GNIDA.mediana.parse_prefixes C# (CSharp) Method

        static UInt32 parse_prefixes(long offset, ref INSTRUCTION instr, INTERNAL_DATA idata, byte ext_table_index, byte ext_pref_index, ref DISASM_INOUT_PARAMS param)
        {
            byte pref_code;
            byte rex_found;
            byte pref_id;
            byte pref_index;
            UInt32 res;
            UInt32 tmp;
            OPCODE_DESCRIPTOR ptr;

            res = 0;
            rex_found = 0;

            while(true)
            {

            //pref_code = *offset;
            pref_code = assembly.Image.ReadBytes(offset, 1)[0];

            if (res > MAX_INSTRUCTION_LEN)
            {
            idata.severe_err = ERRS.ERR_TOO_LONG;//error: instruction too long.
            break;
            }

            ptr = tables[IDX_1BYTE].opcodes[pref_code];
            if ( !( ((ptr.groups & GRP_PREFIX)!=0) ||
                (param.mode == DISMODE.DISASSEMBLE_MODE_64 && (pref_code >= 0x40) && (pref_code <= 0x4F) && (rex_found == 0))))
            {
            break;
            }
            else
            {
            if (rex_found!=0)
            {
                idata.severe_err = ERRS.ERR_REX_NOOPCD;//error: an opcode should follow after rex.
                break;
            }

            if ((rex_found != 0) && (param.mode == DISMODE.DISASSEMBLE_MODE_64))
            {
                if ( (pref_code >= 0x40) && (pref_code <= 0x4F) )
                {
                    idata.prefixes[PREF_REX_INDEX] = PREF_REX_ID;
                    instr.rex = pref_code;
                    rex_found = 1;

                    res++;
                    offset++;
                    continue;
                }
            }

            tmp = tq_handlers[ptr.ops[0].type](0, 0, ref instr, 0, new OPERAND_SIZE(), new INTERNAL_DATA(), param.mode);
            pref_index = (byte)(tmp >> 8);
            pref_id = (byte)tmp;// &0xFF;
            if (idata.prefixes[pref_index] != 0xFF)
            {
                add_sf_prefix(idata.prefixes, pref_index, ref instr, ref param);
            }
            idata.prefixes[pref_index] = pref_id;

            //Used later for prefix table switch.
            if (ptr.id == ID_66 || ptr.id == ID_REPZ || ptr.id == ID_REPNZ)
            {
                ext_table_index =(byte)(ptr.props);
                ext_pref_index = pref_index;
            }

            res++;
            offset++;
            }
            }

            return res;
        }