bsp;         //shift the 6 bit bytes into a single 4 octet word
                                int res=(unenc[0]<<18)+(unenc[1]<<12)+(unenc[2]<<6)+unenc[3];
                                byte c;
                                int k=16;
                                //shift each octet down to read it as char and add to StringBuffer
                                while(k>=0)
                                {
                                        c=(byte)(res>>k);
                                        if ( c>0 )
                                        sb.append((char)c);
                                        k-=8;
                                }
                                //reset j and the unencode buffer
                                j=0;
                                unenc[0]=0;unenc[1]=0;unenc[2]=0;unenc[3]=0;
                        }
                }
                return sb.toString();
        }
        
        /** encode plaintext data to a base 64 string
          * @param plain the text to convert. If plain is longer than 76 characters this method
          *             returns null (see RFC2045).
          * @return the encoded text (or null if string was longer than 76 chars).
        */
        public static String encode(String plain)
        {
                if(plain.length()>76)
                return null;
                int maxturns;
                StringBuffer sb=new StringBuffer();
                //the encode buffer
                byte[] enc=new byte[3];
                boolean end=false;
                for(int i=0,j=0;!end;i++)
                {
                        char _ch=plain.charAt(i);
                        if(i==plain.length()-1)
                        end=true;
                        enc[j++]=(byte)plain.charAt(i);
                        if(j==3 || end)
                        {
                                int res;
                                //this is a bit inefficient at the end point
                                //worth it for the small decrease in code size?
                                res=(enc[0]<<16)+(enc[1]<<8)+enc[2];
                                int b;
                                int lowestbit=18-(j*6);
                                for(int toshift=18;toshift>=lowestbit;toshift-=6)
                                {
                                        b=res>>>toshift;
                                        b&=63;
                                        if(b>=0&&b<26)
                                        sb.append((char)(b+65));
                                        if(b>=26&&b<52)
                                        sb.append((char)(b+71));
                            

上一页  [1] [2] [3] 下一页