文件编码格式转换工具

        //文件转码
        QByteArray encoded_data = in_file.readAll();
        QTextStream in(&encoded_data);
        in.setAutoDetectUnicode(false);
        in.setCodec(src_codec);
        QString decoded_str = in.readAll();
        QTextStream out(&out_file);
        out.setCodec(dest_codec);
        out << decoded_str;

        fill_result(idx, true);
//        fill_row_count(idx, row_count);

        //备份文件
        if(ui->back_src_ckb->isChecked())
        {
            QString back_file = QString("%1_bak").arg(file_info.fileName());
            in_file.copy(back_file);
        }
        in_file.close();
        in_file.remove();
        out_file.close();
        out_file.rename(file_name);
    }