ADD_BYTE
ADD_BYTE(src[spos]);
ADD_BYTE(0xc0 | (src[spos]>>6));
ADD_BYTE(0x80 | (src[spos] & 0x3f));
ADD_BYTE(0xf0 | (c>>18));
ADD_BYTE(0x80 | ((c>>12) & 0x3f));
ADD_BYTE(0x80 | ((c>>6) & 0x3f));
ADD_BYTE(0x80 | (c & 0x3f));
ADD_BYTE(0xe0 | src[spos]>>12);
ADD_BYTE(0x80 | ((src[spos]>>6) & 0x3f));
ADD_BYTE(0x80 | (src[spos] & 0x3f));
ADD_BYTE(*mtod(m, u_char *));
ADD_BYTE(~fcs0 & 0xff);
ADD_BYTE(~fcs0 >> 8);