Base64 encoding/decoding. : Base64 « Development Class « Java

1. Java
2. Development Class
3. Base64

Base64 encoding/decoding.

      
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 * However, if you add GPL Version 2 code and therefore, elected the GPL
 * Version 2 license, then the option applies only if the new code is
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 */

/** This class provides Base64 encoding/decoding.
 */
public class Base64
{
    private Base64()
    {
        //Avoid instantiation of this class
    }
    
    /** Encodes datas using base64 encoding.
     * @param abyte0 data for encoding
     * @return encoded string
     */
    static String encode(final byte abyte0[])
    {
        final StringBuffer stringbuffer = new StringBuffer();
        for(int i = 0; i < abyte0.length; i += 3)
            stringbuffer.append(encodeBlock(abyte0, i));
        
        return stringbuffer.toString();
    }
    
    private static char[] encodeBlock(final byte abyte0[], final int i)
    {
        int j = 0;
        final int k = abyte0.length - i - 1;
        final int l = k < 2 ? k : 2;
        for(int i1 = 0; i1 <= l; i1++)
        {
            final byte byte0 = abyte0[i + i1];
            final int j1 = byte0 >= 0 ? ((int) (byte0)) : byte0 + 256;
            j += j1 << 8 * (2 - i1);
        }
        
        char ac[] = new char[4];
        for(int k1 = 0; k1 < 4; k1++)
        {
            final int l1 = j >>> 6 * (3 - k1) & 0x3f;
            ac[k1] = getChar(l1);
        }
        
        if(k < 1)
            ac[2] = '=';
        if(k < 2)
            ac[3] = '=';
        return ac;
    }
    
    private static char getChar(final int i)
    {
        if(i >= 0 && i <= 25)
            return (char)(65 + i);
        if(i >= 26 && i <= 51)
            return (char)(97 + (i - 26));
        if(i >= 52 && i <= 61)
            return (char)(48 + (i - 52));
        if(i == 62)
            return '+';
        return i != 63 ? '?' : '/';
    }
    
    /** Decode string using Base64 encoding.
     * @param s string for decoding
     * @return decoded data
     */
    static byte[] decode(final String s)
    {
        if (s.length() == 0) return new byte[0];
        int i = 0;
        for(int j = s.length() - 1; j > 0 && s.charAt(j) == '='; j--)
            i++;
        
        final int k = (s.length() * 6) / 8 - i;
        byte abyte0[] = new byte[k];
        int l = 0;
        for(int i1 = 0; i1 < s.length(); i1 += 4)
        {
            final int j1 = (getValue(s.charAt(i1)) << 18) + (getValue(s.charAt(i1 + 1)) << 12) + (getValue(s.charAt(i1 + 2)) << 6) + getValue(s.charAt(i1 + 3));
            for(int k1 = 0; k1 < 3 && l + k1 < abyte0.length; k1++)
                abyte0[l + k1] = (byte)(j1 >> 8 * (2 - k1) & 0xff);
            
            l += 3;
        }
        return abyte0;
    }
    
    private static int getValue(final char c)
    {
        if(c >= 'A' && c <= 'Z')
            return c - 65;
        if(c >= 'a' && c <= 'z')
            return (c - 97) + 26;
        if(c >= '0' && c <= '9')
            return (c - 48) + 52;
        if(c == '+')
            return 62;
        if(c == '/')
            return 63;
        return c != '=' ? -1 : 0;
    }
}

   
    
    
    
    
    
  

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