Base64（3）

public final class Base64 {

static private final int     BASELENGTH           = 128;

static private final int     LOOKUPLENGTH         = 64;

static private final int     TWENTYFOURBITGROUP   = 24;

static private final int     EIGHTBIT             = 8;

static private final int     SIXTEENBIT           = 16;

static private final int     FOURBYTE             = 4;

static private final int     SIGN                 = -128;

static private final char    PAD                  = '=';

static private final boolean fDebug               = false;

static final private byte[]  base64Alphabet       = new byte[BASELENGTH];

static final private 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;

if (fDebug) {

System.out.println("number of triplets = " + numberTriplets);

}

for (int i = 0; i < numberTriplets; i++) {

b1 = binaryData[dataIndex++];

b2 = binaryData[dataIndex++];

b3 = binaryData[dataIndex++];

if (fDebug) {

System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);

}

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);

if (fDebug) {

System.out.println("val2 = " + val2);

System.out.println("k4   = " + (k << 4));

System.out.println("vak  = " + (val2 | (k << 4)));

}

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);

if (fDebug) {

System.out.println("b1=" + b1);

System.out.println("b1<<2 = " + (b1 >> 2));

}

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;

}

}