base64.java

封装了SQL、Socket、WAP、MIME等功能的通用组件

package org.lazybug.util;

public class Base64
{

    private static char baseChar[] = {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
        'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
        'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
        'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
        'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
        '8', '9', '+', '/'
    };
    private static byte position[] = {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, 62, -1, 63, -1, 63, 52, 53,
        54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
        -1, 0, -1, -1, -1, 0, 1, 2, 3, 4,
        5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
        15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
        25, -1, -1, -1, -1, -1, -1, 26, 27, 28,
        29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
        39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
        49, 50, 51, -1, -1, -1, -1, -1
    };

    private Base64()
    {
    }

    public static String encode(byte b[])
    {
        int code = 0;
        StringBuffer sb = new StringBuffer((b.length - 1) / 3 << 6);
        for(int i = 0; i < b.length; i++)
        {
            code |= b[i] << 16 - (i % 3) * 8 & 255 << 16 - (i % 3) * 8;
            if(i % 3 == 2 || i == b.length - 1)
            {
                sb.append(baseChar[(code & 0xfc0000) >>> 18]);
                sb.append(baseChar[(code & 0x3f000) >>> 12]);
                sb.append(baseChar[(code & 0xfc0) >>> 6]);
                sb.append(baseChar[code & 0x3f]);
                code = 0;
            }
        }

        if(b.length % 3 > 0)
            sb.setCharAt(sb.length() - 1, '=');
        if(b.length % 3 == 1)
            sb.setCharAt(sb.length() - 2, '=');
        return sb.toString();
    }

    public static String decodeString(String code)
    {
        if( code.length() == 0 ) return "";
        byte buf[] = decode(code);

        for( int i = 0; i < buf.length; i++ )
        {
            if( buf[i] < 0 ) return code;
        }
        if( buf.length == 1 && buf[0] == 0x00 ) return "";
        String s = new String(buf);
        return Tools.decodeUnicode(s, '%');
    }

    public static byte[] decode(String code)
    {
        if(code == null)
            return null;
        int len = code.length();
        if(len % 4 != 0)
        {
            return code.getBytes(); // new IllegalArgumentException("Base64 string length must be 4*n");
        }
        if(code.length() == 0)
            return new byte[0];
        int pad = 0;
        if(code.charAt(len - 1) == '=')
            pad++;
        if(code.charAt(len - 2) == '=')
            pad++;
        int retLen = (len / 4) * 3 - pad;
        byte ret[] = new byte[retLen];
        for(int i = 0; i < len; i += 4)
        {
            int j = (i / 4) * 3;
            char ch1 = code.charAt(i);
            char ch2 = code.charAt(i + 1);
            char ch3 = code.charAt(i + 2);
            char ch4 = code.charAt(i + 3);
            int tmp = position[ch1] << 18 | position[ch2] << 12 | position[ch3] << 6 | position[ch4];
            ret[j] = (byte)((tmp & 0xff0000) >> 16);
            if(i < len - 4)
            {
                ret[j + 1] = (byte)((tmp & 0xff00) >> 8);
                ret[j + 2] = (byte)(tmp & 0xff);
                continue;
            }
            if(j + 1 < retLen)
                ret[j + 1] = (byte)((tmp & 0xff00) >> 8);
            if(j + 2 < retLen)
                ret[j + 2] = (byte)(tmp & 0xff);
        }

        return ret;
    }

    public static void main(String[] args)
    {
        Tools.printb(decodeString("AA==").getBytes());
        //System.out.println(Base64.encode("http://wap.monternet.com".getBytes()));
        //System.out.println(Base64.decodeString("aHR0cCUzQS8vd2FwLm1vbnRlcm5ldC5jb20="));
    }
}