EIGHTBIT) {
  			b1 = binaryData[dataIndex];
  			k = (byte) (b1 & 0x03);
  			
  			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2)
  					: (byte) ((b1) >> 2 ^ 0xc0);
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
  			encodedData[encodedIndex++] = PAD;
  			encodedData[encodedIndex++] = PAD;
  		} else if (fewerThan24bits == SIXTEENBIT) {
  			b1 = binaryData[dataIndex];
  			b2 = binaryData[dataIndex + 1];
  			l = (byte) (b2 & 0x0f);
  			k = (byte) (b1 & 0x03);
  
  			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2)
  					: (byte) ((b1) >> 2 ^ 0xc0);
  			byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4)
  					: (byte) ((b2) >> 4 ^ 0xf0);
  
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
  			encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
  			encodedData[encodedIndex++] = PAD;
  		}
  
  		return new String(encodedData);
  	}
  
  	/**
  	 * Decodes Base64 data into octects
  	 * 
  	 * @param encoded
  	 *            string containing Base64 data
  	 * @return Array containind decoded data.
  	 */
  	public static byte[] decode(String encoded) {
  
  		if (encoded == null) {
  			return null;
  		}
  
  		char[] base64Data = encoded.toCharArray();
  		// remove white spaces
  		int len = removeWhiteSpace(base64Data);
  
  		if (len % FOURBYTE != 0) {
  			return null;// should be divisible by four
  		}
  
  		int numberQuadruple = (len / FOURBYTE);
  
  		if (numberQuadruple == 0) {
  			return new byte[0];
  		}
  
  		byte decodedData[] = null;
  		byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
  		char d1 = 0, d2 = 0, d3 = 0, d4 = 0;
  
  		int i = 0;
  		int encodedIndex = 0;
  		int dataIndex = 0;
  		decodedData = new byte[(numberQuadruple) * 3];
  
  		for (; i < numberQuadruple - 1; i++) {
  
  			if (!isData((d1 = base64Data[dataIndex++]))
  					|| !isData((d2 = base64Data[dataIndex++]))
  					|| !isData((d3 = base64Data[dataIndex++]))
  					|| !isData((d4 = base64Data[dataIndex++]))) {
  				return null;
  			}// if found "no data" just return null
  
  			b1 = base64Alphabet[d1];
  			b2 = base64Alphabet[d2];
  			b3 = base64Alphabet[d3];
  			b4 = base64Alphabet[d4];
  
  			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
  			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
  			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
  		}
  
  		if (!isData((d1 = base64Data[dataIndex++]))
  				|| !isData((d2 = base64Data[dataIndex++]))) {
  			return null;// if found "no data" just return null
  		}
  
  		b1 = base64Alphabet[d1];
  		b2 = base64Alphabet[d2];
  
  		d3 = base64Data[dataIndex++];
  		d4 = base64Data[dataIndex++];
  		if (!isData((d3)) || !isData((d4))) {// Check if they are PAD characters
  			if (isPad(d3) && isPad(d4)) {
  				if ((b2 & 0xf) != 0)// last 4 bits should be zero
  				{
  					return null;
  				}
  				byte[] tmp = new byte[i * 3 + 1];
  				System.arraycopy(decodedData, 0, tmp, 0, i * 3);
  				tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
  				return tmp;
  			} else if (!isPad(d3) && isPad(d4)) {
  				b3 = base64Alphabet[d3];
  				if ((b3 & 0x3) != 0)// last 2 bits should be zero
  				{
  					return null;
  				}
  				byte[] tmp = new byte[i * 3 + 2];
  				System.arraycopy(decodedData, 0, tmp, 0, i * 3);
  				tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
  				tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
  				return tmp;
  			} else {
  				return null;
  			}
  		} else { // No PAD e.g 3cQl
  			b3 = base64Alphabet[d3];
  			b4 = base64Alphabet[d4];
  			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
  			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
  			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
  
  		}
  
  		return decodedData;
  	}
  
  	/**
  	 * remove WhiteSpace from MIME containing encoded Base64 data.
  	 * 
  	 * @param data
  	 *            the byte array of base64 data (with WS)
  	 * @return the new length
  	 */
  	private static int removeWhiteSpace(char[] data) {
  		if (data == null) {
  			return 0;
  		}
  
  		// count characters that's not whitespace
  		int newSize = 0;
  		int len = data.length;
  		for (int i = 0; i < len; i++) {
  			if (!isWhiteSpace(data[i])) {
  				data[newSize++] = data[i];
  			}
  		}
  		return newSize;
  	}
  }
  