H3C-cams DES加密算法研究总结 (10)

int d1; int d2;

switch (modulus) {

case 0: /* nothing left to do */ break; case 1:

d1 = data[data.length - 1] & 0xff; b1 = (d1 >>> 2) & 0x3f; b2 = (d1 << 4) & 0x3f;

bytes[bytes.length - 4] = encodingTable[b1]; bytes[bytes.length - 3] = encodingTable[b2]; bytes[bytes.length - 2] = (byte) '='; bytes[bytes.length - 1] = (byte) '='; break; case 2:

d1 = data[data.length - 2] & 0xff; d2 = data[data.length - 1] & 0xff; b1 = (d1 >>> 2) & 0x3f;

b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f; b3 = (d2 << 2) & 0x3f;

bytes[bytes.length - 4] = encodingTable[b1]; bytes[bytes.length - 3] = encodingTable[b2];

bytes[bytes.length - 2] = encodingTable[b3]; bytes[bytes.length - 1] = (byte) '='; break; }

return bytes; }

public static byte[] decode(byte[] data) { byte[] bytes; byte b1; byte b2; byte b3; byte b4;

data = discardNonBase64Bytes(data); if (data[data.length - 2] == '=') {

bytes = new byte[(((data.length / 4) - 1) * 3) + 1]; } else if (data[data.length - 1] == '=') {

bytes = new byte[(((data.length / 4) - 1) * 3) + 2]; } else {

bytes = new byte[((data.length / 4) * 3)]; }

for (int i = 0, j = 0; i < (data.length - 4); i += 4, j += 3) { b1 = decodingTable[data[i]];

b2 = decodingTable[data[i + 1]]; b3 = decodingTable[data[i + 2]]; b4 = decodingTable[data[i + 3]]; bytes[j] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2)); bytes[j + 2] = (byte) ((b3 << 6) | b4); }

if (data[data.length - 2] == '=') {

b1 = decodingTable[data[data.length - 4]]; b2 = decodingTable[data[data.length - 3]];

bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4)); } else if (data[data.length - 1] == '=') {

b1 = decodingTable[data[data.length - 4]]; b2 = decodingTable[data[data.length - 3]]; b3 = decodingTable[data[data.length - 2]];

bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2)); } else {

b1 = decodingTable[data[data.length - 4]]; b2 = decodingTable[data[data.length - 3]]; b3 = decodingTable[data[data.length - 2]]; b4 = decodingTable[data[data.length - 1]];

bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2)); bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4); }

return bytes; }

public static byte[] decode(String data) { byte[] bytes; byte b1; byte b2; byte b3; byte b4;

data = discardNonBase64Chars(data); if (data.charAt(data.length() - 2) == '=') {

bytes = new byte[(((data.length() / 4) - 1) * 3) + 1]; } else if (data.charAt(data.length() - 1) == '=') { bytes = new byte[(((data.length() / 4) - 1) * 3) + 2]; } else {

bytes = new byte[((data.length() / 4) * 3)]; }

for (int i = 0, j = 0; i < (data.length() - 4); i += 4, j += 3) { b1 = decodingTable[data.charAt(i)];

b2 = decodingTable[data.charAt(i + 1)]; b3 = decodingTable[data.charAt(i + 2)]; b4 = decodingTable[data.charAt(i + 3)]; bytes[j] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2)); bytes[j + 2] = (byte) ((b3 << 6) | b4); }

if (data.charAt(data.length() - 2) == '=') {

b1 = decodingTable[data.charAt(data.length() - 4)]; b2 = decodingTable[data.charAt(data.length() - 3)]; bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4)); } else if (data.charAt(data.length() - 1) == '=') {

b1 = decodingTable[data.charAt(data.length() - 4)]; b2 = decodingTable[data.charAt(data.length() - 3)]; b3 = decodingTable[data.charAt(data.length() - 2)]; bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2)); } else {

b1 = decodingTable[data.charAt(data.length() - 4)]; b2 = decodingTable[data.charAt(data.length() - 3)]; b3 = decodingTable[data.charAt(data.length() - 2)]; b4 = decodingTable[data.charAt(data.length() - 1)];