Base64加密算法源码（java版）

水深无声 2022-08-24 05:18 112阅读 0赞

public class Base64 \{  
    private static final byte\[\] encodingTable = \{  
            (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E',  
            (byte) 'F', (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J',  
            (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O',  
            (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T',  
            (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y',  
            (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd',  
            (byte) 'e', (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i',  
            (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',  
            (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's',  
            (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x',  
            (byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2',  
            (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7',  
            (byte) '8', (byte) '9', (byte) '+', (byte) '/'  
        \};  
    private static final byte\[\] decodingTable;

static \{  
        decodingTable = new byte\[128\];

for (int i = 0; i < 128; i++) \{  
            decodingTable\[i\] = (byte) -1;  
        \}

for (int i = 'A'; i <= 'Z'; i++) \{  
            decodingTable\[i\] = (byte) (i - 'A');  
        \}

for (int i = 'a'; i <= 'z'; i++) \{  
            decodingTable\[i\] = (byte) (i - 'a' + 26);  
        \}

for (int i = '0'; i <= '9'; i++) \{  
            decodingTable\[i\] = (byte) (i - '0' + 52);  
        \}

decodingTable\['+'\] = 62;  
        decodingTable\['/'\] = 63;  
    \}

public static byte\[\] encode(byte\[\] data) \{  
        byte\[\] bytes;

int modulus = data.length % 3;

if (modulus == 0) \{  
            bytes = new byte\[(4 \* data.length) / 3\];  
        \} else \{  
            bytes = new byte\[4 \* ((data.length / 3) + 1)\];  
        \}

int dataLength = (data.length - modulus);  
        int a1;  
        int a2;  
        int a3;

for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) \{  
            a1 = data\[i\] & 0xff;  
            a2 = data\[i + 1\] & 0xff;  
            a3 = data\[i + 2\] & 0xff;

bytes\[j\] = encodingTable\[(a1 >>> 2) & 0x3f\];  
            bytes\[j + 1\] = encodingTable\[((a1 << 4) | (a2 >>> 4)) & 0x3f\];  
            bytes\[j + 2\] = encodingTable\[((a2 << 2) | (a3 >>> 6)) & 0x3f\];  
            bytes\[j + 3\] = encodingTable\[a3 & 0x3f\];  
        \}

int b1;  
        int b2;  
        int b3;  
        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\[data.charAt(i + 3)\];

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\[data.charAt(data.length() - 1)\];

return bytes;  
    \}

private static byte\[\] discardNonBase64Bytes(byte\[\] data) \{  
        byte\[\] temp = new byte\[data.length\];  
        int bytesCopied = 0;

for (int i = 0; i < data.length; i++) \{  
            if (isValidBase64Byte(data\[i\])) \{  
                temp\[bytesCopied++\] = data\[i\];  
            \}  
        \}

byte\[\] newData = new byte\[bytesCopied\];

System.arraycopy(temp, 0, newData, 0, bytesCopied);

return newData;  
    \}

private static String discardNonBase64Chars(String data) \{  
        StringBuffer sb = new StringBuffer();

int length = data.length();

for (int i = 0; i < length; i++) \{  
            if (isValidBase64Byte((byte) (data.charAt(i)))) \{  
                sb.append(data.charAt(i));  
            \}  
        \}

return sb.toString();  
    \}

private static boolean isValidBase64Byte(byte b) \{  
        if (b == '=') \{  
            return true;  
        \} else if ((b < 0) || (b >= 128)) \{  
            return false;  
        \} else if (decodingTable\[b\] == -1) \{  
            return false;  
        \}

return true;  
    \}

public static void main(String\[\] args) \{  
        String data = "1";  
        byte\[\] result = Base64.encode(data.getBytes());  
        System.out.println(data);  
        System.out.println(new String(result));  
        System.out.println(new String(Base64.decode(new String(result))));  
    \}  
\}

转自：[http://blog.csdn.net/zyg158/archive/2007/06/26/1667531.aspx][http_blog.csdn.net_zyg158_archive_2007_06_26_1667531.aspx]

[http_blog.csdn.net_zyg158_archive_2007_06_26_1667531.aspx]: http://blog.csdn.net/zyg158/archive/2007/06/26/1667531.aspx