标签：return encodedIndex ++ Base64 int b1 byte
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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; } }
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标签：return,encodedIndex,++,Base64,int,b1,byte 来源： https://www.cnblogs.com/chinaifae/p/10400638.html
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