UTF-8 Decoder & Encoder

有的手機不支持utf8. 需要時直接copy。

UTF-8 Decoder:

String decode(byte[] b,int start,int len) {
    StringBuffer s = new StringBuffer();
    int end = start + len;
    for (int i = start; i < end; ) {        

        byte b = b[i++];        

        if ( (b >> 7) == 0)
            s.append( (char) b);
        else if ( (b >> 5) == (byte) 0xfe)
            s.append((char)(((b & 0x1f)<<6)  | (b[i++] & 0x3f)));

        else if ( (b >> 4) == (byte) 0xfe)
            s.append((char)(((b & 0xf)<<12) | ( (b[i++] & 0x3f) << 6) | (b[i++] &0x3f)));    

    }

    return new String(s);

}


UTF-8 Encoder:
byte[] utf8_encode(String s) {
    int len = 0;
    int strlen = s.length();
    for (int i = 0; i < strlen; i++) {

         char c = s.charAt(i);

         if (c < 128) len++;

         else if (c < 2048) len += 2;

         else len += 3;    

    }    

    byte[] b = new byte[len];

     len = 0;    

    for (int i = 0; i < strlen; i++) {

         char c = s.charAt(i);

         if (c < 128)

           b[len++] = (byte) c;

         else if (c < 2048) {

           b[len++]=(byte)((c>>6)|192);
          b[len++]=(byte)((c&63)|128);
        }
        else {
          b[len++]=(byte)((c>>12)|224);
          b[len++]=(byte)((c>>12)|224);
          b[len++]=(byte)((c&63) |128);
        }
    }
    return b;
}